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Grippa, Juliana Malvestio. „Reatividade das espécies heme-Fe metmioglobina e oximioglobina frente ao estado singlete e triplete excitado da riboflavina“. Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/75/75133/tde-02072014-144920/.
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O pigmento da carne fresca, oximioglobina, e a sua forma oxidada, metmioglobina, podem ser ambos oxidados pela riboflavina quando expostos à radiação luminosa, afetando sua estabilidade redox da carne do ponto de vista nutricional e sensorial. A reação da MbFe(II)O2 e da MbFe(III) com o estado tripleto da riboflavina, 3Rib, envolve uma eficiente transferência de elétrons entre o anel isoaloxazina da riboflavina e a cadeia polipeptídica da proteína, o que leva à formação de cross-link e/ou fragmentação, como demostrado por SDS-PAGE e Western-blot. A constante global de velocidade para a oxidação da MbFe(II)O2 pela 3Rib é (3,0 ± 0,5 ) 109 L·mol-1·s-1 e de (3,1 ± 0,4) 109 L·mol-1·s-1 para a oxidação da MbFe(III) pelo estado tripleto da riboflavina. Cálculos termodinâmicos demonstram ainda que há formação de um complexo exotérmico com estequiometria 1:1 favorecido a temperaturas mais baixas com Ka = (1.2 ± 0.2) 104 mol·L-1 a 25 °C e ΔHo = -112 ± 22 kJ·mol-1 e ΔSo = -296 ± 75 J·mol-1·K-1. Conclui-se que para carne, a riboflavina é um fotossensibilizador para oxidação de proteína e não para a descoloração.The fresh meat pigment oxymyoglobin, MbFe(II)O2, and its oxidized form metmyoglobin, MbFe(III), are both oxidized by riboflavin as photosensitizer. The reaction of MbFe(II)O2 and MbFe(III) with triplet-state riboflavin, 3Rib, involves the pigment protein, which is oxidatively cleaved or dimerized as shown by SDS-PAGE and Western-blotting, while the heme iron center is not oxidized. The over-all rate constant for oxidation of MbFe(II)O2 by 3Rib is (3.0 ± 0.5) 109 L·mol-1·s-1 and (3.1 ± 0.4) 109 L·mol-1·s-1 for MbFe(III) in aqueous 0.20 mol·L-1 NaCl phosphate buffer of pH 7.4 at 25 °C as determined by transient absorption laser flash photolysis. The high rates are rationalized by ground state hydrophobic interactions as detected as static quenching of fluorescence from singlet-excited state riboflavin by myoglobins using single photon counting time resolved fluorescence spectroscopy and a Stern-Volmer approach. Binding of riboflavin to MbFe(III) has Ka = (1.2 ± 0.2) 104 mol·L-1 at 25 °C with ΔHo = -112 ± 22 kJ·mol-1 and ΔSo = -296 ± 75 J·mol-1·K-1. For meat, riboflavin is concluded to be a photosensitizer for protein oxidation but not for discoloration.
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Subbotina, Beztsinna Nataliia. „Riboflavin-based amphiphiles for tumour-targeted nanosystems“. Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0254/document.
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La riboflavine (RF) est une vitamine essentielle pour la croissance et le développement cellulaire. Elle possède des propriétés physico-chimiques intéressantes et est internalisée dans les cellules par des transporteurs spécifiques. Le premier objectif de ce projet était de synthétiser des dérivés amphiphiles de la RF (RFA) et d'étudier leurs capacités d'auto-assemblages. Le second objectif était d'insérer les RFA dans des liposomes et d'évaluer leur efficacité de ciblage tumoral in vitro et in vivo. La préparation des différents RFA repose sur l'ajout d'un lipide en différentes positions de la RF. L’un d'eux, de type phospholipide (RfdiC14) a été capable de former des objets tridimensionnels de taille μm constitués de lamelles multicouches dont l’architecture et la dynamique sont très différentes de celles des phospholipides classiques. L’insertion de RfdiC14 dans des liposomes est efficace et n’influence pas leurs propriétés physico-chimiques. Les liposomes fonctionnalisés ont montré une internalisation cellulaire spécifique dans les lignées A431, PC3 et HUVECs. Afin de tester l’efficacité du ciblage tumoral in vivo, un analogue de RfdiC14 portant un espaceur PEG a été préparé puis inséré dans des liposomes péguylés. Grâce à un marquage adéquat (ICG et DiR), leur accumulation tumorale a été suivie par imagerie photoacoustique dans un modèle A431 et leur biodistribution évaluée par imagerie μCT/FMT dans un modèle PC3. Les résultats montrent une légère amélioration de l’accumulation tumorale dans les xénogreffes A431 et une augmentation du ciblage vasculaire dans le modèle tumoral PC3. La biodistribution globale des liposomes marqués est comparable à celle des contrôlesRiboflavin (RF) is an essential vitamin for cell growth and development. It possesses interesting physicochemical properties and is internalized by the cells through specific transporters. The first aim of this study was to prepare amphiphile derivatives of RF (RFA) and study their auto-assembly. The second aim was to insert RFA into established drug delivery systems and test their tumour-targeting potential in vitro and in vivo. RFA were prepared by the molecule functionalization with lipid moieties in different positions. One of them, a phospholipid-like derivative (RfdiC14) was able to self-assembly in aqueous solutions into μm-sized 3D objects constituted from slightly curved multilayer lamellas. The bilayer architecture and dynamics were very different from ordinary phospholipids. In contrast, the insertion of small amount of RfdiC14 in a liposome did not influence membrane dynamics and physicochemical characteristics. RfdiC14-functionalised liposomes displayed high and specific uptake in vitro in A431, PC3 cells and HUVECs. The efficiency of RF targeting was also tested in vivo. For that purpose, liposome composition was optimized and a new RF amphiphile with a PEG spacer between RF and lipid was prepared. The tumour accumulation of the liposomes labelled with ICG was studied by photoacoustic imaging in A431 tumour model. The biodistribution of DiR labelled liposomes was accessed by combined μCT/FMT imaging in PC3 tumour model. The results show slight improvement of the tumour accumulation in A431 xenographts and the enhancement of vascular targeting in PC3 tumour model. The overall biodistribution of the RF-targeted liposomes was comparable to control
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Machado, Daisy 1981. „Modulação da agressividade do melanoma por flavinas“. [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314042.
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Orientadores: Carmen Verissima Ferreira Halder, Silvia Mika ShishidoTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Melanoma é o tipo mais agressivo de tumor de pele e uma das principais causas de morte por tumor de pele, devido a sua alta capacidade metastática. Em termos de estratégias terapêuticas de combate ao melanoma tem-se dado ênfase no controle da resistência e da metástase. Nosso grupo de pesquisa observou que a riboflavina irradiada (RFi) induz apoptose de células de câncer de próstata, renal e leucemia mielóide. Portanto, o objetivo geral deste trabalho foi utilizar a RFi para modular química e geneticamente as vias de transdução de sinal associadas com a sobrevivência, resistência e agressividade do melanoma. Assim, neste trabalho estão apresentados os dados sobre a influência da RFi em diferentes aspectos metabólicos das células de melanoma murino (B16F10), tais como: citotoxicidade, adesão, invasão, migração, capacidade de formação de colônia e em mediadores de transdução de sinal: Src quinase, mTOR e componentes da via sonic hedgehog. Em todos os experimentos a riboflavina (RF) foi previamente irradiada com UVA (dose de 9 J/cm²). Foi observado inibição da proliferação celular com valor de IC50 de 50 ?M. De forma interessante, RFi na faixa de concentração de nanomolar foi eficiente na inibição da formação de colônias. Além disso, causou a redução da adesão das células B16F10, quando utilizada na concentração de 1?M. A capacidade de migração e invasão das células de melanoma foi reduzida na presença da RFi, nas concentrações de 1 e 30 ?M respectivamente, porém a resposta foi independente da dose. A atividade e expressão das metaloproteinases foram diminuídas na presença de RFi, indicando inibição na capacidade de invasão. Sob o contexto de sinalização a RFi modulou negativamente a via sonic hedgehog, PI3K/mTOR e aumentou a expressão da p53 e PTEN. O conjunto de resultados obtidos nesse trabalho mostra que flavinas são candidatas promissoras para a intervenção farmacológica do melanoma
Abstract: Melanoma is the most aggressive type of skin disorder and a major cause of death by skin's disease due to its highly metastatic ability. In terms of melanoma therapeutic strategies has given emphasis on control of resistance and metastasis. Our group observed that irradiated riboflavin (RF) induces apoptosis of prostate cancer cells, kidney cancer cells and myeloid leukemia. Therefore, the goal of this study was to employ irradiated RF for modulating chemical and genetically signal pathways associated with melanoma survival, resistance and aggressiveness. Thus, in this manuscript data about the influence of RF in different cellular metabolic aspects of murine melanoma (B16F10) such as cytotoxicity, adhesion, invasion, migration, colony formation and signal transduction mediators Src kinase, mTOR and sonic hedgehog components, will be presented. In all experiments the RF was previously irradiated with UVA (dose of 9 J/cm²). Inhibition of cell proliferation was observed with IC50 value of 50 ?M. Interestingly, RF in a nanomolar concentration inhibited the formation of colonies. In addition, 1 ?M irradiated RF caused a reduction of B16F10 cells adhesion. The ability of migration and invasion of melanoma cells was reduced in the presence of RF, however, those cells response was dose-independent. The activity and expression of metalloproteinases were diminished indicating reduction of cellular invasiveness capacity. Sonic hedgehog and PI3K/mTOR pathways were negatively modulated and the expression of p53 and PTEN were increased in melanoma cells treated with irradiated RF. The findings showed in this study brought out flavins as promising candidates for pharmacological intervention of melanoma
Doutorado
Bioquimica
Doutor em Biologia Funcional e Molecular
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Ohara, Andre 1989. „Isolamento e seleção de leveduras silvestres de biomas do Estado de São Paulo com potencial para produção de lipase e vitaminas do complexo B“. [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256642.
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Orientador: Gabriela Alves MacedoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: A bioprospecção de micro-organismos representa um grande potencial tecnológico para produção de biocompostos de interesse comercial. Dentre estes compostos estão as enzimas lipolíticas, como as lipases (triacilglicerol acil-hidrolases EC 3.1.1.3) que apresentam um enorme potencial para aplicações biotecnológicas. Outro tipo de biocomposto de relevante interesse comercial são as vitaminas do complexo B, as quais possuem função essencial na atividade de enzimas que regulam reações do metabolismo. Desta forma, o objetivo desse trabalho foi isolar e selecionar linhagens de leveduras do solo de diferentes biomas do Estado de São Paulo com potencial para produção de lipase e de vitaminas do complexo B (biotina e riboflavina). Para tanto, foram isoladas 132 leveduras de amostras de solos provenientes da Mata Atlântica e da região de transição (Mata Atlântica e Cerrado). Essas linhagens foram depositadas na coleção de micro-organismos do laboratório de Bioquímica de Alimentos da FEA-UNICAMP, que já contava com 300 leveduras provenientes da região de Cerrado. As 432 linhagens presentes na coleção foram então avaliadas quanto ao potencial para a produção de lipase extracelular através de seleção em meio sólido diferencial e cultivo em meio líquido, sendo a atividade de lipase determinada no sobrenadante por titulometria de neutralização. O potencial para a produção de biotina e riboflavina extracelular foi avaliada por meio de seleção em meio de cultivo líquido, sendo as concentrações das vitaminas determinadas no sobrenadante por espectrofotometria e fluorimetria. Desta forma 33 leveduras apresentaram potencial para produção de lipase alcançando valores de atividade enzimática que variaram de 6,51 U/mL a 21,44 U/mL. Em relação à produção das vitaminas do complexo B, 38 linhagens apresentaram concentrações de biotina no sobrenadante do cultivo que variaram de 0,28 µg/mL a 18,61 µg/mL e 64 linhagens apresentaram concentrações de riboflavina que variaram de 0,03 µg/mL a 0,77 µg/mL. A linhagem RP.C153 apresentou potencial para produção de lipase e riboflavina, enquanto a linhagem RP.J1308 para produção de lipase e biotina. A linhagem RP.C153 foi classificada como Pichia caribbica e a linhagem RP.J1308 como Candida oleophila
Abstract: The bioprospection of microorganisms represents a great technological potential for the production of biocompounds of commercial interest. Among these compounds are the lipolytic enzymes, such as lipases (triacilglicerol acilhidrolases EC 3.1.1.3) which have currently a huge potential for biotechnological applications. B vitamins are another type of biocompound with relevant commercial interest, which have essential role in the activity of enzymes that regulate metabolic reactions in living organisms. Therefore, the aim of this work was to isolate and select strains of yeasts from the soil of different biomes present in the State of São Paulo for the biotechnological production of lipase and B vitamins (biotin and riboflavin). Thus, 132 yeasts were isolated from soil samples of the Atlantic Forest (Ilha Bela - SP) and the transition region between the Atlantic Forest and Savanna (Campinas - SP). These strains were deposited in the collection of microorganisms of the Food Biochemistry Laboratory FEA - UNICAMP, which already had 300 yeasts from the Savanna region (Ribeirão Preto - SP). Therefore 432 strains present in the collection were then evaluated for their potential to produce extracellular lipase by selection on solid selective differential and liquid medium culture, and the enzyme activity in the supernatant was determined by neutralization titration. The potential production of extracellular biotin and riboflavin was assessed by selection in medium liquid culture, and the concentrations of those vitamins were measured in the supernatant by spectrophotometry and fluorimetry. Therefore 33 yeasts demonstrated potential for the production of lipase, reaching values of enzymatic activity ranging from 6.51 U/mL to 21.44 U/mL. In relation to the production of B vitamins, 38 strains presented concentrations of biotin in the supernatant culture ranging from 0.28 µg/mL to 18.61 µg/mL and 64 strains demonstrated concentrations of riboflavin ranging from 0.03 µg/mL to 0.77 µg/mL. The strain RP.C153 presented potential for production of lipase and riboflavin, while strain RP.J1308 for production of lipase and biotin. The RP.C153 strain was classified as Pichia caribbica and RP.J1308 strain as Candida oleophila
Mestrado
Ciência de Alimentos
Mestre em Ciência de Alimentos
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Øyangen, Julia. „Photoprotection of riboflavin containing beverages“. Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18386.
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Riboflavin, also known as vitamin B2 and one of the most easily absorbed nutrients,can be found in many different organisms. The most abundant source of riboflavin ismilk and dairy products; however it is also present in meat, fish and certain types ofvegetables and fruit. Riboflavin is an important part of a healthy diet in order to keep skin, eyes and nervous systems healthy. Some studies indicate that riboflavin plays an important role in cancer and cardiovascular diseases.As known, milk is extremely sensitive to light. Riboflavin is one of the factorsresponsible for the light-induced degradation of milk. In combination with light andoxygen riboflavin may act as a photosensitizer. When vitamin B2 absorbs blue-greenlight, an excited triplet state of riboflavin is generated through a process called intersystem crossing. Reactive oxygen species, such as singlet oxygen, is then formed by reaction of excited riboflavin triplet with dissolved oxygen present in milk. Light exposure of milk can lead to off-flavor and damage of vitamins by reaction of singlet oxygen with amino acids and lipids in milk. Unfortunately, most of the packaging materials today do not protect milk from light completely. The formation of singlet oxygen can also be prevented by adding quenchers that are able to deactivate riboflavin triplets.Certain amino acids and carotenoids are well known flavin quenchers.The purpose of this study was to investigate how well riboflavin triplets can bequenched by amino acids cysteine, histidine, methionine, tyrosine and tryptophan. Thequenching properties of hydrophilic carotenoid crocin were studied as well. Crocinhas been under investigation of researches at the Departement of Physics at NTNU.Lumiflavin, which is one of the riboflavin’s photodegradation products, was used instead of riboflavin. The former is more stable and has similar photochemical characteristics as the latter.The quenching of lumiflavin triplets was studied by using laser flash photolysis. Itconsists of irradiating the sample under investigation with a short-lived laser flash. The method was used to measure the kinetic decay rate of lumiflavin in aqueous buffer with and without different concentrations of a quencher. The data were fitted to two different decay models. From pseudo-first-order rate constants the quenching rate constants were determined for each amino acid and crocin. All amino acids and crocin used in this study showed a quenching effect on the lumiflavin triplets. Further, it was determined whether the fitting models are suitable for these kind of measurements by simulating the decay of lumiflavin with and without any quencher. More studies on the fitting models have to be done to be able to get reliable results.
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Yates, Catherine Ann. „Gastrointestinal development and riboflavin deficiency“. Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312293.
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Huang, Se-Ne. „Cellular translocation mechanism of Riboflavin /“. The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486572165275525.
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Riether, Gustavo Tokoro. „Aspectos do mecanismo de formação 3-metil-2-buteno-1-tiol em cerveja e a reatividade dos iso-α-ácidos“. Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/75/75132/tde-21092010-091119/.
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A cerveja é uma bebida alcoólica fermentada derivada do amido e aromatizada com lúpulo (Humulus lupulus L.). Os α-ácidos são extraídos do cone do lúpulo e durante o processo de cozimento do mosto são isomerizados em iso-α-ácidos (IAAs), na configuração cis- e trans-, conferindo qualidade de espuma e sabor amargo característico da cerveja. Neste trabalho, é reportado que IAAs sofrem degradação fotossensibilizada por flavinas (Φ = 4,8x10-3 mol einstein-1), mesmo na presença de compostos fenólicos (ácido ferúlico, Φ = 2,0x10-3 mol einstein-1) em excesso molar de 10 vezes, sugerindo que radicais formados pela desativação do estado tripleto excitado da riboflavina por compostos fenólicos possam também estar envolvidos na degradação dos IAAs. Foram identificados dímeros e trímeros derivados do ácido ferúlico e p-coumárico através de LC-ESI-IT-MS como principais fotoprodutos de degradação dos compostos fenólicos. Reportamos a reatividade dos diferentes diastereoisômeros de iso-α-ácidos frente ao radical 2,2-difenil-1-picrilhidrazila (DPPH•), como modelo de radical peroxila, k2 = 0,41 e 1,3 L mol-1 s-1 para a reação com cis-IAA e trans-IAA em meio de etanol acidificado com 1 % ácido fórmico a temperatura de 25 °C, respectivamente. Estas constantes de velocidade específica sugerem que a degradação dos ácidos amargos via reação térmica em processo radicalar é importante no armazenamento do produto já que as constantes de velocidade de reação dos IAAs com o radical DPPH• são competitivas com as observadas para as reações de antioxidantes naturalmente presentes na cerveja com o radical DPPH• ([ácido ferúlico] = 0,2mg/Lcerveja; k2 = 1,18.102 M-1s-1). A análise dos dados termodinâmicos (Mistura de IAAs, ΔH‡ = 25 kJ mol-1 e ΔS‡ = -155 J mol-1 K-1) sugere um mecanismo de oxidação dos IAAs pelo radical DPPH• via HAT/PCET. A diferença de reatividade observada para os diastereoisômeros (cis/trans) está aparentemente relacionada ao arranjo estereoquímico dos grupos laterais isohexonoil e prenil conectados aos carbonos C(4) e C(5), respectivamente. Desta forma, sugere-se que a proximidade espacial dos sítios de insaturação na espécie trans- ocasiona um aumento na densidade eletrônica ou um fator apenas estatístico já que os H-alílicos estão próximos espacialmente, favorecendo desta forma a oxidação via radicalóide.Beer is a fermented alcoholic beverage based on starch and flavored by hops (Humulus lupulus L.). The α-acids are extracted from hop cones and isomerize into iso-α-acids (IAAs) during the wort boiling, in cis- and trans- configuration, providing foam quality and the characteristic bitter taste of beer. In this work, is reported that these compounds undergo degradation photosensitized by flavins (Φ = 4,8x10-3 mol einstein-1), even in the presence of phenolic compounds (ferulic acid, Φ = 2,0x10-3 mol einstein-1) in 10-fold molar excess, suggesting that radicals formed during the deactivation of triplet excited state of riboflavin by phenolic compounds may be involved in the degradation of IAAs. Dimers and trimers derived from ferulic and p-coumaric acids were identified by LC-ESI-IT-MS as the main photoproducts of the phenolic compounds. We report the reactivity of the different diastereoisomers of IAAs towards the 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical, as a model for peroxyl radical, k2 = 0,41 e 1,3 L mol-1 s-1 for the reaction with cis-IAA and trans-IAA in ethanol acidified with 1% of formic acid, at the temperature of 25 °C, respectively. These specifics rate constants suggest that the degradation of the bitter acids via thermal reactions in an radicaloid process is important during the storage of the product since the reaction rate constant for IAAs and the DPPH• radical are competitive with the reaction rate constants for naturally occurring antioxidants in beer with the DPPH• radical ([ferulic acid] = 0,2mg/Lbeer; k2 = 1,18.102 M-1s-1). The analysis of the thermodynamical data (IAAs mixture, ΔH‡ = 25 kJ mol-1 e ΔS‡ = -155 J mol-1 K-1) suggest a HAT/PCET oxidation mechanism of IAAs by DPPH• radical. The difference of reactivity observed for the diastereoisomers (cis-/trans-) is possibly related to the stereochemical arrangement of the isohexonoyl and prenyl side chains connected to C(4) and C(5) carbons, respectively. In this way, is suggested that the spatial proximity of the insaturation sites in the trans- species lead to a increase in electronic density or due to a statistical factor since the allylic-H are close spatially, which favors the oxidation via radicaloid.
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Munive, Mendez María Claudia del Pilar, und Quispe Flavia Jimena Cardenas. „Evaluación in vitro del efecto inhibitorio de la terapia fotodinámica sobre Streptococcus mutans (ATCC® 25175) y Streptococcus sanguinis (ATCC® 10556) en presencia y ausencia de riboflavina“. Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/651668.
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Objetivo: Evaluar el efecto inhibitorio de la terapia fotodinámica (TPD) con Diodo Emisor de Luz (LED) azul sobre Streptococcus mutans y Streptococcus sanguinis en presencia y ausencia de riboflavina (E - 101).
Materiales y métodos: Se realizaron cuatro tratamientos en presencia y ausencia de la exposición de luz LED azul y riboflavina al 0.5% sobre Streptococcus mutans y Streptococcus sanguinis. Las bacterias fueron cultivadas en medio BHI y la unidad de medida utilizada fue las unidades formadoras de colonias (UFC/ml).
Resultados: La fotoactivación con luz LED azul a 40 segundos no tuvo efecto inhibitorio sobre S. mutans y S. sanguinis. Sin embargo, al realizar la terapia fotodinámica en presencia de riboflavina, se observó que el crecimiento bacteriano fue menor (p<0.05). Asimismo, se identificó que la viabilidad bacteriana de S. sanguinis es menor que la de S. mutans, con un 40% y 66% respectivamente.
Conclusiones: Se concluye que la riboflavina tiene un efecto inhibitorio significativo sobre la viabilidad bacteriana de S. mutans y S. sanguinis.Objective: To evaluate the inhibitory effect of photodynamic therapy (TPD) with blue Light Emitting Diode (LED) on Streptococcus mutans and Streptococcus sanguinis in presence and absence of riboflavin (E-101). Materials and methods: Four treatments were performed in presence and absence of blue LED and riboflavin (0.5%) exposure on Streptococcus mutans and Streptococcus sanguinis. The bacteria were grown in BHI medium and the unit of measurement used was the colony forming units (CFU / ml). Results: Photoactivation with blue LED light at 40 seconds had no inhibitory effect on S. mutans and S. sanguinis. However, when performing photodynamic therapy in presence of riboflavin, it was observed that bacterial growth was lower (p <0.05). Likewise, it was identified that bacterial viability of S. sanguinis is lower than S. mutans, with 40% and 66% respectively. Conclusions: It is concluded that riboflavin has a significant inhibitory effect on the bacterial viability of S. mutans and S. sanguinis.
Tesis
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McClelland, David Andrew. „The refolding of riboflavin binding protein“. Thesis, University of Stirling, 1996. http://hdl.handle.net/1893/3408.
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Hen egg riboflavin binding protein (RfBP) acts as a source of riboflavin to the developing embryo. It is the most abundant vitamin binding protein in the egg white. Mutations giving rise to a lack of RfBP lead to embryo death at approximately 13 days. RfBP binds riboflavin tightly in a 1:1 ratio. On formation of this complex, the fluorescence of riboflavin is completely quenched; this quenching is thought to be due to the stacking of aromatic groups within the hydrophobic binding pocket. This quenching provides a convenient assay for the integrity of the riboflavin-binding site of the protein. RfBP consists of a single polypeptide chain of 219 amino acids of molecular mass 29.2 kDa. RfBP undergoes a number of post-translational modifications, namely: the formation of nine disulphide bonds, extensive glycosylation on Asn 36 and Asn 147, and the phosphorylation of eight serine side chains from between Ser 186 and Ser 197. The unfolding and refolding of RfBP was studied by denaturing in 6M guanidium chloride, followed by dilution in buffer, to start refolding. The processes were followed by both steady-state and stopped-flow circular dichroism and fluorescence spectroscopy. RfBP was found to readily unfold and refold, provided the disulphide bonds were intact. The regain of secondary structure was found to be too rapid to measure by the methods available (<12msec). The regain of tertiary structure was found to consist of 4 main phases, and a large proportion (80%) of the tertiary structure formed within 2 msec. The regain of riboflavin binding ability was complete at the end of the second phase, a reaction with a half-life of around 30 msec. In the presence and absence of riboflavin, the kinetics for the first 3 stages of tertiary structure changes seemed to be identical. In the presence of riboflavin, however, seemed to impede the completion of the final, very slow stage, with the refolding reaction only going to 95% completion. The dephosphorylation of the protein seemed to have no affect on this process. When the 9 disulphide bonds are reduced however, RfBP is unable to spontaneously reoxidise to a native-like state in the presence of an oxidised/reduced glutathione redox system. However, the addition of protein disulphide isomerase to the system increases significantly the yield of successfully reoxidised RfBP to about 50%. Attempts to prepare deglycosylated RfBP by chemical methods were unsuccessful since the treatment led to fragmentation of the polypeptide chain.
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Yettella, V. Ramesh Reddy. „Riboflavin Photosensitized Oxidation of Amino Acids“. The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1217897521.
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Kim, Ryuryun Verfasser], und Markus [Akademischer Betreuer] [Fischer. „Biosynthesis of Vitamin B2 (Riboflavin) : Studies on the Reaction Mechanism of Riboflavin Synthase / Ryuryun Kim. Betreuer: Markus Fischer“. Hamburg : Staats- und Universitätsbibliothek Hamburg, 2012. http://d-nb.info/1023947307/34.
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13
Ramsperger, Arne. „Strukturanalyse der Riboflavin-Synthase aus Methanococcus jannaschii“. [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978931084.
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14
Wang, Fan. „UVA/Riboflavin-Induced Apoptosis in Mouse Cornea“. Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-133626.
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Background: A mouse model of combined UVA/riboflavin irradiation to eliminate stromal cells and other antigen-presenting cells in the cornea provides the basis for a probably low risk of corneal transplantation. Methods: After abrasion of the epithelium, the central corneas of mouse eyes were treated with UVA/riboflavin in vitro. Histological studies of hematoxylin-eosin and immunohistochemical staining with caspase 3 were performed. Dissected mouse corneas were analyzed by Western blot. Results: Apoptotic cells were shown on the central corneal stroma; a cell-free zone was displayed in the cornea. Numbers of dead cells increased according to cultivation time. However, the endothelium survived due to the adjustment of the irradiation dose. Conclusions: A cell-free zone in the stroma of the mouse cornea was produced by UVA/riboflavin irradiation in vitro. The technique makes possible to prevent or reduce immunological reactions and the risk of graft rejection by pretreatment of the donor cornea, ultimately prolonging graft survivalDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Abdel-Kader, Z. M. „Diffusion of riboflavin under thermal sterilisation conditions“. Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355374.
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16
Wang, Fan. „UVA/Riboflavin-Induced Apoptosis in Mouse Cornea“. Karger, 2008. https://tud.qucosa.de/id/qucosa%3A27521.
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Background: A mouse model of combined UVA/riboflavin irradiation to eliminate stromal cells and other antigen-presenting cells in the cornea provides the basis for a probably low risk of corneal transplantation.
Methods: After abrasion of the epithelium, the central corneas of mouse eyes were treated with UVA/riboflavin in vitro. Histological studies of hematoxylin-eosin and immunohistochemical staining with caspase 3 were performed. Dissected mouse corneas were analyzed by Western blot.
Results: Apoptotic cells were shown on the central corneal stroma; a cell-free zone was displayed in the cornea. Numbers of dead cells increased according to cultivation time. However, the endothelium survived due to the adjustment of the irradiation dose.
Conclusions: A cell-free zone in the stroma of the mouse cornea was produced by UVA/riboflavin irradiation in vitro. The technique makes possible to prevent or reduce immunological reactions and the risk of graft rejection by pretreatment of the donor cornea, ultimately prolonging graft survival.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Azurdia, Diana Eileen. „The regulation of Riboflavin biosynthesis in Eschrichia coli“. Diss., Restricted to subscribing institutions, 2010. http://proquest.umi.com/pqdweb?did=2026893431&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Klaumünzer, Bastian. „Quantenchemische und molekulardynamische Untersuchungen zur Photoanregung von Riboflavin“. Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2013/6317/.
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Die Photophysik und Photochemie von Flavinen sind aufgrund ihrer biologischen Funktion, inbesondere von Flavoproteinen, von großen Interesse. Flavoproteine spielen eine große Rolle in einer Vielzahl von biologischen Prozessen, z.B. Biolumineszenz, Entfernung von Radikalen, die bei oxidativem Stress entstehen, Photosynthese und DNA-Reparatur. Die spektroskopischen Eigenschaften des Flavin-Cofaktors machen diesen zu einem natürlichen Reporter für Veränderungen innerhalb des aktiven Zentrums. Deshalb sind die Flavoproteine eine der am meisten untersuchten Enzymfamilien. Eine biologische Aktivität des Flavins führt über einen elektronisch angeregten Zustand, wo dann, abhängig von der Aminosäureumgebung, ein bestimmter Mechanismus zu einem biologischen Prozess führt (Photozyklus).
Ein wichtiges Analysetool zum Verständnis des anfänglichen Photoanregungsschritts der Flavine sind die elektronische und die Schwingungsspektroskopie.
In dieser Arbeit wurden die Prozesse von Riboflavin (RF) während und nach optischer Anregung mit theoretischen Mitteln beleuchtet. Dazu wurden quantenchemische Berechnungen für Schwingungsspektren (vibratorische) von Riboflavin, auch Laktoflavin oder Vitamin B2 genannt, dem Grundmolekül der Chromophore biologischer Blaulichtrezeptoren, in dessen elektronischem Grundzustand und dessen niedrigsten angeregten Zustand durchgeführt. Weiterhin wurden vibronische (vibratorische+elektronische) Absorptionsspektren und ein vibronisches Emissionsspektrum berechnet. Die so berechneten Schwingungs- und elektronischen Spektren sind in guter qualitativer wie quantitativer Übereinstimmung mit gemessenen Werten, und helfen so, die experimentellen Signale der Photoanregung von Flavinen zuzuweisen. Unmittelbar nach der Photoanregung wurde ein Verlust des Doppelbindungscharakters im polaren Bereich des Ringssystems beobachtet, was zu der vibronischen Feinstruktur im elektronischen Absorptions- und Emissionsspektrum führte. Hier zeigte sich zudem, dass neben den vibronischen Effekten auch die Lösungsmitteleffekte wichtig für das quantitative Verständnis der Photophysik der Flavine in Lösung sind.
Um Details des optischen Anregungsprozesses als initialen, elementaren Schritt zur Signalweiterleitung zu entschlüsseln, wurden ultraschnelle (femtosekundenaufgelöste) Experimente durchgeführt, die die Photoaktivierung des Flavins untersuchen. Diese Arbeit soll zu einem weiteren Verständnis und der Interpretation dieser Experimente durch das Studium der Post-Anregungsschwingungsdynamik von Riboflavin und mikrosolvatisiertem Riboflavin beitragen. Dazu wurde eine 200 fs lange Molekulardynamik in angeregten Zuständen betrachtet. Durch die Analyse charakteristischer Atombewegungen und durch die Berechnungen zeitaufgelöster Emissionsspektren fand man heraus, dass nach der optischen Anregung Schwingungen im Ringssystem des Riboflavins einsetzen. Mit Hilfe dieser Berechnungen kann die Umverteilung der Energie im angeregten Zustand beobachtet werden.
Neben den theoretischen Untersuchungen zu Riboflavin in der Gasphase und auch in Lösung wurde ein Modell für eine BLUF (Blue-Light Photoreceptor Using Flavin) Domäne, ein Flavin benutzender Photorezeptor, erstellt. Hierbei zeigt sich, dass man die in dieser Arbeit angewendeten Analysemethoden auch auf biologisch relevante Systeme anwenden kann.The photophysics and photochemistry of flavins are due to their biological function, in particular of flavoproteins, of great interest. Flavoproteins play a major role in a variety of biological processes, eg Bioluminescence, removal of free radicals, resulting in oxidative stress, photosynthesis and DNA repair. The spectroscopic properties of the flavin cofactor make this a natural reporter for changes within the active site. Therefore flavoproteins are one of the most studied enzyme families. A biological activity of the flavin via an electronically excited state, which then performs a function of the amino acid environment, a specific mechanism to a biological process (photo cycle). An important analytical tool for the understanding of the initial step of the photoexcitation flavins are the electronic and vibrational spectroscopy. In this study, the processes of riboflavin (RF) during and after optical excitation illuminated by theoretical means. These quantum chemical calculations for the vibrational spectra (vibrational) of riboflavin, or vitamin B2 lactoflavin also been mentioned, the basic molecule of biological chromophores blue light receptors in the electronic ground state and the lowest excited state performed. Furthermore, vibronic (vibrational + electronic) absorption spectra and vibronic emission spectra were calculated. The calculated vibrational and electronic spectra are in good qualitative and quantitative agreement with measured values, and help to assign the experimental signals of the photo-excitation of flavins. Immediately after photoexcitation a loss of the double bond character was observed in the polar region of the ring system, leading to the vibronic fine structure in the electronic absorption and emission spectrum. It showed also that in addition to the vibronic effects, the solvent effects are important for a quantitative understanding of the photophysics of flavins in solution. To decipher details of the optical excitation process as initial, elementary step in signal transduction, ultrafast were performed (femtosecond-resolved) experiments that investigate the photoactivation of the flavin. This work will contribute to a further understanding and interpretation of these experiments by studying the post-excitation vibrational dynamics of riboflavin and riboflavin mikrosolvatisiertem. To a 200 fs long molecular dynamics in excited states was considered. By the analysis of characteristic atomic motions and by the calculations of time-resolved emission spectra, it was found that, after the optical excitation oscillations in the ring system of the riboflavin used. Using these calculations, the energy redistribution in the excited state can be observed. In addition to the theoretical studies of riboflavin in the gas phase and in solution, a model for a BLUF (Blue Light Photoreceptor Using flavin) domain, a flavin-use photoreceptor created. It is shown that one can apply the analytical methods employed in this work and to biologically relevant systems.
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King, Joan M. „Riboflavin Photosensitized Singlet Oxygen Oxidation of Vitamin D“. The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392814029.
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Bradley, Dondeena G. „Riboflavin photosensitized singlet oxygen oxidation in milk products /“. The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu148775817823755.
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Machado, Daisy 1981. „Avaliação da citotoxicidade e fototoxicidade da riboflavina : determinação de marcadores moleculares de inflamação, senescencia e morte celular“. [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314049.
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Orientadores: Carmen Verissima Ferreira, Silvia Mika ShishidoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A riboflavina (RF) é uma vitamina hidrossolúvel pertencente ao complexo vitamínico B2 e precursora das coenzimas FMN e FAD. Além da função biológica como componente de coenzimas, a RF apresenta atividade antitumoral e fotossensibilizante. A proposta principal desse estudo se baseou na avaliação da fototoxicidade da RF, bem como na determinação de marcadores moleculares da inflamação, senescência e morte celular, ações deletérias normalmente desencadeadas pela radiação UVA. Os resultados obtidos indicam que a RF tem potencial aplicação na terapia fotodinâmica, levando se em conta os modelos celulares utilizados, fibroblastos (BALB/c 3T3) e queratinócitos humanos (HaCaT). As células BALB/c 3T3 tratadas com RF 6,0 mM e dose de 5 J/cm² de radiação UVA, apresentaram indução de apoptose principalmente pela via intrínseca. A indução de senescência foi evidenciada pelo aumento da p-caveolina e aumento da atividade da MMP-2 (principal protease responsável pela degradação de colágeno). De acordo com os níveis de NFkB e p- IKKa/b, a RF não alterou significativamente o processo de inflamação desencadeado pela radiação UVA. Nas células HaCaT, o tratamento com 5,0 mM de RF e dose de 5 J/cm² de radiação UVA levou a ativação da apoptose induzida tanto pela via extrínseca como pela intrínseca. O aumento nos níveis de p-caveolina, p21 e da atividade das MMPs-2 e -9 sugerem à indução de processo de senescência precoce também nos queratinócitos. Além disto, a diminuição da expressão do NF?B indica que o mesmo esteja se translocando para o núcleo e, portanto, regulando a resposta inflamatória. Outro aspecto avaliado foi a influência do copolímero F-127 na fototoxicidade da RF. A irradiação do hidrogel contendo F-127 e riboflavina manteve a propriedade fototóxica da mesma. Nossos dados sugerem que a RF apresenta potencial para uso em terapia fotodinâmica, uma vez que a mesma se mostrou fototóxica quando irradiada com doses subtóxicas de radiação UVA.
Abstract: Riboflavin (RF) is a water soluble vitamin which belongs to vitamin B2 complex, an essential precursor of FMN and FAD coenzymes. Besides being a component of coenzymes, RF displays antitumoral and photossensitizing activities. The main proposal of this study was to evaluate the RF phototoxicity, as well as to determine molecular markers of inflammation, senescence and cellular death, deleterious actions normally triggered by the UVA radiation. Taking into consideration both cell lines used as models, fibroblasts (BALB/c 3T3) and human keratinocytes (HaCaT), the results obtained indicate that RF has potential application in photodynamic therapy. BALB/c 3T3 cells treated with 6.0 µM RF associate with UVA radiation (5 J/cm²) showed apoptosis induction mainly via intrinsic pathway. An increase of p-caveolin and MMP-2 activity (major protease responsible for degradating collagen) evidenced senescence induction. According to NF?B and p-IKKa/ß levels, RF did not significantly change the process of inflammation triggered by UVA radiation, in fibroblast cells. In HaCaT cells 5.0 µM RF associated with UVA radiation (5 J/cm ²) was observed apoptosis induction thorough extrinsic and intrinsic pathways. Senescence process was also observed in keratinocytes as indicated by an increase of pcaveolin, p21 and MMPs-2 and -9 activities. Besides, the decrease of NF?B expression indicates that this transcription factor translocates into the nucleus and in turn, regulates inflammatory response. Other aspect evaluated in this work was the influence of the F-127 in the RF phototoxicity. The irradiation of hydrogel containing F-127 and RF remained RF phototoxicity property. Our findings suggest that RF displays potential for use in photodynamic therapy, once it was phototoxic when irradiated with subtoxic UVA dose
Mestrado
Bioquimica
Mestre em Biologia Funcional e Molecular
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Urzêdo, Ana Carolina Borges de 1980. „Foto-oxidação do leite microfiltrado pasteurizado : influência do tipo de embalagem e intensidade da luz“. [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255800.
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Orientador: Walkiria Hanada ViottoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: A foto-oxidação do leite é o fator determinante na vida de prateleira do leite microfiltrado pasteurizado. A exposição do leite à luz, nas gôndolas dos supermercados, desencadeia a foto-oxidação da riboflavina e das proteínas do leite, provocando mudanças na cor e formação de off-flavors. O objetivo do trabalho foi verificar, em condições reais, a influência do tipo de embalagem e da intensidade da luz na degradação da riboflavina, formação de lumicromo, oxidação de proteína, cor e vida de prateleira do leite desnatado microfiltrado pasteurizado. Leite desnatado microfiltrado pasteurizado foi acondicionado em garrafas de vidro e de polietileno de alta densidade, e armazenados no escuro (controle) e sob incidência de luz (500 e 1200 lux), durante 14 dias de estocagem refrigerada. Análises de espectroscopia de fluorescência da riboflavina, lumicromo, triptofano e ditirosina e análise de cor instrumental foram realizadas para acompanhar a foto-oxidação dos componentes do leite. Para estimar a vida de prateleira do leite microfiltrado pasteurizado, sob diferentes condições de luz e embalagem, contagens de micro-organismos mesófilos aeróbios e análise sensorial com assessores treinados, teste de aceitação e intenção de compra foram realizados durante o tempo de armazenamento refrigerado. Assessores foram treinados para avaliação da cor, aroma e sabor característicos de leite desnatado e de leite desnatado oxidado. Aos 14 dias de estocagem refrigerada, 76,1% da riboflavina foi degradada no leite exposto à radiação de 500 lux. Já a 1200 lux, esse valor foi de 86,4%. A degradação da riboflavina, a formação de lumicromo e a fotodegradação do triptofano foram maiores e mais rápidas quando a intensidade de luz foi mais intensa (1200 lux). Durante o armazenamento refrigerado, a oxidação das proteínas resultou em desnovelamento da estrutura terciária, e consequentemente, em exposição e posterior degradação do triptofano. No período estudado, houve somente formação de ditirosina para os leites submetidos à intensidade de luz mis intensa (1200 lux). A vida de prateleira dos leites armazenados no escuro (controle) foi de 10 a 14 dias. O aparecimento do sabor oxidado, proveniente da foto-oxidação dos componentes do leite, foi o parâmetro determinante para o fim da vida de prateleira dos leites armazenados sob luz. O tipo de embalagem somente influenciou a vida de prateleira do leite, quando a intensidade de exposição à luz foi mais baixa (500 lux). Nessa intensidade de radiação luminosa, a vida de prateleira do leite pasteurizado aumentou de 4-6 dias para 10-13 dias, quando a embalagem de vidro foi substituída pela de polietileno
Abstract: Photo-oxidation of milk is probably the main cause for the end of shelf life of a microfiltered pasteurized milk. Milk is inevitably exposed to light on the supermarket shelves, which triggers the photo-oxidation of riboflavin and milk proteins, affecting the sensory quality with changes in color and formation of off-flavors. The objective was to verify, in real conditions, the influence of the type of packaging and the light intensity on the riboflavin degradation, protein oxidation, color, shelf life of microfiltered pasteurized skim milk. After processing, milk was packaged in glass and high density polyethylene bottles and stored in the dark (control) and under influence of light (500 and 1200 lux), during 14 days of refrigerated storage. Analyses of fluorescence spectroscopy of riboflavin, lumicrome, tryptophan and dityrosine and instrumental color were performed to monitor the photo-oxidation of milk components. The shelf life of pasteurized microfiltered skim milk, under different light conditions and packaging was estimated by standard plate count of aerobic mesophilic and sensory analysis with trained assessors, acceptance testing, and purchase intent, during refrigerated storage time. Assessors were trained to evaluate sensorially the color, aroma and flavor of skim milk and oxidized skim milk. At 14 days of refrigerated storage, 76.1% of riboflavin was degraded in milk exposed to radiation of 500 lux. However, at 1200 lux, degradation of riboflavin reached 86.4% of its initial content in milk. Riboflavin degradation, lumicrome and tryptophan formation were higher and faster when light intensity was more intense (1200 lux). During storage time, the oxidation of proteins resulted in the tertiary structure unfolding, and exposure and subsequent degradation of tryptophan. During this period of time, there was formation of dityrosine only for the milks exposed to more intense light radiation (1200 lux). The shelf life of milk stored in the dark (control) was 10-14 days. The development of oxidized flavor, derived from the photo-oxidation of milk components, was the main parameter for determining the ending of the shelf life of milk stored under light. Packaging material influenced the milk shelf life when the intensity of light was lower (500 lux). In this condition, the shelf life of pasteurized milk increased from 10-13 days to 4-6 days when the glass container was replaced by polyethylene bottle
Doutorado
Tecnologia de Alimentos
Doutora em Tecnologia de Alimentos
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Melo, Julliane Tamara Ara?jo de. „An?lise da express?o de APE1 ap?s estresse oxidativo induzido em c?lulas proficientes e deficientes na via de reparo por excis?o de nucleot?deos“. Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/13055.
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Previous issue date: 2010-06-28Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
Riboflavin is a vitamin very important in aerobic organisms, as a precursor of many coenzymes involved in the electron transporter chain. However, after photosensitization of riboflavin with UV or visible light, it generates reactive oxygen species (ROS), which can oxidize the DNA. The repair of oxidative lesions on DNA occurs through the base excision repair pathway (BER), where APE1 endonuclease plays a central role. On the other hand, the nucleotide excision repair pathway (NER) repairs helix-distorting lesions. Recently, it was described the participation of NERproteins in the repair of oxidative damage and in stimulation of repair function fromAPE1. The aim of this research was to evaluate the cytotoxic effects of photosensitized riboflavin (RF*) in cells proficient and deficient in NER, correlating with APE1 expression. For this propose, the cells were treated with RF* and it was performed the cell viability assay, extraction of whole proteins, cells fractionation, immunoblotting, indirect immunofluorescence and analysis of polymorphisms of BER gens. The results evidenced that cells deficient in XPA and CSB proteins were more sensitive to RF*. However, XPC-deficient cells presented similar resistance to MRC5- SV cells, which is proficient in NER. These results indicate that XPA and CSB proteins have an important role on repair of oxidative lesions induced by RF*. Additionally, it was evidenced that single nucleotide polymorphisms (SNPs) in BER enzymes may influence in sensitivity of NER-deficient cell lines. Concerning the APE1 expression, the results showed that expression of this protein after treatment with RF* only changed in XPC-deficient cells. Though, it was observed that APE1 is recruited and is bound to chromatin in MRC5-SV and XPA cells after treatment with RF*. The results also showed the induction of DNA damage after treatment with RF*, through the analysis of-H2AX, since the treatment promoted an increase of endogenous levels of this phosphorylated protein, which acts signaling double strand-break on DNA. On the other hand, in XPC-deficient cells, regardless of resistance of RF*, the endogenous levels of APE1 are extremely reduced when compared with other cell lines and APE1 is not bound to chromatin after treatment with RF*. These results conclude that RF* was able to induce cell death in NERdeficient cells, where XPA and CSB cells were more sensitive when compared with MRC5-SV and XPC-deficient cells. This last result is potentially very interesting, since XPC-deficient cell line presents low levels of APE1. Additionally, the results evidenced that APE1 protein can be involved in the repair of oxidative damage induced by RF*, because APE1 is recruited and bound strongly to chromatin after treatment.
A riboflavina ? uma vitamina de fundamental import?ncia em organismos aer?bios, sendo precursora de importantes coenzimas que participam da cadeia transportadora de el?trons. Contudo, ap?s a sensibiliza??o da riboflavina com luz UV ou luz vis?vel, observou-se a forma??o de esp?cies reativas de oxig?nio (EROs), as quais podem oxidar o DNA. O reparo de les?es oxidativas no DNA ocorre principalmente atrav?s da via de reparo por excis?o de bases (BER), na qual a endonuclease APE1 exerce um papel central. Por sua vez, a via de reparo por excis?o de nucleot?deos (NER) atua reparando les?es no DNA que causam distor??es na dupla h?lice. Recentemente tem sido descrito a participa??o da via NER na remo??o de danos oxidativos e na estimula??o da fun??o de reparo de APE1. Desta forma, o objetivo desta pesquisa foi analisar os efeitos citot?xicos da riboflavina fotossensibilizada (RF*) em c?lulas proficientes e deficientes na via NER, correlacionando ? express?o de APE1. Para tanto, as linhagens proficientes e deficientes no NER foram submetidas ao tratamento com RF* e em seguida foram realizados os ensaios de viabilidade celular, extra??o de prote?nas totais, fracionamento celular, immunoblotting, imunofluoresc?ncia indireta e a an?lise de polimorfismos em genes da via BER. Os resultados evidenciaram perfis de sensibilidade distintos ao estresse oxidativo induzido pela RF*, onde as linhagens XPA e CSB foram mais sens?veis, enquanto a linhagem XPC mostrou resist?ncia similar ? linhagem MRC5-SV, a qual ? proficiente na via NER. Esses resultados indicam que as prote?nas XPA e CSB possuem um importante papel no reparo das les?es oxidativas induzidas pela RF*. Al?m disso, foi demonstrado que polimorfismos em um ?nico nucleot?deo (SNPs) em enzimas do BER podem influenciar na sensibilidade dessas linhagens. Em rela??o ?s an?lises dos n?veis de express?o de APE1, os resultados mostraram que houve altera??o na express?o dessa prote?na ap?s o tratamento com RF* somente na linhagem deficiente em XPC. Por?m, observou-se que APE1 ? recrutada e se torna ligada ? cromatina ap?s o tratamento nas linhagens MRC5-SV e XPA. Os resultados tamb?m comprovaram a indu??o de danos ap?s o tratamento com RF* atrav?s do estudo da prote?na-H2AX, pois o tratamento provocou um aumento nos n?veis end?genos desta prote?na fosforilada, a qual atua na sinaliza??o de quebras de fita dupla no DNA. Por?m, na linhagem XPC, al?m de ter sido observado uma curva de sobreviv?ncia semelhante ? linhagem MRC5-SV, os n?veis end?genos de APE1 s?o significativamente reduzidos quando comparados com as outras linhagens e APE1 n?o se encontra ligada ? cromatina ap?s tratamento com RF*. Conclui-se que a RF* foi capaz de induzir a morte celular em linhagens deficientes no sistema de reparo por excis?o de nucleot?deos, onde as linhagens XPA e CSB foram mais sens?veis quando comparadas ? linhagem normal MRC5-SV e ? linhagem XPC. Este ?ltimo resultado ? potencialmente interessante, considerando que a linhagem XPC apresenta baixos n?veis prot?icos de APE1. Adicionalmente, os resultados comprovaram que a prote?na APE1 pode estar envolvida no reparo de danos oxidativos causados pela RF*, j? que APE1 ? recrutada na cromatina e se liga fortemente a esta ap?s o tratamento.
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Kemter, Kristina. „Untersuchungen zur Riboflavin-Synthase und Flavokinase aus verschiedenen Organismen“. [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966109163.
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Ferreira, Matheus. „The Kinetics and Dynamics of Schizosaccharomyces pombe Riboflavin Kinase“. Thesis, Umeå universitet, Kemiska institutionen, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-150544.
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Lee, Sungsook. „Studies on the biosynthesis of 5-deazaflavin and riboflavin“. The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1341848901.
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Souza, Bianca Rodrigues de. „Quantificação das vitaminas do complexo B (B1, B2) e vitâmeros das vitaminas B3 e B6 em amostras de pólen apícola desidratado provenientes da Região Sul do Brasil“. Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/9/9131/tde-27052015-141055/.
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Entende-se por pólen apícola o resultado da aglutinação do pólen das flores, efetuado pelas abelhas operárias, mediante néctar e substâncias salivares, o qual é recolhido no ingresso da colmeia. A literatura descreve que esse alimento contém proteínas, carboidratos, lipídeos, vitaminas e minerais. De acordo com estudo prévio, amostras de pólen apícola in natura e desidratado, da cidade de Pariquera-Açu (São Paulo), apresentaram teores significativos de vitamina B1(tiamina) e B2 (riboflavina), além da presença dos vitâmeros da vitamina B3 (ácido nicotínico e nicotinamida) e B6 (piridoxal, piridoxol e piridoxamina) em sua composição o que foi associado à flora local explorada pelas abelhas. A região Sul do Brasil possui clima, relevo e vegetação diferenciados de outras regiões, necessitando-se assim da verificação do potencial vitamínico deste produto local. Destaca-se, ainda, o fato de que nesta região encontra-se um dos dois maiores produtores nacionais de pólen apícola (estado de Santa Catarina). O presente trabalho teve como objetivo principal quantificar os teores das vitaminas do complexo B: vitaminas B1 e B2, assim como os vitâmeros das vitaminas B3 e B6. Foram coletados 28 lotes de pólen apícola desidratado de diferentes localidades da região Sul durante o período de agosto de 2011 a dezembro de 2012 que posteriormente foram armazenados, a -18 °C até o momento das análises. As vitaminas do complexo B foram analisadas por cromatografia liquida de alta eficiência (CLAE) na matriz pólen apícola desidratado e os resultados foram expressos em base seca. Entre as amostras analisadas foram verificados teores de vitamina B1 variando entre 0,46 e 1,83 mg / 100 g de pólen apícola; vitamina B2 de 0,40 à 1,86 mg / 100 g e quanto à vitamina B6 apenas os vitâmeros piridoxal e piridoxamina puderam ser quantificados em todos os lotes analisados. O piridoxal teve variação entre as amostras de 0,42 à 6,70 mg / 100 g e a piridoxamina de 0,26 à 0,95 mg / 100g. Em relação à vitamina B3, o vitâmero ácido nicotínico apresentou-se nos diferentes lotes variando de 0,68 à 3,93 mg / 100 g e a nicotinamida de 0,27 à 5,54 mg / 100 g de produto. Tomando-se como porção sugerida para consumo diário 25 g de pólen apícola, verificou-se que num total de 28 amostras, 15 foram consideradas fontes e 2 como ricas em tiamina; 19 lotes foram fontes e 3 ricos em riboflavina, e; 2 lotes foram fontes e 26 ricos em piridoxina segundo à Ingestão Diária Recomendada (IDR) para adultos como disponibilizado na Resolução de Diretoria Colegiada (RDC) nº. 269, de 22 de setembro de 2005.Bee pollen is understood to be the result of agglutination of pollen from flowers, made by worker bees, and nectar through salivary substances, which is collected at the hive entrance. The literature describes that this product contains proteins, carbohydrates, lipids, vitamins, minerals. Previous study with fresh and dehydrated bee pollen, from the city of Pariquera-Açu (São Paulo) showed significant levels of vitamin B1 (thiamine), B2 (riboflavin), presence of B3 (nicotinic acid and nicotinamide) and B6 (pyridoxal, pyridoxamine, piridoxol) vitamins vitamers in its composition which was associated with the local flora explored by bees. Southern Brazil has a differentiated climate, topography and vegetation from other regions, thus requiring verification of vitamin potential of this local product. Also stands out the fact that this region is one of the two largest national producers of bee pollen (Santa Catarina state). This study aimed to quantify the levels of B complex vitamins: vitamins B1, B2, as well as the vitamers of vitamins B3 and B6. Thus, it was collected 28 batches of dehydrated bee pollen from different locations in the South during the period from August 2011 to December 2012. Samples were obtained and subsequently stored at -18 ° C until the analysis time. B vitamins were analyzed by high performance liquid chromatography (HPLC) in bee pollen dehydrated matrix and results were expressed on a dry basis. Among the samples it levels of vitamin B1 varied from 0.46 to 1.83 mg / 100 g; vitamin B2 from 0.40 to 1.86 mg / 100 g; and for vitamin B6, only the pyridoxal and pyridoxamine vitamers could be quantified in all analyzed batches. The pyridoxal had variation between samples from 0.42 to 6,70 mg / 100 g and pyridoxamine from 0.26 to 0.95 mg / 100g. Taking 25 g of bee pollen as suggested for daily intake portion, it was found in a total of 28 samples that 15 were considered sources and 2 rich in thiamine; 19 lots were sources and 3 rich in riboflavin, and; 2 lots were sources and 26 rich in pyridoxine in relation to the Reference Daily Intake (RDI) for adults as provided in Resolução de Diretoria Colegiada (RDC) nº 269, de setembro de 2005.
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Schramek, Nicholas. „Kinetische Untersuchungen von Enzymen der Tetrahydrobiopterin-, Riboflavin- und Folsäure-Biosynthesewege“. [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962156507.
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Bauer, Stefanie. „Röntgenkristallographische Untersuchung von Proteinen der Biosynthese von Riboflavin und Tetrahydrofolat“. [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=973069473.
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Schott, Anne-Kathrin. „Biochemische und strukturelle Charakterisierung von Enzymen der Riboflavin- und Folsäurebiosynthese“. [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969624212.
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Kim, Hyun Jung. „Oxidation mechanism of riboflavin destruction and antioxidant mechanism of tocotrienols“. Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1184681773.
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Crossley, Rachel Amanda. „The role of riboflavin in the physiology of Campylobacter jejuni“. Thesis, University of East Anglia, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426604.
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Hamilton, Jeffrey Hunt. „Photochemical Protection of Riboflavin and Tetrapyrroles with Light Scattering Technology“. Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/76811.
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The effectiveness of titanium dioxide (TiO?) in polyethylene films at preventing the photooxidation of riboflavin in a model solution was evaluated. Five different TiO? loads (0.5-8.0 wt%), each at 3 different thicknesses (50-100 um) were evaluated. A photochemical reactor, equipped with a 350W mercury lamp, provided full spectrum light or narrow bandwidth wavelength exposure, using filters allowing transmission at 25 nm wavebands at maximum peak height at 450, 550, or 650 nm. Riboflavin concentration was measured by HPLC over 8 hours of exposure. Increased TiO? load and thickness significantly affected riboflavin photooxidation (p<0.05). TiO? load had more influence on protection provided to riboflavin than did film thickness. Film opacity correlated linearly with decreased photooxidation (R2 of 0.831 & 0.783 for full spectrum and 450 nm bandpass-filter sets, respectively). Riboflavin photooxidation proceeded most rapidly with the full spectrum exposure (light intensity 118 ° 17.3 mW). Photooxidation occurred in the 450 nm bandpass-filter, but not for 550 & 650 nm sets (light intensities of 2.84 °0.416, 3.36 °0.710, and 0.553 ° 0.246 mW, respectively). Effect of fluorescent light-exposure (2020-1690 lux) on the same system was monitored over 2 days. Riboflavin degradation in the photoreactor proceeded ~300 times faster than under fluorescent lighting. Riboflavin degradation was found to significantly increase with the addition of chlorophyll-like tetrapyrroles (p<0.05). Riboflavin was found to significantly decrease the degradation rate of the tetrapyrroles pyropheophytin a and pheophytin a (p<0.05). The decrease in rate was not significant for chlorophyll a (p>0.05).Master of Science in Life Sciences
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McAuley, Emma. „Riboflavin, MTHFR genotype and blood pressure : implications for personalised nutrition“. Thesis, Ulster University, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.706468.
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Hypertension is the most common risk factor for cardiovascular morbidity and mortality affecting approximately 1 billion people worldwide. Recently evidence has called for a more rigorous approach to lower blood pressure (BP) to levels below the current threshold. Thus, there is a clear need to identify new strategies for the prevention and treatment of hypertension including targeted, non-pharmacological approaches to reduce BP. A common polymorphism (C677T) in the folate metabolising enzyme methylenetetrahydrofolate reductase (MTHFR) has been associated with hypertension. Furthermore, in three randomised controlled trials previously conducted at this centre riboflavin (required as a cofactor for MTHFR) has been shown to effectively lower BP in cardiovascular disease (CVD) and hypertensive patients homozygous for the MTHFR C677T polymorphism (TT genotype) in premature CVD and hypertensive patients. No previous study has however considered the BP lowering effect of riboflavin at a higher dose than previously used (1.6mg/d), or indeed considered how this novel option might translate to patient care. Finally the role of this polymorphism in the development of hypertension over time has not been previously considered. The aim of this thesis therefore was to investigate the role of the MTHFR C677T polymorphism and its interaction with riboflavin, in determining BP in generally healthy adults, and to consider the implications of this gene-nutrient interaction for a personalised nutrition approach to managing hypertension. The findings from a 10-year follow up study provide evidence that adults with the TT genotype had a higher systolic BP than those with the CC/CT genotypes at any given age from 40-65 years. Furthermore, individuals with the TT genotype had a BP in the hypertensive category at a younger age, an effect that appears to be significantly influenced by riboflavin, with the highest BP in adults with the TT genotype in combination with low riboflavin status (ft =0.155, P <0.034). In a randomised controlled trial, that investigated the BP lowering of riboflavin, preliminary findings suggest that the BP response to riboflavin may be strongest in younger adults (<55 years) and in females, but this requires further investigation and no firm conclusions can be made until this trial reaches completion (mid 2016). The GPs and genetically at-risk adults investigated reported a positive attitude towards the novel role of riboflavin in the prevention and treatment of hypertension. In conclusion, the MTHFR 677TT genotype is an important determinant of BP, furthermore in these genetically at risk individuals riboflavin offers a novel preventive and a treatment option for hypertension.
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Graham, Joanne Mimi. „Benefits of riboflavin plus iron supplementation for pregnant Nepali women /“. For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Thesis (Ph. D.)--University of California, Davis, 2004.Degree granted in Nutrition. Dissertation completed in 2003; degree granted in 2004. Also available via the World Wide Web. (Restricted to UC campuses).
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Hiltunen, Hanna-Maija. „Functional analysis of RIBA, the introductory enzyme for Riboflavin biosynthesis“. Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17525.
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Flavinmononukleotid (FMN) und Flavin-Adenin-Dinukleotid (FAD) gehören zu den wichtigsten Redox-Coenzymen und sind an zentralen Stoffwechselprozessen aller Organismen beteiligt. Sie entstehen aus Riboflavin (Vitamin B2). Das bifunktionale RIBA Enzym, das Peptiddomänen für die GTP Cyclohydrolase II (GCHII) und 3,4-Dihydroxy-2-Butanon-4-Phosphat-Synthase (DHBPS) Aktivität umfasst, führt die beiden ersten Schritte der Riboflavin Biosynthese in Pflanzen durch. Die RIBA Proteine werden durch drei Gene in Arabidopsis thaliana und anderen Blütenpflanzen kodiert. Eines der Ziele war es, die physiologischen Rollen der drei RIBA Isoformen aufzuklären. Detaillierte enzymatische Untersuchungen wurden mit rekombinanten RIBA Proteinen IN VITRO durchgeführt. Es wurde gezeigt, dass RIBA2 und RIBA3 jeweils die GCHII oder die DHBPS Aktivität verloren haben. Des Weiteren konnte die Phosphorylierung von RIBA1, sowie die Hemmung von dessen GCHII Aktivität durch FMN nachgewiesen werden. Ein Knockout von RIBA1 führte zu Embryoletalität. Die schrittweise Reduzierung des RIBA1 Proteingehaltes in Arabidopsis, welches zu einem verringerten Flavingehalt führte, ergab einen schwerwiegenden Bleichungsphänotyp. Die konstitutive Antisense-Mutante, sowie das Verfahren des Virus-induzierten Gen-„Silencing“ wurden verwendet, um den durch RIBA1-Mangel hervorgerufenen Flavin-Defizienz-Effekt zu beschreiben. Eine Metabolomics Analyse ergab, dass die Abnahme des Flavingehaltes zu einer Deregulierung verschiedener Zitronensäurezyklus assoziierten Flavoenzyme und zu einer starken Reduktion der katabolischen Kapazität diverser Aminosäuren führt, während flavinabhängige Stickstoffassimilationsprozesse eher priorisiert wurden. Diese Arbeit leistet einen Beitrag zur Erweiterung des Kenntnisstands über den pflanzlichen Riboflavin Biosyntheseweg, sowie zum Verständnis über die Folgen von Flavinmangel in Pflanzen. Darüber hinaus wird hier der erste Versuch zu Erhöhung des Vitamin B2-Gehalt in Pflanzen beschrieben.Flavin mononucleotide (FMN) and Flavin adenine dinucleotide (FAD) belong to the main redox coenzymes and are involved in central metabolic processes. They derive from riboflavin also referred to as vitamin B2. The bifunctional RIBA enzyme, which comprises peptide domains for GTP cyclohydrolase II (GCHII) and 3,4-dihydroxy-2-butanone-4-phosphate synthase (DHBPS) activity, performs the two initial steps of riboflavin biosynthesis in plants. Three genes encode RIBA proteins in Arabidopsis thaliana and many other flowering plants. One of the main aims of this study was to elucidate the physiological roles of the three RIBA isoforms. Detailed enzymatic studies were performed with recombinant RIBA proteins IN VITRO. It revealed for RIBA2 and RIBA3 the loss of either GCHII or DHBPS activity, respectively. The phosphorylation of RIBA1 as well as the inhibition of its GCHII activity by FMN could be demonstrated. A knockout of RIBA1, encoding the dominant RIBA isoform, led to embryo lethality. The gradual reduction of the RIBA1 protein content in Arabidopsis was associated with reduced flavin amounts and a severe bleaching phenotype that was caused by the gradual loss of pigments during leaf development. Flavin deficiency effects caused by RIBA1 depletion were characterised with a constitutive antisense mutant and the virus induced gene silencing method. A comprehensive metabolite profiling, revealed that the loss of almost one third of total flavin content led to a deregulation of several citric acid cycle-associated flavoenzymes. Moreover, a severe reduction of the catabolic capacity of numerous amino acids is seen, while seemingly flavin-dependent processes of the nitrogen assimilation are prioritised. In summary, this thesis contributes to the extended knowledge about the riboflavin biosynthesis pathway as well as to the understanding about consequences of flavin deficiency in plants. Moreover, the first attempt to increase the vitamin B2 content in plants is presented.
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Chaves, Neto Antonio Hernandes. „Flavinas promovem mudanças na matriz extracelular, vias de transdução de sinal, enzimas antioxidantes e metaloproteinases durante a diferenciação de osteoblastos“. [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314035.
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Orientador: Carmen Verissima FerreiraTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Riboflavina (Rb - Vitamina B2) é o precursor das flavocoenzimas essenciais flavina mononucleotídeo (FMN) e flavina adenina dinucleotídeo (FAD). Estas coenzimas participam de processos enzimáticos dependentes das reações de transferências de elétrons, que ocorrem nas vias de produção de energia, biossíntese, desintoxicação e sequestro de elétrons. O aumento dietético da riboflavina e piridoxina foi associado com maiores densidades minerais em mulheres e homens idosos. Fotoderivados da riboflavina demonstraram efeitos citotóxicos em células cancerosas de próstata e leucemias, entretanto, o efeito direto da Rb e seus fotoderivados em osteoblastos não foram examinados. Neste trabalho os efeitos biológicos da Rb e riboflavina irradiada (IRb) foram investigados na linhagem de pré-osteoblastos MC3T3-E1, um modelo bem aceito de osteogênese in vitro caracterizado pela indução de genes específicos associados com o fenótipo osteoblástico quando tratados com ácido ascórbico e ß-glicerofosfato. A viabilidade celular foi avaliada através da redução do MTT, da incorporação do corante vermelho neutro e do conteúdo de ácidos nucléicos. Marcadores de diferenciação osteoblástica foram analisados através do RT-PCR semi-quantitativo (osteopontina e osteocalcina) e através de análises colorimétricas de atividade da fosfatase alcalina (FAL) e síntese de colágeno pela coloração de picrosirius. As atividades das metaloproteinases (MMP) -9 e -2 foram avaliadas pela zimografia de gelatina. Microarranjos de peptídeos com subtratos específicos para quinases e imunoblotting foram usados para identificar os efeitos na sinalização celular. As atividades de enzimas antioxidantes (superóxido dismutase, catalase, glutationa peroxidase e glutationa S-transferase) foram determinadas em lisados celulares usando métodos espectrofotométricos. As atividades das caspases-8, -9 e -3 foram analisadas através de métodos colorimétricos. Na primeira análise Rb e IRb causaram a parada do ciclo celular na fase G0/G1 e também a inibição da quinase AKT, um mediador da proliferação. Flavinas causaram a diferenciação de pré-osteoblastos, evidenciada pelo aumento da expressão de osteocalcina, osteopontina e BMP-2. Atividades mais elevadas de MMP-9 e MMP-2 também foram observadas. A capacidade das flavinas em engatilhar a diferenciação de osteoblastos foi reforçada pelo aumento da conexina 43, diminuição da caveolina-1 e repressão da sinalização Notch. Na segunda análise, nós encontramos que as interações entre Rb, em sua forma irradiada e não-irradiada, e indutores osteogênicos (ácido ascórbico e ß-glicerofosfato) afetaram significativamente a proliferação de osteoblastos, a atividade de FAL, biossíntese de colágeno, expressão de osteocalcina e osteopontina, a atividade das MMP-2 e MMP-9 e a expressão de fatores osteoclastogênicos (RANKL e osteoprotegerina). Nós também encontramos que os efeitos das flavinas em osteoblastos nesta segunda etapa foram independentes das suas propriedades antioxidantes. A atividade biológica da combinação de indutores osteogênicas com Rb e seus fotoprodutos foi associada com a ativação de diferentes vias de sinalização (AKT, FAK, CaMKII), caspases -8, -9 e -3 e aumento da expressão e/ou estabilização de fatores de transcrição osteoblásticos (Runx2 e ß-catenin). Este estudo nos trouxe fortes evidências que altas concentrações de Rb e IRb geraram um microambiente osteogênico através da modulação de diferentes vias de sinalização, além de promover um efeitos aditivo durante a diferenciação das células pré-osteoblasticas MC3T3 induzida por ácido ascórbico e ß- glicerofosfato. Em resumo, este estudo aponta para uma potencial aplicação da Rb e seus fotoprodutos no desenvolvimento do fenótipo osteoblástico e, consequentemente, uma alternativa terapêutica coadjuvante para osteoporose.
Abstract: Riboflavin (Rb-Vitamin B2) is the precursor of essential flavocoenzymes, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These coenzymes participate in numerous enzymatic processes dependent on electron transfer reactions that occur in energyproducing, biosynthetic, and detoxifying and electron-scavenging pathways. Increase dietary riboflavin and pyridoxine intake has been associated with higher bone mineral density in elderly men and women. Photoderivatives of riboflavin have been shown strong activity in haematological malignancy and prostate cancer cells, however, the direct effect of Rb and its photoderivatives on osteoblast has not been examined. In this work, the biologic effects of Rb and irradiated riboflavin (IRb) were investigated in the MC3T3-E1 pre-osteoblastic cell line, a well-accepted model of osteogenesis in vitro characterized for the induction of specific genes associated with the osteoblastic phenotype when treated with ascorbic acid and ß-glycerophosphate. Cell viability was assessed by MTT reduction, neutral red uptake and nucleic acids content. Osteoblastic differentiation markers were analyzed by semiquantitative RT-PCR (osteopontin and osteocalcin), alkaline phosphatase (ALP) activity measured colorimetrically and collagen synthesis by Sirius red staining. Metalloproteinases (MMP) -9 and -2 activities were assayed by gelatin zymography. Peptide microarray of substrate specificity to kinases and immunoblotting were used to identify the effects on signal transduction pathways. Antioxidant enzyme activities (superoxide dismutase, catalase, glutathione peroxidase and glutathione Stransferase) were determined in cellular lysate using spectrophotometric methods. Caspase-8, -9 and -3 activation were measured by a colorimetric assay. In the first analysis Rb and IRb caused cell cycle arrest at G0/G1 phase and accordingly inhibited AKT kinase, a proliferation mediator. Flavins caused differentiation of preosteoblast cells as evidenced by increase of osteocalcin, osteopontin and BMP2 expressions. In addition, higher MMP-9 and -2 activities were observed. Importantly, the capacity of flavins to trigger osteoblasts differentiation was also reinforced by upregulation of connexin 43, down regulation of caveolin-1 and negative modulation of Notch cascade. In the second analysis, we found that the interaction between Rb and IRb and osteogenic inductors (ascorbic acid and ß-glycerophosphate) significantly affected the osteoblast proliferation, alkaline phosphatase activity, collagen biosynthesis, osteopontin and osteocalcin mRNA expression, MMP-2 and MMP-9 activities and the expression of osteoclastogenesis factors (RANKL and OPG). We also showed that the effects of flavins in osteoblasts cells were independent on flavins antioxidant property. The biological activity of the combination of osteogenic medium with riboflavin and its photoderivatives was associated with the activation of different signaling pathways (AKT, FAK, CaMKII), caspases -8, -9 and -3, and up-regulation and/or stabilization of osteoblastic transcription factors (Runx2 and ß-catenin). This study brought out strong evidences that high concentration of Rb and IRb generates an osteogenic microenvironment through modulating different mediators of signaling pathways, besides of the additive effect of riboflavin and its photoproducts during the ascorbate and ß-glycerophosphateinduced osteoblast differentiation of MC3T3-E1 cells. In summary, this study pointed out the potential application of Rb and its photoproducts in osteoblasts phenotype development and, consequently, it is possible use as an alternative therapeutic adjuvant of osteoporosis.
Doutorado
Bioquimica
Doutor em Biologia Funcional e Molecular
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Reihl, Petra. „Untersuchungen zur Wahrnehmung und zur Aufnahme von Riboflavin in Saccharomyces cerevisiae“. [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981809855.
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Huang, Rongmin. „Kinetics and effects of riboflavin photosensitized degradation on soymilk flavor stability“. Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1138713376.
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Golbach, Jennifer L. „Development of a rapid riboflavin growth-based assay using Lactobacillus rhamnosus“. Texas A&M University, 2005. http://hdl.handle.net/1969.1/3131.
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Riboflavin is an essential part of the human diet. Although the United States
does not have a major problem with a riboflavin deficiency, other regions of the world
do. This is especially true for those regions whose main subsistence is rice. To help
prevent and control riboflavin deficiencies, many cereal grains are now being fortified
with riboflavin. The recommended dietary allowance of riboflavin is 1.1-1.6 mg per day.
This value increases slightly for pregnant women, breast feeding women, and athletes.
Because riboflavin is an essential part of the diet, it is important to ensure that the
minimum requirements for this nutrient are met. By determining the amount of
riboflavin in food products, an accurate estimate of daily riboflavin intake can be
determined. The AOAC (Association of Official Analytical Chemists) approved
microbiological riboflavin assay can be tedious and time consuming. A faster approach
to the riboflavin assay would greatly benefit the food industry. By scaling down the
assay to microtiter plates both, time and materials can be conserved. Use of microtiter
plates would also allow for numerous samples to be assayed simultaneously. The goal
for developing the microtiter plate assay is to obtain results more rapidly while
maintaining the accuracy and precision of the AOAC ( method 940.33I) tube assay.
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Lideberg, Josefine. „Keratitbehandling, antibiotika versus corneal collagen crosslinking (CXL) genom riboflavin och UVA“. Thesis, Linnéuniversitetet, Institutionen för naturvetenskap, NV, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-19711.
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Syfte: Syftet med denna studie var att jämföra antibiotikabehandling med corneal collagen crosslinking (CXL)-behandling genom fotoaktivering av riboflavin vid bakteriell keratit. Att experimentellt undersöka om en viss stam av Pseudomonas aeruginosa kunde infektera cornealt epitel var också en del av studien. Metod: Litteraturstudie samt ett experiment med Pseudomonas aeruginosa och grisögon in vitro. Resultat: Dagens behandling av keratit är initial med antibiotika. I experimentella studier har CXL använts både i kombination med antibiotika och som enskild behandling. Positiva resultat från studier med CXL som behandling mot keratit har rapporterats. Resultatet av det experimentella försöket pekar på att den stam av Pseudomonas aeruginosa som användes i experimentet inte kan penetrera ett intakt epitel. Slutsats: CXL kan bli en viktig och användbar behandlingsform vid keratit, särskilt med tanke på den ökade antibiotikaresistensutvecklingen. Ytterligare forskning på området krävs dock innan metoden kan bli fullt vedertagen. För att kunna fastställa om stammen av Pseudomonas aeruginosa i det aktuella experimentet har virulensfaktorer för att ta sig in i ett oskadat epitel eller inte krävs fler försök.
42
Patterson, Beverley Elaine. „Metabolic studies of riboflavin deficiency in the rat and premature infant“. Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329292.
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Mohnicke, Mandy [Verfasser]. „On the control of riboflavin (vitamin B2) crystal structures / Mandy Mohnicke“. Aachen : Shaker, 2007. http://d-nb.info/1166508757/34.
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Amir, Fatima E. „The Clinical Journey of Patients with Riboflavin Transporter Deficiency Type 2“. University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522312243772827.
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Beena, T. K. „Antigenic Determinants Of Chicken Riboflavin Carrier Protein: Structural And Functional Aspects“. Thesis, Indian Institute of Science, 1994. https://etd.iisc.ac.in/handle/2005/141.
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Investigations detailed in this thesis constitute a part of the continuing programme of research undertaken in our laboratory on the riboflavin carrier protein (RCP) with particular reference to identification and synthesis of neutralizing antigenic determinants, design of relevant epitope mimetics with improved immunogenic characteristics and relationship between their secondary structures and immunological properties.
The riboflavin carrier protein is elaborated as a reproductive stratagem to ensure adequate vitamin deposition in the developing oocyte in the chickens. The protein is scrupulously conserved through evolution in terms of physico chemical and immunological characteristics from fish through birds to mammals, including primates. In rodents and subhuman primates immunization with the heteroantigen viz., chicken egg white RCP leads to functional neutralization of the endogenous maternal protein resulting in curtailment of early pregnancy. Thus, the crucial role of RCP in maintenance of pregnancy is established and the protein identified as a potential candidate vaccine for immimocontraception. Further studies with the reduced and carboxymethylated (RCM) RCP as the immunogen reveal that antibodies induced by RCM-RCP are equally effective in bioneutralization of the endogenous protein. So it can be surmised that the native folded structure of RCP is not obligatory for eliciting bioneutralizing antibodies. In an attempt to identify functionally relevant regions of the protein, a panel of monoclonal antibodies (MAbs) have been raised and characterized. One of the MAbs viz., 6J32Ci2 could bring about early fetal resorp-tion when injected to mice with confirmed pregnancies. These results prompted a detail molecular immunological approach to understand underlying mechanisms. The principal aims of the present investigations include: (1) identification of neutralizing epitopes; (2) synthesis of peptidyl sequences incorporating these determinants; (3) an understanding of the structure, antigenic and immunogenic characteristics of these peptides; (4) correlation of conformational and antigenic characteristics; (5) rational design and synthesis of peptide analogs with greater propensity to assume predicted secondary structures; (6) analysis of conformation dependency of peptide antigens and the importance of such conformation in generating an optimal B-cell response; (7) the efficacy of the antibodies elicited by these Peptide antigens in neutralizing endogenous protein with the ultimate aim of designing synthetic vaccines.
Chapter 1 of this thesis deals with a general introduction summarizing the current status of knowledge regarding the chemistry and biology of RCP as well as synthetic peptides as potential immunogens. Chapter 2 outlines details of the experimental procedures adopted. Chapter 3 describes the results of investigations on the C-terminal fragment (residues 200-219) of cRCR The main consideration in selecting this sequence for the design of a potential peptide-based vaccine relied on the epitopic specificity of the neutralizing MAb 6S2C12. Epitope mapping using the Pepscan method revealed that the monoclonal antibody recognizes a core sequence corresponding to residues 203-210 of the cRCP. A 21-residue synthetic peptide (C-21) comprising this epitope was synthesized and antibodies elicited to the peptide conjugated to two different carriers, namely diphtheria toxoid and purified protein derivative (PPD) for T-cell help. In both active and passive immunoneutralization experiments, the peptide specific neutralizing antibodies interfered with the biological function of the protein and hence either protected from pregnancy or caused early fetal resorption in rodents as well as in sub-human primates. The conforma-tional properties of the peptide in aqueous buffers were analyzed from circular dichroism which revealed the absence of any ordered structure in the native C-21 peptide. Theoretical predictions of secondary structure suggested a propensity for an t*-helical structure for this fragment in the native protein. Therefore, influence of the helix-promoting solvent, vizM 2,2,2,trifluroethanol (TFE) on the C-21 peptide was investigated. Addition of TFE resulted in spectral changes with negative bands at 208 and 222 nm and a positive band at 190 rim which are typical of an a-helix.
To gain more information on the conformational characteristics of this peptide, it was considered worthwhile to stabilize the native peptide in an a-helical conformation based on simple rational design principles. Towards this end, four analogs of the parent peptide were synthesized and helix stabilization was sought to be achieved by introducing either salt bridges or back-bone conformational constraints such as by incorporating a-amino isobutyric acid at appropriate positions. In all the analogs, the core sequence, recognised by the neutralizing MAb 6B2C12 was maintained intact to ensure induction of antibodies capable of recognizing the native protein. CD spectral analysis of the analog peptides indicated that all the engineered peptides had varying degrees of enhanced helicities as compared to the parent peptide. The immunogenicity of each analog was studied by to the relevant peptide-diphtheria toxoid conjugates and analyzing their reactivities with the native protein by direct and competitive ELISA. The results revealed that these engineered conformational analogs axe highly immunogenic eliciting high titers of anti-protein antibodies. The relative affinities of these antibodies to bind cRCP were investigated. The antibodies to peptide analogs had higher affinities for the native protein and a positive correlation was found between the helical content of the peptide antigen in question and the relative affinity of corresponding antibody. The antibodies directed to all the peptide analogs could block the function of RCP resulting in early embryonic resorption when administered to pregnant mice. An interesting pattern of immunological cross-reactivity has been observed with the native and designed peptides. Antibodies raised to constrained helical analogs could bind the C-21 peptide which is structurally flexible. In contrast, the antibodies raised to the flexible native peptide antigen were inefficient in recognizing the structured peptides. The ability of all the peptide antibody to bind the native protein has been interpreted in terms of a conformationally flexible C-terminus region in cRCP.
Chapter 4 details investigations on a 21-residue peptide (N- 21) from the N-terminiis (4-24) of the protein. Selection of this peptidyl sequence relied on theoretical prediction of potential sequential determinants on RCP other than at C-terminus as well as on the outcome of immunoneutralisation experiments using antibodies to egg yolk RCP which lacks the relevant C-terminal determinants. The structure of this peptide in solution was analyzed by two dimensional NMR and CD. NMR experiments revealed the presence of two structured regions in the peptide. Diagnostic nuclear Overhauser effects characteristics of reverse turns or short frayed helical segments over residues 3-9 and 18-21 of the peptide were obtained. CD spectra showed the presence of a strong, negative band at 204 nm over a wide range of solvent conditions, a feature which has been interpreted in terms of a "polyproline Il-like" segment encompassing residues 11-16 which corresponds to an interesting (X-Pro)^ repeat in the N-21 sequence.
Specific antibodies were generated to this peptide as a conjugate with diphtheria toxoid. Administration of the antipeptide antibodies could neutralize the protein in vivo as demonstrated by early embryonic loss in pregnant mice. In limited experiments the antipeptide antibodies showed propensity to protect bonnet monkeys from pregnancy over a few consecutive ovulatory cycles when titres are maintained elevated by periodic boosting. To address the relationship between peptide structures and antigenicity, epitope mapping of this antipeptide antibodies as well- as the polyclonal antibodies to native RCP was undertaken using the Pepscan method. The results reveal that antigenic regions correspond well to conformationally well-defined elements of structure with the polyproline II-like segment being a common antigenic determinant on both the peptide and the native protein. These observations are suggestive of the involvement of both the N and C-terminal regions of RCP in terms of its binding to putative plasma membrane receptors.
46
Beena, T. K. „Antigenic Determinants Of Chicken Riboflavin Carrier Protein: Structural And Functional Aspects“. Thesis, Indian Institute of Science, 1994. http://hdl.handle.net/2005/141.
Der volle Inhalt der QuelleAnnotation:
Investigations detailed in this thesis constitute a part of the continuing programme of research undertaken in our laboratory on the riboflavin carrier protein (RCP) with particular reference to identification and synthesis of neutralizing antigenic determinants, design of relevant epitope mimetics with improved immunogenic characteristics and relationship between their secondary structures and immunological properties.
The riboflavin carrier protein is elaborated as a reproductive stratagem to ensure adequate vitamin deposition in the developing oocyte in the chickens. The protein is scrupulously conserved through evolution in terms of physico chemical and immunological characteristics from fish through birds to mammals, including primates. In rodents and subhuman primates immunization with the heteroantigen viz., chicken egg white RCP leads to functional neutralization of the endogenous maternal protein resulting in curtailment of early pregnancy. Thus, the crucial role of RCP in maintenance of pregnancy is established and the protein identified as a potential candidate vaccine for immimocontraception. Further studies with the reduced and carboxymethylated (RCM) RCP as the immunogen reveal that antibodies induced by RCM-RCP are equally effective in bioneutralization of the endogenous protein. So it can be surmised that the native folded structure of RCP is not obligatory for eliciting bioneutralizing antibodies. In an attempt to identify functionally relevant regions of the protein, a panel of monoclonal antibodies (MAbs) have been raised and characterized. One of the MAbs viz., 6J32Ci2 could bring about early fetal resorp-tion when injected to mice with confirmed pregnancies. These results prompted a detail molecular immunological approach to understand underlying mechanisms. The principal aims of the present investigations include: (1) identification of neutralizing epitopes; (2) synthesis of peptidyl sequences incorporating these determinants; (3) an understanding of the structure, antigenic and immunogenic characteristics of these peptides; (4) correlation of conformational and antigenic characteristics; (5) rational design and synthesis of peptide analogs with greater propensity to assume predicted secondary structures; (6) analysis of conformation dependency of peptide antigens and the importance of such conformation in generating an optimal B-cell response; (7) the efficacy of the antibodies elicited by these Peptide antigens in neutralizing endogenous protein with the ultimate aim of designing synthetic vaccines.
Chapter 1 of this thesis deals with a general introduction summarizing the current status of knowledge regarding the chemistry and biology of RCP as well as synthetic peptides as potential immunogens. Chapter 2 outlines details of the experimental procedures adopted. Chapter 3 describes the results of investigations on the C-terminal fragment (residues 200-219) of cRCR The main consideration in selecting this sequence for the design of a potential peptide-based vaccine relied on the epitopic specificity of the neutralizing MAb 6S2C12. Epitope mapping using the Pepscan method revealed that the monoclonal antibody recognizes a core sequence corresponding to residues 203-210 of the cRCP. A 21-residue synthetic peptide (C-21) comprising this epitope was synthesized and antibodies elicited to the peptide conjugated to two different carriers, namely diphtheria toxoid and purified protein derivative (PPD) for T-cell help. In both active and passive immunoneutralization experiments, the peptide specific neutralizing antibodies interfered with the biological function of the protein and hence either protected from pregnancy or caused early fetal resorption in rodents as well as in sub-human primates. The conforma-tional properties of the peptide in aqueous buffers were analyzed from circular dichroism which revealed the absence of any ordered structure in the native C-21 peptide. Theoretical predictions of secondary structure suggested a propensity for an t*-helical structure for this fragment in the native protein. Therefore, influence of the helix-promoting solvent, vizM 2,2,2,trifluroethanol (TFE) on the C-21 peptide was investigated. Addition of TFE resulted in spectral changes with negative bands at 208 and 222 nm and a positive band at 190 rim which are typical of an a-helix.
To gain more information on the conformational characteristics of this peptide, it was considered worthwhile to stabilize the native peptide in an a-helical conformation based on simple rational design principles. Towards this end, four analogs of the parent peptide were synthesized and helix stabilization was sought to be achieved by introducing either salt bridges or back-bone conformational constraints such as by incorporating a-amino isobutyric acid at appropriate positions. In all the analogs, the core sequence, recognised by the neutralizing MAb 6B2C12 was maintained intact to ensure induction of antibodies capable of recognizing the native protein. CD spectral analysis of the analog peptides indicated that all the engineered peptides had varying degrees of enhanced helicities as compared to the parent peptide. The immunogenicity of each analog was studied by to the relevant peptide-diphtheria toxoid conjugates and analyzing their reactivities with the native protein by direct and competitive ELISA. The results revealed that these engineered conformational analogs axe highly immunogenic eliciting high titers of anti-protein antibodies. The relative affinities of these antibodies to bind cRCP were investigated. The antibodies to peptide analogs had higher affinities for the native protein and a positive correlation was found between the helical content of the peptide antigen in question and the relative affinity of corresponding antibody. The antibodies directed to all the peptide analogs could block the function of RCP resulting in early embryonic resorption when administered to pregnant mice. An interesting pattern of immunological cross-reactivity has been observed with the native and designed peptides. Antibodies raised to constrained helical analogs could bind the C-21 peptide which is structurally flexible. In contrast, the antibodies raised to the flexible native peptide antigen were inefficient in recognizing the structured peptides. The ability of all the peptide antibody to bind the native protein has been interpreted in terms of a conformationally flexible C-terminus region in cRCP.
Chapter 4 details investigations on a 21-residue peptide (N- 21) from the N-terminiis (4-24) of the protein. Selection of this peptidyl sequence relied on theoretical prediction of potential sequential determinants on RCP other than at C-terminus as well as on the outcome of immunoneutralisation experiments using antibodies to egg yolk RCP which lacks the relevant C-terminal determinants. The structure of this peptide in solution was analyzed by two dimensional NMR and CD. NMR experiments revealed the presence of two structured regions in the peptide. Diagnostic nuclear Overhauser effects characteristics of reverse turns or short frayed helical segments over residues 3-9 and 18-21 of the peptide were obtained. CD spectra showed the presence of a strong, negative band at 204 nm over a wide range of solvent conditions, a feature which has been interpreted in terms of a "polyproline Il-like" segment encompassing residues 11-16 which corresponds to an interesting (X-Pro)^ repeat in the N-21 sequence.
Specific antibodies were generated to this peptide as a conjugate with diphtheria toxoid. Administration of the antipeptide antibodies could neutralize the protein in vivo as demonstrated by early embryonic loss in pregnant mice. In limited experiments the antipeptide antibodies showed propensity to protect bonnet monkeys from pregnancy over a few consecutive ovulatory cycles when titres are maintained elevated by periodic boosting. To address the relationship between peptide structures and antigenicity, epitope mapping of this antipeptide antibodies as well- as the polyclonal antibodies to native RCP was undertaken using the Pepscan method. The results reveal that antigenic regions correspond well to conformationally well-defined elements of structure with the polyproline II-like segment being a common antigenic determinant on both the peptide and the native protein. These observations are suggestive of the involvement of both the N and C-terminal regions of RCP in terms of its binding to putative plasma membrane receptors.
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Silvério, Carolina Castelli [UNIFESP]. „Deglutição de parkinsonianos pré e pós riboflavina: queixa, aspectos funcionais e impacto na vida diária“. Universidade Federal de São Paulo (UNIFESP), 2009. http://repositorio.unifesp.br/handle/11600/9297.
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Previous issue date: 2009-01-28Objetivo: verificar a relação entre queixa, aspectos funcionais da deglutição e impacto na qualidade de vida referente à voz e à deglutição, em pacientes portadores da doença de Parkinson, submetidos à administração de riboflavina, no período de um ano. Métodos: participaram do estudo 16 pacientes portadores da Doença de Parkinson, com média de idade de 67,25 anos, média do nível de severidade da doença de II para III e média de tempo de diagnóstico da doença de Parkinson de 3,5 anos. As avaliações videofluoroscópicas da deglutição foram realizadas antes e após um ano da administração de riboflavina e restrição de carne vermelha e de aves. Foram realizadas a análise qualitativa da deglutição, a verificação da presença de queixa com relação à deglutição e aplicação de dois protocolos de qualidade de vida sendo relacionados um com o impacto da alteração vocal, e outro com o impacto da alteração na deglutição. A análise quantitativa compreendeu a realização de medidas de deslocamento do osso hióide, de abertura do esfíncter esofágico superior e de constrição da faringe. Resultados: foram observadas redução da queixa e discreta piora na qualidade de vida relacionada à voz e à deglutição, maior freqüência de ocorrência de deglutição normal, no momento pós-riboflavina. Não foram observadas diferenças significativas entre as medidas quantitativas. Conclusões: Conclui-se neste estudo que: houve melhora, apesar de não significativa, da queixa relacionada à deglutição; não ocorreram pioras significativas na dinâmica da deglutição, com exceção do deslocamento da cartilagem cricóidea na consistência de líquido fino após um ano de estudo; não houve piora com relação ao impacto na qualidade de vida, tanto relacionado à deglutição, quanto ao aspecto vocal; os pacientes que não apresentavam queixas de deglutição no momento pré apresentaram melhora na dinâmica da deglutição, com exceção da constrição da faringe; os pacientes com queixa de deglutição no momento pré apresentaram melhora nos índices de qualidade de vida e na auto-avaliação vocal segundo o QVV, no momento pós.
Objective: to verify the relation between clinical complaint, swallowing functional aspects and the impact on quality of life related to voice and swallowing in patients with Parkinson´s disease submitted to treatment with riboflavin during one year period. Method: sixteen patients with Parkinson´s disease participated in the study; mean age was 67.25 years old, mean degree of disease severity was II to III and mean time of disease diagnosis was 3.5 years. Videofluoroscopic evaluations were performed before and after one year of treatment with riboflavin and restriction diet of read meat and chicken. It were analyzed: qualitative analysis of swallowing, presence of complaints related to swallowing, application of questionnaires related to the impact of voice and swallowing alterations and quantitative analyses of swallowing, which included computerized measurements of hyoid bone and cricoid cartilage displacement, opening of the superior esophageal sphincter and pharyngeal constriction. Results: it were observed: decrease of complaints and slight worsening in quality of life impact regarding voice and swallowing and more frequent normal swallowing post riboflavin; there were no significant changes regarding quantitative measurements. Conclusions: there was a non significant improvement regarding swallowing complaints; it were not observed significant impairments of the swallowing dynamics, except for cricoid cartilage displacement during thin liquid ingestion at the end of the treatment; there was no impairment of quality of life regarding swallowing or voice; patients without swallowing complaints at the beginning of the treatment showed improvement in swallowing dynamics, except for pharyngeal constriction; patients with swallowing complaints at the beginning of the treatment showed improvement regarding quality of life and vocal selfevaluation after treatment.
TEDE
BV UNIFESP: Teses e dissertações
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Shi, Xiaofeng. „Time-Resolved Spectroscopic Studies of the Photochemistry of riboflavin, aromatic N-Oxides and the absolute reactivity of hydroxyl radical“. The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1126795561.
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Hucker, Barry. „The presence and role of Thiamine and Riboflavin in the malting and brewing industries“. Thesis, University of Ballarat, 2013. http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/58647.
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Thiamine and riboflavin vitamers are present in a wide range of foods including beer. They play critical roles in a variety of enzymatic complexes and can promote and maintain metabolism. Currently, the presence and role of these vitamers in the malting and brewing industry has not been widely explored. This research has investigated the effects of various malting and brewing processes on the final thiamine and riboflavin vitamer content of finished beer. In order to achieve this, a highly accurate and reproducible HPLC (spike recovery > 95 %; RSD < 5.0 %) method was developed that allowed the separation of thiamine diphosphate (TDP), thiamine monophosphate (TMP), thiamine, riboflavin 5-phosphate (FMN) and riboflavin in various sample matrices. This method was utilised to determine the vitamer content of various cereals and malts and it was found that malting vastly alters the thiamine content of malted barley, while it has minimal effect on riboflavin content. When malted barley is roasted, all vitamers are rapidly degraded. The mashing process releases the various vitamers into a solution and this release is dependent on temperature and enzymatic activity, while wort boiling significantly reduces the vitamer content of the wort. During fermentation, the thiamine content of wort is quickly utilised within the first six hours of standard fermentations and the uptake of this vitamin is not affected by increases in wort gravity. Meanwhile riboflavin is only poorly utilised during these fermentations. Post-fermentative additives, such as the addition of tannic acid and potassium metabisulphite, negatively affect the vitamin content of the final product while phosphorylated forms of these vitamins are greatly affected by the addition of many post-fermentative processing aids/additives. The presence of both thiamine and riboflavin can enhance the spoilage of beer by known brewery spoilage organisms, and the incorrect storage of bottle-conditioned beer can negatively affect the vitamin and organoleptic properties of the final product. These various steps involved in the production of beer greatly affect the final vitamin content, and this knowledge helps to explain the large variation in the thiamine and riboflavin vitamer content of a survey of 204 commercially available beers. This survey concluded that despite the large variations within particular styles of beer, lagers contain the least amount of thiamine compared to ales, stout/porters and wheat beers. However the average riboflavin content of the tested beers was statistically similar (p = 0.608) across all of the styles. This is due to the limited utilisation of this vitamin during fermentations.Doctor of Philosophy
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Körber, Nicole. „Ein neuer therapeutischer Ansatz zur vorbeugenden Behandlung der pathologischen Myopie - Einfluss des skleralen Riboflavin/Blaulicht Cross-Linkings auf das Augenwachstum junger Kaninchen“. Doctoral thesis, Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-220353.
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Die Arbeit umreißt das Krankheitsbild der Myopie (Kurzsichtigkeit) und deren unterschiedliche Ausprägungen, im Speziellen der progressiven und pathologischen Myopie. Hierbei wird ein Einblick in die Symptomatik, die anatomischen Ursachen und die heutigen medizinischen Interventionen gegeben. Hierdurch wird die Problematik einer zu „weichen“ Sklera (Lederhaut des Auges) und des damit einhergehenden fortschreitenden Augenwachstums deutlich. Im Zentrum der Arbeit steht ein neuer therapeutischer Ansatz zur vorbeugenden Behandlung der pathologischen Myopie; das Riboflavin/Blaulicht Cross-Linking der Sklera des Kaninchenauges.
Dessen Wirkungsweise ermöglicht die biomechanische Versteifung von kollagenem Gewebe. Aus diesem Sachverhalt ergibt sich die Fragestellung der Arbeit: Ist das sklerale Riboflavin/Blaulicht Cross Linking geeignet das Augenwachstum im Tiermodell (junge Kaninchen) verträglich zu hemmen?
Operationsbeeinflussende Parameter wie die Riboflavin-Durchdringungsdauer der Sklera und die sklerale Lichtdurchlässigkeit werden untersucht und für die Optimierung der Operationsmethode herangezogen und diskutiert. Zur Einschätzung des Versuchsansatzes werden die im Methodikteil dargelegten Anwendungen an adulten und jungen Kaninchen/Kaninchenaugen durchgeführt. In Tierversuchen wird die Schadensschwelle in Abhängigkeit der Blaulichtintensität, des Alters und der Pigmentierung untersucht, wobei histologische, immunhistochemische und elektronenmikroskopische Verfahren angewendet werden. Der inhibitorische Einfluss des Riboflavin/Blaulicht Cross-Linkings auf das Augenwachstum kann im Jungtiermodell durch verschiedene metrische Verfahren und MRT-Untersuchungen belegt werden.