Dissertations / Theses on the topic 'Divalent metal ions release'
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1
Awassa, Jazia. "Mécanismes antibactériens des hydroxydes doubles lamellaires à base de zinc." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0155.
Abstract:
Les hydroxydes doubles lamellaires (HDL) sont des composés solides constitués par un ensemble de feuilles d'hydroxydes métalliques divalents M(II) et trivalents M(III) entre lesquels s’insèrent des anions et des molécules d’eau. En raison de la flexibilité des HDL en termes de propriétés physico-chimiques, l’étude des différents mécanismes antibactériens qui leurs sont associés présente un intérêt croissant. Ce travail de thèse vise à étudier différentes hypothèses proposées pour explique l'effet antibactérien des hydroxydes doubles lamellaire (HDL) à base de zinc : (1) interactions directes entre la surface des HDL et les parois bactériennes, (2) libération d'ions métalliques divalents en solution depuis les feuillets des HDL, (3) génération d'espèces réactives de l'oxygène (ROS). Lors d’une première étude, une investigation globale a été réalisée pour déterminer les différents paramètres physico-chimiques influençant l'activité antibactérienne des HDLs M(II)Al(III) (M= Zn, Cu, Ni, Co, Mg). L'effet antimicrobien des HDLs contre les bactéries Gram-positives Staphylococcus aureus et Gram-négatives Escherichia coli a été corrélé en premier lieu à la nature du métal divalent, et en second lieu à la quantité d'ions M2+aq libérés dans le milieu de culture. Cet effet était plus prononcé pour les HDLs à base de Zn(II) possédant la plus forte activité antibactérienne et dont les propriétés antibactériennes dépendent du profil de libération des ions Zn2+aq (Mécanisme 2) contrôlée initialement par les différents paramètres physico-chimiques étudiés. De plus, rôle du contact direct (Mécanisme 2) a été validé pour les HDLs à base de Zn(II) en comparant l'activité antibactérienne d’HDLs de taille micrométrique contre S. aureus à celle des nanoparticules (NPs) d’HDL présentant un effet antibactérien supérieur. La présence d'interactions spécifiques entre les HDLs à base de Zn(II) et la paroi de S. aureus a été validée par microscopie à force atomique en mode spectroscopie de force (AFM-FS). L'amélioration des propriétés antibactériennes des NPs d’HDL à base de Zn(II) par la génération de ROS (Mécanisme 3) en présence de lumière UVA a également été évaluée. Après avoir fourni des preuves expérimentales sur les trois mécanismes suggérés, la contribution de chaque mécanisme dans l'activité antibactérienne des HDLs à base de Zn(II) a été déterminéLayered double hydroxides (LDH) are solid compounds constituted by the stacking of divalent M(II) and trivalent M(III) metal hydroxide sheets separated by an interlayer of anions and water molecules. Due to the versatility of LDH in terms of their tunable physico-chemical properties, a growing interest arises for investigating their different antibacterial activity mechanisms. This thesis work aims at studying the different proposed hypotheses explaining the antibacterial effect of pristine zinc-based LDHs: (1) direct interactions between the surface of LDH and bacterial cell walls, (2) release of constituent divalent metal ions, (3) generation of reactive oxygen species (ROS). First a global investigation was performed to determine the different physico-chemical parameters influencing the antibacterial activity of pristine M(II)Al(III) LDHs (M= Zn, Cu, Ni, Co, Mg). The antimicrobial effect of LDHs against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria was linked in the first place to the nature of divalent metal itself, and to the amount of released M2+aq ions into the culture media in the second place. This effect was more easily identified in Zn(II)-based LDHs possessing the strongest antibacterial activity and whose antibacterial properties depended on their release profile of Zn2+aq ions (Mechanism 2) initially controlled by the different physico-chemical parameters. Moreover, the direct contact mechanism (Mechanism 1) was validated for Zn(II)-based LDHs by comparing the antibacterial activity of micron-sized LDHs against S. aureus to that of LDH nanoparticles (NPs) exhibiting a greater antibacterial effect. The presence of specific surface interactions between Zn(II)-based LDHs and the cell wall of S. aureus was further validated by atomic force microscopy-based force spectroscopy (AFM-FS). The enhancement of the antibacterial properties of Zn(II)-based LDH NPs by ROS generation (Mechanism 3) in presence of UVA light was also assessed. After providing experimental evidences about the three suggested mechanisms, the role of each mechanism contributing to the antibacterial activity of Zn(II)-based LDHs in different antibacterial tests assays was determined
2
Wang, Yu-Wen. "Substitution of Calcium with Divalent Metal Ions in Paraoxonase I." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1420819949.
3
Afolaranmi, Grace Ayodele. "Disposition of metal ions in patients after release from orthopaedic arthroplasties." Thesis, University of Strathclyde, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501856.
4
Bellomo, Elisa. "Divalent metal ions and the pancreatic B-cell : role in the pathogenesis of type 2 diabetes." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526394.
5
Ferko, Maxime-Alexandre. "Molecular Mechanisms Involved in Interleukin-1β Release by Macrophages Exposed to Metal Ions from Implantable Biomaterials." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37331.
Abstract:
Metal ions released from implantable biomaterials have been associated with adverse biological reactions that can limit implant longevity. Previous studies have shown that, in macrophages, Co2+, Cr3+, and Ni2+ can activate the NLR family pyrin domain-containing protein 3 (NLPR3) inflammasome, which is responsible for interleukin(IL)-1β production through caspase-1. Furthermore, these ions are known to induce oxidative stress, and inflammasome priming is known to involve nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling. However, the mechanisms of inflammasome activation by metal ions remain largely unknown. The objectives of this thesis were to determine if, in macrophages: 1. IL-1β release induced by metal ions is caspase-1-dependent; 2. caspase-1 activation and IL-1β release induced by metal ions are oxidative stress-dependent; and 3. IL-1β release induced by metal ions is NF-κB signaling pathway-dependent. Lipopolysaccharide (LPS)-primed murine bone-marrow-derived macrophages were exposed to Co2+, Cr3+, or Ni2+, with or without an inhibitor of caspase-1, oxidative stress, or NF-κB. Culture supernatants were analyzed for active caspase-1 (immunoblotting) and/or IL-1β (ELISA). Overall, results showed that while both Cr3+ and Ni2+ may be inducing inflammasome activation, Cr3+ is likely a more potent activator, acting through oxidative stress and the NF-κB signaling pathway. Further elucidation of the activation mechanisms may facilitate the development of therapeutic approaches to modulate the inflammatory response to metal ions, and thereby increase implant longevity.
6
Liu, Chang. "Metal ions removal from polluted waters by sorption onto exhausted coffee waste. Application to metal finishing industries wastewater treatment." Doctoral thesis, Universitat de Girona, 2014. http://hdl.handle.net/10803/283705.
Abstract:
A new technology for Cr(VI) and divalent metal ions removal based on metal sorption onto exhausted coffee waste has been developed. Physical and chemical characterization of exhausted coffee waste was explored as well as the role of structural and non structural compounds of the waste in metal ions sorption. Kinetics of Cr(VI) sorption from binary mixtures containing different Cr(VI) and Cu(II) molar ratios were carried out in a batch reactor. A synergistic effect of Cu(II) in Cr(VI) reduction and sorption was found. From the kinetic sets of data a kinetic model taking into account Cr(VI) reduction/sorption, reduced Cr(III) sorption and Cu(II)synergistic effect on sorption was developed. The model described quite accurately the overall process of Cr(VI) removal. Biosorption by coffee wastes followed by precipitation resulted to be an efficient and low cost technology to remove Cr(VI) and divalent metals from synthetic and industrial effluents from metal finishing industriesS'ha desenvolupat una tecnologia nova per a l'eliminació de Cr(VI) i metalls divalents basada en l'adsorció dels metalls en residus de marro de café. Es va dur a terme la caracterització físicoquímica del marro de café i es va investigar el paper dels components estructurals i no estructurals en l'adsorció de metalls. Emprant un tanc agitat es va estudiar la cinètica d'adsorció de Cr(VI) de mescles binàries de Cr(VI)-Cu(II) amb diferents relacions molars d'ambdos metalls. Es va trobar un efecte sinèrgic del coure sobre l'adsorció i la reducció de Cr(VI). Un model basat en la reducció/adsorció de Cr(VI), adsorció del Cr(III) format i l'efecte sinèrgic del coure va ser desenvolupat. El model va descriure adequadament el procés. La bioadsorció seguida de precipitació va resultar ser una tecnologia eficaç i de baix cost per eliminar Cr(VI) i metalls divalents d'aigües sintètiques i efluents d’indústries de tractament de superfícies
7
Brännvall, Mathias. "Metal ion cooperativity in Escherichia coli RNase P RNA." Doctoral thesis, Uppsala universitet, Institutionen för cell- och molekylärbiologi, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-2056.
Abstract:
RNase P is an essential ribonuclease responsible for removal of the 5’ leader of tRNA precursors. Bacterial RNase P consists of an RNA subunit and a small basic protein. The catalytic activity is associated with the RNA subunit, i.e. bacterial RNase P RNA is a ribozyme. The protein subunit is, however, essential for activity in vivo. RNase P RNA, as well as the holoenzyme, requires the presence of divalent metal ions for activity. The aim of this thesis was to increase our understanding of the catalytic mechanism of RNase P RNA mediated cleavage. The importance of the nucleotides close to the cleavage site and the roles of divalent metal ions in RNase P RNA-catalyzed reaction were investigated. Escherichia coli RNase P RNA (M1 RNA) was used as a model system. It was shown that different metal ions have differential effects on cleavage site recognition. Cleavage activity was rescued by mixing metal ions that do not promote cleavage activity by themselves. This suggests that efficient and correct cleavage is the result of metal ion cooperativity in the RNase P RNA-mediated cleavage reaction. The results suggested that one of the metal ions involved in this cooperativity is positioned in the vicinity of a well-known interaction between RNase P RNA and its substrate. Based on my studies on how different metal ions bind to RNA and influence its activity we raise the interesting possibility that the activity of biocatalysts that depend on RNA for activity are up- or downregulated depending on the intracellular concentrations of the bulk biological metal ions Mg2+ and Ca2+. The nucleotides upstream of the cleavage site in the substrate were found to influence the cleavage efficiency. This was not exclusively due to intermolecular base pairing within the substrate but also dependent on the identities of the nucleotides at position –2 and –1. The strength of the base pair at position –1/+73 was demonstrated to affect cleavage efficiency. These observations are in keeping with previous suggestion that the nucleotides close to the cleavage site are important for RNase P cleavage. We conclude that the residue at -1 is a positive determinant for cleavage by RNase P. Hence, my studies extend our understanding of the RNase P cleavage site recognition process.
8
Xiao, Lan. "Etude physico-chimique de la complexation de divers ions metalliques (cu**(2+), ni**(2+) et co**(2+)) avec des dipeptides l-l contenant des chaines laterales non-coordinantes." Paris 7, 1988. http://www.theses.fr/1988PA077170.
Abstract:
Stabilite des complexes en fonction de l'interaction des chaines laterales du dipeptide et le solvant. Mesures potentiometriques calorimetriques, caracterisation spectrometrique et structure moleculaire
9
Sahmoune, Amar. "Extractions synergiques de metaux divalents de transition par association d'une acyl-4-pyrazolone-5 avec des polyethers cycliques et acycliques." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13116.
Abstract:
Extractions de co. Zu. Cd et cu divalents par les melanges phenyl-1 methyl-3 benzoyl-4 pyrazolone-5 ethers crown. La coextraction alcalins-alcalinoterreux complexes par les composes crown et des metaux divalents est possible quand la taille de la cavite de l'ether-crown est voisine de celle de l'alcalin (ou alcalino-terreux) et quand l'ion ml::(3)**(-) est suffisamment stable
10
Dearden, David Vernell Beauchamp Jesse L. Beauchamp Jesse L. "Experimental probes of gas phase ions and molecules : I. Product kinetic energy release measurements as a probe of reaction thermochemistry, dynamics, and chemical structure in systems containing transition metal ions. II. Photoelectron and optical studies of organic transient species /." Diss., Pasadena, Calif. : California Institute of Technology, 1989. http://resolver.caltech.edu/CaltechETD:etd-02082007-130036.
11
Diantouba, Bertin Aimé. "Effets structuraux des acyl-4-pyrazolones-5 dans l'extraction liquide-liquide des cations metalliques divalents." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13093.
Abstract:
Etude de l'effet de l'acidite de la lipophilie et effets structuraux des acyl-4 pyrazolones-5 dans l'extraction de cu, co, zu et pb divalents. Extraction de 3 types de complexes metalliques : mononucleaires de type m(l-n-lh)::(2) ou m(l-n-l) et polynucleaires (m(l-n-l))::(j). Meilleures possibilites des bis-acyl-4 pyrazolones-5
12
Navick, Caldentey Martine. "Contribution à l'étude des phénomènes de synergie en extraction liquide-liquide : application à l'extraction du nickel(II) et du cobalt(II) en milieu acide." Paris 6, 1986. http://www.theses.fr/1986PA066297.
Abstract:
Etude des propriétés d'agent d'extraction des acides di(alkyl)dithiophosphoriques ; ils ne peuvent pas être utilisés industriellement car ils s'hydrolysent rapidement au contact d'une phase aqueuse des 35**(o). En fait il semble que les anions di(alkyl) monothiophosphoriques conviennent, utilises en même temps qu'une oxime. Effet de divers facteurs sur la cinétique d'extraction. On peut séparer à ph1, ni et co par une extraction par acide di(ethyl)monothiophosphorique et quinoleinols-8 substitués.
13
Fichou, Denis. "L'interface oxyde de zinc/électrolyte : étude des processus primaires." Paris 6, 1986. http://www.theses.fr/1986PA066259.
14
LAKKIS, ZAHREDDINE ZEINAB. "Aspects thermodynamiques et cinetiques de l'extraction de metaux divalents par des acyl-4-pyrazolones-5." Strasbourg 1, 1986. http://www.theses.fr/1986STR13001.
Abstract:
Extraction de cd et zn a partir des milieux aqueux, perchlorate, nitrate et sulfate par des melanges de phenyl-1 methyl-3 benzoyl-4 pyrazolone-5 et de sels d'ammonium lipophiles. Le pyrazolonate de nh::(4) est l'agent reel de synergie. Mecanisme de transport de cuivre par des acyl-4 pyrazolones-5 a travers une membrane liquide epaisse
15
Vasconcelos, Glenda Lara Lopes. "Efeito das pastilhas higienizadoras efervescentes à base de peróxido alcalino em liga metálica de cobalto-cromo." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/58/58131/tde-15032016-162731/.
Abstract:
A higienização das próteses é de fundamental importância para a longevidade do tratamento reabilitador. Entretanto, é necessário analisar os efeitos que os higienizadores podem causar nas superfícies que compõem uma prótese. Deste modo, o objetivo deste estudo foi avaliar os efeitos de pastilhas efervescentes à base de peróxido alcalino em liga de cobalto cromo (Co-Cr), utilizada em Prótese Parcial Removível (PPR). A partir de uma matriz metálica, padrões de cera em forma de disco (12 mm x 3 mm) foram confeccionados para posterior fundição. Os espécimes metálicos (n=16) foram imersos nas soluções: água deionizada (controle), Polident 3 minutes®, Steradent®, Efferdent®, Polident for Partials® e Corega Tabs®. Foi realizada a análise da rugosidade (n=10) por meio de rugosímetro, antes (t0) e após 5 períodos de simulação de ½, 1, 2, 3, 4 e 5 anos de imersão nos higienizadores. Foram realizadas análises complementares quantitativas da liberação de íons (n=5) de cobalto (Co), cromo (Cr) e molibdênio (Mo) em cada solução e análises qualitativas em um espécime de cada grupo, por meio de Microscopia Eletrônica de Varredura (MEV) e Espectrometria de Energia Dispersiva de Raios X (EDS). A distribuição dos dados de rugosidade (μm) apresentou-se não normal. Foi utilizada estatística não-paramétrica (α=0,05). Tanto para o fator solução (Kruskall Wallis, ½ ano (p=0,900), 1 ano (p=0,277), 2 anos (p=0,227), 3 anos (p=0,086), 4 anos (p=0,657) e 5 anos (p=0,856), como para o fator tempo (Friedman, p=0,137) não houve diferença significante. Com relação à liberação de íons (μg/L), a distribuição dos dados apresentou-se normal. De acordo com a estatística (α=0,05, ANOVA e teste de Tukey), Corega Tabs®, Efferdent® e água deionizada promoveram maior liberação de íons Co do que o Steradent® (p=0,003). Quanto aos íons Cr (p=0,000), Corega Tabs® propiciou maior liberação quando comparado a água deionizada, Steradent® e Polident 3 minutes®. Em relação aos íons Mo (p=0,001), o Efferdent® promoveu maior liberação. No MEV pode-se verificar que as soluções não apresentaram efeitos deletérios sobre as superfícies. Conclui-se que todas as pastilhas avaliadas não ocasionaram danos, entretanto, Steradent® foi a que propiciou menor liberação de íons, sendo indicada com maior segurança para higienização de superfícies metálicas de PPR.The hygiene care of the removable dentures is of most importance for the longevity of the rehabilitation treatment. However, it is necessary to analyze the effects that denture cleansers can cause on the surfaces of prosthesis. Thus, the aim of this study was to evaluate the effect of alkaline peroxide-effervescent tablets on the surfaces of the cobalt-chromium alloys (Co-Cr), used in removable partial dentures (RPD). Circular specimens (12 mm x 3 mm) were fabricated with cobalt-chromium alloys. The specimens (n= 16) were immersed in the following solutions: deionized water (control), Polident 3 minutes™, Steradent™, Efferdent™, Polident for Partials™ and Corega Tabs™. The surface roughness (n=10) was analyzed with a surf-test analyzer, before and after 5 periods that corresponds to the simulation of ½, 1, 2, 3, 4 and 5 years of immersion in the cleansers. As complementary analysis, it was performed a quantitative study of ions release (n=5) for cobalt (Co), chromium (Cr) and molybdenum (Mo) in each solution and qualitative analysis with scanning electron microscopy (SEM) associated to Energy-dispersive X-ray spectroscopy (EDS). The results of surface roughness had presented no normal. In nonparametric statistics (α = 0.05), both of the solution factor Kruskall Wallis, ½ year (p=0.900), 1 year (p=0.277), 2 years (p=0.227), 3 years (p=0.086), 4 years (p=0.657) and 5 years (p=0.856), such as time factor (Friedman, p = 0.137), there was no significant difference. The results of ionic release presented a normal distribution and they were submitted to ANOVA (p=0.05) and Tukey test. The solutions Corega Tabs®, Efferdent® and deionized water presented greater Co ionic release than Steradent® (p=0.003). For Cr ions (p=0.000), Corega Tabs® had greater ionic release than deionized water, Steradent® and Polident 3 minutes®. Regarding Mo ions (p=0.001), Efferdent® showed greater release. With SEM, it was possible to verify that the solutions showed no deleterious effects on the specimen surfaces. It was concluded that no deleterious effects on metal surface was caused, however, Steradent® presented the smallest ionic release, and can be indicated more safely for cleaning metal surfaces of RPD.
16
Ben, Nasr Chérif. "Complexation du nickel (II) et des lanthanides (III) par des phosphoramides bidentes : Application à l'extraction liquide-liquide." Nancy 1, 1986. http://www.theses.fr/1986NAN10032.
Abstract:
Les composés de type (NME::(2))::(2)P(O)NRP(O)(NME::(2))::(2) complexent fortement lésions métalliques et peuvent être utilisés en tant qu'agents extractaires dans l'extraction liquide liquide. Synthèse systématique des complexes lanthanides-NDA. L'étude RMN a permis également de trier les contributions de contact et de pseudo-contact au déplacement paramagnétique des protons et des phosphores du ligand engagé dans le complexe et d'obtenir des informations concernant la structure des complexes en solution. Enfin, le problème de l'extraction liquide-liquide des lanthanides par le NIPA dans le nitrométhane a été abordé. Les résultats obtenus ont révélé que le NIPA est un excellent agent extractant, notamment en milieu nitrique, et que l'efficacité de l'extraction augmente quand le rayon atomique diminue
17
Senapati, Bhagyashree. "Biophysical and Catalytic Characterization of Gpx7 in Presence Divalent Metal Ions." Thesis, 2015. http://ethesis.nitrkl.ac.in/7228/1/Biophysical_Senapati_2015.pdf.
Abstract:
Glutathione peroxidase (GPx) is a family of proteins found in biological systems. The protein family is known to detoxicate the system by scavenging reactive oxygen species, formed upon interaction of the system with external moieties or stress conditions or normally synthesized during metabolism of the system. Out of all members of the family, GPx4 and 7 stand alone because of their action on lipid peroxides. GPx4 and 7 are known to reduce lipid peroxides present in lipid membrane into respective lipid alcohol, hence saving the membrane from depolarization. Besides GPx7, other proteins (GPx1-6) of the family are very much known to scientific community. Hence, the underlying mechanism of detoxification by GPx7 is under the scientific scanner. To this end, the thesis has employed extensive in silico studies to draw a picture of GPx-7 relations with other proteins of the family, and the possible catalysis efficiency of the protein in presence of different metal ions. In addition, in vitro studies (partially) started to validate the catalysis findings from in silico studies. The in silico findings indicate that cysteine has been re-favored over selenocysteine residue during the evolutionary development of proteins in the family. In addition, the protein share relatively higher propensity for the non-polar environment than other proteins of the family. On catalysis efficiency of the protein, GPx-7 has highest affinity for lipid peroxide in presence of Ca2+ ions, and least in presence of Se2+ . However, the protein loses its affinity for lipid peroxide in presence of Mg2+ or Fe2+ ions.
18
Thuy, Nguyen Thi Dieu, and 阮妙翠. "Solution equilibria of complex formation between caffeic acid, dihydrocaffeic acid and divalent metal ions." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/52211824435701487927.
Abstract:
碩士國立臺灣科技大學
化學工程系
103
The solution equilibria between chelating agents (caffeic acid – CA or dihydrocaffeic acid – DCA) and several divalent metal ions (Cu2+, Zn2+, Ni2+, Co2+ and Mn2+) in binary and ternary systems were investigated in this work. The potentiometric measurement was carried out at 37oC and ionic strength 0.15 mol.dm-3 NaCl in order to determine the protonation and formation constants of complexes. The complexation model and speciation diagram were established by computer programs Hyperquad2008 and HySS, respectively. Moreover, UV – Vis spectrophotometry was performed to explore the reliable protonation constants of these ligands and qualitatively confirm the complex formation. In both binary and ternary systems, the stability constant values of formed metal – chelator complexes decrease in the following order: Cu2+ > Zn2+ > Ni2+ > Co2+ > Mn2+. The complex formation between metal ion and DCA system is more stable than metal ion and CA system. In addition, the tendency of complex in the ternary system was revealed and evaluated by calculating the relative stability constant ( ) and the disproportionate constant (log X). Besides, at physiological pH, the sequestering ability of CA and DCA followed the order pL0.5 (Cu2+) > pL0.5 (Zn2+) > pL0.5 (Ni2+) > pL0.5 (Co2+)> pL0.5 (Mn2+).
19
NGUYEN, LOC QUANG, and 阮光祿. "Effects of Divalent Metal Ions on the Activity of Recombinant Drosophila Melanogaster Tyrosylprotein Sulfotransferase." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/t2eg64.
Abstract:
碩士國立交通大學
生物科技學系
107
Protein tyrosine sulfation (PTS) is a common post-translational modification. 875 among 4256 proteins have been identified to undergo the PTS on their tyrosine residues. Tyrosylprotein sulfotransferase (TPST; Enzyme Commission number: 2.8.2.20) is the type II trans-Golgi membrane enzyme responsible for the PTS, delineating the transfer of the sulfonate group (SO3)- to specific tyrosine residues in target peptides/proteins to form O-sulfation compound. The sulfation activity plays essential roles in pathogen infection, hemostasis and protein–protein interactions. In order to understand the importance of PTS and tyrosine-sulfated proteins in the life biology, the preparation and characterization of TPST is crucial. In this thesis, Escherichia coli BL21(DE3) was used to produce the recombinant of rat phenol sulfotransferase (PST) and Drosophila melanogaster TPST (TPST), and they were purified to more than 95% homogeneity. The TPST sulfation on small P-selectin glycoprotein ligand-1 peptide (PSGL-1, ATEYEYLDYDFL) affected by five divalent metal ions: calcium (Ca2+), cobalt (Co2+), magnesium (Mg2+), manganese (Mn2+) and zinc (Zn2+) at pH 6.5 and 37oC was determined by phenol sulfotransferase–tyrosylprotein sulfotransferase (PST-TPST) coupled enzyme system through two assays. The former was enzyme-linked immunosorbent assay (ELISA)-based detection on the preparation of sulfated protein at A450 nm. The latter was based on continuously increasing fluorescence of 4-methylumbilliferone (MU) signal. Typically, one liter of Luria−Bertani (LB) broth purified through the His-Trap affinity column with only one chromatography step produced 14.2 mg TPST, its specific activity: 0.350 A450/min/mg or 7.87 nmole/min/mg. Besides, all of the metal cations enhanced the binding ability of PSGL-1 towards TPST, their Km values lower than apo-TPST. Only Zn2+ strongly inhibited the TPST activity, the IC50: 40-50 µM, whereas the other metals enhanced the sulfation activity. The catalytic efficiency of TPST was risen up to 3-fold with the assistance of Ca2+ and Co2+. Together with the available structures of human TPST, this research proposed specific linking interactions between metal-enhancer or metal-inhibitor with amino-acid residues of TPST. This thesis is facilitating the deeper understanding of TPST, which expands more aspects on the PTS regulation.
20
Hung, Hui Chih, and 洪慧芝. "The inhibitory effect of divalent metal ions on human placental alkaline phosphatase in reverse micelles." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/49724713477618096479.
Abstract:
碩士國防醫學院
生物化學研究所
83
Human placental alkaline phosphatase (EC 3. 1. 3. 1.) is an integral membrane protein; catalyzing the hydrolysis of phosphoester linkage of a broad range substrate. It is a dimeric metalloprotein possessing two zinc atoms and a magnesium atom at eath active site. In aqueous solution, Mg2+ was found to be a nonessential activator for the enzyme. We have embedded human placental alkaline phosphatase in a reverse micellar system prepared by dissolving sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in isooctane. Protein molecules embedded in reverse micelles behave much as if they are anchored in a membranous structure and may represent the enzyme properties in vivo. In this study we examine the effects of metal ions on human placental alkaline phosphatase in the reverse micellar system. In our experiments, we found the Mg2+, which is an activator for the enzyme in aqueous solution, acts as an inhibitor in the reverse micellar system. The inhibition was due to a time-dependent isomerization of the enzyme molecule, which resulted in the recorder tracing in the enzyme assays became curvature. The Mg2+-induced enzyme isomerization was occurred only for the Mg2+-bound enzyme form and completely prevented by phosphate and partially reversed by EDTA. Other divalent metal ions such as Ca2+ caused similar effect. Cu2+ at 0.6 mM has no effect on the enzyme activity in aqueous solution, but strongly inhibits the enzyme activities in reverse micelles. High concentration of Zn2+ also strongly inhibited the enzyme activity in both aqueous and reverse micellar solvent systems presumably by occupying the Mg2+ (M3) site. However, binding of Zn2+ at the M3 site did not cause enzyme isomerization and the enzyme assay tracing was linear. The M3 site of the enzyme was proposed to have a regulatory role in vivo with magnesium ion as the modulator.
21
Lee, Nung, and 李儂. "Electrochemical Behaviors of Divalent Metal Ions and Nanoporous Activated Carbon Electrodes in Capacitive Deionization Process." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/34218001253688825604.
Abstract:
碩士國立臺灣大學
環境工程學研究所
104
Capacitive deionization (CDI) is a novel water purification technology for the removal of ions with the features of low-energy consumption, no membrane component, no secondary waste, and easy regeneration of electrodes (Anderson et al. 2010). The working principle of the CDI system is to apply an external electric field on a pair of porous carbon electrodes, and thereby ions can be electrostatically captured onto the oppositely charged electrode surface. Notably, our previous study reported that copper ions can be effectively removed from solutions by electrosorption and electrodeposition(Huang et al. 2014). The removal mechanism has a dependency on the amplitude of applying electric voltage. However, researches related to heavy metals removal with CDI technology are still limited. The main object of this study is to give a fundamental aspect of heavy metal removal in CDI process using activated carbon electrodes. Divalent heavy metals with different reduction potentials are selected, including Cu2+, Zn2+, and Ca2+, for the following experiments: electrochemical characterization and CDI tests. Cyclic voltammetry and electrochemical impedance spectra measurements were carried out to clarify the physicochemical properties of divalent metal ions in aqueous solution. A batch-mode CDI cell was performed at an applied voltage of 1.2 V to remove divalent heavy metal ions at 1 mM. After the CDI process, the electrode surfaces are further analyzed by Scanning Electron Microscope, Energy Dispersive Spectromete, X-ray Photoelectron Spectroscopy, for determining the removal characteristics of divalent heavy metals onto the carbon electrodes. According to the results, the divalent heavy metals can be successfully removed by CDI process. The removal mechanism is not only by electrosorption of electrical double-layer charging, but also by the electrodeposition of reduction of metals onto the electrode surface. More specifically, the reduction potential of divalent heavy metals plays an important role to determine their electrochemical behaviours during the CDI process. For example, Zn2+ ions with a lower reduction potential (Zn2+ /Zn, E0= −0.76 V) are mainly removed by electrosorption, which is further confirmed by depolarizing the electrode. In contrast, Cu2+ ions, possessing a high reduction potential (Cu2+ /Cu, E0= +0.34 V), have a tendency to be reduced to be cuprous oxide in CDI. The electrodeposition of Cu2+ ions on the electrode surface are also observed by Scanning Electron Microscope, Energy Dispersive Spectromete, X-ray Photoelectron Spectroscopy. Furthermore, the removal selectivity is studied by a mixture of Zn2+ and Cu2+ ions to investigate the competition between different divalent ions. As evidenced, Cu2+ ions are preferred to be separated from water than Zn2+ ions. The research findings can provide useful information to understand the removal characteristics of different heavy metals with CDI technology for water purification and wastewater treatment.
22
Yoshida, Aiichiro. "Catalytic mechanism of the tetrahymena ribozyme : the role of divalent metal ions in the catalysis /." 2000. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:9965041.
23
Poyner, Russell R. "The role of divalent metal ions in the reaction catalyzed by yeast enolase a spectroscopic study /." 1993. http://catalog.hathitrust.org/api/volumes/oclc/31403479.html.
24
Shou-YunLu and 盧守筠. "Site-Directed Mutagenesis Studies on the Divalent Metal Ions Binding Site of Rat Lens αB-Crystallin." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/fwjydk.
Abstract:
博士國立成功大學
化學系
102
The lens αB-crystallin, playing a major role in maintaining the transparency of the eye lens, possesses chaperone-like function to prevent the lens proteins from aggregation due to foreign stress and/or aging. In nonlenticular cells, it is involved in various neurological diseases, diabetes, and cancer. The role of some metal ions in the αB-crystallin biology has been reported. Theoretical calculations have proposed that the coordination site of human αB-crystallin for binding divalent metal ions were His101, His119, Lys121, His18 and Glu99. In this study, H18G, H119G, and H101G mutant types of rat lens αB-crystalin were cloned and expressed to investigate whether His18, His119 and His101 are the coordination binding sites. And the results suggested that His18, His119 and His101 were the crucial binding sites for Cu (II) and Zn (II) in terms of chaperone-like activity and structure. Copper and zinc at 1 mM concentration significantly increase the chaperone-like activity in wild type αB-crystalin, whereas zinc, copper and magnesium at 1 mM reduced the activity of mutant type significantly. ANS fluorescence measurement showed that there was no linear relationship between chaperone-like activity and surface hydrophobicity, indicating that surface hydrophobicity is not prerequisite for exhibiting chaperone-like activity. Both the Far- and Near-UV CD spectra suggested that the wild type reflected more β-sheet structural characteristics; whereas the mutant type reflected more random coil characteristics and more micro-environmental changes around the tryptophan residues. The results from chaperone-like activity, ANS fluorescence measurement and Far- and Near-UV CD studies indicate that the replacement of His18, His119 and His101 with Glycine resulted in a conformational and minor environmental changes that decrease chaperone-like activity in the presence of divalent ions suggested that His18, His119 and His101 were a crucial binding site for Cu (II) and Zn (II), respectively. All results together suggest that His18, His119 and His101 coordinate each other for the binding site of Cu (II) and Zn (II) in terms of improving the chaperone-like activity and stability of crystallin/metal ion complex, which further confirmed the proposed binding site based on the theoretical calculation.
25
Santos, Ariana Coelho Ferreira dos. "The solid products of L−arginine and divalent metal ions – synthesis, physicochemical characterization and biological properties." Master's thesis, 2020. http://hdl.handle.net/10316/93928.
Abstract:
Dissertação de Mestrado em Química Medicinal apresentada à Faculdade de Ciências e TecnologiaDois dos grandes objetivos em Química Medicinal são sintetizar novos fármacos e aumentar a qualidade/potência dos que já se encontram comercialmente disponíveis, ao mesmo tempo que se pretende diminuir os efeitos secundários. Visto que, ao longo dos anos, os compostos de coordenação têm mostrado, de forma geral, propriedades biológicas bastante melhoradas em relação à molécula livre de origem, o trabalho apresentado na presente dissertação focou-se na síntese desses mesmos compostos.Neste sentido, tentou-se sintetizar novos complexos metálicos contendo cálcio(II), magnésio(II), cobre(II) e zinco(II) como átomos metálicos centrais. Apenas com o cobre(II) se conseguiu obter, com sucesso, oito compostos de coordenação. Por sua vez, como ligandos recorreu-se ao uso da L−arginina (por se tratar de um aminoácido importante em diferentes processos biológicos), bem como aos iões SCN− e N3−, por serem quimicamente muito idênticos. O recurso a estes aniões teve como objetivo perceber qual o efeito estrutural dos mesmos nos complexos metálicos, isto é, se apenas serviriam como contra-ião para balançar a carga positiva proveniente do catião [metal:L−arginina] ou se também eram capazes de coordenar com o ião metálico central e, consequentemente, originar compostos de coordenação com geometrias diversas e únicas.Todos os mono-cristais dos compostos sintetizados {[Cu(L−arg)2](NO3)2•3H2O}n (1), [Cu(L−arg)2(SCN)2]•2H2O (2), [Cu(L−arg)(SCN)2] (3), [Cu(L−arg)2(N3)2][Cu(L−arg)2Cl](N3)•7H2O (4), {[Cu2(L−arg)2(N3)2(µ−1,3−N3)(µ−1,1−N3)][Cu(L−arg)(N3)(µ−1,1−N3)]•3H2O}n (5), [Cu(L−arg)2(N3)2][Cu(L−arg)2(N3)](N3)•6H2O (6), [Cu(L−arg)2(H2O)2](N3)2 (7) e {[Cu(L−arg)(N3)(µ−1,3−N3)]}n (8), foram obtidos a partir de soluções aquosas através da cristalização lenta. A morfologia, bem como as cores de cada cristal, foram únicas para cada complexo metálico. Todos os complexos metálicos foram caracterizados por cristalografia de raios-X de cristal e de pó e por espectroscopia de infravermelho, concluindo se que a estrutura cristalina dos produtos 1 e 3 já tinha sido resolvida, ao passo que todas as restantes foram resolvidas pela primeira vez.Uma vez que os iões cobre(II) apresentam propriedades paramagnéticas, foram realizados estudos magnométricos para todos os complexos metálicos (T = 1.8−300 K), exceto para os produtos 1 e 3, que já se encontravam descritos na literatura, e para o produto 5, por não haver uma quantidade de material suficiente. Estes estudos tiveram como objetivo poder estabelecer uma correlação magneto-estrutural. Apenas o produto 8, cujos mono-cristais obtidos eram esverdeados, mostrou ter interações ferromagnéticas residuais, isto é, abaixo de uma certa temperatura, os momentos magnéticos atómicos tenderam em alinhar-se na mesma direção. Todos os restantes (produtos 2, 4, 6 e 7) mostraram ter um comportamento normal de paramagnetismo, ou seja, na presença de um campo magnético externo, os iões metálicos paramagnéticos ficaram magnetizados.Finalmente, a atividade antimicrobiana da maioria dos compostos foi avaliada contra várias estirpes de leveduras e fungos filamentosos (Candida albicans, Candida tropicalis, Trichophyton mentagrophytes, Microsporum gypseum e Epidermophyton floccosum) e contra as bactérias Escherichia coli e Staphylococcus aureus. Todos os produtos mostraram uma forte atividade inibitória contra os dermatófitos. Em particular, sublinha-se a atividade dos compostos 3, 7 e 8 que apresentaram um melhor valor de MIC relativamente ao fármaco de referência (Fluconazole). Todos os produtos não apresentaram atividade contra as leveduras e bactérias no intervalo de concentrações testadas.
Two of the biggest purposes in Medicinal Chemistry are to synthetize new drugs or to increase the quality/potency of the ones that are commercially available, while limiting side effects. The present work focused on the synthesis of new coordination compounds. Over the years, metal-based compounds have shown, in general, noteworthy improved biological activities comparing to the parent standalone drug. In this endeavor, it was attempted the synthesis of new metal complexes with calcium(II), magnesium(II), copper(II) and zinc(II) ions as the central metal atoms. Eight coordination compounds were successfully synthesized from the copper(II) salts. Besides L−arginine (an important amino acid involved in several biological functions), the chemically alike SCN− and N3−ions were used as ligands in order to understand its structural effect in the metal complex, i.e. whether they would serve only as counterions to balance the positive charge of [metal−L−arginine] cations, or if they were also able to coordinate with the metal ion and consequently originate coordination compounds with diverse and unique geometries.All of the single-crystals of all the obtained products, {[Cu(L−arg)2](NO3)2•3H2O}n (1), [Cu(L−arg)2(SCN)2]•2H2O (2), [Cu(L−arg)(SCN)2] (3), [Cu(L−arg)2(N3)2][Cu(L−arg)2Cl](N3)•7H2O (4), {[Cu2(L−arg)2(N3)2(µ−1,3−N3)(µ−1,1−N3)][Cu(L−arg)(N3)(µ−1,1−N3)]•3H2O}n (5), [Cu(L−arg)2(N3)2][Cu(L−arg)2(N3)](N3)•6H2O (6), [Cu(L−arg)2(H2O)2](N3)2 (7) and {[Cu(L−arg)(N3)(µ−1,3−N3)]}n (8) were synthetized by slow crystallization from aqueous solutions. The morphology and color of the synthesized crystals were unique for each metal complex. The metal complexes were characterized by the means of single-crystal and powdered X-ray crystallography and infrared spectroscopy. The single-crystal structure of products 1 and 3 has already been solved, whereas for the remaining products were solved for the first time.Due to the paramagnetic properties of copper(II) ions, and to establish a magneto-structural correlation, magnetic studies for all the metal complexes (T = 1.8−300 K) were also carried out, except for products 1 and 3 (already described in literature) and for product 5 (as a result of low quantity of material). Only product 8, with greenish single-crystals showed weak ferromagnetic interactions, i.e. below a certain temperature, the atomic magnetic moments tended to line up in a common direction. The others (products 2, 4, 6 and 7) presented the normal behavior of a paramagnetic specie, i.e. when exposed to an external magnetic field, the paramagnetic ions acquired a small magnetization.Finally, the antimicrobial activity of the majority of the products was evaluated against Candida albicans, Candida tropicalis, Trichophyton mentagrophytes, Microsporum gypseum and Epidermophyton floccosum (fungi strains) and against Escherichia coli and Staphylococcus aureus (bacteria strains). All the products showed strong activity against dermatophytes. In particular products 3, 7 and 8 are highlighted for a much better MIC value comparing to the standard drug (Fluconazole). The tested products did not show activity against yeasts or bacteria in the tested concentrations.
26
Latwesen, David Gary. "Spectroscoptic characterization of the first coordination sphere of divalent metal ions at the active sites of enzymes." 1992. http://catalog.hathitrust.org/api/volumes/oclc/28161086.html.
27
Chih-Yuan and 王志元. "Effect of home bleaching treatment on metal ions release from stainless steel orthodontic brackets." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/42875691061941695881.
Abstract:
碩士中山醫學大學
口腔材料科學研究所
95
This study was to evaluate the effect of home bleaching treatment on metal ions release from stainless steel orthodontic brackets, including 3M Unitek, Dentaurum, and Tomy. Six different bleaching treatments were used in this study. The amounts of iron, chromium, and nickel ions release from brackets were detected by inductively coupled plasma mass spectrometry. A scanning electron microscope and an atomic force microscopy were used to analyze the surface morphology and roughness, respectively. Results showed that the bleaching treatment and the bracket brand had a statistically significant influence on metal ions release (p<0.0001). Among the tested brackets, Tomy bracket treated with 10% H2O2 had the highest iron and nickel ions release, 3M Unitek bracket treated with 10% H2O2 had the highest chromium ions release. However, the amounts of the released metal ions were still below the critical value to induce a biological negative effect. Different surface topography was present among the tested brackets. The difference in surface topography with bleaching treatment did not correspond with metal ions release.
28
蘇偉廷. "The effects of divalent metal ions on oxidoreduction and nitroreduction of the NAD(P)H:flavin oxidoreductase (HP0642) from Helicobacter pylori." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/02372507332326871744.
Abstract:
碩士國立清華大學
生物科技研究所
100
In the previous study, the recombinant HP0642 protein which obtained from gene expression in E. coli SG13009 system has two majority functions as NAD(P)H electron donor dependent NAD(P)H-flavin oxidoreductase and the same electron donor dependent nitroreductase. In the previous study, it was found that the oxidoreductase activity of recHP0642 was inhibited by 1 mM Zn2+ or Hg2+ when NADH as electron donor. And the nitroreductase activity of recHP0642 was inhibited by 5 mM Zn2+ and Fe2+ when NADPH as electron donor. But the Cu2+ could make the nitroreductase activity increase. The NADH:flavin oxidoreductase activity could be monitored by the decrease of the absorbance of NADH at 340 nm. The Km value is 4.3 μM, the Vmax is 303.00 μM min-1 mg-1 in this study (Fig. 1). The divalent metal ion, including Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Cu2+, and Zn2+, were used to observe the effect on oxidoreductase activity for recHP0642 protein. The Mg2+, Mn2+, and Zn2+ at 1.6 mM could inhibit the activity down to 79.22, 74.18, and 39.39% relative to metal-free control group. Among the range at 0.2~1.6 mM, the Ca2+, Co2+, Ni2+, and Cu2+ performed no obvious effects on the activity. At the relative high concentration 2~16 mM, Cu2+, Mn2+, and Co2+ could inhibit the activity down to 50% relative to metal-free control group at least. At 16 mM, the remaining activity order of oxidoreductase of HP0642 protein is as follows: Cu2+ (15.07%), Mn2+ (41.83%), Co2+ (48.96%), Zn2+ (55.73%), Ni2+ (62.50%), Mg2+ (73.37%), and Ca2+ (97.78%) (Fig. 2). The nitroreductase activity of HP0642 protein was monitored by the decrease of the absorbance of Nitrofurazone and Nitrofuratoin at 400 or 420 nm respectively. The Km value is 161.29 μM, the Vmax is 1428.57 μM min-1 μg-1, and the kcat value is 600.00 sec-1 in Nitrofurazone nitroreductase activity (Fig 3). The Km value is 66.73 μM, the Vmax is 384.62 μM min-1 μg-1, and the kcat value is 164.54 sec-1 in nitrofurantoin nitroreductase activity (Fig 7). The divalent metal ions which mentioned above were used to observe the nitroreductase activity for recHP0642 protein. Mg2+, Ca2+, Mn2+, Co2+, and Ni2+ at 0.2 mM could change the activity up to 107.54 %, 111.51 %, 117.06 %, 108.73 %, and 122.62 % of metal-free control level. Another tested divalent cation, Cu2+, could inhibit enzyme activity down to 64.68 % of metal-free control level at the same concentration. Zn2+ with slightly inhibition effect on nitroreductase activity, 93.65 % of metal-free control level was observed (Fig. 4). The Zn2+ showed different properties in reaction of oxidoreductase and nitroreductase activity of recHP0642, and the phenomenon should be discussed detailed in the future. Mg2+, and Ca2+ could make the nitrofurantoin nitroreductase activity up to 104.52 %, 104.40 % of metal-free control level. Mn2+, Co2+, Ni2+ and Zn2+ could be with interfered effect on nitroreductase activity down to 95.96 %, 96.08 %, 86.03% and 76.73% of metal-free control level. The Cu2+ could inhibit the nitrofuratoin nitroreductase activity completely at 0.2 mM (Fig. 8). According to this result, the concentration of Cu2+ cation was diluted 10 times to 0.02 mM. The activity was inhibited by Cu2+ down to 80.69 % of metal-free control level (Fig 9). In this study, both the reduction of nitrofurazone and nitrofuratoin was inhibited by Cu2+ with decreasing Vmax and the Km value, and it is concluded that the inhibition type of Cu2+ on nitroreductase activity of recHP0642 preotein was uncompetitive inhibition ( Fig. 5, 10)(Fig. 6, 11).
29
Santoso, Shella Permatasari, and 黎美清. "Complex Formation of 2,3-Dihydroxybenzoic Acid and N-Acetylcysteine with Divalent Metal Ions: Solution Equilibrium, Synthesis, Characterization and Biological Activity Studies." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/15565797628335710536.
Abstract:
博士國立臺灣科技大學
化學工程系
104
Solution equilibriums of 2,3-dihydroxybenzoic acid, N-acetylcysteine and divalent transition metal ions (Mn2+, Co2+, Ni2+, Zn2+, Cu2+) were investigated in this study. The equilibrium constant values of binary and ternary compounds were determined by using potentiometric method at conditions similar to that of human physiology (37°C, ionic strength = 0.15 mol•dm-3 NaCl). The refinement of potentiometric data were done by using the Hyperquad 2008 computer program. The determination of equilibrium constants was confirmed by spectrophotometric method with refinement using the HypSpec program. The binary complexes of 2,3-dihydroxybenzoic acid were found to be more stable than that of N-acetylcysteine complexes. While in ternary systems, the combination of the two ligands resulted in synergistic effect, thus producing more stable complexes. Furthermore, 2,3-dihydroxybenzoic acid binary and ternary complexes including N-acetylcysteine were synthesized and characterized by analyses such as UV-Vis and IR. The synthesized complexes were found to improve biological properties of the original ligand especially in antimicrobial activity against Staphylococcus aureus and Escherichia coli. In all complexes synthesized, binary and ternary complexes of Zn2+ gave the best antimicrobial activity and were characterized further by elemental analysis and 1H NMR. From the results structures of the synthesized binary complex and ternary complex of Zn2+ were suggested. The binary complex was formed through the binding of 2,3-dihydroxybenzoic acid hydroxyl (—O) groups while the ternary complex was formed through the binding of the same groups of 2,3-dihydroxybenzoic acid as in the binary complex and the N-acetylcysteine carboxylic group (—COO) and thiol group (—S).
30
Cuzic-Feltens, Simona [Verfasser]. "Investigation of the catalytic mechanism of RNase P : the role of divalent metal ions and functional groups important for catalysis / vorgelegt von Simona Cuzic-Feltens." 2006. http://d-nb.info/979656133/34.
31
Doyle, Colleen. "A Refined Method for Quantitation of Divalent Metal Ions in Metalloproteins and Local Stability and Conformational Heterogeneity of Amyotrophic Lateral Sclerosis-Associated Cu, Zn Superoxide Dismutase." Thesis, 2014. http://hdl.handle.net/10012/8440.
Abstract:
Amyotrophic lateral sclerosis (ALS) is a devastating and progressive disease that results in selective death of motor neurons in the cortex, brain stem and spinal cord. ALS is the most common adult onset motor neuron disease resulting in paralysis and death, commonly within 2 – 5 years of symptom onset, yet there remains no effective treatment for the disease. The majority of ALS cases show no hereditary link (referred to as sporadic ALS or sALS); however, ~10% of cases show a dominant pattern of inheritance (referred to as familial ALS or fALS). Over 170 different mutations in human Cu, Zn superoxide dismutase (SOD1) have been identified to account for ~20% of fALS. SOD1 is a ubiquitously expressed homodimeric antioxidant enzyme. It is widely accepted that mutations in SOD1 result in a gain of toxic function, rather than a loss of native function. A prominent hypothesis for the gain of function is the formation of protein aggregates, which have been shown to be toxic to motor neurons. Protein aggregation is observed in a number of neurodegenerative disorders, including Alzheimer’s, Huntington’s and Parkinson’s disease.
Each β-rich monomer of SOD1 binds one catalytic Cu ion and one structural Zn ion. The metallation state of SOD1 significantly influences the structure, dynamics, activity, stability, and aggregation propensity. A similar trend has been observed in a number of metalloenzymes and as such a method to rapidly and accurately quantitate metal ions in proteins is of great importance. Here a review of previous methods using the chromogenic chelator PAR to quantitate metal ions in proteins is presented. Three methods are assessed for their accuracy, precision and ease of use. The methods vary in accuracy, which is highest only under the specific conditions it was designed for. A robust new method is presented here that uses spectral decomposition software to accurately resolve the absorption bands of Cu and Zn with high precision. This method may be successful as a more general method for metal analysis of proteins allowing for the quantitation of additional metal combinations (e.g. Zn/Co, Ni/Cu, Ni/Co).
Thermodynamic stability has widely been implicated as playing a major role in the aggregation of globular proteins. Metal loss significantly decreases the global stability of SOD1 and as such metal-depleted (apo) forms of SOD1 have largely been the focus of SOD1 investigations. Recent studies, however, suggest that complete global unfolding is not required for protein aggregation. Local unfolding has been investigated and proposed to be sufficient to induce irreversible protein aggregation in the absence of global destabilization. Enhanced local unfolding has been observed in a number of disease-related proteins. Since SOD1 aggregation may occur from partially unfolded forms, NMR temperature dependence studies have been carried out on the most abundant form of SOD1 in vivo, the fully metallated (holo) dimer, to provide a residue specific picture of subglobal structural changes in SOD1 upon heating.
Amide proton (N1H) temperature coefficients report on the hydrogen bonding status of a protein. A curved N1H temperature dependence indicates that the proton populates an alternative conformation generally within 5 kcal/mol of the ground state. NMR temperature dependence studies of pseudoWT indicate that the thermal unfolding process of holo pWT begins with “fraying” of the structure at its periphery. In particular, increased disorder is observed in edge strands β5 and β6, as well as surrounding the zinc binding site. The local stability and conformational heterogeneity of ALS-associated mutants G93A, E100G and V148I was also assessed. All mutants display similar local unfolding patterns to pseudoWT, but also show distinct differences in the hydrogen bonding network surrounding the mutation site. Interestingly, each mutation regardless of its structural context results in altered dynamics at the β-barrel plug, a key stabilizing element in SOD1. A significant proportion of residues (~30%) access alternative states in both pseudoWT and mutants, however, overall mutants appear to be able to access higher free energy alternative states compared to pseudoWT. The implications of these results for the mechanism of protein aggregation and disease are discussed.
32
Dearden, David Vernell. "Experimental probes of gas phase ions and molecules: I. Product kinetic energy release measurements as a probe of reaction thermochemistry, dynamics, and chemical structure in systems containing transition metal ions. II. Photoelectron and optical studies of organic transient species." Thesis, 1989. https://thesis.library.caltech.edu/554/1/Dearden_dv_1989.pdf.
Abstract:
The release of kinetic energy in the decomposition of a metastable ion is a reflection of both the overall energetics and the potential energy surface on which the process takes place. Chapter 1 applies measurements of the kinetic energy release distributions (KERDs) for decomposition of metastable Mn(CO)[x][+] to the dynamics and energetics of exchange processes for the CO ligands. All the dissociations can be described by statistical phase space theory, in agreement with efficient CO exchange rates indicating that conservation of electronic spin is not important to the dynamics. A general method is presented and used whereby Mn[+]-CO bond energies are obtained from the KERDs. Chapter 2 deals with reactions of Fe[+] and Co[+] with alkanes to eliminate methane, which have KERDs narrower than predicted by statistical theory. Restriction of the angular momentum (or, equivalently, the impact parameter) to values less than those anticipated by simple ion-molecule collision theory can account for the narrowed distributions. The restrictions result from barriers in the effective potential energy surfaces and from limitations in our measurement techniques. In Chapter 3, KERDs are used to demonstrate the existence of cobaltacyclobutane[+], (hydrido)(cyclopropyl)Co[+] and Co(propene)[+] structures which do not interconvert on the µs time scale in the gas phase. Chapter 4 deals with the dehydrogenations of cyclic alkanes by Fe[+] and Co[+], and shows that, contrary to previous assumptions, statistical energy partitioning occurs in these processes.
Chapters 5 and 6 deal with studies of transient organic species. Chapter 5 presents preliminary work on charge-reversed, resonance enhanced multiphoton ionization (CRREMPI), a potentially powerful new method which exploits the special characteristics of the ion cyclotron resonance spectrometer to obtain optical spectra of a wide variety of transient species. In Chapter 6 photoelectron spectroscopy is used to observe the rearrangements of primary alkyl radicals, produced by flash vacuum pyrolysis of nitrites, to the thermodynamically more stable secondary isomers. Decomposition processes are also observe
33
Ιατρίδη, Ζαχαρούλα. "Μελέτη αποδέσμευσης ιόντων δισθενούς χαλκού από συμπολυμερή τύπου κτένας." Thesis, 2009. http://nemertes.lis.upatras.gr/jspui/handle/10889/2479.
Abstract:
Διερευνήθηκε η δέσμευση/αποδέσμευση ιόντων Cu(II) ή/και αντίθετα φορτισμένων επιφανειοδραστικών ενώσεων από συμπολυμερή τύπου κτένας. Ο κεντρικός σκελετός ήταν το πολυ(ακρυλικό νάτριο), PANa, ενώ οι πλευρικές αλυσίδες ήταν το Πολυ(Ν,Ν-διμεθυλακρυλαμίδιο) και το πολυ(Ν-Ισοπροπυλακρυλαμίδιο). Η συμπλοκοποίηση των συμπολυμερών με τα ιόντα Cu(II)σε υδατικό περιβάλλον διερευνήθηκε με θολομετρία, ιξωδομετρία, φασματοφωτομετρία UV-Vis, δυναμική σκέδαση φωτός, ιχνηθέτηση με φθορίζοντες ιχνηθέτες και προσδιορισμό του ζ-δυναμικού. Σε επόμενο στάδιο διερευνήθηκε η δυνατότητα σχηματισμού τριμερών συμπλόκων ΡAΝa/Cu(II)/επιφανειοδραστικής ένωσης σε υδατικό περιβάλλον. Από τη φυσικοχημική μελέτη των συστημάτων σε συνάρτηση του pΗ, ελήφθησαν σημαντικές πληροφορίες σχετικά με τον ανταγωνισμό των δύο ειδών (ιόντα Cu(II)ή ιόντα επιφανειοδραστικής ένωσης) να σχηματίσουν σύμπλοκα με το PANa. Ως τελικό στάδιο, παρασκευάστηκαν αδιάλυτα στο νερό υβριδικά υλικά πολυμερούς/Cu(II)ή πολυμερούς/Cu(II)/επιφανειοδραστικής ένωσης. Έπειτα από διερεύνηση της συμβατότητας/αναμιξιμότητάς τους με εμπορικές μήτρες που χρησιμοποιούνται συνήθως στη βιομηχανία χρωμάτων, ορισμένα από αυτά ενσωματώθηκαν σε πραγματικά χρώματα.The binding/release of Cu(II) ions or/and surfactants from comb-type copolymers was studied. The backbone was poly(sodium acrylate), PANa, whereas the side chains were poly(N, N-Dimethylacrylamide) and Poly9N-Isopropylacrylamide). The complexation of these copolymers with Cu(II) ions in water, was studied by turbidimetry, viscometry, UV-Vis fasmatophotometry, dynamic light scattering, fluorescense probing and ζ-potential. As a next step, the possible formation of ternary PANa/Cu(II)/surfactant complexes in water was studied. From the physiocochemical studies with pH, important information was taken as far as the competition of the two species (Cu(II) ions and surfactant) to form complexes with PANa is concerned. As a next step, water-insoluble hybrid polymer/Cu(II) or polymer/Cu(II)/surfactant materials were produced. After studies upon the compatibility/mischibility of the hybrid materials with matrices that are usually used in paints, some of the materials were incorporated to paints.
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Duarte, Claudia Berta. "Biocompatibilidade das principais ligas metálicas utilizadas em medicina dentária em Portugal." Master's thesis, 2017. http://hdl.handle.net/10284/6140.
Abstract:
As ligas metálicas utilizadas em medicina dentária podem influenciar não apenas a qualidade e durabilidade das próteses e implantes dentários como também a saúde dos tecidos orais e até sistémicos.
Antigamente os efeitos biológicos das ligas metálicas e materiais dentários eram ignorados em estudos e totalmente desconhecidos, porém com o passar do tempo observou-se a influência direta e indireta da biocompatibilidade destes metais e ligas metálicas no sucesso dos tratamentos dentários de reabilitação.
O objetivo deste estudo é apresentar conteúdos atualizados e conceitos já conhecidos e comprovados através de uma revisão da literatura existente sobre o biocompatibilidade das ligas metálicas mais utilizadas em medicina dentária em Portugal.
Para a presente revisão bibliográfica, foi realizada uma pesquisa bibliográfica com recurso a livros e artigos publicados em revistas, e que foram consultados nas Bibliotecas da Faculdade de Medicina Dentária da Universidade do Porto e da Universidade Fernando Pessoa. Procedeu-se à pesquisa por recurso aos motores de busca na internet, tais como, PubMed, Scielo, B-On e Medline, utilizando as seguintes palavras-chave, em conjunto ou individualmente: Ligas metálicas, prótese dentária, reabilitação dentária, reabilitação oral, biocompatibilidade, citotoxicidade, liberação, iões, titânio, cobalto, cromo¨. Foram selecionados artigos entre 1980 e 2017, com relevância para o presente trabalho de dissertação de Mestrado, escritos em Português e Inglês.Metal alloys used in dentistry can influence not only the quality and durability of dental prosthesis and dental implants as well as oral health and even systemic tissues. In the past years, the biological effects of metal alloys and dental materials have been ignored and unknown in scientific studies, but over the following years it could be observed the direct and indirect influences of the biocompatibility of those metals and metal alloys in dental rehabilitation treatments success. The aim of this study is organize and include an updated scientific content and known concepts and through a review of existing literature about the biocompatibility of metal alloys used in dentistry in Portugal. For this bibliographic review, a bibliographic research was performed with the use of books and articles published in journals, which were consulted in the libraries of the Dental Faculty of the University of Porto and the Fernando Pessoa University. The research was carried out by resource to internet search engines such as PubMed, Scielo, B-On and Medline, using the following keywords, jointly or individually: metal alloys, dental alloys, dental prosthesis, dental rehabilitation, oral rehabilitation, biocompatibility, release, ions, titanium, cobalt, chromium, nickel, dentistry. Articles were selected between 1980 and 2017, with relevance to the present work of the Master thesis, written in Portuguese and English.