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Gamma-IFN-inducible-lysosomal thiol reductase modulates acidic proteases and HLA class II antigen processing in melanoma  

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HLA class II-restricted antigen (Ag) processing and presentation are important for the activation of CD4+ T cells, which are the central orchestrating cells of immune responses. The majority of melanoma cells either expresses, or can be induced to express, HLA class II proteins. Thus, they are prime targets for immune mediated elimination by class II-restricted CD4+ T cells. We have previously shown that human melanoma cells lack an important enzyme, gamma interferon-inducible lysosomal thiol...

Goldstein, Oliver G.; Hajiaghamohseni, Laela M.; Amria, Shereen; Sundaram, Kumaran; Reddy, Sakamuri V.; Haque, Azizul

2008-01-01

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Disulfide Reduction in the Endocytic Pathway: Immunological Functions of Gamma-Interferon-Inducible Lysosomal Thiol Reductase  

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Gamma-interferon-inducible lysosomal thiol reductase (GILT) is constitutively expressed in most antigen presenting cells and is interferon ? inducible in other cell types via signal transducer and activator of transcription 1. Normally, N- and C-terminal propeptides are cleaved in the early endosome, and the mature protein resides in late endosomes and lysosomes. Correspondingly, GILT has maximal reductase activity at an acidic pH. Monocyte differentiation via Toll-like receptor 4 triggers s...

Hastings, Karen Taraszka; Cresswell, Peter

2011-01-01

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Effects of glutathione reductase inhibition on cellular thiol redox state and related systems  

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Although inhibition of glutathione reductase (GR) has been demonstrated to cause a decrease in reduced glutathione (GSH) and increase in glutathione disulfide (GSSG), a systematic study of the effects of GR inhibition on thiol redox state and related systems has not been noted. By employing a monkey kidney cell line as the cell model and 2-acetylamino-3-[4-(2-acetylamino-2-carboxy-ethylsulfanylthio-carbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (2-AAPA) as a GR inhibitor, an investi...

Zhao, Yong; Seefeldt, Teresa; Chen, Wei; Wang, Xiuqing; Matthees, Duane; Hu, Yueshan; Guan, Xiangming

2009-01-01

4

Cloning and sequencing of thiol-specific antioxidant from mammalian brain: alkyl hydroperoxide reductase and thiol-specific antioxidant define a large family of antioxidant enzymes.  

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A cDNA corresponding to a thiol-specific antioxidant enzyme (TSA) was isolated from a rat brain cDNA library with the use of antibodies to bovine TSA. The cDNA clone encoded an open reading frame capable of encoding a 198-residue polypeptide. The rat and yeast TSA proteins show significant sequence homology to the 21-kDa component (AhpC) of Salmonella typhimurium alkyl hydroperoxide reductase, and we have found that AhpC exhibits TSA activity. AhpC and TSA define a family of > 25 different pr...

Chae, H. Z.; Robison, K.; Poole, L. B.; Church, G.; Storz, G.; Rhee, S. G.

1994-01-01

5

Thioredoxin Reductase Is Essential for Thiol/Disulfide Redox Control and Oxidative Stress Survival of the Anaerobe Bacteroides fragilis? †  

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Results of this study showed that the anaerobic, opportunistic pathogen Bacteroides fragilis lacks the glutathione/glutaredoxin redox system and possesses an extensive number of putative thioredoxin (Trx) orthologs. Analysis of the genome sequence revealed six Trx orthologs and an absence of genes required for synthesis of glutathione and glutaredoxins. In addition, it was shown that the thioredoxin reductase (TrxB)/Trx system is the major or sole redox system for thiol/disulfide cellular hom...

Rocha, Edson R.; Tzianabos, Arthur O.; Smith, C. Jeffrey

2007-01-01

6

Glutathione Reductase from Lactobacillus sanfranciscensis DSM20451T: Contribution to Oxygen Tolerance and Thiol Exchange Reactions in Wheat Sourdoughs?  

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The effect of the glutathione reductase (GshR) activity of Lactobacillus sanfranciscensis DSM20451T on the thiol levels in fermented sourdoughs was determined, and the oxygen tolerance of the strain was also determined. The gshR gene coding for a putative GshR was sequenced and inactivated by single-crossover integration to yield strain L. sanfranciscensis DSM20451T?gshR. The gene disruption was verified by sequencing the truncated gshR and surrounding regions on the chromosome. The gshR act...

Ja?nsch, Andre?; Korakli, Maher; Vogel, Rudi F.; Ga?nzle, Michael G.

2007-01-01

7

Molecular cloning, expression and functional characterization of interferon-?-inducible lysosomal thiol reductase (GILT) gene from mandarin fish (Siniperca chuatsi).  

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Interferon-?-inducible lysosomal thiol reductase (GILT) plays a key role in the processing and presentation of MHC class II-restricted antigen (Ag) by catalyzing disulfide bond reduction, thus unfolding native protein Ag and facilitating subsequent cleavage by proteases. For this important function in the immune system, we cloned a GILT gene homologue from mandarin fish (designated mGILT), a kind of precious freshwater fish with high market value. Through reverse transcription PCR and rapid amplification of cDNA ends (RACE) strategies, we obtained the full-length cDNA of mGILT, which consists of 1008 bp with a 771 bp open reading frame, encoding a protein of 256 amino acids, with a putative molecular weight of 28.47 kDa. The deduced protein possesses the typical structural features of known GILT proteins, including an active-site motif, a GILT signature sequence, and 6 conserved cysteines. The result of real-time quantitative PCR showed that mGILT mRNA was expressed in a tissue-specific manner. In addition, the expression of mGILT mRNA was obviously up-regulated in splenocytes and kidney after induction with lipopolysaccharide (LPS). Recombinant mGILT fused with His6 tag was efficiently expressed in Escherichia coli BL21 (DE3) and purified using Ni-nitrilotriacetic acid resin. Further study revealed that mGILT exhibit thiol reductase activity on IgG substrate. These results suggest mGILT is highly likely to play a role in the immune responses in mandarin fish. PMID:24698993

Song, Jinyun; Liu, Hongzhen; Ma, Lei; Ma, Li; Gao, Cuixiang; Zhang, Shuangquan

2014-06-01

8

Identification of gamma-interferon-inducible lysosomal thiol reductase (GILT) homologues in the fruit fly Drosophila melanogaster.  

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Gamma-interferon-inducible lysosomal thiol reductase (GILT) has been demonstrated to be involved in the immune response to bacterial challenge in various organisms. However, little is known about GILT function in innate immunity. Drosophila has been commonly used as a model for the study of the innate immune response of invertebrates. Here, we identify the CG9796, CG10157, and CG13822 genes of fruit fly Drosophila melanogaster as GILT homologues. All deduced Drosophila GILT coding sequences contained the major characteristic features of the GILT protein family: the GILT signature CQHGX2ECX2NX4C sequence and the active site CXXC or CXXS motif. The mRNA transcript levels of the Drosophila GILT genes were up-regulated after Gram-negative bacteria Escherichia coli DH5? infection. Moreover, a bacterial load assay showed that over-expression of Drosophila GILT in fat body or hemocytes led to a low bacterial colony number whereas knock-down of Drosophila GILT in fat body or hemocytes led to a high bacterial colony number when compared to a wild-type control. These results indicate that the Drosophila GILTs are very likely to play a role in the innate immune response upon bacterial challenge of Drosophila host defense. This study may provide the basis for further study on GILT function in innate immunity. PMID:24491521

Kongton, Kittima; McCall, Kimberly; Phongdara, Amornrat

2014-06-01

9

Characterization of clutathione amide reductase from Chromatium gracile. Identification of a novel thiol peroxidase (Prx/Grx) fueled by glutathione amide redox cycling.  

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Among the Chromatiaceae, the glutathione derivative gamma-l-glutamyl-l-cysteinylglycine amide, or glutathione amide, was reported to be present in facultative aerobic as well as in strictly anaerobic species. The gene (garB) encoding the central enzyme in glutathione amide cycling, glutathione amide reductase (GAR), has been isolated from Chromatium gracile, and its genomic organization has been examined. The garB gene is immediately preceded by an open reading frame encoding a novel 27.5-kDa chimeric enzyme composed of one N-terminal peroxiredoxin-like domain followed by a glutaredoxin-like C terminus. The 27.5-kDa enzyme was established in vitro to be a glutathione amide-dependent peroxidase, being the first example of a prokaryotic low molecular mass thiol-dependent peroxidase. Amino acid sequence alignment of GAR with the functionally homologous glutathione and trypanothione reductases emphasizes the conservation of the catalytically important redox-active disulfide and of regions involved in binding the FAD prosthetic group and the substrates glutathione amide disulfide and NADH. By establishing Michaelis constants of 97 and 13.2 microm for glutathione amide disulfide and NADH, respectively (in contrast to K(m) values of 6.9 mm for glutathione disulfide and 1.98 mm for NADPH), the exclusive substrate specificities of GAR have been documented. Specificity for the amidated disulfide cofactor partly can be explained by the substitution of Arg-37, shown by x-ray crystallographic data of the human glutathione reductase to hydrogen-bond one of the glutathione glycyl carboxylates, by the negatively charged Glu-21. On the other hand, the preference for the unusual electron donor, to some extent, has to rely on the substitution of the basic residues Arg-218, His-219, and Arg-224, which have been shown to interact in the human enzyme with the NADPH 2'-phosphate group, by Leu-197, Glu-198, and Phe-203. We suggest GAR to be the newest member of the class I flavoprotein disulfide reductase family of oxidoreductases. PMID:11399772

Vergauwen, B; Pauwels, F; Jacquemotte, F; Meyer, T E; Cusanovich, M A; Bartsch, R G; Van Beeumen, J J

2001-06-15

10

Crystal structure of the YffB protein from Pseudomonas aeruginosa suggests a glutathione-dependent thiol reductase function  

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Abstract Background The yffB (PA3664) gene of Pseudomonas aeruginosa encodes an uncharacterized protein of 13 kDa molecular weight with a marginal sequence similarity to arsenate reductase from Escherichia coli. The crystal structure determination of YffB was undertaken as part of a structural genomics effort in order to assist with the functional assignment of the protein. Results The structure was determined at 1.0 Å resolution by s...

Teplyakov Alexey; Pullalarevu Sadhana; Obmolova Galina; Doseeva Victoria; Galkin Andrey; Herzberg Osnat; Dauter Miroslawa; Dauter Zbigniew; Gilliland Gary L

2004-01-01

11

Comparative study of the physiological roles of three peroxidases (NADH peroxidase, Alkyl hydroperoxide reductase and Thiol peroxidase) in oxidative stress response, survival inside macrophages and virulence of Enterococcus faecalis.  

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The opportunistic pathogen Enterococcus faecalis is well equipped with peroxidatic activities. It harbours three loci encoding a NADH peroxidase, an alkyl hydroperoxide reductase and a protein (EF2932) belonging to the AhpC/TSA family. We present results demonstrating that ef2932 does encode a thiol peroxidase (Tpx) and show that it is part of the regulon of the hydrogen peroxide regulator HypR. Characterization of unmarked deletion mutants showed that all three peroxidases are important for the defence against externally provided H(2)O(2). Exposure to internal generated H(2)O(2) by aerobic growth on glycerol, lactose, galactose or ribose showed that Npr was absolutely required for aerobic growth on glycerol and optimal growth on the other substrates. Growth on glycerol was also dependent on Ahp. Addition of catalase restored growth of the mutants, and therefore, extracellular H(2)O(2) concentrations have been determined. This showed that the time point of growth arrest of the Deltanpr mutant correlated with the highest H(2)O(2) concentration measured. Analysis of the survival of the different strains inside peritoneal macrophages revealed that Tpx was the most important antioxidant activity for protecting the cells against the hostile phagocyte environment. Finally, the Deltatpx and the triple mutant showed attenuated virulence in a mouse peritonitis model. PMID:17971082

La Carbona, Stephanie; Sauvageot, Nicolas; Giard, Jean-Christophe; Benachour, Abdellah; Posteraro, Brunella; Auffray, Yanick; Sanguinetti, Maurizio; Hartke, Axel

2007-12-01

12

Thiol biochemistry of prokaryotes  

Science.gov (United States)

The present studies have shown that GSH metabolism arose in the purple bacteria and cyanobacteria where it functions to protect against oxygen toxicity. Evidence was obtained indicating that GSH metabolism was incorporated into eucaryotes via the endosymbiosis giving rise to mitochrondria and chloroplasts. Aerobic bacteria lacking GSH utilize other thiols for apparently similar functions, the thiol being coenzyme A in Gram positive bacteria and chi-glutamylcysteine in the halobacteria. The thiol biochemistry of prokaryotes is thus seen to be much more highly diversified than that of eucaryotes and much remains to be learned about this subject.

Fahey, Robert C.

1986-01-01

13

Cell surface thiol isomerases may explain the platelet-selective action of S-nitrosoglutathione  

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S-nitrosoglutathione (GSNO) at low concentration inhibits platelet aggregation without causing vasodilation, suggesting platelet-selective nitric oxide delivery. The mechanism of this selectivity is unknown, but may involve cell surface thiol isomerases, in particular protein disulphide isomerase (csPDI) (EC 5.3.4.1). We have now compared csPDI expression and activity on platelets, endothelial cells and vascular smooth muscle cells, and the dependence on thiol reductase activity of these cell...

Xiao, Fang; Gordge, Michael P.

2011-01-01

14

Thiol Reactive Probes and Chemosensors  

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Thiols are important molecules in the environment and in biological processes. Cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H2S) play critical roles in a variety of physiological and pathological processes. The selective detection of thiols using reaction-based probes and sensors is very important in basic research and in disease diagnosis. This review focuses on the design of fluorescent and colorimetric probes and sensors for thiol detection. Thiol detection m...

Peng, Hanjing; Chen, Weixuan; Cheng, Yunfeng; Hakuna, Lovemore; Strongin, Robert; Wang, Binghe

2012-01-01

15

Thiols and radiosensitivity  

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The role played by non-protein (NPSH) and protein sulfhydryls (PSH) in hypoxic and aerated cell radiosensitivity was investigated using human skin fibroblasts derived from patients affected with 5-oxoprolinuria. These cells have lowered levels of the enzyme GSH-synthetase which results in a decreased concentration of glutathione. Six cell lines were studied; GM3877 and GM3878, SR and SUR from a single family and OB and AB from a French family. Only GM3877, with GSH levels of 0.6 nmoles/mg protein and NPSH levels of 4 nmoles/mg protein, was found to exhibit a reduced OER of 1.8. Experiments are now in progress to investigate the effect of depleting thiol levels with the ?-glutamyl cysteine synthetase inhibitor DL Buthionine-SR-sulfoximine to determine if the OER is further reduced, especially in the cell line which already has a lowered OER. The results are discussed with a view toward developing a model which takes into account the role of thiols and DNA repair processes in the resistance of hypoxic cells to ionizing radiation

1984-03-01

16

Thiol Reactive Probes and Chemosensors  

Directory of Open Access Journals (Sweden)

Full Text Available Thiols are important molecules in the environment and in biological processes. Cysteine (Cys, homocysteine (Hcy, glutathione (GSH and hydrogen sulfide (H2S play critical roles in a variety of physiological and pathological processes. The selective detection of thiols using reaction-based probes and sensors is very important in basic research and in disease diagnosis. This review focuses on the design of fluorescent and colorimetric probes and sensors for thiol detection. Thiol detection methods include probes and labeling agents based on nucleophilic addition and substitution, Michael addition, disulfide bond or Se-N bond cleavage, metal-sulfur interactions and more. Probes for H2S are based on nucleophilic cyclization, reduction and metal sulfide formation. Thiol probe and chemosensor design strategies and mechanism of action are discussed in this review.

Binghe Wang

2012-11-01

17

Evaluation of a dithiocarbamate derivative as a model of thiol oxidative stress in H9c2 rat cardiomyocytes.  

Science.gov (United States)

Thiol redox state (TRS) refers to the balance between reduced thiols and their corresponding disulfides and is mainly reflected by the ratio of reduced and oxidized glutathione (GSH/GSSG). A decrease in GSH/GSSG, which reflects a state of thiol oxidative stress, as well as thiol modifications such as S-glutathionylation, has been shown to have important implications in a variety of cardiovascular diseases. Therefore, research models for inducing thiol oxidative stress are important tools for studying the pathophysiology of these disease states as well as examining the impact of pharmacological interventions on thiol pathways. The purpose of this study was to evaluate the use of a dithiocarbamate derivative, 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylthiocarbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (2-AAPA), as a pharmacological model of thiol oxidative stress by examining the extent of thiol modifications induced in H9c2 rat cardiomyocytes and its impact on cellular functions. The extent of thiol oxidative stress produced by 2-AAPA was also compared to other models of oxidative stress including hydrogen peroxide (H2O2), diamide, buthionine sulfoximine, and N,N?-bis(2-chloroethyl)-N-nitroso-urea. Results indicated that 2-AAPA effectively inhibited glutathione reductase and thioredoxin reductase activities and decreased the GSH/GSSG ratio by causing a significant accumulation of GSSG. 2-AAPA also increased the formation of protein disulfides as well as S-glutathionylation. The alteration in TRS led to a loss of mitochondrial membrane potential, release of cytochrome c, and increase in reactive oxygen species production. Compared to other models, 2-AAPA is more potent at creating a state of thiol oxidative stress with lower cytotoxicity, higher specificity, and more pharmacological relevance, and could be utilized as a research tool to study TRS-related normal and abnormal biochemical processes in cardiovascular diseases. PMID:24607690

Xie, Jiashu; Potter, Ashley; Xie, Wei; Lynch, Christophina; Seefeldt, Teresa

2014-05-01

18

A hydrogen peroxide electrode assay to measure thiol peroxidase activity for organoselenium and organotellurium drugs.  

Science.gov (United States)

Molecular mimics of the enzyme glutathione peroxidase (GPx) are increasingly being evaluated as redox active drugs. Their molecular mechanism of action parallels that of the native enzyme; however, a major distinction is that GPx mimics can use alternative thiol substrates to glutathione. This generic thiol peroxidase activity implies that it is necessary to assess a GPx mimic's recognition of a range of cellular thiols in order to determine its potential therapeutic effects. We report an electrochemical assay that, by measuring the rate of decrease of the peroxide substrate, allows the activity of GPx mimics to be directly compared against an array of thiols. The derived pseudo zero-order rate constants, k(obs), for representative GPx mimics range between 0 and 6.6 min(-1) and can vary by more than an order of magnitude depending on the thiol electron donor. An additional advantage of the assay is that it enables synergistic interactions between GPx mimics and cellular proteins to be evaluated. Here we report that glutathione disulfide reductase, which is commonly used to evaluate GPx mimic activity, recognizes the GPx mimic ebselen as a substrate, increasing its apparent k(obs). Therefore, reports relying on glutathione disulfide reductase to evaluate GPx mimic activity may exaggerate drug antioxidant action. PMID:22813709

Giles, Niroshini M; Kumari, Sweta; Stamm, Rosemary A; Patel, Siddharth; Giles, Gregory I

2012-10-15

19

Thiol isomerases in thrombus formation.  

Science.gov (United States)

Protein disulfide isomerase (PDI), ERp5, and ERp57, among perhaps other thiol isomerases, are important for the initiation of thrombus formation. Using the laser injury thrombosis model in mice to induce in vivo arterial thrombus formation, it was shown that thrombus formation is associated with PDI secretion by platelets, that inhibition of PDI blocked platelet thrombus formation and fibrin generation, and that endothelial cell activation leads to PDI secretion. Similar results using this and other thrombosis models in mice have demonstrated the importance of ERp5 and ERp57 in the initiation of thrombus formation. The integrins, ?IIb?3 and ?V?3, play a key role in this process and interact directly with PDI, ERp5, and ERp57. The mechanism by which thiol isomerases participate in thrombus generation is being evaluated using trapping mutant forms to identify substrates of thiol isomerases that participate in the network pathways linking thiol isomerases, platelet receptor activation, and fibrin generation. PDI as an antithrombotic target is being explored using isoquercetin and quercetin 3-rutinoside, inhibitors of PDI identified by high throughput screening. Regulation of thiol isomerase expression, analysis of the storage, and secretion of thiol isomerases and determination of the electron transfer pathway are key issues to understanding this newly discovered mechanism of regulation of the initiation of thrombus formation. PMID:24677236

Furie, Bruce; Flaumenhaft, Robert

2014-03-28

20

Thiol-based redox switches.  

Science.gov (United States)

Regulation of protein function through thiol-based redox switches plays an important role in the response and adaptation to local and global changes in the cellular levels of reactive oxygen species (ROS). Redox regulation is used by first responder proteins, such as ROS-specific transcriptional regulators, chaperones or metabolic enzymes to protect cells against mounting levels of oxidants, repair the damage and restore redox homeostasis. Redox regulation of phosphatases and kinases is used to control the activity of select eukaryotic signaling pathways, making reactive oxygen species important second messengers that regulate growth, development and differentiation. In this review we will compare different types of reversible protein thiol modifications, elaborate on their structural and functional consequences and discuss their role in oxidative stress response and ROS adaptation. This article is part of a Special Issue entitled: Thiol-Based Redox Processes. PMID:24657586

Groitl, Bastian; Jakob, Ursula

2014-08-01

 
 
 
 
21

Structural and Mechanistic Insights into Unusual Thiol Disulfide Oxidoreductase  

Science.gov (United States)

Cytoplasmic desulfothioredoxin (Dtrx) from the anaerobe Desulfovibrio vulgaris Hildenborough has been identified as a new member of the thiol disulfide oxidoreductase family. The active site of Dtrx contains a particular consensus sequence, CPHC, never seen in the cytoplasmic thioredoxins and generally found in periplasmic oxidases. Unlike canonical thioredoxins (Trx), Dtrx does not present any disulfide reductase activity, but it presents instead an unusual disulfide isomerase activity. We have used NMR spectroscopy to gain insights into the structure and the catalytic mechanism of this unusual Dtrx. The redox potential of Dtrx (?181 mV) is significantly less reducing than that of canonical Trx. A pH dependence study allowed the determination of the pKa of all protonable residues, including the cysteine and histidine residues. Thus, the pKa values for the thiol group of Cys31 and Cys34 are 4.8 and 11.3, respectively. The His33 pKa value, experimentally determined for the first time, differs notably as a function of the redox states, 7.2 for the reduced state and 4.6 for the oxidized state. These data suggest an important role for His33 in the molecular mechanism of Dtrx catalysis that is confirmed by the properties of mutant DtrxH33G protein. The NMR structure of Dtrx shows a different charge repartition compared with canonical Trx. The results presented are likely indicative of the involvement of this protein in the catalysis of substrates specific of the anaerobe cytoplasm of DvH. The study of Dtrx is an important step toward revealing the molecular details of the thiol-disulfide oxidoreductase catalytic mechanism.

Garcin, Edwige B.; Bornet, Olivier; Elantak, Latifa; Vita, Nicolas; Pieulle, Laetitia; Guerlesquin, Francoise; Sebban-Kreuzer, Corinne

2012-01-01

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Asymmetric synthesis of tertiary thiols and thioethers  

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Enantiomerically pure tertiary thiols provide a major synthetic challenge, and despite the importance of chiral sulfur-containing compounds in biological and medicinal chemistry, surprisingly few effective methods are suitable for the asymmetric synthesis of tertiary thiols. This review details the most practical of the methods available.

Jonathan Clayden; Paul MacLellan

2011-01-01

23

Protein Thiol Modifications Visualized In Vivo  

Directory of Open Access Journals (Sweden)

Full Text Available Thiol-disulfide interconversions play a crucial role in the chemistry of biological systems. They participate in the major systems that control the cellular redox potential and prevent oxidative damage. In addition, thiol-disulfide exchange reactions serve as molecular switches in a growing number of redox-regulated proteins. We developed a differential thiol-trapping technique combined with two-dimensional gel analysis, which in combination with genetic studies, allowed us to obtain a snapshot of the in vivo thiol status of cellular proteins. We determined the redox potential of protein thiols in vivo, identified and dissected the in vivo substrate proteins of the major cellular thiol-disulfide oxidoreductases, and discovered proteins that undergo thiol modifications during oxidative stress. Under normal growth conditions most cytosolic proteins had reduced cysteines, confirming existing dogmas. Among the few partly oxidized cytosolic proteins that we detected were proteins that are known to form disulfide bond intermediates transiently during their catalytic cycle (e.g., dihydrolipoyl transacetylase and lipoamide dehydrogenase. Most proteins with highly oxidized thiols were periplasmic proteins and were found to be in vivo substrates of the disulfide-bond-forming protein DsbA. We discovered a substantial number of redox-sensitive cytoplasmic proteins, whose thiol groups were significantly oxidized in strains lacking thioredoxin A. These included detoxifying enzymes as well as many metabolic enzymes with active-site cysteines that were not known to be substrates for thioredoxin. H2O2-induced oxidative stress resulted in the specific oxidation of thiols of proteins involved in detoxification of H2O2 and of enzymes of cofactor and amino acid biosynthesis pathways such as thiolperoxidase, GTP-cyclohydrolase I, and the cobalamin-independent methionine synthase MetE. Remarkably, a number of these proteins were previously or are now shown to be redox regulated.

Leichert Lars I

2004-01-01

24

Profiling patterns of glutathione reductase inhibition by the natural product illudin S and its acylfulvene analogues  

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Acylfulvenes (AFs) are a class of antitumor agents with favorable cytotoxic selectivity profiles compared to their natural product precursor, illudin S. Like many alkylating agents, illudin S and AFs readily react with thiol-containing small molecules such as cysteine, glutathione and cysteine-containing peptides; reduced cellular glutathione levels can affect illudin S toxicity. Glutathione reductase (GR) is a critical cellular anti-oxidant enzyme that regulates the intracellular ratio of re...

Liu, Xiaodan; Sturla, Shana J.

2009-01-01

25

Thiol-ene and thiol-yne chemistry in microfluidics: a straightforward method towards macroporous and nonporous functional polymer beads  

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Thiol-ene and thiol-yne reactions are explored as efficient pathways towards rapid production of diverse monodisperse macroporous and nonporous functional beads. In a straightforward method, polymer beads containing amine, hydroxyl and carboxyl groups have been prepared by reacting a tetrafunctional thiol with a range of mono and/or multifunctional -enes/-ynes containing the desired functional groups. The thiol-ene and thiol-yne reactions have been performed in a simple home-made microfluidic...

Ramaswamy, Arun Prasath; Go?kmen, Muhammed; Espeel, Pieter; Du Prez, Filip

2010-01-01

26

Purine nucleoside phosphorylase as a cytosolic arsenate reductase.  

Science.gov (United States)

The findings of the accompanying paper (Németi and Gregus, Toxicol: Sci. 70, 4-12) indicate that the arsenate (AsV) reductase activity of rat liver cytosol is due to an SH enzyme that uses phosphate (or its analogue, arsenate, AsV) and a purine nucleoside (guanosine or inosine) as substrates. Purine nucleoside phosphorylase (PNP) is such an enzyme. It catalyzes the phosphorolytic cleavage of 6-oxopurine nucleosides according to the following scheme: guanosine (or inosine) + phosphate guanine (or hypoxanthine) + ribose-1-phosphate. Therefore, we have tested the hypothesis that PNP is responsible for the thiol- and purine nucleoside-dependent reduction of AsV to AsIII by rat liver cytosol. AsIII formed from AsV was quantified by HPLC-hydride generation-atomic fluorescence spectrometry analysis of the deproteinized incubates. The following findings support the conclusion that PNP reduces AsV to AsIII, using AsV instead of phosphate in the reaction above: (1) Specific PNP inhibitors (CI-1000, BCX-1777) at a concentration of 1 microM completely inhibited cytosolic AsV reductase activity. (2) During anion-exchange chromatography of cytosolic proteins, PNP activity perfectly coeluted with the AsV reductase activity, suggesting that both activities belong to the same protein. (3) PNP purified from calf spleen catalyzed reduction of AsV to AsIII in the presence of dithiothreitol (DTT) and a 6-oxopurine nucleoside (guanosine or inosine). (4) AsV reductase activity of purified PNP, like the cytosolic AsV reductase activity, was inhibited by phosphate (a substrate of PNP alternative to AsV), guanine and hypoxanthine (products of PNP favoring the reverse reaction), mercurial thiol reagents (nonspecific inhibitors of PNP), as well as CI-1000 and BCX-1777 (specific PNP inhibitors). Thus, PNP appears to be responsible for the AsV reductase activity of rat liver cytosol in the presence of DTT. Further research should clarify the mechanism and the in vivo significance of PNP-catalyzed reduction of AsV to AsIII. PMID:12388830

Gregus, Zoltán; Németi, Balázs

2002-11-01

27

Glucagon activation of the thiol:protein disulfide oxidoreductase in isolated, rat, hepatic microsomes  

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Thiol:protein disulfide oxidoreductase catalyzes the GSH reduction of protein disulfides to sulfhydryl groups. The authors determined this activity in washed rat hepatic microsomes (1) by a coupled reaction in which GSSG is reduced by GSH reductase and NADPH is oxidized and (2) by the cleavage of (/sup 125/I)-insulin (insulinase). Physiological concentrations of glucagon (GLU)(1 nM) with GSH (1 mM) increased both activities (NADPH oxidae - 1.1 nmol/min-mg prot (control)(C) to 4.3 (GLU); insulinase - 36 (C) to 83 (GLU)). For both assays stimulation was only seen with low protein concentrations (< 100 ..mu..g/ml), probably due to nonspecific GLU binding rather than proteolysis of the GLU since both reactions were linear for at least 30 min. The stimulation of NADPH oxidase had a P50 for GLU of 0.78 nM. GLU stimulation of insulinase was only observed in the presence of a GSH reducing system. Basal insulinase activity was unaffected by GSH reductase. These two observation suggest that the stimulation may be inhibited by the presence of GSSG. This effect was not due to depletion of GSH since the same effect was observed with higher GSH (5 mM). Although the effect on NADPH oxidase could represent activation of a GSH peroxidase, the insulinase data support the hypothesis that GLU may act by stimulating the thiol:protein disulfide oxidoreductase catalyzed reduction of protein disulfides.

McConkey, D.J.; Crankshaw, D.L.; Holtzman, J.L.

1986-05-01

28

Glucagon activation of the thiol:protein disulfide oxidoreductase in isolated, rat, hepatic microsomes  

International Nuclear Information System (INIS)

Thiol:protein disulfide oxidoreductase catalyzes the GSH reduction of protein disulfides to sulfhydryl groups. The authors determined this activity in washed rat hepatic microsomes (1) by a coupled reaction in which GSSG is reduced by GSH reductase and NADPH is oxidized and (2) by the cleavage of ["1"2"5I]-insulin (insulinase). Physiological concentrations of glucagon (GLU)(1 nM) with GSH (1 mM) increased both activities (NADPH oxidae - 1.1 nmol/min-mg prot (control)(C) to 4.3 (GLU); insulinase - 36 (C) to 83 (GLU)). For both assays stimulation was only seen with low protein concentrations (< 100 ?g/ml), probably due to nonspecific GLU binding rather than proteolysis of the GLU since both reactions were linear for at least 30 min. The stimulation of NADPH oxidase had a P50 for GLU of 0.78 nM. GLU stimulation of insulinase was only observed in the presence of a GSH reducing system. Basal insulinase activity was unaffected by GSH reductase. These two observation suggest that the stimulation may be inhibited by the presence of GSSG. This effect was not due to depletion of GSH since the same effect was observed with higher GSH (5 mM). Although the effect on NADPH oxidase could represent activation of a GSH peroxidase, the insulinase data support the hypothesis that GLU may act by stimulating the thiol:protein disulfide oxidoreductase catalyzed reduction of protein disulfides

1986-05-01

29

Coenzyme A disulfide reductase, the primary low molecular weight disulfide reductase from Staphylococcus aureus. Purification and characterization of the native enzyme.  

Science.gov (United States)

The human pathogen Staphylococcus aureus does not utilize the glutathione thiol/disulfide redox system employed by eukaryotes and many bacteria. Instead, this organism produces CoA as its major low molecular weight thiol. We report the identification and purification of the disulfide reductase component of this thiol/disulfide redox system. Coenzyme A disulfide reductase (CoADR) catalyzes the specific reduction of CoA disulfide by NADPH. CoADR has a pH optimum of 7.5-8.0 and is a dimer of identical subunits of Mr 49,000 each. The visible absorbance spectrum is indicative of a flavoprotein with a lambdamax = 452 nm. The liberated flavin from thermally denatured enzyme was identified as flavin adenine dinucleotide. Steady-state kinetic analysis revealed that CoADR catalyzes the reduction of CoA disulfide by NADPH at pH 7.8 with a Km for NADPH of 2 muM and for CoA disulfide of 11 muM. In addition to CoA disulfide CoADR reduces 4,4'-diphosphopantethine but has no measurable ability to reduce oxidized glutathione, cystine, pantethine, or H2O2. CoADR demonstrates a sequential kinetic mechanism and employs a single active site cysteine residue that forms a stable mixed disulfide with CoA during catalysis. These data suggest that S. aureus employs a thiol/disulfide redox system based on CoA/CoA-disulfide and CoADR, an unorthodox new member of the pyridine nucleotide-disulfide reductase superfamily. PMID:9488707

delCardayre, S B; Stock, K P; Newton, G L; Fahey, R C; Davies, J E

1998-03-01

30

Genomics and X-ray microanalysis indicate that Ca2+ and thiols mediate the aggregation and adhesion of Xylella fastidiosa  

Directory of Open Access Journals (Sweden)

Full Text Available The availability of the genome sequence of the bacterial plant pathogen Xylella fastidiosa, the causal agent of citrus variegated chlorosis, is accelerating important investigations concerning its pathogenicity. Plant vessel occlusion is critical for symptom development. The objective of the present study was to search for information that would help to explain the adhesion of X. fastidiosa cells to the xylem. Scanning electron microscopy revealed that adhesion may occur without the fastidium gum, an exopolysaccharide produced by X. fastidiosa, and X-ray microanalysis demonstrated the presence of elemental sulfur both in cells grown in vitro and in cells found inside plant vessels, indicating that the sulfur signal is generated by the pathogen surface. Calcium and magnesium peaks were detected in association with sulfur in occluded vessels. We propose an explanation for the adhesion and aggregation process. Thiol groups, maintained by the enzyme peptide methionine sulfoxide reductase, could be active on the surface of the bacteria and appear to promote cell-cell aggregation by forming disulfide bonds with thiol groups on the surface of adjacent cells. The enzyme methionine sulfoxide reductase has been shown to be an auxiliary component in the adhesiveness of some human pathogens. The negative charge conferred by the ionized thiol group could of itself constitute a mechanism of adhesion by allowing the formation of divalent cation bridges between the negatively charged bacteria and predominantly negatively charged xylem walls.

B. Leite

2002-06-01

31

Effect of Prolonged High-Fat Diet on Thiol-Disulfide Homeostasis in Rats  

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Full Text Available The aim of this study was to determine the effect of a prolonged high-fat (HF on thiol-disulfide homeostasis via the activity of the glutathione redox-system (GRS in rat blood and liver. Methods: The experiment was conducted on male Wistar rats. They were divided into groups and fed on the HF diet for 30, 90 and 180 days, respectively. The HF diet consisted of beef fat and cholesterol (19 % and 2 % of the total diet, respectively. The state of the GRS was assessed in the erythrocytes and liver tissue by the glutathione, glutathione reductase (GR and glutathione peroxidase (GP activity. The levels of the initial and final products of lipid peroxidation – lipid hydroperoxides (LOOHs, diene conjugates (DC and malondialdehydes (MDA in the blood and liver were investigated. Results: Within 30 days, the HF diet inhibits the glutathione enzyme activity in the blood (GR: P<0.01; GP: P<0.001 and liver (GR, P<0.01. Within 90 days the HF diet kick-starts the beginning of the GRS compensatory response and restores the thiol-disulfide homeostasis. At 180 days, the HF diet shows failure of the compensatory processes in the glutathione system caused by the redox-imbalance in the thiol-disulfide exchange, which reveals lowered levels of glutathione, GR and GP activity (P<0.001 for all in the blood and liver. Conclusion: Our results suggest that the thiol-disulfide status of the cells depends upon the nature of the nutrition, a long-term breach of which triggers a compensatory response and a failure of the compensatory processes in the GRS.

Tatyana P. Novgorodtseva

2013-09-01

32

Cytoplasmic glutathione redox status determines survival upon exposure to the thiol-oxidant 4,4'-dipyridyl disulfide.  

DEFF Research Database (Denmark)

Dipyridyl disulfide (DPS) is a highly reactive thiol oxidant that functions as electron acceptor in thiol-disulfide exchange reactions. DPS is very toxic to yeasts, impairing growth at low micromolar concentrations. The genes TRX2 (thioredoxin), SOD1 (superoxide dismutase), GSH1 (gamma-glutamyl-cysteine synthetase) and, particularly, GLR1 (glutathione reductase) are required for survival on DPS. DPS is uniquely thiol-specific, and we found that the cellular mechanisms for DPS detoxification differ substantially from that of the commonly used thiol oxidant diamide. In contrast to this oxidant, the full antioxidant pools of glutathione (GSH) and thioredoxin are required for resistance to DPS. We found that DPS-sensitive mutants display increases in the disulfide form of GSH (GSSG) during DPS exposure that roughly correlate with their more oxidizing GSH redox potential in the cytosol and their degree of DPS sensitivity. DPS seems to induce a specific disulfide stress, where an increase in the cytoplasmic/nuclearGSSG/GSH ratio results in putative DPS target(s) becoming sensitive to DPS. Udgivelsesdato: 2007-May

López-Mirabal, H Reynaldo; Thorsen, Michael

2007-01-01

33

Determination of water in thiols by Karl Fischer titration.  

Science.gov (United States)

Water in thiol-containing samples may be determined by titration with Karl Fischer reagent after conversion of the thiol into a thioether. Both acrylonitrile and N-ethylmaleimide have been found to be suitable reagents. PMID:18962259

Francis, H J; Persing, D D

1978-05-01

34

Aldehyde reductase activity in the antennae of Helicoverpa armigera.  

Science.gov (United States)

In the present study, we identified two aldehyde reductase activities in the antennae of Helicoverpa species, NADH and NADPH-dependent activity. We expressed one of these proteins of H.?armigera, aldo-keto reductase (AKR), which bears 56% identity to bovine aldose reductase, displays a NADPH-dependent activity and is mainly expressed in the antennae of adults. Whole-mount immunostaining showed that the enzyme is concentrated in the cells at the base of chemosensilla and in the nerves. The enzyme activity of H.?armigera?AKR is markedly different from those of mammalian enzymes. The best substrates are linear aliphatic aldehydes of 8-10 carbon atoms, but not hydroxyaldehydes. Both pheromone components of H.?armigera, which are unsaturated aldehydes of 16 carbons, are very poor substrates. Unlike mammalian AKRs, the H.?armigera enzyme is weakly affected by common inhibitors and exhibits a different behaviour from the action of thiols. A model of the enzyme suggests that the four cysteines are in their reduced form, as are the seven cysteines of mammalian enzymes. The occurrence of orthologous proteins in other insect species, that do not use aldehydes as pheromones, excludes the possibility of classifying this enzyme among the pheromone-degrading enzymes, as has been previously described in other insect species. PMID:24580848

Guo, H; Del Corso, A; Huang, L-Q; Mura, U; Pelosi, P; Wang, C-Z

2014-06-01

35

Oligonucleotide cyclization: The thiol-maleimide reaction revisited  

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A novel method to synthesize cyclic oligonucleotides (5- to 26-mer) using the thiol-maleimide reaction is described. The target molecules were obtained after subsequent removal of thiol and maleimide protecting groups from 5?-maleimido-3?-thiol-derivatized linear precursors. Retro-DielsAlder conditions deprotecting the maleimide simultaneously promoted cyclization cleanly and in high yield.

Sa?nchez, Albert; Pedroso Muller, Enrique; Grandas Sagarra, Anna

2013-01-01

36

Nitrate Reductase from Monoraphidium braunii  

Science.gov (United States)

Homogeneous nitrate reductase (EC 1.6.6.2) from Monoraphidium braunii was obtained by means of affinity chromatography in blue-Sepharose and gel filtration. After electrophoresis in polyacrylamide, gel slices containing pure nitrate reductase were disrupted and injected into previously unimmunized rabbits. The antiserum produced after several weeks was found to inhibit the different activities of nitrate reductase to a similar degree. Monospecificity of the antiserum was demonstrated by Ouchterlony double diffusion and crossed immunoelectrophoresis. The antibodies were purified by immunoabsorption to Sepharose-bound nitrate reductase. The intracellular location of nitrate reductase in green algae was examined by applying an immunocytochemical method to M. braunii cells. Ultrathin frozen sections were first treated with immunopurified anti-nitrate reductase monospecific antibodies, followed by incubation with colloidal gold-labeled goat antirabbit immunoglobulin G as a marker. The enzyme was specifically located in the pyrenoid region of the chloroplast. Images Fig. 1 Fig. 2 Fig. 4 Fig. 5

Lopez-Ruiz, Antonio; Roldan, Jose Manuel; Verbelen, Jean Pierre; Diez, Jesus

1985-01-01

37

Activated polyurethane modified with latent thiol groups.  

Science.gov (United States)

A novel type of modified polyurethane with pendant acetylthio groups (as a latent form of thiol groups) has been proposed for the use in surface modifications with various biomolecules. The polymer was prepared via a modified variant of low-temperature bromoalkylation of urethane hard segments followed by the reaction of pendant bromoalkyl groups with thiolacetic acid in mild conditions. The extent of modification with acetylthio groups can be made as high as 0.45 mmol/g. After deprotection of acetylthio groups and reaction of the resulting thiol groups with an excess of Ellman's reagent, 0.1 nmol/cm(2) of thiol-reactive 3-carboxy-4-nitrophenyldithio groups were detected on the surface of films cast from the modified polymer. A sensitive fluorescent probe--dansyl-L-cysteine was used for the quantification of thiol-reactive groups bound to the surface. The acetylthio-modified polyurethane is sufficiently stable to withstand conditions typical for the high-temperature processing (molding, extrusion) of polyurethanes. PMID:12361613

Alferiev, Ivan S; Fishbein, Ilia

2002-12-01

38

Microfluidic devices using thiol-ene polymers  

Science.gov (United States)

Here, a new polymeric microfluidic platform using off-stoichiometric thiol-ene (OSTE) polymers was developed. Thiolene polymers were chosen as they afford rapid UV curing, low volume shrinkage and optical transparency for use in microfluidic devices. Three different off-stoichiometric thiol-ene polymers with 30% excess allyl, 50% excess thiol and a 90% excess thiol (OSTE Allyl-30, OSTE-50 and OSTE-90, respectively) were fabricated. Attenuated reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and solid-state cross polarisation-magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) spectroscopy confirmed which functional groups (thiol or allyl) were present in excess in the OSTE polymers. The polymers were shown to have a more hydrophilic surface (water contact angle of 65°+/- 3) compared to polydimethylsiloxane (water contact angle of 105° +/- 5). Testing of the mechanical properties showed the glass transition temperatures to be 15.09 °C, 43.15 °C and, 57.48 °C for OSTE-90, OSTE Allyl-30 and, OSTE-50, respectively. The storage modulus was shown to be less than 10 MPa for the OSTE-90 polymer and approximately 1750 MPa for the OSTE Allyl-30 and OSTE-50 polymers. The polymers were then utilised to fabricate microfluidic devices via soft lithography practices and devices sealed using a one-step UV lamination "click" reaction technique. Finally, gold nanoparticles were used to form gold films on the OSTE-90 and OSTE-50 polymers as potential electrodes. Atomic force microscopy and sheet resistances were used to characterise the films.

Bou, Simon J. M. C.; Ellis, Amanda V.

2013-12-01

39

Experimental and theoretical studies of selective thiol-ene and thiol-yne click reactions involving N-substituted maleimides.  

Science.gov (United States)

A combination of experimental and computational methods has been used to understand the reactivity and selectivity of orthogonal thiol-ene and thiol-yne ?click? reactions involving N-allyl maleimide (1) and N-propargyl maleimide (2). Representative thiols methyl-3-mercaptopropionate and ?-mercaptoethanol are shown to add exclusively and quantitatively to the electron poor maleimide alkene of 1 and 2 under base (Et3N) initiated thiol-Michael conditions. Subsequent radical-mediated thiol-ene or thiol-yne reactions can be carried out to further functionalize the remaining allyl or propargyl moieties in near quantitative yields (>95%). Selectivity, however, can only be achieved when base-initiated thiol-Michael reactions are carried out first, as radical-mediated reactions between equimolar amounts of thiol and N-substituted maleimides give complex mixtures of products. CBS-QB3 calculations have been used to investigate the energetics and kinetics of reactions between a representative thiol (methyl mercaptan) with N-allyl and N-propargyl maleimide under both base-initiated and radical-mediated conditions. Calculations help elucidate the factors that underlie the selective base-initiated and nonselective radical-mediated thiol-ene/yne reactions. The results provide additional insights into how to design selective radical-mediated thiol-ene/yne reactions. PMID:23924266

Stolz, Robert M; Northrop, Brian H

2013-08-16

40

Thiol methyltransferase activity in inflammatory bowel disease  

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BACKGROUND—Luminal anionic sulphide may contribute to epithelial damage in ulcerative colitis. Thiol methyltransferase (TMT) governs sulphide detoxification by the colonic mucosa and circulating erythrocytes.?AIMS—To measure levels of TMT activity in erythrocytes of surgically treated cases of colitis or in rectal biopsies of defined groups of colitis.?PATIENTS—Venepuncture blood was obtained from 37 blood donors and 27 subjects who had previously undergone a proctocolecto...

Roediger, W.; Babidge, W.

2000-01-01

 
 
 
 
41

Thiol-disulfide oxidoreductases in Bacillus subtilis  

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An important function in protein folding is the formation of disulfide bonds. In different compartments of bacteria specific oxido reductases are responsible for this function. Thanks to the identification of all genes from various model organisms the understanding of the function of the various members of this family has increased dramatically. Zie: Summary

Dorenbos, Ronald

2004-01-01

42

Nitrate and periplasmic nitrate reductases.  

Science.gov (United States)

The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types--periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed. PMID:24141308

Sparacino-Watkins, Courtney; Stolz, John F; Basu, Partha

2014-01-21

43

Different-metal and thiol-thiol complexes of copper (indium) with 8-mercaptoquinoline (unithiol)  

International Nuclear Information System (INIS)

Different physicochemical methods were used to study the formation of two-metal complexes by the interaction of a binary Cu2+-In2+ (CH3COO-) mixture with 8-mercaptoquinoline and by thiol-thiol interaction in an RSH-H2Un--CH3COO--Cu2+ system. The reactions were proposed to be used in the analysis of Cu-In(Zn, Cd) binary mixtures in different technological processes as well as for for the differential determination of 8-mercaptoquinoline and unithiol by amperometric titration with a copper(2) solution

1992-04-01

44

Designed Chemical Intervention with Thiols for Prophylactic Contraception  

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Unlike somatic cells, sperm have several-fold more available-thiols that are susceptible to redox-active agents. The present study explains the mechanism behind the instant sperm-immobilizing and trichomonacidal activities of pyrrolidinium pyrrolidine-1-carbodithioate (PPC), a novel thiol agent rationally created for prophylactic contraception by minor chemical modifications of some known thiol drugs. PPC, and its three derivatives (with potential active-site blocked by alkylation), were synt...

2013-01-01

45

Fabrication and bonding of thiol-ene-based microfluidic devices  

DEFF Research Database (Denmark)

In this work, the bonding strength of microchips fabricated by thiol-ene free-radical polymerization was characterized in detail by varying the monomeric thiol/allyl composition from the stoichiometric ratio (1:1) up to 100% excess of thiol (2:1) or allyl (1:2) functional groups. Four different thiol-ene to thiol-ene bonding combinations were tested by bonding: (i) two stoichiometric layers, (ii) two layers bearing complementary excess of thiols and allyls, (iii) two layers both bearing excess of thiols, or (iv) two layers both bearing excess of allyls. The results showed that the stiffness of the cross-linked polymer plays the most crucial role regarding the bonding strength. The most rigid polymer layers were obtained by using the stoichiometric composition or an excess of allyls, and thus, the bonding combinations (i) and (iv) withstood the highest pressures (up to the cut-off value of 6 bar). On the other hand, excess of thiol monomers yielded more elastic polymer layers and thus decreased the pressure tolerance for bonding combinations (ii) and (iii). By using monomers with more thiol groups (e.g. tetrathiol versus trithiol), a higher cross-linking ratio, and thus, greater stiffness was obtained. Surface characterization by infrared spectroscopy confirmed that the changes in the monomeric thiol/allyl composition were also reflected in the surface chemistry. The flexibility of being able to bond different types of thiol-enes together allows for tuning of the surface chemistry to yield the desired properties for each application. Here, a capillary electrophoresis separation is performed to demonstrate the attractive properties of stoichiometric thiol-ene microchips. © 2013 IOP Publishing Ltd.

Sikanen, T.M.; Lafleur, Josiane P.

2013-01-01

46

A binuclear gold(i) complex with mixed bridging diphosphine and bis(n-heterocyclic carbene) ligands shows favorable thiol reactivity and inhibits tumor growth and angiogenesis in?vivo.  

Science.gov (United States)

In the design of anticancer gold(I) complexes with high in?vivo efficacy, tuning the thiol reactivity to achieve stability towards blood thiols yet maintaining the thiol reactivity to target cellular thioredoxin reductase (TrxR) is of pivotal importance. Herein we describe a dinuclear gold(I) complex (1-PF6 ) utilizing a bridging bis(N-heterocyclic carbene) ligand to attain thiol stability and a diphosphine ligand to keep appropriate thiol reactivity. Complex 1-PF6 displays a favorable stability that allows it to inhibit TrxR activity without being attacked by blood thiols. In?vivo studies reveal that 1-PF6 significantly inhibits tumor growth in mice bearing HeLa xenograft and mice bearing highly aggressive mouse B16-F10 melanoma. It inhibits angiogenesis in tumor models and inhibits sphere formation of cancer stem cells in?vitro. Toxicology studies indicate that 1-PF6 does not show systemic anaphylaxis on guinea pigs and localized irritation on rabbits. PMID:24729298

Zou, Taotao; Lum, Ching Tung; Lok, Chun-Nam; To, Wai-Pong; Low, Kam-Hung; Che, Chi-Ming

2014-06-01

47

Recent advances in thiol and sulfide reactive probes.  

Science.gov (United States)

Because of the biological relevance of thiols and sulfides such as cysteine, homocysteine, glutathione and hydrogen sulfide, their detection has attracted a great deal of research interest. Fluorescent probes are emerging as a new strategy for thiol and hydrogen sulfide analysis due to their high sensitivity, low cost, and ability to detect and image thiols in biological samples. In this short review, we have summarized recent advances in the development of thiol and hydrogen sulfide reactive fluorescent probes. These probes are compared and contrasted with regard to their designing strategies, mechanisms, photophysical properties, and/or reaction kinetics. Biological applications of these probes are also discussed. PMID:24415273

Wang, Ke; Peng, Hanjing; Wang, Binghe

2014-06-01

48

Virus-Encoded Ribonucleotide Reductases  

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Ribonucleotide reductases are encoded by many viruses, but without other enzymes of nucleotide metabolism of no obvious use. A look at the enzymes' molecular properties and their possible mutator action may give clues.

Bornemann, Claus

2014-01-01

49

Studies on alterations of the 86-rubidium efflux from rat pancreatic islets caused by thiol and thiol oxidants  

International Nuclear Information System (INIS)

The following findings were revealed by this study: 1) Oxidation-reduction (redox) of the intracellular system of glutathione influences the potassium efflux by way of an increase in the 86-rubidium efflux brought about by the oxidation of intracellular thiols. 2) The 86-rubidium efflux is not subject to change by oxidation of extracellular thiols located in the membrane, nor can it in any way be influenced by reduced glutathione of exogenous origin. 3) The potassium efflux from rat pancreatic islets, being generally known to trigger the electric activities of the beta-cell, is controlled by the oxidation-reduction of intracellular thiols rather than by that of extracellular thiols. (TRV)

1983-01-01

50

Role of endogenous thiols in intrinsic radioprotection  

Energy Technology Data Exchange (ETDEWEB)

Observations are reviewed from experiments performed to study the role of endogenous thiols in the radiation response of cells using a glutathione-deficient and a related glutathione-proficient cell strain. The effect of glutathione in the initial radical reactions was considered and the yield of single-strand DNA breaks was the end-point of the response. The rejoining of breaks and clonogenic survival were chosen as end-points when, in addition, the role of glutathione in the subsequent biochemical processes was studied. The results were interpreted to indicate that glutathione plays a role in both the radical and the biochemical reactions which follow irradiation. In the former case, it functions as a damage-restituting reactant, in general agreement with the 'competition model'. Some biochemical repair processes, in particular those concerned with the rejoining of breaks induced by radiation in the presence of oxygen or misonidazole, appear also to be critically dependent on glutathione. Due, probably, to its particular spatial distribution, endogenous glutathione is specific in the radical processes, and exogenous thiols cannot be substituted for it. No such specificity was indicated in the biochemical processes related to strand break rejoining.

Revesz, L.

1985-04-01

51

Maturation-dependent thiol loss increases chondrocyte susceptibility to apoptosis.  

Science.gov (United States)

The major aim of the current investigation was to evaluate the role of thiols during chondrocyte maturation and apoptosis. Using a thiol-sensitive fluorescent probe, we found that in chick growth plate chondrocytes, hypertrophy is accompanied by a decrease in the glutathione content. In this study, we show that the maturation-dependent loss of thiol, although not causing death of maturing chondrocytes, drastically increases susceptibility to apoptosis by oxidative and nitrosoactive stress. To investigate how the loss of thiol content in cultured chondrocytes affects the expression of the hypertrophic phenotype, we chemically manipulated intracellular thiol levels and analyzed the expression of important maturation markers. We found that thiol depletion causes a decrease in the expression of osteopontin, type X and type II collagen and a significant loss of alkaline phosphatase activity, suggesting that the expression of the hypertrophic phenotype is tightly regulated by redox levels in chondrocytes. Furthermore, severe thiol depletion profoundly affected cell survival under oxidative and nitrosoactive stress. It was concluded that the loss of thiol reserve is not only linked to the expression of the hypertrophic phenotype but also influenced chondrocyte survival, linking chondrocyte maturation and the activation of the apoptotic pathway. PMID:12674327

Teixeira, Cristina C; Rajpurohit, Ramesh; Mansfield, Kyle; Nemelivsky, Yelena V; Shapiro, Irving M

2003-04-01

52

Zeatin reductase in Phaseolus embryos  

International Nuclear Information System (INIS)

Zeatin was converted to O-xylosylzeatin in embryos of Phaseolus vulgaris . O-xylosyldihydrozeatin was also identified as a zeatin metabolite. Incubation of embryo extracts with 14C-zeatin and 14C-O-xylosylzeatin revealed that reduction preceeds the O-xylosylation of zeatin. An enzyme responsible for reducing the N6-side chain was isolated and partially purified using ammonium sulfate fractionation and affinity, gel filtration and anion exchange chromatography. The NADPH dependent reductase was zeatin specific and did not recognize cis-zeatin, ribosylzeatin, i6Ade or i6Ado. Two forms of the reductase could be separated by either gel filtration or anion exchange HPLC. The HMW isozyme (Mr. 55,000) eluted from the anion exchange column later than the LMW isozyme (Mr. 25,000). Interspecific differences in zeatin reductase activity were also detected

1989-01-01

53

Zeatin reductase in Phaseolus embryos  

Energy Technology Data Exchange (ETDEWEB)

Zeatin was converted to O-xylosylzeatin in embryos of Phaseolus vulgaris . O-xylosyldihydrozeatin was also identified as a zeatin metabolite. Incubation of embryo extracts with {sup 14}C-zeatin and {sup 14}C-O-xylosylzeatin revealed that reduction preceeds the O-xylosylation of zeatin. An enzyme responsible for reducing the N{sup 6}-side chain was isolated and partially purified using ammonium sulfate fractionation and affinity, gel filtration and anion exchange chromatography. The NADPH dependent reductase was zeatin specific and did not recognize cis-zeatin, ribosylzeatin, i{sup 6}Ade or i{sup 6}Ado. Two forms of the reductase could be separated by either gel filtration or anion exchange HPLC. The HMW isozyme (Mr. 55,000) eluted from the anion exchange column later than the LMW isozyme (Mr. 25,000). Interspecific differences in zeatin reductase activity were also detected.

Martin, R.C.; Mok, David, W.S.; Mok, M.C. (Oregon State Univ., Corvallis (USA))

1989-04-01

54

Pseudoazurin-nitrite reductase interactions.  

Science.gov (United States)

The nitrite reductase-binding site on pseudoazurin has been determined by using NMR chemical-shift perturbations. It comprises residues in the hydrophobic patch surrounding the exposed copper ligand His81 as well as several positively charged residues. The binding site is similar for both redox states of pseudoazurin, despite differences in the binding mode. The results suggest that pseudoazurin binds in a well-defined orientation. Docking simulations provide a putative structure of the complex with a binding site on nitrite reductase that has several hydrophobic and polar residues as well as a ridge of negatively charged side chains and a copper-to-copper distance of 14 A. PMID:16138306

Impagliazzo, Antonietta; Krippahl, Ludwig; Ubbink, Marcellus

2005-09-01

55

Glutathione and the redox control system trypanothione/trypanothione reductase are involved in the protection of Leishmania spp. against nitrosothiol-induced cytotoxicity  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Glutathione is the major intracellular antioxidant thiol protecting mammalian cells against oxidative stress induced by oxygen- and nitrogen-derived reactive species. In trypanosomes and leishmanias, trypanothione plays a central role in parasite protection against mammalian host defence systems by [...] recycling trypanothione disulphide by the enzyme trypanothione reductase. Although Kinetoplastida parasites lack glutathione reductase, they maintain significant levels of glutathione. The aim of this study was to use Leishmania donovani trypanothione reductase gene mutant clones and different Leishmania species to examine the role of these two individual thiol systems in the protection mechanism against S-nitroso-N-acetyl-D,L-penicillamine (SNAP), a nitrogen-derived reactive species donor. We found that the resistance to SNAP of different species of Leishmania was inversely correlated with their glutathione concentration but not with their total low-molecular weight thiol content (about 0.18 nmol/10(7) parasites, regardless Leishmania species). The glutathione concentration in L. amazonensis, L. donovani, L. major, and L. braziliensis were 0.12, 0.10, 0.08, and 0.04 nmol/10(7) parasites, respectively. L. amazonensis, that have a higher level of glutathione, were less susceptible to SNAP (30 and 100 µM). The IC50 values of SNAP determined to L. amazonensis, L. donovani, L. major, and L. braziliensis were 207.8, 188.5, 160.9, and 83 µM, respectively. We also observed that L. donovani mutants carrying only one trypanothione reductase allele had a decreased capacity to survive (~40%) in the presence of SNAP (30-150 µM). In conclusion, the present data suggest that both antioxidant systems, glutathione and trypanothione/trypanothione reductase, participate in protection of Leishmania against the toxic effect of nitrogen-derived reactive species.

P.R.T., Romão; J., Tovar; S.G., Fonseca; R.H., Moraes; A.K., Cruz; J.S., Hothersall; A.A., Noronha-Dutra; S.H., Ferreira; F.Q., Cunha.

56

Glutathione and the redox control system trypanothione/trypanothione reductase are involved in the protection of Leishmania spp. against nitrosothiol-induced cytotoxicity  

Directory of Open Access Journals (Sweden)

Full Text Available Glutathione is the major intracellular antioxidant thiol protecting mammalian cells against oxidative stress induced by oxygen- and nitrogen-derived reactive species. In trypanosomes and leishmanias, trypanothione plays a central role in parasite protection against mammalian host defence systems by recycling trypanothione disulphide by the enzyme trypanothione reductase. Although Kinetoplastida parasites lack glutathione reductase, they maintain significant levels of glutathione. The aim of this study was to use Leishmania donovani trypanothione reductase gene mutant clones and different Leishmania species to examine the role of these two individual thiol systems in the protection mechanism against S-nitroso-N-acetyl-D,L-penicillamine (SNAP, a nitrogen-derived reactive species donor. We found that the resistance to SNAP of different species of Leishmania was inversely correlated with their glutathione concentration but not with their total low-molecular weight thiol content (about 0.18 nmol/10(7 parasites, regardless Leishmania species. The glutathione concentration in L. amazonensis, L. donovani, L. major, and L. braziliensis were 0.12, 0.10, 0.08, and 0.04 nmol/10(7 parasites, respectively. L. amazonensis, that have a higher level of glutathione, were less susceptible to SNAP (30 and 100 µM. The IC50 values of SNAP determined to L. amazonensis, L. donovani, L. major, and L. braziliensis were 207.8, 188.5, 160.9, and 83 µM, respectively. We also observed that L. donovani mutants carrying only one trypanothione reductase allele had a decreased capacity to survive (~40% in the presence of SNAP (30-150 µM. In conclusion, the present data suggest that both antioxidant systems, glutathione and trypanothione/trypanothione reductase, participate in protection of Leishmania against the toxic effect of nitrogen-derived reactive species.

P.R.T. Romão

2006-03-01

57

Cerebellar thiol status and motor deficit after lactational exposure to methylmercury.  

Science.gov (United States)

This study examined the exclusive contribution of methylmercury (MeHg) exposure through maternal milk on biochemical parameters related to the thiol status (glutathione (GSH) levels, glutathione peroxidase (GPx) and glutathione reductase (GR) activities) in the cerebellums of suckling mice. The same biochemical parameters were also evaluated in the cerebellums of mothers, which were submitted to a direct oral exposure to MeHg (10 mg/L in drinking water). With regard to the relationship between cerebellar function and motor activity, the presence of signs of motor impairment was also evaluated in the offspring exposed to MeHg during lactation. After the treatment (at weaning period), the pups lactationally exposed to MeHg showed increased levels of mercury in the cerebellum compared to pups in the control group and a significant impairment in the motor performance in the rotarod apparatus. In addition, these pups showed decreased levels of GSH in the cerebellum compared to pups in the control group. In dams, MeHg significantly increased the levels of cerebellar GSH and the activities of cerebellar GR. However, this was not observed in pups. This study indicates that (1) the exposure of lactating mice to MeHg causes significant impairments in motor performance in the offspring which may be related to a decrease in the cerebellar thiol status and (2) the increased GSH levels and GR activity, observed only in the cerebellums of MeHg-exposed dams, could represent compensatory pathophysiologic responses to the oxidative effects of MeHg toward endogenous GSH. PMID:16564521

Franco, Jeferson L; Teixeira, Adriana; Meotti, Flávia C; Ribas, Camila M; Stringari, James; Garcia Pomblum, Solange C; Moro, Angela M; Bohrer, Denise; Bairros, André V; Dafre, Alcir L; Santos, Adair R S; Farina, Marcelo

2006-09-01

58

Rapid photochemical surface patterning of proteins in thiol-ene based microfluidic devices  

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The suitable optical properties of thiol-ene polymers combined with the ease of modifying their surface for the attachment of recognition molecules make them ideal candidates in many biochip applications. This paper reports the rapid one-step photochemical surface patterning of biomolecules in microfluidic thiol-ene chips. This work focuses on thiol-ene substrates featuring an excess of thiol groups at their surface. The thiol-ene stoichiometric composition can be varied to precisely control ...

Lafleur, Josiane P.; Kwapiszewski, Radoslaw; Jensen, Thomas G.; Kutter, Joerg P.

2013-01-01

59

Cell-type specific requirements for thiol/disulfide exchange during HIV-1 entry and infection  

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Full Text Available Abstract Background The role of disulfide bond remodeling in HIV-1 infection is well described, but the process still remains incompletely characterized. At present, the data have been predominantly obtained using established cell lines and/or CXCR4-tropic laboratory-adapted virus strains. There is also ambiguity about which disulfide isomerases/ reductases play a major role in HIV-1 entry, as protein disulfide isomerase (PDI and/or thioredoxin (Trx have emerged as the two enzymes most often implicated in this process. Results We have extended our previous findings and those of others by focusing on CCR5-using HIV-1 strains and their natural targets - primary human macrophages and CD4+ T lymphocytes. We found that the nonspecific thiol/disulfide exchange inhibitor, 5,5'-dithiobis(2-nitrobenzoic acid (DTNB, significantly reduced HIV-1 entry and infection in cell lines, human monocyte-derived macrophages (MDM, and also phytohemagglutinin (PHA-stimulated peripheral blood mononuclear cells (PBMC. Subsequent studies were performed using specific anti-PDI or Trx monoclonal antibodies (mAb in HIV-1 envelope pseudotyped and wild type (wt virus infection systems. Although human donor-to-donor variability was observed as expected, Trx appeared to play a greater role than PDI in HIV-1 infection of MDM. In contrast, PDI, but not Trx, was predominantly involved in HIV-1 entry and infection of the CD4+/CCR5+ T cell line, PM-1, and PHA-stimulated primary human T lymphocytes. Intriguingly, both PDI and Trx were present on the surface of MDM, PM-1 and PHA-stimulated CD4+ T cells. However, considerably lower levels of Trx were detected on freshly isolated CD4+ lymphocytes, compared to PHA-stimulated cells. Conclusions Our findings clearly demonstrate the role of thiol/disulfide exchange in HIV-1 entry in primary T lymphocytes and MDM. They also establish a cell-type specificity regarding the involvement of particular disulfide isomerases/reductases in this process and may provide an explanation for differences among previously published studies. More importantly, from an in vivo perspective, the preferential utilization of PDI may be relevant to the HIV-1 entry and establishment of virus reservoirs in resting CD4+ cells, while the elevated levels of Trx reported in the chronic stages of HIV-1 infection may facilitate the virus entry in macrophages and help to sustain high viremia during the decline of T lymphocytes.

Stantchev Tzanko S

2012-12-01

60

ORIGINAL ARTICLE: Protein Thiols in Essential Hypertension Patients  

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Full Text Available Background: Essential hypertension is one of the most prevalent diseases of the world and is an unequivocal risk factor for cardiovascular morbidity and mortality. Several previous studies have shown that increased free radical activity is suggested to play an important role in the lipid peroxidation and protein oxidationof cellular structures causing cell injury and is implicated in the pathogenesis of vascular disease and essential hypertension is one ofthem. The thiols groups on proteins are known to play a major role in maintaining the antioxidant status of the body. Aims and Objectives: The current study was designed to find out the levels of such protein bound thiols in essential hypertension patients. Materials and Methods: The study was conducted on 45 essential hypertension patients and 25 healthy subjects without any underlying medical disorder as controls. Patients were divided into three groups according to the 2003 European Society of Hypertension-European Society of Cardiology (ESH/ ESC guidelines (grade I, II,III. Serum and urine protein thiols were determined by spectrophotometric methods using dithionitrobenzoic acid (DTNB andcorrelated with blood pressure (BP. Results: There was a significant decrease in serum protein thiols in essential hypertensive patients compared to healthy controls (p<0.01 and correlated positively with grade II and grade III essential hypertension. In urine samples there was a significant increase in protein and a decrease in protein bound thiols (p<0.01 which also correlated positively with grade II and grade III essential hypertension. Conclusions: Protein bound thiols; the major antioxidants in the body are decreased in essential hypertensive patients. Due to increased consumption of protein bound thiols in such oxidative environment, there was a significant decrease in protein bound thiols in urine.

Jagadish. B. Ingin

2012-01-01

 
 
 
 
61

Fast and Highly Efficient Solid State Oxidation of Thiols  

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A fast and efficient solid state method for the chemoselective room temperature oxidative coupling of thiols to afford their corresponding disulfides using inexpensive and readily available moist sodiumperiodate as the reagent is described. The reaction was applicable to a variety of thiols giving high yields after short reaction times. Comparison of yield/time ratios of this method with some of those reported in the literature shows the superiority of this reagent over others under these con...

Morteza Montazerozohori; Shiva Joohari; Bahador Karami; Nasrin Haghighat

2007-01-01

62

The binding sites on human heme oxygenase-1 for cytochrome p450 reductase and biliverdin reductase.  

Science.gov (United States)

Human heme oxygenase-1 (hHO-1) catalyzes the NADPH-cytochrome P450 reductase-dependent oxidation of heme to biliverdin, CO, and free iron. The biliverdin is subsequently reduced to bilirubin by biliverdin reductase. Earlier kinetic studies suggested that biliverdin reductase facilitates the release of biliverdin from hHO-1 (Liu, Y., and Ortiz de Montellano, P. R. (2000) J. Biol. Chem. 275, 5297-5307). We have investigated the binding of P450 reductase and biliverdin reductase to truncated, soluble hHO-1 by fluorescence resonance energy transfer and site-specific mutagenesis. P450 reductase and biliverdin reductase bind to truncated hHO-1 with Kd = 0.4 +/- 0.1 and 0.2 +/- 0.1 microm, respectively. FRET experiments indicate that biliverdin reductase and P450 reductase compete for binding to truncated hHO-1. Mutation of surface ionic residues shows that hHO-1 residues Lys18, Lys22, Lys179, Arg183, Arg198, Glu19, Glu127, and Glu190 contribute to the binding of cytochrome P450 reductase. The mutagenesis results and a computational analysis of the protein surfaces partially define the binding site for P450 reductase. An overlapping binding site including Lys18, Lys22, Lys179, Arg183, and Arg185 is similarly defined for biliverdin reductase. These results confirm the binding of biliverdin reductase to hHO-1 and define binding sites of the two reductases. PMID:12626517

Wang, Jinling; de Montellano, Paul R Ortiz

2003-05-30

63

Efficient functionalization of oxide-free silicon(111) surfaces: thiol-yne versus thiol-ene click chemistry.  

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Thiol-yne click (TYC) chemistry was utilized as a copper-free click reaction for the modification of alkyne-terminated monolayers on oxide-free Si(111) surfaces, and the results were compared with the analogous thiol-ene click (TEC) chemistry. A wide range of thiols such as 9-fluorenylmethoxy-carbonyl cysteine, thio-?-d-glucose tetraacetate, thioacetic acid, thioglycerol, thioglycolic acid, and 1H,1H,2H,2H-perfluorodecanethiol was immobilized using TYC under photochemical conditions, and all modified surfaces were characterized by static water contact angle measurements, X-ray photoelectron spectroscopy (including a simulation thereof by density functional calculations), and infrared absorption reflection spectroscopy. Surface-bound TYC proceeds with an efficiency of up to 1.5 thiols per alkyne group. This high surface coverage proceeds without oxidizing the Si surface. TYC yielded consistently higher surface coverages than TEC, due to double addition of thiols to alkyne-terminated monolayers. This also allows for the sequential and highly efficient attachment of two different thiols onto an alkyne-terminated monolayer. PMID:23528051

Bhairamadgi, Nagendra S; Gangarapu, Satesh; Caipa Campos, Mabel A; Paulusse, Jos M J; van Rijn, Cees J M; Zuilhof, Han

2013-04-01

64

Comparison of concentration changes in nonprotein SH-groups, reduced glutathione and glutathione reductase activity in some radioprotection methods  

International Nuclear Information System (INIS)

The concentration dynamics of nonprotein SH-groups, reduced glutathione, and glutathione reductase activity were compared in different rat tissues in the course of the first hour following intraperitoneal administration of radioprotectively effective doses of cystamine or of a combination of cystamine with mexamine. The results obtained confirmed the participation of endogenous reduced glutathione in the radioprotective effect of cystamine in the rat organism, showing, however, that the increase in the concentration of reduced glutathione alone does not explain the total concentration increase of nonprotein thiols after the administration of radioprotective agents. With respect to the increase in the concentration of both SH-groups and reduced glutathione, the observed reduction in glutathione reductase activity may be due to the action of the regulatory mechanism. (author)

1980-01-01

65

Fatty acyl-CoA reductase  

Energy Technology Data Exchange (ETDEWEB)

The present invention relates to bacterial enzymes, in particular to an acyl-CoA reductase and a gene encoding an acyl-CoA reductase, the amino acid and nucleic acid sequences corresponding to the reductase polypeptide and gene, respectively, and to methods of obtaining such enzymes, amino acid sequences and nucleic acid sequences. The invention also relates to the use of such sequences to provide transgenic host cells capable of producing fatty alcohols and fatty aldehydes.

Reiser, Steven E.; Somerville, Chris R.

1998-12-01

66

Ferric iron reductase of Rhodopseudomonas sphaeroides.  

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Ferric iron reductase activity was examined in the facultative photosynthetic bacterium Rhodopseudomonas sphaeroides. The specific activities of extracts from cells grown under phototrophic and aerobic conditions were similar and not affected by the concentration of iron in the growth media. The activity was resolved by ion-exchange column chromatography into two fractions, designated iron reductase A and iron reductase B, with molecular weights of 41,000 and 32,000, respectively. Both of the...

1985-01-01

67

Protection by thiols against poisoning by radiomimetic agents. Chapter 8  

International Nuclear Information System (INIS)

A review is presented of reports of studies aimed at detecting a protective effect of thiols against radiomimetic alkylating agents such as those used in cancer therapy (nitrogen mustards (HN2), sarcolysine, busulfan, etc.). Protection by thiols against alkylating agents has been observed in mammals, plant cells, bacteria, isolated mammalian cells and in model systems. The lack of correlation between the protective power of various thiols against radiomimetic agents and ionizing radiations indicates that different mechanisms are involved. Studies have been made of the toxicity of the protector and the competition factor, increased excretion of detoxication products of alkylating agents, decreased alkylation of DNA and RNA both in vivo and in vitro, the protection of hematopoietic tissues, tumours and the adrenal cortex, and the modification of the effects of nitrosoalkylamines, carbon tetrachloride and fungistatics by thiols. The restriction of DNA alkylation by the competitive removal of radiomimetic agents is thought to account for the protective effect of thiols against radiomimetic agents. (U.K.)

1975-01-01

68

21 CFR 864.7375 - Glutathione reductase assay.  

Science.gov (United States)

...2009-04-01 2009-04-01 false Glutathione reductase assay. 864.7375 Section...Hematology Kits and Packages § 864.7375 Glutathione reductase assay. (a) Identification. A glutathione reductase assay is a device used...

2009-04-01

69

Thiol and non-thiol antioxidants effect radiation damage expressed by IEC-6 cells  

International Nuclear Information System (INIS)

Full text: The epithelial lining of the GI mucosal surface is traditionally viewed as a passive barrier serving a largely protective function. Recently, enterocytes have been seen to function as sensitive indicators of oxidative stress, with defined responses to shifts in the oxidative balance. Radiation damage, long recognized as the result of the generation of reactive oxygen species, would theoretically be modulated by the presence of radical scavenging anti-oxidants. Cultures of IEC-6 cells, a model for the gastrointestinal epithelium were found to have lower numbers of adherent cells in response either n-acetyl cysteine (NAC) or l-ascorbate in the medium. In both cases the response was dose dependent, with inhibition in response to l-ascorbate well established by 48 hours. However, in contrast to the thiol antioxidant NAC where a late recovery was observed at high dose, no statistically significant increase in adherent cell numbers were observed with high dose l-ascorbate, and adherent cell numbers actually fell off with time. Exposure to antioxidants potentiated the damage from x-ray irradiation further reducing cell numbers. While we have previously shown that this damage was not associated with mitotic delay or inhibition of proliferation, the mechanism of this response remains undefined. Non-adherent cells were found to increase with dose in the presence of antioxidants with those cells having morphology consistent with apoptotic cells including nuclear condensation, and blabbing. Annexin V cells increased in the non-adherent cell layer, but the numbers did not seem to account for the severe reduction in cell numbers observed. It has been suggested that a p53 mutation alters the response to oxidative damage in these cells via a thiol containing motif sensitive to the cellular glutathione pool resulting in an automatic signal to release from the basement membrane, however it does not explain the similarity in effects to ascorbate

2003-08-17

70

Interaction of thiols and non-thiol ·OH scavengers in the modification of radiation-induced DNA damage  

International Nuclear Information System (INIS)

Oxygen has long been known to sensitize cells to the lethal effects of ionizing radiation and is widely believed to do so by the fixation of potentially reversible radical damage to cellular DNA. A number of studies have suggested that this widely observed oxygen enhancement of cell killing requires the presence of reduced thiols. Published in vitro studies of the modification of DNA damage by glutathione or other thiols have generally shown peak oxygen enhancement ratios (OERs) much higher than those observed for cell killing. However, these studies measured loss of DNA transforming activity or induction of single-strand DNA breaks (SSBs), related endpoints which are not thought to represent lethal lesions, rather than double-strand breaks (DSBs), which are generally believed to be the dominant lethal lesions from ionizing radiation. In addition, non-thiol scavengers of OH radicals were not generally present. There is also evidence that, in addition to their protective effects, some non-thiol ·OH scavengers can produce radicals which are damaging to DNA under anoxic conditions. In the present investigation, the authors have adapted a previously used in vitro model system to simultaneously investigate the effects on radiation-induced single- and double-strand DNA breaks of various combinations of glutathione and glycerol, a widely used non-thiol scavenger, in the presence and absence of oxygen

1994-10-01

71

Reversible inactivation of CO dehydrogenase with thiol compounds.  

Science.gov (United States)

Carbon monoxide dehydrogenase (CO dehydrogenase) from Oligotropha carboxidovorans is a structurally characterized member of the molybdenum hydroxylase enzyme family. It catalyzes the oxidation of CO (CO+H2O?CO2+2e(-)+2H(+)) which proceeds at a unique [CuSMo(O)OH] metal cluster. Because of changing activities of CO dehydrogenase, particularly in subcellular fractions, we speculated whether the enzyme would be subject to regulation by thiols (RSH). Here we establish inhibition of CO dehydrogenase by thiols and report the corresponding Ki-values (mM): l-cysteine (5.2), d-cysteine (9.7), N-acetyl-l-cysteine (8.2), d,l-homocysteine (25.8), l-cysteine-glycine (2.0), dithiothreitol (4.1), coenzyme A (8.3), and 2-mercaptoethanol (9.3). Inhibition of the enzyme was reversed by CO or upon lowering the thiol concentration. Electron paramagnetic resonance spectroscopy (EPR) and X-ray absorption spectroscopy (XAS) of thiol-inhibited CO dehydrogenase revealed a bimetallic site in which the RSH coordinates to the Cu-ion as a third ligand {[Mo(VI)(O)OH(2)SCu(I)(SR)S-Cys]} leaving the redox state of the Cu(I) and the Mo(VI) unchanged. Collectively, our findings establish a regulation of CO dehydrogenase activity by thiols in vitro. They also corroborate the hypothesis that CO interacts with the Cu-ion first. The result that thiol compounds much larger than CO can freely travel through the substrate channel leading to the bimetallic cluster challenges previous concepts involving chaperone function and is of importance for an understanding how the sulfuration step in the assembly of the bimetallic cluster might proceed. PMID:24717648

Kreß, Oliver; Gnida, Manuel; Pelzmann, Astrid M; Marx, Christian; Meyer-Klaucke, Wolfram; Meyer, Ortwin

2014-05-01

72

Inactivation of ribonuclease inhibitor by thiol-disulfide exchange.  

Science.gov (United States)

Porcine ribonuclease inhibitor (RI) contains 30 1/2-cystinyl residues, all of which occur in the reduced form. Reaction of the native protein with 5,5'-dithiobis (2-nitrobenzoic acid) resulted in the release of 30 mol of the product 5-mercapto-2-nitrobenzoate, and the loss of the RNase inhibitory activity. A linear relationship between the degree of modification and inactivation was observed. The rate of modification was greatly increased in the presence of 6 M guanidinium HCl. Reaction with substoichiometric amounts of 5,5'-dithiobis(2-nitrobenzoic acid) was found to yield a mixture of fully reduced active molecules, and fully oxidized inactive ones, but no partially oxidized forms were detected. This suggests that an "all-or-none" type of modification and inactivation took place. All 1/2-cystinyl residues in the inactive, monomeric inhibitor had formed disulfide bridges, judged by the absence of either free thiol groups or mixed disulfides with 5-mercapto-2-nitrobenzoate. This fully disulfide-cross-linked molecule had an open conformation compared to the native one, as shown by gel filtration and limited proteolysis. Reaction of phenylarsinoxide with vicinal dithiols yields products that are much more stable than those with monothiols. Titration of RI with this reagent yielded complete inactivation at a reagent/thiol ratio of 0.5. Taken together, these observations suggest that the thiol groups in RI have a diminished reactivity due to three-dimensional constraints. After the initial modification of a small number of thiol groups, a conformational change occurs which causes an increase in reactivity of the remaining thiols. The thiol groups are situated close enough together to permit the formation of 15 disulfide bridges in the inactive molecule. PMID:1447207

Fominaya, J M; Hofsteenge, J

1992-12-01

73

Effect of thiol group on the curing process of alkaline developable photo-resists  

International Nuclear Information System (INIS)

Photosensitivity of a conventional radical photo-initiator in an alkaline developable photoresist is boosted by substitution with a thiol group. Evidence is presented that the thiol group acts via chain transfer mechanism

1999-08-24

74

5-Furan-2yl[1,3,4]oxadiazole-2-thiol, 5-Furan-2yl-4H [1,2,4] triazole-3-thiol and Their Thiol-Thione Tautomerism  

Directory of Open Access Journals (Sweden)

Full Text Available 5-Furan-2-yl[1,3,4]oxadiazole-2-thiol (Ia and 5-furan-2-yl-4H-[1,2,4]-triazole-3-thiol (Ib were synthesized from furan-2-carboxylic acid hydrazide. Mannich basesand methyl derivatives were then prepared. The structures of the synthesized compoundswere confirmed by elemental analyses, IR and 1H-NMR spectra. Their thiol-thione tautomericequilibrium is described.

A. Cansız

2005-02-01

75

5-Furan-2yl[1,3,4]oxadiazole-2-thiol, 5-Furan-2yl-4H [1,2,4] triazole-3-thiol and Their Thiol-Thione Tautomerism  

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5-Furan-2-yl[1,3,4]oxadiazole-2-thiol (Ia) and 5-furan-2-yl-4H-[1,2,4]-triazole-3-thiol (Ib) were synthesized from furan-2-carboxylic acid hydrazide. Mannich basesand methyl derivatives were then prepared. The structures of the synthesized compoundswere confirmed by elemental analyses, IR and 1H-NMR spectra. Their thiol-thione tautomericequilibrium is described.

2005-01-01

76

Prediction of reversibly oxidized protein cysteine thiols using protein structure properties  

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Protein cysteine thiols can be divided into four groups based on their reactivities: those that form permanent structural disulfide bonds, those that coordinate with metals, those that remain in the reduced state, and those that are susceptible to reversible oxidation. Physicochemical parameters of oxidation-susceptible protein thiols were organized into a database named the Balanced Oxidation Susceptible Cysteine Thiol Database (BALOSCTdb). BALOSCTdb contains 161 cysteine thiols that undergo...

Sanchez, Ricardo; Riddle, Megan; Woo, Jongwook; Momand, Jamil

2008-01-01

77

Octaheme nitrite reductases: structure and properties.  

Science.gov (United States)

Octaheme oxidoreductases are widespread among various bacterial taxa involved in the biogeochemical nitrogen cycle. The evolution of octaheme oxidoreductases of the nitrogen cycle from the evolutionarily more ancient pentaheme nitrite reductases was accompanied by changes in function from reduction of nitrogen oxides to their oxidation under changing environmental conditions. Octaheme nitrite reductases, which are the subject of the present review, are of a transitional form that combines structural and functional characteristics of pentaheme reductases and octaheme oxidases and possesses a number of unique features typical of only this family of enzymes. The review summarizes data on structure-function investigations of the family of octaheme nitrite reductases. Emphasis is given to comparison of the structures and functions of octaheme nitrite reductases and other multiheme oxidoreductases of the nitrogen cycle. PMID:23157293

Tikhonova, T V; Trofimov, A A; Popov, V O

2012-10-01

78

Surface functionalized thiol-ene waveguides for fluorescence biosensing in microfluidic devices  

DEFF Research Database (Denmark)

Thiol-ene polymers possess physical, optical, and chemical characteristics that make them ideal substrates for the fabrication of optofluidic devices. In this work, thiol-ene polymers are used to simultaneously create microfluidic channels and optical waveguides in one simple moulding step. The reactive functional groups present at the surface of the thiol-ene polymer are subsequently used for the rapid, one step, site-specific functionalization of the waveguide with biological recognition molecules. It was found that while the bulk properties and chemical surface properties of thiol-ene materials vary considerably with variations in stoichiometric composition, their optical properties remain mostly unchanged with an average refractive index value of 1.566 ± 0.008 for thiol-ene substrates encompassing a range from 150% excess ene to 90% excess thiol. Microfluidic chips featuring thiol-ene waveguides were fabricated from 40% excess thiol thiol-ene to ensure the presence of thiol functional groups at the surface of the waveguide. Biotin alkyne was photografted at specific locations using a photomask, directly at the interface between the microfluidic channel and the thiol-ene waveguide prior to conjugation with fluorescently labeled streptavidin. Fluorescence excitation was achieved by launching light through the thiol-ene waveguide, revealing bright fluorescent patterns along the channel/waveguide interface. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Feidenhans'l, N.A.; Lafleur, Josiane P.

2014-01-01

79

Surface functionalized thiol-ene waveguides for ï¬?uorescence biosensing in microï¬?uidic devices  

DEFF Research Database (Denmark)

Thiol-ene polymers possess physical, optical, and chemical characteristics thatmake them ideal substrates for the fabrication of optofluidic devices. In this work, thiol-ene polymers are used to simultaneously create microfluidic channels and optical waveguides in one simple moulding step. The reactive functional groups present at the surface of the thiol-ene polymer are subsequently used for the rapid, one step, site-specific functionalization of the waveguide with biological recognition molecules. It was found that while the bulk properties and chemical surface properties of thiol-ene materials vary considerably with variations in stoichiometric composition, their optical properties remain mostly unchanged with an average refractive index value of 1.566 ± 0.008 for thiol-ene substrates encompassing a range from 150% excess ene to 90% excess thiol. Microfluidic chips featuring thiol-ene waveguides were fabricated from 40% excess thiol thiol-ene to ensure the presence of thiol functional groups at the surface of the waveguide. Biotin alkyne was photografted at specific locations using a photomask, directly at the interface between the microfluidic channel and the thiol-ene waveguide prior to conjugation with fluorescently labeled streptavidin. Fluorescence excitation was achieved by launching light through the thiol-ene waveguide, revealing bright fluorescent patterns along the channel/waveguide interface

Feidenhans'l, Nikolaj Agentoft; Lafleur, Josiane P.

2013-01-01

80

Preparation of Novel Hydrolyzing Urethane Modified Thiol-Ene Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Novel tetra-functional hydrolyzing monomers were prepared from the reaction of TEOS and select alkene-containing alcohols, ethylene glycol vinyl ether or 2-allyloxy ethanol, and combined with trimethylolpropane tris(3-mercaptopropionate (tri-thiol in a thiol-ene “click” polymerization reaction to produce clear, colorless thiol-ene networks using both radiation and thermal-cure techniques. These networks were characterized for various mechanical characteristics, and found to posses Tg’s (DSC, hardness, tack, and thermal stability (TGA consistent with their molecular structures. A new ene-modified urethane oligomer was prepared based on the aliphatic polyisocyanate Desmodur® N 3600 and added to the thiol-ene hydrolyzable network series in increasing amounts, creating a phase-segregated material having two Tg’s. An increase in water absorption in the ene-modified urethane formulations leading to a simultaneous increase in the rate of hydrolysis was supported by TGA data, film hardness measurements, and an NMR study of closely related networks. This phenomenon was attributed to the additional hydrogen bonding elements and polar functionality brought to the film with the addition of the urethane segment. SEM was utilized for visual analysis of topographical changes in the film’s surface upon hydrolysis and provides support for surface-driven erosion. Coatings prepared in this study are intended for use as hydrolyzing networks for marine coatings to protect against ship fouling.

Bridget S. Confait

2011-10-01

 
 
 
 
81

Di-heterometalation of thiol-functionalized peptide nucleic acids.  

Science.gov (United States)

As a proof-of-principle, two hetero-bimetallic PNA oligomers containing a ruthenium(II) polypyridyl and a cyclopentadienyl manganese tricarbonyl complex have been prepared by serial combination of solid-phase peptide coupling and in-solution thiol chemistry. Solid-phase N-terminus attachment of Ru(II)-polypyridyl carboxylic acid derivative, C1, onto the thiol-functionalized PNA backbone (H-a-a-g-t-c-t-g-c-linker-cys-NH 2) has been performed by standard peptide coupling method. As two parallel approaches, the strong affinity of thiols for maleimide and haloacetyl group has been exploited for subsequent post-SPPS addition of cymantrene-based organometallic cores, C2 and C3. Michael-like addition and thioether ligation of thiol functionalized PNA1 (H-gly-a-a-g-t-c-t-g-c-linker-cys-NH 2) and PNA2 (C1-a-a-g-t-c-t-g-c-linker-cys-NH 2) to cymantrene maleimide and chloroacetyl derivatives, C2 and C3, respectively, has been performed. The synthesized ruthenium(II)-cymantrenyl PNA oligomers have been characterized by mass spectrometry (ESI-MS) and IR spectroscopy. The distinct Mn-CO vibrational IR stretches, between 1,924-2,074 cm (-1) , have been used as markers to confirm the presence of cymantrenyl units in the PNA sequences and the purity of the HPLC-purified PNA thioethers assessed using LC-MS. PMID:23422249

Joshi, Tanmaya; Patra, Malay; Spiccia, Leone; Gasser, Gilles

2013-01-01

82

Production of dithioselenides from thiols and selenium dioxide  

International Nuclear Information System (INIS)

The authors have established that the slow addition of a methanol solution of selenium dioxide to solutions of thiols in dioxane (molar ratio 2:1) leads to the formation of the corresponding thioselenides without side compounds. Under the influence of bases, light, or heat above 1500C these compounds eliminate amorphous selenium and are converted quantitatively into the known disulfides

1986-07-20

83

Thiol-ene enabled detection of thiophosphorylated kinase substrates.  

Science.gov (United States)

Protein phosphorylation is a ubiquitous posttranslational modification that regulates cell signaling in both prokaryotes and eukaryotes. Although the study of phosphorylation has made great progress, several major hurdles remain, including the difficulty of the assignment of endogenous substrates to a discrete kinase and of global phosphoproteomics investigations. We have developed a novel chemical strategy for detecting phosphorylated proteins. This method utilizes adenosine 5'-O-(3-thiotriphosphate) (ATP?S), which results in the transfer of a thiophosphate moiety by a kinase to its substrate(s). This group can subsequently be employed as a nucleophilic handle to promote protein detection. To selectively label thiophosphorylated proteins, cellular thiols (e.g., cysteine-containing proteins) must first be blocked. Most common cysteine-capping strategies rely upon the nucleophilicity of the sulfur group and would therefore also modify the thiophosphate moiety. We hypothesized that the radical-mediated thiol-ene reaction, however, would be selective for cysteine over thiophosphorylated amino acids due to the differences in the electronics and pKa values between these groups. Here, we report rapid and specific tagging of thiophosphorylated proteins in vitro following chemoselective thiol capping using the thiol-ene reaction. PMID:23668631

Garber, Kathleen C A; Carlson, Erin E

2013-08-16

84

Effect of thiols on macroconidia of Fusarium sulphureum.  

Science.gov (United States)

Treatment of Fusarium sulphureum macroconidial cells with five thiols alters their morphology. Macroconidial cells incubated in dithiothreitol (DTT), dithioerythritol (DTE), or thiourea differentiate into thick-walled, chlamydospore-like cells (thiol-induced spores). These cells appear similar in size and shape to chlamydospores in the light microscope, but differ markedly in cell wall structure when viewed in the electron microscope (EM). Incubation of macroconidia with both DTT and DTE also leads to the formation of large swollen cells (giant cells) which have a parietal cytoplasm and electron-tranparent cell walls; most of these giant cells lyse within 3 to 7 days of incubation. Thiourea-induced spores are characterized by the deposition of a thick, electron-dense, extracellular layer and an accumulation of mitochondria. DTT and DTE, at the concentrations used, inhibit macroconidial germination while thiourea, mercaptoethanol, and cysteine do not. With the latter three thiols, the newly formed hyphal cells become elongated with either one or both ends swollen. Mercaptoethanol-treated cells contain an abundance of mitochondria. The DTT-induced spore differs from both macroconidia and chlamydospores with respect to cellular lipid and cell wall composition. While the thiols have different effects on the macroconidia, the fact that they all induce cell expansion suggests that they react at some common sites. PMID:476543

Barran, L R; Schneider, E F

1979-05-01

85

Transsulfuration pathway thiols and methylated arginines: the hunter community study  

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Background: Serum homocysteine, when studied singly, has been reported to be positively associated both with the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine [ADMA, via inhibition of dimethylarginine dimethylaminohydrolase (DDAH) activity] and with symmetric dimethylarginine (SDMA). We investigated combined associations between transsulfuration pathway thiols, including homocysteine, and serum ADMA and SDMA concentrations at population level. <...

Mangoni, Arduino A.; Zinellu, Angelo; Carru, Ciriaco; Attia, John R.; Mcevoy, Mark

2013-01-01

86

Organo-Soluble Chiral Thiol-Monolayer-Protected Gold Nanorods.  

Science.gov (United States)

Here, we report the synthesis and characterization of organo-soluble chiral thiol-monolayer-protected gold nanorods. The resulting gold nanorods respectively covered with two opposite enantiomers via the strong covalent Au-S linkage were found to not only...

A. Urbas D. Yu L. Dai Q. Li Y. Li

2011-01-01

87

Alkyl hydroperoxide reductase repair by Helicobacter pylori methionine sulfoxide reductase.  

Science.gov (United States)

Protein exposure to oxidants such as HOCl leads to formation of methionine sulfoxide (MetSO) residues, which can be repaired by methionine sulfoxide reductase (Msr). A Helicobacter pylori msr strain was more sensitive to HOCl-mediated killing than the parent. Because of its abundance in H. pylori and its high methionine content, alkyl hydroperoxide reductase C (AhpC) was hypothesized to be prone to methionine oxidation. AhpC was expressed as a recombinant protein in Escherichia coli. AhpC activity was abolished by HOCl, while all six methionine residues of the enzyme were fully to partially oxidized. Upon incubation with a Msr repair mixture, AhpC activity was restored to nonoxidized levels and the MetSO residues were repaired to methionine, albeit to different degrees. The two most highly oxidized and then Msr-repaired methionine residues in AhpC, Met101 and Met133, were replaced with isoleucine residues by site-directed mutagenesis, either individually or together. E. coli cells expressing variant versions were more sensitive to t-butyl hydroperoxide than cells expressing native protein, and purified AhpC variant proteins had 5% to 39% of the native enzyme activity. Variant proteins were still able to oligomerize like the native version, and circular dichroism (CD) spectra of variant proteins revealed no significant change in AhpC conformation, indicating that the loss of activity in these variants was not related to major structural alterations. Our results suggest that both Met101 and Met133 residues are important for AhpC catalytic activity and that their integrity relies on the presence of a functional Msr. PMID:24097943

Benoit, Stéphane L; Bayyareddy, Krishnareddy; Mahawar, Manish; Sharp, Joshua S; Maier, Robert J

2013-12-01

88

Inhibition of glutathione reductase by oncomodulin.  

Science.gov (United States)

Evidence for a specific interaction between oncomodulin and glutathione reductase is presented. Glutathione reductase (EC 1.6.4.2) isolated from either the bovine intestinal mucosa or the rat liver was bound in a Ca2(+)-dependent manner to oncomodulin which was covalently attached to Sepharose. In addition, glutathione reductase was able to catalyze the reduction of the disulfide-linked dimer of oncomodulin. The interaction of these proteins could also be indirectly demonstrated by monitoring glutathione reductase activity since oncomodulin was shown to inhibit the enzyme in a dose-dependent manner with an apparent IC50 of approximately 5 microM. The kinetic analysis of the oncomodulin-dependent effects on glutathione reductase activity indicates that oncomodulin interacts at a site other than the active site as the oncomodulin-induced inhibition was of the noncompetitive type. The in vivo inhibition of glutathione reductase appears to be an oncomodulin-specific effect as closely related members of the troponin C superfamily such as rabbit (pI 5.5) or carp (pI 4.25) parvalbumins, as well as calmodulin, failed to affect the activity of this enzyme. The present in vitro study indicating that oncomodulin can regulate the activity of glutathione reductase could be very significant with respect to the elucidation of a physiological role for oncomodulin. PMID:2306116

Palmer, E J; MacManus, J P; Mutus, B

1990-02-15

89

Thiol adsorption on metal oxides: an approach for selective deposition on zinc oxide nanoparticles  

Science.gov (United States)

We have previously discovered a novel, facile approach to encapsulate ZnO nanorods within thiol complexes. This approach results in a thiol uptake of 30-40% and a 400-500 nm thick thiol-Zn-thiol complex encapsulation layer surrounding ZnO nanorods. By controlling experimental parameters, it is possible to control the thiol deposition, enabling less uptake, which results in a surface monolayer instead of encapsulation. Through this approach, thiol modification of other metal oxide materials, namely TiO2, Al2O3, and MgO, has been attempted. FTIR analysis indicates that thiol adsorption occurs only on ZnO; chemisorption of thiols on other nanoparticles is not evident. Ultrahigh vacuum single crystal adsorption studies demonstrate that ZnO(0001) is also more susceptible to thiol monolayer formation, as evidenced by lack of methanethiol adsorption on TiO2(110) and MgO(0001). These results indicate that the facile thiol modification approach opens a new avenue for surface modification of multi-component metal oxide materials by enabling selective thiol modification of ZnO. This work has potential applicability for creating multiple ligand-functionalized materials, which could be useful for the design of novel multiplexing sensors and photovoltaics.

Soares, Jason W.; Steeves, Diane M.; Singh, Jagdeep; Im, Jisun; Whitten, James E.

2011-02-01

90

Selective irreversible inhibitors of aldose reductase.  

Science.gov (United States)

A series of 5-substituted-1,3-dioxo-1H-benz[de]isoquinoline-2(3H)-acetic acid analogues have been examined as irreversible inhibitors of aldose reductase. The 5-alpha-bromoacetamide and 5-alpha-iodoacetamide analogues 5 and 6 gave irreversible inhibition of aldose reductase while the 5-alpha-chloroacetamide analogue 3 did not show this type of inhibition. Protection studies indicate that irreversible inhibitions are occurring at the inhibitor binding site. Comparative irreversible inhibition studies with rat lens aldose reductase (RLAR) and rat kidney aldehyde reductase (RKALR) indicate that 5-alpha-haloacetamide analogues 5 and 6 are much more effective inhibitors of RLAR. PMID:1552504

Smar, M W; Ares, J J; Nakayama, T; Itabe, H; Kador, P F; Miller, D D

1992-03-20

91

5 alpha-reductase deficiency without hypospadias.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A boy aged 4 with penoscrotal hypospadias and his brother aged 12 with micropenis had typical changes of homozygous 5 alpha-reductase deficiency. After three injections of chorionic gonadotrophin there was a trivial rise in plasma dihydrotestosterone with a normal increase in plasma testosterone. Urine steroid chromatography showed abnormally high 5 beta: 5 alpha ratios and 5 alpha-reductase activity was appreciably reduced in genital skin fibroblasts. The results indicate that 5 alpha-reduct...

Ng, W. K.; Taylor, N. F.; Hughes, I. A.; Taylor, J.; Ransley, P. G.; Grant, D. B.

1990-01-01

92

The oxidation of ebselen metabolites to thiol oxidants catalyzed by liver microsomes and perfused rat liver.  

Science.gov (United States)

The oxidation of 2-(methylseleno)benzanilide and 2-selenylbenzanilide, metabolites of the antioxidant drug ebselen, was examined in reactions catalyzed by rat, pig, and guinea pig liver microsomes and in perfused rat liver. Microsomes from all three species catalyzed NADPH- and oxygen-dependent oxidation of the selenide and the selenol to thiol-reactive metabolites. The oxidation product of the selenide was similar in properties to the chemically synthesized selenoxide [2-(methylseleninyl)benzanilide]. The selenoxide oxidized GSH and thiocholine at rate constants of 1.2 x 10(2) and 7.2 x 10(2) M-1 s-1, respectively at pH 7.4, 37 degrees C. n-Octylamine stimulated the oxidation of the ring-opened metabolites of ebselen catalyzed by pig and guinea pig liver microsomes but it had essentially no effect on these activities in rat liver microsomes. The selenoxidase activity of microsomes from all three species was partially (30-50%) sensitive to N-benzylimidazole. The effects of n-octylamine and the imidazole suggest that the oxidation of the selenide was catalyzed primarily by enzymes with the properties of flavin-containing and P450-dependent monooxygenases, but the nature of enzymes responsible for a small fraction of the N-benzylimidazole-sensitive activity was not fully resolved. The 2-(methylseleno)benzanilide oxidase activity of pig liver microsomes sensitive to N-benzylimidazole was only partially sensitive to antisera to pig liver NADPH-cytochrome P450 reductase. While neither 2-(methylseleno)benzanilide nor ebselen affected bile flow, the biliary efflux of GSSG was stimulated about fourfold in rat liver perfused with either of these selenium compounds. The increased GSSG efflux produced by 5 microM ebselen or its methyl metabolite was abolished by N-benzylimidazole. PMID:7840620

Akerboom, T P; Sies, H; Ziegler, D M

1995-01-10

93

Thiol Signalling Network with an Eye to Diabetes  

Directory of Open Access Journals (Sweden)

Full Text Available Redox regulatory system controls normal cellular functions. Controlled changes in redox couples potential serve as components for signal transduction, similarly to the phosphorylation cascade. Cellular redox biology requires both compartimentalisation and communication of redox systems: the thermodynamic disequilibrium of the major redox switches allows rapid and sensitive responses to perturbations in redox environments. The many oxidation states of sulphur are found in numerous sulphur species with distinct functional groups (thiols, disulphides, polysulphides, sulphenic, sulphinic and sulphonic acids, etc., which participate in a complicated network of sulphur-based redox events. Human diseases such as diabetes mellitus and its cardiovascular complications have been associated with increased production of reactive oxygen species and perturbations of thiol redox homeostasis. The review surveys literature related to some etiopathogenic aspects and therapeutic perspectives. The dual toxic-protective property of sulphydryl-donor molecules in experimental settings proposes the general problem of designing antioxidants for therapeutic use.

Elena Matteucci

2010-12-01

94

EUV negative-resist based on thiol-yne system  

Science.gov (United States)

Non-conventional chemically amplified (CA) negative resist for EUV lithography was studied. We have designed negative-tone EUV resist based on thiol-yne stepwise radical reactions. OH groups of poly(4-hydroxystyrene) (PHS) were modified with functional units bearing C-C triple bond structure. Resist was formulated as a mixture of modified-PHS, multifunctional thiol compound, and photoradical generator. The present resist was developable with standard 2.38 wt% TMAH aq. solution. Photo-sensitivity of the resist was obtained on irradiation at 254 nm and 13.5 nm. The resist was highly sensitive to EUV exposure. The sensitivity and the contrast were affected by the structure of modified-PHS and process conditions.

Shirai, Masamitsu; Maki, Koich; Okamura, Haruyuki; Kaneyama, Koji; Itani, Toshiro

2011-03-01

95

Odorant polyfunctional thiols issued from bottle beer fermentation  

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Bottle refermentation which imparts beer effervescence and resistance against infection and oxidation is also known to improve flavor profile and stability. By this process, some stale off-flavors exhaled by aldehydes (trans-2-nonenal, 3-methylthiopropionaldehyde, 3- methylbutanal ..) are reduced into alcohols (1, 2). Unfortunately, yeast esterases can also strongly affect the beer fruity character by hydrolyzing isoamyl acetate, ethyl hexanoate and ethyl octanoate (1, 2). Thiols are known to...

Nizet, Sabrina; Gros, Jacques; Collin, Sonia; Xii, Weurman Flavour Research Symposium

2011-01-01

96

Contrasting bonding behavior of thiol molecules on carbon fullerene structures  

International Nuclear Information System (INIS)

We have performed semiempirical as well as ab initio density-functional theory (DFT) calculations at T=0 to analyze the equilibrium configurations and electronic properties of spheroidal C60 as well as of cylindrical armchair (5,5) and (8,8) fullerenes passivated with SCH3 and S(CH2)2CH3 thiols. Our structural results reveal that the lowest-energy configurations of the adsorbates strongly depend on their chain length and on the structure of the underlying substrate. In the low-coverage regime, both SCH3 and S(CH2)2CH3 molecules prefer to organize into a molecular cluster on one side of the C60 surface, providing thus a less protective organic coating for the carbon structure. However, with increasing the number of adsorbed thiols, a transition to a more uniform distribution is obtained, which actually takes place for six and eight adsorbed molecules when using S(CH2)2CH3 and SCH3 chains, respectively. In contrast, for the tubelike arrangements at the low-coverage regime, a quasi-one-dimensional zigzag organization of the adsorbates along the tubes is always preferred. The sulfur-fullerene bond is considerably strong and is at the origin of outward and lateral displacements of the carbon atoms, leading to the stabilization of three-membered rings on the surface (spheroidal structures) as well as to sizable nonuniform radial deformations (cylindrical configurations). The electronic spectrum of our thiol-passivated fullerenes shows strong variations in the energy difference between the highest occupied and lowest unoccupied molecular orbitals as a function of the number and distribution of adsorbed thiols, opening thus the possibility to manipulate the transport properties of these compounds by means of selective adsorption mechanisms

2003-11-01

97

Activities of Bismuth Thiols against Staphylococci and Staphylococcal Biofilms  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Indwelling medical devices are associated with infectious complications. Incorporating antimicrobials into indwelling materials may reduce bacterial colonization. Bismuth thiols are antibiofilm agents with up to 1,000-fold-greater antibacterial activity than other bismuth salts. Staphylococci are particularly sensitive, as determined by agar diffusion and broth dilution susceptibility testing. Bismuth-ethanedithiol inhibited 10 methicillin-resistant Staphylococcus epidermidis strains at 0.9 t...

Domenico, Philip; Baldassarri, Lucilla; Schoch, Paul E.; Kaehler, Kristina; Sasatsu, Masanori; Cunha, Burke A.

2001-01-01

98

A fluorescent probe for rapid detection of thiols and imaging of thiols reducing repair and H2O2 oxidative stress cycles in living cells.  

Science.gov (United States)

A diselenide containing fluorescent probe based on a fluorescein scaffold for thiols was developed. The fluorescent probe exhibited rapid response, high selectivity and reversibility. Confocal fluorescence microscopy was used to visualize the redox changes mediated by thiols and reactive oxygen species in living HeLa cells. PMID:23187935

Lou, Zhangrong; Li, Peng; Sun, Xiaofei; Yang, Songqiu; Wang, Bingshuai; Han, Keli

2013-01-14

99

Identification of the thiol ester lipids in apolipoprotein B  

International Nuclear Information System (INIS)

Human plasma low-density lipoproteins of 1.032-1.043 g/mL density were totally delipidized. The reduced and carboxymethylated apolipoprotein B was incubated with 50 mM [14C] methylamine at pH 8.5 at 30 0C. Covalent incorporation of [14C] methylamine was observed with concomitant generation of new sulfhydryl groups, which could be blocked with [3H]- or [14C]iodoacetic acid. One type of the [14C] methylamine-modified products was separated from the protein and was found to be lipid in nature. Its R/sub f/ on thin-layer chromatography (TLC) was similar to that of the synthetic N-methyl fatty acyl amides. After purification with TLC and transesterification in 3 N methanolic HCl, methyl esters of C16 and C18 fatty acids at 1:1 ratio were identified by gas-liquid chromatography. The transesterification method was verified with the known N-methyl fatty acyl amides. These results suggest the presence of labile thiol ester linked palmitate and stearate in apolipoprotein B. Under mild alkaline conditions, the thiol ester bonds are broken by methylamine and form N-methyl fatty acyl amides and release new -SH groups. Intramolecular thiol ester bonds linked between cysteine side chains and acidic amino acid residues were also found present, which will be reported separately

1988-03-08

100

Occurrence of polyfunctional thiols in fresh lager beers.  

Science.gov (United States)

Polyfunctional thiols are known to have a strong impact on the overall aroma of many fermented foods. Surprisingly, very little data is available on their occurrence in beer. A specific extraction with p-hydroxymercuribenzoic acid was performed on four different fresh light-protected lager beers. gas chromatography-olfactometry, gas chromatography-mass spectrometry, and gas chromatography-pulsed-flame photometer detector analyses of the extracts revealed the presence of more than 10 polyfunctional thiols. All of them were absent from wort, suggesting a key role of the H(2)S excreted by yeasts. 3-Methyl-2-buten-1-thiol, 2-mercapto-3-methylbutanol, 3-mercapto-3-methylbutanol seem to be created from hop allylic alcohols via four different mechanisms: nucleophilic substitution, addition-elimination, and radical anti-Markovnikov or electrophilic Markovnikov additions. 1,4 Addition of hydrogen sulfide to wort alpha,beta-unsaturated aldehydes or ketones may explain the synthesis of 1-mercapto-3-pentanol, 3-mercaptohexanol, and 4-mercapto-4-methyl-2-pentanone through fermentation. Finally, 2-mercaptoethanol, 3-mercaptopropanol, and their corresponding acetates may derive from Ehrlich degradation of sulfur amino acids, while 2-methyl-3-furanthiol should be logically issued from Maillard reactions. PMID:16819917

Vermeulen, C; Lejeune, I; Tran, T T H; Collin, S

2006-07-12

 
 
 
 
101

Organized thiol functional groups in mesoporous core shell colloids  

Energy Technology Data Exchange (ETDEWEB)

The co-condensation in situ of tetraethoxysilane (TEOS) and mercaptopropyltrimethoxysilane (MPTMS) using cetyltrimethylammonium bromide (CTAB) as a template results in the synthesis of multilayered mesoporous structured SiO{sub 2} colloids with 'onion-like' chemical environments. Thiol groups were anchored to an inner selected SiO{sub 2} porous layer in a bilayered core shell particle producing different chemical regions inside the colloidal layered structure. X-Ray Photoelectron Spectroscopy (XPS) shows a preferential anchoring of the -SH groups in the double layer shell system, while porosimetry and simple chemical modifications confirm that pores are accessible. We can envision the synthesis of interesting colloidal objects with defined chemical environments with highly controlled properties. - Graphical abstract: Mesoporous core shell SiO{sub 2} colloids with organized thiol groups. Highlights: Black-Right-Pointing-Pointer Double shell mesoporous silica colloids templated with CTAB. Black-Right-Pointing-Pointer Sequential deposition of mesoporous SiO{sub 2} layers with different chemistries. Black-Right-Pointing-Pointer XPS shows the selective functionalization of mesoporous layers with thiol groups.

Marchena, Martin H. [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina); Granada, Mara [Centro Atomico Bariloche-CNEA, 8400 San Carlos de Bariloche (Argentina); Instituto Balseiro-Centro Atomico Bariloche-CNEA, San Carlos de Bariloche 8400 (Argentina); Bordoni, Andrea V. [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina); Joselevich, Maria [Asociacion Civil Expedicion Ciencia, Cabrera 4948, C1414BGP Buenos Aires (Argentina); Troiani, Horacio [Centro Atomico Bariloche-CNEA, 8400 San Carlos de Bariloche (Argentina); Instituto Balseiro-Centro Atomico Bariloche-CNEA, San Carlos de Bariloche 8400 (Argentina); Williams, Federico J. [DQIAQyF-INQUIMAE FCEN, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon II, C1428EHA Buenos Aires (Argentina); Wolosiuk, Alejandro, E-mail: wolosiuk@cnea.gov.ar [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina)

2012-03-15

102

Fast and Selective Modification of Thiol Proteins/Peptides by N-(Phenylseleno)phthalimide  

Science.gov (United States)

We previously reported that selenamide reagents such as ebselen and N-(phenylseleno)phthalimide (NPSP) can be used to selectively derivatize thiols for mass spectrometric analysis, and the introduced selenium tags are useful as they could survive or removed with collision-induced dissociation (CID). Described herein is the further study of the reactivity of various protein/peptide thiols toward NPSP and its application to derivatize thiol peptides in protein digests. With a modified protocol (i.e., dissolving NPSP in acetonitrile instead of aqueous solvent), we found that quantitative conversion of thiols can be obtained in seconds, using NPSP in a slight excess amount (NPSP:thiol of 1.1-2:1). Further investigation shows that the thiol reactivity toward NPSP reflects its chemical environment and accessibility in proteins/peptides. For instance, adjacent basic amino acid residues increase the thiol reactivity, probably because they could stabilize the thiolate form to facilitate the nucleophilic attack of thiol on NPSP. In the case of creatine phosphokinase, the native protein predominately has one thiol reacted with NPSP while all of four thiol groups of the denatured protein can be derivatized, in accordance with the corresponding protein conformation. In addition, thiol peptides in protein/peptide enzymatic digests can be quickly and effectively tagged by NPSP following tri- n-butylphosphine (TBP) reduction. Notably, all three thiols of the peptide QCCASVCSL in the insulin peptic digest can be modified simultaneously by NPSP. These results suggest a novel and selective method for protecting thiols in the bottom-up approach for protein structure analysis.

Wang, Zhengfang; Zhang, Yun; Zhang, Hao; Harrington, Peter B.; Chen, Hao

2012-03-01

103

Pneumolysin, the thiol-activated toxin of Streptococcus pneumoniae, does not require a thiol group for in vitro activity.  

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The role of the single cysteine residue in the activity of the thiol-activated toxin pneumolysin was investigated using oligonucleotide-mediated, site-directed mutagenesis. Three modified toxins in which the cysteine residue was changed to an alanine, a serine, or a glycine residue were purified to homogeneity and examined for activity. The Cys-428----Ala modified toxin was indistinguishable from the wild-type recombinant toxin in terms of hemolytic activity and lytic and inhibitory effects o...

1989-01-01

104

Interactions of thiol-containing androgens with human placental aromatase.  

Science.gov (United States)

A series of thiol androgens were synthesized and investigated to characterize structural features important for the inhibition of aromatase. Analogues of androstenedione with thiol groups in either the 2 alpha-, 10 beta-, or 19-positions caused time-dependent inhibition of human placental aromatase. When their KI and kcat values were compared with those of 4-hydroxyandrost-4-ene-3,17-dione (4-OHa) and 10 beta-propargylestr-4-ene-3,17-dione (PED), the thiol androgen 10 beta-mercaptoestr-4-ene-3,17-dione (10 beta-SHnorA) proved to be the most potent suicide substrate. However, 19-mercaptoandrost-4-ene-3,17-dione (19-SHA) was the best all-around inhibitor. All compounds except 19-SHA exhibited normal type I P-450 difference spectra with partially purified/solubilized, human placental aromatase. The Ks values for the series of compounds compared qualitatively to the KI values determined from the time and concentration-dependent inhibition experiments. 19-SHA induced split Soret peaks at 380 and 474 nm, which suggested binding of the 19-thiolate directly to the ferric iron of aromatase. This binding could be displaced by aminoglutethimide but not by androstenedione. The inhibitory activity of 19-SHA may be explained by two independent mechanisms: (1) suicide inactivation of aromatase in the ferrous state; and (2) a direct "hyper-type II" binding to the remaining portion of the cytochrome in the ferric state. A free thiol group was necessary for the suicide inhibitory activity of 19-SHA; time-dependent inactivation of aromatase by 19-(acetylthio)androst-4-ene-3,17-dione (19-SAcA) and 19-xanthogenylandrost-4-ene-3,17-dione (19-XanA) could be prevented if the microsomes were preincubated with a carboxyesterase inhibitor. Aromatase previously inactivated by either thiol androgens,4-OHA, or PED could not be reactivated after incubation with the disulfide reducing agent dithiothreitol, which suggests that a disulfide bond may not be involved in aromatase inactivation by these inhibitors. PMID:2909733

Bednarski, P J; Nelson, S D

1989-01-01

105

A fluorescent probe which allows highly specific thiol labeling at low pH  

DEFF Research Database (Denmark)

Determination of the thiol-disulfide status in biological systems is challenging as redox pools are easily perturbed during sample preparation. This is particularly pertinent under neutral to mildly alkaline conditions typically required for alkylation of thiols. Here we describe the synthesis and properties of a thiol-specific reagent, fluorescent cyclic activated disulfide (FCAD), which includes the fluorescein moiety as fluorophore and utilizes a variation of thiol-disulfide exchange chemistry. The leaving-group character of FCAD makes it reactive at pH 3, allowing modification at low pH, limiting thiol-disulfide exchange. Different applications are demonstrated including picomolar thiol detection, determination of redox potentials, and in-gel detection of labeled proteins.

Nielsen, Jonas W.; Jensen, Kristine Steen

2012-01-01

106

In vivo modulation of rat liver 3-hydroxy-3-methylglutaryl-coenzyme A reductase, reductase kinase, and reductase kinase kinase by mevalonolactone.  

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It has been previously demonstrated that the enzymic activity of rat liver 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase; EC 1.1.1.34) is modulated in vitro and in vivo by a bicyclic cascade system involving reversible phosphorylation of HMG-CoA reductase and reductase kinase. In the present study, administration of mevalonolactone to rats caused a rapid inhibition of HMG-CoA reductase activity. The initial short-term (20-min) reversible inhibition (38%) of enzyme activit...

Beg, Z. H.; Stonik, J. A.; Brewer, H. B.

1984-01-01

107

Combined bead polymerization and Cinchona organocatalyst immobilization by thiol–ene addition  

Directory of Open Access Journals (Sweden)

Full Text Available In this work, we report an unusually concise immobilization of Cinchona organocatalysts using thiol–ene chemistry, in which catalyst immobilization and bead polymerization is combined in a single step. A solution of azo initiator, polyfunctional thiol, polyfunctional alkene and an unmodified Cinchona-derived organocatalyst in a solvent is suspended in water and copolymerized on heating by thiol–ene additions. The resultant spherical and gel-type polymer beads have been evaluated as organocatalysts in catalytic asymmetric transformations.

Kim A. Fredriksen

2012-07-01

108

Fabrication and bonding of thiol-ene-based microfluidic devices : Technical Note  

DEFF Research Database (Denmark)

In this work, the bonding strength of microchips fabricated by thiol-ene free-radical polymerization was characterized in detail by varying the monomeric thiol/allyl composition from the stoichiometric ratio (1:1) up to 100% excess of thiol (2:1) or allyl (1:2) functional groups. Four different thiol-ene to thiol-ene bonding combinations were tested by bonding: (i) two stoichiometric layers, (ii) two layers bearing complementary excess of thiols and allyls, (iii) two layers both bearing excess of thiols, or (iv) two layers both bearing excess of allyls. The results showed that the stiffness of the cross-linked polymer plays the most crucial role regarding the bonding strength. The most rigid polymer layers were obtained by using the stoichiometric composition or an excess of allyls, and thus, the bonding combinations (i) and (iv) withstood the highest pressures (up to the cut-off value of 6 bar). On the other hand, excess of thiol monomers yielded more elastic polymer layers and thus decreased the pressure tolerance for bonding combinations (ii) and (iii). By using monomers with more thiol groups (e.g. tetrathiol versus trithiol), a higher cross-linking ratio, and thus, greater stiffness was obtained. Surface characterization by infrared spectroscopy confirmed that the changes in the monomeric thiol/allyl composition were also reflected in the surface chemistry. The flexibility of being able to bond different types of thiol-enes together allows for tuning of the surface chemistry to yield the desired properties for each application. Here, a capillary electrophoresis separation is performed to demonstrate the attractive properties of stoichiometric thiol-ene microchips.

Sikanen, Tiina M; Lafleur, Josiane P.

2013-01-01

109

Fast and Selective Modification of Thiol Proteins/Peptides by N-(Phenylseleno) phthalimide  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We previously reported that selenamide reagents such as ebselen and N-(phenylseleno) phthalimide (NPSP) can be used to selectively derivatize thiols for mass spectrometric analysis, and the introduced selenium tags are useful as they could survive or removed with collision-induced dissociation (CID). Described herein is the further study of the reactivity of various protein/peptide thiols toward NPSP and its application to derivatize thiol peptides in protein digests. With a modified protocol...

Wang, Zhengfang; Zhang, Yun; Zhang, Hao; Harrington, Peter B.; Chen, Hao

2012-01-01

110

Neutron-gamma irradiation and protein thiols: development of a protein thiol evaluation micro-method and application to irradiated baboons; Irradiation neutron-gamma et groupements thiols proteiques: developpement d`une micromethode d`evaluation des thiols proteiques et application au babouin irradie  

Energy Technology Data Exchange (ETDEWEB)

The essential non-protein sulfhydryl compound implicated in cellular radioprotection is glutathione. Protein thiols seem to be also involved in this protection and might be scavengers for free radical injury. We developed an analytical procedure for protein thiols measurement and we applied this method in neutron-gamma irradiated baboons. Our results demonstrated the reliability and sensitivity of the procedure. They also a drastic decrease of in vivo protein thiols after irradiation. (author). 5 refs.

Chancerelle, Y.; Lafond, J.L.; Della-Maura, L.; Faure, P.; Mathieu, J.; Costa, P.; Mestries, J.C.; Kergonou, J.F.

1994-12-31

111

Thiol?ene Coupling of Renewable Monomers : at the forefront of bio-based polymeric materials  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Plant derived oils bear intrinsic double-bond functionality that can be utilized directly for the thiol–ene reaction. Although terminal unsaturations are far more reactive than internal ones, studies on the reversible addition of thiyl radicals to 1,2-disubstituted alkenes show that this is an important reaction. To investigate the thiol–ene coupling reaction involving these enes, stoichiometric mixtures of a trifunctional propionate thiol with monounsaturated fatty acid methyl esters (me...

Claudino, Mauro

2011-01-01

112

Structural prototypes for an extended family of flavoprotein reductases: comparison of phthalate dioxygenase reductase with ferredoxin reductase and ferredoxin.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The structure of phthalate dioxygenase reductase (PDR), a monomeric iron-sulfur flavoprotein that delivers electrons from NADH to phthalate dioxygenase, is compared to ferredoxin-NADP+ reductase (FNR) and ferredoxin, the proteins that reduce NADP+ in the final reaction of photosystem I. The folding patterns of the domains that bind flavin, NAD(P), and [2Fe-2S] are very similar in the two systems. Alignment of the X-ray structures of PDR and FNR substantiates the assignment of features that ch...

Correll, C. C.; Ludwig, M. L.; Bruns, C. M.; Karplus, P. A.

1993-01-01

113

Impact of thiol and amine functionalization on photoluminescence properties of ZnO films  

International Nuclear Information System (INIS)

In the present study, we have investigated surface functionalization of ZnO films with dodecanethiol (Thiol) and trioctylamine (amine) by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle (CA) and photoluminescence (PL) measurements. The chemical bondings of thiol and amine with ZnO have been confirmed via the formation of Zn–S and Zn–N bonds by XPS measurements. AFM measurements on ZnO films before and after surface functionalization with thiol and amine provide evidence for the successful functionalization of thiol and amine on ZnO surfaces without any island formation. The CA measurements on ZnO films before and after surface functionalization with thiol and amine show the hydrophobic nature. PL measurements of thiol and amine functionalized ZnO show enhancements of UV emission and quenching of visible emission. The enhanced UV emissions in thiol and amine functionalized ZnO films suggest that the surface defects such as oxygen vacancies are passivated by thiol and amine functionalization. -- Highlights: ? Surface functionalization is a new approach to reduce surface dependent non-radiative process. ? Oxygen vacancies are passivated on surface functionalization. ? Thiol and amine functionalized ZnO show enhancements of UV emission

2013-08-01

114

Thiol-chromene click chemistry: a coumarin-based derivative and its use as regenerable thiol probe and in bioimaging applications.  

Science.gov (United States)

The synthesis and characterization of a coumarin-chromene (8, 9-dihydro-2H-cyclopenta[b]pyrano[2,3-f]chromene-2,10(7aH)-dione) (1) derivative and its use for thiol chemosensing in water was reported. Experimental details showed 1 acts as a probe for the detection of thiols including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), whereas amino acids which do not contain thiols induced no changes in UV-vis spectra and fluorescence emission properties of 1. A possible detection mechanism is a nucleophilic attack of thiols to the ?,?-unsaturated ketone in 1 that resulted in a fluorescent coumarin derivative. Further studies showed that 1-thiol derivatives can be applied to the design of regenerative chemodosimeters for Cu(2+), Hg(2+) and Cd(2+) in water based on M(n+)-promoted desulfurization and recovery of 1. Furthermore, the optical properties of the probe and its Cys-addition product were theoretically studied. The ability of probe 1 to detect thiols in living cells (HepG2 cells) via an enhancement of the fluorescence was proved. Moreover, the applicability of 1 for the direct determination of biorelevant thiols in a complex matrix such as human plasma was also demonstrated. PMID:23587792

Yang, Yutao; Huo, Fangjun; Yin, Caixia; Zheng, Anmin; Chao, Jianbin; Li, Yingqi; Nie, Zongxiu; Martínez-Máñez, Ramón; Liu, Diansheng

2013-09-15

115

Respiratory arsenate reductase as a bidirectional enzyme  

International Nuclear Information System (INIS)

The haloalkaliphilic bacterium Alkalilimnicola ehrlichii is capable of anaerobic chemolithoautotrophic growth by coupling the oxidation of arsenite (As(III)) to the reduction of nitrate and carbon dioxide. Analysis of its complete genome indicates that it lacks a conventional arsenite oxidase (Aox), but instead possesses two operons that each encode a putative respiratory arsenate reductase (Arr). Here we show that one homolog is expressed under chemolithoautotrophic conditions and exhibits both arsenite oxidase and arsenate reductase activity. We also demonstrate that Arr from two arsenate respiring bacteria, Alkaliphilus oremlandii and Shewanella sp. strain ANA-3, is also biochemically reversible. Thus Arr can function as a reductase or oxidase. Its physiological role in a specific organism, however, may depend on the electron potentials of the molybdenum center and [Fe-S] clusters, additional subunits, or constitution of the electron transfer chain. This versatility further underscores the ubiquity and antiquity of microbial arsenic metabolism.

2009-05-01

116

Respiratory arsenate reductase as a bidirectional enzyme  

Science.gov (United States)

The haloalkaliphilic bacterium Alkalilimnicola ehrlichii is capable of anaerobic chemolithoautotrophic growth by coupling the oxidation of arsenite (As(III)) to the reduction of nitrate and carbon dioxide. Analysis of its complete genome indicates that it lacks a conventional arsenite oxidase (Aox), but instead possesses two operons that each encode a putative respiratory arsenate reductase (Arr). Here we show that one homolog is expressed under chemolithoautotrophic conditions and exhibits both arsenite oxidase and arsenate reductase activity. We also demonstrate that Arr from two arsenate respiring bacteria, Alkaliphilus oremlandii and Shewanella sp. strain ANA-3, is also biochemically reversible. Thus Arr can function as a reductase or oxidase. Its physiological role in a specific organism, however, may depend on the electron potentials of the molybdenum center and [Fe–S] clusters, additional subunits, or constitution of the electron transfer chain. This versatility further underscores the ubiquity and antiquity of microbial arsenic metabolism.

Richey, C.; Chovanec, P.; Hoeft, S. E.; Oremland, R. S.; Basu, P.; Stolz, J. F.

2009-01-01

117

Oligomerization of Indole Derivatives with Incorporation of Thiols  

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Abstract: Two molecules of indole derivative, e.g. indole-5-carboxylic acid, reacted with one molecule of thiol, e.g. 1,2-ethanedithiol, in the presence of trifluoroacetic acid to yield adducts such as 3-[2-(2-amino-5-carboxyphenyl)-1-(2-mercaptoethylthio)ethyl]-1Hindole-5-carboxylic acid. Parallel formation of dimers, such as 2,3-dihydro-1H,1'H-2,3'-biindole-5,5'-dicarboxylic acid and trimers, such as 3,3'-[2-(2-amino-5-carboxyphenyl) ethane-1,1-diyl]bis(1H-indole-5-carboxylic acid) of the i...

Felikss Mutulis; Adolf Gogoll; Ilze Mutule; Sviatlana Yahorava; Aleh Yahorau; Edvards Liepinsh; Wikberg, Jarl E. S.

2008-01-01

118

Suspended hybrid films assembled from thiol-capped gold nanoparticles  

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In this work, we explored the formation processes of suspended hybrid thin films of thiol-capped Au nanoparticles (AuNPs) inside metal oxide tubular structures. We found that a balance between in-film interactions of the AuNPs and boundary interactions with metal oxides is a key in making these special organic–inorganic thin films. The hybrid films process many processing advantages and flexibilities, such as controllable film thickness, interfacial shape and inter-AuNPs distance, tuning of...

2012-01-01

119

Tip-enhanced Raman spectroscopic imaging of patterned thiol monolayers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Full spectroscopic imaging by means of tip-enhanced Raman spectroscopy (TERS) was used to measure the distribution of two isomeric thiols (2-mercaptopyridine (2-PySH) and 4-mercaptopyridine (4-PySH)) in a self-assembled monolayer (SAM) on a gold surface. From a patterned sample created by microcontact printing, an image with full spectral information in every pixel was acquired. The spectroscopic data is in good agreement with the expected molecular distribution on the sample surface due to t...

2011-01-01

120

Structural prototypes for an extended family of flavoprotein reductases: comparison of phthalate dioxygenase reductase with ferredoxin reductase and ferredoxin.  

Science.gov (United States)

The structure of phthalate dioxygenase reductase (PDR), a monomeric iron-sulfur flavoprotein that delivers electrons from NADH to phthalate dioxygenase, is compared to ferredoxin-NADP+ reductase (FNR) and ferredoxin, the proteins that reduce NADP+ in the final reaction of photosystem I. The folding patterns of the domains that bind flavin, NAD(P), and [2Fe-2S] are very similar in the two systems. Alignment of the X-ray structures of PDR and FNR substantiates the assignment of features that characterize a family of flavoprotein reductases whose members include cytochrome P-450 reductase, sulfite and nitrate reductases, and nitric oxide synthase. Hallmarks of this subfamily of flavoproteins, here termed the FNR family, are an antiparallel beta-barrel that binds the flavin prosthetic group, and a characteristic variant of the classic pyridine nucleotide-binding fold. Despite the similarities between FNR and PDR, attempts to model the structure of a dissociable FNR:ferredoxin complex by analogy with PDR reveal features that are at odds with chemical crosslinking studies (Zanetti, G., Morelli, D., Ronchi, S., Negri, A., Aliverti, A., & Curti, B., 1988, Biochemistry 27, 3753-3759). Differences in the binding sites for flavin and pyridine nucleotides determine the nucleotide specificities of FNR and PDR. The specificity of FNR for NADP+ arises primarily from substitutions in FNR that favor interactions with the 2' phosphate of NADP+. Variations in the conformation and sequences of the loop adjoining the flavin phosphate affect the selectivity for FAD versus FMN. The midpoint potentials for reduction of the flavin and [2Fe-2S] groups in PDR are higher than their counterparts in FNR and spinach ferredoxin, by about 120 mV and 260 mV, respectively. Comparisons of the structure of PDR with spinach FNR and with ferredoxin from Anabaena 7120, along with calculations of electrostatic potentials, suggest that local interactions, including hydrogen bonds, are the dominant contributors to these differences in potential.

Correll, C. C.; Ludwig, M. L.; Bruns, C. M.; Karplus, P. A.

1993-01-01

 
 
 
 
121

A new nomenclature for the aldo-keto reductase superfamily.  

Science.gov (United States)

The aldo-keto reductases (AKRs) represent a growing oxidoreductase superfamily. Forty proteins have been identified and characterized as AKRs, and an additional fourteen genes may encode proteins related to the superfamily. Found in eukaryotes and prokaryotes, the AKRs metabolize a wide range of substrates, including aliphatic aldehydes, monosaccharides, steroids, prostaglandins, and xenobiotics. This broad substrate specificity has caused problems in naming these proteins. Enzymes capable of these reactions have been referred to as aldehyde reductase (ALR1), aldose reductase (ALR2), and carbonyl reductase (ALR3); however, ALR3 is not a member of the AKR superfamily. Also, some AKRs have multiple names based upon substrate specificity. For example, human 3alpha-hydroxysteroid dehydrogenase (3apha-HSD) type I is also known as dihydrodiol dehydrogenase 4 and chlordecone reductase. To address these issues, we propose a new nomenclature system for the AKR superfamily based on amino acid sequence identities. Cluster analysis of the AKRs shows seven distinct families at the 40% amino acid identity level. The largest family (AKR1) contains the aldose reductases, aldehyde reductases, and HSDs. Other families include the prokaryotic AKRs, the plant chalcone reductases, the Shaker channels, and the ethoxyquin-inducible aflatoxin B1 aldehyde reductase. At the level of 60% amino acid identity, subfamilies are discernible. For example, the AKR1 family includes five subfamilies: (A) aldehyde reductases (mammalian); (B) aldose reductases; (C) HSDs; (D) delta4-3-ketosteroid-5beta-reductases; and (E) aldehyde reductases (plant). This cluster analysis forms the basis for our nomenclature system. Recommendations for naming an aldo-keto reductase include the root symbol "AKR," an Arabic number designating the family, a letter indicating the subfamily when multiple subfamilies exist, and an Arabic numeral representing the unique protein sequence. For example, human aldehyde reductase would be assigned as AKR1A1. Our nomenclature is both systematic and expandable, thereby allowing assignment of consistent designations for newly identified members of the superfamily. PMID:9310340

Jez, J M; Flynn, T G; Penning, T M

1997-09-15

122

Indicator approach to develop a chemosensor for the colorimetric sensing of thiol-containing water and its application for the thiol detection in plasma.  

Science.gov (United States)

A strategy for the determination of the presence of thiol-containing amino acids was successfully established by simply assembling copper chloride and xylenol orange (3,3'-bis[N,N-bis(carboxymethyl)aminomethyl]-o-cresolsulfonephthalein trisodium salt; XO) in a 1 : 1 molar ratio in quasi-physiological water solution (pH 6.0). The copper(II)-XO ensemble was highly selective for thiol species such as cysteine, homocysteine, and glutathione without interference from other amino acids and could quantitatively detect thiol in the range from 10 to 200 ?M with a linear relationship having an average molar absorbance constant of 6530 L mol(-1) cm(-1) in pure water. The whole recognition process for thiol gave rise to a rapid visual color change from purple-red to yellow which can be observed simultaneously with the naked-eye. PMID:21373697

Huo, Fang-Jun; Yang, Yu-Tao; Su, Jing; Sun, Yuan-Qiang; Yin, Cai-Xia; Yan, Xu-Xiu

2011-05-01

123

Antioxidant generation and regeneration in lipid bilayers: the amazing case of lipophilic thiosulfinates and hydrophilic thiols.  

Science.gov (United States)

We demonstrate that the garlic-derived chemopreventive agent allicin and the related anamu-derived petivericin are poor radical-trapping antioxidants in lipid bilayers, but that the in situ reaction of a lipophilic analog and a hydrophilic thiol yields an extremely potent radical-trapping antioxidant that can be recycled in the presence of excess thiol. PMID:23938951

Zheng, Feng; Pratt, Derek A

2013-09-25

124

Surfactant-free coating of thiols on gold nanoparticles using sonochemistry: a study of competing processes.  

Science.gov (United States)

A method for the surfactant-free coating of gold nanoparticles with thiols using sonochemistry is presented. The gold nanoparticles were prepared by a modified Zsigmondy method, affording good control over the particle-size distribution, and the thiol coating was performed by the sonication of a biphasic system consisting of a nanoparticle suspension in water and thiols in toluene. The effects of two important reaction parameters on the particle morphology, viz. sonication time and thiol concentration, were investigated in detail using transmission electron microscopy. The effect of the thiol chain length was also studied. We show that the morphology of the coated particles is determined through a competition between two opposing effects: particle fusion, due to the sonication conditions, and digestive ripening, due to the action of the thiols. Additionally, we illustrate the utility of our technique for various applications, including surface-enhanced Raman scattering from bound molecules, and further functionalization using a thiol-exchange reaction. Our technique paves the way for an efficient synthesis of thiol-coated AuNPs of different shapes and sizes, suitable for a range of diverse applications. PMID:24704067

Pallipurath, Anuradha; Nicoletti, Olivia; Skelton, Jonathan M; Mahajan, Sumeet; Midgley, Paul A; Elliott, Stephen R

2014-09-01

125

The first peripherally masked thiol dendrimers: a facile and highly efficient functionalization strategy of polyester dendrimers via one-pot xanthate deprotection/thiol-acrylate Michael addition reactions.  

Science.gov (United States)

Introducing multiple reactive functional groups at the periphery of dendrimer materials presents considerable challenges if the functionality is able to self-react. An efficient and facile approach to introducing masked thiols at the surface of polyester dendrimers is presented. One-pot, deprotection/thiol-acrylate Michael addition from the xanthate-functional dendritic substrates (generation zero to two) has been achieved for the first time, with high efficiency demonstrated using three acrylates of varying chemistry and avoiding disulfide formation. PMID:24595823

Auty, Sam E R; Andrén, Oliver; Malkoch, Michael; Rannard, Steven P

2014-05-27

126

Ebsulfur is a benzisothiazolone cytocidal inhibitor targeting the trypanothione reductase of Trypanosoma brucei.  

Science.gov (United States)

Trypanosoma brucei is the causing agent of African trypanosomiasis. These parasites possess a unique thiol redox system required for DNA synthesis and defense against oxidative stress. It includes trypanothione and trypanothione reductase (TryR) instead of the thioredoxin and glutaredoxin systems of mammalian hosts. Here, we show that the benzisothiazolone compound ebsulfur (EbS), a sulfur analogue of ebselen, is a potent inhibitor of T. brucei growth with a favorable selectivity index over mammalian cells. EbS inhibited the TryR activity and decreased non-protein thiol levels in cultured parasites. The inhibition of TryR by EbS was irreversible and NADPH-dependent. EbS formed a complex with TryR and caused oxidation and inactivation of the enzyme. EbS was more toxic for T. brucei than for Trypanosoma cruzi, probably due to lower levels of TryR and trypanothione in T. brucei. Furthermore, inhibition of TryR produced high intracellular reactive oxygen species. Hydrogen peroxide, known to be constitutively high in T. brucei, enhanced the EbS inhibition of TryR. The elevation of reactive oxygen species production in parasites caused by EbS induced a programmed cell death. Soluble EbS analogues were synthesized and cured T. brucei brucei infection in mice when used together with nifurtimox. Altogether, EbS and EbS analogues disrupt the trypanothione system, hampering the defense against oxidative stress. Thus, EbS is a promising lead for development of drugs against African trypanosomiasis. PMID:23900839

Lu, Jun; Vodnala, Suman K; Gustavsson, Anna-Lena; Gustafsson, Tomas N; Sjöberg, Birger; Johansson, Henrik A; Kumar, Sangit; Tjernberg, Agneta; Engman, Lars; Rottenberg, Martin E; Holmgren, Arne

2013-09-20

127

Role of thiol-containing polyethylene glycol (thiol-PEG) in the modification process of gold nanoparticles (AuNPs): stabilizer or coagulant?  

Science.gov (United States)

Gold nanoparticles (AuNPs) have significant potential as biosensors and drug delivery vehicles, as well as imaging and thermotherapy agents. Thiol-containing polyethylene glycol (PEG), hereafter denoted as thiol-PEG, is widely used as a macromolecular ligand for modifying AuNPs and stabilizing them under various environments. In this work, a series of thiol-PEG-modified AuNPs (PEGylated AuNPs) with different PEG molecular weights (Mw) were synthesized. The saturated capping density, charge-screening ability, and stability of the PEGylated AuNPs were then examined. The results showed that high-Mw PEG stabilized the AuNPs and screened the surface charge better than low-Mw PEG, but the latter showed higher saturated capping density. More importantly, PEG exhibited the maximum coagulation concentration (MCC) and critical stabilization concentration (CSC) in the stabilizing process of the AuNPs. Thiol-PEG acted as an AuNP stabilizer only when its concentration was higher than the CSC. Otherwise, thiol-PEG accelerated AuNPs aggregation, which reached the peak level at the MCC. These results were significant in recognizing the influence of thiol-PEG on the stability of AuNPs. PMID:23711661

Wang, Wei; Wei, Qin-Qin; Wang, Jun; Wang, Bi-Cui; Zhang, Sai-Hui; Yuan, Zhi

2013-08-15

128

Spiropyran as a reusable chemosensor for selective colorimetric detection of aromatic thiols.  

Science.gov (United States)

Design of optical molecular probes for selective detection of aromatic thiols has attracted much attention. Although several types of probes have been proposed, all of them exhibit colorimetric or fluorometric response via irreversible reaction with aromatic thiols and cannot be reused. Here we report that a spiropyran dye is the first example of a reusable chemosensor for aromatic thiols. A colorless spiropyran dye () dissolved in aqueous media containing aromatic thiols is selectively isomerized to the colored merocyanine form in the dark. In contrast, visible light irradiation of the merocyanine form promotes successful reversion to the colorless spirocyclic form. Kinetic absorption analysis and ab initio calculations of the transition states revealed that this colorimetric response in the dark is ascribed to the decrease in activation energy for isomerization via the nucleophilic interaction between the aromatic thiol and the olefinic carbon of the dye. PMID:24616910

Shiraishi, Yasuhiro; Yamamoto, Kohei; Sumiya, Shigehiro; Hirai, Takayuki

2014-05-28

129

NrdH-redoxin of Mycobacterium tuberculosis and Corynebacterium glutamicum Dimerizes at High Protein Concentration and Exclusively Receives Electrons from Thioredoxin Reductase*  

Science.gov (United States)

NrdH-redoxins are small reductases with a high amino acid sequence similarity with glutaredoxins and mycoredoxins but with a thioredoxin-like activity. They function as the electron donor for class Ib ribonucleotide reductases, which convert ribonucleotides into deoxyribonucleotides. We solved the x-ray structure of oxidized NrdH-redoxin from Corynebacterium glutamicum (Cg) at 1.5 ? resolution. Based on this monomeric structure, we built a homology model of NrdH-redoxin from Mycobacterium tuberculosis (Mt). Both NrdH-redoxins have a typical thioredoxin fold with the active site CXXC motif located at the N terminus of the first ?-helix. With size exclusion chromatography and small angle x-ray scattering, we show that Mt_NrdH-redoxin is a monomer in solution that has the tendency to form a non-swapped dimer at high protein concentration. Further, Cg_NrdH-redoxin and Mt_NrdH-redoxin catalytically reduce a disulfide with a specificity constant 1.9 × 106 and 5.6 × 106 m?1 min?1, respectively. They use a thiol-disulfide exchange mechanism with an N-terminal cysteine pKa lower than 6.5 for nucleophilic attack, whereas the pKa of the C-terminal cysteine is ?10. They exclusively receive electrons from thioredoxin reductase (TrxR) and not from mycothiol, the low molecular weight thiol of actinomycetes. This specificity is shown in the structural model of the complex between NrdH-redoxin and TrxR, where the two surface-exposed phenylalanines of TrxR perfectly fit into the conserved hydrophobic pocket of the NrdH-redoxin. Moreover, nrdh gene deletion and disruption experiments seem to indicate that NrdH-redoxin is essential in C. glutamicum.

Van Laer, Koen; Dziewulska, Aleksandra M.; Fislage, Marcus; Wahni, Khadija; Hbeddou, Abderahim; Collet, Jean-Francois; Versees, Wim; Mateos, Luis M.; Tamu Dufe, Veronica; Messens, Joris

2013-01-01

130

Selenium as an Electron Acceptor During the Catalytic Mechanism of Thioredoxin Reductase  

Science.gov (United States)

Mammalian thioredoxin reductase (TR) is a pyridine nucleotide disulfide oxidoreductase that uses the rare amino acid selenocysteine (Sec) in place of the more commonly used amino acid cysteine (Cys) in the redoxactive tetrapeptide Gly-Cys-Sec-Gly motif to catalyze thiol/disulfide exchange reactions. Sec can accelerate the rate of these exchange reactions by being: (i) a better nucleophile than Cys, (ii) a better electrophile than Cys, (iii) a better leaving group than Cys, or (iv) by using a combination of all three of these factors, being more chemically reactive than Cys. The role of the selenolate as a nucleophile in the reaction mechanism was recently demonstrated by creating a mutant of human thioredoxin reductase-1 in which the Cys497-Sec498 dyad of the C-terminal redox center was mutated to either a Ser497-Cys498 dyad or a Cys497-Ser498 dyad. Both mutant enzymes were incubated with human thioredoxin (Trx) in order to determine which mutant formed a mixed disulfide bond complex. Only the mutant containing the Ser497-Cys498 dyad formed a complex and this structure has been solved by X-ray crystallography [Fritz-Wolf, K., Kehr, S., Stumpf, M., Rahlfs, S., and Becker, K. (2011) Crystal structure of the human thioredoxin reductase-thioredoxin complex, Nat Commun 2, 383.] This experimental observation most likely means that the selenolate is the initial attacking nucleophile onto the disulfide bond of Trx because a complex only resulted when Cys was present in the second position of the dyad. As a nucleophile, the selenolate of Sec helps to accelerate the rate of this exchange reaction relative to Cys in the Sec ? Cys mutant enzyme. Another thiol/disulfide exchange reaction that occurs in the enzymatic cycle of the enzyme is the transfer of electrons from the thiolate of the interchange Cys residue of the N-terminal redox center to the 8-membered selenosulfide ring of the C-terminal redox center. The selenium atom of the selenosulfide could accelerate this exchange reaction by being a good leaving group (attack at the sulfur atom), or by being a good electrophile (attack at the selenium atom). Here we provide strong evidence that the selenium atom is attacked in this exchange step. This was shown by creating a mutant enzyme containing a Gly-Gly-Seccoo- motif that had 0.5% of the activity of the wild type enzyme. This mutant lacks the adjacent, resolving Cys residue, which acts by attacking the mixed selenosulfide bond that occurs between enzyme and substrate. A similar result was obtained when Sec was replaced with homocysteine. These results highlight the role of selenium as an electron acceptor in the catalytic mechanism of thioredoxin reductase as well as its established role as an electron donor to the substrate.

Lothrop, Adam P.; Snider, Gregg W.; Ruggles, Erik L.; Patel, Amar S.; Lees, Watson J.; Hondal, Robert J.

2014-01-01

131

Voltammetric, spectroelectrochemical, and electrocatalytic properties of thiol-derivatized phthalocyanines  

International Nuclear Information System (INIS)

Voltammetric and spectroelectrochemical properties and electrocatalytic activities of thiol-derivatized phthalocyanine complexes for hydrogen production have been investigated. Voltammetric and spectroelectrochemical measurements show that while cobalt phthalocyanine complexes (CoPc) present well defined metal-based and ring-based redox processes, all other complexes give only ring-based reduction and oxidation processes. The redox processes are generally diffusion-controlled, reversible and one-electron transferred processes. The complexes bearing tetra(acetoxyethylthio) substituents represents aggregation tendency in DCM solution. Cobalt and nickel phthalocyanines are easily electrodeposited on the GCE working electrode during the repeating cycles of positive potentials. Electrocatalytic activities of electrodeposited complexes indicated that CoPc catalyzed the proton reduction via the electro-reduced [CoIPc2-]1- and/or [CoIPc3-]2- species depending on the pH of the aqueous solution

2008-06-01

132

Reactivity assessment of chalcones by a kinetic thiol assay.  

Science.gov (United States)

The electrophilic nature of chalcones (1,3-diphenylprop-2-en-1-ones) and many other ?,?-unsaturated carbonyl compounds is crucial for their biological activity, which is often based on thiol-mediated regulation processes. To better predict their biological activity a simple screening assay for the assessment of the second-order rate constants (k(2)) in thia-Michael additions was developed. Hence, a clear structure-activity relationship of 16 differentially decorated hydroxy-alkoxychalcones upon addition of cysteamine could be established. Moreover, amongst other naturally occurring ?,?-unsaturated carbonyl compounds k(2) values for curcumin and cinnamaldehyde were gained while cinnamic acids or esters gave no or very slow reactions. PMID:23224077

Amslinger, Sabine; Al-Rifai, Nafisah; Winter, Katrin; Wörmann, Kilian; Scholz, Rebekka; Baumeister, Paul; Wild, Martin

2013-01-28

133

Organic thiols as pyrite depressants in oil agglomeration of coal  

Energy Technology Data Exchange (ETDEWEB)

Describes a study in which a group of bifunctional organosulphur compounds were tested as pyrite depressants in the selective oil agglomeration of coal. Pyrite sulphurised by treatment with a freshly acidified solution of sodium sulphide to increase its response to oil agglomeration was used in preliminary screening tests of potential depressants. For most of the tests, high-grade mineral pyrite was used, but in some cases pyrite extracted from coal was used instead. The following organic thiols, each of which containing a sulphydryl group (-SH) and a hydrophilic group, were found to suppress the agglomeration of sulphurised pyrite when heptane was used as an agglomerant: thioglyolic acid, thiolactic acid, mercaptosuccinic acid, 3-mercaptopropionic acid, and 2-mercaptoethanesulfonic acid. In other tests involving agglomeration with heptane, these materials also improved the separation of artificial mixtures of Illinois, No. 6 coal and sulphurised pyrite. The use of thioglycolic acid gave the best separation. 14 refs., 6 figs., 1 tab.

Drzymala, J.; Wheelock, T.D. (Iowa State University, Ames, IA (United States). Ames Lab. and Dept. of Chemical Engineering)

1993-01-01

134

Controlled formation of gold nanoparticle dimers using multivalent thiol ligands.  

Science.gov (United States)

Approaches for the controlled formation of gold nanoparticle dimers are investigated. These are based on a locally confined surface modification of gold nanoparticles followed by bridging two particles with an organic linker. A key factor in these approaches is the use of multivalent ligands. Citrate-stabilized gold nanoparticles are immobilized on a glass surface and mono- and multivalent thiol ligands are investigated regarding their ability to inactivate the nanoparticles sites facing away from the glass. A successful locally confined functionalization is only possible if multivalent ligands are used in this step. The application of monovalent ligands results in less stable particles without a permanent regioselective functionalization. This result can be explained by the dynamic equilibrium between bound and free ligands. Subsequently, the sites of the nanoparticles previously bound to the glass surface are functionalized with thiol ligands additionally bearing a reactive group. Approaches using dithiol linkers, diamine linkers, and coupling complementary functionalized particles are investigated. The highest yield of stable dimers is obtained from conditions where nanoparticles which are regioselectively functionalized with an N-hydroxysuccinimide ester are reacted with complementary amino-functionalized particles. The application of nanoparticles with activated carboxyl groups is essential since standard carboxyl activation agents induce an aggregation of the nanoparticles due to a reaction with remaining citrate molecules on the nanoparticle surface which reduces significantly electrostatic stabilization. This versatile approach using complementary regioselective with multivalent ligands functionalized nanoparticles may be also used for the coupling of particles with different size, shape, or composition, as well as a control of the interparticle distance. PMID:22029627

Hofmann, Andreas; Schmiel, Peter; Stein, Benjamin; Graf, Christina

2011-12-20

135

Studies of Aqueous U(IV) Complexation under Thiol-rich Conditions  

Energy Technology Data Exchange (ETDEWEB)

Organic thiol compounds and hydrogen sulfide (H{sub 2}S) are electron donors and metabolic products of sulfate reducing bacteria. In addition, they are among redox potential (Eh) determinants of groundwater systems due to their redox characteristics. The low values of acid dissociation constants for .SH (pK{sub a}, 7-9) compared to those of aliphatic or phenolic .OH, impart greater anionic and metal-binding properties to the molecules. Recently, we demonstrated that a thiol compound (i. e., thiosalicylate) enhances the solubility of U(VI) at higher pH levels (< ?9). In this study, to have a better knowledge of the behaviors of U(IV) species under anaerobic conditions, the U(IV)-OH complex formation in the presence of thiol was examined using UV-Vis spectrophotometry and TRLFS (time-resolved laser-induced fluorescence spectroscopy). A TRLFS-based U(IV) quantification methodology developed earlier was applied to examine the effects of thiol species on the dissolution behaviors. Based on UV-Vis absorption monitoring, the presence of thiol does not result in a significant changes in the low-pH hydrolysis behaviors of U(IV). However, the concentration of U(IV) dissolved in bulk phase of aqueous solutions increased with the increase of thiol concentration. The formation of soluble thiol complexes or the stabilization of UO{sub 2} nanoparticles may explain the observed solubility increase.

Cha, Wansik; Cho, Hyeryun; Jung, Euo Chang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2013-05-15

136

Species variations in biliary excretion of glutathione-related thiols and methylmercury.  

Science.gov (United States)

The biliary excretion of methylmercury is thought to be related to the biliary excretion of nonprotein thiols in rats. Species differences in biliary excretion of glutathione (GSH) and related thiols are unknown; therefore, the relationship between the biliary excretion of GSH-related thiols and methylmercury in five species was studied. The biliary excretion rate of GSH-related thiols and disulfides was 369, 192, 94, 50, and 19 nmol/min/kg for mice, rats, hamsters, guinea pigs, and rabbits, respectively. The main thiol in mouse, hamster, and rat bile was GSH, whereas guinea pig and rabbit bile contained mainly cysteinylglycine (Cys-Gly). The larger percentage of Cys-Gly in guinea pig and rabbit bile was correlated with their greater hepatic gamma-glutamyltranspeptidase (GGT) activity than that observed in the other species. The biliary excretion rate (nmol/min/kg) of methylmercury was approximately 0.8 in mice, rats, and hamsters compared to significantly lower rates in guinea pigs and rabbits (0.15 and 0.03, respectively). It is concluded that the species-specific composition of GSH-related thiols and disulfides in bile is related to species variations in hepatic GGT activity, and that the species variation in biliary excretion of GSH-related thiols does not entirely account for the species variation in methylmercury excretion, indicating other factors are also apparently involved in determining the rate of biliary excretion of methylmercury. PMID:2897139

Stein, A F; Gregus, Z; Klaassen, C D

1988-05-01

137

Oxidation of dissolved elemental mercury by thiol compounds under anoxic conditions  

Energy Technology Data Exchange (ETDEWEB)

Mercuric mercury, Hg(II), forms strong complexes with thiol compounds that commonly dominate Hg(II) speciation in natural freshwater. However, reactions between dissolved elemental Hg(0) and thiols are not well understood although these processes are likely to be important in determining Hg speciation and geochemical cycling in the environment. In this study, reaction rates and mechanisms between dissolved Hg(0) and a number of selected organic ligands with varying molecular structures and sulfur (S) oxidation states were determined to assess the role of these ligands in Hg(0) redox transformation. We found that all thiols caused oxidation of Hg(0) under anoxic conditions but, contrary to expectation, compounds with higher S-oxidation states (e.g., disulfide) than thiols exhibited little or no reactivity with Hg(0) at pH 7. The rate and extent of Hg(0) oxidation varied widely, with smaller aliphatic thiols showing the greatest degree of oxidation. The mechanism of the oxidation is attributed to a two-step process involving adsorption of Hg(0) to thiols followed by the charge transfer from Hg(0) to electron acceptors. These observations demonstrate a unique thiol-induced oxidation pathway of dissolved Hg(0), with important implications for the redox transformation, speciation, and bioavailability of Hg for microbial methylation in anoxic environments.

Zheng, Wang [ORNL; Lin, Hui [ORNL; Mann, Benjamin F [ORNL; Liang, Liyuan [ORNL; Gu, Baohua [ORNL

2013-01-01

138

Thiol synthesis and arsenic hyperaccumulation in Pteris vittata (Chinese brake fern).  

Science.gov (United States)

Pteris vittata (Chinese brake fern) has potential for phytoremediation of As-contaminated sites. In this study, the synthesis of total thiols and acid-soluble thiols in P. vittata was investigated under arsenic exposure. The strong and positive correlation between As concentration and acid-soluble thiols in plant leaflets suggests that acid-soluble thiols may play a role in As detoxification. A major As-induced thiol was purified and characterized. A molecular ion (M + 1) of 540 m/z suggests that the thiol was a phytochelatin (PC) with two base units (PC(2)). However, the ratios of acid-soluble thiols to As in leaflets exposed to As ranged from 0.012 to 0.026, suggesting that only a very small part of As is complexed by PC(2). PCs could play a minor detoxification role in this hyperaccumulator. A PC-independent mechanism appears to be mainly involved in As tolerance, while PC-dependent detoxification seems to be a supplement. PMID:15261396

Zhang, Weihua; Cai, Yong; Downum, Kelsey R; Ma, Lena Q

2004-10-01

139

Thiol synthesis and arsenic hyperaccumulation in Pteris vittata (Chinese brake fern)  

Energy Technology Data Exchange (ETDEWEB)

Pteris vittata (Chinese brake fern) has potential for phytoremediation of As-contaminated sites. In this study, the synthesis of total thiols and acid-soluble thiols in P. vittata was investigated under arsenic exposure. The strong and positive correlation between As concentration and acid-soluble thiols in plant leaflets suggests that acid-soluble thiols may play a role in As detoxification. A major As-induced thiol was purified and characterized. A molecular ion (M+1) of 540 m/z suggests that the thiol was a phytochelatin (PC) with two base units (PC{sub 2}). However, the ratios of acid-soluble thiols to As in leaflets exposed to As ranged from 0.012 to 0.026, suggesting that only a very small part of As is complexed by PC{sub 2}. PCs could play a minor detoxification role in this hyperaccumulator. A PC-independent mechanism appears to be mainly involved in As tolerance, while PC-dependent detoxification seems to be a supplement.

Zhang Weihua; Cai Yong; Downum, Kelsey R.; Ma, Lena Q

2004-10-01

140

Thiol synthesis and arsenic hyperaccumulation in Pteris vittata (Chinese brake fern)  

International Nuclear Information System (INIS)

Pteris vittata (Chinese brake fern) has potential for phytoremediation of As-contaminated sites. In this study, the synthesis of total thiols and acid-soluble thiols in P. vittata was investigated under arsenic exposure. The strong and positive correlation between As concentration and acid-soluble thiols in plant leaflets suggests that acid-soluble thiols may play a role in As detoxification. A major As-induced thiol was purified and characterized. A molecular ion (M+1) of 540 m/z suggests that the thiol was a phytochelatin (PC) with two base units (PC2). However, the ratios of acid-soluble thiols to As in leaflets exposed to As ranged from 0.012 to 0.026, suggesting that only a very small part of As is complexed by PC2. PCs could play a minor detoxification role in this hyperaccumulator. A PC-independent mechanism appears to be mainly involved in As tolerance, while PC-dependent detoxification seems to be a supplement

2004-10-01

 
 
 
 
141

Identification of novel aroma-active thiols in pan-roasted white sesame seeds.  

Science.gov (United States)

Screening for aroma-active compounds in an aroma distillate obtained from freshly pan-roasted sesame seeds by aroma extract dilution analysis revealed 32 odorants in the FD factor range of 2-2048, 29 of which could be identified. The highest FD factors were found for the coffee-like smelling 2-furfurylthiol, the caramel-like smelling 4-hydroxy-2,5-dimethyl-3(2H)-furanone, the coffee-like smelling 2-thenylthiol (thiophen-2-yl-methylthiol), and the clove-like smelling 2-methoxy-4-vinylphenol. In addition, 9 odor-active thiols with sulfurous, meaty, and/or catty, black-currant-like odors were identified for the first time in roasted sesame seeds. Among them, 2-methyl-1-propene-1-thiol, (Z)-3-methyl-1-butene-1-thiol, (E)-3-methyl-1-butene-1-thiol, (Z)-2-methyl-1-butene-1-thiol, (E)-2-methyl-1-butene-1-thiol, and 4-mercapto-3-hexanone were previously unknown as food constituents. Their structures were confirmed by comparing their mass spectra and retention indices as well as their sensory properties with those of synthesized reference compounds. The relatively unstable 1-alkene-1-thiols represent a new class of food odorants and are suggested as the key contributors to the characteristic, but quickly vanishing, aroma of freshly ground roasted sesame seeds. PMID:20491509

Tamura, Hitoshi; Fujita, Akira; Steinhaus, Martin; Takahisa, Eisuke; Watanabe, Hiroyuki; Schieberle, Peter

2010-06-23

142

Changes in intestinal mucosal permeability caused by nonprotein thiol loss in rats.  

Science.gov (United States)

The barrier selectivity of the intestinal mucosal membrane permeability may be impaired in certain disease conditions. Membrane permeability was previously shown to be correlated with changes in nonprotein thiol in rat intestinal tissue by the everted sac method. In the present study, the mucosal effects of alloxan-induced diabetes and chronic alcohol administration to intact rats, as well as pre-treatment with diethyl maleate, ethanol, and salicylate, were investigated. In each case, a drop of mucosal nonprotein thiol was associated with an increased absorption of cefoxitin, cefmetazole, and phenol red, hydrophilic compounds that are poorly absorbed through intact membrane, and with a decreased absorption of L-phenylalanine. The effect of nonprotein thiol loss on rectal absorption of cefoxitin, cefmetazole, and phenol red was greater than that on the small intestinal absorption. The increase in phenol red absorption by diethyl maleate in the in vitro everted sac method correlated with Ca(2+) release from the intestinal mucosa, which was induced by nonprotein thiol loss. Resistance to the effect of nonprotein thiol loss on Ca(2+) homeostasis was greater in rat ileum than in rat colon (including rectum). The administration of cysteamine as an exogenous nonprotein thiol restored non-protein thiol levels in the mucosa along with the barrier function of the intestinal mucosa to the absorption of cefoxitin, cefmetazole, and phenol red. In contrast, the transport of L-phenylalanine in the small intestinal mucosa was not restored by cysteamine treatment. PMID:24271833

Nishihata, T; Nghiem, B T; Yoshitomi, H; Lee, C S; Dillsaver, M; Higuchi, T; Choh, R; Suzuka, T; Furuya, A; Kamada, A

1986-12-01

143

Low-molecular-weight thiols in streptomycetes and their potential role as antioxidants.  

Science.gov (United States)

The intracellular low-molecular-weight thiols present in five gram-positive Streptomyces species and one Flavobacterium species were analyzed by high-performance liquid chromatography after fluorescence labeling with monobromobimane. Bacteria were chosen to include penicillin and cephalosporin beta-lactam producers and nonproducers. No significant amount of glutathione was found in any of the streptomycetes. Major intracellular thiols in all strains examined were cysteine, coenzyme A, sulfide, thiosulfate, and an unknown thiol designated U17. Those streptomycetes that make beta-lactam antibiotics also produce significant amounts of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV), a key intermediate in their biosynthesis. In Streptomyces clavuligerus, a potent producer of beta-lactams, the level of ACV was low during the early phase of growth and increased rapidly toward the end of exponential growth, paralleling that of antibiotic production. These and other observations indicate that ACV does not function as a protective thiol in streptomycetes. U17 may have this role since it was the major thiol in all streptomycetes and appeared to occur at levels about 10-fold higher than those of the other thiols measured, including ACV. Purification and amino acid analysis of U17 indicated that it contains cysteine and an unusual amine that is not one of the common amino acids. This thiol is identical to an unknown thiol found previously in Micrococcus roseus and Streptomyces griseus. A high level of ergothioneine was found in Streptomyces lactamdurans, and several unidentified thiols were detected in this and other streptomycetes. PMID:8478335

Newton, G L; Fahey, R C; Cohen, G; Aharonowitz, Y

1993-05-01

144

Oxidative desorption of thiols as a route to controlled formation of binary self assembled monolayer surfaces  

International Nuclear Information System (INIS)

Binary self-assembled monolayers have been prepared by an alternative route to the conventional approach where a surface is exposed to a solution of both thiols at open circuit. A particular composition can be prepared with relative ease and the method is particularly useful for binary monolayers comprising two thiols with very different chain lengths since the problem of the longer chain thiol displacing the shorter over time is avoided. This is achieved by first preparing a full monolayer of the longer thiol, then oxidative desorption is carried out using cyclic voltammetry to remove a known fraction (as measured from the charge associated with gold oxide reduction) of the original SAM. Experiments with several thiols of chain lengths from 9 to 16 carbon atoms show that a considerable degree of control may be exerted over the rate at which the thiol is removed, using factors such as the potential limit, scan rate, pH and electrolyte polarity. The amount of thiol removed can thus also be controlled in a similar fashion. Once the oxidative desorption has taken place to the required degree, the vacancies created can be filled by exposure to a solution of a second thiol, differing in either chain length, termination or both. Deposition of thiols was carried out both under potential control (for longer chains) and by simple adsorption (for shorter chains). Several binary SAMs were prepared using this method and characterised using simple cyclic voltammetry with redox probes and selective reductive desorption. This method of preparation of binary SAMS may provide an alternative to both conventional methods using solution exposure and to methods that employ reductive desorption to expose selected facets on a polycrystalline surface. It may also be used to create partially blocked electrodes

2013-10-30

145

Determination of thiol functional groups on bacteria and natural organic matter in environmental systems.  

Science.gov (United States)

Organic thiols (R-SH) are known to react and form complexes with some toxic soft metals such as mercury (Hg) in both biotic and abiotic systems. However, a clear understanding of these interactions is currently limited because quantifying thiols in environmental matrices is difficult due to their low abundance, susceptibility to oxidation, and measurement interference by non-thiol compounds in samples. Here, we report a fluorescence-labeling method using a maleimide containing probe, ThioGlo-1 (TG-1), to determine total thiols directly on bacterial cells and natural organic matter (NOM). We systematically evaluated the optimal thiol labeling conditions and interference from organic compounds such as disulfide, methionine, thiourea, and amine, and inorganic ions such as Na(+), K(+), Ca(2+), Fe(2+), Cl(-), SO4(2-), HCO3(-), and SCN(-), and found that the method is highly sensitive and selective. Only relatively high levels of sulfide (S(2-)) and sulfite (SO3(2-)) significantly interfere with the thiol analysis. The method was successful in determining thiols in a bacterium Geobacter sulfurreducens PCA and its mutants in a phosphate buffered saline solution. The measured value of ~2.1 × 10(4) thiols cell(-1) (or ~0.07 µmol g(-1) wet cells) is in good agreement with that observed during reactions between Hg and PCA cells. Using the standard addition, we determined the total thiols of two reference NOM samples, the reduced Elliot soil humic acid and Suwanee River NOM, to be 3.6 and 0.7 µmol g(-1), respectively, consistent with those obtained based on their reactions with Hg. PMID:24401410

Rao, Balaji; Simpson, Carolyne; Lin, Hui; Liang, Liyuan; Gu, Baohua

2014-02-15

146

Determination of thiol functional groups on bacteria and natural organic matter in environmental systems  

Energy Technology Data Exchange (ETDEWEB)

Organic thiols (R-SH) are known to react and form complexes with some toxic soft metals such as mercury (Hg) in both biotic and abiotic systems. However, a clear understanding of these interactions is currently limited because quantifying thiols in environmental matrices is difficult due to their low abundance, susceptibility to oxidation, and measurement interference by non-thiol compounds in samples. Here, we report a fluorescence-labeling method using a maleimide containing probe, ThioGlo-1 (TG-1), to determine total thiols directly on bacterial cells and natural organic matter (NOM). We systematically evaluated the optimal thiol labeling conditions and interference from organic compounds such as disulfide, methionine, thiourea, and amine, and inorganic ions such as Na+, K+, Ca2+, Fe2+, Cl-, SO42-, HCO3-, and SCN-, and found that the method is highly sensitive and selective. Only relatively high levels of sulfide (S2-) and sulfite (SO32-) significantly interfere with the thiol analysis. The method was successful in determining thiols in a bacterium Geobacter sulfurreducens PCA and its mutants in a phosphate buffered saline solution. The measured value of ~2.1 104 thiols cell-1 (or ~0.07 mol g-1 wet cells) is in good agreement with that observed during reactions between Hg and PCA cells. Using the standard addition, we determined the total thiols of two reference NOM samples, the reduced Elliot soil humic acid and Suwanee River NOM, to be 3.6 and 0.7 mol g-1, respectively, consistent with those obtained based on their reactions with Hg.

Anandha Rao, Balaji [ORNL; Lin, Hui [ORNL; Liang, Liyuan [ORNL; Gu, Baohua [ORNL

2014-01-01

147

Regulation of human methylenetetrahydrofolate reductase by phosphorylation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of methylenetetrahydrofolate to methyltetrahydrofolate, the methyl donor for the conversion of homocysteine to methionine. Regulation of MTHFR activity is crucial for maintaining cellular concentrations of methionine and S-adenosylmethionine (AdoMet). Purified recombinant human MTHFR expressed in insect cells is multiply phosphorylated on an N-terminal extension of the protein that contains a highly conserved serine-rich regi...

Yamada, Kazuhiro; Strahler, John R.; Andrews, Philip C.; Matthews, Rowena G.

2005-01-01

148

3-Methyl-2-butene-1-thiol: identification, analysis, occurrence and sensory role of an uncommon thiol in wine.  

Science.gov (United States)

A highly uncommon odorant, 3-methyl-2-butene-1-thiol was detected by using Gas Chromatography-Olfactometry (GC-O) and unequivocally identified for the first time in wine. A purge and trap sampling technique which provides highly representative extracts for olfactometric analysis was used for the extraction of the volatile fraction of a Spanish red wine made from Prieto Picudo grapes. The identification of the odorant was achieved by multidimensional gas chromatography analysis of the same purge and trap extract. Mass spectrum and retention indices in both polar and non-polar columns allowed knowing unequivocally the identity. To obtain quantitative data a method was validated for the analysis of the compound at ng L(-1) level with acceptable precision. This powerful odorant presented an odor threshold in wine of 0.5-1 ng L(-1) and it has been detected in several Prieto Picudo wines at concentrations slightly above the odor threshold. PMID:22967545

San-Juan, Felipe; Cacho, Juan; Ferreira, Vicente; Escudero, Ana

2012-09-15

149

Characterization of erythrose reductases from filamentous fungi.  

Science.gov (United States)

Proteins with putative erythrose reductase activity have been identified in the filamentous fungi Trichoderma reesei, Aspergillus niger, and Fusarium graminearum by in silico analysis. The proteins found in T. reesei and A. niger had earlier been characterized as glycerol dehydrogenase and aldehyde reductase, respectively. Corresponding genes from all three fungi were cloned, heterologously expressed in Escherichia coli, and purified. Subsequently, they were used to establish optimal enzyme assay conditions. All three enzymes strictly require NADPH as cofactor, whereas with NADH no activity could be observed. The enzymatic characterization of the three enzymes using ten substrates revealed high substrate specificity and activity with D-erythrose and D-threose. The enzymes from T. reesei and A. niger herein showed comparable activities, whereas the one from F. graminearum reached only about a tenth of it for all tested substrates. In order to proof in vivo the proposed enzyme function, we overexpressed the erythrose reductase-encoding gene in T. reesei. An increased production of erythritol by the recombinant strain compared to the parental strain could be detected. PMID:23924507

Jovanovi?, Birgit; Mach, Robert L; Mach-Aigner, Astrid R

2013-01-01

150

Low molecular weight thiols in arsenic hyperaccumulator Pteris vittata upon exposure to arsenic and other trace elements  

Energy Technology Data Exchange (ETDEWEB)

Low molecular weight thiol-containing compounds have been reported to play an important role in metal detoxification and accumulation in some higher plants. The formation of these low molecular weight thiols in the recently discovered arsenic hyperaccumulator, Chinese Brake fern (Pteris vittata) upon exposure to arsenic and other trace metals was investigated. In addition to cysteine and glutathione, an unidentified thiol was observed in the plants exposed to arsenic, which was not found in the control. The concentration of the unidentified thiol showed a very strong and positive correlation with arsenic concentration in the leaflets. The unidentified thiol was low in rachises and undetectable in the roots for As-treated plants. Total and acid-soluble thiols were also measured and the results indicated that arsenic mainly stimulated the synthesis of acid-soluble thiol in Chinese Brake. The investigations of other trace elements (Cd, Cu, Cr, Zn, Pb, Hg, and Se) showed that these elements were not accumulated in Chinese Brake to high levels and the synthesis of the unidentified thiol in the plant was not observed. Our study suggests that the unidentified thiol was induced specifically by arsenic and the distribution patterns of the unidentified thiol and arsenic in the plant were consistent, indicating that the synthesis of this compound was related to As exposure. - Arsenic induces synthesis of low molecular weight thiols in the arsenic hyperaccumulator Pteris vittata.

Cai Yong; Su Jinhui; Ma, Lena Q

2004-05-01

151

Low molecular weight thiols in arsenic hyperaccumulator Pteris vittata upon exposure to arsenic and other trace elements  

International Nuclear Information System (INIS)

Low molecular weight thiol-containing compounds have been reported to play an important role in metal detoxification and accumulation in some higher plants. The formation of these low molecular weight thiols in the recently discovered arsenic hyperaccumulator, Chinese Brake fern (Pteris vittata) upon exposure to arsenic and other trace metals was investigated. In addition to cysteine and glutathione, an unidentified thiol was observed in the plants exposed to arsenic, which was not found in the control. The concentration of the unidentified thiol showed a very strong and positive correlation with arsenic concentration in the leaflets. The unidentified thiol was low in rachises and undetectable in the roots for As-treated plants. Total and acid-soluble thiols were also measured and the results indicated that arsenic mainly stimulated the synthesis of acid-soluble thiol in Chinese Brake. The investigations of other trace elements (Cd, Cu, Cr, Zn, Pb, Hg, and Se) showed that these elements were not accumulated in Chinese Brake to high levels and the synthesis of the unidentified thiol in the plant was not observed. Our study suggests that the unidentified thiol was induced specifically by arsenic and the distribution patterns of the unidentified thiol and arsenic in the plant were consistent, indicating that the synthesis of this compound was related to As exposure. - Arsenic induces synthesis of low molecular weight thiols in the arsenic hyperaccumulator Pteris vittata

2004-05-01

152

Interaction of thiols and non-thiol {center_dot}OH scavengers in the modification of radiation-induced DNA damage  

Energy Technology Data Exchange (ETDEWEB)

Oxygen has long been known to sensitize cells to the lethal effects of ionizing radiation and is widely believed to do so by the fixation of potentially reversible radical damage to cellular DNA. A number of studies have suggested that this widely observed oxygen enhancement of cell killing requires the presence of reduced thiols. Published in vitro studies of the modification of DNA damage by glutathione or other thiols have generally shown peak oxygen enhancement ratios (OERs) much higher than those observed for cell killing. However, these studies measured loss of DNA transforming activity or induction of single-strand DNA breaks (SSBs), related endpoints which are not thought to represent lethal lesions, rather than double-strand breaks (DSBs), which are generally believed to be the dominant lethal lesions from ionizing radiation. In addition, non-thiol scavengers of OH radicals were not generally present. There is also evidence that, in addition to their protective effects, some non-thiol {center_dot}OH scavengers can produce radicals which are damaging to DNA under anoxic conditions. In the present investigation, the authors have adapted a previously used in vitro model system to simultaneously investigate the effects on radiation-induced single- and double-strand DNA breaks of various combinations of glutathione and glycerol, a widely used non-thiol scavenger, in the presence and absence of oxygen.

Krisch, R.E.; Ayene, I.S.; Koch, C.J. [Univ. of Pennsylvania School of Medicine, Philadelphia, PA (United States). Dept. of Radiation Oncology

1995-12-31

153

Nitrate Reductase from Monoraphidium braunii: Immunocytochemical Localization and Immunological Characterization.  

Science.gov (United States)

Homogeneous nitrate reductase (EC 1.6.6.2) from Monoraphidium braunii was obtained by means of affinity chromatography in blue-Sepharose and gel filtration. After electrophoresis in polyacrylamide, gel slices containing pure nitrate reductase were disrupted and injected into previously unimmunized rabbits. The antiserum produced after several weeks was found to inhibit the different activities of nitrate reductase to a similar degree. Monospecificity of the antiserum was demonstrated by Ouchterlony double diffusion and crossed immunoelectrophoresis. The antibodies were purified by immunoabsorption to Sepharose-bound nitrate reductase.The intracellular location of nitrate reductase in green algae was examined by applying an immunocytochemical method to M. braunii cells. Ultrathin frozen sections were first treated with immunopurified anti-nitrate reductase monospecific antibodies, followed by incubation with colloidal gold-labeled goat antirabbit immunoglobulin G as a marker. The enzyme was specifically located in the pyrenoid region of the chloroplast. PMID:16664292

Lopez-Ruiz, A; Roldan, J M; Verbelen, J P; Diez, J

1985-07-01

154

Effect of abiotic stress stimuli on S-nitrosoglutathione reductase in plants.  

Science.gov (United States)

S-nitrosylation of protein cysteine thiol groups has recently emerged as a widespread and important reversible post-translational protein modification, involved in redox signalling pathways of nitric oxide and reactive nitrogen species. S-nitrosoglutathione reductase (GSNOR), member of class III alcohol dehydrogenase family (EC 1.1.1.1), is considered the key enzyme in the catabolism of major low molecular S-nitrosothiol, S-nitrosoglutathione, and hence to control the level of protein S-nitrosylation. Changes of GSNOR activity after exposure to different abiotic stress conditions, including low and high temperature, continuous dark and de-etiolation, and mechanical injury, were investigated in important agricultural plants. Significantly higher GSNOR activity was found under normal conditions in leaves of Cucumis spp. genotype sensitive to biotrophic pathogen Golovinomyces cichoracearum. GSNOR activity was generally increased in all studied plants by all types of stress conditions. Strong down-regulation of GSNOR was observed in hypocotyls of etiolated pea plants, which did not recover to values of green plants even 168 h after the transfer of etiolated plants to normal light regime. These results point to important role of GSNOR during normal plant development and in plant responses to several types of abiotic stress conditions. PMID:24104214

Kubienová, Lucie; Tichá, Tereza; Jahnová, Jana; Luhová, Lenka; Mieslerová, Barbora; Pet?ivalský, Marek

2014-01-01

155

Chloroplast NADPH-thioredoxin reductase interacts with photoperiodic development in Arabidopsis.  

Science.gov (United States)

Chloroplast NADPH-thioredoxin reductase (NTRC) belongs to the thioredoxin systems that control crucial metabolic and regulatory pathways in plants. Here, by characterization of T-DNA insertion lines of NTRC gene, we uncover a novel connection between chloroplast thiol redox regulation and the control of photoperiodic growth in Arabidopsis (Arabidopsis thaliana). Transcript and metabolite profiling revealed severe developmental and metabolic defects in ntrc plants grown under a short 8-h light period. Besides reduced chlorophyll and anthocyanin contents, ntrc plants showed alterations in the levels of amino acids and auxin. Furthermore, a low carbon assimilation rate of ntrc leaves was associated with enhanced transpiration and photorespiration. All of these characteristics of ntrc were less severe when plants were grown under a long 16-h photoperiod. Transcript profiling revealed that the mutant phenotypes of ntrc were accompanied by differential expression of genes involved in stomatal development, chlorophyll biosynthesis, chloroplast biogenesis, and circadian clock-linked light perception systems in ntrc plants. We propose that NTRC regulates several key processes, including chlorophyll biosynthesis and the shikimate pathway, in chloroplasts. In the absence of NTRC, imbalanced metabolic activities presumably modulate the chloroplast retrograde signals, leading to altered expression of nuclear genes and, ultimately, to the formation of the pleiotrophic phenotypes in ntrc mutant plants. PMID:19151130

Lepistö, Anna; Kangasjärvi, Saijaliisa; Luomala, Eeva-Maria; Brader, Günter; Sipari, Nina; Keränen, Mika; Keinänen, Markku; Rintamäki, Eevi

2009-03-01

156

Molybdenum effector of fumarate reductase repression and nitrate reductase induction in Escherichia coli.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In Escherichia coli the presence of nitrate prevents the utilization of fumarate as an anaerobic electron acceptor. The induction of the narC operon encoding the nitrate reductase is coupled to the repression of the frd operon encoding the fumarate reductase. This coupling is mediated by nitrate as an effector and the narL product as the regulatory protein (S. Iuchi and E. C. C. Lin, Proc. Natl. Acad. Sci. USA 84:3901-3905, 1987). The protein-ligand complex appears to control narC positively ...

Iuchi, S.; Lin, E. C.

1987-01-01

157

Nitrate reductase of green algae is located in the pyrenoid.  

Science.gov (United States)

Antibodies against nitrate reductase from Monoraphidium braunii have been used to determine the antigenic relationships of nitrate reductases from different green algae. Nitrate reductases from Chlamydomonas reinhardii, Chlorella fusca, Dunaliella salina, and Scenedesmus obliquus, were inhibited by, and cross-reacted with, antibodies raised against the enzyme from Monoraphidium braunii.These antibodies were also used to determine, by immunoelectron microscopy, the intracellular location of nitrate reductase in the aforementioned green algae. In all cases, the enzyme was specifically located in the pyrenoid. PMID:16664519

Lopez-Ruiz, A; Verbelen, J P; Roldan, J M; Diez, J

1985-12-01

158

Quantification of methanogenic heterodisulfide reductase activity in biogas sludge.  

Science.gov (United States)

Methanogenic archaea are essential for the production of methane in biogas plants. Here we present enzymatic test systems for the analysis of the metabolic activity of methanogens based on the heterodisulfide reductase reaction. The first rapid test shows that heterodisulfide reductase can be detected in 1 g of biogas sludge after sonication and centrifugation. The resulting cell lysate used reduced methylviologen for heterodisulfide reduction, a reaction that is specifically catalyzed by methanogenic heterodisulfide reductase. In the second test cell lysate from 60 g of biogas sludge was separated by ultracentrifugation. Both, cytoplasmic membrane and cytoplasmic fractions revealed heterodisulfide reductase activity, indicating the presence of hydrogenotrophic and aceticlastic methanogens, respectively. PMID:24721213

Refai, Sarah; Berger, Stefanie; Wassmann, Kati; Deppenmeier, Uwe

2014-06-20

159

The intracellular redox stress caused by hexavalent chromium is selective for proteins that have key roles in cell survival and thiol redox control  

International Nuclear Information System (INIS)

Hexavalent chromium [Cr(VI)] compounds (e.g. chromates) are strong oxidants that readily enter cells where they are reduced to reactive Cr intermediates that can directly oxidize some cell components and can promote the generation of reactive oxygen and nitrogen species. Inhalation is a major route of exposure which directly exposes the bronchial epithelium. Previous studies with non-cancerous human bronchial epithelial cells (BEAS-2B) demonstrated that Cr(VI) treatment results in the irreversible inhibition of thioredoxin reductase (TrxR) and the oxidation of thioredoxins (Trx) and peroxiredoxins (Prx). The mitochondrial Trx/Prx system is somewhat more sensitive to Cr(VI) than the cytosolic Trx/Prx system, and other redox-sensitive mitochondrial functions are subsequently affected including electron transport complexes I and II. Studies reported here show that Cr(VI) does not cause indiscriminant thiol oxidation, and that the Trx/Prx system is among the most sensitive of cellular protein thiols. Trx/Prx oxidation is not unique to BEAS-2B cells, as it was also observed in primary human bronchial epithelial cells. Increasing the intracellular levels of ascorbate, an endogenous Cr(VI) reductant, did not alter the effects on TrxR, Trx, or Prx. The peroxynitrite scavenger MnTBAP did not protect TrxR, Trx, Prx, or the electron transport chain from the effects of Cr(VI), implying that peroxynitrite is not required for these effects. Nitration of tyrosine residues of TrxR was not observed following Cr(VI) treatment, further ruling out peroxynitrite as a significant contributor to the irreversible inhibition of TrxR. Cr(VI) treatments that disrupt the TrxR/Trx/Prx system did not cause detectable mitochondrial DNA damage. Overall, the redox stress that results from Cr(VI) exposure shows selectivity for key proteins which are known to be important for redox signaling, antioxidant defense, and cell survival.

2011-03-15

160

Responses of Monolayer Membrances of Thiol-Containing Lipids to Odor Substances  

Science.gov (United States)

It is known that thiol-containing compounds form monolayer membranes on a gold surface via chemisorption from organic solvents in terms of a strong connection ability between thiol and the metal. Here we prepared different kinds of thiol-containing lipids and fabricated monolayer membranes on the gold disk electrode whose surface structures were similar to biological membranes. Responses of this lipid-coated electrode to odor substances were examined by an electrochemical method of a cyclic voltammetry. Blocking ability for the redox reaction of Fe(CN)63- was found to change upon adsorption of odor substances into monolayer membranes. The order of threshold values to detect the odorants was ?-iononeamyl acetate; this order was the same as that in the human olfactory sense. The present study indicates that the monolayer membrane of thiol-containing lipids can be useful as a transducer of an odor sensor.

Miyazaki, Yoshio; Hayashi, Kenshi; Toko, Kiyoshi; Yamafuji, Kaoru; Nakashima, Naotoshi

1992-05-01

 
 
 
 
161

Effect of hydroxyurea and amethopterin on radiosensitivity and thiol content of biological objects  

International Nuclear Information System (INIS)

It has been shown on a whole organism (mice) and isolated cells (Ehrlich ascites tumour) that hydroxyurea has a radiosensitizing action and decreases the endogenous thiol content. Amethopterin fails to produce the same effects

1976-07-01

162

AFM-assisted fabrication of thiol SAM pattern with alternating quantified surface potential  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Thiol self-assembled monolayers (SAMs are widely used in many nano- and bio-technology applications. We report a new approach to create and characterize a thiol SAMs micropattern with alternating charges on a flat gold-coated substrate using atomic force microscopy (AFM and Kelvin probe force microscopy (KPFM. We produced SAMs-patterns made of alternating positively charged, negatively charged, and hydrophobic-terminated thiols by an automated AFM-assisted manipulation, or nanografting. We show that these thiol patterns possess only small topographical differences as revealed by AFM, and distinguished differences in surface potential (20-50 mV, revealed by KPFM. The pattern can be helpful in the development of biosensor technologies, specifically for selective binding of biomolecules based on charge and hydrophobicity, and serve as a model for creating surfaces with quantified alternating surface potential distribution.

Simons Janet

2011-01-01

163

Highly sensitive EUV-resist based on thiol-ene radical reaction  

Science.gov (United States)

Non-conventional chemically amplified (CA) resist was designed. Photo-induced thiol/ene radical reaction was used to insolubilize the resist based on multifunctional thiol and poly(4-hydroxystyrene) (PHS) derivatives. Hydroxy groups of PHS were modified with allyl or propargyl moiety. Dissolution property of the modified-PHS in TMAHaq solution was affected by the modification degree. Resist was prepared by mixing the modified-PHS, multifunctional thiol compound, and photoradical generator. Photosensitivity of the resist was studied at 254 and 13.5 nm. The sensitivity was strongly affected by the modification degree of PHS, molecular weight of PHS, molecular weight distribution of PHS, amounts of thiol compound and photoradical generator added. It was found that the present resist system was highly sensitive to EUV exposure.

Shirai, Masamitsu; Maki, Koichi; Okamura, Haruyuki; Kaneyama, Koji; Itani, Toshiro

2010-03-01

164

Kinetics and physical properties of photolatent base catalyzed thiol-epoxy resins  

Science.gov (United States)

Typical epoxy resin systems based on multifunctional epoxides and multifunctional amines yield polymeric materials with unrivaled chemical resistance, toughness, and adhesion. Unfortunately amine cured epoxy resins must be mixed immediately prior to application because reactivity of the amine and epoxy is too high. Thiol-epoxy resins offer a less reactive alternative to these traditional epoxy resins and are catalyzed by the addition of a tertiary amine, such as DBN. In this study a combination of a diepoxide with multifunctional thiols based on mercaptoacetate (MA) and mercaptopropionate (MP) were polymerized using a photolatent base catalyst or DBN. The reactivity of the MA and MP based thiols were characterized using Real-time FT-IR. Mechanical and thermal properties of the resins were characterized using DMA, DSC, MTS, pencil hardness, and impact resistance. Thiol-cured epoxy systems have uniform network structures, as indicated by sharp tan ? peaks and distinct glass transition region shown by DMA and DSC respectively.

Comer, Christopher; McNair, Olivia; Hoyle, Charles; Savin, Daniel

2010-03-01

165

A Thiol-functionalized Nanoporous Silica Sorbent for Removal of Mercury from Actual Industrial Waste  

Energy Technology Data Exchange (ETDEWEB)

Tests were conducted using a novel sorbent, thiol-functionalized nanoporous silica material for its effectiveness in removing mercury from two waste streams. These waste streams originated from pilot-scale tests being conducted to refine the process of vitrifying radioactive sludges that result from chemical separation of targeted actinide species. Two waste streams resulting from this process (High Efficiency Mist Eliminator, HEME and melter condensate) contain mercury concentrations that ranged from ~700 to ~5 ppm respectively. The data showed that thiol functionalized Self-Assembled Monolayers on Mesoporous Silica (thiol-SAMMS) was effective in reducing mercury concentrations in these two waste streams to meet a treatment limit of ?0.2 ppm. These tests demonstrated that the thiol-SAMMS can very selectively (Kd: 5 x 104 and 1 x 105 ml/g) and effectively scavenge strongly complexed mercury from dilute to relatively concentrated waste matrices to meet the UTS limits for effluents.

Mattigod, Shas V.; Fryxell, Glen E.; Parker, Kent E.

2007-07-02

166

Controlling Topological Entanglement in Engineered Protein Hydrogels with a Variety of Thiol Coupling Chemistries  

Directory of Open Access Journals (Sweden)

Full Text Available Topological entanglements between polymer chains are achieved in associating protein hydrogels through the synthesis of high molecular weight proteins via chain extension using a variety of thiol coupling chemistries, including disulfide formation, thiol-maleimide, thiol-bromomaleimide and thiol-ene. Coupling of cysteines via disulfide formation results in the most pronounced entanglement effect in hydrogels, while other chemistries provide versatile means of changing the extent of entanglement, achieving faster chain extension, and providing a facile method of controlling the network hierarchy and incorporating stimuli responsivities. The addition of trifunctional coupling agents causes incomplete crosslinking and introduces branching architecture to the protein molecules. The high-frequency plateau modulus and the entanglement plateau modulus can be tuned by changing the ratio of difunctional chain extender to the trifunctional branching unit. Therefore, these chain extension reactions show promise in delicately controlling the relaxation and mechanical properties of engineered protein hydrogels in ways that complement their design through genetic engineering.

BradleyOlsen

2014-05-01

167

New functional materials for heavy metal sorption: “Supramolecular” attachment of thiols to mesoporous silica substrates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new class of sorbent material, which exhibits exceptional metal capture from contaminated natural water, features aromatic thiol ligands reversibly bound to functionalized mesoporous silica through non-covalent interactions and have the potential of being regenerable.

Carter, Timothy G.; Yantasee, Wassana; Sangvanich, Thanapon; Fryxell, Glen E.; Johnson, Darren W.; Addleman, R. Shane

2008-01-01

168

Controlling topological entanglement in engineered protein hydrogels with a variety of thiol coupling chemistries  

Science.gov (United States)

Topological entanglements between polymer chains are achieved in associating protein hydrogels through the synthesis of high molecular weight proteins via chain extension using a variety of thiol coupling chemistries, including disulfide formation, thiol-maleimide, thiol-bromomaleimide and thiol-ene. Coupling of cysteines via disulfide formation results in the most pronounced entanglement effect in hydrogels, while other chemistries provide versatile means of changing the extent of entanglement, achieving faster chain extension, and providing a facile method of controlling the network hierarchy and incorporating stimuli responsivities. The addition of trifunctional coupling agents causes incomplete crosslinking and introduces branching architecture to the protein molecules. The high-frequency plateau modulus and the entanglement plateau modulus can be tuned by changing the ratio of difunctional chain extender to the trifunctional branching unit. Therefore, these chain extension reactions show promise in delicately controlling the relaxation and mechanical properties of engineered protein hydrogels in ways that complement their design through genetic engineering.

Tang, Shengchang; Olsen, Bradley D.

2014-01-01

169

Maleimide-functionalised organoruthenium anticancer agents and their binding to thiol-containing biomolecules.  

Science.gov (United States)

Ru(II)(arene) anticancer compounds with maleimide functionality were prepared to allow selective interaction with thiol-containing biomolecules and thereby enforcing the selective delivery of the compounds to the tumour. PMID:22003496

Hanif, Muhammad; Nazarov, Alexey A; Legin, Anton; Groessl, Michael; Arion, Vladimir B; Jakupec, Michael A; Tsybin, Yury O; Dyson, Paul J; Keppler, Bernhard K; Hartinger, Christian G

2012-02-01

170

Characterization of chitosan thiolation and application to thiol quantification onto nanoparticle surface  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of the present work was to establish a simple and appropriated method for the quantification of thiol groups standing on the surface of core-shell nanoparticles elaborated with poly(isobutyl cyanoacrylates) and thiolated chitosan.

Arpicco, Silvia Maria

2007-01-01

171

Interactions of oxaliplatin with the cytoplasmic thiol containing ligand glutathione.  

Science.gov (United States)

The complexation of the Pt-based anti-cancer drug oxaliplatin (OxPt) with biological ligands other than DNA is believed to be a major cellular sink for the drug reducing its therapeutic effect and acting as a potential cause of toxicity. In this paper, linear ion trap electrospray ionization mass spectrometry was employed to study the interaction of oxaliplatin with the cytoplasmic thiol containing tripeptide ligand ?-l-glutamyl-l-cysteinyl-glycine (GSH) this being the most abundant low-molecular-weight thiol containing molecule in human cells. Evidence of protonated dimers and multimers of oxaliplatin, protonated multimers of glutathione as well as several different combinations of these protonated species is presented. Most species observed were unambiguously assigned and compared to their theoretical isotopic patterns. Fragmentation of the collisionally-activated protonated complex of glutathione with oxaliplatin [GSH + OxPt + H](+) resulted in the formation of several species. No experimental evidence for [GSH + H](+) formation from the [OxPt + GSH + H](+) precursor was observed. Density functional calculations at B3LYP/LANL2DZ were used to obtain structural information and relative free energies of different isomers of the observed precursor [OxPt + GSH + H](+) both in the gas phase and in solution as well as to probe its fragmentation, highlighting mechanisms that account for all the experimental results. Data are presented to show several binding modes between electron rich sites such as S, N, O centers of GSH and the Pt metal of oxaliplatin. Calculations were also employed to obtain proton affinities and free energies of key reactions. The proton affinities of GSH and OxPt at 298 K were calculated to be 255.3 and 233.5 kcal mol(-1) respectively. The enthalpy and free energy, based on the most thermodynamically favored conformers of the reactants and products, for the addition reaction [Pt(dach)](2+) + [GSH - H](-) ? [GSH - H + Pt(dach)](+) (where dach represents diaminocyclohexane) in the gas phase at 298 K were determined to be -311.3 and -290.2 kcal mol(-1) respectively. Similarly, the enthalpy of the gas phase reaction [Pt(dach)](2+) + GSH ? [GSH + Pt(dach)](2+) at 298 K was determined to be -169.2 kcal mol(-1). PMID:23128601

Shoeib, Tamer; Sharp, Barry L

2012-12-01

172

Reactions of thiophenes and thiols with supported molybdenum oxides: A model for hydrodesulfurization reactions  

Energy Technology Data Exchange (ETDEWEB)

Organometallic precursors were used to prepare silica-supported molybdenum oxides as isolated species, pairs or dimers with oxidation states ranging from 1+ to 4+. Our goal is to understand the role of oxidation state and structure on the hydrodesulfurization of thiophenes, compounds typically found in fossil fuels, and thiols. We used gas chromatography and mass spectroscopy to study the reactions of thiophenes and thiols with supported molybdenum oxide systems.

Sullivan, D.L.; Ekerdt, J.G. [Univ. of Texas, Austin, TX (United States)

1995-12-31

173

A method for site-specific labeling of multiple protein thiols  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a generic method for the site-specific and differential labeling of multiple cysteine residues in one protein. Phenyl arsenic oxide has been employed as a protecting group of two closely spaced thiols, allowing first labeling of a single thiol. Subsequently, the protecting group is removed, making available a reactive dithiol site for labeling with a second probe. For proof-of-principle, single and triple Cys mutants of the sulphate binding protein of an ABC transporter were constr...

Kuiper, Johanna M.; Pluta, Radek; Huibers, Wim H. C.; Fusetti, Fabrizia; Geertsma, Eric R.; Poolman, Bert

2009-01-01

174

Optimization of Optical Properties of Polycarbonate Film with Thiol Gold-Nanoparticles  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new nanostructured composite film based on thiol gold nanoparticles dispersed in polycarbonate and prepared by evaporating a solution of 1-dodecanthiol gold nanoparticles and polycarbonate was developed for applications as optical lenses. Lenses with superior mechanical properties, coloring and UV ray absorption and with the same transparency as the matrix were obtained. The supporting highly transparent polycarbonate matrix and the chloroform solution of thiol gold nanoparticles, 3 nm mean...

2009-01-01

175

Biosynthesis and functions of bacillithiol, a major low-molecular-weight thiol in Bacilli  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Bacillithiol (BSH), the ?-anomeric glycoside of L-cysteinyl-D-glucosamine with L-malic acid, is a major low-molecular-weight thiol in Bacillus subtilis and related bacteria. Here, we identify genes required for BSH biosynthesis and provide evidence that the synthetic pathway has similarities to that established for the related thiol (mycothiol) in the Actinobacteria. Consistent with a key role for BSH in detoxification of electrophiles, the BshA glycosyltransferase and BshB1 deacetylase are ...

Gaballa, Ahmed; Newton, Gerald L.; Antelmann, Haike; Parsonage, Derek; Upton, Heather; Rawat, Mamta; Claiborne, Al; Fahey, Robert C.; Helmann, John D.

2010-01-01

176

Low-molecular-weight thiols in streptomycetes and their potential role as antioxidants.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The intracellular low-molecular-weight thiols present in five gram-positive Streptomyces species and one Flavobacterium species were analyzed by high-performance liquid chromatography after fluorescence labeling with monobromobimane. Bacteria were chosen to include penicillin and cephalosporin beta-lactam producers and nonproducers. No significant amount of glutathione was found in any of the streptomycetes. Major intracellular thiols in all strains examined were cysteine, coenzyme A, sulfide...

1993-01-01

177

Occurrence of polyfunctional thiols in sorghum beer "ikigage" made with Vernonia amygdalina "umubirizi"  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several polyfunctional thiols have been previously identified in beers made from barley and hops. These compounds have not been investigated in beers brewed with non-Western raw materials. Here we have performed a thiol-specific extraction with p-hydroxymercuribenzoic acid on a traditional ikigage sorghum beer from Rwandese peasants (use of Vernonia amygdalina just for yeast propagation), and on two pilot beers with addition (or not) of V. amygdalina in the boiling kettle, instead of hops. G...

Lyumugabe Loshima, Franc?ois

2012-01-01

178

Occurrence of polyfunctional thiols in sorghum beer 'ikigage' made with Vernonia amygdalina 'umubirizi'  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several polyfunctional thiols have been previously identified in beers made from barley and hops. These compounds have not been investigated in beers brewed with 'non-Western' raw materials. Here we have performed a thiol-specific extraction with p-hydroxymercuribenzoic acid on a traditional ikigage sorghum beer from Rwandese peasants (use of Vernonia amygdalina just for yeast propagation), and on two pilot beers with addition (or not) of V. amygdalina in the boiling kettle, instead of hops. ...

Lyumugabe, Franc?ois; Gros, Jacques; Thonart, Philippe; Collin, Sonia

2012-01-01

179

High catalase and low thiol levels in adult-ADHD patients  

Directory of Open Access Journals (Sweden)

Conclusions: The results of the present study may indicate that thiol levels may be decreased with in reaction of increased CAT levels and thiol act like a pro-oxidant. This study may be considered as one of the initial phase studies that lighten the relationship between oxidative stress and A-ADHD. There is a need for further studies that will prove this relationship exactly.

gokay alpak

2014-01-01

180

Proximity of thiol esters and bait region in human ?2-macroglobulin: paramagnetic mapping  

International Nuclear Information System (INIS)

The two key structural features of ?2-macroglobulin (?2M) involved in inhibitory caging of proteases are the thiol ester and the bait region. This paper examines the environment of the hydrolyzed thiol ester in methylamine-treated human ?2M and the separation between the bait region and the thiol ester and between the four thiol esters in the tetramer to try to further our understanding of how bait region proteolysis triggers thiol ester cleavage. The sulfhydryl groups of Cys-949, formed upon cleavage of the thiol ester by methylamine, were specifically labeled with the nitroxide spin-labels. ESR spectra of these ?2M derivative showed that label I is firmly held and label II has limited freedom of rotation consistent with location of the cysteine residue in a narrow cavity. Label III has much greater motional freedom. From the absence of dipole-dipole splittings in the ESR spectra, it is concluded that the four nitroxide groups in the tetramer are more than 20 A apart for both label I and label II. Label I broadens 1H NMR signals from one phenylalanyl, one tyrosyl, and four histidyl residues in the bait region. Separations of 11-17 A are estimated between the nitroxide of label I and these residues. Label II is further away and only broadens resonances from one of the histidines. The bait region is thus shown to be quite close to the thiol ester in the methylamine-treated form of ?2M and in addition must have a compact structure. It is suggested that the bait region exists as a loop of two strands in ? conformation in the native structure and that proteolytic cleavage disrupts the loop and triggers thiol ester cleavage

1988-04-19

 
 
 
 
181

One-pot, additive-free preparation of functionalized polyurethanes via amine-thiol-ene conjugation  

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A straightforward, isocyanate-free method for the synthesis of functionalized polyurethanes, based on amine-thiol-ene conjugation, was elaborated. Aminolysis of a readily available AB'-urethane monomer, containing both an acrylate (A) and a thiolactone unit (B'), facilitates the preparation of various reactive thiol-acrylates. In situ polymerization via Michael addition proceeds under ambient conditions, yielding polyurethanes with a large variety of chemical functionalities. Side-chain funct...

Espeel, Pieter; Goethals, Fabienne; Driessen, Frank; Nguyen, Le Thu Thi; Du Prez, Filip

2013-01-01

182

Cooperative functions of manganese and thiol redox system against oxidative stress in human spermatozoa  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Aims: In this study, the effects of 0.1 mM Mn 2+ on thiol components (total thiols [TSH], glutathione reduced [GSH], glutathione oxidized [GSSG] and redox ratio [GSH/ GSSG]) have been determined in human spermatozoa. Settings and Design: The subjects of the study were healthy males having more than 75% motility and 80 x 10 6 sperms/mL. Materials and Methods: Fresh semen was suspended in phosphate-buffered saline (PBS) (pH 7.2) an...

Bansal Amrit; Kaur Anand

2009-01-01

183

Macromolecular design : UV-curable thiol-ene networks based on renewable resources  

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Plant oils and terpenes are ubiquitous natural renewable compounds. The double bonds contained in most of these monomers can be utilized via the photo-induced free-radical thiol–ene reaction to create novel bio-derived polymer thermosets representing a valuable ‘green’ alternative to petrochemical olefins and resulting synthetic plastic materials. Nevertheless, there are several factors limiting their applicability, the first one being the relatively slow reaction rates towards thiol–...

2013-01-01

184

Undeca-carbonyl-?(2)-methane-thiol-ato-?(2)-[(pyridin-2-yl)methane-thiol-ato]-?(4)-sulfido-tetra-iron(II)(2 Fe-Fe).  

Science.gov (United States)

The title compound, [Fe(4)(C(6)H(6)NS)(CH(3)S)S(CO)(11)], com-prises two butterfly-shaped sub-cluster cores, Fe(2)S(2)N and Fe(2)S(2), joined together by a spiro-type ?(4)-S atom. The (pyridin-2-yl)methane-thiol-ate ligand is attached to the Fe(2)(CO)(5) unit in a ?-?N:?(2)S mode, and the methane-thiol-ate ligand is coordinated to the Fe(2)(CO)(6) unit in a ?-?(2)S fashion. PMID:22199559

Shi, Yao-Cheng; Lai, Liang; Shen, Wen-Bin; Yuan, Li-Min

2011-12-01

185

Undeca­carbonyl-?2-methane­thiol­ato-?2-[(pyridin-2-yl)methane­thiol­ato]-?4-sulfido-tetra­iron(II)(2 Fe—Fe)  

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The title compound, [Fe4(C6H6NS)(CH3S)S(CO)11], com­prises two butterfly-shaped sub-cluster cores, Fe2S2N and Fe2S2, joined together by a spiro-type ?4-S atom. The (pyridin-2-yl)methane­thiol­ate ligand is attached to the Fe2(CO)5 unit in a ?-?N:?2 S mode, and the methane­thiol­ate ligand is coordinated to the Fe2(CO)6 unit in a ?-?2 S fashion.

Shi, Yao-cheng; Lai, Liang; Shen, Wen-bin; Yuan, Li-min

2011-01-01

186

Undeca-carbonyl-?2-methane-thiol-ato-?2-[(pyridin-2-yl)methane-thiol-ato]-?4-sulfido-tetra-iron(II)(2 Fe--Fe)  

Science.gov (United States)

The title compound, [Fe4(C6H6NS)(CH3S)S(CO)11], com­prises two butterfly-shaped sub-cluster cores, Fe2S2N and Fe2S2, joined together by a spiro-type ?4-S atom. The (pyridin-2-yl)methane­thiol­ate ligand is attached to the Fe2(CO)5 unit in a ?-?N:?2 S mode, and the methane­thiol­ate ligand is coordinated to the Fe2(CO)6 unit in a ?-?2 S fashion.

Shi, Yao-Cheng; Lai, Liang; Shen, Wen-Bin; Yuan, Li-Min

2011-01-01

187

Hepatocytes lacking thioredoxin reductase 1 have normal replicative potential during development and regeneration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Cells require ribonucleotide reductase (RNR) activity for DNA replication. In bacteria, electrons can flow from NADPH to RNR by either a thioredoxin-reductase- or a glutathione-reductase-dependent route. Yeast and plants artificially lacking thioredoxin reductases exhibit a slow-growth phenotype, suggesting glutathione-reductase-dependent routes are poor at supporting DNA replication in these organisms. We have studied proliferation of thioredoxin-reductase-1 (Txnrd1)-deficient hepatocytes in...

Rollins, Maryclare F.; Heide, Dana M.; Weisend, Carla M.; Kundert, Jean A.; Comstock, Kristin M.; Suvorova, Elena S.; Capecchi, Mario R.; Merrill, Gary F.; Schmidt, Edward E.

2010-01-01

188

Glutathione-S-Transferase and Thiol Stress in patients with acute renal failure  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction: Tubular damage is common finding in acute renal failure (ARF. Various etiologies have been put forth to explain the tubular damage in ARF, one important mechanism among them is oxidative damage to renal tubules. Several biomolecules including low-molecular weight peptides and enzymes in urine have been proposed as early markers of renal failure. Current study has been undertaken to study the thiol stress and glutathione-S-transferase (GST levels in ARF patients. Method: 58 ARF patients and 55 healthy controls were selected based on inclusion and exclusion criteria. Serum thiols, GST, malanoldehyde (MDA and urine thiols were determined by spectrophotometer based methods. Results: Serum thiols and urine thiols were significantly decreased (p<0.0001, and serum GST and MDA levels were significantly increased (p<0.0001 in ARF patients compared to healthy controls. Serum GST and MDA correlated positively in ARF cases (r2 = 0.6938, p<0.0001. Conclusion: There is significant thiol stress and increased lipid peroxidation in ARF patients which leads to tubular cell membrane damage and release of GST into blood stream and into urine. This may be possible mechanism for the increased presence of GST in urine (enzymuria found in other studies.

Mungli Prakash

2010-07-01

189

The role of the thiol group in protein modification with methylglyoxal  

Directory of Open Access Journals (Sweden)

Full Text Available Methylglyoxal is a highly reactive ?-oxoaldehyde with elevated production in hyperglycemia. It reacts with nucleophilic Lys and Arg side-chains and N-terminal amino groups causing protein modification. In the present study, the importance of the reaction of the Cys thiol group with methylglyoxal in protein modification, the competitiveness of this reaction with those of amino and guanidine groups, the time course of these reactions and their role and contribution to protein cross-linking were investigated. Human and bovine serum albumins were used as model systems. It was found that despite the very low levels of thiol groups on the surface of the examined protein molecules (approx. 80 times lower than those of amino and guanidino groups, a very high percentage of it reacts (25–85 %. The amount of reacted thiol groups and the rate of the reaction, the time for the reaction to reach equilibrium, the formation of a stable product and the contribution of thiol groups to protein cross-linking depend on the methylglyoxal concentration. The product formed in the reaction of thiol and an insufficient quantity of methylglyoxal (compared to the concentrations of the groups accessible for modification participates to a significant extent (4 % to protein cross-linking. Metformin applied in equimolar concentration with methylglyoxal prevents its reaction with amino and guanidino groups but, however, not with thiol groups.

JELENA M. A?IMOVI?

2009-08-01

190

Low molecular weight thiols in arsenic hyperaccumulator Pteris vittata upon exposure to arsenic and other trace elements.  

Science.gov (United States)

Low molecular weight thiol-containing compounds have been reported to play an important role in metal detoxification and accumulation in some higher plants. The formation of these low molecular weight thiols in the recently discovered arsenic hyperaccumulator, Chinese Brake fern (Pteris vittata) upon exposure to arsenic and other trace metals was investigated. In addition to cysteine and glutathione, an unidentified thiol was observed in the plants exposed to arsenic, which was not found in the control. The concentration of the unidentified thiol showed a very strong and positive correlation with arsenic concentration in the leaflets. The unidentified thiol was low in rachises and undetectable in the roots for As-treated plants. Total and acid-soluble thiols were also measured and the results indicated that arsenic mainly stimulated the synthesis of acid-soluble thiol in Chinese Brake. The investigations of other trace elements (Cd, Cu, Cr, Zn, Pb, Hg, and Se) showed that these elements were not accumulated in Chinese Brake to high levels and the synthesis of the unidentified thiol in the plant was not observed. Our study suggests that the unidentified thiol was induced specifically by arsenic and the distribution patterns of the unidentified thiol and arsenic in the plant were consistent, indicating that the synthesis of this compound was related to As exposure. PMID:14749071

Cai, Yong; Su, Jinhui; Ma, Lena Q

2004-05-01

191

Thiol-ene/acrylate substrates for softening intracortical electrodes.  

Science.gov (United States)

Neural interfaces have traditionally been fabricated on rigid and planar substrates, including silicon and engineering thermoplastics. However, the neural tissue with which these devices interact is both 3D and highly compliant. The mechanical mismatch at the biotic-abiotic interface is expected to contribute to the tissue response that limits chronic signal recording and stimulation. In this work, novel ternary thiol-ene/acrylate polymer networks are used to create softening substrates for neural recording electrodes. Thermomechanical properties of the substrates are studied through differential scanning calorimetry and dynamic mechanical analysis both before and after exposure physiological conditions. This substrate system softens from more than 1 GPa to 18 MPa on exposure to physiological conditions: reaching body temperature and taking up less than 3% fluid. The impedance of 177 µm(2) gold electrodes electroplated with platinum black fabricated on these substrates is measured to be 206 k? at 1 kHz. Specifically, intracortical electrodes are fabricated, implanted, and used to record driven neural activity. This work describes the first substrate system that can use the full capabilities of photolithography, respond to physiological conditions by softening markedly after insertion, and record driven neural activity for 4 weeks. PMID:23666562

Ware, Taylor; Simon, Dustin; Liu, Clive; Musa, Tabassum; Vasudevan, Srikanth; Sloan, Andrew; Keefer, Edward W; Rennaker, Robert L; Voit, Walter

2014-01-01

192

Kinetics of ? hydrogen abstractions from thiols, sulfides and thiocarbonyl compounds.  

Science.gov (United States)

Hydrogen abstraction reactions involving organosulfur compounds play an important role in many industrial, biological and atmospheric processes. Despite their chemical relevance, little is known about their kinetics. In this work a group additivity model is developed that allows predicting the Arrhenius parameters for abstraction reactions of ? hydrogen atoms from thiols, alkyl sulfides, alkyl disulfides and thiocarbonyl compounds by carbon-centered radicals at temperatures ranging from 300 to 1500 K. Rate coefficients for 102 hydrogen abstractions were obtained using conventional transition state theory within the high-pressure limit. Electronic barriers were calculated using the CBS-QB3 method and the rate coefficients were corrected for tunneling and hindered rotation about the transitional bond. Group additivity values for 46 groups are determined. To account for resonance and hyperconjugative stabilization in the transition state, 8 resonance corrections were fitted to a set of 32 reactions. The developed group additivity scheme was validated using a test set containing an additional 30 reactions. The group additivity scheme succeeds in reproducing the rate coefficients on average within a factor of 2.4 at 300 K and 1.4 at 1000 K. Mean absolute deviations of the Arrhenius parameters amount to, respectively, 2.5 kJ mol(-1) for E(a) and 0.13 for log A, both at 300 and 1000 K. This work hence illustrates that the recently developed group additivity methods for Arrhenius parameters extrapolate successfully to hetero-element containing compounds. PMID:22854881

Vandeputte, Aäron G; Sabbe, Maarten K; Reyniers, Marie-Françoise; Marin, Guy B

2012-10-01

193

Processing and targeting of the thiol protease aleurain: Progress report  

Energy Technology Data Exchange (ETDEWEB)

This study addresses the processing and targeting of the thiol protease aleurain in monocots. A probe derived from the aleurain cDNA specific for the 5'-most 400 bp (a region encoding the first 140 amino acids of the preprotein hybridized to at least 3 separate elements in the barley genome; only one represented the aleurain gene. In contrast, a probe specific for the remaining 2/23 of the cDNA (representing the protease domain) hybridized to only a single copy sequence. To know if this pattern pertained in other, closely related, monocots, we probed Southern blots of genomic DNA from maize, rye, oats, sorghum, and pearl millet with each probe. In each instance except for maize DNA, the 5' domain probe hybridizes to several fragments in addition to those identified by the protease domain probe. Presumable the darkest hybridization in each represents the fragment carrying the sequences homologous to barley aleurain. The fragments from a given restriction enzyme identified by the protease domain probe in sorghum, millet, and maize, were indistinguishable in size indicating that the gene sequences, as well as flanking DNA, are so well conserved among the group that the location of the hexanucleotide sequences have not diverged. (3 refs., 3 figs.)

Rogers, J.C.

1988-01-01

194

Processing and targeting of the thiol protease, aleurain  

Energy Technology Data Exchange (ETDEWEB)

We have identified a cDNA clone from barley aleurone mRNA that encodes a protein with unusual homologies: the C-terminal portion, about 270 amino acids, is 65% identical to the mammalian thiol protease, cathepsin H. This degree of sequence conservation indicates that the enzyme must have some specific function in both plants and mammals that cannot tolerate further divergence. The N-terminal 1/3 of the protein, about 140 amino acids, has no detectable homologies to other known protein sequences; its function is unknown. In aleurone tissue, the mRNA level is increased by gibberellic acid and decreased by abscisic acid, but is expressed apparently constitutively at high levels in leaf and root tissues. The amino acid sequence and cathepsin H homology suggest that the protein will be both secreted into the endoplasmic reticulum and glycosylated. Using our cDNA clone in a bacterial expression system, we have made a fusion protein containing the protease domain of aleurain, and have used it to raise specific antisera in rabbits. These antibodies identify a 32 kd protein in extracts of aleurone layers that is induced with GA treatment but not secreted; a similarly sized protein is specifically identified in extracts of leaf tissue. Experiments are underway to characterize the pattern of expression in different tissues, to identify the subcellular locations of the protein, to characterize processing of the precursor to the 32 kd mature form, and to purify the enzyme from barley. 2 figs.

Rogers, J.C.

1989-01-01

195

(Processing and targeting of the thiol protease aleurain)  

Energy Technology Data Exchange (ETDEWEB)

Our goal for work during the past two years under this Grant was to characterize the barley thiol protease, aleurain, to determine if it is secreted or retained intracellularly in aleurone cells, and to begin to elucidate structural features that might control targeting of the protein to its final destination. We have shown that aleurain is synthesized as a proenzyme with two N-linked oligosaccharide chains, one high mannose-type and one complex-type. Aleurain undergoes processing to mature form by removal of an Nterminal prosegment, and is retained intracellularly; it cannot be detected among proteins secreted from aleurone cells. Treatment of aleurone cells with tunicamycin to prevent glycosylation of aleurain does not prevent processing of the unglycosylated form. The N-terminal portion of aleurain's prosegment is homologous to the comparable region in two yeast vacuolar proteases, where that region is known to contain the signal necessary for targeting the proteases to the vacuole. 18 refs., 7 figs.

Rogers, J.C.

1990-01-01

196

A chromogenic assay of substrate depletion by thiol dioxygenases.  

Science.gov (United States)

A fast and easy method for enzyme activity assays using the chromogenic Ellman reagent, 5,5'-dithiobis(2-nitrobenzoic acid), was developed. The method was used to measure the activity of the nonheme mono-iron enzyme cysteine dioxygenase. Quantifying the depletion of the substrate, cysteine, allowed standard kinetic parameters to be determined for the enzyme from Rattus norvegicus. The assay was also used to quickly test the effects of ionic strength, pH, enzyme storage conditions, and potential inhibitors and activators. This assay facilitates a higher throughput than available HPLC-based assays, as it enjoys the advantages of fewer sample handling steps, implementation in a 96-well format, and speed. In addition, the relative specificity of Ellman's reagent, coupled with its reaction with a wide range of thiols, means that this assay is applicable to many enzymes. Finally, the use of readily available reagents and instrumentation means that this assay can be used by practically any research group to compare results with those of other groups. PMID:24857787

Fellner, Matthias; Doughty, Laura M; Jameson, Guy N L; Wilbanks, Sigurd M

2014-08-15

197

Adsorption kinetic process of thiol ligands on gold nanocrystals  

Science.gov (United States)

Understanding the kinetic mechanism during ligand adsorption on gold nanocrystals is important for designing and fine-tuning their properties and implications. Here, we report a kinetic study on the adsorption process of dodecanethiol ligands on Au nanocrystals of 3.3 nm by an in situ time-resolved X-ray absorption fine structure technique. A two-step process of dodecanethiol adsorption on Au NC surfaces is proposed based on the obtained ligand coverage, which shows a quick increase from 0 to 0.40 within the first 20 min, followed by a much slower increase to the limiting value of 0.94. In-depth analysis suggests that the first stage involves the quick adsorption of dodecanethiol to the corner and edge sites of Au NCs surfaces, leading to remarkable surface Au-Au bond length relaxation (from 2.79 to 2.81 Å) and pronounced gold-to-ligand charge transfer. The second step that corresponds to the much slower adsorption process to the surface facets could be described by the Langmuir kinetics equation with an adsorption rate constant of 0.0132 min-1 and an initial coverage of 0.41, in good agreement with the initially preferable adsorption of thiols to the most favorable sites.

Cheng†, Hao; Yang†, Lina; Jiang, Yong; Huang, Yuanyuan; Sun, Zhihu; Zhang, Jing; Hu, Tiandou; Pan, Zhiyun; Pan, Guoqiang; Yao, Tao; Bian, Qing; Wei, Shiqiang

2013-11-01

198

Selenium and the Methionine Sulfoxide Reductase System  

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Selenium is a chemical element participating in the synthesis of selenocysteine residues that play a pivotal role in the enzymatic activity efficiency of selenoproteines. The methionine sulfoxide reductase (Msr) system that reduces methionine sulfoxide (MetO) to methionine comprises the selenoprotein MsrB (MsrB1) and the non-selenoprotein MsrA, which reduce the R- and the S- forms of MetO, respectively. The effects of a selenium deficient (SD) diet, which was administrated to wild type (WT) a...

Oien, Derek B.; Jackob Moskovitz

2009-01-01

199

A functional nitric oxide reductase model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A functional heme/nonheme nitric oxide reductase (NOR) model is presented. The fully reduced diiron compound reacts with two equivalents of NO leading to the formation of one equivalent of N2O and the bis-ferric product. NO binds to both heme Fe and nonheme Fe complexes forming individual ferrous nitrosyl species. The mixed-valence species with an oxidized heme and a reduced nonheme FeB does not show NO reduction activity. These results are consistent with a so-called “trans” mechanism fo...

Collman, James P.; Yang, Ying; Dey, Abhishek; Decre?au, Richard A.; Ghosh, Somdatta; Ohta, Takehiro; Solomon, Edward I.

2008-01-01

200

Analogue reaction systems of selenate reductase.  

Science.gov (United States)

Analogue reaction systems of selenate reductase, which reduces substrate in the overall enzymatic reaction SeO4(2-) + 2H+ + 2e- --> SeO3(2-) + H2O, have been developed using bis(dithiolene) complexes of Mo(IV) and W(IV). On the basis of the results of EXAFS analysis of the oxidized and reduced enzyme, the minimal reaction Mo(IV)OH + SeO4(2-) --> Mo(VI)O(OH) + SeO3(2-) is probable. The square pyramidal complexes [M(OMe)(S2C2Me2)2](1-) (M = Mo, W) were prepared as structural analogues of the reduced enzyme site. The systems, [ML(S2C2Me2)2](1-)/SeO4(2-) (L = OMe, OPh, SC6H2-2,4,6-Pr(i)3) in acetonitrile, cleanly reduce selenate to selenite in second-order reactions whose negative entropies of activation implicate associative transition states. Rate constants at 298 K are in the 10(-2)-10(-4) M(-1) s(-1) range with DeltaS++ = -12 to -34 eu. When rate constants are compared with previous data for the reduction of (CH2)4SO, Ph3AsO, and nitrate by oxygen atom transfer, reactivity trends dependent on the metal, axial ligand L, and substrate are identified. As in all other cases of substrate reduction by oxo transfer, the kinetic metal effect k(2)W > k(2)Mo holds. A proposal from primary sequence alignments suggesting that a conserved Asp residue is a likely ligand in the type II enzymes in the DMSO reductase family has been pursued by synthesis of the [Mo(IV)(O2CR)(S2C2Me2)2](1-) (R = Ph, Bu(t)) complexes. The species display symmetrical eta2-carboxylate binding and distorted trigonal prismatic stereochemistry. They serve as possible structural analogues of the reduced sites of nitrate, selenate, and perchlorate reductases under the proposed aspartate coordination. Carboxylate binding has been crystallographically demonstrated for one nitrate reductase, but not for the other two enzymes. PMID:16562954

Wang, Jun-Jieh; Tessier, Christian; Holm, R H

2006-04-01

 
 
 
 
201

Influence of growth conditions on glycine reductase of Clostridium sporogenes.  

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Cells of Clostridium sporogenes were deficient in glycine reductase activity when grown in a rich medium containing 40 mM each of exogenously added pyruvate and proline or hydroxyproline. These cells lacked the selenoprotein and at least one more protein of the glycine reductase system. Proline or hydroxyproline in the medium also influenced the uptake of glycine by the cells.

Venugopalan, V.

1980-01-01

202

SORGOdb: Superoxide Reductase Gene Ontology curated DataBase  

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Abstract Background Superoxide reductases (SOR) catalyse the reduction of superoxide anions to hydrogen peroxide and are involved in the oxidative stress defences of anaerobic and facultative anaerobic organisms. Genes encoding SOR were discovered recently and suffer from annotation problems. These genes, named sor, are short and the transfer of annotations from previously characterized neelaredoxin, desulfoferrodoxin, superoxide reductase and rubredoxin oxidase has ...

Lucchetti-Miganeh Céline; Goudenège David; Thybert David; Salbert Gilles; Barloy-Hubler Frédérique

2011-01-01

203

Biochemical characterization of thioredoxin reductase from Babesia bovis.  

Science.gov (United States)

This paper addresses the identification, cloning, expression, purification and functional characterization of thioredoxin reductase from Babesia bovis, the etiological agent of babesiosis. The work deals with in vitro steady state kinetic studies and other complementary analyses of the thioredoxin reductase found in the pathogenic protist. Thioredoxin reductase from B. bovis was characterized as a homodimeric flavoprotein that catalyzes the NADPH-dependent reduction of Trx with a high catalytic efficiency. Moreover, the enzyme exhibited a disulfide reductase activity using DTNB as substrate, being this activity highly sensitive to inhibition by Eosin B. The thioredoxin reductase/thioredoxin system can reduce oxidized glutathione and S-nitrosoglutathione. Our in vitro data suggest that antioxidant defense in B. bovis could be supported by this enzyme. We have performed an enzymatic characterization, searching for targets for rational design of inhibitors. This work contributes to the better understanding of the redox biochemistry occurring in the parasite. PMID:24239559

Regner, Erika L; Thompson, Carolina S; Iglesias, Alberto A; Guerrero, Sergio A; Arias, Diego G

2014-04-01

204

Purification and Characterization of NAD(P)H:Nitrate Reductase and NADH:Nitrate Reductase from Corn Roots.  

Science.gov (United States)

The nitrate reductase activity of 5-day-old whole corn roots was isolated using phosphate buffer. The relatively stable nitrate reductase extract can be separated into three fractions using affinity chromatography on blue-Sepharose. The first fraction, eluted with NADPH, reduces nearly equal amounts of nitrate with either NADPH or NADH. A subsequent elution with NADH yields a nitrate reductase which is more active with NADH as electron donor. Further elution with salt gives a nitrate reductase fraction which is active with both NADH and NADPH, but is more active with NADH. All three nitrate reductase fractions have pH optima of 7.5 and Stokes radii of about 6.0 nanometers. The NADPH-eluted enzyme has a nitrate K(m) of 0.3 millimolar in the presence of NADPH, whereas the NADH-eluted enzyme has a nitrate K(m) of 0.07 millimolar in the presence of NADH. The NADPH-eluted fraction appears to be similar to the NAD(P)H:nitrate reductase isolated from corn scutellum and the NADH-eluted fraction is similar to the NADH:nitrate reductases isolated from corn leaf and scutellum. The salt-eluted fraction appears to be a mixture of NAD(P)H: and NADH:nitrate reductases. PMID:16661853

Redinbaugh, M G; Campbell, W H

1981-07-01

205

Overexpression of Thiol/Disulfide Isomerases Enhances Membrane Fusion Directed by the Newcastle Disease Virus Fusion Protein?  

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Newcastle disease virus (NDV) fusion (F) protein directs membrane fusion, which is required for virus entry and cell-cell fusion. We have previously shown that free thiols are present in cell surface-expressed NDV F protein and that blocking the production of free thiols by thiol-disulfide exchange inhibitors inhibited the membrane fusion mediated by F protein (J Virol. 81:2328-2339, 2007). Extending these observations, we evaluated the role of the overexpression of two disulfide bond isomera...

2008-01-01

206

RAPID PERMANENT HYDROPHILIC AND HYDROPHOBIC PATTERNING OF POLYMER SURFACES VIA OFF-STOICHIOMETRY THIOL-ENE (OSTE) PHOTOGRAFTING  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work we have developed a simple and robust method to permanently pattern alternating hydrophobic and hydrophilic surfaces in off-stoichiometry thiol-ene (OSTE) polymer microchannels. By being able to tune the number of unreacted thiol surface groups of the OSTE Thiol polymers and by taking advantage of spatially photo-controlled surface grafting of methacrylate monomers we achieve defined areas with contact angles from 20° to 115° within one single channel. The surface modification ...

Carlborg, Fredrik; Moraga, Francesca; Saharil, Farizah; Wijngaart, Wouter; Haraldsson, Tommy

2012-01-01

207

Electrochemistry behavior of endogenous thiols on fluorine doped tin oxide electrodes  

International Nuclear Information System (INIS)

Highlights: ? The first time that fluorine doped tin oxide electrodes are used for the electrooxidation of endogenous thiols. ? Low potentials of electrooxidation were obtained for the different thiols. ? The electrochemical behavior of thiols depends on the pH and the ionic electroactive species, the electrooxidation proceeds for a process of adsorption of electroactive species on FTO and high values the heterogeneous electron tranfer rate constant of the reaction were obtained. - Abstract: In this work the electrochemical behavior of different thiols on fluorine doped tin oxide (FTO) electrodes is reported. To this end, the mechanism of electrochemical oxidation of glutathione (GSH), cysteine (Cys), homocysteine (HCys) and acetyl-cysteine (ACys) at different pH was investigated. FTO showed electroactivity for the oxidation of the first three thiols at pH between 2.0 and 4.0, but under these conditions no acetyl-cysteine oxidation was observed on FTO. Voltammetric studies of the electro-oxidation of GSH, Cys and HCys showed peaks at about 0.35, 0.29, and 0.28 V at optimum pH 2.4, 2.8 and 3.4, respectively. In addition, this study demonstrated that GSH, Cys and HCys oxidation occurs when the zwitterion is the electro-active species that interact by adsorption on FTO electrodes. The overall reaction involves 4e-/4H+ and 2e-/2H+, respectively, for HCys and for GSH and Cys and high heterogeneous electron transfer rate constants. Besides, the use of FTO for the determination of different thiols was evaluated. Experimental square wave voltammetry shows a linear current vs. concentrations response between 0.1 and 1.0 mM was found for HCys and GSH, indicating that these FTO electrodes are promising candidates for the efficient electrochemical determination of these endogenous thiols.

2011-10-01

208

Quantum-chemical predictions of pKa's of thiols in DMSO.  

Science.gov (United States)

The deprotonation of thiols (on the S-H bond) is widely involved in organic and bio-organic reactions. With the aid of density functional theory (DFT) calculations, the present study focuses on predicting the pKa's of thiols. Efforts were first put in searching for an appropriate computational method. To achieve this goal, the accuracy of 13 different DFT functionals (i.e., B3LYP, BB1K, PBE, M06, M05, M06-2X, M06-L, M05-2X, TPSS, MPW1K, MPWB1K, MPW3LYP, TPSSLYP1W) and 6 different total electron basis sets (6-31G(d), 6-31+G(d), 6-31+G(d,p), 6-311+G(d,p), 6-311++G(d,p), 6-311++G(2df,2p)) (with DMSO solvent and SMD solvation model) were examined. The M06-2X/6-311++G(2df,2p) (M1) method was found to give the best performance in reproducing the reported 16 pKa's of thiols, with a standard deviation (SD) of about 0.5 pKa unit. Meanwhile, the M1 method was found to be excellent in reproducing the gas phase Gibbs free energies of 17 thiols, providing extra evidence for the reliability of the M1 method in treating thiol systems. On this basis, M1 was then used to predict the pKa's of 291 thiols whose experimental pKa values remain unknown. Accordingly, the scope of pKa's of different thiols was constructed. PMID:24387165

Yu, Hai-Zhu; Yang, Yi-Meng; Zhang, Liang; Dang, Zhi-Min; Hu, Guo-Hua

2014-01-23

209

Thiol involvement in the inhibition of DNA repair by metals in mammalian cells  

International Nuclear Information System (INIS)

We have previously demonstrated that a number of metal salts have the capacity to inhibit the DNA repair process in human cells. We investigated repair of X-ray damage in metal-treated HeLa cells under normal conditions and conditions in which cellular thiols had been depleted by treatment with buthionine sulfoximine (BSO) and diethyl maleate (DEM). The combination reduced cellular TNPT by 92%, and cells so depleted became sensitized to X-ray-induced killing and exhibited retarded sealing of X-ray-induced DNA single-strand breaks. Thiol depletion also sensitized cells to the cytotoxicity of certain but not all metals tested. The sensitivity to copper was increased over 6000-fold, and significant enhancement of killing was also seen in cells treated with arsenic, lead, and mercury. Smaller effects were observed with cadmium and nickel, and sensitivity to manganese, magnesium, cobalt or zinc was not substantially altered. Enhanced sensitivity to X-ray killing was found in cells treated with nickel, cadmium, zinc, arsenic, and copper under conditions in which thiols were not limiting. In thiol-depleted cells, sensitivity was not further increased in the case of nickel and arsenic but at least additively affected for copper, mercury and zinc. X-Ray-induced single-strand break repair was retarded by treatment of cells with mercury, nickel, zinc, arsenic, and copper in thiol-normal cells. In thiol-depleted cells, repair inhibition by zinc, arsenic, and copper was nearly complete, while little additional effect on repair was seen following mercury and nickel treatment. An examination of the effects of brief metal treatment on cellular TNPT revealed that copper strongly decreased thiol levels whereas the other metals tested either had no effect on TNPT or reduced TNPT levels to no less than 48% under the conditions employed

1989-01-01

210

Electrochemistry behavior of endogenous thiols on fluorine doped tin oxide electrodes  

Energy Technology Data Exchange (ETDEWEB)

Highlights: > The first time that fluorine doped tin oxide electrodes are used for the electrooxidation of endogenous thiols. > Low potentials of electrooxidation were obtained for the different thiols. > The electrochemical behavior of thiols depends on the pH and the ionic electroactive species, the electrooxidation proceeds for a process of adsorption of electroactive species on FTO and high values the heterogeneous electron tranfer rate constant of the reaction were obtained. - Abstract: In this work the electrochemical behavior of different thiols on fluorine doped tin oxide (FTO) electrodes is reported. To this end, the mechanism of electrochemical oxidation of glutathione (GSH), cysteine (Cys), homocysteine (HCys) and acetyl-cysteine (ACys) at different pH was investigated. FTO showed electroactivity for the oxidation of the first three thiols at pH between 2.0 and 4.0, but under these conditions no acetyl-cysteine oxidation was observed on FTO. Voltammetric studies of the electro-oxidation of GSH, Cys and HCys showed peaks at about 0.35, 0.29, and 0.28 V at optimum pH 2.4, 2.8 and 3.4, respectively. In addition, this study demonstrated that GSH, Cys and HCys oxidation occurs when the zwitterion is the electro-active species that interact by adsorption on FTO electrodes. The overall reaction involves 4e{sup -}/4H{sup +} and 2e{sup -}/2H{sup +}, respectively, for HCys and for GSH and Cys and high heterogeneous electron transfer rate constants. Besides, the use of FTO for the determination of different thiols was evaluated. Experimental square wave voltammetry shows a linear current vs. concentrations response between 0.1 and 1.0 mM was found for HCys and GSH, indicating that these FTO electrodes are promising candidates for the efficient electrochemical determination of these endogenous thiols.

Rojas, Luciana; Molero, Leonard; Tapia, Ricardo A.; Rio, Rodrigo del; Valle, M. Angelica del; Antilen, Monica [Departamento de Quimica Inorganica, Facultad de Quimica, Pontificia Universidad Catolica de Chile, Av Vicuna Mackenna 4860, Casilla 306, Correo 22, Macul, Santiago (Chile); Armijo, Francisco, E-mail: jarmijom@uc.cl [Departamento de Quimica Inorganica, Facultad de Quimica, Pontificia Universidad Catolica de Chile, Av Vicuna Mackenna 4860, Casilla 306, Correo 22, Macul, Santiago (Chile)

2011-10-01

211

Molecular modeling of the reductase domain to elucidate the reaction mechanism of reduction of peptidyl thioester into its corresponding alcohol in non-ribosomal peptide synthetases  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Nonribosomal peptide synthetases (NRPSs are multienzymatic, multidomain megasynthases involved in the biosynthesis of pharmaceutically important nonribosomal peptides. The peptaibol synthetase from Trichoderma virens (TPS is an important member of the NRPS family that exhibits antifungal properties. The majority of the NRPSs terminate peptide synthesis with the thioesterase (TE domain, which either hydrolyzes the thioester linkage, releasing the free peptic acid, or catalyzes the intramolecular macrocyclization to produce a macrolactone product. TPS is an important NRPS that does not encompass a TE domain, but rather a reductase domain (R domain to release the mature peptide product reductively with the aid of a NADPH cofactor. However, the catalytic mechanism of the reductase domain has not yet been elucidated. Results We present here a three-dimensional (3D model of the reductase domain based on the crystal structure of vestitone reductase (VR. VR belongs to the short-chain dehydrogenase/reductase (SDR superfamily and is responsible for the nicotinamide dinucleotide phosphate (NADPH-dependent reduction of the substrate into its corresponding secondary alcohol product. The binding sites of the probable linear substrates, alamethicin, trichotoxin, antiamoebin I, chrysopermin C and gramicidin, were identified within the modeled R domain using multiple docking approaches. The docking results of the ligand in the active site of the R domain showed that reductase side chains have a high affinity towards ligand binding, while the thioester oxygen of each substrate forms a hydrogen bond with the OH group of Tyr176 and the thiol group of the substrate is closer to the Glu220. The modeling and docking studies revealed the reaction mechanism of reduction of thioester into a primary alcohol. Conclusion Peptaibol biosynthesis incorporates a single R domain, which appears to catalyze the four-electron reduction reaction of a peptidyl carrier protein (PCP-bound peptide to its corresponding primary alcohol. Analysis of R domains present in the non-redundant (nr database of the NCBI showed that the R domain always resides in the last NRPS module and is involved in either a two or four-electron reduction reaction.

Lee Gwang

2010-01-01

212

Visible light cured thiol-vinyl hydrogels with tunable degradation for 3D cell culture.  

Science.gov (United States)

We report here a synthetically simple yet highly tunable and diverse visible light mediated thiol-vinyl gelation system for fabricating cell-instructive hydrogels. Gelation was achieved via a mixed-mode step-and-chain-growth photopolymerization using functionalized 4-arm poly(ethylene glycol) as backbone macromer, eosin-Y as photosensitizer, and di-thiol containing molecule as dual purpose co-initiator/cross-linker. N-vinylpyrrolidone (NVP) was used to accelerate gelation kinetics and to adjust the stiffness of the hydrogels. Visible light (wavelength: 400-700 nm) was used to initiate rapid gelation (gel points: ~20s) that reached completion within a few minutes. The major differences between current thiol-vinyl gelation and prior visible light mediated photopolymerization are that: (1) the co-initiator triethanolamine (TEA) used in the previous systems was replaced with multifunctional thiols and (2) mixed-mode polymerized gels contain less network heterogeneity. The gelation kinetics and gel properties at the same PEG macromer concentration could be tuned by changing the identity of vinyl groups and di-thiol cross-linkers, as well as concentration of cross-linker and NVP. Specifically, acrylate-modified PEG afforded the fastest gelation rate, followed by acrylamide and methacrylate-functionalized PEG. Increasing NVP concentration also accelerated gelation and led to a higher network cross-linking density. Further, increasing di-thiol peptide concentration in the gel formulation increased hydrogel swelling and decreased gel stiffness. Due to the formation of thiol-ether-ester bonds following thiol-acrylate reaction, the gels degraded hydrolytically following a pseudo first order degradation kinetics. Degradation rate was controlled by adjusting thiol or NVP content in the polymer precursor solution. The cytocompatibility and utility of this hydrogel system were evaluated using in situ encapsulation of human mesenchymal stem cells (hMSC). Encapsulated hMSCs remained alive (>90%) throughout the duration of the study and the cells were differentiated down osteogenic lineage with varying degrees by controlling the rate and mode of gel degradation. PMID:24021231

Hao, Yiting; Shih, Han; Mu?oz, Zachary; Kemp, Arika; Lin, Chien-Chi

2014-01-01

213

Thiol synthetases of legumes: immunogold localization and differential gene regulation by phytohormones.  

Science.gov (United States)

In plants and other organisms, glutathione (GSH) biosynthesis is catalysed sequentially by ?-glutamylcysteine synthetase (?ECS) and glutathione synthetase (GSHS). In legumes, homoglutathione (hGSH) can replace GSH and is synthesized by ?ECS and a specific homoglutathione synthetase (hGSHS). The subcellular localization of the enzymes was examined by electron microscopy in several legumes and gene expression was analysed in Lotus japonicus plants treated for 1-48 h with 50 ?M of hormones. Immunogold localization studies revealed that ?ECS is confined to chloroplasts and plastids, whereas hGSHS is also in the cytosol. Addition of hormones caused differential expression of thiol synthetases in roots. After 24-48 h, abscisic and salicylic acids downregulated GSHS whereas jasmonic acid upregulated it. Cytokinins and polyamines activated GSHS but not ?ECS or hGSHS. Jasmonic acid elicited a coordinated response of the three genes and auxin induced both hGSHS expression and activity. Results show that the thiol biosynthetic pathway is compartmentalized in legumes. Moreover, the similar response profiles of the GSH and hGSH contents in roots of non-nodulated and nodulated plants to the various hormonal treatments indicate that thiol homeostasis is independent of the nitrogen source of the plants. The differential regulation of the three mRNA levels, hGSHS activity, and thiol contents by hormones indicates a fine control of thiol biosynthesis at multiple levels and strongly suggests that GSH and hGSH play distinct roles in plant development and stress responses. PMID:22442424

Clemente, Maria R; Bustos-Sanmamed, Pilar; Loscos, Jorge; James, Euan K; Pérez-Rontomé, Carmen; Navascués, Joaquín; Gay, Marina; Becana, Manuel

2012-06-01

214

Glutathione revisited: a vital function in iron metabolism and ancillary role in thiol-redox control.  

Science.gov (United States)

Glutathione contributes to thiol-redox control and to extra-mitochondrial iron-sulphur cluster (ISC) maturation. To determine the physiological importance of these functions and sort out those that account for the GSH requirement for viability, we performed a comprehensive analysis of yeast cells depleted of or containing toxic levels of GSH. Both conditions triggered an intense iron starvation-like response and impaired the activity of extra-mitochondrial ISC enzymes but did not impact thiol-redox maintenance, except for high glutathione levels that altered oxidative protein folding in the endoplasmic reticulum. While iron partially rescued the ISC maturation and growth defects of GSH-depleted cells, genetic experiments indicated that unlike thioredoxin, glutathione could not support by itself the thiol-redox duties of the cell. We propose that glutathione is essential by its requirement in ISC assembly, but only serves as a thioredoxin backup in cytosolic thiol-redox maintenance. Glutathione-high physiological levels are thus meant to insulate its cytosolic function in iron metabolism from variations of its concentration during redox stresses, a model challenging the traditional view of it as prime actor in thiol-redox control. PMID:21478822

Kumar, Chitranshu; Igbaria, Aeid; D'Autreaux, Benoît; Planson, Anne-Gaëlle; Junot, Christophe; Godat, Emmanuel; Bachhawat, Anand K; Delaunay-Moisan, Agnès; Toledano, Michel B

2011-05-18

215

The synthesis of novel hybrid thiol-functionalized nano-structured SBA-15  

International Nuclear Information System (INIS)

Mesoporous thiol-functionalized SBA-15 has been directly synthesized by co-condensation of tetraethyl orthosilicate (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) with triblock copolymer P123 as-structure-directing agent under hydrothermal conditions. Surfactant removal was performed by Soxhlet ethanol extraction. These materials have been characterized by powder x-ray diffraction (XRD), nitrogen adsorption/desorption (BET model), transmission electron microscopy (TEM), thermal analysis, infrared spectroscopy (IR) and energy-dispersive x-ray spectroscopy (EDX). The main parameters, such as the initial molar ratio of MPTMS to TEOS, the time of adding MPTMS to synthesized gel and the Soxhlet ethanol extraction on the thiol functionalized SBA-15 with high thiol content and highly ordered hexagonal mesostructure, were investigated and evaluated. The adsorption capacity of the thiol-functionalized and non-functionalized SBA-15 materials for Pb2+ ion from aqueous solution was tested. It was found that the Pb2+ adsorption capacity of the thiol functionalized SBA-15 is three times higher than that of non-functionalized SBA-15

2010-09-01

216

Influence of thiol stress on oxidative phosphorylation and generation of ROS in Streptomyces coelicolor  

Directory of Open Access Journals (Sweden)

Full Text Available Thiols play very important role in the intracellular redox homeostasis. Imbalance in the redox status leads to changes in the intracellular metabolism including respiration. Thiol stress, a reductive type of stress can also cause redox imbalance. When Gram-positive bacterium Strep- tomyces coelicolor was exposed to thiol stress, catalaseA was induced. Induction of catalaseA is the consequence of elevation of ROS (reactive oxygen species. The two major sources of reactive oxygen species are Fenton reaction and slippage of electrons from electron transport chain during respiration. Hence, the effect of thiol stress was checked on the rate of oxidative phosphorylation in S. coelicolor. We found correlation in the increase of oxidative phosphorylation rate and the generation of ROS, subsequently leading to induction of catalase. It was observed that thiol stress does not affect the functionality of the individual complexes of the ETC, but still there was an increase in the overall respiration, which may lead to generation of more ROS leading to induction of catalase.

Hemendra J. Vekaria

2010-11-01

217

Near-Edge X-Ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol Monolayers on Gold  

Energy Technology Data Exchange (ETDEWEB)

Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 {+-} 0.05 and 0.16 {+-} 0.04 eV, respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different degrees of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond nanoparticles.

Willey, T.M.; Fabbri, J.D.; Lee, J.R.I.; Schreiner, P.R.; Fokin, A.A.; Tkachenko, B.A.; Fokina, N.A.; Dahl, J.E.P.; Carlson, R.M.K.; Vance, A.L.; Yang, W.; Terminello, L.J.; Buuren, T.van; Melosh, N.A.

2009-05-26

218

Near-edge X-ray absorption fine structure spectroscopy of diamondoid thiol monolayers on gold.  

Science.gov (United States)

Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 +/- 0.05 and 0.16 +/- 0.04 eV, respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different degrees of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond nanoparticles. PMID:18642809

Willey, Trevor M; Fabbri, Jason D; Lee, Jonathan R I; Schreiner, Peter R; Fokin, Andrey A; Tkachenko, Boryslav A; Fokina, Nataliya A; Dahl, Jeremy E P; Carlson, Robert M K; Vance, Andrew L; Yang, Wanli; Terminello, Louis J; van Buuren, Tony; Melosh, Nicolas A

2008-08-13

219

Near-Edge X-ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol Monolayers on Gold  

Energy Technology Data Exchange (ETDEWEB)

Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface-modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 {+-} 0.05 eV and 0.16 {+-} 0.04 eV respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different amounts of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond clusters.

Willey, T M; Fabbri, J; Lee, J I; Schreiner, P; Fokin, A A; Tkachenko, B A; Fokina, N A; Dahl, J; Carlson, B; Vance, A L; Yang, W; Terminello, L J; van Buuren, T; Melosh, N

2007-11-27

220

Mitochondrial respiratory chain complexes as sources and targets of thiol-based redox-regulation.  

Science.gov (United States)

The respiratory chain of the inner mitochondrial membrane is a unique assembly of protein complexes that transfers the electrons of reducing equivalents extracted from foodstuff to molecular oxygen to generate a proton-motive force as the primary energy source for cellular ATP-synthesis. Recent evidence indicates that redox reactions are also involved in regulating mitochondrial function via redox-modification of specific cysteine-thiol groups in subunits of respiratory chain complexes. Vice versa the generation of reactive oxygen species (ROS) by respiratory chain complexes may have an impact on the mitochondrial redox balance through reversible and irreversible thiol-modification of specific target proteins involved in redox signaling, but also pathophysiological processes. Recent evidence indicates that thiol-based redox regulation of the respiratory chain activity and especially S-nitrosylation of complex I could be a strategy to prevent elevated ROS production, oxidative damage and tissue necrosis during ischemia-reperfusion injury. This review focuses on the thiol-based redox processes involving the respiratory chain as a source as well as a target, including a general overview on mitochondria as highly compartmentalized redox organelles and on methods to investigate the redox state of mitochondrial proteins. This article is part of a Special Issue entitled: Thiol-Based Redox Processes. PMID:24561273

Dröse, Stefan; Brandt, Ulrich; Wittig, Ilka

2014-08-01

 
 
 
 
221

Radiosensitization by misonidazole during recovery of cellular thiols following depletion by BSO or DEM  

International Nuclear Information System (INIS)

V79 cells have been depleted of their endogenous thiols by treatment with 100 microM BSO for 16-18 hr, or 0.5 mM DEM for 1 hr. The recovery of cellular thiols after removal of the drugs was determined by h.p.l.c. or flow cytometry and the sensitizer enhancement ratio for 100 microM misonidazole was measured as a function of time after removal of the drugs. The SER of 1.2 for control (hypoxic) cells increased to 1.8 for BSO treated (hypoxic) cells and 2.2 for DEM treated ones, when thiol levels were below 10% of controls. The SER and thiol levels returned to control values within 5 hr of removing DEM. After BSO there was little change during the first 5 hr and then a gradual return to normal values by 24 hrs. The major fall in the SER after removal of the drugs occurred as the cellular thiols increased to 60% of control values

1989-01-01

222

A Central Role for Thiols in Plant Tolerance to Abiotic Stress  

Directory of Open Access Journals (Sweden)

Full Text Available Abiotic stress poses major problems to agriculture and increasing efforts are being made to understand plant stress response and tolerance mechanisms and to develop new tools that underpin successful agriculture. However, the molecular mechanisms of plant stress tolerance are not fully understood, and the data available is incomplete and sometimes contradictory. Here, we review the significance of protein and non-protein thiol compounds in relation to plant tolerance of abiotic stress. First, the roles of the amino acids cysteine and methionine, are discussed, followed by an extensive discussion of the low-molecular-weight tripeptide, thiol glutathione, which plays a central part in plant stress response and oxidative signalling and of glutathione-related enzymes, including those involved in the biosynthesis of non-protein thiol compounds. Special attention is given to the glutathione redox state, to phytochelatins and to the role of glutathione in the regulation of the cell cycle. The protein thiol section focuses on glutaredoxins and thioredoxins, proteins with oxidoreductase activity, which are involved in protein glutathionylation. The review concludes with a brief overview of and future perspectives for the involvement of plant thiols in abiotic stress tolerance.

Lyuben Zagorchev

2013-04-01

223

Ribonucleotide reductases: essential enzymes for bacterial life  

Science.gov (United States)

Ribonucleotide reductase (RNR) is a key enzyme that mediates the synthesis of deoxyribonucleotides, the DNA precursors, for DNA synthesis in every living cell. This enzyme converts ribonucleotides to deoxyribonucleotides, the building blocks for DNA replication, and repair. Clearly, RNR enzymes have contributed to the appearance of genetic material that exists today, being essential for the evolution of all organisms on Earth. The strict control of RNR activity and dNTP pool sizes is important, as pool imbalances increase mutation rates, replication anomalies, and genome instability. Thus, RNR activity should be finely regulated allosterically and at the transcriptional level. In this review we examine the distribution, the evolution, and the genetic regulation of bacterial RNRs. Moreover, this enzyme can be considered an ideal target for anti-proliferative compounds designed to inhibit cell replication in eukaryotic cells (cancer cells), parasites, viruses, and bacteria.

Torrents, Eduard

2014-01-01

224

Selenium and the Methionine Sulfoxide Reductase System  

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Full Text Available Selenium is a chemical element participating in the synthesis of selenocysteine residues that play a pivotal role in the enzymatic activity efficiency of selenoproteines. The methionine sulfoxide reductase (Msr system that reduces methionine sulfoxide (MetO to methionine comprises the selenoprotein MsrB (MsrB1 and the non-selenoprotein MsrA, which reduce the R- and the S- forms of MetO, respectively. The effects of a selenium deficient (SD diet, which was administrated to wild type (WT and MsrA knockout mice (MsrA-/-, on the expression and function of Msr-related proteins are examined and discussed. Additionally, new data about the levels of selenium in brain, liver, and kidneys of WT and MsrA-/- mice are presented and discussed.

Jackob Moskovitz

2009-07-01

225

Nucleotide sequence of dihydrofolate reductase type VI.  

Science.gov (United States)

The complete sequence of the type VI dihydrofolate reductase (DHFR) gene from plasmid pUK672 was determined. The structural gene coded for a polypeptide of 157 amino acids which had a deduced mol. wt of 17,424. Comparison with amino-acid sequences of the type I, type V and Escherichia coli K12 chromosomal DHFRs showed that there was 63%, 61% and 31% homology respectively. Putative RNA polymerase and ribosomal binding sites were identified proximal to the initiation codon and a feature consistent with transcription termination was present distal to the coding region. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed that the enzyme had a subunit mol. wt of 17,500. PMID:1941991

Wylie, B A; Koornhof, H J

1991-10-01

226

Oxidised- and total non-protein bound glutathione and related thiols in gallbladder bile of patients with various gastrointestinal disorders  

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Full Text Available Abstract Background Glutathione is a tripeptide composed of glutamate, cysteine and glycine, accomplishing a broad range of vital functions. Synthesis of glutathione and cysteine is performed mainly in the liver, whereas most other tissues are supplied with these thiols via sinusoidal efflux into the blood. Since canalicular efflux also occurs, thiols may be present in human bile. However, thiol composition of human gallbladder bile is largely unknown, which makes it difficult to speculate on the exact function of thiols in bile. In this study we report on the levels of non-protein bound thiols in gallbladder bile of patients with various gastrointestinal disorders. Methods Gallbladder bile was obtained after cholecystectomy from 30 patients who were operated for pancreatic cancer, duodenal cancer, chronic pancreatitis or cholecystolithiasis. Bile was analysed for non-protein bound total- and oxidised glutathione and related thiols, by high performance liquid chromatography. Results A more than 100-fold inter-individual variation in non-protein bound thiol levels was found in human gallbladder bile of patients with a variety of gastrointestinal disorders. Bile did contain high amounts of cysteine, whereas much lower levels of glutathione, cysteinylglycine and homocysteine were detected. Most thiols were present in their oxidised forms. Conclusion Thiols are present in considerable amounts in human gallbladder bile of patients with various gastrointestinal disorders, levels of cysteine being much higher than those of glutathione and other thiols. Most thiols were in their oxidised forms, which may indicate the presence of considerable chemical- or oxidative stress in the patients studied here.

Peters Joost H

2007-02-01

227

Substrate and thiol specificity of a stress-inducible glutathione transferase from soybean.  

Science.gov (United States)

An RT-PCR-derived clone encoding a stress-inducible glutathione transferase (GSTGm1) from soybean has been overexpressed in E. coli. The enzyme was active as the dimer GSTGm1-1 and showed GST and glutathione peroxidase activity toward diverse xenobiotics, including analogues of natural stress-metabolites. The selective herbicides, fomesafen and acifluorfen, were conjugated more actively with homoglutathione (hGSH), the major thiol in soybean, than with glutathione (GSH). No thiol preference was shown with the related herbicide, fluorodifen, while GSH was preferred with metolachlor and most non-herbicide substrates. Similar thiol-dependent specificities were observed in GST preparations from plants of varying GSH/hGSH content. PMID:9224692

Skipsey, M; Andrews, C J; Townson, J K; Jepson, I; Edwards, R

1997-06-16

228

Thiol peptides induction in the seagrass Thalassia testudinum (Banks ex König) in response to cadmium exposure.  

Science.gov (United States)

Trace metal accumulation and thiol compounds synthesis as induced by cadmium exposure was studied in the seagrass Thalassia testudinum. Shoots were exposed for 24, 48, 96 and 144 h to several CdCl(2) concentrations (0, 30, 50 and 70 microM). Levels of cadmium, cysteine, glutathione (GSH), gamma-glutamylcysteine (gamma-EC), and phytochelatin-like peptides were determined in green blades, live sheaths and root/rhizomes tissues. Metal accumulation was dependent on Cd concentration and type of tissue, with green blades showing the highest content followed by live sheaths and root/rhizomes. All tissues experienced an increase in thiol-containing compounds as a response to cadmium exposure. Live sheaths showed the highest levels of cysteine, GSH and gamma-EC. This is the first report of induction of thiol peptides, presumably phytochelatins, by a trace metal in a sea grass species. PMID:18031838

Alvarez-Legorreta, Teresa; Mendoza-Cozatl, David; Moreno-Sanchez, Rafael; Gold-Bouchot, Gerardo

2008-01-20

229

A selective colorimetric chemosensor for thiols based on intramolecular charge transfer mechanism  

Energy Technology Data Exchange (ETDEWEB)

Compound 1 as an electron donor-acceptor compound with N,N-dimethylaniline and quinone units was designed for a highly selective colorimetric determination of thiol-containing amino acids and peptides, by making use of the unique reactivity of thiol towards quinone. Compound 1 shows a strong intramolecular charge transfer (ICT) band around 582 nm; but, it decreased after addition of either cysteine (Cys) or glutathione (GSH). Moreover, the ICT band intensity at 582 nm decreased linearly with the increasing concentrations of Cys or GSH. The interference from other amino acids can be neglected. Therefore, compound 1 can be employed as a selective colorimetric visual chemosensor for thiol-containing amino acids and peptides.

Zeng Yan [Beijing National Laboratory for Molecular Sciences, Organic Solids Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Zhang Guanxin [Beijing National Laboratory for Molecular Sciences, Organic Solids Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China)], E-mail: gxzhang@iccas.ac.cn; Zhang Deqing [Beijing National Laboratory for Molecular Sciences, Organic Solids Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China)], E-mail: dqzhang@iccas.ac.cn

2008-10-10

230

A selective colorimetric chemosensor for thiols based on intramolecular charge transfer mechanism  

International Nuclear Information System (INIS)

Compound 1 as an electron donor-acceptor compound with N,N-dimethylaniline and quinone units was designed for a highly selective colorimetric determination of thiol-containing amino acids and peptides, by making use of the unique reactivity of thiol towards quinone. Compound 1 shows a strong intramolecular charge transfer (ICT) band around 582 nm; but, it decreased after addition of either cysteine (Cys) or glutathione (GSH). Moreover, the ICT band intensity at 582 nm decreased linearly with the increasing concentrations of Cys or GSH. The interference from other amino acids can be neglected. Therefore, compound 1 can be employed as a selective colorimetric visual chemosensor for thiol-containing amino acids and peptides

2008-10-10

231

The Function of Cytoplasmic Flavin Reductases in the Reduction of Azo Dyes by Bacteria  

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A flavin reductase, which is naturally part of the ribonucleotide reductase complex of Escherichia coli, acted in cell extracts of recombinant E. coli strains under aerobic and anaerobic conditions as an “azo reductase.” The transfer of the recombinant plasmid, which resulted in the constitutive expression of high levels of activity of the flavin reductase, increased the reduction rate for different industrially relevant sulfonated azo dyes in vitro almost 100-fold. The flavin reductase g...

Russ, Rainer; Rau, Jo?rg; Stolz, Andreas

2000-01-01

232

Diamond surface functionalization with biomimicry – Amine surface tether and thiol moiety for electrochemical sensors  

Science.gov (United States)

The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen–oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

Sund, James B.; Causey, Corey P.; Wolter, Scott D.; Parker, Charles B.; Stoner, Brian R.; Toone, Eric J.; Glass, Jeffrey T.

2014-05-01

233

Self-assembled monolayers of semifluorinated thiols on electrochemically modified polycrystalline nickel surfaces  

International Nuclear Information System (INIS)

Electrochemically pretreated polycrystalline nickel substrates modified with ethanolic solutions (10-2 and 10-1 M) of four semi-fluorinated thiols with R F-R H-SH structures have been evaluated by X-ray photoelectron spectroscopy, contact angles and cyclic voltammetry measurements. Our results show that it is possible to graft highly fluorinated alkanethiols on nickel surfaces, the quality of the self assembled monolayers depending on the concentration of the dipping solutions, the dipping time as well as the length of the perfluorinated carbon chains and those of the hydrocarbon connector between the perfluorinated fragment and the thiol function

2005-11-22

234

Liquid-phase thermal condensation of aromatic and heteroaromatic thiols with ?-chloro and ?-bromostyrene  

International Nuclear Information System (INIS)

Aromatic thiols and 2-thiophenethiol react with ?-chloro- and ?-bromostyrene when heated to form the corresponding 1-phenyl-2-aryl(thienyl)thioethenes. The reaction begins at 800C and takes place effectively and strictly stereospecifically at 140-1600C. The yield of the respective vinyl sulfides amounts to 70-95%. ?-Bromostyrene reacts with thiophenol more slowly than ?-chlorostyrene, and this is due to the inhibiting action of the hydrogen bromide, which acts as a trap for the thiyl radicals and gives rise to decomposition of the obtained 1-phenyl-2-phenylthioethene. Among the investigated thiols 2-thiophenethiol has the lowest reactivity

1987-11-20

235

Orthogonal protection of peptides and peptoids for cyclization by the thiol-ene reaction and conjugation.  

Science.gov (United States)

Cyclic peptides and peptoids were prepared using the thiol-ene Michael-type reaction. The linear precursors were provided with additional functional groups allowing for subsequent conjugation: an orthogonally protected thiol, a protected maleimide, or an alkyne. The functional group for conjugation was placed either within the cycle or in an external position. The click reactions employed for conjugation with suitably derivatized nucleoside or oligonucleotides were either cycloadditions (Diels-Alder, Cu(I)-catalyzed azide-alkyne) or the same Michael-type reaction as for cyclization. PMID:24617567

Elduque, Xavier; Pedroso, Enrique; Grandas, Anna

2014-04-01

236

Tandem Pd/Au-catalyzed route to ?-sulfenylated carbonyl compounds from terminal propargylic alcohols and thiols.  

Science.gov (United States)

An efficient and highly atom-economical tandem Pd/Au-catalyzed route to ?-sulfenylated carbonyl compounds from terminal propargylic alcohols and thiols has been developed. This one-step procedure has a wide substrate scope with respect to substituents at the ?-position of the alcohol. Both aromatic and aliphatic thiols generated the ?-sulfenylated carbonyl products in good to excellent yields. A mechanism is proposed in which the reaction proceeds through a Pd-catalyzed regioselective hydrothiolation at the terminal triple bond of the propargyl alcohol followed by an Au-catalyzed 1,2-hydride migration. PMID:24478141

Biswas, Srijit; Watile, Rahul A; Samec, Joseph S M

2014-02-17

237

Studies of Aqueous U(IV) Complexation under Thiol-rich Conditions  

International Nuclear Information System (INIS)

Organic thiol compounds and hydrogen sulfide (H2S) are electron donors and metabolic products of sulfate reducing bacteria. In addition, they are among redox potential (Eh) determinants of groundwater systems due to their redox characteristics. The low values of acid dissociation constants for .SH (pKa, 7-9) compared to those of aliphatic or phenolic .OH, impart greater anionic and metal-binding properties to the molecules. Recently, we demonstrated that a thiol compound (i. e., thiosalicylate) enhances the solubility of U(VI) at higher pH levels (2 nanoparticles may explain the observed solubility increase

2013-05-01

238

Serum thiols and cardiovascular risk scores: a combined assessment of transsulfuration pathway components and substrate/product ratios  

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Background: Serum thiols have shown associations with surrogate markers of cardiovascular disease. However, little information is available on their combined association with validated cardiovascular risk scores for primary prevention at population level. We sought to determine whether individual serum thiol concentrations and substrate/product ratios within the transsulfuration pathway are independently associated with such scores.

2013-01-01

239

Selective fluorometric detection of aromatic thiols by a chemosensor containing two electrophilic sites with different local softness.  

Science.gov (United States)

A resorufin–dinitrophenyl ether conjugate (1) shows emission enhancement for aromatic thiols in aqueous media with a neutral–basic pH, while being nonemissive for aliphatic thiols. This is achieved by two electrophilic sites with different local softness on compound 1; the respective sites selectively react with aromatic or aliphatic thiolate anions. PMID:24189889

Shiraishi, Yasuhiro; Yamamoto, Kohei; Sumiya, Shigehiro; Hirai, Takayuki

2013-12-25

240

Fumarate reductase system of filarial parasite Setaria digitata.  

Science.gov (United States)

In the cattle filarial parasite Setaria digitata the mitochondria like particles have been shown to possess NADH dependent fumarate reduction coupled with site I electron transport associated phosphorylation. This reduction is catalysed by the fumarate reductase system. The Km for fumarate is 1.47 mM and that for NADH is 0.33 mM. This activity is sensitive to rotenone, antimycin A and o-Hydroxy diphenyl. One ATP is produced for each pair of electrons transferred to fumarate. The fumarate reductase system consisting of NADH-coenzyme Q reductase, cytochrome b like component(s) and succinate dehydrogenase/fumarate reductase is thus very important and hence specific inhibitors of the system may prove useful in the effective control of filariasis. PMID:1567448

Unnikrishnan, L S; Raj, R K

1992-04-15

 
 
 
 
241

Characterization of mitochondrial thioredoxin reductase from C. elegans  

International Nuclear Information System (INIS)

Thioredoxin reductase catalyzes the NADPH-dependent reduction of the catalytic disulfide bond of thioredoxin. In mammals and other higher eukaryotes, thioredoxin reductases contain the rare amino acid selenocysteine at the active site. The mitochondrial enzyme from Caenorhabditis elegans, however, contains a cysteine residue in place of selenocysteine. The mitochondrial C. elegans thioredoxin reductase was cloned from an expressed sequence tag and then produced in Escherichia coli as an intein-fusion protein. The purified recombinant enzyme has a k cat of 610 min-1 and a K m of 610 ?M using E. coli thioredoxin as substrate. The reported k cat is 25% of the k cat of the mammalian enzyme and is 43-fold higher than a cysteine mutant of mammalian thioredoxin reductase. The enzyme would reduce selenocysteine, but not hydrogen peroxide or insulin. The flanking glycine residues of the GCCG motif were mutated to serine. The mutants improved substrate binding, but decreased the catalytic rate

2006-08-04

242

Cloning and sequence of the human adrenodoxin reductase gene.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Adrenodoxin reductase (ferrodoxin:NADP+ oxidoreductase, EC 1.18.1.2) is a flavoprotein mediating electron transport to all mitochondrial forms of cytochrome P450. We cloned the human adrenodoxin reductase gene and characterized it by restriction endonuclease mapping and DNA sequencing. The entire gene is approximately 12 kilobases long and consists of 12 exons. The first exon encodes the first 26 of the 32 amino acids of the signal peptide, and the second exon encodes the remainder of signal ...

1990-01-01

243

Species-Specific Differences in Translational Regulation of Dihydrofolate Reductase  

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We have observed that rodent cell lines (mouse, hamster) contain approximately 10 times the levels of dihydrofolate reductase as human cell lines, yet the sensitivity to methotrexate (ED50), the folate antagonist that targets this enzyme, is similar. Our previous studies showed that dihydrofolate reductase protein levels increased after methotrexate exposure, and we proposed that this increase was due to the relief of feedback inhibition of translation as a consequence of methotrexate binding...

Hsieh, Yi-ching; Skacel, Nancy E.; Bansal, Nitu; Scotto, Kathleen W.; Banerjee, Debabrata; Bertino, Joseph R.; Abali, Emine Ercikan

2009-01-01

244

Plasmid-Encoded Diacetyl (Acetoin) Reductase in Leuconostoc pseudomesenteroides  

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A plasmid-borne diacetyl (acetoin) reductase (butA) from Leuconostoc pseudomesenteroides CHCC2114 was sequenced and cloned. Nucleotide sequence analysis revealed an open reading frame encoding a protein of 257 amino acids which had high identity at the amino acid level to diacetyl (acetoin) reductases reported previously. Downstream of the butA gene of L. pseudomesenteroides, but coding in the opposite orientation, a putative DNA recombinase was identified. A two-step PCR approach was used to...

Rattray, Fergal P.; Myling-petersen, Dorte; Larsen, Dianna; Nilsson, Dan

2003-01-01

245

Nitrogenase reductase: A functional multigene family in Rhizobium phaseoli  

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The complete coding sequence of the nitrogenase reductase gene (nifH) is present in three different regions of a Rhizobium phaseoli symbiotic plasmid. Homology between two of the regions containing nifH coding sequences extends over 5 kilobases. These in turn share 1.3 kilobases of homology with the third region. The nucleotide sequences of the three nitrogenase reductase genes were found to be identical. Site-directed insertion mutagenesis indicated that none of the three genes is indispensa...

1985-01-01

246

How do HMG-CoA reductase inhibitors prevent stroke?  

Science.gov (United States)

Stroke is a heterogeneous disorder with significantly high morbidity and mortality. The relationship between serum cholesterol level and the incidence of stroke remains controversial. Recent evidence from primary and secondary prevention trials suggests that treatment with hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors may reduce the incidence of stroke in patients with coronary artery disease (CAD). In this review, we attempt to outline and describe the potential mechanisms of HMG-CoA reductase inhibitors in the prevention of stroke. In addition to their lipid-lowering action HMG-CoA reductase inhibitors appear to exert their beneficial effects by various nonlipid-lowering mechanisms including anti-inflammatory effects, effect on endothelial function and coagulation cascade. Treatment with HMG-CoA reductase inhibitors is associated with decreased progression, plaque stablization and even regression of atheromatous plaque in the carotid arteries. HMG-CoA reductase inhibitors also inhibit the coagulation cascade at various levels such as activation of prothrombin, factor V, factor X and liberation of tissue factor in response to vascular injury. Inhibition of fibrinolysis occurs secondary to inhibition of plasmin generation. Pravastatin therapy is associated with a reduction in the size of aortic atheroma which is an independent risk factor for stroke. Lastly, left ventricular dysfunction after acute myocardial infarction is associated with an increased risk of stroke and HMG-CoA reductase inhibitors may indirectly decrease the incidence of stroke by reducing coronary events. Most of these effects are independent of the cholesterol-lowering effects of HMG-CoA reductase inhibitors. In conclusion, HMG-CoA reductase inhibitors may have a role in primary prevention of stroke in patients with CAD. PMID:14727994

Bedi, Ashwani; Flaker, Gregory C

2002-01-01

247

S-Nitrosoglutathione Reductase in Human Lung Cancer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

S-Nitrosoglutathione (GSNO) reductase regulates cell signaling pathways relevant to asthma and protects cells from nitrosative stress. Recent evidence suggests that this enzyme may prevent human hepatocellular carcinoma arising in the setting of chronic hepatitis. We hypothesized that GSNO reductase may also protect the lung against potentially carcinogenic reactions associated with nitrosative stress. We report that wild-type Ras is S-nitrosylated and activated by nitrosative stress and that...

Marozkina, Nadzeya V.; Wei, Christina; Yemen, Sean; Wallrabe, Horst; Nagji, Alykhan S.; Liu, Lei; Morozkina, Tatiana; Jones, David R.; Gaston, Benjamin

2012-01-01

248

Structural Elucidation of Chalcone Reductase and Implications for Deoxychalcone Biosynthesis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

4,2?,4?,6?-tetrahydroxychalcone (chalcone) and 4,2?,4?-trihydroxychalcone (deoxychalcone) serve as precursors of ecologically important flavonoids and isoflavonoids. Deoxychalcone formation depends on chalcone synthase and chalcone reductase; however, the identity of the chalcone reductase substrate out of the possible substrates formed during the multistep reaction catalyzed by chalcone synthase remains experimentally elusive. We report here the three-dimensional structure of alfal...

2005-01-01

249

Effects of thioredoxin reductase-1 deletion on embryogenesis and transcriptome  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thioredoxin reductases (Txnrd)1 maintain intracellular redox homeostasis in most organisms. Metazoans Txnrds also participate in signal transduction. Mouse embryos homozygous for a targeted null mutation of the txnrd1 gene, encoding the cytosolic thioredoxin reductase, were viable at embryonic day 8.5 (E8.5) but not at E9.5. Histology revealed that txnrd1?/? cells were capable of proliferation and differentiation; however, mutant embryos were smaller than wild-type littermates and failed ...

Bondareva, Alla A.; Capecchi, Mario R.; Iverson, Sonya V.; Li, Yan; Lopez, Nathan I.; Lucas, Olivier; Merrill, Gary F.; Prigge, Justin R.; Siders, Ashley M.; Wakamiya, Maki; Wallin, Stephanie L.; Schmidt, Edward E.

2007-01-01

250

Aldose reductase inhibitory activity and antioxidant capacity of pomegranate extracts  

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The pomegranate, Punica granatum L., has been the subject of current interest as a medicinal agent with wide-ranging therapeutic indications. In the present study, pomegranate ethanolic seed and hull extracts were tested, in comparison with a commercial sample, for the inhibition of aldose reductase, an enzyme involved in the etiology of diabetic complications. In vitro inhibition of rat lens aldose reductase was determined by a conventional method. Pomegranate ethanolic hull extract and comm...

Karasu, C?imen; Cumaog?lu, Ahmet; Gu?rpinar, Ali Rifat; Kartal, Murat; Kovacikova, Lucia; Milackova, Ivana; Stefek, Milan

2012-01-01

251

Plasma thiols inhibit hemin-dependent oxidation of human low-density lipoprotein.  

Science.gov (United States)

Oxidative modification of human low-density lipoprotein (LDL) renders it atherogenic. Previous studies demonstrated that plasma thiols promote oxidation of LDL by free ferric iron (Fe3+). The current study investigated effects of plasma thiols on oxidation of LDL by hemin, a physiological Fe3+-protoporphyrin IX complex thought to be capable of initiating LDL oxidation in vivo. In contrast to free Fe3+ which is incapable of oxidizing LDL in the absence of an exogenous reductant, hemin readily promoted LDL oxidation. During incubation of LDL (0.2 mg of protein/ml) with hemin (10 microM) at 37 degrees C for 6 h, thiobarbituric acid-reactive substances (TBARS), a marker of lipid oxidation, increased from 0.3 (+/-0.1) nmol/mg of LDL protein to a maximal concentration of 45.8 (+/-5.2) nmol/mg of LDL protein. Under the same experimental conditions, lipid-conjugated dienes, another marker of lipid oxidation, increased from non-detectable to near-maximal levels of 78-187 nmol/mg of LDL protein, and lipoprotein polyunsaturated fatty acyl-containing cholesteryl ester content decreased to 15-36% of that present in native (i.e. unoxidized) LDL. Continued incubation of LDL with hemin for up to 24 h resulted in no further significant alterations in lipoprotein levels of TBARS, lipid-conjugated dienes, and cholesteryl esters. In addition to these chemical modifications indicative of lipoprotein oxidation, agarose gel electrophoretic analysis indicated that exposure of LDL to hemin resulted in conversion of the lipoprotein to an atherogenic form as evidenced by its increased anodic electrophoretic mobility. Addition of physiological concentrations of plasma thiols (either cysteine, homocysteine or reduced glutathione; 1-100 microM, each) inhibited hemin-mediated oxidation of LDL. Thus, whereas the maximal TBARS concentration was achieved following 6 h of incubation of LDL with hemin alone, addition of thiol extended the time required to attain maximal TBARS concentration to > or = 12 h. Similar antioxidant effects of thiols on formation of lipid-conjugated dienes, loss of cholesteryl esters, and lipoprotein anodic electrophoretic mobility were also observed. However, all thiols were not equally effective at inhibiting hemin-dependent LDL oxidation. Thus, whereas reduced glutathione was most effective at inhibiting hemin-dependent LDL oxidation, an intermediate effect was observed for homocysteine, and cysteine was least effective. The inhibition of hemin-mediated LDL oxidation by plasma thiols reported here confirms a previous observation that, under certain conditions, thiols can function as antioxidants, but contrasts with the previously documented pro-oxidant effect of the same thiols on oxidation of LDL by free Fe3+. These contrasting effects of plasma thiols on hemin- and free Fe3+-mediated LDL oxidation indicate that, in vivo, the ability of thiols to function as either anti- or pro-oxidants during LDL oxidation may, at least in part, be determined by the type of oxidant stress to which the lipoprotein is exposed. PMID:10802245

Lynch, S M; Campione, A L; Moore, M K

2000-05-01

252

Nitrate Reductase and Chlorate Toxicity in Chlorella vulgaris Beijerinck  

Science.gov (United States)

A study of the growth-inhibiting effect of chlorate on the Berlin strain of Chlorella vulgaris Beijerinck provided complete confirmation of the theory of chlorate toxicity first proposed by Åberg in 1947. Chlorate was toxic to the cells growing on nitrate, and relatively nontoxic to the cells growing on ammonium. The latter cells contained only 0.01 as much NADH-nitrate reductase as the nitrate-grown cells. Chlorate could substitute for nitrate as a substrate of the purified nitrate reductase with Km = 1.2 mm, and Vmax = 0.9Vmax for nitrate. Bromate, and to a much smaller extent, iodate, also served as alternate substrates. Nitrate is a reversible competitive inhibitor of chlorate reduction, which accounts for the partial reversal, by high nitrate concentrations, of the observed inhibition of cell growth by chlorate. During the reduction of chlorate by NADH in the presence of purified nitrate reductase, there was a progressive, irreversible inhibition of the enzyme activity, presumably brought about by the reduction product, chlorite. Both the NADH-nitrate reductase activity and the associated NADH-cytochrome c reductase activity were inactivated to the same extent by added chlorite. The spectral properties of the cytochrome b557 associated with the purified enzyme were not affected by chlorite. The inactivation of the nitrate reductase by chlorite could account for the toxicity of chlorate to cells grown on nitrate, though the destruction of other cell components by chlorite or its decomposition products cannot be excluded.

Solomonson, L. P.; Vennesland, Birgit

1972-01-01

253

Yeast Sml1, a protein inhibitor of ribonucleotide reductase.  

Science.gov (United States)

Ribonucleotide reductase (RNR) catalyzes the reduction of ribonucleotides to deoxyribonucleotides; this step is rate-limiting in DNA precursor synthesis. A number of regulatory mechanisms ensure optimal deoxyribonucleotide pools, which are essential for cell viability. The best studied mechanisms are transcriptional regulation of the RNR genes during the cell cycle and in the response to DNA damage, and the allosteric regulation of ribonucleotide reductase by nucleoside triphosphates. Recently, another mode of RNR regulation has been hypothesized in yeast. A novel protein, Sml1, was shown to bind to the Rnr1 protein of the yeast ribonucleotide reductase; this interaction was proposed to inhibit ribonucleotide reductase activity when DNA synthesis is not required (Zhao, X., Muller, E.G.D., and Rothstein, R. (1998) Mol. Cell 2, 329-340). Here, we use highly purified recombinant proteins to directly demonstrate that the Sml1 protein is a strong inhibitor of yeast RNR. The Sml1p specifically binds to the yeast Rnr1p in a 1:1 ratio with a dissociation constant of 0.4 microM. Interestingly, Sml1p also specifically binds to the mouse ribonucleotide reductase R1 protein. However, the inhibition observed in an in vitro mouse ribonucleotide reductase assay is less pronounced than the inhibition in yeast and probably occurs via a different mechanism. PMID:10593972

Chabes, A; Domkin, V; Thelander, L

1999-12-17

254

Alkaloids as aldose reductase inhibitors, with special reference to berberine.  

Science.gov (United States)

Aldose reductase is the rate-limiting enzyme of the polyol pathway that leads to conversion of glucose to sorbitol. Its increased activity, which results in abnormal activation of the polyol pathway, is implicated in the development of long-term complications of diabetes mellitus. Different plant species and their active components have shown potent in vitro and in vivo aldose reductase inhibitory activity. Among different phyto-constituents, alkaloids that contain isoquinoline/bis(isoquinoline)and related ring structures (such as berberine, palmatine, coptisine, and jateorrhizine) have shown very potent aldose reductase inhibitory activity. The structural activity relationship has revealed the importance of hydrophobic and hydrophilic groups of isoquinoline/bis(isoquinoline)for binding to an enzyme. The dioxymethylene group in the D ring (hydrophobic group) of these alkaloids binds tightly to the site adjacent to the anionic binding site (active site), while the methoxyl groups (polar) bind to the site adjacent to the nicotinamide ring of the coenzyme. On the basis of these findings, it may be proposed that the presence of isoquinoline/bis(isoquinoline)ring structures is the most important requirement for alkaloids to behave as potent aldose reductase inhibitors. Thus, other plants may also be screened for the same activity. The present review discusses these isoquinoline/bis(isoquinoline)-based alkaloids as aldose reductase inhibitors that may be used to manage diabetic complications and may substitute for the chemically synthesized aldose reductase inhibitors. PMID:24236461

Gupta, Sakshi; Singh, Nirmal; Jaggi, Amteshwar Singh

2014-03-01

255

Carboxylation mechanism and stereochemistry of crotonyl-CoA carboxylase/reductase, a carboxylating enoyl-thioester reductase  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Chemo- and stereoselective reductions are important reactions in chemistry and biology, and reductases from biological sources are increasingly applied in organic synthesis. In contrast, carboxylases are used only sporadically. We recently described crotonyl-CoA carboxylase/reductase, which catalyzes the reduction of (E)-crotonyl-CoA to butyryl-CoA but also the reductive carboxylation of (E)-crotonyl-CoA to ethylmalonyl-CoA. In this study, the complete stereochemical course of both reactions ...

Erb, Tobias J.; Brecht, Volker; Fuchs, Georg; Mu?ller, Michael; Alber, Birgit E.

2009-01-01

256

The crystal structure of Desulfovibrio vulgaris dissimilatory sulfite reductase bound to DsrC provides novel insights into the mechanism of sulfate respiration.  

Science.gov (United States)

Sulfate reduction is one of the earliest types of energy metabolism used by ancestral organisms to sustain life. Despite extensive studies, many questions remain about the way respiratory sulfate reduction is associated with energy conservation. A crucial enzyme in this process is the dissimilatory sulfite reductase (dSiR), which contains a unique siroheme-[4Fe4S] coupled cofactor. Here, we report the structure of desulfoviridin from Desulfovibrio vulgaris, in which the dSiR DsrAB (sulfite reductase) subunits are bound to the DsrC protein. The alpha(2)beta(2)gamma(2) assembly contains two siroheme-[4Fe4S] cofactors bound by DsrB, two sirohydrochlorins and two [4Fe4S] centers bound by DsrA, and another four [4Fe4S] centers in the ferredoxin domains. A sulfite molecule, coordinating the siroheme, is found at the active site. The DsrC protein is bound in a cleft between DsrA and DsrB with its conserved C-terminal cysteine reaching the distal side of the siroheme. We propose a novel mechanism for the process of sulfite reduction involving DsrAB, DsrC, and the DsrMKJOP membrane complex (a membrane complex with putative disulfide/thiol reductase activity), in which two of the six electrons for reduction of sulfite derive from the membrane quinone pool. These results show that DsrC is involved in sulfite reduction, which changes the mechanism of sulfate respiration. This has important implications for models used to date ancient sulfur metabolism based on sulfur isotope fractionations. PMID:18829451

Oliveira, Tânia F; Vonrhein, Clemens; Matias, Pedro M; Venceslau, Sofia S; Pereira, Inês A C; Archer, Margarida

2008-12-01

257

Thimerosal exposure and the role of sulfation chemistry and thiol availability in autism.  

Science.gov (United States)

Autism spectrum disorder (ASD) is a neurological disorder in which a significant number of the children experience a developmental regression characterized by a loss of previously acquired skills and abilities. Typically reported are losses of verbal, nonverbal, and social abilities. Several recent studies suggest that children diagnosed with an ASD have abnormal sulfation chemistry, limited thiol availability, and decreased glutathione (GSH) reserve capacity, resulting in a compromised oxidation/reduction (redox) and detoxification capacity. Research indicates that the availability of thiols, particularly GSH, can influence the effects of thimerosal (TM) and other mercury (Hg) compounds. TM is an organomercurial compound (49.55% Hg by weight) that has been, and continues to be, used as a preservative in many childhood vaccines, particularly in developing countries. Thiol-modulating mechanisms affecting the cytotoxicity of TM have been identified. Importantly, the emergence of ASD symptoms post-6 months of age temporally follows the administration of many childhood vaccines. The purpose of the present critical review is provide mechanistic insight regarding how limited thiol availability, abnormal sulfation chemistry, and decreased GSH reserve capacity in children with an ASD could make them more susceptible to the toxic effects of TM routinely administered as part of mandated childhood immunization schedules. PMID:23965928

Kern, Janet K; Haley, Boyd E; Geier, David A; Sykes, Lisa K; King, Paul G; Geier, Mark R

2013-08-01

258

Alterations in the Atlantic cod (Gadus morhua) hepatic thiol-proteome after methylmercury exposure.  

Science.gov (United States)

Proteomic studies in general have demonstrated that the most effective and thorough analysis of biological samples requires subfractionation and/or enrichment prior to downstream processing. In the present study, Atlantic cod (Gadus morhua) liver samples were fractionated using activated thiol sepharose to isolate hepatic proteins containing free/reactive cysteines. This subset of proteins is of special interest when studying the physiological effects attributed to methylmercury (MeHg) exposure. Methylmercury is a persistent environmental contaminant that has a potent affinity toward thiol groups, and can directly bind proteins via available cysteine residues. Further, alterations in the cod thiol-proteome following MeHg exposure (2 mg/kg body weight) were explored with two-dimensional gel electrophoresis combined with downstream mass spectrometry analyses for protein identifications. Thirty-five protein spots were found to respond to MeHg exposure, and 13 of these were identified when searching cod-specific databases with acquired mass spectrometry data. Among the identified thiol-containing proteins, some are known to respond to MeHg treatment, including constituents of the cytoskeleton, and proteins involved in oxidative stress responses, protein synthesis, protein folding, and energy metabolism. Methylmercury also appeared to affect cod heme metabolism/turnover, producing significantly altered levels of hemoglobin and hemopexin in liver following metal exposure. The latter finding suggests that MeHg may also affect the hematological system in Atlantic cod. PMID:24754398

Karlsen, O A; Sheehan, D; Goksøyr, A

2014-01-01

259

Thiol-Ene Induced Diphosphonic Acid Functionalization of Superparamagnetic Iron Oxide Nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

Multi-functional organic molecules represent an interesting challenge for nanoparticle functionalization due to the potential for undesirable interactions between the substrate material and the variable functionalities, making it difficult to control the final orientation of the ligand. In the present study, UV-induced thiol-ene click chemistry has been utilized as a means of directed functionalization of bifunctional ligands on an iron oxide nanoparticle surface. Allyl diphosphonic acid ligand was covalently deposited on the surface of thiol-presenting iron oxide nanoparticles via the formation of a UV-induced thioether. This method of thiol-ene click chemistry offers a set of reaction conditions capable of controlling the ligand deposition and circumventing the natural affinity exhibited by the phosphonic acid moiety for the iron oxide surface. These claims are supported via a multimodal characterization platform which includes thermogravimetric analysis, x-ray photoelectron spectroscopy, and metal contact analysis and are consistent with a properly oriented, highly active ligand on the nanoparticle surface. These experiments suggest thiol-ene click chemistry as both a practical and generally applicable strategy for the directed deposition of multi-functional ligands on metal oxide nanoparticle surfaces.

Rutledge, Ryan D.; Warner, Cynthia L.; Pittman, Jonathan W.; Addleman, Raymond S.; Engelhard, Mark H.; Chouyyok, Wilaiwan; Warner, Marvin G.

2010-07-20

260

Thiol-ene click chemistry: computational and kinetic analysis of the influence of alkene functionality.  

Science.gov (United States)

The influence of alkene functionality on the energetics and kinetics of radical initiated thiol-ene click chemistry has been studied computationally at the CBS-QB3 level. Relative energetics (?H°, ?H(++), ?G°, ?G(++)) have been determined for all stationary points along the step-growth mechanism of thiol-ene reactions between methyl mercaptan and a series of 12 alkenes: propene, methyl vinyl ether, methyl allyl ether, norbornene, acrylonitrile, methyl acrylate, butadiene, methyl(vinyl)silanediamine, methyl crotonate, dimethyl fumarate, styrene, and maleimide. Electronic structure calculations reveal the underlying factors that control activation barriers for propagation and chain-transfer processes of the step-growth mechanism. Results are further extended to predict rate constants for forward and reverse propagation and chain-transfer steps (k(P), k(-P), k(CT), k(-CT)) and used to model overall reaction kinetics. A relationship between alkene structure and reactivity in thiol-ene reactions is derived from the results of kinetic modeling and can be directly related to the relative energetics of stationary points obtained from electronic structure calculations. The results predict the order of reactivity of alkenes and have broad implications for the use and applications of thiol-ene click chemistry. PMID:22853003

Northrop, Brian H; Coffey, Roderick N

2012-08-22

 
 
 
 
261

The influence of fatty acids on determination of human serum albumin thiol group.  

Science.gov (United States)

During investigation of the changes of the Cys34 thiol group of human serum albumin (HSA) (isolated by affinity chromatography with Cibacron Blue (CB)) in diabetes, we found that the HSA-SH content was higher (11-33%) than the total serum thiol content. The influence of fatty acids (FA) binding to HSA on this discrepancy was investigated in vitro (using fluorescence and CD spectroscopy and GC) and with HSA samples from diabetic (n=20) and control groups (n=17). HSA-bound FA determine the selection of HSA molecules by CB and enhance reactivity and/or accessibility of the SH group. A high content of polyunsaturated FA (35.6%) leads to weaker binding of HSA molecules to CB. Rate constants of DTNB reaction with the SH group of HSA applied to a CB column, bound-HSA and unbound-HSA fractions, were 4.8×10(-3), 21.6×10(-3), and 11.2×10(-3) s(-1), respectively. The HSA-SH group of diabetics is more reactive compared with control individuals (rate constants 20.9×10(-3)±4.4×10(-3) vs 12.9×10(-3)±2.6×10(-3) s(-1), Pstearic acid ranged from 110 to 140%, while those for defatted HSA were from 98.5 to 101.7%. Thus, HSA-bound FA leads to an increase of HSA-SH content and a contribution to total serum thiols, which make the determination of the thiol group unreliable. PMID:24316317

Jovanovi?, Vesna B; Pavi?evi?, Ivan D; Taki?, Marija M; Penezi?-Romanjuk, Ana Z; A?imovi?, Jelena M; Mandi?, Ljuba M

2014-03-01

262

Rhenium(V) complexation with pyridine-2-thiol in 6M HBr  

International Nuclear Information System (INIS)

Complexing of rhenium(V) with pyridine-2-thiol in 6M HBr in the temperature range from 273 to 338 K was studied by potentiometric titration. The stepwise formation constants of rhenium(V) oxobromo pyridinethiol complex were determined and thermodynamic functions of the complexing were estimated

2004-12-01

263

Passivation of copper surfaces for selective-area ALD using a thiol self-assembled monolayer  

International Nuclear Information System (INIS)

Self-assembled monolayers (SAMs) of 1-dodecanethiol (CH3(CH2)11SH) were prepared from the vapor phase and used as a passivation layer for selective-area ALD. Thiol SAMs have commonly been prepared by immersing the substrates into a solution containing alkyl thiols. Formation of SAMs from the vapor phase, however, has advantages compared to liquid phase preparation. Passivation of surface can be done as a part of the ALD process forming a SAM first and then continuing with the common ALD process. SAMs can also be applied to three-dimensional structures relying on chemical selectivity of the thiol SAM formation. For example in the copper damascene process the thiol SAMs should form only on the copper surface but not on the insulators. In this study, the SAMs were prepared by placing the substrate and the alkylthiol to the reaction chamber and heating the system to the temperature of 73 °C. Preparation time varied from 0.5 to 24 h. Passivation properties of SAMs were tested with ALD iridium and polyimide processes. Iridium was deposited at 250? ° C for 500 cycles and polyimide at 160? ° C for 20 cycles. (paper)

2012-07-11

264

Thimerosal Exposure and the Role of Sulfation Chemistry and Thiol Availability in Autism  

Directory of Open Access Journals (Sweden)

Full Text Available Autism spectrum disorder (ASD is a neurological disorder in which a significant number of the children experience a developmental regression characterized by a loss of previously acquired skills and abilities. Typically reported are losses of verbal, nonverbal, and social abilities. Several recent studies suggest that children diagnosed with an ASD have abnormal sulfation chemistry, limited thiol availability, and decreased glutathione (GSH reserve capacity, resulting in a compromised oxidation/reduction (redox and detoxification capacity. Research indicates that the availability of thiols, particularly GSH, can influence the effects of thimerosal (TM and other mercury (Hg compounds. TM is an organomercurial compound (49.55% Hg by weight that has been, and continues to be, used as a preservative in many childhood vaccines, particularly in developing countries. Thiol-modulating mechanisms affecting the cytotoxicity of TM have been identified. Importantly, the emergence of ASD symptoms post-6 months of age temporally follows the administration of many childhood vaccines. The purpose of the present critical review is provide mechanistic insight regarding how limited thiol availability, abnormal sulfation chemistry, and decreased GSH reserve capacity in children with an ASD could make them more susceptible to the toxic effects of TM routinely administered as part of mandated childhood immunization schedules.

Mark R. Geier

2013-08-01

265

Peptidoglycan Recognition Proteins Kill Bacteria by Inducing Oxidative, Thiol, and Metal Stress  

Science.gov (United States)

Mammalian Peptidoglycan Recognition Proteins (PGRPs) are a family of evolutionary conserved bactericidal innate immunity proteins, but the mechanism through which they kill bacteria is unclear. We previously proposed that PGRPs are bactericidal due to induction of reactive oxygen species (ROS), a mechanism of killing that was also postulated, and later refuted, for several bactericidal antibiotics. Here, using whole genome expression arrays, qRT-PCR, and biochemical tests we show that in both Escherichia coli and Bacillus subtilis PGRPs induce a transcriptomic signature characteristic of oxidative stress, as well as correlated biochemical changes. However, induction of ROS was required, but not sufficient for PGRP killing. PGRPs also induced depletion of intracellular thiols and increased cytosolic concentrations of zinc and copper, as evidenced by transcriptome changes and supported by direct measurements. Depletion of thiols and elevated concentrations of metals were also required, but by themselves not sufficient, for bacterial killing. Chemical treatment studies demonstrated that efficient bacterial killing can be recapitulated only by the simultaneous addition of agents leading to production of ROS, depletion of thiols, and elevation of intracellular metal concentrations. These results identify a novel mechanism of bacterial killing by innate immunity proteins, which depends on synergistic effect of oxidative, thiol, and metal stress and differs from bacterial killing by antibiotics. These results offer potential targets for developing new antibacterial agents that would kill antibiotic-resistant bacteria.

Kashyap, Des Raj; Rompca, Annemarie; Gaballa, Ahmed; Helmann, John D.; Chan, Jefferson; Chang, Christopher J.; Hozo, Iztok; Gupta, Dipika; Dziarski, Roman

2014-01-01

266

Thiol-disulfide organization in alliin lyase (alliinase) from garlic (Allium sativum).  

Science.gov (United States)

Alliinase, an enzyme found in garlic, catalyzes the synthesis of the well-known chemically and therapeutically active compound allicin (diallyl thiosulfinate). The enzyme is a homodimeric glycoprotein that belongs to the fold-type I family of pyridoxal-5'-phosphate-dependent enzymes. There are 10 cysteine residues per alliinase monomer, eight of which form four disulfide bridges and two are free thiols. Cys368 and Cys376 form a S--S bridge located near the C-terminal and plays an important role in maintaining both the rigidity of the catalytic domain and the substrate-cofactor relative orientation. We demonstrated here that the chemical modification of allinase with the colored --SH reagent N-(4-dimethylamino-3,5-dinitrophenyl) maleimide yielded chromophore-bearing peptides and showed that the Cys220 and Cys350 thiol groups are accesible in solution. Moreover, electron paramagnetic resonance kinetic measurements using disulfide containing a stable nitroxyl biradical showed that the accessibilities of the two --SH groups in Cys220 and Cys350 differ. Neither enzyme activity nor protein structure (measured by circular dichroism) were affected by the chemical modification of the free thiols, indicating that alliinase activity does not require free --SH groups. This allowed the oriented conjugation of alliinase, via the --SH groups, with low- or high-molecular-weight molecules as we showed here. Modification of the alliinase thiols with biotin and their subsequent binding to immobilized streptavidin enabled the efficient enzymatic production of allicin. PMID:19177363

Weiner, Lev; Shin, Irina; Shimon, Linda J W; Miron, Talia; Wilchek, Meir; Mirelman, David; Frolow, Felix; Rabinkov, Aharon

2009-01-01

267

Analysis of thiols by microchip capillary electrophoresis for in situ planetary investigations.  

Science.gov (United States)

The detection of thiols on extraterrestrial bodies could provide evidence for life, as well as a host of potential prebiological or abiological processes. Here, we report a novel protocol to analyze organic thiols by microchip CE with LIF detection. Thiols were labeled with Pacific Blue C5 maleimide and analyzed by MEKC. The separation buffer consisted of 15 mM tetraborate pH 9.2 and 25 mM SDS. The optimized method provided LODs ranging from 1.4 to 15 nM. The method was validated using samples collected from geothermal pools at Hot Creek Gorge, California, which were found to contain 2-propanethiol and 1-butanethiol in the nanomolar concentration range. These samples serve as chemical analogues to material potentially present in the reducing environment of primitive Earth and also at sulfurous regions of Mars. Hence, the protocol developed here enables highly sensitive thiol analysis in samples with complexity comparable to that expected in astrobiologically relevant extraterrestrial settings. This new protocol could be readily added to the existing suite of microfluidic chemical analyses developed for in situ planetary exploration; all that is required is the incorporation of two new reagents to the payload of an existing instrument concept. PMID:23161601

Mora, Maria F; Stockton, Amanda M; Willis, Peter A

2013-01-01

268

Factors influencing the oxidation of cysteamine and other thiols: implications for hyperthermic sensitization and radiation protection  

International Nuclear Information System (INIS)

Some of the factors influencing the oxygen uptake and peroxide formation for cysteamine (MEA) and other thiols in serum-supplemented modified McCoy's 5A, a well-known medium used to cultivate a variety of cells in vitro, have been studied. The oxidation of MEA and cysteine in modified McCoy's 5A has been compared with that in Ham's F-12, MEM, and phosphate-buffered saline. The ability to produce peroxide is dependent upon the temperature, the concentration of thiol, the presence of copper ions, and pH of the medium. Catalase also reduces the oxygen uptake for all thiols. Superoxide dismutase (SOD) was found to stimulate the oxygen uptake in the case of MEA and cysteine, but had little or no effect with DTT and glutathione. The combined presence of SOD and catalase resulted in less inhibition of oxygen uptake than that obtained by catalase alone. Alkaline pH was found to enhance the oxidation of cysteine and MEA. The results indicate that many problems may arise when thiols are added to various media. A major consideration is concerned with the production of peroxide, superoxide, and reduced trace metal intermediates. The presence of these intermediates may result in the production of hydroxyl radical intermediates as well as the eventual oxygen depletion from the medium

1984-01-01

269

Electrochemical determination of thiols at single-wall carbon nanotubes and PQQ modified electrodes.  

Science.gov (United States)

The electrocatalytic oxidation of thiols has been observed at a glassy carbon (GC) electrode coated with a single-wall carbon nanotube (SWNT) film. Fourteen thiols including L-cysteine (CySH) and glutathione were tested using the SWNT/GC electrode, and the cyclic voltammetry (CV) showed that each thiol was oxidized at much less positive potential than those at other electrodes such as bare GC and diamond electrodes. The SWNT/GC electrode was also modified with pyrroloquinoline quinone (PQQ) which showed a further improvement of the catalytic behavior of the SWNT/GC electrode: e.g. the oxidation peak current of CySH was observed at 0.27 V vs. Ag/AgCl in pH 7.5 phosphate buffer. The amperometic responses at these electrodes showed a linear relationship with the substrate concentration in a 10(-6)-10(-3) M range and 10(-6)-10(-7) M detection limits for several thiols including CySH, L-homocysteine, N-acetyl-L-cysteine, L-penicillamine and glutathione. These electrodes show a response time of 2-3 s and storage stabilities over 3 weeks. A PQQ/SWNT/GC electrode has been successfully applied for the assay of both L-cysteine and N-acetyl-L-cysteine in the dietary supplement. PMID:15569631

Han, Heyou; Tachikawa, Hiroyasu

2005-01-01

270

The reverse of the 'repair' reaction of thiols: H-abstraction at carbon by thiyl radicals  

International Nuclear Information System (INIS)

Thiyl radicals (RS radical) formed by the reaction of radiolytically generated OH radicals with thiols, e.g. 1,4-dithiothreitol (DTT), react with cis- and trans-2,5-dimethyltetrahydrofuran by abstracting an H atom in the ?-position to the ether function (k approx.5 x 10"3dm"3mol"-"1s"-"1). The so-formed planar ether radical is 'repaired' by the thiol (k = 6 x 10"8dm"3mol"-"1s"-"1) thereby regenerating a cis-or trans-2,5-dimethyltetrahydrofuran molecule. In this reaction a thiyl radical is reproduced. Thus trans-2,5-Me_2 THF from cis-2,5-Me_2THF and vice versa are formed in a chain reaction: at a dose rate of 2.8 x 10"-"3Gy s"-"1 and a trans-2,5-Me_2THF concentration of 1 x 10"-"2mol dm"-"3 using DTT as the thiol, G(cis-2,5-Me_2THF) = 160 has been found. The chain reaction is very sensitive to impurities and also to disulphides such as those radiolytically formed. 2,5-Me_2THF can be regarded as a model for the sugar moiety of DNA where the C(4')-radical is known to lead to DNA strand breakage. The possible role of cellular thiols in the repair of the C(4')DNA radical, and also the conceivable role of thiyl radicals inducing DNA strand breakage, are discussed. (author)

1987-01-01

271

Production of carbonyl reductase by Metschnikowia koreensis.  

Science.gov (United States)

A new strain of the yeast Metschnikowia koreensis was grown in shake flasks and a stirred bioreactor for the production of carbonyl reductase. The optimal conditions in the bioreactor for maximizing the biomass specific activity of the enzyme were found to be: a medium composed of glucose (20 g/L), peptone (5 g/L), yeast extract (5 g/L) and zinc sulfate (0.3g/L); the pH controlled at 7; the temperature controlled at 25 °C; an agitation speed of 500 rpm; and an aeration rate of 0.25 vvm. In the bioreactor, a biomass specific enzyme activity of 115.6 U/gDCW was obtained and the maximum biomass concentration was 15.3 gDCW/L. The biomass specific enzyme activity obtained in the optimized bioreactor culture was 11-fold higher than the best result achieved in shake flasks. The bioreactor culture afforded a 2.7-fold higher biomass concentration than could be attained in shake flasks. PMID:21967713

Singh, Amit; Chisti, Yusuf; Banerjee, Uttam Chand

2011-11-01

272

QSAR Study on Some Dihydrofolate Reductase Inhibitors  

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Full Text Available Dihydrofolate reductase (DHFR inhibitors have proved to be of value as antibacterial, antimalarial, and antitumor agents. Some 2,4-diamino-5-methyl-6-[(substituted anilinomethyl]pyrrido[2,3-d]pyrimidines were reported earlier as DHFR inhibitors. Using non-parabolic Hansch models, a QSAR study was performed in an attempt to find out the required physicochemical and structural features of these compounds for DHFR inhibition. This study revealed the importance of resonance effect at R2 and R3 positions and sum of molar refractivity (?MR at R2, R3, R4, and R5 positions of the ring C. Lipophilicity of the whole molecule (log P also played an important role. The presence of OCH3 group at R4 of the phenyl C ring and CH3 at R1 of anilino N might be advantageous to DHFR inhibition. This QSAR study is beneficial for future studies to carry out further tailoring of this type of compounds with an objective to increase DHFR inhibitory activity.

Bikash Debnath

2003-03-01

273

Binding of Fidarestat Stereoisomers with Aldose Reductase  

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Full Text Available The stereospecificity in binding to aldose reductase (ALR2 of two fidarestat {6-fluoro-2',5'-dioxospiro[chroman-4,4'-imidazolidine]-2-carboxamide} stereoisomers [(2S,4Sand (2R,4S] has been investigated by means of molecular dynamics simulations using freeenergy integration techniques. The difference in the free energy of binding was found to be2.0 ± 1.7 kJ/mol in favour of the (2S,4S-form, in agreement with the experimentalinhibition data. The relative mobilities of the fidarestats complexed with ALR2 indicate alarger entropic penalty for hydrophobic binding of (2R,4S-fidarestat compared to (2S,4S-fidarestat, partially explaining its lower binding affinity. The two stereoisomers differmainly in the orientation of the carbamoyl moiety with respect to the active site and rotationof the bond joining the carbamoyl substituent to the ring. The detailed structural andenergetic insights obtained from out simulations allow for a better understanding of thefactors determining stereospecific inhibitor-ALR2 binding in the EPF charges model.

Dae-Sil Lee

2006-11-01

274

Aldose reductase, oxidative stress and diabetic mellitus  

Directory of Open Access Journals (Sweden)

Full Text Available Diabetes mellitus (DM is a complex metabolic disorder arising from lack of insulin production or insulin resistance 1. DM is a leading cause of morbidity and mortality in the developed world, particularly from vascular complications such as atherothrombosis in the coronary vessels. Aldose reductase (AR [ALR2; EC 1.1.1.21], a key enzyme in the polyol pathway, catalyzes NADPH-dependent reduction of glucose to sorbitol, leading to excessive accumulation of intracellular reactive oxygen species (ROS in various tissues of DM including the heart, vasculature, neurons, eyes and kidneys. As an example, hyperglycemia through such polyol pathway induced oxidative stress, may have dual heart actions, on coronary blood vessel (atherothrombosis and myocardium (heart failure leading to severe morbidity and mortality (reviewed in 2. In cells cultured under high glucose conditions, many studies have demonstrated similar AR-dependent increases in ROS production, confirming AR as an important factor for the pathogenesis of many diabetic complications. Moreover, recent studies have shown that AR inhibitors may be able to prevent or delay the onset of cardiovascular complications such as ischemia/reperfusion injury, atherosclerosis and atherothrombosis. In this review, we will focus on describing pivotal roles of AR in the pathogenesis of cardiovascular diseases as well as other diabetic complications, and the potential use of AR inhibitors as an emerging therapeutic strategy in preventing DM complications.

JohnHwa

2012-05-01

275

Methaneseleninic Acid is a Substrate for Truncated Mammalian Thioredoxin Reductase: Implications for the Catalytic Mechanism and Redox Signaling†  

Science.gov (United States)

Mammalian thioredoxin reductase is a homodimeric pyridine nucleotide disulfide oxidoreductase that contains the rare amino acid, selenocysteine (Sec) on a C-terminal extension. We previously have shown that a truncated version of mouse mitochondrial thioredoxin reductase missing this C-terminal tail will catalyze the reduction of a number of small molecules. Here we show that the truncated thioredoxin reductase will catalyze the reduction of methaneseleninic acid. This reduction is fast at pH 6.1 and is only 4-fold less than the full-length enzyme containing Sec. This finding suggested to us that if the C-terminal Sec residue in the holoenzyme became oxidized to the seleninic acid form (Sec-SeO2?) that it would be quickly reduced back to an active state by enzymic thiols, and further suggested to us that the enzyme would be very resistant to irreversible inactivation by oxidation. We tested this hypothesis by reducing the enzyme with NADPH and subjecting it to high concentrations of H2O2 (up to 50 mM). The results show that the enzyme strongly resisted inactivation by 50 mM H2O2. In order to determine the redox state of the C-terminal Sec residue we attempted to inhibit the enzyme with dimedone. Dimedone alkylates protein sulfenic acid residues and presumably will alklyate selenenic acid (Sec-SeOH) residues as well. The enzyme was not inhibited by dimedone even when 150-fold excess was added to the reaction containing enzyme and H2O2. We also tested the ability of the truncated enzyme to resist inactivation by oxidation as well and found that it also was resistant to high concentrations of H2O2. One assumption for the use of Sec in enzymes is that it is catalytically superior to the use of cysteine. We, and others have previously suggested that there are reasons for the use of Sec in enzymes that are unrelated to the conversion of substrate to product. The data presented here supports this assertion. The results also imply that the redox signaling function of the thioredoxin system can remain active under oxidative stress.

Snider, Gregg; Grout, Leah; Ruggles, Erik L.; Hondal, Robert J.

2010-01-01

276

Ferredoxin-thioredoxin reductase: a catalytically active dithiol group links photoreduced ferredoxin to thioredoxin functional in photosynthetic enzyme regulation  

International Nuclear Information System (INIS)

The mechanism by which the ferredoxin-thioredoxin system activates the target enzyme, NADP-malate dehydrogenase, was investigated by analyzing the sulfhydryl status of individual protein components with ["1"4C]iodoacetate and monobromobimane. The data indicate that ferredoxin-thioredoxin reductase (FTR)--an iron-sulfur enzyme present in oxygenic photosynthetic organisms--is the first member of a thiol chain that links light to enzyme regulation. FTR possesses a catalytically active dithiol group localized on the 13 kDa (similar) subunit, that occurs in all species investigated and accepts reducing equivalents from photoreduced ferredoxin and transfers them stoichiometrically to the disulfide form of thioredoxin m. The reduced thioredoxin m, in turn, reduces NADP-malate dehydrogenase, thereby converting it from an inactive (S-S) to an active (SH) form. The means by which FTR is able to combine electrons (from photoreduced ferredoxin) with protons (from the medium) to reduce its active disulfide group remains to be determined

1987-01-01

277

Tissue factor de-encryption, thrombus formation, and thiol-disulfide exchange.  

Science.gov (United States)

Tissue factor (TF) by forming a complex with factor VIIa (FVIIa) initiates blood coagulation. It was traditionally believed that the separation of FVIIa in circulation from subendothelial TF was the main control that was preventing spontaneous initiation of thrombosis and that circulating cells and endothelium did not express TF protein at rest in healthy individuals. However, TF has been detected in healthy human plasma and animal models of thrombosis, which indicate that TF in circulation can contribute to thrombin generation and fibrin formation after an activation event. Circulating TF-and indeed, most of the TF on the cell surface-is "encrypted" or coagulation inactive. The de-encryption step involves exposure of phosphatidylserine (PS), but PS exposure alone is insufficient for full TF activity. Allosteric disulfide bonds control protein function by mediating conformal change through the formation and breaking of disulfide bonds. TF contains a typical surface exposed allosteric bond in the membrane proximal fibronectin type III domain. Thiol-disulfide exchange involving this disulfide is implicated in TF activation with the formation of the disulfide bond corresponding with the active conformation of TF and free thiol or thiol-modified forms corresponding with encryption. Although the exact mechanism by which TF de-encryption occurs remains a subject of debate, thiol blockade and inhibition of oxidoreductases show an important role for thiol-disulfide reactions in platelet-independent pathways of coagulation in vitro and in vivo. In particular, redox active extracellular protein disulfide isomerase is involved in the earliest stages of thrombus initiation and has proven to be a potential target for antithrombotic drug development. PMID:23325480

Chen, Vivien M Y

2013-02-01

278

Acetate- and thiol-capped monodisperse ruthenium nanoparticles: XPS, XAS, and HRTEM studies.  

Science.gov (United States)

Monodisperse ruthenium nanoparticles were prepared by reduction of RuCl3 in 1,2-propanediol. The mean particle size was controlled by appropriate choice of the reduction temperature and the acetate ion concentration. Colloidal solutions in toluene were obtained by coating the metal particles with dodecanethiol. High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XANES and EXAFS for the Ru K-absorption edge) were performed on particles of two different diameters, 2 and 4 nm, and in different environments, polyol/acetate or thiol. For particles stored in polyol/acetate XPS studies revealed superficial oxidation limited to one monolayer and a surface coating containing mostly acetate ions. Analysis of the EXAFS spectra showed both oxygen and ruthenium atoms around the ruthenium atoms with a Ru-Ru coordination number N smaller than the bulk value, as expected for fine particles. In the case of 2 nm acetate-capped particles N is consistent with particles made up of a metallic core and an oxidized monolayer. For 2 nm thiol-coated particles, a Ru-S bond was evidenced by XPS and XAS. For the 4 nm particles XANES and XPS studies showed that most of the ruthenium atoms are in the zerovalent state. Nevertheless, in both cases, when capped with thiol, the Ru-Ru coordination number inferred from EXAFS is much smaller than for particles of the same size stored in polyol. This is attributed to a structural disorganization of the particles by thiol chemisorption. HRTEM studies confirm the marked dependence of the structural properties of the ruthenium particles on their chemical environment; they show the acetate-coated particles to be single crystals, whereas the thiol-coated particles appear to be polycrystalline. PMID:16008388

Chakroune, Nassira; Viau, Guillaume; Ammar, Souad; Poul, Laurence; Veautier, Delphine; Chehimi, Mohamed M; Mangeney, Claire; Villain, Françoise; Fiévet, Fernand

2005-07-19

279

Cooperative functions of manganese and thiol redox system against oxidative stress in human spermatozoa  

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Full Text Available Aims: In this study, the effects of 0.1 mM Mn 2+ on thiol components (total thiols [TSH], glutathione reduced [GSH], glutathione oxidized [GSSG] and redox ratio [GSH/ GSSG] have been determined in human spermatozoa. Settings and Design: The subjects of the study were healthy males having more than 75% motility and 80 x 10 6 sperms/mL. Materials and Methods: Fresh semen was suspended in phosphate-buffered saline (PBS (pH 7.2 and this suspension was divided into eight equal fractions. All fractions, control (containing PBS and experimental (treated/untreated with [ferrous ascorbate, FeAA - 200 FeSO 4 ?M, 1000 ?M ascorbic acid, nicotine (0.5 mM and FeAA + nicotine], supplemented/unsupplemented with Mn 2+ [0.1 mM], were incubated for 2 h at 378C. These fractions were assessed for determining the thiol components. Statistical Analysis: The data were statistically analyzed by Students " t" test. Results and Conclusions: Ferrous ascorbate, nicotine and ferrous ascorbate + nicotine induced oxidative stress and decreased GSH and redox ratio (GSH/GSSG ratio but increased the TSH and GSSG levels. Mn 2+ supplementation improved TSH, GSH and redox ratio (GSH/GSSG but decreased the GSSG level under normal and oxidative stress conditions. Thiol groups serve as defense mechanisms of sperm cells to fight against oxidative stress induced by stress inducers such as ferrous ascorbate, nicotine and their combination (ferrous ascorbate + nicotine. In addition, Mn 2+ supplementation maintains the thiol level by reducing oxidative stress.

Bansal Amrit

2009-01-01

280

Overexpression of thiol/disulfide isomerases enhances membrane fusion directed by the Newcastle disease virus fusion protein.  

Science.gov (United States)

Newcastle disease virus (NDV) fusion (F) protein directs membrane fusion, which is required for virus entry and cell-cell fusion. We have previously shown that free thiols are present in cell surface-expressed NDV F protein and that blocking the production of free thiols by thiol-disulfide exchange inhibitors inhibited the membrane fusion mediated by F protein (J Virol. 81:2328-2339, 2007). Extending these observations, we evaluated the role of the overexpression of two disulfide bond isomerases, protein disulfide isomerase (PDI) and ERdj5, in cell-cell fusion mediated by NDV glycoproteins. The overexpression of these isomerases resulted in significantly increased membrane fusion, as measured by syncytium formation and content mixing. The overexpression of these isomerases enhanced the production of free thiols in F protein when expressed without hemagglutination-neuraminidase (HN) protein but decreased free thiols in F protein expressed with HN protein. By evaluating the binding of conformation-sensitive antibodies, we found that the overexpression of these isomerases favored a postfusion conformation of surface-expressed F protein in the presence of HN protein. These results suggest that isomerases belonging to the PDI family catalyze the production of free thiols in F protein, and free thiols in F protein facilitate membrane fusion mediated by F protein. PMID:18829746

Jain, Surbhi; McGinnes, Lori W; Morrison, Trudy G

2008-12-01

 
 
 
 
281

Novel one-pot synthesis and characterization of bioactive thiol-silicate nanoparticles for biocatalytic and biosensor applications  

International Nuclear Information System (INIS)

A novel one-pot neutral synthesis using bioinspired polymers to fabricate thiol-nanoparticles is presented. The thiol-particles may be directly tethered to metal surfaces such as gold, allowing the production of self-assembled nanostructured biocatalytic or biosensor surfaces. This one-pot method has also been used to entrap enzymes within the thiol-nanoparticles; it is apparent that once enzyme entrapment is carried out a bimodal distribution of particles is formed, with particles of one mode being very similar in size to thiol-nanoparticles without enzyme entrapped, and particles of the other mode being much larger in size. To this end, efforts have been made to separate the two modes of particles for the sample containing enzyme and it has been observed that the larger mode thiol-nanoparticles do indeed contain significant amounts of enzyme in comparison to the smaller mode ones. As the enzyme-containing thiol-nanoparticles can now be isolated, this means that there are many future possibilities for the use of thiol-particles containing enzyme, as they may be used in a wide range of processes and devices which require catalytic functionalized surfaces, such as biosensors and biocatalytic reactors.

2009-02-04

282

Comparison of thiol subproteome of the vent mussel Bathymodiolus azoricus from different Mid-Atlantic Ridge vent sites.  

Science.gov (United States)

Deep-sea hydrothermal mussels Bathymodiolus azoricus live in the mixing zone where hydrothermal fluid mixes with bottom seawater, creating large gradients in the environmental conditions and are one of the most studied hydrothermal species as a model of adaptation to extreme conditions. Thiol proteins, i.e. proteins containing a thiol or sulfhydryl group (SH) play major roles in intracellular stress defense against reactive oxygen species (ROS) and are especially susceptible to oxidation. However, they are not particularly abundant, representing a small percentage of proteins in the total proteome and therefore are difficult to study by proteomic approaches. Activated thiol sepharose (ATS) was used for the rapid and quantitative selection of proteins comprising thiol- or disulfide-containing subproteomes. This study aims to isolate thiol-containing proteins from the gills of B. azoricus collected in distinct hydrothermal vents and to study the thiol-containing subproteome as a function of site-specific susceptibility to ROS. Results show that ATS is a powerful tool to isolate the thiol-containing sub-proteome and differently-expressed protein spots showed significant differences among the three vent sites, supporting previous findings that specific environmental conditions are crucial for ROS formation and that B. azoricus have different susceptibilities to oxidative stress depending on the vent site they inhabit. PMID:22964374

Company, Rui; Torreblanca, Amparo; Cajaraville, Miren; Bebianno, Maria João; Sheehan, David

2012-10-15

283

Photoluminescent and electrochemiluminescent dual-signaling probe for bio-thiols based on a ruthenium(II) complex  

International Nuclear Information System (INIS)

Highlights: ? A unique ruthenium(II) complex-based probe for bio-thiols was developed. ? The probe can respond to bio-thiols to give PL and ECL dual-signals. ? The probe was used for the PL and ECL detection of bio-thiols in aqueous media. ? The endogenous intracellular thiols were luminously imaged using the probe. - Abstract: Photoluminescence (PL) and electrochemiluminescence (ECL) detection techniques are highly sensitive and widely used methods for clinical diagnostics and analytical biotechnology. In this work, a unique ruthenium(II) complex, [Ru(bpy)2(DNBSO-bpy)](PF6)2 (bpy: 2,2?-bipyridine; DNBSO-bpy: 2,4-dinitrobenzenesulfonate of 4-(4-hydroxyphenyl)-2,2?-bipyridine), has been designed and synthesized as a highly sensitive and selective PL and ECL dual-signaling probe for the recognition and detection of bio-thiols in aqueous media. As a thiol-responsive probe, the complex can specifically and rapidly react with bio-thiols in aqueous solutions to yield a bipyridine-Ru(II) complex derivative, [Ru(bpy)2(HP-bpy)]2+ (HP-bpy: 4-(4-hydroxyphenyl)-2,2?-bipyridine), accompanied by the remarkable PL and ECL enhancements. The complex was used as a probe for the PL and ECL detections of cysteine (Cys) and glutathione (GSH) in aqueous solutions. The dose-dependent PL and ECL enhancements showed good linear relationships against the Cys/GSH concentrations with the detection limits at nano-molar concentration level. Moreover, the complex-loaded HeLa cells were prepared for PL imaging of the endogenous intracellular thiols. The results demonstrated the practical utility of the complex as a cell-membrane permeable probe for PL imaging detection of bio-thiols in living cells.

2012-08-31

284

Formation of Underbrushes on thiolated Poly (ethylene glycol) PEG monolayers by Oligoethylene glycol (OEG) terminated Alkane Thiols on Gold  

DEFF Research Database (Denmark)

Adding underbrushes of oligoethylene glycol (OEG) to monolayers of long chain PEG molecules on a surface is one of the strategies [1] in designing a suitable platform for antifouling purpose, where it is possible to have high graft density and molecular conformational freedom[4] simultaneously, there by maximal retention of activity of covalently immobilised antifouling enzyme [2] on PEG surfaces along with resistance to protein adsorption[3]. Here we present some our studies on the addition of OEG thiol molecules over a self assembled monolayer of PEG thiol on gold. The kinetics of addition of OEG thiol to monolayers of PEG thiol was followed using X- ray photoelectron spectroscopy (XPS), which indicated the time point of maximum graft density and beyond this time point there was predominant desorption of OEG thiol as indicated by the C/O ratio. The initial increase in graft density was reflected in the superior resistance towards non specific adsorption of proteins as shown by N 1s signal. We also performedprotein adsorption studies using quartz crystal microbalance (QCM-D). Studies involving addition of alkane thiol instead of OEG terminating alkane thiol showed the importance of OEG part of the molecule in superior resistance towards protein adsorption. The surfaces with underbrushes were imaged using atomic force microscopy (AFM) to detect any changes in mechanical properties of PEG thiol covered surfaces upon addition of OEG thiol. References: 1. Katsumi Uchida, Yuki Hoshino, Atsushi Tamura, Keitaro Yoshimoto, Shuji Kojima and Keichiro Yamashita, Ichiro Yamanaka, Hidenori Otsuka, Kazunori Kataoka, Yukio Nagasaki, Biointerphases. 2007, 2, 4, 126. 2. L. Selan, F. Berluti, C. Passariello, M. R. Comodiballanti, M. C. Thaller, Antimicrobial agents and chemotherapy, 1993, 37, 12, 2618. 3. Susan J. Sofia, V. Premnath, and Edward W. Merrill, Macromolecules, 1998, 31, 15, 5059. 4. Hidenori Otsuka, Yukio Nagasaki, and Kazunori Kataoka, Langmuir, 2004, 20, 26, 11285

Lokanathan, Arcot R.

2011-01-01

285

Photoluminescent and electrochemiluminescent dual-signaling probe for bio-thiols based on a ruthenium(II) complex  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer A unique ruthenium(II) complex-based probe for bio-thiols was developed. Black-Right-Pointing-Pointer The probe can respond to bio-thiols to give PL and ECL dual-signals. Black-Right-Pointing-Pointer The probe was used for the PL and ECL detection of bio-thiols in aqueous media. Black-Right-Pointing-Pointer The endogenous intracellular thiols were luminously imaged using the probe. - Abstract: Photoluminescence (PL) and electrochemiluminescence (ECL) detection techniques are highly sensitive and widely used methods for clinical diagnostics and analytical biotechnology. In this work, a unique ruthenium(II) complex, [Ru(bpy){sub 2}(DNBSO-bpy)](PF{sub 6}){sub 2} (bpy: 2,2 Prime -bipyridine; DNBSO-bpy: 2,4-dinitrobenzenesulfonate of 4-(4-hydroxyphenyl)-2,2 Prime -bipyridine), has been designed and synthesized as a highly sensitive and selective PL and ECL dual-signaling probe for the recognition and detection of bio-thiols in aqueous media. As a thiol-responsive probe, the complex can specifically and rapidly react with bio-thiols in aqueous solutions to yield a bipyridine-Ru(II) complex derivative, [Ru(bpy){sub 2}(HP-bpy)]{sup 2+} (HP-bpy: 4-(4-hydroxyphenyl)-2,2 Prime -bipyridine), accompanied by the remarkable PL and ECL enhancements. The complex was used as a probe for the PL and ECL detections of cysteine (Cys) and glutathione (GSH) in aqueous solutions. The dose-dependent PL and ECL enhancements showed good linear relationships against the Cys/GSH concentrations with the detection limits at nano-molar concentration level. Moreover, the complex-loaded HeLa cells were prepared for PL imaging of the endogenous intracellular thiols. The results demonstrated the practical utility of the complex as a cell-membrane permeable probe for PL imaging detection of bio-thiols in living cells.

Zhang Wenzhu, E-mail: wenzhuzhang@yahoo.com.cn [State Key Laboratory of Fine Chemicals, School of Chemistry, Dalian University of Technology, Dalian 116024 (China); Zhang Run; Zhang Jingmei; Ye Zhiqiang [State Key Laboratory of Fine Chemicals, School of Chemistry, Dalian University of Technology, Dalian 116024 (China); Jin Dayong [MQ Photonics Centre, Faculty of Science, Macquarie University, NSW 2109, Sydney (Australia); Yuan Jingli, E-mail: jingliyuan@yahoo.com.cn [State Key Laboratory of Fine Chemicals, School of Chemistry, Dalian University of Technology, Dalian 116024 (China)

2012-08-31

286

Role of copper and ceruloplasmin in oxidative mutagenesis induced by the gluthathione-{gamma}-glutamyl transpeptidase system and by other thiols  

Energy Technology Data Exchange (ETDEWEB)

Glutathione is activated to a mutagen by {gamma}-glutamyl transpeptidase. Other thiols, such as cysteine, penicillamine, cysteine ethylester, and cysteinylglycine, are direct mutagens in the Ames Salmonella mutagenicity test. Thiol mutagenesis is oxidative in nature and involves H{sub 2}O{sub 2} and possibly hydroxyl radicals. Transition metals are crucial for thiol autoxidation. The role of copper and ceruloplasmin (CP) in thiol-dependent mutagenesis was studied in Salmonella typhimurium strain TA 102. Cu and CP at low concentrations enhanced thiol-dependent mutagenesis in the presence, but not in the absence, and added Fe. The degree of enhancement depended on the type of thiol. At high Cu or CP concentrations, thiol mutagenesis was inhibited. Cu also decreased the mutagenicity of H{sub 2}O{sub 2}. Cu- and CP-enhanced mutagenesis were inhibited by radical scavengers, catalase, and peroxidase but not by superoxide dismutase. The effects of Cu and CP on thiol-dependent mutagenesis were similar to their effects on thiol-driven lipid peroxidation. The results indicate that the role of Cu and CP in the enhancement of thiol mutagenesis is the facilitation of the transfer of electrons from a thiol to iron, rather than in catalysis of the Fenton reaction. 34 refs., 7 figs., 2 tabs.

Stark, A.A.; Glass, G.A. [Tel-Aviv Univ., Ramat-Aviv (Israel)

1997-10-01

287

Impairment of methionine sulfoxide reductase during UV irradiation and photoaging.  

Science.gov (United States)

During chronic UV irradiation, which is part of the skin aging process, proteins are damaged by reactive oxygen species resulting in the accumulation of oxidatively modified protein. UV irradiation generates irreversible oxidation of the side chains of certain amino acids resulting in the formation of carbonyl groups on proteins. Nevertheless, certain amino acid oxidation products such as methionine sulfoxide can be reversed back to their reduced form within proteins by specific repair enzymes, the methionine sulfoxide reductases A and B. Using quantitative confocal microscopy, the amount of methionine sulfoxide reductase A was found significantly lower in sun-exposed skin as compared to sun-protected skin. Due to the importance of the methionine sulfoxide reductase system in the maintenance of protein structure and function during aging and conditions of oxidative stress, the fate of this system was investigated after UVA irradiation of human normal keratinocytes. When keratinocytes are exposed to 15 J/cm(2) UVA, methionine sulfoxide reductase activity and content are decreased, indicating that the methionine sulfoxide reductase system is a sensitive target for UV-induced inactivation. PMID:17418992

Picot, Cédric R; Moreau, Marielle; Juan, Mylène; Noblesse, Emmanuelle; Nizard, Carine; Petropoulos, Isabelle; Friguet, Bertrand

2007-09-01

288

Structure of human type II 5 alpha-reductase gene.  

Science.gov (United States)

The best known activity of steroid 5 alpha-reductase is the transformation of testosterone into dihydrotestosterone, the most potent androgen. Two types of human steroid 5 alpha-reductase cDNAs and the type I gene have previously been isolated and characterized. This report describes the isolation and characterization of the human type II 5 alpha-reductase gene, the gene most likely responsible for male pseudohermaphroditism due to 5 alpha-reductase deficiency as well as the one presumed to be involved in a major androgen-related diseases such as prostate cancer and benign prostatic hyperplasia. The type II 5 alpha-reductase gene contains five exons of 352, 164, 102, 151 and 1695 bp, respectively, which share 43.8% to 64.1% homology with exons of the corresponding type I gene. These exons are separated by four introns of greater than 29, and approximately 2.3, 2.0 and 3.0 kb. Analysis of primer extension products by polyacrylamide gel electrophoresis as well as by subcloning and sequencing reveals a start site located 71 nucleotides upstream the ATG initiating codon. PMID:1505484

Labrie, F; Sugimoto, Y; Luu-The, V; Simard, J; Lachance, Y; Bachvarov, D; Leblanc, G; Durocher, F; Paquet, N

1992-09-01

289

Exhaustive glycosylation, PEGylation, and glutathionylation of a [G4]-ene48 dendrimer via photoinduced thiol-ene coupling  

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We report in this paper the use of free-radical thiol-ene coupling (TEC) for the introduction of carbohydrate, poly(ethylene glycol), and peptide fragments at the periphery of an alkene functional dendrimer. Four different sugar thiols including glucose, mannose, lactose and sialic acid, two PEGylated thiols and the natural tripeptide glutathione were reacted with a fourth generation alkene functional dendrimer [G4]-ene48 upon irradiation at ?max 365 nm. In all cases, the 1H NMR spectra of t...

Lo Conte, Mauro; Robb, Maxwell J.; Hed, Yvonne; Marra, Alberto; Malkoch, Michael; Hawker, Craig J.; Dondoni, Alessandro

2011-01-01

290

Mechanism of thiol-supported arsenate reduction mediated by phosphorolytic-arsenolytic enzymes: II. Enzymatic formation of arsenylated products susceptible for reduction to arsenite by thiols.  

Science.gov (United States)

Enzymes catalyzing the phosphorolytic cleavage of their substrates can reduce arsenate (AsV) to the more toxic arsenite (AsIII) via the arsenolytic substrate cleavage in presence of a reductant, as glutathione or dithiotreitol (DTT). We have shown this for purine nucleoside phosphorylase (PNP), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), glycogen phosphorylase-a (GPa), and phosphotransacetylase (PTA). Using a multidisciplinary approach, we explored the mechanism whereby these enzymes mediate AsV reduction. It is known that PNP cleaves inosine with AsV into hypoxanthine and ribose-1-arsenate. In presence of inosine, AsV and DTT, PNP mediates AsIII formation. In this study, we incubated PNP first with inosine and AsV, allowing the arsenolytic reaction to run, then blocked this reaction with the PNP inhibitor BCX-1777, added DTT and continued the incubation. Despite inhibition of PNP, large amount of AsIII was formed in these incubations, indicating that PNP does not reduce AsV directly but forms a product (i.e., ribose-1-arsenate) that is reduced to AsIII by DTT. Similar studies with the other arsenolytic enzymes (GPa, GAPDH, and PTA) yielded similar results. Various thiols that differentially supported AsV reduction when present during PNP-catalyzed arsenolysis (DTT approximately dimercaptopropane-1-sulfonic acid > mercaptoethanol > DMSA > GSH) similarly supported AsV reduction when added only after a transient PNP-catalyzed arsenolysis, which preformed ribose-1-arsenate. Experiments with progressively delayed addition of DTT after BCX-1777 indicated that ribose-1-arsenate is short-lived with a half-life of 4 min. In conclusion, phosphorolytic enzymes, such as PNP, GAPDH, GPa, and PTA, promote thiol-dependent AsV reduction because they convert AsV into arsenylated products reducible by thiols more readily than AsV. In support of this view, reactivity studies using conceptual density functional theory reactivity descriptors (local softness, nucleofugality) indicate that reduction by thiols of the arsenylated metabolites is favored over AsV. PMID:19478237

Gregus, Zoltán; Roos, Goedele; Geerlings, Paul; Németi, Balázs

2009-08-01

291

Pravastatin sodium, a new HMG-CoA reductase inhibitor.  

Science.gov (United States)

The rate-limiting step in cholesterol biosynthesis is controlled by the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. Inhibitors of this enzyme lower serum cholesterol very efficiently by increasing cellular uptake of cholesterol-rich, low-density lipoproteins. Pravastatin, a derivative of mevastatin and in the same class as lovastatin, lowers total cholesterol concentrations by 20-30 percent in patients with hypercholesterolemia. In patients who also have hypertriglyceridemia, serum triglyceride levels are decreased. Detailed pharmacokinetic data and long-term adverse-effect experience with pravastatin are extremely limited. The issue of tissue-selectivity for pravastatin has given rise to the marketing terminology "second-generation" HMG-CoA reductase inhibitor, but any clinical advantage of pravastatin over other HMG-CoA reductase inhibitors remains to be demonstrated. PMID:1926908

Raasch, R H

1991-04-01

292

Regulation of aldehyde reductase expression by STAF and CHOP.  

Science.gov (United States)

Aldehyde reductase is involved in the reductive detoxification of reactive aldehydes that can modify cellular macromolecules. To analyze the mechanism of basal regulation of aldehyde reductase expression, we cloned the murine gene and adjacent regulatory region and compared it to the human gene. The mouse enzyme exhibits substrate specificity similar to that of the human enzyme, but with a 2-fold higher catalytic efficiency. In contrast to the mouse gene, the human aldehyde reductase gene has two alternatively spliced transcripts. A fragment of 57 bp is sufficient for 25% of human promoter activity and consists of two elements. The 3' element binds transcription factors of the Sp1 family. Gel-shift assays and chromatin immunoprecipitation as well as deletion/mutation analysis reveal that selenocysteine tRNA transcription activating factor (STAF) binds to the 5' element and drives constitutive expression of both mouse and human aldehyde reductase. Aldehyde reductase thus becomes the fourth protein-encoding gene regulated by STAF. The human, but not the mouse, promoter also binds C/EBP homologous protein (CHOP), which competes with STAF for the same binding site. Transfection of the human promoter into ethoxyquin-treated mouse 3T3 cells induces a 3.5-fold increase in promoter activity and a CHOP-C/EBP band appears on gel shifts performed with the 5' probe from the human aldehyde reductase promoter. Induction is attenuated in similar transfection studies of the mouse promoter. Mutation of the CHOP-binding site in the human promoter abolishes CHOP binding and significantly reduces ethoxyquin induction, suggesting that CHOP mediates stimulated expression in response to antioxidants in the human. This subtle difference in the human promoter suggests a further evolution of the promoter toward responsiveness to exogenous stress and/or toxins. PMID:14667815

Barski, Oleg A; Papusha, Victor Z; Kunkel, Gary R; Gabbay, Kenneth H

2004-01-01

293

Aldo keto reductases 1B in endocrinology and metabolism  

Directory of Open Access Journals (Sweden)

Full Text Available The aldose reductase (human AKR1B1/mouse Akr1b3 has been the focus of many research because of its role in diabetic complications. The starting point of these alterations is the massive entry of glucose in polyol pathway where it is converted into sorbitol by this enzyme. However, the issue of aldose reductase function in non-diabetic condition remains unresolved. Aldose reductase-like enzymes (AKR1B10, Akr1b7 and Akr1b8 are highly related isoforms often co-expressed with bona fide aldose reductase, making functional analysis of one or the other isoform a challenging task. AKR1B/Akr1b members share at least 65% protein identity and the general ability to reduce many redundant substrates such as aldehydes provided from lipid peroxidation, steroids and their by-products and xenobiotics in vitro. Based on these properties, AKR1B/Akr1b are generally considered as detoxifying enzymes. Considering that divergences should be more informative than similarities to help understanding their physiological functions, we chose to review specific hallmarks of each human/mouse isoforms by focusing on tissue distribution and specific mechanisms of gene regulation. Indeed, although the aldose reductase shows ubiquitous expression, aldose reductase-like proteins exhibit tissue-specific patterns of expression. We focused on 3 organs where certain isoforms are enriched, the adrenal gland, enterohepatic and adipose tissues and tried to connect recent enzymatic and regulation data with endocrine and metabolic functions of these organs. We presented recent mouse models showing unsuspected physiological functions in the regulation of glucido-lipidic metabolism and adipose tissue homeostasis. Beyond the widely accepted idea that AKR1B/Akr1b are detoxification enzymes, these recent reports provide growing evidences that they are able to modify or generate signal molecules. This conceptually shifts this class of enzymes from unenviable status of scavenger to upper class of messengers.

AntoineMartinez

2012-08-01

294

Expression and site-directed mutagenesis of human dihydrofolate reductase  

International Nuclear Information System (INIS)

A procaryotic high-level expression vector for human dihydrofolate reductase has been constructed and the protein characterized as a first step toward structure-function studies of this enzyme. A vector bearing the tac promoter, four synthetic oligodeoxynucleotides, and a restriction fragment from the dihydrofolate reductase cDNA were ligated in a manner which optimized the transcriptional and translational frequency of the enzyme mRNA. The reductase, comprising ca. 17% of the total soluble protein in the host bacteria, was purified to apparent homogeneity as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and characterized by amino acid composition, partial amino acid sequence, and steady-sate kinetic analysis. This expression vector has been used as a template for double-stranded plasmid DNA site-specific mutagenesis. Functional studies on a Cys-6 ? Ser-6 mutant enzyme support the contention that Cys-6 is obligatory for organomercurial activation of human dihydrofolate reductase. The Ser-6 mutant enzyme was not activated to any extent following a 24-h incubation with p-(hydroxymercuri)benzoate and nicotinamide adenine dinucleotide phosphate (reduced) (NADPH), whereas the k/sub cat/ for Cys-6 reductase increased 2-fold under identical conditions. The specific activities of the Cys-6 and Ser-6 enzymes were virtually identical as determined by methotrexate titration as were the K/sub m/ values for both dihydrofolate and NADPH. The Ser-6 mutant showed a decreased temperature stability and was more sensitive to inactivation by ?-chymotrypsin when compared to the wild-type enzyme. These results suggest that the Ser-6 mutant reductase is conformationally altered relative to the Cys-6 native enzyme

1988-05-17

295

Identification of viral polypeptides involved in pseudorabies virus ribonucleotide reductase activity.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We studied pseudorabies virus-induced ribonucleotide reductase and found that it exhibited biochemical properties very similar to those of herpes simplex virus reductase. A polyclonal rabbit antiserum (P9) directed against the carboxy terminus of subunit H2 polypeptide (38,000 daltons) of herpes simplex virus reductase neutralized the pseudorabies virus reductase, as well as the herpes simplex virus isozyme. This serum recognized two pseudorabies virus-specified polypeptides of 34,000 and 110...

Cohen, E. A.; Paradis, H.; Gaudreau, P.; Brazeau, P.; Langelier, Y.

1987-01-01

296

Purification and Characterization of a Novel Erythrose Reductase from Candida magnoliae  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Erythritol biosynthesis is catalyzed by erythrose reductase, which converts erythrose to erythritol. Erythrose reductase, however, has never been characterized in terms of amino acid sequence and kinetics. In this study, NAD(P)H-dependent erythrose reductase was purified to homogeneity from Candida magnoliae KFCC 11023 by ion exchange, gel filtration, affinity chromatography, and preparative electrophoresis. The molecular weights of erythrose reductase determined by sodium dodecyl sulfate-pol...

Lee, Jung-kul; Kim, Sang-yong; Ryu, Yeon-woo; Seo, Jin-ho; Kim, Jung-hoe

2003-01-01

297

The interplay between thiol-compounds against chromium (VI) in the freshwater green alga Monoraphidium convolutum: toxicology, photosynthesis, and oxidative stress at a glance.  

Science.gov (United States)

In this paper, the multifaceted Cr(VI) toxicity over the freshwater green alga Monoraphidium convolutum was assessed by concomitantly monitoring thiol-dependent redox balances, photosynthesis activity and growth-survival scores. Control group showed exponential growth rate at (5.78±0.29) division/day until 8th day with linear increasing chlorophyll a/protein ratios (CHLa/PROT) throughout the period. Cultures of M. convolutum were exposed for 5 days to Cr(VI) concentrations from 0 up to 100mg/L showing that CHLa/PROT ratios were sensibly affected, in agreement to the calculated LC(50,48 h) (5.38±0.72) mg/L from the concentration-response curve of cell mortality after 48 h. Regarding photosynthesis effects, Cr(VI) concentrations >1.0 mg/L showed significant increases in short-term (after 2 h) electron transfer rates (ETR) and quantum yields of photosystem II (?(PSII)), followed by subsequent decline of both parameters after 48 and 72 h. Biochemical analyses showed that maximal GSH concentrations in algal cultures were observed upon 1mg Cr(VI)/L and higher dichromate concentrations dramatically increased the activity of antioxidant GSH-dependent enzymes ascorbate peroxidase and glutathione reductase. However, no variation was observed in the cellular GSH levels, whereas GSSG and lipid peroxidation indexes abruptly increased upon 10 mg Cr(VI)/L exposure. Altogether, plant physiology, photosynthesis and biochemical data suggest that the GSH-dependent antioxidant system is capable to sustain M. convolutum viability through efficient photosynthesis activity and adequate antioxidant responses up to Cr(VI) concentrations of 1.0mg/L, when redox unbalances were first evidenced. PMID:22522782

Takami, R; Almeida, J V; Vardaris, C V; Colepicolo, P; Barros, M P

2012-08-15

298

The interplay between thiol-compounds against chromium (VI) in the freshwater green alga Monoraphidium convolutum: Toxicology, photosynthesis, and oxidative stress at a glance  

Energy Technology Data Exchange (ETDEWEB)

In this paper, the multifaceted Cr(VI) toxicity over the freshwater green alga Monoraphidium convolutum was assessed by concomitantly monitoring thiol-dependent redox balances, photosynthesis activity and growth-survival scores. Control group showed exponential growth rate at (5.78 {+-} 0.29) division/day until 8th day with linear increasing chlorophyll a/protein ratios (CHLa/PROT) throughout the period. Cultures of M. convolutum were exposed for 5 days to Cr(VI) concentrations from 0 up to 100 mg/L showing that CHLa/PROT ratios were sensibly affected, in agreement to the calculated LC{sub 50,48h} (5.38 {+-} 0.72) mg/L from the concentration-response curve of cell mortality after 48 h. Regarding photosynthesis effects, Cr(VI) concentrations >1.0 mg/L showed significant increases in short-term (after 2 h) electron transfer rates (ETR) and quantum yields of photosystem II ({Phi}{sub PSII}), followed by subsequent decline of both parameters after 48 and 72 h. Biochemical analyses showed that maximal GSH concentrations in algal cultures were observed upon 1 mg Cr(VI)/L and higher dichromate concentrations dramatically increased the activity of antioxidant GSH-dependent enzymes ascorbate peroxidase and glutathione reductase. However, no variation was observed in the cellular GSH levels, whereas GSSG and lipid peroxidation indexes abruptly increased upon 10 mg Cr(VI)/L exposure. Altogether, plant physiology, photosynthesis and biochemical data suggest that the GSH-dependent antioxidant system is capable to sustain M. convolutum viability through efficient photosynthesis activity and adequate antioxidant responses up to Cr(VI) concentrations of 1.0 mg/L, when redox unbalances were first evidenced.

Takami, R. [Postgraduate Program in Environmental Chemistry, CBS, Universidade Cruzeiro do Sul, 08060070, Sao Paulo, SP (Brazil); Almeida, J.V. [Department of Biochemistry, Instituto de Quimica, Universidade de Sao Paulo (IQ-USP), Sao Paulo, SP (Brazil); Vardaris, C.V. [Postgraduate Program in Environmental Chemistry, CBS, Universidade Cruzeiro do Sul, 08060070, Sao Paulo, SP (Brazil); Colepicolo, P. [Department of Biochemistry, Instituto de Quimica, Universidade de Sao Paulo (IQ-USP), Sao Paulo, SP (Brazil); Barros, M.P., E-mail: marcelo.barros@cruzeirodosul.edu.br [Postgraduate Program in Environmental Chemistry, CBS, Universidade Cruzeiro do Sul, 08060070, Sao Paulo, SP (Brazil)

2012-08-15

299

Pleiotropic effects of the HMG-CoA reductase inhibitors  

Directory of Open Access Journals (Sweden)

Full Text Available Christos G Mihos, Orlando SantanaColumbia University Division of Cardiology, Mount Sinai Heart Institute, Miami Beach, FL, USAAbstract: The HMG-CoA reductase inhibitors (statins are used extensively in the treatment of hyperlipidemia. They have also demonstrated a benefit in a variety of other disease processes. These secondary actions are known as pleiotropic effects. Our paper serves as a focused and updated discussion on the pleiotropy of statins and emphasizes the importance of randomized placebo-controlled trials to further elucidate this interesting phenomenon.Keywords: HMG-CoA inhibitors, pleiotropic, reductase, review, statins

Mihos CG

2011-04-01

300

Photochemical reactions of thiol-terminated self-assembled monolayers (SAMs) for micropatterning of gold nanoparticles and controlled surface functionality  

Energy Technology Data Exchange (ETDEWEB)

This paper reported a facile method for the patterning of gold nanoparticles (AuNPs) on SiO{sub 2}/Si by combining photochemical reaction and self-assembly techniques, and the conversion of surface functionality through thiol-ene click chemistry. The oxidation of terminal thiols in self-assembled monolayer of (3-mercaptopropyl)trimethoxysilane upon exposure to 254 nm UV light under ambient atmosphere was investigated. Chemically well-defined microstructures were obtained by UV irradiation through a mask, and subsequent immersion of the substrate into a dispersion of AuNPs resulted in site-specific assembly of AuNPs via Au-S covalent bond in the unexposed area. Thiol-ene 'click' reaction between surface thiol-group and alkene-containing molecules under illumination of 365 nm UV light was also demonstrated. X-ray photoelectron spectroscopy study indicated the successful conversion of surface functionality.

Han Xuemingyue; Wu Chong [National Center for Nanoscience and Technology, 11 Beiyitiao, Zhongguancun, Beijing 100190 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Sun Shuqing, E-mail: sun.shuqing@sz.tsinghua.edu.cn [Laboratory of Optical Imaging and Sensing, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)

2012-04-01

 
 
 
 
301

Modifying surface resistivity and liquid moisture management property of keratin fibers through thiol-ene click reactions.  

Science.gov (United States)

This paper reports on a new method for improving the antistatic and liquid moisture management properties of keratinous materials. The method involves the generation of thiols by controlled reduction of cystine disulfide bonds in keratin with tris(2-carboxyethyl) phosphine hydrochloride and subsequent grafting of hydrophilic groups onto the reduced keratin by reaction with an acrylate sulfonate or acrylamide sulfonate through thiol-ene click chemistry. The modified substrates were characterized with Raman spectroscopy and scanning electron microscopy and evaluated for their performance changes in liquid moisture management, surface resistivity, and wet burst strength. The results have revealed that the thiol-acrylate reaction is more efficient than the thiol-acrylamide reaction, and the keratinous substrate modified with an acrylate sulfonate salt exhibits significantly improved antistatic and liquid moisture management properties. PMID:24367993

Yu, Dan; Cai, Jackie Y; Church, Jeffrey S; Wang, Lijing

2014-01-22

302

Conjugate addition of thiols to p-benzoquinone monoketals. Attempts to prepare chiral synthetic equivalents of p-benzoquinone  

Energy Technology Data Exchange (ETDEWEB)

The conjugate addition of several thiols to achiral and chiral p-benzoquinone monoketals has been studied. A chiral synthetic equivalent of p-benzoquinone has been obtained in both enantiopure forms. (Author) 13 refs.

March, P. de; Escoda, M.; Figueredo, M.; Font, J.; Medrano, J. [Departamento de Quimica. Universitat Autonoma de Barcelon, Bellaterra, (Spain)

1997-09-01

303

Direct covalent attachment of DNA microarrays by rapid thiol-ene "click" chemistry.  

Science.gov (United States)

A rapid strategy for the covalent immobilization of DNA onto silicon-based materials using the UV-initiated radical thiol-ene reaction is presented in this study. Following this approach, thiol- and alkene-modified oligonucleotide probes were covalently attached in microarray format, reaching immobilization densities around 6 pmol·cm(-2). The developed methodology presents the advantages of spatially controlled probe anchoring (using a photomask), direct attachment without using cross-linkers (one-pot fashion), and short irradiation times (20 min). Using the described strategy, hybridization efficiencies up to 65% with full complementary strands were reached. The approach was evaluated by scoring single-base pair mismatches with discrimination ratios around 15. Moreover, the efficacy of the proposed DNA detection scheme is further demonstrated through the assay on a genomic target of bacterial Escherichia coli. PMID:24559310

Escorihuela, Jorge; Bañuls, María-José; Grijalvo, Santiago; Eritja, Ramón; Puchades, Rosa; Maquieira, Angel

2014-03-19

304

Pre-fermentation addition of grape tannin increases the varietal thiols content in wine.  

Science.gov (United States)

The recent finding that grape tannin may contain significant amount of S-glutathionylated (GSH-3MH) and S-cysteinylated (Cys-3MH) precursors of the varietal thiols 3-mercapto-1-hexanol and 3-mercaptohexyl acetate, characteristic of Sauvignon blanc wines, offers new opportunities for enhancing the tropical aroma in fermented beverages. In this study this new hypothesis was investigated: Müller Thurgau (17 samples) and Sauvignon blanc (15 samples) grapes were fermented with and without addition of a selected grape tannin. As expected, the tannin-added juices were higher in precursors, and they produced wines with increased free thiols. Preliminary informal sensory tests confirmed that in particular the Sauvignon wines produced with the tannin addition were often richer with increased "fruity/green" notes than the corresponding reference wines. This outcome confirms that grape tannin addition prior to fermentation can fortify the level of these compounds. PMID:25053028

Larcher, Roberto; Tonidandel, Loris; Román Villegas, Tomás; Nardin, Tiziana; Fedrizzi, Bruno; Nicolini, Giorgio

2015-01-01

305

Thiol Modification of Psyllium Husk Mucilage and Evaluation of Its Mucoadhesive Applications  

Science.gov (United States)

Thiol functionalization of psyllium was carried out to enhance its mucoadhesive potential. Thiolation of psyllium was achieved by esterification with thioglycolic acid. Thiolation was observed to change the surface morphology of psyllium from fibrous to granular and result in a slight increase in the crystallinity and swelling. Thiolated psyllium was found to contain 3.282?m moles of thiol groups/g of the polymer. Mucoadhesive applications of thiolated psylium were explored by formulating gels using metronidazole as the model drug. On comparative evaluation thiolated psyllium gels showed 3-fold higher mucoadhesive strength than the psyllium gels as determined by modified physical balance using chicken buccal pouch. The results of in vitro release study revealed that thiolated psyllium gels provided a prolonged release of metronidazole. Further, the psyllium and thiolated psyllium gels were found to release the drug following first-order kinetics by combination of polymer relaxation and diffusion through the matrix.

Bhatia, Meenakshi

2013-01-01

306

Surface Grafting of Vinyl-Functionalized Poly(fluorene)s via Thiol-Ene Click Chemistry.  

Science.gov (United States)

Thiol-ene chemistry is used for the surface grafting of vinyl-functionalized poly(fluorene) derivatives onto substrates containing free surface thiol groups. The grafting reaction proceeds in a matter of minutes under UV irradiation without photoinitiator, and the resulting surface-bound, solvent-impervious conjugated polymers retain their characteristic optoelectronic properties. End-chain grafted poly(fluorene)s reach greater surface densities than their side-chain grafted counterparts and show less blue-shifting of photoluminescence upon grafting, suggesting that chain end-grafted conjugated polymers experience less disruption of their extended conjugation and adopt a more brush-like surface conformation. Surface grafted poly(fluorene)s showed facile photopatterning, and thin film transistors with semiconducting polymers directly grafted to the dielectric layer showed performances directly comparable to conventional self-assembled layers of performance-improving alkylsilanes. PMID:24689503

Davis, Andrew R; Carter, Kenneth R

2014-04-22

307

Magnetically controlled bioelectrocatalytic system based on ferrocene-tagged magnetic nanoparticles by thiol-ene reaction  

International Nuclear Information System (INIS)

A simple and versatile method for the introduction of electrochemical moieties onto the surface of Fe3O4 nanoparticles has been developed based on UV-induced thiol-ene click chemistry. Thiol-terminated Fe3O4 nanoparticles were synthesized and further reacted with vinylferrocence under 365 nm UV. The functionalized magnetic nanoparticles were characterized using a powder X-ray diffractometer (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscope (FTIR), and vibrating sample magnetometer (VSM). The resulting nanocomposites possess of magnetism and electrochemical activity. Based on the superparamagnetism of Fe3O4 nanoparticles and the electrocatalytic activity of ferrocene, a recyclable, magneto-controlled bioelectrocatalytic system for glucose oxidation is developed. The switching of the biocatalytic activity and recyclable usage of the ferrocene functionalized nanoparticles by means of the external magnet could provide a simple, green and convenient strategy for bioelectrosensing.

2012-05-01

308

Superhydrophobic hybrid inorganic-organic thiol-ene surfaces fabricated via spray-deposition and photopolymerization.  

Science.gov (United States)

We report a simple and versatile method for the fabrication of superhydrophobic inorganic-organic thiol-ene coatings via sequential spray-deposition and photopolymerization under ambient conditions. The coatings are obtained by spray-deposition of UV-curable hybrid inorganic-organic thiol-ene resins consisting of pentaerythritol tetra(3-mercaptopropionate) (PETMP), triallyl isocyanurate (TTT), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (TMTVSi), and hydrophobic fumed silica nanoparticles. The spray-deposition process and nanoparticle agglomeration/dispersion provide surfaces with hierarchical morphologies exhibiting both micro- and nanoscale roughness. The wetting behavior, dependent on the concentration of TMTVSi and hydrophobic silica nanoparticles, can be varied over a broad range to ultimately provide coatings with high static water contact angles (>150°), low contact angle hysteresis, and low roll off angles (glass, paper, stone, and cotton fabric. PMID:23410965

Sparks, Bradley J; Hoff, Ethan F T; Xiong, Li; Goetz, James T; Patton, Derek L

2013-03-13

309

Photocured thiol-ene based optical fluorescence sensor for determination of gold(III).  

Science.gov (United States)

This study describes the preparation and the characterization of a new thiol-ene based polymeric fluorescence sensor by photo initiated polymerization of trimethylolpropane tris(3-mercaptopropionate), 2-hydroxyethylacrylate, and 2,4,6-triallyloxy-1,3,5-triazine which are used as monomers and also a photo initiator (2,2-dimethoxy-2-phenylacetophenone) for its usage as optical sensor for gold ions. The thiol-ene based polymeric membrane sensor was characterized by using attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). The response characteristics of the sensors including dynamic range, pH effect, response time, and the effect of foreign ions were investigated. Fluorescence spectra showed that the excitation/emission maxima of the membrane were at 379/425 nm, respectively. PMID:24491784

Cubuk, Soner; Kahraman, Memet Vezir; Yetimo?lu, Ece Kök; Kenan, Sibel

2014-02-17

310

Thiol-Ene Based Polymer Waveguides Fabricated By Uv-Assisted Soft Lithography For Optofluidic Applications  

DEFF Research Database (Denmark)

In this paper, a thiol-ene based polymer waveguide, defined by UV-assisted soft lithography, is designed, fabricated and characterized. Waveguides are formed by filling microfluidic channels with a high refractive index liquid mixture of â??thiolâ?? and â??eneâ?? monomers (e.g., trimethylolpropane tris(3-mercaptopropionate) = â??thiolâ??, and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione = â??eneâ??), which can be cured by UV exposure into a solid polymer. The waveguides demonstrated good confinement of light, and a propagation loss of 0.5 dB/cm was obtained. To our best knowledge, this is the first report to employ thiol-ene based polymers as waveguide core materials for potential optofluidic applications.

Zhuang, Guisheng; Jensen, Thomas Glasdam

2011-01-01

311

Synthesis and characterization of thiol-functionalized polymer as binder in conductive ink  

Science.gov (United States)

The technology of electrical printing has received industrial and scientific attention due to wide variety of application such as sensors, radio frequency identification cards (RFIDs), flexible display, and flexible solar cell. Especially a roll to roll gravure printing technique has been useful for mass production of electrical products. For the more high quality of conductive ink, the compatibility of organic binder and inorganic filler is very important. In this study, Thiol-functionalized polymer and core-shell conductive nanoparticles were used as the binder and filler. The thiol moieties in binder contribute to functionality of the synthesized polymer. Also, the conductivity and viscosity of synthesized ink and compatibility of filler with binder were characterized in various conditions.

Lee, Jungmin; Varadan, Vijay K.

2011-03-01

312

Rapid photochemical surface patterning of proteins in thiol-ene based microfluidic devices  

DEFF Research Database (Denmark)

The suitable optical properties of thiolâ??ene polymers combined with the ease of modifying their surface for the attachment of recognition molecules make them ideal candidates in many biochip applications. This paper reports the rapid one-step photochemical surface patterning of biomolecules in microfluidic thiolâ??ene chips. This work focuses on thiolâ??ene substrates featuring an excess of thiol groups at their surface. The thiolâ??ene stoichiometric composition can be varied to precisely control the number of surface thiol groups available for surface modification up to an average surface density of 136 ! 17 SH nm"2. Biotin alkyne was patterned directly inside thiolâ??ene microchannels prior to conjugation with fluorescently labelled streptavidin. The surface bound conjugates were detected by evanescent waveinduced fluorescence (EWIF), demonstrating the success of the grafting procedure and its potential for biochip applications.

Lafleur, Josiane P.; Jensen, Thomas Glasdam

2013-01-01

313

Colorimetric/fluorogenic detection of thiols by N-fused porphyrin in water.  

Science.gov (United States)

A water-soluble derivative of N-fused porphyrin (NFP) possessing four cationic side-arms (pPyNFP) serves as a unique class of colorimetric/fluorogenic reporters that selectively react with biothiols in aquaous media to afford N-confused porphyrin (NCP) derivatives, while other nucleophilic amino acids were inert under a wide range of pH conditions. Owing to the large difference of the optical properties between NCP and NFP, the transformation enabled selective detection of biothiols in colorimetric/fluorogenic manner, especially in the near-infrared region. To the best our knowledge, this is the first example of porphyrin-based thiol detection systems that use the direct attack of thiol group on the optical reporter. PMID:24051075

Ikawa, Yoshiya; Touden, Satoshi; Katsumata, Sho; Furuta, Hiroyuki

2013-11-01

314

Thiol modification of psyllium husk mucilage and evaluation of its mucoadhesive applications.  

Science.gov (United States)

Thiol functionalization of psyllium was carried out to enhance its mucoadhesive potential. Thiolation of psyllium was achieved by esterification with thioglycolic acid. Thiolation was observed to change the surface morphology of psyllium from fibrous to granular and result in a slight increase in the crystallinity and swelling. Thiolated psyllium was found to contain 3.282?m moles of thiol groups/g of the polymer. Mucoadhesive applications of thiolated psylium were explored by formulating gels using metronidazole as the model drug. On comparative evaluation thiolated psyllium gels showed 3-fold higher mucoadhesive strength than the psyllium gels as determined by modified physical balance using chicken buccal pouch. The results of in vitro release study revealed that thiolated psyllium gels provided a prolonged release of metronidazole. Further, the psyllium and thiolated psyllium gels were found to release the drug following first-order kinetics by combination of polymer relaxation and diffusion through the matrix. PMID:24348147

Bhatia, Meenakshi; Ahuja, Munish

2013-01-01

315

Long-lived ¹H nuclear spin singlet in dimethyl maleate revealed by addition of thiols.  

Science.gov (United States)

Nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) have become important techniques in many research areas. One major limitation is the relatively low sensitivity of these methods, which recently has been addressed by hyperpolarization. However, once hyperpolarization is imparted on a molecule, the magnetization typically decays within relatively short times. Singlet states are well isolated from the environment, such that they acquire long lifetimes. We describe herein a model reaction for read-out of a hyperpolarized long-lived state in dimethyl maleate using thiol conjugate addition. This type of reaction could lend itself to monitoring oxidative stress or hypoxia by sensitive detection of thiols. Similar reactions could be used in biosensors or assays that exploit molecular switching. Singlet lifetimes of about 4.7?min for (1)H spins in [D4]MeOH are seen in this system. PMID:24623618

Zhang, Yuning; Soon, Pei Che; Jerschow, Alexej; Canary, James W

2014-03-24

316

Liquid-phase thermal condensation of aromatic and heteroaromatic thiols with. beta. -chloro and. beta. -bromostyrene  

Energy Technology Data Exchange (ETDEWEB)

Aromatic thiols and 2-thiophenethiol react with ..beta..-chloro- and ..beta..-bromostyrene when heated to form the corresponding 1-phenyl-2-aryl(thienyl)thioethenes. The reaction begins at 80/sup 0/C and takes place effectively and strictly stereospecifically at 140-160/sup 0/C. The yield of the respective vinyl sulfides amounts to 70-95%. ..beta..-Bromostyrene reacts with thiophenol more slowly than ..beta..-chlorostyrene, and this is due to the inhibiting action of the hydrogen bromide, which acts as a trap for the thiyl radicals and gives rise to decomposition of the obtained 1-phenyl-2-phenylthioethene. Among the investigated thiols 2-thiophenethiol has the lowest reactivity.

Kuznetsova, M.A.; Korchevin, N.A.; Deryagina, E.N.; Voronkov, M.G.

1987-11-20

317

Labeling Thiols on Proteins, Living Cells, and Tissues with Enhanced Emission Induced by FRET  

Science.gov (United States)

Using N-(2-Aminoethyl)maleimide-cysteine(StBu) (Mal-Cys) as a medium, protein thiols were converted into N-terminal cysteines. After a biocompatible condensation reaction between the N-terminal cysteine and fluorescent probe 2-cyanobenzothiazole-Gly-Gly-Gly-fluorescein isothiocyanate (CBT-GGG-FITC), a new fluorogenic structure Luciferin-GGG-FITC was obtained. The latter exhibits near one order of magnitude (7 folds) enhanced fluorescence emission compared to the precursor moiety due to fluorescence resonance energy transfer (FRET) effect between the newly formed luciferin structure and the FITC motif. Theoretical investigations revealed the underlying mechanism that satisfactorily explained the experimental results. With this method, enhanced fluorescence imaging of thiols on proteins, outer membranes of living cells, translocation of membrane proteins, and endothelial cell layers of small arteries was successfully achieved.

Yuan, Yue; Wang, Xijun; Mei, Bin; Zhang, Dongxin; Tang, Anming; An, Linna; He, Xiaoxiao; Jiang, Jun; Liang, Gaolin

2013-12-01

318

Synthesis and Biological Evaluation of Novel Benzothiazole-2-thiol Derivatives as Potential Anticancer Agents  

Directory of Open Access Journals (Sweden)

Full Text Available A series of novel benzothiazole-2-thiol derivatives were synthesized and their structures determined by 1H-NMR, 13C-NMR and HRMS (ESI. The effects of all compounds on a panel of different types of human cancer cell lines were investigated. Among them, pyridinyl-2-amine linked benzothiazole-2-thiol compounds 7d, 7e, 7f and 7i exhibited potent and broad-spectrum inhibitory activities. Compound 7e displayed the most potent anticancer activity on SKRB-3 (IC50 = 1.2 nM, SW620 (IC50 = 4.3 nM, A549 (IC50 = 44 nM and HepG2 (IC50 = 48 nM and was found to induce apoptosis in HepG2 cancer cells.

Luo-Ting Yu

2012-03-01

319

Occurrence of odorant polyfunctional thiols in the Super Alpha Tomahawk hop cultivar. Comparison with the thiol-rich Nelson Sauvin bitter variety.  

Science.gov (United States)

Tomahawk hop (Humulus lupulus) is a recently developed Super Alpha cultivar (14-18% ?-acids w/w), already widely used by brewers to impart bitterness and a citrus-like aroma to beer. By comparison with two bitter varieties (Nelson Sauvin and Nugget) and two aromatic ones (Cascade and Saaz), the Tomahawk cultivar showed a very particular terpenoid profile, rich in both ?- and ?-selinenes (>600 mg/kg IST equiv in total), methyl geranate (>40 mg/kg IST equiv), and geraniol (>200 mg/kg). Tomahawk also proved to contain a wide variety of odorant polyfunctional thiols. The major ?-sulfanyl acetate, 3-sulfanyl-2-ethylpropyl acetate, newly identified here, was found at similar levels in the famous Sauvignon-like Nelson Sauvin and Tomahawk varieties (15-44 ?g/kg IST equiv). On the other hand, lower levels of total ?-sulfanyl alcohols were measured in Tomahawk, although 3-sulfanylhexan-1-ol was found at a similar level and the 3-sulfanyl-4-methylpentan-1-ol previously claimed to be specific to the Nelson Sauvin variety was also evidenced in the Super Alpha cultivar (9-13 ?g/kg IST equiv). As revealed by boiling and fermentation, Tomahawk hop also contains very interesting bound polyfunctional thiols that should be investigated for better use by brewers. PMID:21740044

Gros, Jacques; Nizet, Sabrina; Collin, Sonia

2011-08-24

320

Additional pathways of S-conjugate formation during the interaction of thiols with nitrosoarenes bearing pi-donating substituents.  

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During the well-established reaction pathways of nitrosoarenes interacting with thiols, a reactive N-(thiol-S-yl)-arylamine cation was implicated in the so-called rearrangement reaction which transforms the semimercaptal to the sulfinamide. In the case of nitrosoarenes with pi-donating substituents, this cationic transition state includes resonance structures bearing the positive charge in 2 and 4 position, thereby facilitating the attack of nucleophiles to the aromatic ring. Investigating th...

1994-01-01

 
 
 
 
321

Labelling by 3H-N-ethylmaleimide of diamide-oxidized thiol groups in sheep red blood cell (SRBC) membranes  

International Nuclear Information System (INIS)

Exposure of SRBC to the thiol oxidant diamide activates K:Cl cotransport, reversed upon metabolic restoration of cellular glutathione suggesting redox control of the K:Cl cotransporter, as well as by subsequent exposure to dithiothreitol (DTT). The thiols crucial for activation may be either on the transporter or on a membrane or cytoplasmic regulator. To test this hypothesis, the authors attempted to label with 3H-N-ethylmaleimide (3H-NEM) the thiols protected by diamide oxidation and reduced subsequently by DTT. SRBC were first treated with a diamide concentration activating K:Cl cotransport, followed by a second exposure to unlabeled (cold) NEM to block any non-oxidized thiol, and then hemolyzed to obtain white ghosts. The ghosts were again treated with cold NEM and after reduction by DTT exposed to 3H-NEM with and without cold NEM. Saturation labelling by 3H-NEM of diamide protected groups occurred in the range of CTT concentrations inactivating the diamide-stimulated K:Cl cotransport. Saturation labelling with 3H-NEM occurred at about 25?M NEM suggesting a Ki of less than 10?M NEM. The number of diamide protected thiols was about 5-10,000/cell membrane. At 100?M 3H-NEM, SRBC not treated with diamide possess at least 100,000 thiols cell and this number is likely to rise by tenfold at higher NEM concentrations. Thus, diamide protected about 1/1,000 of the membrane thiols in both genetically low and high K SRBC, assayed under conditions where K:Cl cotransport is activated in intact cells. Therefore, at least some of the thiols crucial for potential regulation of K:Cl cotransport reside within the plasma membrane

1991-03-11

322

Thiol depletion can selectively enhance melphalan toxicity: in vitro studies with hypoxic cell sensitizers and buthionine sulfoximine  

International Nuclear Information System (INIS)

The potential for the combined use of 2 mechanistically different types of thiol altering agents at non-cytotoxic doses of either drug using several combinations of treatments on V-79-379 A hamster cells is discussed. The importance of thiol depletions and regeneration to the vulnerability and repair capabilities of cells exposed to Melphalan was determined in the hopes of understanding the chemotherapeutic strategy necessary for utilizing this approach in vivo

1984-07-01

323

Thiol-metabolizing proteins and endothelial redox state: differential modulation of eNOS and biopterin pathways  

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The intracellular redox state is stringently maintained by thiol-based antioxidants to establish a balance for the physiological and pathophysiological roles of reactive oxygen species. The relative contributions of the thioredoxin (Trx) and glutathione/glutaredoxin systems to intracellular redox balance are incompletely understood, as are the consequences of altered thiol metabolism on endothelial nitric oxide (NO) synthase (eNOS) and NO-dependent pathways in the endothelium. We designed dup...

Sugiyama, Toru; Michel, Thomas

2010-01-01

324

Copper and ceruloplasmin levels in relation to total thiols and GST in type 2 diabetes mellitus patients  

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Presence of oxidative stress in type 2 diabetes mellitus (DM) is well proved. Current study was undertaken to know the relation between fasting plasma glucose (FPG) and copper along with antioxidants like total thiols and ceruloplasmin, and antioxidant enzyme glutathione S transferase (GST). The study group consisted of a total of 201 subjects which included nondiabetic healthy control subjects (n = 78) and diabetic patients (n = 123). Plasma total thiols, GST, copper and ceruloplasmin levels...

Sarkar, A.; Dash, S.; Barik, B. K.; Muttigi, Manjunatha S.; Kedage, V.; Shetty, J. K.; Prakash, M.

2010-01-01

325

A study of oxidative stress, thiol proteins and role of vitamin E supplementation in chronic obstructive pulmonary disease (COPD  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Lipid peroxide plays an important role in inflammatory lung disease. Increased epithelial permeability produced by cigarette smoke is likely to be mediated through depletion of thiol proteins. Imbalance between oxidants and thiol proteins is also an established fact in these patients. Materials & methods: In the present study 30 healthy non-smokers were served as controls and 20 patients with stable COPD were included. Their base line clinical examination, Malondialdehyde (MDA as an oxidant, alpha tocopherol and erythrocyte superoxide dismutase (SOD as an antioxidants and thiol proteins levels were measured. All above parameters were repeated after 12 weeks of supplementation with 400 IU of vitamin E daily. Results: We observed that the mean malondialdehyde levels in these patients at base line were high (p<0.001 than Control Plasma alpha-tocopherol, SOD and thiol proteins levels were low (p<0.001 in the patients compared to controls. Exogenous vitamin E (400 IU twice daily Supplementation did not bring about any significant change in plasma Erythrocyte Superoxide Dismutase and vitamin E. But slight increase in the plasma thiol proteins levels was seen. The present study shows that initially the plasma lipid peroxide (MDA levels were high antioxidant (alpha- tocopherol, SOD and thiol proteins were low in patients with COPD. Exogenous supplementation with vitamin E increases slightly thiol proteins levels and brings down the levels of MDA showing attenuation of further damage. Conclusion: Our study confirmed the existence of oxidative stress and and the augmentation of antioxidant defenses as shown by slight increase in thiol proteins level. The antioxidant therapy is adjunct in lung disease patients and opens a promising field in prevention of oxidative stress related complications in these patients.

Anita M. Raut

2013-04-01

326

Ruthenium(III Chloride Catalyzed Acylation of Alcohols, Phenols, and Thiols in Room Temperature Ionic Liquids  

Directory of Open Access Journals (Sweden)

Full Text Available Ruthenium(III chloride-catalyzed acylation of a variety of alcohols, phenols, and thiols was achieved in high yields under mild conditions (room temperature in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]. The ionic liquid and ruthenium catalyst can be recycled at least 10 times. Our system not only solves the basic problem of ruthenium catalyst reuse, but also avoids the use of volatile acetonitrile as solvent.

Mingzhong Cai

2009-09-01

327

System B0,+ and the Transport of Thiol-S-Conjugates of Methylmercury  

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Methylmercury (CH3Hg+) is a clinically relevant toxicant that is the most abundant form of mercury found in the environment. After exposure, it accumulates in the kidneys, liver, and central nervous system. The mechanisms by which this toxicant is taken up by target cells are only now beginning to be understood. Some experimental data support a hypothesis involving molecular mimicry, whereby thiol conjugates of methylmercury (especially a cysteine S-conjugate) mimic one or more amino acids an...

Bridges, Christy C.; Zalups, Rudolfs K.

2006-01-01

328

Glutathione revisited: a vital function in iron metabolism and ancillary role in thiol-redox control  

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Glutathione contributes to thiol-redox control and to extra-mitochondrial iron–sulphur cluster (ISC) maturation. To determine the physiological importance of these functions and sort out those that account for the GSH requirement for viability, we performed a comprehensive analysis of yeast cells depleted of or containing toxic levels of GSH. Both conditions triggered an intense iron starvation-like response and impaired the activity of extra-mitochondrial ISC enzymes but did not impact thi...

Kumar, Chitranshu; Igbaria, Aeid; D Autreaux, Benoi?t; Planson, Anne-gae?lle; Junot, Christophe; Godat, Emmanuel; Bachhawat, Anand K.; Delaunay-moisan, Agne?s; Toledano, Michel B.

2011-01-01

329

Inhibition of metallo-beta-lactamases by a series of mercaptoacetic acid thiol ester derivatives.  

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A series of mercaptoacetic acid thiol esters have been identified as metallo-beta-lactamase inhibitors. Electrospray mass spectrometry (ESMS) has shown that irreversible inhibition of the Bacillus cereus II metallo-beta-lactamase by SB214751, SB214752, and SB213079 was concomitant with a 90-Da increase in mass of the enzyme. Tryptic digestion of the B. cereus II inhibited with SB214751 illustrated that the peptide fragment, containing the only cysteine of the enzyme, had undergone a mass incr...

1997-01-01

330

Kinetics of alpha hydrogen abstractions in thiols, sulfides and thiocarbonyl compounds  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Hydrogen abstraction reactions involving organosulfur compounds play an important role in many industrial, biological and atmospheric processes. Despite their chemical relevance, little is known about their kinetics. In this work a group additivity model is developed that allows predicting the Arrhenius parameters for abstraction reactions of alpha hydrogen atoms from thiols, alkyl sulfides, alkyl disulfides and thiocarbonyl compounds by carbon-centered radicals at temperatures ranging from 3...

Vandeputte, Aa?ron; Sabbe, Maarten; Reyniers, Marie-franc?oise; Marin, Guy

2012-01-01

331

Serum paraoxonase activity and protein thiols in chronic renal failure patients  

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Serum paraoxonase is known to prevent low-density lipoprotein oxidation and atherogenesis. Association of paraoxonase with the oxidative status and lipid profile in chronic renal failure (CRF) patients on conservative management and those on chronic maintenance hemodialysis was analyzed in the present study. Serum paraoxonase, protein thiols, lipid hydroperoxides, lipid profile, creatinine and albumin levels were estimated by spectrophotometric methods in CRF patients on conservative manageme...

Prakash, M.; Shetty, J. K.; Rao, L.; Sharma, S.; Rodrigues, A.; Prabhu, R.

2008-01-01

332

EVALUATION OF THIOL-BASED ANTIOXIDANT THERAPEUTICS IN CYSTIC FIBROSIS SPUTUM: FOCUS ON MYELOPEROXIDASE  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Neutrophil-dependent reactions catalyzed by myeloperoxidase (MPO) are thought to play important roles in the pulmonary pathobiology of cystic fibrosis (CF). Aerosolized thiol antioxidants such as glutathione (GSH) and N-acetylcysteine (NAC) are currently being utilized as therapeutics to modify CF respiratory tract oxidative processes. We hypothesized that MPO in CF airway lining fluids may be a target of such therapeutics. MPO activity in sputum from 21 adult CF patients was found to be inve...

Vasu, Vihas T.; Cruz, Sharon J.; Houghton, Jessica S.; Hayakawa, Keri A.; Morrissey, Brian M.; Cross, Carroll E.; Eiserich, Jason P.

2011-01-01

333

Protection against cerebral malaria by the low-molecular-weight thiol pantethine  

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We report that administration of the low-molecular-weight thiol pantethine prevented the cerebral syndrome in Plasmodium berghei ANKA-infected mice. The protection was associated with an impairment of the host response to the infection, with in particular a decrease of circulating microparticles and preservation of the blood–brain barrier integrity. Parasite development was unaffected. Pantethine modulated one of the early steps of the inflammation–coagulation cascade, i.e., the transbila...

Penet, Marie-france; Abou-hamdan, Mhamad; Coltel, Nicolas; Cornille, Emilie; Grau, Georges E.; Reggi, Max; Gharib, Bouchra

2008-01-01

334

Regulation of pyruvate dehydrogenase kinase activity by protein thiol-disulfide exchange.  

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Endogenous kinase activity of highly purified pyruvate dehydrogenase complex from bovine kidney is markedly inhibited by N-ethylmaleimide and by certain disulfides. Inhibition by disulfides is highly specific and is reversed by thiols. 5,5'-Dithiobis(2-nitrobenzoate) is the most potent inhibitor, showing significant inhibition at a concentration as low as 1 microM. Cystamine, oxidized glutathione, pantethine, lipoic acid, lipoamide, ergothionine, insulin, oxytocin, and vasopressin were ineffe...

Pettit, F. H.; Humphreys, J.; Reed, L. J.

1982-01-01

335

A Novel Bifunctional Maleimido CHX-A” Chelator for Conjugation to Thiol-Containing Biomolecules  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A novel bifunctional maleimido CHX-A”-DTPA chelator 5 was developed and conjugated to the monoclonal antibody trastuzumab (Herceptin) and subsequently radiolabeled with 111In. The resulting 111In labeled immunoconjugate 2 was demonstrated to bind to SKOV3 ovarian cancer cells comparably to an isothiocyanato CHX-A” DTPA modified native trastuzumab, 1. Through efficient thiol-maleimide chemistry, antibodies, peptides or other targeting vectors can now be modified with an established radioac...

Xu, Heng; Baidoo, Kwamena E.; Wong, Karen J.; Brechbiel, Martin W.

2008-01-01

336

Thiol-functionalized silica colloids, grains, and membranes for irreversible adsorption of metal(oxide) nanoparticles  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thiol-functionalization is described for silica surfaces from diverging origin, including commercial silica nanoparticles and Stöber silica as well as silica structures provided by porous glasses and novel polymer-templated silica membranes. The functionalization allows in all cases for the irreversible binding of metal(oxide) particles from a solution. Examples are the adsorption of CoFe2O4 particles for the preparation of magnetizable silica colloids and silica structures, and gold nanopar...

Claesson, E. M.; Philipse, A. P.

2007-01-01

337

Comparison of Hydrazone Heterobifunctional Crosslinking Agents for Reversible Conjugation of Thiol-Containing Chemistry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Reversible covalent conjugation chemistries that allow site- and condition-specific coupling and uncoupling reactions are attractive components in nanotechnologies, bioconjugation methods, imaging and drug delivery systems. Here, we compare three heterobifunctional crosslinkers, containing both thiol- and amine- reactive chemistry, to form pH-labile hydrazones with hydrazide derivatives of the known and often published water-soluble polymer, poly[N-(2-hydroxypropyl methacrylamide)] (pHPMA), w...

Christie, R. James; Anderson, Diana J.; Grainger, David W.

2010-01-01

338

Spectro fluorimetric detection of glutathione and thiol-containing compounds in various environmental matrices  

Energy Technology Data Exchange (ETDEWEB)

Low-molecular-weight hydrophilic thiols (cysteine, glutathione-GSH-, thioglycolic acid, 3-mercaptopropionic acid,...) have received much attention owing to their biochemical and environmental importance. These compounds serve as a key step in the formation of high-molecular-weight organic matter fractions, as strong ligands for transition metals and are thus involved in mobilization of metals in vegetal (phyto remediation through phytochelatin synthesis, for instance), aquatic or terrestrial environments through complexation reactions. (Author)

Palacio-Barco, E.; Robert-Peillard, F.; Boudenne, J. L.; Dudal, Y.; Coulomb, B.

2009-07-01

339

Spectro fluorimetric detection of glutathione and thiol-containing compounds in various environmental matrices  

International Nuclear Information System (INIS)

Low-molecular-weight hydrophilic thiols (cysteine, glutathione-GSH-, thioglycolic acid, 3-mercaptopropionic acid,...) have received much attention owing to their biochemical and environmental importance. These compounds serve as a key step in the formation of high-molecular-weight organic matter fractions, as strong ligands for transition metals and are thus involved in mobilization of metals in vegetal (phyto remediation through phytochelatin synthesis, for instance), aquatic or terrestrial environments through complexation reactions. (Author)

2008-09-00

340

Characterization of plasma thiol redox potential in a common marmoset model of aging?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Due to its short lifespan, ease of use and age-related pathologies that mirror those observed in humans, the common marmoset (Callithrix jacchus) is poised to become a standard nonhuman primate model of aging. Blood and extracellular fluid possess two major thiol-dependent redox nodes involving cysteine (Cys), cystine (CySS), glutathione (GSH) and glutathione disulfide (GSSG). Alteration in these plasma redox nodes significantly affects cellular physiology, and oxidation of the plasma Cys/CyS...

2013-01-01

 
 
 
 
341

Profiling protein thiol oxidation in tumor cells using sulfenic acid-specific antibodies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Hydrogen peroxide (H2O2) functions as a second messenger that can activate cell proliferation through chemoselective oxidation of cysteine residues in signaling proteins. The connection between H2O2 signaling, thiol oxidation, and activation of growth pathways has emerged as fertile ground for the development of strategies for cancer treatment. Central to achieving this goal is the development of tools and assays that facilitate characterization of the molecular events associated with tumorig...

Seo, Young Ho; Carroll, Kate S.

2009-01-01

342

Requirements for heme and thiols for the nonenzymatic modification of nitrotyrosine  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Peroxynitrite-dependent formation of nitrotyrosine has been associated with inactivation of various enzymes and proteins possessing functionally important tyrosines. We have previously reported an enzymatic activity modifying the nitrotyrosine residues in nitrated proteins. Here we are describing a nonenzymatic reduction of nitrotyrosine to aminotyrosine, which depends on heme and thiols. Various heme-containing proteins can mediate the reaction, although the reaction also is catalyzed by hem...

Balabanli, Barbaros; Kamisaki, Yoshinori; Martin, Emil; Murad, Ferid

1999-01-01

343

Ruthenium(III) Chloride Catalyzed Acylation of Alcohols, Phenols, and Thiols in Room Temperature Ionic Liquids  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ruthenium(III) chloride-catalyzed acylation of a variety of alcohols, phenols, and thiols was achieved in high yields under mild conditions (room temperature) in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]). The ionic liquid and ruthenium catalyst can be recycled at least 10 times. Our system not only solves the basic problem of ruthenium catalyst reuse, but also avoids the use of volatile acetonitrile as solvent.

Zhiwen Xi; Wenyan Hao; Pingping Wang; Mingzhong Cai

2009-01-01

344

Chemical synthesis of oligonucleotides containing a free sulphydryl group and subsequent attachment of thiol specific probes.  

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Oligonucleotides containing a free sulphydryl group at their 5'-termini have been synthesised and further derivatised with thiol specific probes. The nucleotide sequence required is prepared using standard solid phase phosphoramidite techniques and an extra round of synthesis is then performed using the S-triphenylmethyl O-methoxymorpholinophosphite derivatives of 2-mercaptoethanol, 3-mercaptopropan (1) ol or 6-mercaptohexan (1) ol. After cleavage from the resin and removal of the phosphate a...

1985-01-01

345

In vivo therapeutic potential of combination thiol depletion and alkylating chemotherapy.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of administering the thiol modulating agent buthionine sulfoximine (BSO) in conjunction with alkylating chemotherapy was investigated in vivo in the mouse KHT sarcomas and bone marrow stem cells. Tumour response to treatment was assessed by an in vivo to in vitro excision assay and bone marrow survival was determined in vitro by CFU-GM. Glutathione (GSH) depletion and recovery kinetics were determined at various times after treatment using high performance liquid chromatography (HP...

Siemann, D. W.; Beyers, K. L.

1993-01-01

346

Facile fabrication of redox-responsive thiol-containing drug delivery system via RAFT polymerization.  

Science.gov (United States)

A novel kind of redox-responsive polymeric drug delivery system has been designed and prepared successfully through the coupling of the multithiol branched polymers and thiol-containing drugs. The branched poly((S-(4-vinyl) benzyl S'-propyltrithiocarbonate)-co-(poly(ethylene glycol) methacrylate)) (poly(VBPT-co-PEGMA)) was synthesized by one-pot reaction via reversible addition-fragmentation chain transfer (RAFT) copolymerization. Subsequently, the hydrophobic thiol-containing anticancer drug 6-mercaptopurine (MP) was conjugated to poly(VBPT-co-PEGMA) by thiol-disulfide exchange reaction, resulting in the formation of poly(VBPT-co-PEGMA)-S-S-MP conjugate. Due to its amphiphilicity, poly(VBPT-co-PEGMA)-S-S-MP conjugate self-assembled into amphiphilic micelles in aqueous solution. Under a reductive environment, the disassembly of polymeric micelles resulted in the MP release. Flow cytometry and confocal laser scanning microscopy (CLSM) measurements demonstrated that the poly(VBPT-co-PEGMA)-S-S-MP micelles could be taken up by Raji cells (a Burkitt lymphoma cell line). The viability of the Raji cells incubated with the glutathione (GSH) mediated poly(VBPT-co-PEGMA)-S-S-MP micelles was investigated by Cell Counting Kit-8 (CCK-8) assay. The experimental results showed that the viability of the glutathione monoester (GSH-OEt) pretreated cells was lower than that without pretreatment, while the viability of the buthionine sulfoximine (BSO) pretreated cells was higher than that without pretreatment. The poly(VBPT-co-PEGMA)-S-S-MP micelles could induce the apoptosis of Raji cells, and the apoptosis behavior was dose-dependent. This redox-responsive polymer-drug conjugate provides a promising platform for the delivery of thiol-containing biological molecules. PMID:24598057

Zhuang, Yuanyuan; Su, Yue; Peng, Yu; Wang, Dali; Deng, Hongping; Xi, Xiaodong; Zhu, Xinyuan; Lu, Yunfeng

2014-04-14

347

Reduced nonprotein thiols inhibit activation and function of MMP-9: Implications for chemoprevention  

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Clinical studies demonstrate a positive correlation between the extent of matrix metalloproteinase (MMP) activation and malignant progression of precancerous lesions. Therefore, identification of effective, well-tolerated MMP inhibitors represents a rational chemopreventive strategy. A variety of agents, including proteinases and thiol-oxidizing compounds, activate MMPs by initiating release of the propeptide's cysteine sulfur “blockage” of the MMP active site. Despite the importance of t...

Pei, Ping; Horan, Michael P.; Hille, Russ; Hemann, Craig F.; Schwendeman, Steven P.; Mallery, Susan R.

2006-01-01

348

A Model of Redox Kinetics Implicates the Thiol Proteome in Cellular Hydrogen Peroxide Responses  

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Hydrogen peroxide is appreciated as a cellular signaling molecule with second-messenger properties, yet the mechanisms by which the cell protects against intracellular H2O2 accumulation are not fully understood. We introduce a network model of H2O2 clearance that includes the pseudo-enzymatic oxidative turnover of protein thiols, the enzymatic actions of catalase, glutathione peroxidase, peroxiredoxin, and glutaredoxin, and the redox reactions of thioredoxin and glutathione. Simulations repro...

2010-01-01

349

Inelastic Tunneling Spectroscopy of Gold-Thiol and Gold-Thiolate Interfaces in Molecular Junctions: The Role of Hydrogen  

CERN Multimedia

It is widely believed that when a molecule with thiol (S-H) end groups bridges a pair of gold electrodes, the S atoms bond to the gold and the thiol H atoms detach from the molecule. However, little is known regarding the details of this process, its time scale, and whether molecules with and without thiol hydrogen atoms can coexist in molecular junctions. Here we explore theoretically how inelastic tunneling spectroscopy (IETS) can shed light on these issues. We present calculations of the geometries, low bias conductances and IETS of propanedithiol and propanedithiolate molecular junctions with gold electrodes. We show that IETS can distinguish between junctions with molecules having no, one or two thiol hydrogen atoms. We find that in most cases the single-molecule junctions in the IETS experiment of Hihath et al. [Nano Lett. 8, 1673 (2008)] had no thiol H atoms, but that a molecule with a single thiol H atom may have bridged their junction occasionally. We also consider the evolution of the IETS spectrum ...

Demir, Firuz

2012-01-01

350

Gold Nanoparticles Protected with Thiol-Derivatized Amphiphilic Poly(epsilon-caprolactone)-b-poly(acrylic acid)  

DEFF Research Database (Denmark)

Amphiphilic poly(epsilon-caprolactone)-b-poly(acrylic acid) (HS-PCL-b-PAA) with a thiol functionality in the PCL terminal has been prepared in a novel synthetic cascade. Initially, living anionic ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) employing the difunctional initiator, 2-hydroxyethyl 2-bromoisobutyrate, followed by esterification with 2,4-dinitrophenyl- or 4-monomethoxytrityl-protected mercaptoacetic acids (Prot-), provided well-defined PCL macroinitiators capped with protected thiols. The macroinitiators allowed atom transfer radical polymerization (ATRP) of tent-butyl acrylate (tBA) in a controlled fashion by use of NiBr2(PPh3)(2) catalyst to produce Prot-PCL-b-PtBA with narrow polydispersities (1.17-1.39). Subsequent mild deprotection protocols provided HS-PCL-b-PAA. Reduction of a gold salt in the presence of this macroligand under thiol-deficient conditions afforded stable, aggregation-free nanoparticles, as evidenced from UV-vis spectroscopy and transmission electron microscopy (TEM), the latter revealed nanoparticles with a mean diameter of 9.0 +/- 3.1 nm.

Javakhishvili, Irakli; Hvilsted, Søren

2009-01-01

351

The critical role of the cellular thiol homeostasis in cadmium perturbation of the lung extracellular matrix  

International Nuclear Information System (INIS)

Cadmium (Cd) inhalation can result in emphysema. Cd exposure of rat lung fibroblasts (RFL6) enhanced levels of metal scavenging thiols, e.g., metallothionein (MT) and glutathione (GSH), and the heavy chain of ?-glutamylcysteine synthetase (?-GCS), a key enzyme for GSH biosynthesis, concomitant with downregulation of lysyl oxidase (LO), a copper-dependent enzyme for crosslinking collagen and elastin in the extracellular matrix (ECM). Cd downregulation of LO in treated cells was closely accompanied by suppression of synthesis of collagen, a major structure component of the lung ECM. Using rats intratracheally instilled with cadmium chloride (30 ?g, once a week) as an animal model, we further demonstrated that although 2-week Cd instillation induced a non-significant change in the lung LO activity and collagen synthesis, 4- and 6-week Cd instillation resulted in a steady decrease in the lung LO and collagen expression. The lung MT and total GSH levels were both upregulated upon the long-term Cd exposure. Emphysematous lesions were generated in lungs of 6-week Cd-dosed rats. Increases of cellular thiols by transfection of cells with MT-II expression vectors or treatment of cells with GSH monoethyl ester, a GSH delivery system, markedly inhibited LO mRNA levels and catalytic activities in the cell model. Thus, Cd upregulation of cellular thiols may be a critical cellular event facilitating downregulation of LO, a potential mechanism for Cd-induced emphysema.

2010-01-12

352

Immunoprotection in sheep against Haemonchus contortus using its thiol-purified excretory/secretory proteins  

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Full Text Available Excretory/Secretory antigen was prepared by culturing live adult worms of Haemonchus contortus in RPMI 1640 medium at a concentration of 50 worms per mL in a culture-flask at 37 ?C for 24 hr and the culture supernatant was used as antigen. The E/S antigen was purified by thiol-sepharose affinity chromatography. On western blot analysis, it was demonstrated that thiol-purified antigen showed a single reactive band at 66 kDa. In immunization trial, sheep were administered intramuscularly with 500 ?g of thiol-purified excretory/secretory antigen along with montanide as adjuvant on day 0, 30 and 60. On ELISA, it was observed that the mean absorbance values were significantly (p ? 0.01 higher up to 20 weeks post immunization in Group-I (purified antigen compared to Group- II (unimmunized control. Further, the mean EPG values was lower in Group I (200.00 ± 40.82 to 400.00 ± 91.29 than Group II (2200.00 ± 108.01 to 5100.00 ± 169.56 and the percentage reduction in mean fecal egg counts was 88.50%. Similarly, the mean abomasal worm counts was lower in Group I (808.33 ± 78.29 than Group II (3280.00 ± 147.19 and the percentage reduction in mean abomasal worm count was 75.40%.

Selvarayar Arunkumar

2012-12-01

353

Kandelia obovata (S., L.) Yong tolerance mechanisms to Cadmium: Subcellular distribution, chemical forms and thiol pools  

International Nuclear Information System (INIS)

Highlights: ? Cadmium tolerance mechanisms of Kandelia obovata was investigated systematacially. ? Thiol pool can play roles in cadmium detoxification mechanisms. ? Increasing cadmium treatment strength caused proportional increase of cadmium uptake. ? More than half of cadmium was localized in cell walls, and lowest in membranes. ? Sodium chloride and acetic acid extractable fractions were dominant. - Abstract: In order to explore the detoxification mechanisms adopted by mangrove under cadmium (Cd) stress, we investigated the subcellular distribution and chemical forms of Cd, in addition to the change of the thiol pools in Kandelia obovata (S., L.) Yong, which were cultivated in sandy culture medium treated with sequential Cd solution. We found that Cd addition caused a proportional increase of Cd in the organs of K. obovata. The investigation of subcellular distribution verified that most of the Cd was localized in the cell wall, and the lowest was in the membrane. Results showed sodium chloride and acetic acid extractable Cd fractions were dominant. The contents of non-protein thiol compounds, Glutathione and phytochelatins in K. obovata were enhanced by the increasing strength of Cd treatment. Therefore, K. obovata can be defined as Cd tolerant plant, which base on cell wall compartmentalization, as well as protein and organic acids combination.

2012-11-01

354

Ethyl propiolate derivatisation for the analysis of varietal thiols in wine.  

Science.gov (United States)

Varietal thiols [3-mercaptohexan-1-ol (3MH), 3-mercaptohexyl acetate (3MHA) and 4-mercapto-4-methylpentan-2-one (4MMP)] have been extensively studied in the recent literature. Nonetheless the hardest obstacle for research focussing on this class of compounds is the lack of quick, user-friendly and sensitive analytical methods. The current paper presents the use of ethyl propriolate (ETP) as a novel derivatising agent to quantify varietal thiols and the first time quantification of the thiol-ETP adducts via gas chromatography-mass spectrometry. Method optimisation including choice of the best SPE cartridge, derivatisation pH and adducts stability is presented. Validation of the method via stable isotope dilution was carried out. Detection limits in both model wine (4MMP 7.2ng/L, 3MHA 40.0ng/L and 3MH 91.2ng/L) and white wine (4MMP 24.5ng/L, 3MHA 120.9ng/L and 3MH 194.6ng/L) for the novel ETP-based method were lower than those obtained with the p-HMB method. Finally, 14 New Zealand Sauvignon blanc were analysed with both the new method and the organo-mercury based procure: good correlations were obtained for 3MH and 3MHA. Detection limits obtained with the new methods, its rapidity and reproducibility make this protocol perfectly suitable for oenological purposes. PMID:24034138

Herbst-Johnstone, Mandy; Piano, Federico; Duhamel, Nina; Barker, David; Fedrizzi, Bruno

2013-10-18

355

Location of N-methyl-N'-nitro-N-nitrosoguanidine-induced gastrointestinal tumors correlates with thiol distribution  

International Nuclear Information System (INIS)

Chronic administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water causes a high incidence of carcinomas of the glandular stomach in rats. Following a single oral dose of [14C-methyl]MNNG (80 p.p.m.; 2.5 mg/kg), the extent of DNA methylation in the glandular stomach was 9 and 20 times higher than that in the forestomach and oesophagus, respectively. The autoradiographic distribution of tissue-bound radioactivity within the glandular stomach of BONN/WIST rats coincides with strain-specific tumor location at the small curvature. Following intragastric administration of [14C-methyl]MNNG, alkylation levels in forestomach and glandular stomach were twice as high as those observed after oral exposure via the drinking water, whereas duodenal DNA showed a much lower extent of methylation. The regional differences in DNA alkylation correlated with tissue-specific variations in the concentration of cellular thiols which are known to accelerate the heterolytic decomposition of MNNG. When [14C-methyl]MNNG was given intragastrically together with the thiol-blocking agent, N-ethylmaleimide, covalent binding of the 14C-radioactivity to forestomach, glandular stomach and duodenum was almost completely abolished. This indicates that the preferential induction of glandular stomach tumors by MNNG relies on high concentrations of cellular thiols in the target tissue

1983-01-01

356

Purification and characterization of thiols in an arsenic hyperaccumulator under arsenic exposure.  

Science.gov (United States)

Pteris vittata (Chinese brake fern) is the first reported arsenic hyperaccumulator. To investigate the arsenic tolerance mechanism in this plant, reversed-phase HPLC with postcolumn derivatization was used to analyze the thiols induced under arsenic exposure. A major thiol in the plant leaflets was found to be responsive to arsenic exposure. The arsenic-induced compound was purified on a large scale by combining covalent chromatography and preparative reversed-phase HPLC. About 2 mg of this compound was isolated from 1 kg of fresh leaflets. The purified arsenic-induced compound was characterized using electrospray ionization mass spectrometry. A molecular ion (M + 1) of 540 and fragments were obtained, which indicated that the arsenic-induced thiol was a phytochelatin with two subunits (PC(2)). Compared to the classical methods for purification of phytochelatins, this new method is more specific, simple, and rapid and is suitable for purification of PCs in a large scale as well as sample preparation for mass spectrometry analysis. PMID:14670068

Zhang, Weihua; Cai, Yong

2003-12-15

357

Chemical synthesis and structural studies of thiol-capped gold nanoparticles  

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We report the chemical synthesis and structural studies of thiol-capped Au nanoparticles (NPs) using extended X-ray absorption fine structures (EXAFS) and high-resolution transmission electron microscopy (HRTEM). Synthesis of Au NPs was conducted in one case in a toluene/water two-phase system using alkanethiols with varied hydrocarbon chain length (C6, C12, and C18), resulting in NPs of sizes ranging from 1.6 nm to 5.4 nm. Au L{sub 3}-edge EXAFS reveals a systematical trend of the local structure of Au in the NPs when the Au/S ratio and chain-length of thiols are varied. In another synthesis, thiol-capped Au NPs were prepared on the surface of silicon nanowires, which act as both substrates and reducing agents. HRTEM reveals that not only spherical particles but also very small quasi-1D nanostructures of Au were formed. The formation and structure of these Au NPs was discussed in terms of ligand and template effect associated with the silicon nanowire substrates.

Zhang, P.; Chu, A.Y.-C.; Sham, T.K.; Yao, Y.; Lee, S.-T.; (Dalhousie U.); (City U/Hong Kong); (UWO)

2008-12-16

358

Investigation into the Effect of Molds in Grasses on Their Content of Low Molecular Mass Thiols  

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Full Text Available The aim of this study was to investigate the effect of molds on levels of low molecular mass thiols in grasses. For this purpose, the three grass species Lolium perenne, Festulolium pabulare and Festulolium braunii were cultivated and sampled during four months, from June to September. The same species were also grown under controlled conditions. High-performance liquid chromatography with electrochemical detection was used for quantification of cysteine, reduced (GSH and oxidized (GSSG glutathione, and phytochelatins (PC2, PC3, PC4 and PC5. Data were statistically processed and analyzed. Thiols were present in all examined grass species. The effect of fungicide treatments applied under field conditions on the content of the evaluated thiols was shown to be insignificant. Species influenced (p < 0.05 PC3 and GSSG content. F. pabulare, an intergeneric hybrid of drought- and fungi-resistant Festuca arundinacea, was comparable in PC3 content with L. perenne and F. braunii under field conditions. Under controlled conditions, however, F. pabulare had higher (p < 0.05 PC3 content than did L. perenne and F. braunii. Under field conditions, differences between the evaluated species were recorded only in GSSG content, but only sampling in June was significant. F. pabulare had higher (p < 0.05 GSSG content in June than did L. perenne and F. braunii.

Adam Nawrath

2012-10-01

359

Electronic and structural studies of immobilized thiol-derivatized cobalt porphyrins on gold surfaces  

International Nuclear Information System (INIS)

The immobilisation of thiol-derivatized cobalt porphyrins on gold surfaces has been studied in detail by means of combined scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). S-thioacetyl has been used as a protective group for the thiol. Different routes for deprotection of the acetyl groups were performed in acidic and in basic conditions. The results show the formation of monolayer films for the different preparation schemes. The immobilisation of the molecules on the gold surface takes place through the thiol-linkers by the formation of multiple thiolate bonds. In the case of layers formed with protected porphyrins approximately 60% of the linkers are bonded to the gold surface whereas for deprotected layers the amount of bonded linkers is increased up to about 80%. STM measurements revealed that the molecules arrange in a disordered overlayer and do not exhibit mobility on the gold surface. Annealing experiments have been performed in order to test the stability of the porphyrin layers. Disordered patterns have been observed in the STM images after annealing at T = 400 oC. XPS revealed that the sulphur content disappeared completely after annealing at T = 180 oC and that the molecules did undergo significant modifications

2007-07-15

360

Thiol group modulation of sodium-lithium countertransport kinetics in diabetic nephropathy.  

Science.gov (United States)

Abnormal erythrocyte sodium-lithium countertransport (Na-Li CT) activity, traditionally measured at a single sodium concentration of 140 mmol.l-1 (V140), may represent an inherited risk marker for diabetic nephropathy. The membrane defect underlying this association is poorly understood, though modulation by key protein thiol groups appears to be important in essential hypertension. To improve understanding of this abnormality, Na-Li CT kinetics in untreated erythrocytes and after thiol group alkylation with N-ethylmaleimide were investigated in 18 subjects with diabetic nephropathy, 20 normoalbuminuric insulin-dependent diabetic (IDDM) subjects and 18 non-diabetic individuals. Using the traditional assay, V140 was similar in subjects with diabetic nephropathy compared to IDDM control subjects vs 0.311 (0.152-0.475) (0.247 (0.111-0.498) mmol Li.h-1.l erythrocytes-1). Kinetic parameters were abnormal in subjects with diabetic nephropathy compared with diabetic and non-diabetic control subjects with both Vmax (maximal Na-Li CT activity) (0.454 (0.257-0.963) vs 0.338 (0.183-0.972) vs 0.332 (0.213-0.603) mmol Li.h-1.l erythrocytes-1, p V140, is poor at detecting individuals with diabetic nephropathy. Study of the kinetic parameters of the transporter, including thiol group modulation, suggests that increased ion association, Vmax/Km(So) ratio may represent the inherited defect and improves identification of subjects with diabetic nephropathy. PMID:9300245

Jones, S C; Thomas, T H; Marshall, S M

1997-09-01

 
 
 
 
361

Electronic and structural studies of immobilized thiol-derivatized cobalt porphyrins on gold surfaces  

Energy Technology Data Exchange (ETDEWEB)

The immobilisation of thiol-derivatized cobalt porphyrins on gold surfaces has been studied in detail by means of combined scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). S-thioacetyl has been used as a protective group for the thiol. Different routes for deprotection of the acetyl groups were performed in acidic and in basic conditions. The results show the formation of monolayer films for the different preparation schemes. The immobilisation of the molecules on the gold surface takes place through the thiol-linkers by the formation of multiple thiolate bonds. In the case of layers formed with protected porphyrins approximately 60% of the linkers are bonded to the gold surface whereas for deprotected layers the amount of bonded linkers is increased up to about 80%. STM measurements revealed that the molecules arrange in a disordered overlayer and do not exhibit mobility on the gold surface. Annealing experiments have been performed in order to test the stability of the porphyrin layers. Disordered patterns have been observed in the STM images after annealing at T = 400 {sup o}C. XPS revealed that the sulphur content disappeared completely after annealing at T = 180 {sup o}C and that the molecules did undergo significant modifications.

Berner, Simon [Department of Physics, Uppsala University, Box 530, 75121 Uppsala (Sweden)]. E-mail: berner@physik.unizh.ch; Lidbaum, Hans [Department of Physics, Uppsala University, Box 530, 75121 Uppsala (Sweden); Ledung, Greger [Department of Biology and Chemical Engineering, Maelardalen University, Box 325, 63105 Eskilstuna (Sweden); Ahlund, John [Department of Physics, Uppsala University, Box 530, 75121 Uppsala (Sweden); Nilson, Katharina [Department of Physics, Uppsala University, Box 530, 75121 Uppsala (Sweden); Schiessling, Joachim [Department of Physics, Uppsala University, Box 530, 75121 Uppsala (Sweden); Gelius, Ulrik [Department of Physics, Uppsala University, Box 530, 75121 Uppsala (Sweden); Baeckvall, Jan-E. [Department of Organic Chemistry, Stockholm University, Arrhenius Laboratory, 10691 Stockholm (Sweden); Puglia, Carla [Department of Physics, Uppsala University, Box 530, 75121 Uppsala (Sweden); Oscarsson, Sven [Department of Biology and Chemical Engineering, Maelardalen University, Box 325, 63105 Eskilstuna (Sweden)

2007-07-15

362

On the inactivity of thiol-subtilisin. The role of the intramolecular electric field.  

Science.gov (United States)

Based on computed proton affinities for several model systems, the energetics of proton transfer and the acidity of the catalytic triads Cys-His-Asn (papain). Cys-His-Asp (thiol-subtilisin) and Ser-His-Asp (subtilisin) are discussed. It is shown that in papain the ion-pair Cys--HisH+ exists owing to the intramolecular electric field, and that a similar situation is found in thiol-subtilisin. but not in subtilisin. Assuming similar reaction mechanisms for papain and thiol-subtilisin - i.e. proton transfer from HisH+ to the NH group of the scissile peptide bond - the inactivity of thil-subtilisin towards proteins is explained by the much greater basicity of His in the complex His-Asp- than in His-Asn. In order for this explanation to be consistent, it is tentatively concluded that the catalytic mechanism of the serine proteases is different from that of the cystein proteases, and involves direct transfer of the serine proton to the leaving group in the acylation step. PMID:17000163

Van Duijnen, P T

1981-04-01

363

Thiol-reactive compounds from garlic inhibit the epithelial sodium channel (ENaC).  

Science.gov (United States)

The epithelial sodium channel (ENaC) is a key factor in the transepithelial movement of sodium, and consequently salt and water homeostasis in various organs. Dysregulated activity of ENaC is associated with human diseases such as hypertension, the salt-wasting syndrome pseudohypoaldosteronism type 1, cystic fibrosis, pulmonary oedema or intestinal disorders. Therefore it is important to identify novel compounds that affect ENaC activity. This study investigated if garlic (Allium sativum) and its characteristic organosulfur compounds have impact on ENaCs. Human ENaCs were heterologously expressed in Xenopus oocytes and their activity was measured as transmembrane currents by the two-electrode voltage-clamp technique. The application of freshly prepared extract from 5g of fresh garlic (1% final concentration) decreased transmembrane currents of ENaC-expressing oocytes within 10 min. This effect was dose-dependent and irreversible. It was fully sensitive to the ENaC-inhibitor amiloride and was not apparent on native control oocytes. The effect of garlic was blocked by dithiothreitol and l-cysteine indicating involvement of thiol-reactive compounds. The garlic organosulsur compounds S-allylcysteine, alliin and diallyl sulfides had no effect on ENaC. By contrast, the thiol-reactive garlic compound allicin significantly inhibited ENaC to a similar extent as garlic extract. These data indicate that thiol-reactive compounds which are present in garlic inhibit ENaC. PMID:22668601

Krumm, Patrick; Giraldez, Teresa; Alvarez de la Rosa, Diego; Clauss, Wolfgang G; Fronius, Martin; Althaus, Mike

2012-07-01

364

The mode of action of allicin: trapping of radicals and interaction with thiol containing proteins.  

Science.gov (United States)

Allicin (thio-2-propene-1-sulfinic acid S-allyl ester) is the main biologically active component of garlic clove extracts. Its biological activity was attributed to either antioxidant activity or thiol disulfide exchange. Antioxidant properties of both allicin and its precursor, alliin (+S-allyl-L-cysteine sulfoxide), were investigated in the Fenton oxygen-radical generating system [H2O2-Fe(II)]. Using the spin trapping technique and ESR, it was found that both compounds possessed significant antioxidant activity. The reaction between allicin and L-cysteine was studied by 1H and 13C-NMR, and a S-thiolation product, S-allylmercaptocysteine, was identified. Allicin irreversibly inhibited SH-protease papain, NADP(+)-dependent alcohol dehydrogenase from Thermoanaerobium brockii (TBAD), and the NAD(+)-dependent alcohol dehydrogenase from horse liver (HLAD). All the three enzymes could be reactivated with thiol containing compounds. Papain could be reactivated with glutathione, TBAD with dithiothreitol or 2-mercaptoethanol (2-ME) but not by glutathione, while HLAD could be reactivated only with 2-ME. This study demonstrates that in addition to its antioxidant activity, the major biological effect of allicin should be attributed to its rapid reaction with thiol containing proteins. PMID:9528659

Rabinkov, A; Miron, T; Konstantinovski, L; Wilchek, M; Mirelman, D; Weiner, L

1998-02-01

365

Transport through thiol SAMs: Effect of monolayer order, dynamics and temperature  

Science.gov (United States)

We discuss the self assembly and charge transport of organic thiol molecules and discuss the influence of structure, order and dynamics in the monolayer [1] on the transport and also the effect of temperature by scanning tunneling microscopy/spectroscopy (STM/S). Conjugated thiol molecular wires and organometals such as terpyridine metal complexes provide a new platform for molecular electronic devices. Molecular resolution STM imaging in vacuum reveals that the molecular wires adopt an incommensurate, almost vertical SAM structure with a rectangular unit cell, while terpyridine metal thiol complexes tend to lie flat on the Au(111) substrate. STS of the molecular wires show that inherent asymmetry in the molecular structure and asymmetric coupling to contacts results in asymmetric, weakly rectifying I-Vs. STS on alkanethiols do not show a marked temperature dependence down to 150K. We also show that packing and order greatly influence the transport measurements and that the presence of molecular order in the monolayer is very important for reproducible I-Vs. Thus a good control of the molecule-substrate interface needs to be ensured for device reliability. We also point out that molecular electronic devices need to be made tolerant to fluctuations as these cannot be totally eliminated in low dimensional soft systems. [1] Geetha R. Dholakia et. al, PHYSICAL REVIEW B 69, 153402 (2004).

Dholakia, Geetha

2005-03-01

366

The assessment of thiol status in children with neurogenic bladder caused by meningomyelocele.  

Science.gov (United States)

Purpose: Oxidative stress can cause tissue damage in many diseases. Oxidative status depends on the balance between total oxygen radical absorbance capacity and antioxidants. Neurogenic bladder (NB) is a special state where oxidative status can influence urinary tract function. We decided to measure antioxidant (thiol) status in patients with NB and assess the effect of NB on the urinary antioxidant status and to correlate it with urodynamic findings. Materials and Methods: The investigation was conducted on two groups. The first group, constituted of 41 children with NB. The second group, consisted of 20 healthy children with no abnormality in urinary and nervous systems. The antioxidant status was assessed based on the enzyme-linked immunosorbent assay of thiols. Results: The median value of urinary protein thiol level was significantly lower in NB patients than in reference group [median 48 (0.0-633.33) and 221.55 (0.17-1293] ?moL/g protein, respectively (P bladder overactivity. Oxidative stress may be involved in the pathophysiology of bladder dysfunction related to neurogenic damage. PMID:24807750

Korzeniecka-Kozerska, Agata; Zawada, Bozena Okurowska; Zawada, Bozena Okurowska; Skutnik, Joanna Michaluk; Skutnik, Joanna Michaluk; Wasilewska, Anna; Wasilewska, Anna

2014-01-01

367

Metabolism of the Synthetic Progestogen Norethynodrel by Human Ketosteroid Reductases of the Aldo-Keto Reductase Superfamily  

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Human ketosteroid reductases of the aldo-keto reductase (AKR) superfamily, i.e. AKR1C1-4, are implicated in the biotransformation of synthetic steroid hormones. Norethynodrel (NOR, 17?-ethynyl-17?-hydroxy-estra-5(10)-en-3-one), the progestin component of the first marketed oral contraceptive, is known to undergo rapid and extensive metabolism to 3?- and 3?-hydroxy metabolites. The ability of the four human AKR1C enzymes to catalyze the metabolism of NOR has now been characterized. AKR1C1 ...

Jin, Yi; Duan, Ling; Chen, Mo; Penning, Trevor M.; Kloosterboer, Helenius J.

2012-01-01

368

Malonic Semialdehyde Reductase, Succinic Semialdehyde Reductase, and Succinyl-Coenzyme A Reductase from Metallosphaera sedula: Enzymes of the Autotrophic 3-Hydroxypropionate/4-Hydroxybutyrate Cycle in Sulfolobales?  

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A 3-hydroxypropionate/4-hydroxybutyrate cycle operates during autotrophic CO2 fixation in various members of the Crenarchaea. In this cycle, as determined using Metallosphaera sedula, malonyl-coenzyme A (malonyl-CoA) and succinyl-CoA are reductively converted via their semialdehydes to the corresponding alcohols 3-hydroxypropionate and 4-hydroxybutyrate. Here three missing oxidoreductases of this cycle were purified from M. sedula and studied. Malonic semialdehyde reductase, a member of the 3...

Kockelkorn, Daniel; Fuchs, Georg

2009-01-01

369

Chimeric 3-hydroxy-3-methylglutaryl coenzyme A reductase-dihydrofolate reductase genes display bidirectional expression and unidirectional regulation in stably transfected cells.  

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We have constructed hybrid dihydrofolate reductase (DHFR) genes which are controlled by the sterol-responsive hamster 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase promoter. Stable transfection frequencies of these chimeric templates into a DHFR-deficient Chinese hamster cell line indicate that the HMG CoA reductase promoter fragment confers DHFR transformation irrespective of its orientation relative to a downstream murine DHFR cDNA. Sterol-regulated levels of DHFR RNA and protei...

Abrams, J. M.; Schimke, R. T.

1989-01-01

370

Domain Evolution and Functional Diversification of Sulfite Reductases  

Science.gov (United States)

Sulfite reductases are key enzymes of assimilatory and dissimilatory sulfur metabolism, which occur in diverse bacterial and archaeal lineages. They share a highly conserved domain "C-X5-C-n-C-X3-C" for binding siroheme and iron-sulfur clusters that facilitate electron transfer to the substrate. For each sulfite reductase cluster, the siroheme-binding domain is positioned slightly differently at the N-terminus of dsrA and dsrB, while in the assimilatory proteins the siroheme domain is located at the C-terminus. Our sequence and phylogenetic analysis of the siroheme-binding domain shows that sulfite reductase sequences diverged from a common ancestor into four separate clusters (aSir, alSir, dsr, and asrC) that are biochemically distinct; each serves a different assimilatory or dissimilatory role in sulfur metabolism. The phylogenetic distribution and functional grouping in sulfite reductase clusters (dsrA and dsrB vs. aSiR, asrC, and alSir) suggest that their functional diversification during evolution may have preceded the bacterial/archaeal divergence.

Dhillon, Ashita; Goswami, Sulip; Riley, Monica; Teske, Andreas; Sogin, Mitchell

2005-02-01

371

Stereospecific electrophoretically mediated microanalysis assay for methionine sulfoxide reductase enzymes.  

Science.gov (United States)

An electrophoretically mediated microanalysis assay (EMMA) for the determination of the stereoselective reduction of L-methionine sulfoxide diastereomers by methionine sulfoxide reductase enzymes was developed using fluorenylmethyloxycarbonyl (Fmoc)-L-methionine sulfoxide as substrate. The separation of the diastereomers of Fmoc-L-methionine sulfoxide and the product Fmoc-L-methionine was achieved in a successive multiple ionic-polymer layer-coated capillary using a 50 mM Tris buffer, pH 8.0, containing 30 mM sodium dodecyl sulfate as background electrolyte and an applied voltage of 25 kV. 4-Aminobenzoic acid was employed as internal standard. An injection sequence of incubation buffer, enzyme, substrate, enzyme, and incubation buffer was selected. The assay was optimized with regard to mixing time and mixing voltage and subsequently applied for the analysis of stereoselective reduction of Fmoc-L-methionine-(S)-sulfoxide by human methionine sulfoxide reductase A and of the Fmoc-L-methionine-(R)-sulfoxide by human methionine sulfoxide reductase B. The Michaelis-Menten constant, K m, and the maximum velocity, v max, were determined. Essentially identical data were determined by the electrophoretically mediated microanalysis assay and the analysis of the samples by CE upon offline incubation. Furthermore, it was shown for the first time that Fmoc-methionine-(R)-sulfoxide is a substrate of human methionine sulfoxide reductase B. PMID:24424966

Zhu, Qingfu; El-Mergawy, Rabab G; Heinemann, Stefan H; Schönherr, Roland; Já?, Pavel; Scriba, Gerhard K E

2014-02-01

372

Herpes simplex type 1 ribonucleotide reductase. Mechanism studies with inhibitors.  

Science.gov (United States)

Several known inhibitors of mammalian ribonucleotide reductase were studied for their interactions with herpes simplex virus type 1 (HSV-1) ribonucleotide reductase. MAIQ (4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone) produced apparent inactivation of HSV-1 ribonucleotide reductase. Only catalytically cycling, not resting, enzyme could be inactivated. Double reciprocal replots of the rates of inactivation versus the concentration of MAIQ indicated that a reversible complex with the enzyme was formed prior to inactivation. In the presence of 10 microM CDP, the maximum rate of inactivation was 20 per h (t1/2 = 3 min). The half-maximum rate was achieved at about 15 microM MAIQ. INOX (periodate-oxidized inosine) also appeared to inactivate HSV-1 ribonucleotide reductase. In contrast to MAIQ, it readily inactivated resting as well as cycling enzyme. CDP retarded the rates of inactivation by INOX. An initial reversible complex between INOX and enzyme was not detectable under the conditions used. IMPY (2,3-dihydro-1H-pyrazolo(2,3-a)imidazole) and guanazole (3,5-diamino-1,2,4-triazole) produced reversible inhibition. Although the data with both inhibitors were most consistent with the noncompetitive inhibition model (versus CDP), the data with guanazole were also marginally consistent with the uncompetitive model. PMID:2991215

Spector, T; Jones, T E

1985-07-25

373

Stereospecific oxidation of calmodulin by methionine sulfoxide reductase A.  

Science.gov (United States)

Methionine sulfoxide reductase A has long been known to reduce S-methionine sulfoxide, both as a free amino acid and within proteins. Recently the enzyme was shown to be bidirectional, capable of oxidizing free methionine and methionine in proteins to S-methionine sulfoxide. A feasible mechanism for controlling the directionality has been proposed, raising the possibility that reversible oxidation and reduction of methionine residues within proteins is a redox-based mechanism for cellular regulation. We undertook studies aimed at identifying proteins that are subject to site-specific, stereospecific oxidation and reduction of methionine residues. We found that calmodulin, which has nine methionine residues, is such a substrate for methionine sulfoxide reductase A. When calmodulin is in its calcium-bound form, Met77 is oxidized to S-methionine sulfoxide by methionine sulfoxide reductase A. When methionine sulfoxide reductase A operates in the reducing direction, the oxidized calmodulin is fully reduced back to its native form. We conclude that reversible covalent modification of Met77 may regulate the interaction of calmodulin with one or more of its many targets. PMID:23583331

Lim, Jung Chae; Kim, Geumsoo; Levine, Rodney L

2013-04-11

374

5. cap alpha. -reductase activity in rat adipose tissue  

Energy Technology Data Exchange (ETDEWEB)

We measured the 5 ..cap alpha..-reductase activity in isolated cell preparations of rat adipose tissue using the formation of (/sup 3/H) dihydrotestosterone from (/sup 3/H) testosterone as an endpoint. Stromal cells were prepared from the epididymal fat pad, perinephric fat, and subcutaneous fat of male rats and from perinephric fat of female rats. Adipocytes were prepared from the epididymal fat pad and perinephric fat of male rats. Stromal cells from the epididymal fat pad and perinephric fat contained greater 5..cap alpha..-reductase activity than did the adipocytes from these depots. Stromal cells from the epididymal fat pad contained greater activity than those from perinephric and subcutaneous depots. Perinephric stromal cells from female rats were slightly more active than those from male rats. Estradiol (10/sup -8/ M), when added to the medium, caused a 90% decrease in 5..cap alpha..-reductase activity. Aromatase activity was minimal, several orders of magnitude less than 5..cap alpha..-reductase activity in each tissue studied.

Zyirek, M.; Flood, C.; Longcope, C.

1987-11-01

375

Gold Nanoparticles Protected with Thiol-Derivatized Amphiphilic Poly( -caprolactone)-b-poly(acrylic acid)  

DEFF Research Database (Denmark)

Amphiphilic poly(c-caprolactone)-b-poly(acrylic acid) (HS-PCL-b-PAA) bearing thiol functionality at the PCL terminal has been synthesized by a combination of ring-opening polymerization (ROP) of c-caprolactone (c-CL), esterification of hydroxy chain end with protected mercaptoacetic acid, subsequent chain-extension by atom transfer radical polymerization (ATRP) of tert-butyl acrylate (tBA), and final deprotection steps. ROP of c-CL initiated by 2-hydroxyethyl 2-bromoisobutyrate, and catalysed by tin octoate afforded Br-PCL-OH with the degree of polymerization of 30 and narrow molecular weight distribution (1.09). The hydroxy chain end of Br-PCL-OR was modified by reacting with a-(2,4-dinitrophenylthio)acetic acid or a-(4methoxytritylthio) acetic acid resulting in heterotelechelic PCL incorporating protected thiol and bromoester functionalities. It was then employed as macroinitiator in NiBr2(PPh3)2 catalysed ATRP of tBA. ATRP of tBA provided diblock copolymers with low polydispersity index (1.17-1.39) while preserving the protected thiol function. Sequential or simultaneous removal of 2,4-dinitrophenyl or 4-methoxytrityl and tert-butyl ester groups resulted in HS-PCL-b-PAA. The PCL backbone remained intact after mild deprotection protocols. Thus, reversible masking of thiol functionality allows facile fusion of the controlled polymerization techniques employing dual initiator strategy, and furnishes RS-PCL-bPAA with well-defined chain architecture which has been assessed by size exclusion chromatography (SEC), nuclear magnetic resonance eR NMR) and infrared (FT IR) spectroscopy. The capacity of the resulting block copolymer in preparation of monolayer-protected gold nanoparticles has been examined by reduction of a gold salt in the presence of this macroligand under thiol-deficient conditions. As a result stable, aggregation-free nanopaticles with moderate dispersity as estimated from UV-visible spectroscopy and transmission electron microscopy (TEM) data were obtained.

Javakhishvili, Irakli; Hvilsted, Søren

2008-01-01

376

POTENTIOMETRIC RESPONSE OF A GRAPHITE ELECTRODE MODIFIED WITH COBALT PHTHALOCYANINE FOR THIOLS AND DISULFIDES  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in spanish Se ha investigado la respuesta potenciométrica the electrodos de grafito pirolítico ordinario (OPG) modificados con ftalocianina de cobalto (Co-Pc) frente a los tioles (R-SH) 2-mecaptoetanol y L-cisteína y los correspondientes disulfuros (R-SS-R). Al agregar pequeñas cantidades de estos tioles a sol [...] uciones acuosas con pH en el rango 11-4, se obtienen respuestas en potencial estables dentro de unos pocos segundos despues de las adiciones. Gráficas de potencial vs. log [R-SH] dan rectas para todos los casos, con pendientes cercanas a -0,060 V para concentraciones del tiol en el rango de 10-5 a 10-2 M. Estas medidas se efectuaron en presencia de aire u oxígeno. En atmósfera de nitrógeno, las pendientes de las gráficas suben a -0,14 V. El potencial de circuito abierto de los electrodos OPG/Co-Pc resultó ser independiente de la concentración de los disulfuros lo que indica que el potencial del electrodo modificado es sólo sensible al tiol. Los electrodos de grafito sin modificar frente a los tioles dan respuestas en potencial irreproducibles, lo que muestra la importancia de la presencia Co-Pc para obtener respuestas potenciométricas estables Abstract in english We have investigated the potentiometric response of ordinary pyrolytic graphite electrodes (OPG) modified with cobalt phthalocyanine (Co-Pc) for thiols (R-SH) 2-mercaptoethanol, L-cysteine and their corresponding disulfides (R-SS-R). Stable potentials are achieved after a few seconds of additions of [...] different amounts of thiols to aqueous solutions of pH values between 11 and 4. Plots of potential vs. log [R-SH] give straight lines for all cases with slopes ca. -0.060 V with concentrations of the thiol varying from 10-5 up to 10-2 M. These measurements were conducted in the presence of air or oxygen. Under nitrogen, the slopes increase to -0.14 V. The potential response of OPG/Co-Pc is independent of disulfide concentration, which shows that these modified electrodes are only sensitive to the thiol. Graphite electrodes without modification are not sensitive to the concentration of thiols in the solution and the potential response is erratic.

JOSÉ H., ZAGAL; JAIME J.H., HENRIQUEZ.

377

POTENTIOMETRIC RESPONSE OF A GRAPHITE ELECTRODE MODIFIED WITH COBALT PHTHALOCYANINE FOR THIOLS AND DISULFIDES  

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Full Text Available We have investigated the potentiometric response of ordinary pyrolytic graphite electrodes (OPG modified with cobalt phthalocyanine (Co-Pc for thiols (R-SH 2-mercaptoethanol, L-cysteine and their corresponding disulfides (R-SS-R. Stable potentials are achieved after a few seconds of additions of different amounts of thiols to aqueous solutions of pH values between 11 and 4. Plots of potential vs. log [R-SH] give straight lines for all cases with slopes ca. -0.060 V with concentrations of the thiol varying from 10-5 up to 10-2 M. These measurements were conducted in the presence of air or oxygen. Under nitrogen, the slopes increase to -0.14 V. The potential response of OPG/Co-Pc is independent of disulfide concentration, which shows that these modified electrodes are only sensitive to the thiol. Graphite electrodes without modification are not sensitive to the concentration of thiols in the solution and the potential response is erratic.Se ha investigado la respuesta potenciométrica the electrodos de grafito pirolítico ordinario (OPG modificados con ftalocianina de cobalto (Co-Pc frente a los tioles (R-SH 2-mecaptoetanol y L-cisteína y los correspondientes disulfuros (R-SS-R. Al agregar pequeñas cantidades de estos tioles a soluciones acuosas con pH en el rango 11-4, se obtienen respuestas en potencial estables dentro de unos pocos segundos despues de las adiciones. Gráficas de potencial vs. log [R-SH] dan rectas para todos los casos, con pendientes cercanas a -0,060 V para concentraciones del tiol en el rango de 10-5 a 10-2 M. Estas medidas se efectuaron en presencia de aire u oxígeno. En atmósfera de nitrógeno, las pendientes de las gráficas suben a -0,14 V. El potencial de circuito abierto de los electrodos OPG/Co-Pc resultó ser independiente de la concentración de los disulfuros lo que indica que el potencial del electrodo modificado es sólo sensible al tiol. Los electrodos de grafito sin modificar frente a los tioles dan respuestas en potencial irreproducibles, lo que muestra la importancia de la presencia Co-Pc para obtener respuestas potenciométricas estables

JOSÉ H. ZAGAL

2000-06-01

378

Feedback Regulation of 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase in Livers of Mice Treated with Mevinolin, a Competitive Inhibitor of the Reductase  

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Compactin (ML-236B) and the related compound, mevinolin, are competitive inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG CoA reductase), the rate-controlling enzyme in cholesterol synthesis. Previous studies have shown that administration of compactin to cultured cells elicits a compensatory increase in the amount of HMG CoA reductase in the cells. A similar increase in HMG CoA reductase has been reported in livers of rats and mice that have been treated with compactin. In ...

Kita, Toru; Brown, Michael S.; Goldstein, Joseph L.

1980-01-01

379

Linked expressions of nap and nos genes in a Bradyrhizobium japonicum mutant with increased N(2)O reductase activity.  

Science.gov (United States)

To understand the mechanisms underlying the increased N2O reductase activity in the Bradyrhizobium japonicum 5M09 mutant from enrichment culture under N2O respiration, we analyzed the expression of genes encoding denitrification reductases and regulators. Our results suggest a common regulation of nap (encoding periplasmic nitrate reductase) and nos (encoding N2O reductase). PMID:23624475

Sánchez, Cristina; Itakura, Manabu; Mitsui, Hisayuki; Minamisawa, Kiwamu

2013-07-01

380

Immunological approach to the regulation of nitrate reductase in Monoraphidium braunii.  

Science.gov (United States)

The effects of different culture conditions on nitrate reductase activity and nitrate reductase protein from Monoraphidium braunii have been studied, using two different immunological techniques, rocket immunoelectrophoresis and an enzyme-linked immunosorbent assay, to determine nitrate reductase protein. The nitrogen sources ammonium and glutamine repressed nitrate reductase synthesis, while nitrite, alanine, and glutamate acted as derepressors. There was a four- to eightfold increase of nitrate reductase activity and a twofold increase of nitrate reductase protein under conditions of nitrogen starvation versus growth on nitrate. Nitrate reductase synthesis was repressed in darkness. However, when Monoraphidium was grown under heterotrophic conditions with glucose as the carbon and energy source, the synthesis of nitrate reductase was maintained. With ammonium or darkness, changes in nitrate reductase activity correlated fairly well with changes in nitrate reductase protein, indicating that in both cases loss of activity was due to repression and not to inactivation of the enzyme. Experiments using methionine sulfoximine, to inhibit ammonium assimilation, showed that ammonium per se and not a product of its metabolism was the corepressor of the enzyme. The appearance of nitrate reductase activity after transferring the cells to induction media was prevented by cycloheximide and by 6-methylpurine, although in this latter case the effect was observed only in cells preincubated with the inhibitor for 1 h before the induction period. PMID:2913954

Díez, J; López-Ruiz, A

1989-02-01

 
 
 
 
381

3-Oxoacyl-[ACP] reductase from oilseed rape (Brassica napus).  

Science.gov (United States)

3-Oxoacyl-[ACP] reductase (E.C. 1.1.1.100, alternatively known as beta-ketoacyl-[ACP] reductase), a component of fatty acid synthetase has been purified from seeds of rape by ammonium sulphate fractionation, Procion Red H-E3B chromatography, FPLC gel filtration and high performance hydroxyapatite chromatography. The purified enzyme appears on SDS-PAGE as a number of 20-30 kDa components and has a strong tendency to exist in a dimeric form, particularly when dithiothreitol is not present to reduce disulphide bonds. Cleveland mapping and cross-reactivity with antiserum raised against avocado 3-oxoacyl-[ACP] reductase both indicate that the multiple components have similar primary structures. On gel filtration the enzyme appears to have a molecular mass of 120 kDa suggesting that the native structure is tetrameric. The enzyme has a strong preference for the acetoacetyl ester of acyl carrier protein (Km = 3 microM) over the corresponding esters of the model substrates N-acetyl cysteamine (Km = 35 mM) and CoA (Km = 261 microM). It is inactivated by dilution but this can be partly prevented by the inclusion of NADPH. Using an antiserum prepared against avocado 3-oxoacyl-[ACP] reductase, the enzyme has been visualised inside the plastids of rape embryo and leaf tissues by immunoelectron microscopy. Amino acid sequencing of two peptides prepared by digestion of the purified enzyme with trypsin showed strong similarities with 3-oxoacyl-[ACP] reductase from avocado pear and the Nod G gene product from Rhizobium meliloti. PMID:1562581

Sheldon, P S; Kekwick, R G; Smith, C G; Sidebottom, C; Slabas, A R

1992-04-01

382

Sucrose mimics the light induction of Arabidopsis nitrate reductase gene transcription  

DEFF Research Database (Denmark)

Nitrate reductase, the first enzyme in nitrate assimilation, is located at the crossroad of two energy-consuming pathways: nitrate assimilation and carbon fixation. Light, which regulates the expression of many higher-plant carbon fixation genes, also regulates nitrate reductase gene expression. Located in the cytosol, nitrate reductase obtains its reductant not from photosynthesis but from carbohydrate catabolism. This relationship prompted us to investigate the indirect role that light might play, via photosynthesis, in the regulation of nitrate reductase gene expression. We show that sucrose can replace light in eliciting an increase of nitrate reductase mRNA accumulation in dark-adapted green Arabidopsis plants. We show further that sucrose alone is sufficient for the full expression of nitrate reductase genes in etiolated Arabidopsis plants. Finally, using a reporter gene, we show that a 2.7-kilobase region of 5' flanking sequence of the nitrate reductase gene is sufficient to confer the light or the sucrose response.

Cheng, Chi-Lien; Acedo, Gregoria N

1992-01-01

383

Recominant Pinoresino-Lariciresinol Reductase, Recombinant Dirigent Protein And Methods Of Use  

Science.gov (United States)

Dirigent proteins and pinoresinol/lariciresinol reductases have been isolated, together with cDNAs encoding dirigent proteins and pinoresinol/lariciresinol reductases. Accordingly, isolated DNA sequences are provided from source species Forsythia intermedia, Thuja plicata, Tsuga heterophylla, Eucommia ulmoides, Linum usitatissimum, and Schisandra chinensis, which code for the expression of dirigent proteins and pinoresinol/lariciresinol reductases. In other aspects, replicable recombinant cloning vehicles are provided which code for dirigent proteins or pinoresinol/lariciresinol reductases or for a base sequence sufficiently complementary to at least a portion of dirigent protein or pinoresinol/lariciresinol reductase DNA or RNA to enable hybridization therewith. In yet other aspects, modified host cells are provided that have been transformed, transfected, infected and/or injected with a recombinant cloning vehicle and/or DNA sequence encoding dirigent protein or pinoresinol/lariciresinol reductase. Thus, systems and methods are provided for the recombinant expression of dirigent proteins and/or pinoresinol/lariciresinol reductases.

Lewis, Norman G. (Pullman, WA); Davin, Laurence B. (Pullman, WA); Dinkova-Kostova, Albena T. (Baltimore, MD); Fujita, Masayuki (Kita-gun, JP), Gang; David R. (Ann Arbor, MI), Sarkanen; Simo (Minneapolis, MN), Ford; Joshua D. (Pullman, WA)

2003-10-21

384

Influence of extra-cellular and intra-cellular acting thiol oxidants on the "4"5calcium uptake by the islets of Langerhans of the rat  

International Nuclear Information System (INIS)

The glucose-stimulated calcium uptake by the islets of Langerhans is dependent on the intra-cellular GSH/GSSG ratios. The inhibition of calcium uptake is not the consequence of a direct oxidation of membrane-fixed thiol groups. In contrast, direct oxidation of extra cellular thiols leads to an increase in calcium uptake when intra-cellular oxidation is simultaneously prevented. Since this effect only occurs at high intra-cellular GSH/GSSG ratios it can be assumed that the redox state of extra-cellular thiols is dependent on the redox state of the intra-cellular GSH/GSSG ratios. These findings support the theory that the oxidation of extra-cellular thiols by thiol oxidants leads to an increase in calcium uptake and that the extent of uptake is higher, the more the redox state of the extra-cellular thiols tends towards the reduced state prior to oxidation. (orig./MG)

1981-01-01

385

Identification and characterization of 2-naphthoyl-coenzyme A reductase, the prototype of a novel class of dearomatizing reductases  

DEFF Research Database (Denmark)

The enzymatic dearomatization of aromatic ring systems by reduction represents a highly challenging redox reaction in biology and plays a key role in the degradation of aromatic compounds under anoxic conditions. In anaerobic bacteria, most monocyclic aromatic growth substrates are converted to benzoyl-coenzyme A (CoA), which is then dearomatized to a conjugated dienoyl-CoA by ATP-dependent or -independent benzoyl-CoA reductases. It was unresolved whether or not related enzymes are involved in the anaerobic degradation of environmentally relevant polycyclic aromatic hydrocarbons (PAHs). In this work, a previously unknown dearomatizing 2-naphthoyl-CoA reductase was purified from extracts of the naphthalene-degrading, sulphidogenic enrichment culture N47. The oxygen-tolerant enzyme dearomatized the non-activated ring of 2-naphthoyl-CoA by a four-electron reduction to 5,6,7,8-tetrahydro-2-naphthoyl-CoA. The dimeric 150â??kDa enzyme complex was composed of a 72â??kDa subunit showing sequence similarity to members of the flavin-containing 'old yellow enzyme' family. NCR contained FAD, FMN, and an iron-sulphur cluster as cofactors. Extracts of Escherichia coli expressing the encoding gene catalysed 2-naphthoyl-CoA reduction. The identified NCR is a prototypical enzyme of a previously unknown class of dearomatizing arylcarboxyl-CoA reductases that are involved in anaerobic PAH degradation; it fundamentally differs from known benzoyl-CoA reductases.

Eberlein, Christian; Estelmann, Sebastian

2013-01-01

386

Inhibition of mammalian thioredoxin reductase by black tea and its constituents: implications for anticancer actions.  

Science.gov (United States)

Black tea is recently reported to have anti-carcinogenic effects through pro-oxidant property, but the underlying mechanisms remain unclear. Mammalian cytosolic thioredoxin reductase (TrxR1) is well -known for its anti-oxidation activity. In this study, we found that black tea extract (BTE) and theaflavins (TFs), the major black tea polyphenols, inhibited the purified TrxR1 with IC(50) 44 microg/ml and 21+/-1 microg/ml, respectively. Kinetics of TFs exhibited a mixed type of competitive and non-competitive inhibition, with K(is) 4+/-1 microg/ml and K(ii) 26+/-5 microg/ml against coenzyme NADPH, and with K(is) 12+/-3 microg/ml and K(ii) 27+/-5 microg/ml against substrate DTNB. In addition, TFs inhibited TrxR1 in a time-dependent manner. In an equilibrium step, a reversible TrxR1-TFs complex (E*I) forms, which is followed by a slow irreversible first-order inactivation step. Rate constant of the inactivation was 0.7 min(-1), and dissociation constant of E*I was 51.9 microg/ml. Treatment of NADPH-reduced TrxR1 with TFs decreased 5-(Iodoacetamido) fluorescein incorporation, a fluorescent thiol-reactive reagent, suggesting that Sec/Cys residue(s) in the active site may be involved in the binding of TFs. The inhibitory capacity of TFs depends on their structure. Among the TFs tested, gallated forms had strong inhibitory effects. The interactions between TFs and TrxR1 were investigated by molecular docking, which revealed important features of the binding mechanism of theaflavins. An inhibitory effect of BTE on viability of HeLa cells was observed with IC(50) 29 microg/ml. At 33 microg/ml of BTE, TrxR1 activity in HeLa cells was decreased by 73% at 22 h after BTE treatment. TFs inhibited cell viability with IC(50) 10+/-4 microg/ml for HeLa cells and with IC(50) 20+/-5 microg/ml for EAhy926 cells. The cell susceptibility to TFs was inversely correlated to cellular levels of TrxR1. The inhibitory actions of TFs on TrxR1 may be an important mechanism of their anti-cancer properties. PMID:19059456

Du, Yatao; Wu, Yunfei; Cao, Xueli; Cui, Wei; Zhang, Huihui; Tian, Weixi; Ji, Mingjuan; Holmgren, Arne; Zhong, Liangwei

2009-03-01

387

The effects of acrolein on peroxiredoxins, thioredoxins, and thioredoxin reductase in human bronchial epithelial cells  

International Nuclear Information System (INIS)

Inhalation is a common form of exposure to acrolein, a toxic reactive volatile aldehyde that is a ubiquitous environmental pollutant. Bronchial epithelial cells would be directly exposed to inhaled acrolein. The thioredoxin (Trx) system is essential for the maintenance of cellular thiol redox balance, and is critical for cell survival. Normally, thioredoxin reductase (TrxR) maintains the cytosolic (Trx1) and mitochondrial (Trx2) thioredoxins in the reduced state, and the thioredoxins keep the peroxiredoxins (Prx) reduced, thereby supporting their peroxidase function. The effects of acrolein on TrxR, Trx and Prx in human bronchial epithelial (BEAS-2B) cells were determined. A 30-min exposure to 5 ?M acrolein oxidized both Trx1 and Trx2, although significant effects were noted for Trx1 at even lower acrolein concentrations. The effects on Trx1 and Trx2 could not be reversed by treatment with disulfide reductants. TrxR activity was inhibited 60% and >85% by 2.5 and 5 ?M acrolein, respectively. The endogenous electron donor for TrxR, NADPH, could not restore its activity, and activity did not recover in cells during a 4-h acrolein-free period in complete medium. The effects of acrolein on TrxR and Trx therefore extend beyond the duration of exposure. While there was a strong correlation between TrxR inhibition and Trx1 oxidation, the irreversible effects on Trx1 suggest direct effects of acrolein rather than loss of reducing equivalents from TrxR. Trx2 did not become oxidized until ?90% of TrxR was inhibited, but irreversible effects on Trx2 also suggest direct effects of acrolein. Prx1 (cytosolic) and Prx3 (mitochondrial) shifted to a largely oxidized state only when >90 and 100% of their respective Trxs were oxidized. Prx oxidation was readily reversed with a disulfide reductant, suggesting that Prx oxidation resulted from lack of reducing equivalents from Trx and not direct reaction with acrolein. The effects of acrolein on the thioredoxin system and peroxiredoxins could have important implications for cell survival, redox-sensitive cell signaling, and tolerance to other oxidant insults

2009-03-04

388

Study of the Thiol/Disulfide Redox Systems of the Anaerobe Desulfovibrio vulgaris Points Out Pyruvate:Ferredoxin Oxidoreductase as a New Target for Thioredoxin 1  

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Sulfate reducers have developed a multifaceted adaptative strategy to survive against oxidative stresses. Along with this oxidative stress response, we recently characterized an elegant reversible disulfide bond-dependent protective mechanism in the pyruvate:ferredoxin oxidoreductase (PFOR) of various Desulfovibrio species. Here, we searched for thiol redox systems involved in this mechanism. Using thiol fluorescent labeling, we show that glutathione is not the major thiol/disulfide balance-c...

Pieulle, Laetitia; Stocker, Pierre; Vinay, Manon; Nouailler, Matthieu; Vita, Nicolas; Brasseur, Gae?l; Garcin, Edwige; Sebban-kreuzer, Corinne; Dolla, Alain

2011-01-01

389

Mechanism of thiol-supported arsenate reduction mediated by phosphorolytic-arsenolytic enzymes: I. The role of arsenolysis.  

Science.gov (United States)

Several mammalian enzymes catalyzing the phosphorolytic-arsenolytic cleavage of their substrates (thus yielding arsenylated metabolites) have been shown to facilitate reduction of arsenate (AsV) to the more toxic arsenite (AsIII) in presence of their substrate and a thiol. These include purine nucleoside phosphorylase (PNP), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and glycogen phosphorylase-a (GPa). In this work, we tested further enzymes, the bacterial phosphotransacetylases (PTAs) and PNP, for AsV reduction. The PTAs, which arsenolytically cleave acetyl-CoA producing acetyl-arsenate, were compared with GAPDH, which can also form acetyl-arsenate by arsenolysis of its nonphysiological substrate, acetyl-phosphate. As these enzymes also mediated AsV reduction, we can assert that facilitation of thiol-dependent AsV reduction may be a general property of enzymes that catalyze phosphorolytic-arsenolytic reactions. Because with all such enzymes arsenolysis is obligatory for AsV reduction, we analyzed the relationship between these two processes in presence of various thiol compounds, using PNP. Although no thiol influenced the rate of PNP-catalyzed arsenolysis, all enhanced the PNP-mediated AsV reduction, albeit differentially. Furthermore, the relative capacity of thiols to support AsV reduction mediated by PNP, GPa, PTA, and GAPDH apparently depended on the type of arsenylated metabolites (i.e., arsenate ester or anhydride) produced by these enzymes. Importantly, AsV reduction by both acetyl-arsenate-producing enzymes (i.e., PTA and GAPDH) exhibited striking similarities in responsiveness to various thiols, thus highlighting the role of arsenylated metabolite formation. This observation, together with the finding that PNP-mediated AsV reduction lags behind the PNP-catalyzed arsenolysis lead to the hypothesis that arsenolytic enzymes promote reduction of AsV by forming arsenylated metabolites which are more reducible to AsIII by thiols than inorganic AsV. This hypothesis is evaluated in the adjoining paper. PMID:19474219

Németi, Balázs; Gregus, Zoltán

2009-08-01

390

Yeast genes involved in sulfur and nitrogen metabolism affect the production of volatile thiols from Sauvignon Blanc musts.  

Science.gov (United States)

Two volatile thiols, 3-mercaptohexan-1-ol (3MH), and 3-mercaptohexyl-acetate (3MHA), reminiscent of grapefruit and passion fruit respectively, are critical varietal aroma compounds in Sauvignon Blanc (SB) wines. These aromatic thiols are not present in the grape juice but are synthesized and released by the yeast during alcoholic fermentation. Single deletion mutants of 67 candidate genes in a laboratory strain of Saccharomyces cerevisiae were screened using gas chromatography mass spectrometry for their thiol production after fermentation of SB grape juice. None of the deletions abolished production of the two volatile thiols. However, deletion of 17 genes caused increases or decreases in production by as much as twofold. These 17 genes, mostly related to sulfur and nitrogen metabolism in yeast, may act by altering the regulation of the pathway(s) of thiol production or altering substrate supply. Deleting subsets of these genes in a wine yeast strain gave similar results to the laboratory strain for sulfur pathway genes but showed strain differences for genes involved in nitrogen metabolism. The addition of two nitrogen sources, urea and di-ammonium phosphate, as well as two sulfur compounds, cysteine and S-ethyl-L-cysteine, increased 3MH and 3MHA concentrations in the final wines. Collectively these results suggest that sulfur and nitrogen metabolism are important in regulating the synthesis of 3MH and 3MHA during yeast fermentation of grape juice. PMID:22684328

Harsch, Michael J; Gardner, Richard C

2013-01-01

391

Reduction of the secretory response to Escherichia coli heat-stable enterotoxin by thiol and disulfide compounds. [Mice  

Energy Technology Data Exchange (ETDEWEB)

We examined the effects of disulfide and thiol compounds on Escherichia coli heat-stable enterotoxin (ST) and cyclic GMP-induced secretion. Both cystamine and cystine (disulfide compounds) reduced the secretory responses to submaximal doses of ST in suckling mice (at 0.5 mumol per mouse) and reduced ST activation of guanylate cyclase (by 33 to 73% at 1 mM). In higher doses, cystamine completely eradicated a maximally effective ST dose as well. In addition, the sulfhydryl (thiol) compounds cysteamine, cysteine, and acetylcysteine strikingly reduced the secretory response and the guanylate cyclase response to ST. Neither the disulfide nor the thiol compounds tested reduced cyclic GMP-induced secretion. These studies suggest that disulfide and thiol compounds both block ST-induced secretion before its activation of guanylate cyclase. Taken with the work of others, these findings suggest that disulfide compounds may alter the oxidation reduction state of a cell or act directly on the guanylate cyclase enzyme, whereas thiol compounds may inactivate ST itself by breaking its disulfide bridges, or it may alter guanylate cyclase activation by ST. Both families of compounds deserve further consideration among potential antisecretory agents for application in the control of ST-induced diarrhea.

Greenberg, R.N.; Dunn, J.A.; Guerrant, R.L.

1983-07-01

392

Synthesis and Optical Properties of Thiol Functionalized CdSe/ZnS (Core/Shell) Quantum Dots by Ligand Exchange  

Energy Technology Data Exchange (ETDEWEB)

The colloidal photoluminescent quantum dots (QDs) of CdSe (core) and CdSe/ZnS (core/shell) were synthesized at different temperatures with different growth periods. The optical properties (i.e., UV/Vis spectra and photoluminescent emission spectra) of the resulting QDs were investigated. The CdSe/ZnS QDs exhibited higher photoluminescent (PL) efficiency and stability than their corresponding CdSe core QDs. Ligand exchange with various thiol molecules was performed to replace the initial surface passivation ligands, that is, trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP), and the optical properties of the surface-modified QDs were studied. The thiol ligand molecules used included 1,4-benzenedimethanethiol, 1,16-hexadecanedithiol, 1,11-undecanedithiol, 11-mercapto-1-undecanol, and 1,8 octanedithiol. After the thiol functionalization, the CdSe/ZnS QDs