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Dissertations / Theses on the topic 'Microbial peptides'

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Published: 4 June 2021
Last updated: 7 September 2023

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1

Kwok, Hoi-shan, and 郭凱珊. "The comparison of biological properties of L- and D-enantiomeric antimicrobial peptides." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206507.

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Antibiotics have been used widely for the treatment of bacterial infections for over half a century. However, the emergence of resistance to antibiotics has aroused public health concern, leading to the development of antimicrobial peptides (AMPs) as potential alternative therapeutic agents against bacterial infections. AMPs are naturally found in many species and have important roles in our innate immune defense systems. AMPs are usually cationic amphipathic peptides with membrane destabilizing property. They have a relatively broad spectrum of antimicrobial activity and pathogens are less likely to develop resistance against AMPs. The major challenge of using AMPs as therapeutic agents is their toxicity towards mammalian cells. The biological stability of AMPs to protease in human body is another concern. To address the latter problem, instead of the naturally occur L-enantiomers, Denantiomeric AMPs were introduced to enhance their stability. This study aimed to test the hypothesis that the D-enantiomeric AMPs are more resistant than the Lenantiomeric AMPs against proteolytic degradation. Three pairs of synthetic D-/LAMPs (D-LAO160-P13/LAO160-P12; D-LAO160-H/LAO160-H; and D-LAK-120-HP13/LAK-120-HP13) were employed to test for their stability when treated with trypsin, serum and gastric fluid, and the samples were analyzed by high performance liquid chromatography (HPLC). Generally, all the D-enantiomeric AMPs were found to be resistant towards proteolysis. Besides, to compare the cytotoxicity of D-/LAMPs, MTT and LDH assays of the D/L-LAK120-HP13 pair were carried out on two different cell lines, A549 cells (human lung adenocarcinoma epithelial cells) and RAW264.7 cells (mouse macrophage cells). Significant difference in cytotoxicity of D-LAK120-HP13 and LAK120-HP13 on RAW264.7 cells were obtained from MTT assay, but not in LDH assays or on A549 cells. Further analysis has to be done to validate the findings obtained from this research.
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Pharmacology and Pharmacy
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Master of Medical Sciences
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2

Zhou, Yu. "Studies on anti-microbial peptides and other bioactive peptides from skin secretions of phyllomedusine frogs." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534594.

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3

Chia, Brian Cheng San. "Amphibian antimicrobial peptides : their structures and mechanisms of action : a thesis presented for the degree of Doctor of Philosophy." Title page, contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phc532.pdf.

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Copy of author's previously published works inserted. Bibliography: leaves 183-220. Three antimicrobial peptides, maculatin 1.1, uperin 3.6 and caerin 4.1 have been isolated from the respective skin glands of the Australian amphibians Litoria genimaculata, Uperoleia mjobergii and Litoria caerulea. To gain a deeper insight into their mechanisms of action, three dimensional structural studies have been conducted using circular dichroism, two-dimensional nuclear resonance and computer modelling techniques. The role of central flexibility within antibiotic peptides in their interaction with bacterial membranes is also discussed.
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Chen, Heru. "Preparation and biological evaluation of the loloatins and their analogues /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202002%20CHEN.

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5

Wilson, Sarah, and n/a. "Vaccine peptide delivery by virus particles." University of Otago. Department of Microbiology & Immunology, 2007. http://adt.otago.ac.nz./public/adt-NZDU20080131.161222.

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Vaccination with immunogenic peptides offers a safe and specific way of inducing protection against pathogens, however as of yet there are no peptide-based vaccines available. The limitations on the therapeutic use of peptides are due to their poor immunogenicity and short life span in vivo. Peptide delivery systems act to circumvent these issues. The aims of this research were to investigate the ability of virus-like particles (VLP) from Rabbit haemmorhagic disease virus (RHDV) to deliver immunogenic peptides, to characterize the immune response to these particles, and to investigate whether baculovirus could also act as a delivery system. The vaccine peptides HAT (representing a T helper cell epitope) and HAB (representing the major B cell epitope) derived from the haemagglutinin antigen of influenza virus A/PR/8/34 were used as a model to investigate the ability of these virus particles to act as delivery vehicles to the immune system. A scheme for the production and purification of RHDV VLP was established. Expression of the capsid protein from RHDV in a serum-free recombinant baculovirus system using suspension cultures of up to 200 ml, and separation by isopycnic centrifugation on cesium chloride gradients led to high yields of purified RHDV VLP. Up to 20 mg of pure VLP could be obtained from an 800 ml culture of insect cells infected with recombinant baculovirus. In vitro testing revealed that RHDV VLP carrying the peptide HAT as a genetic fusion were processed by dendritic cells (DC), and that this peptide could be presented to induce activation of T cells. However, the purified RHDV VLP alone were not able to induce significant upregulation of cell activation markers CD40, CD86, and CD80. A preliminary in vivo study revealed that when RHDV VLP carrying the HAT peptide were delivered by an intraperitoneal injection in the absence of adjuvant, the immune response to the peptide was weak, therefore the route of delivery and the use of immune adjuvants with the VLP were optimised. Five different routes of delivery and two different immune adjuvants were compared. VLP were delivered through subcutaneous, intraperitoneal, transcutaneous, intramuscular and intranasal routes. Delivery of the VLP through each of these routes resulted in potent serum antibody responses. However, the strongest antibody responses were elicited when the VLP were delivered through the intraperitoneal or intranasal routes. Of these two routes, intranasal delivery gave the best mucosal responses at the lung surface, and was therefore chosen as the route of delivery for subsequent trials. CpG DNA and the wild-type baculovirus Autographa californica nucleopolyhedrovirus (AcMNPV) were tested as adjuvants for the RHDV VLP. These two adjuvants gave similar results, both acting to enhance a T[H]1 type response against the VLP, characterized by significantly increased levels of serum IgG2a and enhanced IFN-γ production. Two approaches were then tested: using the RHDV VLP as a peptide carrier with a CpG adjuvant, and using baculovirus particles directly as self-adjuvanting carriers for vaccine peptides. HAT and HAB peptides were chemically coupled to RHDV VLP. Mice that were vaccinated with these VLP mixed with a CpG adjuvant were able to raise low levels of specific antibody in the serum against influenza, and specific IgA against influenza was detected in the lung. These results indicated that, though the immune responses raised were modest, the RHDV VLP was able to deliver the vaccine peptides to the immune system. HAT and HAB peptides were chemically coupled to baculovirus particles. When mice were immunized with the baculovirus carrying the vaccine peptides, they raised significant levels of IgG1 (p<0.001) and IgG2a (p<0.05) against influenza in the serum, when compared to peptide delivered alone. A significant level of influenza-specific IgA was also detected in the lung at 10 ng/ml in the mice that received the baculovirus coupled with peptide. Analysis of splenocyte cytokines showed that these mice also responded to restimulation with IFN-γ production at around 100 pg/ml. This research revealed that RHDV VLP are able to act as carriers for vaccine peptides, however there are some limitations to their use with the HAT and HAB model peptides. It also showed that baculovirus can be rapidly modified to carry vaccine peptides by chemical conjugation, and that these peptides can be delivered to induce specific systemic and mucosal immunity, raising both B cell and cell mediated responses. Both virus particles have potential as components for new strategies for vaccination.
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Wabnitz, Paul Andrew. "Chemistry and medical implications of novel amphibian peptides : a thesis submitted for the degree of Doctor of Philosophy /." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phw112.pdf.

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7

Brewster, Rachel Elizabeth. "Synthesis of small molecules with specific function : I. Peptidocalix[4]arenes as molecular receptors ; II. Towards the total synthesis of (-)-Dihydroguaiaretic acid." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131103/unrestricted/brewster%5Frachel%5Fe%5F200405%5Fphd.pdf.

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8

Limoli, Dominique H. "Investigating the host and microbial determinants of Pseudomonas aeruginosa mucoid conversion." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406024226.

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9

Lu, Qian. "Expression and regulation of human [beta]-defensins in gingival epithelia." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36613708.

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10

Besse, Alison. "Interactions microbiennes et adaptations en milieu extrême : peptides antimicrobiens d’archées halophiles." Thesis, Paris, Muséum national d'histoire naturelle, 2016. http://www.theses.fr/2016MNHN0007/document.

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Les archées halophiles sont des procaryotes vivant dans des conditions d’extrême salinité. Ces micro-organismes colonisent les environnements hypersalins et synthétisent des peptides antimicrobiens appelés halocines, qui pourraient leur conférer un avantage sélectif sur leurs compétiteurs. Parmi les peptides antimicrobiens d’archées halophiles décrits, on distingue l’halocine C8, initialement purifiée à partir de la souche halophile Natrinema sp. AS7092. Ce travail de thèse a permis de montrer que la production d’halocine C8 était conservée chez plusieurs archées halophiles appartenant aux genres : Natrinema, Haloterrigena, Haloferax et Halobacterium. Une activité antimicrobienne associée des particules supérieures à 100 kDa non infectieuses suggère que l’halocine C8 pourrait être localisée dans des vésicules membranaires. Ce travail présente des résultats qui déboucheront sur une meilleure compréhension des compétitions microbiennes dans les environnements hypersalins et du rôle écologique des halocines
Halophilic archaea are prokaryotes living in extremely high salinity conditions. Those microorganisms thrive in hypersaline environments and produce antimicrobial peptides named halocins, which may confer them a selective advantage over competitors. Among the known antimicrobial peptides produced by halophilic archaea, halocin C8 had been initially purified from the halophilic strain Natrinema sp. AS7092. This work demonstrates that halocin C8 production is conserved among several halophilic archaea belonging to genera Natrinema, Haloterrigena, Haloferax and Halobacterium. An antimicrobial activity has been associated with non-infectious particles larger than 100 kDa, suggesting that halocin C8 could be localized in membrane vesicles. Results obtained from this work will lead to a better understanding of microbial competitions arising in hypersaline environments and the ecological role of halocins
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11

Morgan, Joanne. "Screening, isolation and characterisation of antimicrobial/antifungal peptides produced by lactic acid bacteria isolated from wine." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53582.

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Thesis (MSc)--Stellenbosch University, 2003.
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ENGLISH ABSTRACT: Winemaking is an age-old tradition that dates back to as early as 6000 BC. In our modern era there are several insects and microorganisms that pose a threat to the grapevine, the environment and the final wine product. Farmers and winemakers are becoming aware of the threat and the fight against disease, spoilage and/or pathogenic microorganisms is on the rise. Currently, the natural environment is being altered through rural developments, pollution and disaster, which in turn is responsible for altering the natural micro flora. The result is a harsh battle between man and microorganism. The weapon used often against microorganisms is chemical preservatives, such as sulphur dioxide. These chemical preservatives change the nutritional value, quality and wholesomeness of the wine. Chemical preservatives suppress the quality of the wine with a reduction in wine consumption by the consumers. Until the 18th century, wine was regarded as a safe drink and prescribed by doctors. In the zo" century alcohol consumption became the focus point of some health campaigners. Medical science restored the good name of wine in the 1990s when it came to light that moderate red wine consumption may aid in preventing heart disease and assist in stress management. The only drawback that lowers consumption levels is the use of chemical preservatives. It is of utmost importance to place the focus on health issues and the development of natural preservation methods that are environmentally friendly and contributes to the overall wholesomeness of the wine. Due to these demands, the scientific community placed the focus of research projects on the development and enhancement of biopreservation methods, in order to minimise chemical preservation use. One of the most promising biocontrol agents is bacteriocins. These proteinaceous molecules produced by various lactic acid bacteria exert antimicrobial activity towards closely related organism. Research has shown that bacteriocins may aid in the prevention of wine-spoilage and enhance natural preservation techniques. Most of the research on biopreservation in food and beverages has been performed on the bacteriocins of LAB. No evidence could be found that indicated bacteriocin production by wine isolated LAB in South Africa. This study is therefore, of utmost importance and is considered to be novel pioneering work for the South African wine industry. The main objective of this study was to screen wine isolated LAB for the production of antimicrobial and/or antifungal compounds. This was followed by the isolation and characterisation of the produced bacteriocins. This study forms part of a greater project that focuses on wine preservation, under the auspices of the Institute for Wine Biotechnology.The research results in this study indicated the production of bacteriocins by wine isolated LAB of South African origin. It was found that numerous isolates exerted antimicrobial activity towards other wine associated LAB. The most predominant species that gave the highest activity was Lactobacillus brevis and Lactobacillus paracasei. Experimental results indicated that the bacteriocins produced by these two species were thermo-stable and active over a wide pH range, including the temperatures and pH values that reign in the South African wine environment. The antimicrobial activity was lost after treatment with proteolytic enzymes, such as proteinase K and lysozyme. The size, production and growth kinetic curves of the bacteriocins under investigation showed similar results that are comparable to other findings in the literature. Antifungal activity was detected against Botryfis cinerea that indicated limited inhibitory activity towards spore germination, but had no effect on hyphal growth. This study provides novel information regarding bacteriocin production by LAB isolated from the South African wine industry. The results indicate the suitability of these bacteriocins as possible biopreservatives in the wine environment. The proposed results obtained in this study will aid in the development of bacteriocinproducing, tailored made wine yeast or LAB that may in future, play vital roles in the winemaking process.
AFRIKAANSE OPSOMMING: Wynmaak is 'n eeu oue tradisie wat terugdateer tot so vroeg soos 6000 jaar v.C. In ons moderne eeu is daar verskeie insekte en mikro-organismes wat In bedreiging vir die wingerdstok, asook die omgewing en die finale wynproduk inhou. Boere en wynmakers word al hoe meer bewus van hierdie bedreiging, terwyl die stryd teen siektes, bederf en/of patogene mikro-organismes ook aan die toeneem is. Tans word die natuurlike omgewing deur landelike ontwikkeling, besoedeling en natuurlike rampe verander, wat op sy beurt weer verantwoordelik is vir die verandering van mikroflora. Die gevolg is 'n harde stryd tussen die mens en mikro-organismes. Die wapen wat gereeld ingespan word in die stryd teen mikro-organismes, is chemiese preserveermiddels, soos swaweidioksied. Hierdie chemiese preserveermiddels verander die voedingswaarde, kwaliteit en die voedsaamheid van die wyn. Dit onderdruk ook die gehalte van wyn, wat meebring dat minder wyn deur die verbruiker gedrink word. Tot en met die agtiende eeu is wyn deur dokters as 'n veilige drankie voorgeskryf. In die twintigste eeu het alkoholverbruik die fokuspunt van gesondheidskamvegters geword. In die 1990's het die mediese wetenskap wyn se goeie naam in ere herstel toe dit aan die lig gekom het dat In matige verbruik van rooiwyn moontlik hartsiektes kan voorkom en help om stres te beheer. Die enigste nadelige faktor wat verbruikersvlakke verlaag, is die gebruik van chemiese preserveermiddels. Dit is uiters noodsaaklik om die fokus op gesondheidskwessies te plaas en die ontwikkeling van natuurlike preserveermetodes wat omgewingsvriendelik is en tot die algehele voedsaamheid van wyn bydra. As gevolg van hierdie eise het wetenskaplikes die fokus geplaas op navorsingsprojekte vir die ontwikkeling en verbetering van biopreserveringsmetodes met die doelom die gebruik van chemiese preserveermiddels te verminder. Een van die belowendste biokontrolemiddels is bakteriosiene. Hierdie proteïenagtige molekule word deur verskeie melksuurbakterieë vervaardig en oefen anti-mikrobiese aktiwiteit teenoor nabyverwante organismes uit. Navorsing het getoon dat bakteriosiene moontlik kan help in die voorkoming van wynbederf en natuurlike preserveertegnieke kan verbeter. Die meeste van die navorsing op biopreservering in voedsel en drank is op die bakteriosiene van melksuurbakterieë uitgevoer. Geen bewys kon gevind word in Suid Afrika wat bakteriosienproduksie deur wyn-geïsoleerde melksuurbakterieë aangedui het nie. Hierdie studie is daarom baie belangrik en word as baanbreker werk vir die Suid Afrikaanse wynbedryf beskou. Die hoofdoel van hierdie studie was om wyn-geïsoleerde melksuurbakterieë vir die produksie van anti-mikrobiese en/of anti-fungiese substanse te toets. Dit is gevolg deur die isolasie en karakterisering van die geproduseerde bakteriosiene. Hierdie studie maak deel uit van 'n groter projek wat fokus op wynpreservering en wat onder leiding van die Instituut van Wynbiotegnologie uitgevoer word. Navorsingsresultate van hierdie studie dui op die produksie van bakteriosiene deur wyn-geïsoleerde melksuurbakterieë van Suid Afrikaanse oorsrong. Daar is gevind dat verskeie isolate anti-mikrobiese aktiwiteit teenoor ander wynverwante malksuurbakterieë uitgeoefen het. Die oorheersende spesie wat die hoogste aktiwiteit getoon het, was Lactobacillus brevis en Lactobacillus paracasei. Eksperimentele uitslae dui daarop dat die bakteriosiene wat deur hierdie twee spesies geproduseer word, termostabiel en aktief is oor 'n wye pH reeks, insluitende die temperature en pH-waardes wat in die Suid Afrikaanse wynomgewing voorkom. Die anti-mikrobiese aktiwiteit het verlore gegaan na behandeling met proteolitiese ensieme soos proteïnase K. Die groote, produksie en groeikinetika kurwes van die bakteriosiene wat ondersoek is, toon vergelykbare resultate met ander bevindings in die literatuur. Anti-fungiese aktiwiteit is opgemerk teen Botrytis cinerea, wat beperkte inhiberende aktiwiteit ten opsigte van spoorontkieming aangedui het, maar geen effek op hifegroei gehad nie. Hierdie studie verskaf nuwe inligting aangaande bakteriosienproduksie deur melksuurbakterieë wat van die Suid Afrikaanse wynomgewing geïsoleer is. Die resultate dui op die geskiktheid van hierdie bakteriosiene as moontlike biopreserveermiddels in die wynbedryf. Die voorgestelde resultate deur hierdie studie verkry sal help in die ontwikkeling van bakteriosien produserende, spesifiek vervaardigse wyngis of melksuurbakterieë, wat in die toekoms 'n baie belangrike rol in die wynmaakproses sal speel.
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12

Lu, Qian, and 陸茜. "Expression and regulation of human {221}-defensins in gingival epithelia." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B36613708.

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13

Holroyd, Dale. "Atomic force microscopy : a novel tool for the analysis of the mechanism of action of antimicrobial peptides on target membranes." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53306.

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Thesis (MSc)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: Nanoscale visualisation of live cells and cellular components under physiological conditions has long been a goal in microscopy. The objective of this study was to validate the use of Atomic Force Microscopy (AFM) as a new tool in unravelling the mysteries of antimicrobial peptide mechanism of action. Using the simplest AFM imaging technique, we were able to analyse the influence of haemolytic melittin and anti-bacterial magainin 2 on different target membranes at nanometer resolution, without using fixing agents. First, magainin 2 was synthesised and purified by gel permeation chromatography and high performance liquid chromatography (HPLC). The purity of magainin 2 and melittin, isolated from bee venom (Sigma-Aldrich), was verified with electro spray ionisation mass spectrometry (ESI-MS). Second, dose-response experiments were used to determine the optimum peptide/target cell ratio that would allow interaction with the membrane without causing lysis. Third, peptide/target-cell samples were placed on silica plates and visualised using contact mode AFM. Images obtained of the cells before and after peptide treatment, showed distinct changes in cell membrane surface topology. We observed grooves, lesions, membrane collapse and vesiculation depending on the concentration, type of peptide and target-cell used, allowing us to make conclusions regarding the mechanism of action of melittin and magainin 2. In comparison with model membrane studies, our AFM results show that a peptide can function by more than one mechanism of action depending on the structural composition of the membrane, which appears to have specific segregated lateral organisation. Magainin 2 (non-toxic) selectively targets cell membranes using different mechanisms of action. In this way it can lyse bacterial membranes (anti-bacterial agent) using one mechanism, while using another mechanism to interact with mammalian cells at physiological concentrations, without destroying them. In contrast, melittin (toxic) is non-selective, and uses the same mechanism of interaction with bacterial and mammalian cells. In conclusion, we propose a new holistic model for the mechanism of action of antimicrobial peptides.
AFRIKAANSE OPSOMMING: Nanoskaal visualiseering van lewende selle en sellulêre komponente onder fisiologiese toestande is al 'n geruime tyd 'n mikpunt in mikroskopie. Die doel van hierdie studie was om antimikrobiese peptiede se meganisme van werking op teikenselle op nanoskaalvlak met AFM te visualiseer. Sonder om fikseermiddels by te voeg, het ons die eenvoudigste AFM tegniek gebruik om die effek van hemolitiese melittien en anti-bakteriële magainin 2 op verskillende teikenselle, in nanometer resolusie, waar te neem. Eerstens is Magainin 2 gesintesiseer en gesuiwer met behulp van gelpermeasie chromatografie en hoë doeltreffenheid vloeistof chromatografie (HPLC). Die suiwerheid van magainin 2 en kommersiële bye gif melittien, is bevestig met behulp van elektrosproei-ionisasie massaspektrometrie (ESI-MS). Tweedens, is dosis-respons eksperimente gebruik om die optimale peptied/teikensel verhouding te bepaal voordat membraanliese plaasvind. Derdens, is peptied/teikensel monsters op silika plate gevisualiseer met gebruik van kontak AFM. Die beelde van die selle, voor en na peptied behandeling, het duidelike veranderinge in seltopologie getoon. Ons het groewe, letsels, membraaninstorting en vesikulasie, afhangende van die konsentrasie peptied en teikensel gebruik, waargeneem. Dit het ons toegelaat om tot gevolgtrekkings te kom aangaande die meganisme van werking van melittien en magainin 2. In ooreenstemming met model membraan studies, het ons AFM resultate gewys dat 'n peptied veelvoudige meganismes van werking kan hê, afhangend van die strukturele samestelling van die membraan, wat klaarblyklik laterale segregasie toon. Magainin 2 (nie-giftig) is selektief ten opsigte van teikenselle omdat dit gebruik maak van verskillende meganismes van werking op bakteriële en soogdier selle. In teenstelling is melittien (giftig) nie-selektief, en gebruik dieselfde meganisme van werking op bakteriële en soogdierselle. Ten slotte, stel ons 'n nuwe model vir die meganisme van werking voor.
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Miranda, Ceres Maciel de. "Expressão de microplusina em Aedes aegypti: avaliação do efeito sobre Plasmodium gallinaceum." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/42/42135/tde-04082011-091317/.

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A transmissão de parasitas da malária por mosquitos vetores é dependente do desenvolvimento bem sucedido das formas infectantes de Plasmodium sp., especialmente os esporozoítas, que são as formas que infectam o hospedeiro vertebrado. A manipulação genética de mosquitos vetores tem sido uma estratégia alternativa na tentativa de controle da malária. Um componente extremamente importante desta estratégia é a escolha de uma molécula efetora capaz de reduzir a transmissão do patógeno. Microplusina é um peptídeo antimicrobiano rico em cisteína, originalmente descrito como um componente antimicrobiano da hemolinfa e dos ovos de carrapato bovino Rhipicephalus (Boophilus) microplus. Testes anteriores utilizando o modelo experimental mosquito Aedes aegypti infectado por Plasmodium gallinaceum mostraram que a microplusina é altamente tóxico para esporozoítas de Plasmodium gallinaceum em concentração relativamente baixa, sem apresentar toxicidade aos mosquitos vetores Aedes aegypti. Nosso objetivo foi analisar a expressão da microplusina e seu efeito na infecção de P. gallinaceum em mosquitos transgênicos. Obtivemos quatro linhagens através da integração de um transgene contendo a região promotora do gene da vitelogenina de Ae. aegypti, peptídeo sinal maltase-like I de Ae. aegypti e a sequência codificadora da microplusina (PMOS [3xP3-EGFP-AeVg Micro]). A atividade anti esporozoítas da microplusina expressa pelos mosquitos transgênicos mostrou diferença significante as linhagens. O desenho de novas moléculas utilizando como molde moléculas efetoras existentes e testadas, possibilitará o aperfeiçoamento da expressão de genes exógenos em mosquitos transgênicos, tornando-os refratários ao parasita.
Transmission of malaria parasites by mosquito vectors is dependent on the successful development of Plasmodium sp. infective forms, particularly the sporozoites, which are the forms that enter the vertebrate host. The genetic manipulation of mosquito vectors has been a strategy for malaria control. An extremely important component of this strategy is the effector molecule of choice which reduces parasite transmission. Microplusin is a cysteine-rich antimicrobial peptide originally described as an hemolymph and eggs antimicrobial component of the cattle tick Boophilus microplus. Previous tests using the experimental model Plasmodium gallinaceum infected Aedes aegypti showed that microplusin is highly toxic to P. gallinaceum sporozoites in relatively low concentration, without showing toxicity to the mosquito vector A. aegypti. Our goal was to analyze transgenic mosquitoes expressing microplusin and its effect on infection of P. gallinaceum. We obtained four lines through the integration of transgene that containing the promoter region of the A. aegypti vitelogenin gene, the maltase-like I signal peptide of A. aegypti and microplusin coding sequence (pMos[3xP3-EGFPAeVg-Micro]). The activity anti sporozoites microplusin expressed by transgenic mosquitoes showed significant differences between strains. The design of effector molecules using information from existing and tested molecules as template will enable the improvement of the expression of foreign genes in transgenic mosquitoes, making them resistant to the parasite.
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NASH, JAMES ANDREW. "THE PEPTIDOGLYCAN-DEGRADING PROPERTY OF LYSOZYME IS NOT REQUIRED FOR BACTERICIDAL ACTIVITY, IN VIVO." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1135957476.

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16

Rizk, Ziad. "Impact and identification of inhibitory peptides released by Saccharomyces cerevisiae on the malolactic fermentation." Phd thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/19390/1/Ziad_Rizk.pdf.

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The production of most red wines and certain white and sparkling wine styles requires two consecutive fermentation steps. The first one is the alcoholic fermentation (AF) and is carried out mainly by Saccharomyces cerevisiae. At the end of the AF, the wines undergo malolactic fermentation (MLF) carried out mainly by Oenococcus oeni. However, the MLF is often difficult to trigger and accomplish because of the individual or synergistic antibacterial activity of several physical chemical wine parameters and yeast inhibitory metabolites. In this context, the study of the interactions that may occur between specific strains of yeasts and bacteria is important for choosing the adequate strain combination and inoculation strategy. In the present work, S. cerevisiae strain D strongly inhibited O. oeni strain X during sequential fermentations performed in synthetic grape juice (SGJ) media whereas S. cerevisiae strain A stimulated it. Protease and heat treatments of the SGJ media fermented by strain D showed the protein nature of the yeast inhibitory metabolites. Fractionation by ultrafiltration of the same media revealed that an extracellular peptidic fraction of 5-10 kDa was responsible for the inhibition. It was gradually released during AF and reached its highest concentration at late stages of the stationary phase. The MLF inhibition was maintained in natural grape juices and grape musts (Cabernet-Sauvignon and Syrah) presenting low and high phenolic contents. Therefore, the activity of the inhibitory peptides was not affected by grape phenolic compounds. The 5-10 kDa fraction was tested in vitro on cell-free bacterial cytosolic extracts containing the malolactic enzyme in a pH range between 3.5 and 6.7. Results showed that it was able to directly inhibit the malolactic enzyme activity with an increasing inhibitory kinetic correlated to the AF time at which it was collected. The 5-10 kDa peptidic fraction of the 60-80 % ammonium sulfate precipitate was submitted to analyses by both anionic and cationic exchange chromatography (AEXC and CEXC). Eluates recuperated with 0.5 M NaCl from both AEXC and CEXC contained inhibitory peptides and were further migrated by SDS-PAGE. The bands of interest were excised and sequenced by LC1D-nanoESI-LTQ-Orbitrap. Results gave 12 different peptidic fractions that may have worked synergistically. 2 GAPDH fragments of 0.9 and 1.373 kDa having a pI of 9.074 and a Wtm2p fragment of 2.42 kDa having a pI of 3.35 were involved in the MLF inhibition.
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17

Wang, Peng. "Studies on E. Coli Membrane Protein Biogenesis: Mechanism of Signal Peptide Peptidase A and the Influence of YiDC Depletion on Cellular Processes." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=osu1243982038.

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18

Hubert, Marie. "Structure de mycotoxines et d'analogues- recherche de leurs métabolites chez un insecte hôte." Rouen, 1998. http://www.theses.fr/1998ROUES037.

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Dans l'optique d'utiliser les mycotoxines en tant que bioinsecticides potentiels de nouvelle génération, nous nous sommes intéressés à celles de deux champignons entomopathogènes, Metarhizium anisopliae et Paecilomyces farinosus. Celles de M. Anisopliae, les destruxines (DTXs), sont des cyclohexadepsipeptides connus depuis plusieurs décennies. Sur le plan structural, une systématique de fragmentation de ces composés a été mise au point par PFAB/MS/Linked Scan. Au niveau biologique, nous avons complété les études sur le comportement in vivo des destruxines. Les métabolites des DTXs A et E, destruxines les plus toxiques et les plus abondamment produites par M. Anisopliae, avaient été mis en évidence chez un insecte modèle, le criquet Locusta migratoria. Ici, nous les avons étudies à l'aide de deux techniques analytiques complémentaires, la spectrométrie de masse et l'HPLC, dans l'hémolymphe d'un insecte ciblé, les larves du lépidoptère Galleria mellonella. Ainsi, pour la DTXE, un processus de détoxication identique à celui observé chez le criquet a été décelé chez G. Mellonella : hydrolyse (DEDiol), conjugaison par le glutathion (DESG) puis métabolisation ultérieure en conjugué cystéinique (DESCys) et enfin conjugaison en dérivé phosphate et/ou sulfate (DEDiolP ou DEDiolS). En revanche, pour la DTXA, le processus se révèle différent selon les deux insectes. Chez le criquet, la DTXA se métabolise en peptide linéaire, tandis que chez G. Mellonella, elle mène principalement au DEDiolP, en passant vraisemblablement par la DTXE et la DTXEDiol. En outre, le comportement in vivo d'analogues synthétiques des destruxines a été étudié. C'est d'ailleurs la première fois qu'une telle étude est menée. Pour ces deux diastéréoisomères, dont l'un est actif et l'autre inactif, un processus de métabolisation identique a été mis en évidence. Il s'agit de la formation du peptide linéaire résultant d'une hydrolyse au niveau de la liaison lactone. Cependant, le processus d'excrétion semble différent. En effet, l'isomère inactif disparaît alors que l'actif est toujours présent après 24h d'incubation. En ce qui concerne les toxines de P. Farinosus souche KVL420, elles n'ont malheureusement pu être caracterisées. Il s'agit de molécules de petites tailles, très hydrophiles. Aucune méthode de séparation adéquate et préalable à des analyses par spectrométrie de masse et RMN n'a pu être determinée à ce jour.
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19

Leite, Suzan Blima Paulino. "Efluentes do processamento de Minced de tilápia reaproveitados como coprodutos com atividade antioxidante e para uso como meio de cultura em bioprocessos." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/64/64135/tde-14072016-142959/.

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A água residual do processamento do Minced de tilápia (Oreochromis niloticus) é descartada sem qualquer aproveitamento, constituindo um efluente de potencial impacto ao ambiente. O objetivo desse estudo foi avaliar este efluente, caracterizar sua fração proteica, verificar seu potencial antioxidante e sua eficiência como meio de cultura para o crescimento microbiano. A carne mecanicamente separada (CMS) de tilápia foi submetida à operação de clarificação em água destilada a 10ºC, na proporção 1:3, processo que se constituiu em homogeneização por 3 min, repouso por 3 min, sendo o Minced acondicionado e prensado em tecido de algodão esterilizado para drenagem da água residual. O efluente gerado pela etapa de lavagem do Minced apresentou 8854,5 mgO2/L de DQO e 4656,88 mgO2/L de DBO, valores considerados elevados dentre os padrões de qualidade, devido ao alto teor de matéria orgânica. O efluente foi submetido à centrifugação e a fração aquosa foi liofilizada, sendo designada de peptona e submetida à análise eletroforética que apresentou maior concentração de proteínas na faixa de 47-60 kDa. A atividade antioxidante foi avaliada em diferentes concentrações utilizando ensaios in vitro como o método do radical 2,2-azinobis-(3-etilbenzotiazoline-6-ácido sulfônico) (ABTS) e 1,1-difenil-2-picrilhidrazil (DPPH), sendo que, em ambos, o aumento da atividade antioxidante acompanhou a concentração. Com destaque para o extrato 15 mg/ml que propiciou 46,23% de inibição do radical ABTS, e 83,22% em DPPH. Em relação ao teste de efetividade, foram comparadas peptonas comerciais e a peptona da água residual liofilizada, sendo avaliada a curva de crescimento pela densidade óptica, produção de biomassa e detecção por plaqueamento da Escherichia coli e Staphylococcus aureus. A performance obtida nas peptonas da água residual foram superiores às comerciais, evidenciando o vantajoso reuso desse efluente como coproduto destinado ao cultivo de microrganismos. O desempenho do peptídeo residual permite que se recomende o seu uso por parte das empresas que buscam a ecoeficiência
The wastewater of minced tilapia (Oreochromis niloticus) processing is discarded without any use, constituting a effluent of potential impact on the environment. The aim of this study was to evaluate this effluent, characterize its protein fraction, verify its antioxidant potential and its efficiency as a culture medium for microbial growth. Mechanically separated meat (CMS) tilapia was submitted to clarification operation in distilled water at 10°C in a 1:3 ratio, a process that constitutes homogenizing for 3 minutes, rest for 3 minutes, and the minced packed and compressed in a sterilized cotton fabric for drainage of wastewater. The effluent generated by the minced washing step showed 8854.5 mgO2 / L of COD and 4656.88 mgO2 / L BOD, values considered among high quality standards due to the high content of organic matter. The effluent was subjected to centrifugation and the aqueous fraction was lyophilized, and designated peptone and subjected to electrophoresis analysis showed a higher concentration of proteins in the 47-60 kDa range. The antioxidant activity was evaluated at different concentrations using in vitro assays such as radical method 2,2-azinobis- (3-sulphonic acid 6-etilbenzotiazoline) (ABTS), and 1,1-diphenyl-2-picrylhydrazyl (DPPH), wherein, in both the increased antioxidant activity followed the concentration. Especially the extract 15 mg / ml which provided 46.23% inhibition of ABTS radical, and 83.22% in DPPH. Regarding the effectiveness test, they were compared to commercial peptones and peptone lyophilized wastewater, assessing growth curves by optical density biomass production by plating and detection of Escherichia coli and Staphylococcus aureus. The performance achieved in peptones wastewater were higher than commercial, showing the beneficial reuse of the effluent as a co-product intended for microorganisms cultivation. The performance of the residual peptide allows recommending its use by businesses seeking eco-efficiency
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Tayou, Junior Kom. "Requirement of ßDELSEED-Motif of Escherichia coli F1FO ATP Synthase in Antimicrobial Peptide Binding." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etd/1260.

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F1FO ATP synthase is a membrane bound enzyme capable of synthesizing and hydrolyzing ATP. Lately, α-helical cationic peptides such as melittin and melittin related peptide (MRP) were shown to inhibit E. coli ATP synthase. The proposed but unconfirmed site of inhibition is βDELSEED-motif formed by the residues 380-386, located at the interface of α/β subunit of ATP synthase. This project was a mutagenic analysis of βDELSEED-motif residues to understand the binding mechanism and mode of action of peptide inhibitors. The study addressed 2 main questions: Are the antibacterial/anticancer effects of these peptides related to their inhibitory action on ATP synthase through interaction with the βDELSEED-motif? If so, which amino acid residues play critical role in peptide binding? The findings demonstrated that the βDELSEED-motif is the binding site of the above peptides on ATP synthase and Glutamate residues are more important in peptide binding than the Aspartate residues.
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21

Winkle, Sean M., Andrea L. Throop, and Melissa M. Herbst-Kralovetz. "IL-36γ Augments Host Defense and Immune Responses in Human Female Reproductive Tract Epithelial Cells." FRONTIERS MEDIA SA, 2016. http://hdl.handle.net/10150/617371.

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IL-36 gamma is a proinflamatory cytokine which belongs to the IL-1 family of cytokines. It is expressed in the skin and by epithelial cells (ECs) lining lung and gut tissue. We used human 3-D organotypic cells, that recapitulate either in vivo human vaginal or cervical tissue, to explore the possible role of IL-36 gamma in host defense against pathogens in the human female reproductive tract (FRT). EC were exposed to compounds derived from virus or bacterial sources and induction and regulation of IL-36 gamma and its receptor was determined. Polyinosinic-polycytidylic acid (poly I:C), flagellin, and synthetic lipoprotein (FSL-1) significantly induced expression of IL-36 gamma in a dose-dependent manner, and appeared to be TLR-dependent. Recombinant IL-36 gamma treatment resulted in self amplification of IL-36 gamma and its receptor (IL-36R) via increased gene expression, and promoted other inflammatory signaling pathways. This is the first report to demonstrate that the IL-36 receptor and IL-36 gamma are present in the human FRT EC and that they are differentially induced by microbial products at this site. We conclude that IL-36 gamma is a driver for epithelial and immune activation following microbial insult and, as such, may play a critical role in host defense in the FRT.
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22

Govender, Thashlin. "Antifungal activity of epithelia from selected frogs species of the south Western Cape of South Africa." Thesis, Cape Peninsula University of Technology, 2008. http://hdl.handle.net/20.500.11838/1476.

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Thesis (MTech Biomedical Technology)) ---Cape Peninsula University of Technology, 2008
Resistance to antibiotics has been acknowledged as a major global public health problem. The use of peptides to provide alternatives to combat multi drug resistant organisms is of current relevance to overcome antibiotic resistance. The high deversity of amphibian skin peptides render these animals a potential source for the discovery of novel drugs.
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23

Liu, Youzhong. "Etude des interactions levures/bactérie par métabolomique." Thesis, Dijon, 2015. http://www.theses.fr/2015DIJOS074/document.

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Le vin en tant qu’écosystème complexe est un modèle particulièrement intéressant pour l’étudie des interactions entre les microorganismes. L’interaction sans contact celluaire (interaction indirecte) entre la levure Saccharomyces cerevisae et la bactérie lactique Oenococcus oeni a un effect direct sur l’induction et l'achèvement de la fermentation malolactique (FML), une fermentation très importante pour la qualité du vin. Une souche levurienne peut être classée FML+ si elle stimule la croissance bactérienne et FML- si elle a un effet inhibiteur. Les métabolites connus qui inhibent ou stimulent la FML ne permettent pas toujours d’expliquer cette distinction phénotypique. Dans ce travail de thèse, nous avon développé un workflow multidisciplinaire qui combine l’approche métabolomique non ciblée, l’analyse classique ciblée, les statistiques et les réseaux. L’objectif premier était de dévoiler des métabolites levuriens impliqués dans l’interaction entre levures et bactéries par une comparaison directe des exométabolome des deux phénotypes.À cet effet et pour la première fois dans l’éude d’interactions inter-espèces, la Spectrométrie de Masse à Résonance Cyclotronique des Ions et à Transformée de Fourier (FT-ICR-MS) et la Chromatographie Liquide couplée à la Spectrométrie de Masses (UPLC-Q-TOF-MS) ont été combinées. Pour mieux visualiser les données à haut débit générées par les deux plate-formes, une méthode statistique non supervisée MetICA a été developpée et validée. Par rapport à l’analyse en composantes principales (ACP), cette nouvelle méthode peut réduire la dimension des données d'une façon plus robuste et fiable. Afin d’extraire des métabolites impliquées dans la distinction phénotypique, nous avons comparé différentes methodes de classification et choisi la meilleure pour chaque jeu de données. Les structures putatives de ces biomarqueurs ont été validés par la spectrométrie de masse MS/MS et leurs rôles physiologiques sur la croissance bactérienne ont été confirmées in vitro. La découverte de biomarqueurs a été complétée par l’analyse ciblée réalisées par Chromatographie en Phase Liquide à Haute Performance (HPLC). La complémentarité entre les différentes techniques métabolomiques a conduit à l’identification de nouveaux biomarqueurs de familles distinctes, comme des composés phénoliques, des sucres, des nucléotides, des acides aminés et des peptides. En outre , l'analyse des réseaux métaboliques a révélé des liens entre les biomarqueurs de levure et a suggéré des voies bactériennes influencés par l’exo-métabolome de levure.Notre workflow multidisciplinaire a révélé une réelle capacité à identifier des signatures moléculaires nouvelles et inattendues de l’interaction levure-bactérie
As a complex microbial ecosystem, wine is a particularly interesting model for studying interactions between microorganisms. Contact-independent interactions (indirect interactions) between the yeast Saccharomyces cerevisae and the lactic acid bacterium Oenococcus oeni have a direct effect on malolactic fermentation (MLF), induction and completion, which is an important factor in wine quality. Yeast strains could be classified as MLF+ phenotype if it usually stimulates the bacterial growth or MLF- in the opposite case. The known metabolites that stimulate or inhibit the MLF cannot always explain the phenotypic distinction. In this work, a multidisciplinary workflow combining non-targeted metabolomics, targeted analysis, statistics and network was developed. The main objective was to unravel diverse yeast metabolites involved in yeast-bacteria interaction via a direct comparison of exo-metabolomes of MLF+ and MLF- phenotypes.To that purpose, and for the first time in the research of interspecies microbial interactions, two metabolomics platforms, Fourier Transform Ion Cyclotron Resonance -Mass Spectrometry (FT-ICR-MS) and Liquid Chromatography coupled with Mass Spectrometry (UPLC-Q-TOF-MS) were used in combination. To better visualize the high-throughput data generated from the two platforms, a novel unsupervised statistical method, the MetICA was developed and validated. Compared to classical principal component analysis (PCA), the new method reduced the data dimension in a more robust and reliable way. To extract metabolic features involved in the phenotypic distinction, we have compared different statistical classifiers and selected the best one for each dataset. Putative structures of these biomarkers were validated via MS/MS fragmentation analysis and their physiological roles to bacteria were confirmed in vitro. The discovery of biomarkers was complemented by targeted HPLC (high performance liquid chromatography) analysis. The complementarities between different analytical techniques led to new biomarkers of distinct chemical families, such as phenolic compounds, carbohydrates, nucleotides, amino acids and peptides. Furthermore, metabolic network analysis has revealed connections between yeast biomarkers and suggested bacterial pathways influenced by yeast exo-metabolome.Our multidisciplinary workflow has shown its ability to find new and unexpected molecular evidence of wine yeast-bacteria interaction
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Wall, Erin A. "ELUCIDATION OF A NOVEL PATHWAY IN STAPHYLOCOCCUS AUREUS: THE ESSENTIAL SITE-SPECIFIC PROCESSING OF RIBOSOMAL PROTEIN L27." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3747.

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Ribosomal protein L27 is a component of the eubacterial large ribosomal subunit that has been shown to play a critical role in substrate stabilization during protein synthesis. This function is mediated by the L27 N-terminus, which protrudes into the peptidyl transferase center where it interacts with both A-site and P-site tRNAs as well as with 23S rRNA. We observed that L27 in S. aureus and other Firmicutes is encoded with a short N-terminal extension that is not present in most Gram-negative organisms, and is absent from mature ribosomes. The extension contains a conserved cleavage motif; nine N-terminal amino acids are post-translationally removed from L27 by a site-specific protease so that conserved residues important for tRNA stabilization at the peptidyl transferase center are exposed. We have identified a novel cysteine protease in S. aureus that performs this cleavage. This protease, which we have named Prp, is conserved in all bacteria containing the L27 N-terminal extension. L27 cleavage was shown to be essential in S. aureus; un-cleavable L27 did not complement an L27 deletion. Cleavage appears to play an essential regulatory role, as a variant of L27 lacking the cleavage motif could not complement. Ribosomal biology in eubacteria has largely been studied in E. coli; our findings indicate that there are aspects of the basic biology of the ribosome in S. aureus and other related bacteria that differ substantially from that of E. coli. This research lays the foundation for the development of new therapeutic approaches that target this novel, essential pathway.
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25

Wynn, Jessica Elaine. "Functionalizing Branched Peptides with Unnatural Amino Acids Toward Targeting HIV-1 RRE RNA and Microbials." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/82227.

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The interaction of the protein Rev with Rev Response Element (RRE) RNA is critical to the HIV-1 life cycle as this complex is required for the export of singly-spliced and unspliced mRNAs from the nucleus to the cytoplasm. Disruption of this interaction is considered to be a powerful strategy towards the development of HIV-1 therapeutics. Therefore, we have developed several branched peptide libraries containing unnatural amino acids to target the high-affinity binding site of RRE RNA (RRE IIB), with the idea that branching in peptides can provide multivalent contacts with folded RNA structures and boost binding affinity and selectivity for the target. Unnatural amino acids were incorporated into the library design to encourage non-canonical interactions with the RNA and to improve proteolytic stability. The on-bead high-throughput screening of our first branched peptide library (46,656 sequences) against HIV-1 RRE RNA generated hit peptides with binding affinities in the low micromolar range. We demonstrated that branching in the peptide is required for efficient binding and selectivity towards the RNA, and that the peptides bind a large surface area of RRE IIB. Introduction of boronic acids into branched peptides boosted selectivity of the peptides for RRE IIB, and proved to be a novel and tunable mode of binding towards RNA. Additionally, we revealed that these branched peptide boronic acids (BPBAs) were cell permeable and non-toxic. One BPBA (BPBA3) bound RRE IIB selectively and was able to inhibit HIV-1 replication in vitro, revealing enzymatic cleavage of the RNA upon binding. A second generation BPBA library that introduced acridinyl lysine as an intercalator (4,096 sequences) was screened against RRE IIB. Several hit compounds bound in the low nanomolar regime, and a significant number of compounds inhibited HIV-1 replication in vitro. These BPBAs were also found to severely inhibit the microbial growth of bacteria and fungus, with MICs as low as 1 µg/mL against Staphylococcus aureus, Candida albicans, and Escherichia coli. These compounds were also found to significantly inhibit biofilm formation and growth, and were non-hemolytic. High-throughput screening of a third generation BPBA library containing all unnatural amino acids (46,656 sequences) revealed several hits that bound RRE IIB RNA in the nanomolar range. Sequence motifs present in the hit peptides suggested that the location and composition of amino acids within the branched peptide structure were important for recognizing the RNA target. In particular, lead compounds 2C5 and 4B3 demonstrated selectivity towards RRE, and footprinting experiments combined with SHAPE experiments revealed different interactions of the peptides with the RNA Toxicity assays revealed no impact on cell viability for the majority of hit sequences tested up to 100 µM, and several compounds also demonstrated inhibition of HIV-1 replication.
Ph. D.
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26

Smith, Mark Wayne. "Characterisation and exploitation of microbial peptide transport systems." Thesis, Bangor University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305957.

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27

Clamens, Thomas. "Etude de l'implication de l'opéron ami de Pseudomonas aeruginosa dans l'activité anti-biofilm d'une famille d'hormones humaines." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR124.

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Dans un contexte mondial d’émergence de bactéries résistantes aux antibiotiques, il est nécessaire d’explorer de nouvelles voies de recherche pour trouver de nouveaux traitements. Cet état de fait est particulièrement marqué dans le cadre d’infections chroniques associées à une colonisation des tissus par des biofilms bactériens. L’endocrinologie microbienne est un champ de recherche axé sur l’étude des mécanismes de communication inter-règnes qui peut s’établir entre des bactéries et leurs hôtes. Les molécules humaines qui permettent ce dialogue constituent de potentiels outils capables de moduler la physiologie des bactéries pour empêcher leur développement. Dans cette optique, l’objectif de ma thèse était d’approfondir nosconnaissances sur l’effet des peptides natriurétiques, une famille d’hormones humaines, sur la physiologie du pathogène opportuniste P. aeruginosa. Les travaux que j’ai menés ont permis de préciser les mécanismes de l’action anti-biofilm du peptide natriurétique de type C ou CNP. J’ai également montré qu’un autre peptide, le peptide natriurétique atrial (ANP), est capable de disperser un biofilm établis de P. aeruginosa. Dans un second temps, j’ai pu identifier que l’opéron ami, dans son intégralité, est indispensable aux effets des peptides natriurétiques et qu’en plus les protéines codées par les gènes de l’opéron ami ont un rôle important dans la régulation de la virulence bactérienne et dans la formation des biofilms. Ainsi, j’ai pu mettre en évidence que les protéines AmiE et AmiR, en plus de leur rôle dans le métabolisme secondaire, sont impliquées dans la régulation de la virulence et de la formation de biofilm de P. aeruginosa
In a global context of emergence of antibiotic-resistant bacteria, it is necessary to explore new paths of research to find new treatments. This state of affairs is particularly marked in the context of chronic infections associated with tissue colonization by bacterial biofilms. Microbial endocrinology is a field of research focused on the study of inter-kingdom communication that can be established between bacteria and their hosts. The human molecules that allow this dialogue are potential tools capable of modulating bacterial physiology to prevent their development. In this perspective, the aim of my thesis was to deepen our knowledge about the effect of natriuretic peptides, a family of human hormones, on the physiology of the opportunistic pathogen P. aeruginosa. The work that I carried out allowed us to characterize the mechanisms of the anti-biofilm action of the natriuretic peptide type C or CNP. I have also shown that another peptide, the atrial natriuretic peptide (ANP), is able to disperse an established biofilm of P. aeruginosa. In a second step, I was able to identify that the entire ami operon is essential for the effects of the natriuretic peptides and that the proteins encoded by the genes of the ami operon have an important role in bacterial virulence regulation and in the formation of biofilms. Thus, I was able to demonstrate that the AmiE and AmiR proteins, in addition to their role in secondary metabolism, are involved in the regulation of virulence and biofilm formation of P. aeruginosa
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28

Nathan, Philip Bernard. "Genetic and biochemical studies of microbial peptidase enzymes." Thesis, Nottingham Trent University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258545.

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29

Ghannad, Mona. "Design and Synthesis of Collagen-binding Anti-microbial Proteins." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19981.

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The Herpes simplex virus (HSV) is a virus that commonly infects the skin, and mucous membrane of the mouth, genitalia, and the eye. HSV-1 is the strain that is most commonly associated with corneal infections, and it is the most frequent cause of corneal blindness in North America [1]. Currently no cure is available, and many limitations are characterized by the currently available synthetic antiviral drugs, which suggest the need for other potential drug alternatives and delivery strategies. Anti-microbial peptides are naturally occurring peptides that are potent killers of a broad range of micro-organisms, including bacteria, fungi, and viruses [2]. AMPs are known to be a key component of the innate immune response at the human ocular surface. The human cathelicidin-derived AMP, LL-37, expressed in human corneal epithelial cells provides a wide range of protection against viral pathogens such as HSV-1 [3]. My thesis research addressed the design and recombinant production of hybrid AMP sequences containing LL-37 with the potential ability to form chemical or physical associations with a Collagen scaffold material, such as those used in current artificial cornea constructs to address the need for alternative anti-viral drugs. Three fusion proteins were tested, and compared for feasible design anti-microbial peptide expression and purification in E. coli. It was illustrated that the thioredoxin and SUMO fusion systems are good candidates for successful recombinant production of active designed peptides. The point-mutated LL-37 sequence was successfully expressed and purified using the thioredoxin fusion system. It was demonstrated that this modified LL-37 was effective against HSV-1 infection. The SUMO system was used to express the bio-functional LL-37 containing a collagen-binding sequence. Further work is required to address issues regarding recombinant AMP production, such as increasing enzymatic cleavage efficacy, and minimizing proteolytic degradation or modification.
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Shurtleff, Matthew J. "DESIGNING A MICROBIAL PROLYL PEPTIDASE DELIVERY SYSTEM FOR THE TREATMENT OF CELIAC DISEASE." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/160.

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Celiac disease is an autoimmune enteropathy resulting from the ingestion of gluten and gluten-like proteins from wheat, barley and rye in afflicted individuals. Indigestible gluten-derived peptides rich in proline residues are known to be responsible for eliciting the inappropriate immune response characteristic of the disease. In this investigation, surface level expression of prolyl peptidase activity by genetically engineered probiotic lactobacilli was postulated to be a possible treatment for this disease. Plasmid-based reporter vectors were constructed utilizing a novel, homology-based cloning technique to assess the expression and localization signals from the S-layer protein gene of Lactobacillus acidophilus. These plasmids were mutated during construction due to toxicity associated with the cloned cassettes. The toxicity of the Slayer secretion and/or anchoring domains in E. coli was confirmed by cloning the fused components into an inducible expression system. When the prolyl peptidase, Xaa-Pro, from L. reuteri was incorporated into the S-layer expression cassette, the full-length protein was efficiently expressed but was not active, likely due to protein aggregation and inclusion body formation. Future research directions are discussed and a modified experimental design strategy is presented. This work provides a foundation for continued investigation into the feasibility of utilizing genetically engineered lactobacilli as a potential treatment strategy for celiac disease.
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31

Moon, Jinyoung. "Selective accrual and dynamics of proteinaceous compounds during pedogenesis: testing source and sink selection hypotheses." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/77030.

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The emerging evidence of preferential accumulation and long residence time of proteinaceous compounds in soil are counter to the traditional view that their structure is readily broken down through microbial activity. The shift in thinking of their residence time is, however, heavily influenced by physical and chemical protections in soil, representing an important change for understanding global biogeochemical carbon and nitrogen cycling. We investigated the accumulation patterns of proteinogenic amino acids for a long term (thousands of years) related to their sources and sinks. We found clear patterns of change in the amino acids in a 4000 year-chronosequence adjacent to Lake Michigan, USA (Michigan chronosequence) and they were tightly related to the shifts in their biological sources, namely aboveground vegetative community (r2=0.66, p<0.0001) and belowground microbial community (r2=0.71, p<0.0001). Results also showed great variations of approximately 49% between seasons (summer and winter). Moreover, seasonal dynamic patterns (22% variations) of the amino acids in soil mineral associated fraction were rather counter to the conceptual view that it represents a slow soil organic pool with long residence times. The amino acids enriched in the mineral associated fraction, (e.g., positively charged, aromatic, and sulfur containing amino acids), tended to preferentially accumulate in whole soil pool during the 4000 years of ecosystem development. Their interaction with soil minerals, therefore, may play a critical role in the long-term sink and selective accumulation of proteinaceous compounds with some degree of the displacement. This was further confirmed by another chronosequence system near Haast River, New Zealand, which is geologically separated and climatically- and ecologically- different from the Michigan chronosequence. Common trends between two chronosequences suggested that either polar interactions or redox reactions may be relatively more important in the mineral interaction of amino acids than non-polar interactions. The consistency of results at two disparate locations in the southern and northern hemispheres is strong evidence that the processes of pedogenesis and ecosystem development are parsimonious and predictable. Our research demonstrated fundamental understanding of behavior of proteinaceous compounds at the molecular species level, and further provided their partitioning mechanisms associated with soil components.
Ph. D.
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32

Wheeler, Gregory Lawrence. "Plant Carnivory and the Evolution of Novelty in Sarracenia alata." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531948732481904.

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33

Chou, Chung Jen James. "Design and screening of potential peptide modulator through the studies of iron-dependent regulator functions /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/8504.

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34

Telugu, Bhanu Prakash V. L. Green Jonathan A. "An analysis of aspartic peptidases expressed by trophoblasts and placenta of even-toed ungulates." Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/7197.

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Title from PDF of title page (University of Missouri--Columbia, viewed on February 23, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Jonathan A. Green. Vita Includes bibliographical references.
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35

Diaz, Benjamin. "STUDIES RELATING PQQ BIOSYNTHESIS TO PUTATIVE PEPTIDASES AND OPERON STRUCTURE IN PSEUDOMONAS SPECIES." UKnowledge, 2017. http://uknowledge.uky.edu/pss_etds/95.

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Several bacteria isolated from the broccoli rhizosphere were assayed to compare their ability to solubilize phosphate and release pyrroloquinoline quinone (PQQ) into the surrounding media. Subsequently, their genomes were sequenced and analyzed for PQQ biosynthesis operon structure. PQQ biosynthesis genes pqqA-F were found in all isolates. The order of PQQ biosynthesis genes and predicted amino acid sequences were compared to each other and the host’s ability to solubilize phosphate and release PQQ. In all Pseudomonas species, two putative protease genes, pqqF, and pqqG, flanked the canonical pqqA-pqqE biosynthesis operon. No mechanistic studies have confirmed the function of pqqF and pqqG. Pseudomonas putida KT2440 is a versatile model organism, representing environmental, agronomical, and industrial interests. Like the broccoli isolates, P. putida KT2440 biosynthesizes and releases PQQ into its surroundings. To better understand their functions within PQQ synthesis in P. putida KT2440, ∆pqqF, ∆pqqG, and ∆pqqF/∆pqqG strains of P. putida KT2440 were generated and the resulting phenotypes were studied.
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36

Silva, Alessandra Vaso Rodrigues da. "Prospecção das interações mastoparano-membrana em proteolipossomos como modelo para o desenvolvimento racional de novos agentes antimicrobianos /." Rio Claro : [s.n.], 2009. http://hdl.handle.net/11449/87736.

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Resumo: Neste trabalho estudou-se a estrutura, função e mecanismo de ação do peptídeo antibacteriano Protonectarina-MP (isolado de veneno da vespa social Protonectarina sylveirae) tendo seu resíduo C-terminal nas formas ácida (-OH) e amidada (-NH2). Os peptídeos foram sintetizados, utilizando-se a estratégia Fmoc, purificados por cromatografia líquida de alta performance. O monitoramento do material sintético foi feito por espectrometria de massas ESI-MS e por seqüenciamento através de Química Degradativa de Edman. A estrutura secundária foi investigada pelo uso de espectroscopia de dicroísmo circular e modelagem molecular. Atividade lítica (extravasamento) e interação do resíduo de triptofano em vesículas foram investigadas pelo uso de espectrômetro de fluorescência. Foram realizados ensaios sobre as interações desses peptídeos em meio de vesículas zwitteriônicas e aniônica, formando complexos proteolipossomos que foram submetidos à troca isotópica H/D monitorada por espectrometria de massas ESI-MS e MS/MS. Além disso, foram realizados ensaios biológicos de atividade hemolítica, de desgranulação de mastócito, de liberação da enzima citoplasmática Lactato Desidrogenase e de atividade antimicrobianas. Os dados de CD revelam uma tendência dos peptídeos se estruturarem em hélice-α em ambiente hidrofóbico e em ambiente de membranas. Porém, o mesmo não pode ser observado em meio aquoso. Os modelos obtidos para ambos os peptídeos por modelagem molecular mostram uma estruturação em hélice-α anfipática. Nos ensaios de atividade lítica em vesículas, os peptídeos apresentaram um processo com cooperatividade positiva, com curvas de dose-resposta que mostram uma dependência sigmoidal com a concentração do peptídeo. Os resultados da fluorescência do triptofanos mostram um deslocamento da emissão para a região de onda do azul para o peptídeo... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In the present work was studied the structure, function and mechanism of action of the antibacterial peptide Protonectarina-MP (isolated from venom of social wasp Protonectarina sylveirae) with its carboxyamidation (-NH2) and carboxyl-free (-OH) Cterminal forms. The peptides were manually synthesized on-solid phase by using Fmoc strategy and purified under HPLC. The homogeneity of the synthetic material was analyzed by ESI mass spectrometry and Edman Degradation Chemistry. The secondary structure was investigated through circular dichroism (CD) spectroscopy and molecular modeling. Lytic activity and peptides interaction with the membranes was also investigated through tryptophan emission, by fluorescence spectrometry. The interaction of peptides with zwitterionic and anionic vesicles was investigated through the combination of H/D exchange and ESI-mass spectrometry. Some biological activities, like: mast cell degranulation, release of cytoplasmic enzyme lactate dehydrogenase, hemolysis and antibiosis were investigated for both peptides. The CD spectra revealed that the peptides in hydrophobic environments or in presence of biological membranes have the tendency to form helix conformations; however, organized structures were not observed in aqueous or buffer solutions. The models obtained by molecular modeling show that both peptides form an amphipathic α-helix. The peptides presented a positive cooperative process in the lytic activity of vesicles, with dose-response curves presenting a sigmoidal dependence with the peptide concentration. The results of the fluorescence of tryptophans showed a shift of the emission wavelength to the blue region of the peptide Protonectarina-MP (-NH2), which was not observed for its analogue presenting the C-terminal residue in free acid form. This is indicating a greater interaction of the amidated peptide in membranes, when compared to the peptide... (Complete abstract click electronic access below)
Orientador: Mario Sergio Palma
Coorientador: João Ruggiero Neto
Banca: Ivo Lebrun
Banca: Pietro Ciancaglini
Mestre
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37

Prabhu, Saurabh. "Determining the in vitro anti-cancer effects of various novel indoles and an anti-microbial peptide towards a potential treatment of glioma." Thesis, University of Central Lancashire, 2014. http://clok.uclan.ac.uk/11323/.

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Substituted indoles (2-arylindoles) and related structures are known to exhibit potent anti-cancer activity against human breast cancer cell lines, and a range of other therapeutic targets. This activity, and other factors such as their biological activity, the fact that they are privileged structures, and the presence of the indole nucleus in various commercial anti-cancer drugs led to the choosing of indoles for the current study as a starting point for the development of new treatments against glioma. Investigation began on determining the anti-cancer activity of a variety of indoles against glioma cell lines (1321N1 and U87MG) using a number of different cell-based assays and also to compare them with conventional anti-cancer drugs. The aim was to find potent anti-cancer compound(s), amongst the compounds tested, and by studying its preliminary structure-activity-relationships (SAR), try to determine how the active compound(s) may be exerting their effects. The SAR screening was divided into two main groups: indoles without a 2-aryl group and indoles with a 2-aryl group. The most potent compound identified, and its analogues, were further tested on the non-cancerous SVGp12 cell line to check for specificity of these indoles towards cancer cells, wherein it was found that these compounds were not specific to any particular cell type. Furthermore, activity was also observed for the best lead compound in the glioblastoma short-term culture, IN859, in which it gave a relatively low micromolar IC50 value (400 μM). The results indicated that the anti-cancer activity of these compounds started within 2 h and therefore it was speculated that the mechanism of action of these compounds might work through the generation of reactive oxygen species (ROS). A ROS-detection kit was used to demonstrate this hypothesis, a result which was later corroborated using flow cytometry, and also provided quantitative analysis of the amount of ROS generated. It was further hypothesised that in the cells studied, autophagy was mediated due to excessive ROS generation. This was also confirmed over a similar time course by quantifying the amount of fluorescence generated in the 1321N1 and U87MG cell lines when labelled with acridine orange (a dye used to detect the formation of autophagosomes during autophagy) using flow cytometry. Moreover, the use of an autophagy inhibitor, 3-methyladenine, was shown to inhibit autophagy in these cell lines, again validating this hypothesis. In conclusion, it has been demonstrated that the ability of certain substituted privileged indoles possessing a 2-aryl group and having an attached –OH group to it may have a rapid, deleterious effect on the viability of a primary short term culture (IN859) and glioma cell lines (1321N1 and U87MG). The mechanism of action of these indoles to cause cell death may be via the generation of ROS, leading to cell death initiated by autophagy. Another short separate study was also performed in order to investigate the anti-cancer activity of an anionic host defence peptide, Cn-AMP2, on the above mentioned cell lines. This peptide was found to exhibit a modest cytostatic effect on both the cell lines but at higher concentrations (> 1 mM) and only when the serum concentrations were weaned down from 10 % to 2.5 %.
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38

Milhan, Noala Vicensoto Moreira. "Avaliação do peptideo LL-37 em contato com células-tronco da polpa dentária /." São José dos Campos, 2017. http://hdl.handle.net/11449/149791.

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Orientador: Samira Esteves Afonso Camargo
Banca: Luana Marotta Reis de Vasconcellos
Banca: Mônica Ghislaine Oliveira Alves
Banca: Cristina Pacheco Soares
Banca: Cacio de Moura Netto
Resumo: O peptídeoLL-37 (catelicidina derivada de humano), é liberado por algumas células humanas e capaz de neutralizar os tecidos com lipopolissacarídeo (LPS), além de atrair células da polpa, e induzir a angiogênese, características que o tornam um possível adjunto para a regeneração do complexo dentino-pulpar. O objetivo desse trabalho foi avaliar in vitro a biocompatibilidade do peptídeo LL-37 nas concentrações de 5 e 10 µg/mL, e sua possível atuação na diferenciação de células-tronco da polpa dentária (DPSC) para odontoblastoslike. Com esse propósito, foram avaliados: (a) a citotoxicidade, pelo teste MTT; (b) a genotoxicidade, através do ensaio do micronúcleo; (c) a produção e quantificação de óxido nítrico; (d) as fases do ciclo celular, por citometria; (e) a expressão de alguns genes associados à formação de tecido mineralizado, através do teste qRT-PCR; (f) o conteúdo de proteína total; (g) a atividade de fosfatase alcalina (ALP); e (h) a produção de sialofosfoproteína dentinária (DSPP), pelo ensaio imunoenzimático ELISA. Foi observado que as concentrações de 5 e 10 µg/mL de LL-37 não foram citotóxicas e ainda aumentaram, em geral, a viabilidade celular (p<0,05), sendo que os maiores valores de absorbância foram observados no 3° dia de contato. As concentrações testadas também não induziram genotoxicidade, após 7 dias de contato, tendo sido genotóxico apenas o grupo controle positivo (EMS) (p<0,05). Ainda, não foi observado diferença estatisticamente significativa na produção de nitrito, pelas células expostas ao LL-37 após 7 dias, em ambas as concentrações. A análise do ciclo celular, evidenciou maior porcentual de células na fase G0/G1, em todos os grupos (p<0,05). Quando estes foram comparados, foi observado maior quantidade de células na fase G0/G1 na concentração de... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract : The LL 37 peptide (human derived cathelicidin) is released by some human cells and able of neutralizing the tissues that present lipopolysaccharide (LPS), as well as, attracts pulp cells and induces angiogenesis; characteristics that makes it a possible adjunct for regeneration of the dentin-pulp complex. The aim of this study was evaluate in vitro the biocompatibility of LL-37 in the concentrations of 5 and 10 µg/mL, and its possible performance in the differentiation of dental pulp stem cells (DPSC) into odontoblasts-like cells. For this purpose, it was evaluated: (a) the cytotoxicity by MTT assay; (b) the genotoxicity by the micronucleus test; (c) the production and quantification of nitric oxide; (d) the cell cycle, by flow cytometry; (e) the expression of genes associated with the mineralization by qRT-PCR; (f) the total protein content; (g) the alkaline phosphatase activity (ALP); and (h) the production of dentine sialofosfoprotein (DSPP) by indirect enzyme-linked immunosorbent assay (ELISA). It was observed that the concentrations of 5 and 10 µg/ml of LL-37 were not cytotoxic, in addition to they increased, in general, the cell viability (p<0,05). Moreover, higher absorbance values were observed on 3rd day of contact. After 7 days, the tested concentrations also did not induce genotoxicity, (p<0,05); only the positive control group (EMS) was genotoxic (p<0.05). Furthermore, there was not statistical significance in the nitrite production by the cells exposed to LL-37 for 7 days, in both concentrations. The cell cycle test showed higher percentage of cells in the phase G0/G1 in all groups (p<0.05). When they were compared, it was noticied that concentration of 10 ug/ml of LL-37 arrested the cells in G0/G1 compared to the control group (p<0.05). On the other hand, the control group, exhibited higher amount of cells in G2 and mitosis...(Resumo completo, clicar acesso eletrônico abaixo)
Doutor
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39

Silva, Alessandra Vaso Rodrigues da [UNESP]. "Prospecção das interações mastoparano-membrana em proteolipossomos como modelo para o desenvolvimento racional de novos agentes antimicrobianos." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/87736.

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Neste trabalho estudou-se a estrutura, função e mecanismo de ação do peptídeo antibacteriano Protonectarina-MP (isolado de veneno da vespa social Protonectarina sylveirae) tendo seu resíduo C-terminal nas formas ácida (-OH) e amidada (-NH2). Os peptídeos foram sintetizados, utilizando-se a estratégia Fmoc, purificados por cromatografia líquida de alta performance. O monitoramento do material sintético foi feito por espectrometria de massas ESI-MS e por seqüenciamento através de Química Degradativa de Edman. A estrutura secundária foi investigada pelo uso de espectroscopia de dicroísmo circular e modelagem molecular. Atividade lítica (extravasamento) e interação do resíduo de triptofano em vesículas foram investigadas pelo uso de espectrômetro de fluorescência. Foram realizados ensaios sobre as interações desses peptídeos em meio de vesículas zwitteriônicas e aniônica, formando complexos proteolipossomos que foram submetidos à troca isotópica H/D monitorada por espectrometria de massas ESI-MS e MS/MS. Além disso, foram realizados ensaios biológicos de atividade hemolítica, de desgranulação de mastócito, de liberação da enzima citoplasmática Lactato Desidrogenase e de atividade antimicrobianas. Os dados de CD revelam uma tendência dos peptídeos se estruturarem em hélice-α em ambiente hidrofóbico e em ambiente de membranas. Porém, o mesmo não pode ser observado em meio aquoso. Os modelos obtidos para ambos os peptídeos por modelagem molecular mostram uma estruturação em hélice-α anfipática. Nos ensaios de atividade lítica em vesículas, os peptídeos apresentaram um processo com cooperatividade positiva, com curvas de dose-resposta que mostram uma dependência sigmoidal com a concentração do peptídeo. Os resultados da fluorescência do triptofanos mostram um deslocamento da emissão para a região de onda do azul para o peptídeo...
In the present work was studied the structure, function and mechanism of action of the antibacterial peptide Protonectarina-MP (isolated from venom of social wasp Protonectarina sylveirae) with its carboxyamidation (-NH2) and carboxyl-free (-OH) Cterminal forms. The peptides were manually synthesized on-solid phase by using Fmoc strategy and purified under HPLC. The homogeneity of the synthetic material was analyzed by ESI mass spectrometry and Edman Degradation Chemistry. The secondary structure was investigated through circular dichroism (CD) spectroscopy and molecular modeling. Lytic activity and peptides interaction with the membranes was also investigated through tryptophan emission, by fluorescence spectrometry. The interaction of peptides with zwitterionic and anionic vesicles was investigated through the combination of H/D exchange and ESI-mass spectrometry. Some biological activities, like: mast cell degranulation, release of cytoplasmic enzyme lactate dehydrogenase, hemolysis and antibiosis were investigated for both peptides. The CD spectra revealed that the peptides in hydrophobic environments or in presence of biological membranes have the tendency to form helix conformations; however, organized structures were not observed in aqueous or buffer solutions. The models obtained by molecular modeling show that both peptides form an amphipathic α-helix. The peptides presented a positive cooperative process in the lytic activity of vesicles, with dose-response curves presenting a sigmoidal dependence with the peptide concentration. The results of the fluorescence of tryptophans showed a shift of the emission wavelength to the blue region of the peptide Protonectarina-MP (-NH2), which was not observed for its analogue presenting the C-terminal residue in free acid form. This is indicating a greater interaction of the amidated peptide in membranes, when compared to the peptide... (Complete abstract click electronic access below)
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40

Masson, Florent. "Régulations immunitaires et cellulaires impliquées dans le maintien et le contrôle des bactéries endosymbiotiques du charançon des céréales du genre Sitophilus spp." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0116/document.

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Plusieurs insectes se développant dans des milieux nutritionnellement déficients vivent en symbiose durable avec des bactéries intracellulaires (endosymbiotes) qui complémentent leur alimentation et améliorent leur pouvoir adaptatif. Alors que ces associations ont été largement étudiées sur les plans physiologiques et évolutifs, peu de travaux se sont consacrés à l’étude des mécanismes impliqués dans la tolérance et le contrôle des endosymbiotes par l’hôte. L’objectif de cette thèse est d’étudier, chez les charançons des céréales du genre Sitophilus, les particularités moléculaires et immunitaires du bactériome, un organe que l’insecte développe pour héberger les symbiotes et les isoler de sa réponse immunitaire systémique. Le bactériome du charançon exprime une réponse immunitaire modulée : des études transcriptomiques ont montré que les effecteurs de l’immunité sont peu exprimés dans cet organe, à l’exception d’un gène codant un peptide antimicrobien, la coléoptéricine A. Cette dernière interagit avec les endosymbiotes et participe à leur confinement intracellulaire. Dans une première partie, j’ai montré avec une approche d’interférence à l’ARN que l’expression du gène colA serait contrôlée par un système original qui impliquerait les gènes relish et tollip. Cette régulation « interne » au bactériome semble assurer le maintien des endosymbiotes et l’homéostasie de l’organe. Afin de comprendre comment le bactériome répond à une infection par les bactéries exogènes, j’ai suivi par RT-qPCR l’expression de gènes effecteurs de l’immunité dans le bactériome après injection systémique de bactéries à Gram positif ou négatif. Ceci a mis en évidence une réponse « externe », induite en cas d’infection, et qui aurait un rôle de protection des endosymbiotes contre les bactéries exogènes. Enfin, je me suis consacré à l’étude des changements de régulation accompagnant le passage du stade larvaire au stade adulte, marqué par une symbiose très dynamique. Le nombre d’endosymbiotes augmente fortement pendant les premiers jours de vie imaginale, puis diminue jusqu’à leur élimination complète par recyclage autophagique. Une analyse RNAseq a permis d’identifier les voies de signalisation dont l’activité accompagne cette dynamique. Une approche de RT-qPCR a également montré que l’immunité du bactériome est maintenue à un faible niveau d’activation pendant tout le processus de recyclage. Ce travail montre qu’au cours de leur évolution, les insectes ont sélectionné plusieurs stratégies pour assurer le maintien et l’ajustement de leur charge endosymbiotique en fonction de leurs besoins physiologiques : une signalisation immunitaire assurerait le confinement intracellulaire des endosymbiotes, et un ensemble de processus cellulaires incluant l’apoptose et l’autophagie semble être en associé aux voies métaboliques pour assurer le contrôle de la dynamique bactérienne et garantir le compromis bénéfice/coût de la symbiose
Many insect species living on nutritionally unbalanced media depend on intracellular mutualistic bacteria, called obligatory endosymbionts, for their development and reproduction. Endosymbionts are housed in specialized host cells called bacteriocytes, that group together to form the bacteriome organ. Although such associations have been widely investigated on a physiological and evolutionary point of view, little is known about the mechanisms involved in the tolerance and the control of endosymbionts by the host. This work aims at deciphering the molecular and immune specificities of the bacteriome using the model system Sitophilus oryzae, the cereal weevil, and its obligate endosymbiont Sodalis pierantonius. The weevil bacteriome expresses a modulated immune response: transcriptomic studies showed that immune effector genes were lowly expressed despite the massive bacterial presence, with the exception of colA, a gene encoding for Coleoptericin A, an antimicrobial peptide. Coleoptericin A interacts with endosymbionts and participates in their intracellular seclusion. In a first chapter, I used RNA interference to demonstrate that colA gene expression may be controlled by an original system involving the genes relish and tollip. This “internal” regulation for endosymbiont control seems to maintain bacteriome homeostasis. In a second chapter, in order to understand how the bacteriome responds to an infection by exogenous bacteria, I followed up by RT-qPCR the expression of immune effector genes in the bacteriome after injection of Gram positive and Gram negative bacteria. This highlighted an “external” immune response, inducible upon infections, which may enable endosymbiont protection against exogenous intruders. In a third and last chapter, I focused on the regulation changes that accompany the switch from the larval stage to the imaginal stage, the latter being characterized by a very dynamic symbiosis. Endosymbiont load drastically increases during the first days of imaginal life, then rapidly decreases until complete elimination of the bacteria by autophagic recycling. RNAseq analysis allowed the identification of signaling pathways linked to this dynamic. A complementary RT-qPCR approach also showed that bacteriome immunity was laid low during the whole recycling process. This work shows that several strategies have been selected during host-symbiont coevolution to ensure the maintenance of the endosymbionts and the adjustment of their population depending on the insects physiological needs: immunity allows the intracellular seclusion in the bacteriocytes, and cell processes including autophagy and apoptosis are associated to metabolic pathways to control the endosymbiotic dynamics and secure the cost and benefit trade-off of symbiosis
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41

Trino, Luciana Daniele. "Funcionalização de superfícies e estudo de adsorção de biomoléculas em óxidos metálicos." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/154201.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O titânio e suas ligas são utilizados em diversas aplicações, dentre elas em implantes ortopédicos e dentários devido à sua reconhecida biocompatibilidade. No entanto, falhas e subsequentes efeitos colaterais clínicos ainda são recorrentes em implantes. Neste contexto, melhorias podem ser alcançadas projetando biomateriais nos quais o bulk e a superfície do titânio são independentemente modificadas. Deste modo, filmes finos nanoestruturados de óxidos metálicos, tais como TiO2 e ZnO, podem melhorar as propriedades físico-químicas, a biocompatibilidade e a resistência à corrosão dos implantes de titânio. Além disso, a conjugação de biomoléculas, como peptídeos derivados da proteína da matriz dentinária 1 (DMP1), na superfície dos óxidos metálicos pode melhorar sua bioatividade, acelerando o processo de osteointegração. Dessa forma, o objetivo deste trabalho foi funcionalizar óxidos metálicos com diferentes moléculas bifuncionais e investigar as propriedades físico-químicas de grupos silano, amino, ácido carboxílico, tiol e hidroxila que atuaram como espaçadores entre os óxidos metálicos e os peptídeos da DMP1. Além disso foram realizadas análises de biocompatibilidade, mineralização, resistência à corrosão e à tribocorrosão das superfícies bio-funcionalizadas com os peptídeos da DMP1. Neste trabalho, filmes de TiO2 e ZnO nanométricos foram sintetizados pelo método sol-gel e depositados pela técnica spin coating em substratos de titânio. Posteriormente, os filmes finos de óxidos metálicos foram funcionalizados com (3-aminopropil) trimetoxissilano (APTMS), ácido 3- (4-aminofenil) propiônico (APPA), ácido 3-mercaptopropiônico (MPA) ou polietilenoglicol (PEG), que atuam como espaçadores entre os óxidos metálicos e os peptídeos da DMP1. As análises físico-químicas por XPS, microscopia confocal, AFM, ângulo de contato e energia de superfície revelaram a efetiva modificação das superfícies dos óxidos metálicos com APTMS, APPA, MPA e PEG. Após a bio-funcionalização as análises físico-químicas confirmaram a presença dos peptídeos da DMP1 na superfície dos óxidos metálicos. Além disso, testes biológicos indicaram que os peptídeos puderam modular a afinidade, proliferação e diferenciação de células mesenquimais humanas. Para a amostra contendo o dióxido de titânio, foram observados melhores resultados para o TiO2 funcionalizado com MPA e os peptídeos da DMP1. Já para o óxido de zinco, melhores resultados de biocompatibilidade foram observados para ZnO funcionalizado com APPA e os peptídeos. Além disso, a imobilização dos peptídeos da DMP1 através dos espaçadores APPA e MPA, para ambos os óxidos, levou à formação de biominerais de apatita. Os resultados eletroquímicos indicaram um aumento da resistência à corrosão nos materiais bio-funcionalizados, sendo que melhores resultados foram observados para o TiO2 quando comparado ao ZnO. Além disso a análise de tribocorrosão apresentou menor perda de massa para as amostras de TiO2 bio-funcionalizadas. Considerando os aspectos de biocompatibilidade, diferenciação osteogênica, mineralização, resistência à corrosão e à tribocorrosão a amostra de TiO2 funcionalizada com MPA e os peptídeos da DMP1 foi a que apresentou melhores resultados. Portanto, os resultados obtidos sugerem que a bio-funcionalização de óxidos metálicos é capaz de projetar implantes de melhor qualidade aplicados à medicina regenerativa.
Titanium and its alloys are used in a variety of applications, including orthopedic and dental implants because of their recognized biocompatibility. However, failures and subsequent clinical side effects are still recurrent in implants. In this context, improvements can be achieved by designing biom aterials in which the bulk and surface of the titanium are independently tailored . Thus, nanostructured metal oxides thin films , such as TiO 2 and ZnO, can improve the physicochemical properties, biocompatibility and corrosion resistance of titanium implant s. In addition, the conjugation of biomolecules, such as peptides derived from the dentin matrix 1 protein (DMP1), on the surface of the metal oxides can improve their bioactivity, accelerating the os t eointegration process. Therefore, the objective of thi s work was to functionalize metal oxides with different bifunctional molecules and to investigate the physicochemical properties of silane, amino, carboxylic acid, thiol and hydroxyl groups that act as spacers between metal oxides and DMP1 peptides. In add ition, biocompatibility, mineralization, corrosion and tribocorrosion resistance of the bio - functionalized surfaces were performed. In this work, nanosized TiO 2 and ZnO thin films were synthesized by sol - gel method and deposited by spin coating technique o n titanium substrates. Subsequently, the thin films of metal oxides were functionalized with (3 - aminopropyl) trimethoxysilane (APTMS), 3 - (4 - aminophenyl) propionic acid (APPA), 3 - mercaptopropionic acid (MPA) or polyethylene glycol (PEG), which acted as spac ers between the metal oxides and the DMP1 peptides. The physicochemical analyzes by XPS, confocal microscopy, AFM, contact angle and surface energy revealed the effective modification of the metal oxides surfaces with APTMS, APPA, MPA and PEG. After the bi o - functionalization the physicochemical analyzes confirmed the presence of the DMP1 peptides on the surface of the metal oxides. In addition, biological tests indicated that the peptides could modulate the affinity, proliferation and differentiation of hum an mesenchymal stem cells. For the sample containing the titanium dioxide, better results were observed for the TiO 2 functionalized with MPA and the DMP1 peptides. On the other hand, better biocompatibility results were observed for ZnO functionalized with APPA and peptides. In addition, the immobilization of the DMP1 peptides through the APPA and MPA spacers for both oxides led to the formation of apatite biominerals. The electrochemical results indicated an increase in corrosion resistance in the bio - func tionalized materials, and better results were observed for TiO 2 when compared to ZnO. In addition, the tribocorrosion analysis presented lower mass loss for the bio - functionalized TiO 2 samples. Considering the aspects of biocompatibility, osteogenic differ entiation, mineralization, resistance to corrosion and tribocorrosion, the TiO 2 functionalized with MPA and DMP1 peptides presented the best results. Therefore, the results suggest that the bio - functionalization of metal oxides can design better quality im plants applied to regenerative medicine
2014/01713-3
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42

Nelson, Geoffrey Winston. "Surface characterization and functional properties of carbon-based materials." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:f22b95ce-65f3-4d9e-ac3d-a88f6e142c1a.

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Carbon-based materials are poised to be an important class of 21st century materials, for bio-medical, bio-electronic, and bio-sensing applications. Diamond and polymers are two examples of carbon-based materials of high interest to the bio-materials community. Diamond, in its conductive form, can be used as an electrochemical bio-sensor, whilst its nanoparticle form is considered a non-inflammatory platform to deliver drugs or to grow neuronal cells. Polymers, especially when chemically modified, have been used extensively in biological environments, from anti-microbial use to drug delivery. The large-scale use of either material for biological use is limited by two factors: ease of chemical modification and the paucity of knowledge of their surface chemistry in aqueous media. This thesis addresses aspects of both these issues. The first study reported is an in situ study of the adsorption dynamics of an exemplar globular protein (bovine serum albumin, BSA) on nanodiamond using the relatively novel quartz crystal microbalance with dissipation (QCM-D) technique. For the first time, QCM-D enabled the detailed study of protein dynamics (i.e. kinetics, viscoelastic properties, overlayer structure, etc.) onto nanodiamond thin films having various surface chemistry and roughness. The dynamics of protein adsorption is found to be sensitive to surface chemistry at all stages of adsorption, but it is only sensitive to surface roughness during initial adsorption phases. Our understanding of the nanodiamond-biology interface is enhanced by this study, and it suggests that QCM-D is useful for the study of the surface chemistry of nanoparticle forms of inorganic materials. A second study concerns a novel surface functionalization scheme, based on carbene and azo-coupling chemistry, which has been recently introduced as a practical, facile method for modifying the surfaces of polymers. Using modern surface characterization techniques, it is demonstrated that a chemical linker can be attached to polystyrene surfaces using carbene-based chemistry, and that further chemical functionality can be added to this chemical linker via an azo-coupling reaction. In situ studies of protein dynamics at these interfaces were conducted using QCM-D, thus enabling a link between specific protein behaviour and the polymer surface chemical termination chemistry to be made. A third area of study of investigates the use of diamond electrodes as a bio-sensor for dopamine under physiological conditions. For these conditions, ascorbic acid interferes with the dopamine oxidation signal, in ways that render the two signals irresolvable. Various modifications are used in attempts to reduce this interference, including: small and large cathodic treatments, grafting of electro-active polymers, addition of carbon nanotubes, and hydrogen plasma treatment. Those modifications leading to the hydrogen-termination of diamond are shown to work the best. Notably, hydrogen plasma treatment effects the complete electrochemical separation of dopamine and ascorbic acid at a diamond electrode. This is the first time this has been accomplished without adding non-diamond materials to the diamond electrode surface.
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43

Kuo, Ting-Rung, and 郭庭榕. "Identification of anti-microbial peptides and their functional types." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2ec6u3.

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碩士
國立中央大學
資訊工程學系
106
Owing to the abuse of antibiotics, the infection resistance of microbial pathogens against chemical antibiotics increases rapidly. Antimicrobial peptides (AMPs) are essential components of the innate immune system with the lower possibility on the emergence of resistance and produced by virtually all organisms known on earth, hence become the attractive candidates for development as therapeutics. AMPs are able to resist various pathogenic microorganisms, such as viruses, parasites, bacteria, and fungi. However, little research dedicates to differentiate the multiple functional types of AMPs simultaneously or even analyze those features that may highly related to distinguish them. In this study, we construct 8 classifiers under two-stage framework to identify the AMPs with their functional types. Moreover, we adopted forward selection strategy to find some important features that may associate with the functional types of AMPs. In the first stage, the resulting area under curves (AUC) of AMP classifier is 0.9894 on the testing set. In the second stage, the AUCs of parasitic, viral, cancer, mammalian, fungal, gram-positive bacterial and gram-negative bacterial are 0.7474, 0.9397, 0.8150, 0.8515, 0.8533, 0.8725 and 0.8576 on the independent testing set, respectably. Besides, we found that hydrophobicity, normalized van der Waals volume, polarity, polarizability, charge, secondary structure and solvent accessibility in the first residue were important patterns to identify AMPs and non-AMPs. In addition to these seven properties, pseudo amino acid composition was also the important factors to distinguish different functional types of AMPs. We developed a web-server called AMPfun to provide our classifiers for AMP and their functional types prediction.
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44

Lam, Lisa Ngoc Han. "The synthesis of Staphylococcal quorum sensing-inhibiting cyclic peptides via continuous-flow solid phase peptide." Thesis, 2017. http://hdl.handle.net/1959.7/uws:45620.

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The overuse of antibiotics has imposed immense selective pressure on Staphylococcal bacteria which has resulted in the increased evolution of antibiotic-resistant bacteria such as Methicillin-resistant S. aureus to the point where last-line agents are now obsolete. Therefore, there is great pressure to develop novel approaches to combat bacterial infections while minimising the development of resistance. Here, the development of compounds which inhibit bacterial quorum sensing through antagonism of the accessory gene regulator (agr) display promise as a new generation of therapeutics. In this study, which focused on S. aureus group I, the previously reported agr inhibitor tr-Ac(Ala5)-AIP-1 was subjected to structure-activity-relationship studies with peptides synthesised under continuous-flow solid-phase conditions. Evaluation of the agrC-I inhibitory activities of the resulting library of cyclic peptides demonstrated that the three analogues, compound 16, 18 and 13 displayed sub-nanomolar inhibitory activities (IC50 < 0.7 nM, IC50 < 0.7 nM & IC50 < 0.7 nM, respectively). It is hopeful that the principle pharmacophores for agrC-I developed in this study will provide a valuable platform for the development of global agr-inhibitors as next-generation anti-bacterial therapeutics.
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45

Uma, M. V. "Studies on Efrapeptins." Thesis, 1999. https://etd.iisc.ac.in/handle/2005/1536.

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46

Uma, M. V. "Studies on Efrapeptins." Thesis, 1999. http://etd.iisc.ernet.in/handle/2005/1536.

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47

Chia, Brian Cheng San. "Amphibian antimicrobial peptides : their structures and mechanisms of action / by Brian Cheng San Chia." Thesis, 2000. http://hdl.handle.net/2440/19636.

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Copy of author's previously published works inserted.
Bibliography: leaves 183-220.
xiii, 226 leaves : ill. (chiefly col.) ; 30 cm.
Three antimicrobial peptides, maculatin 1.1, uperin 3.6 and caerin 4.1 have been isolated from the respective skin glands of the Australian amphibians Litoria genimaculata, Uperoleia mjobergii and Litoria caerulea. To gain a deeper insight into their mechanisms of action, three dimensional structural studies have been conducted using circular dichroism, two-dimensional nuclear resonance and computer modelling techniques. The role of central flexibility within antibiotic peptides in their interaction with bacterial membranes is also discussed.
Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2000
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48

Takahashi, Sumiko Logan Timothy M. "Preparation and crystallization trials of HR1 peptide bound iron-dependent repressor protein of mycobacterium tuberculosis." 2006. http://etd.lib.fsu.edu/theses/available/etd-05082006-173409.

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Thesis (M.S.)--Florida State University, 2006.
Advisor: Timothy M. Logan, Florida State University, College of Arts and Science, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Sept. 15, 2006). Document formatted into pages; contains xi, 63 pages. Includes bibliographical references.
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49

Goredema, Wadzanayi Patience. "An investigation into the proteolytic degradation of antimicrobial peptides by plant extracts and localisation of pleurocidin in transgenic saccharum hybrid species." Thesis, 2001. http://hdl.handle.net/10413/9779.

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Two cationic antimicrobial peptides, ESF I-GR7, and pleurocidin, were assessed for their stability in plant intercellular fluid, the targeted locale for their expression in transgenic plants. Incubation of ESFI-GR7 and pleurocidin with intercellular fluid (ICF) extracted from sugarcane, tomato and tobacco leaves reduced their biotoxicity towards various pathogens, namely Camobacterium mobile DMSO and Xanthomollas campestris. It was concluded that it may be necessary to modify the aminoacid structures of the peptides in order to ensure that endogenous proteases would not degrade the peptides once expressed in a transgenic environment. The presence of pleurocidin was detected in transgenic sugarcane transformed (in a previous study) with pleurocidin gene cloned into the pUBI 510 plasmid. ICF was extracted from four month old transgenic Saccharum hybrid species (sugarcane). Western blotting verified the presence of the transgenic protein in crude protein extracts. Immunogold labelling and transmission electron microscopy were performed to investigate the localisation of transgenic pleurocidin. The peptide was localized predominantly in the intercellular spaces and cell wall sugarcane leaves.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.
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50

Wabnitz, Paul Andrew. "Chemistry and medical implications of novel amphibian peptides : a thesis submitted for the degree of Doctor of Philosophy / by Paul Andrew Wabnitz." Thesis, 1999. http://hdl.handle.net/2440/19494.

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Copies of author's previously published articles inserted.
Includes bibliographical references.
xv, 210 leaves : ill. ; 30 cm.
A chemical and pharmacological investigation of compounds derived from amphibian skin. Isolates novel amphibian peptides and further investigates the biological activity of some of the peptides discovered.
Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2000
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