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Sample records for gamma-ifn-inducible-lysosomal thiol reductase

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

    OpenAIRE

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

    2007-01-01

    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...

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

    Directory of Open Access Journals (Sweden)

    Dauter Zbigniew

    2004-03-01

    Full Text Available 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 single-wavelength anomalous diffraction. The fold is very similar to that of arsenate reductase, which is an extension of the thioredoxin fold. Conclusion Given the conservation of the functionally important residues and the ability to bind glutathione, YffB is likely to function as a GSH-dependent thiol reductase.

  3. Location of the redox-active thiols of ribonucleotide reductase: sequences similarity between the Escherichia coli and Lactobacillus leichmannii enzymes

    International Nuclear Information System (INIS)

    The redox-active thiols of Escherichia coli ribonucleoside diphosphate reductase and of Lactobacillus leichmannii ribonucleoside triphosphate reductase have been located by a procedure involving (1) prereduction of enzyme with dithiothreitol, (2) specific oxidation of the redox-active thiols by treatment with substrate in the absence of exogenous reductant, (3) alkylation of other thiols with iodoacetamide, and (4) reduction of the disulfides with dithiothreitol and alkylation with [1-14C]iodoacetamide. The dithiothreitol-reduce E. coli B1 subunit is able to convert 3 equiv of CDP to dCDP and is labeled with 5.4 equiv of 14C. Sequencing of tryptic peptides shows that 2.8 equiv of 14C is on cysteines-752 and -757 at the C-terminus of B1, while 1.0-1.5 equiv of 14C is on cysteines-222 and -227. It thus appears that two sets of redox-active dithiols are involved in substrate reduction. The L. leichmannii reductase is able to convert 1.1 equiv of CTP to dCTP and is labeled with 2.1 equiv of 14C. Sequencing of tryptic peptides shows that 1.4 equiv of 14C is located on the two cysteines of C-E-G-G-A-C-P-I-K. This peptide shows remarkable and unexpected similarity to the thiol-containing region of the C-terminal peptide of E. coli B1, C-E-S-G-A-C-K-I

  4. Gamma-interferon-inducible lysosomal thiol reductase is upregulated in human melanoma.

    Science.gov (United States)

    Nguyen, Jennifer; Bernert, Richard; In, Kevin; Kang, Paul; Sebastiao, Noemi; Hu, Chengcheng; Hastings, K Taraszka

    2016-04-01

    T-cell-mediated immunity has the ability to produce durable antimelanoma responses, resulting in improved survival of patients with advanced melanoma. Antigen presentation is a key determinant of T-cell responses. Gamma-interferon-inducible lysosomal thiol reductase (GILT) is critical for MHC class II-restricted presentation of multiple melanoma antigens to CD4+ T cells. However, GILT expression in melanoma has not been defined. We evaluated GILT and MHC class II expression in human primary and metastatic melanomas and nevi using immunohistochemical analysis. GILT staining in melanocytes was observed in 70% of primary and 58% of metastatic melanomas versus 0% of nevi. When present, the GILT staining intensity in melanocytes was typically faint. Both GILT and MHC class II expression were increased in melanocytes of primary and metastatic melanomas compared with nevi. GILT staining in antigen-presenting cells (APCs) was detected in 100% of primary and metastatic melanomas versus 31% of nevi, and it was typically intense. GILT expression was increased in APCs of primary and metastatic melanomas compared with nevi, whereas MHC class II had equivalent high expression in APCs of all melanocytic lesions. GILT staining in keratinocytes was detected in 67% of primary melanomas versus 14% of nevi and 6% of metastatic melanomas. GILT, but not MHC class II, expression was increased in keratinocytes of primary melanomas compared with nevi and metastases. GILT expression is anticipated to result in improved presentation of melanoma antigens and more effective antimelanoma T-cell responses. GILT expression may be a biomarker of immune recognition of melanoma. PMID:26930048

  5. Enzymatic reduction of disulfide bonds in lysosomes: Characterization of a Gamma-interferon-inducible lysosomal thiol reductase (GILT)

    Science.gov (United States)

    Arunachalam, Balasubramanian; Phan, Uyen T.; Geuze, Hans J.; Cresswell, Peter

    2000-01-01

    Proteins internalized into the endocytic pathway are usually degraded. Efficient proteolysis requires denaturation, induced by acidic conditions within lysosomes, and reduction of inter- and intrachain disulfide bonds. Cytosolic reduction is mediated enzymatically by thioredoxin, but the mechanism of lysosomal reduction is unknown. We describe here a lysosomal thiol reductase optimally active at low pH and capable of catalyzing disulfide bond reduction both in vivo and in vitro. The active site, determined by mutagenesis, consists of a pair of cysteine residues separated by two amino acids, similar to other enzymes of the thioredoxin family. The enzyme is a soluble glycoprotein that is synthesized as a precursor. After delivery into the endosomal/lysosomal system by the mannose 6-phosphate receptor, N- and C-terminal prosequences are removed. The enzyme is expressed constitutively in antigen-presenting cells and induced by IFN-? in other cell types, suggesting a potentially important role in antigen processing.

  6. Differential responses to salinity of two Atriplex halimus populations in relation to organic solutes and antioxidant systems involving thiol reductases.

    Science.gov (United States)

    Bouchenak, Fatima; Henri, Patricia; Benrebiha, Fatma-Zohra; Rey, Pascal

    2012-10-15

    Atriplex halimus L. is a xero-halophyte species widespread in the Mediterranean basin. The tolerance to water stress and high salinity of two Atriplex populations from semi-arid (Djelfa) and arid saline (Laghouat) Algerian regions has been investigated in relation with organic solutes and antioxidant systems. Whereas no noticeable difference was observed between the two populations under water stress resulting from withholding watering or PEG treatment, Laghouat plants display significantly higher fresh and dry weights than Djelfa plants when exposed to high salinity. At 300mM NaCl, Laghouat plants exhibit higher concentrations in Na(+), proline and quaternary ammonium compounds, and a higher catalase activity than Djelfa plants. We then analysed the involvement of recently characterized plastidial thiol reductases, peroxiredoxins (Prxs) and methionine sulphoxide reductases (MSRs), key enzymes scavenging organic peroxides and repairing oxidized proteins, respectively. Upon salt treatment (300mM NaCl), we observed higher amounts of PrxQ and over-oxidized 2-Cys Prx in Laghouat than in Djelfa. An increased abundance of plastidial MSRA and a higher total MSR activity were also noticed in Laghouat plants treated with 300mM NaCl compared to Djelfa ones. We propose that mechanisms based on organic solutes and antioxidant enzymes like catalases, peroxiredoxins and MSRs party underlie the better tolerance of the Laghouat population to high salt. PMID:22840322

  7. Role of GSSG-reductase and a thiol oxidant diethylmaleate (DEM) in skin tumorigenesis induced by jute batching oil.

    Science.gov (United States)

    Antony, M; Kumar, S; Mehrotra, N K

    1989-09-01

    Single topical application of jute batching oil (JBO-P) elevated the status of enzyme GSSG-reductase in mouse skin and multiple applications produced a persistent increase in the enzyme levels. Also an increase in NADPH-dependent GSSG-reductase activity was registered after single topical application of known carcinogenic polyaromatic hydrocarbons (PAHs), e.g. benzo(a)pyrene (BaP), 7,12-dimethyl-benzanthracene (DMBA) and 3-methylcholanthrene (3-MC). This suggests that the change in GSSG-reductase activity induced by JBO-P is intrinsic to its tumorigenic activity rather than the toxic effect of the oil. Pretreatment of mouse skin with diethylmaleate (DEM), an SH-inactivating agent, increases the latent period of JBO-P induced tumorigenesis. No tumour was recorded in animals belonging to Group IV (DEM + JBO) while in animals belonging to Group II (JBO-P alone) 100% tumorigenesis was recorded during the period of study (i.e. up to 20 wk). PMID:2781594

  8. Identification of three IFN-? inducible lysosomal thiol reductase (GILT)-like genes in mud crab Scylla paramamosain with distinct gene organizations and patterns of expression.

    Science.gov (United States)

    Huang, Wen-Shu; Duan, Li-Peng; Huang, Bei; Zhou, Li-Hong; Liang, Ying; Tu, Chen-Ling; Zhang, Fang-Fang; Nie, Pin; Wang, Tiehui

    2015-10-01

    Vertebrate gamma-interferon inducible lysosomal thiol reductase (GILT) is an IFN-?-inducible protein and is involved in MHCII-restricted antigen processing and cross-presentation of MHCI-restricted antigens in adaptive immunity. Outside of the endocytic MHC pathway, GILT regulates the cellular redox state, inhibits T cell activation, neutralizes extracellular pathogens and is also a host factor of some bacterial pathogens. In this report, we isolated and characterized three divergent GILT-like genes, GILT1, GILT2 and GILT3, which share only 30.9-40.4% identities in a crustacean mud crab Scylla paramamosain. Whilst the crab GILT1 and GILT3 possess four and five exons, respectively, the GILT2 is intronless, suggesting that GILT2 may arise from a recent retroposition event. The invertebrate GILT-like genes have diverse gene organizations and may be evolved in a species/lineage-specific manner as suggested by phylogenetic tree analysis. The amino acid sequences equivalent to human mature GILT are well conserved, including the GILT signature and nine of the ten cysteine residues that potentially form 5 disulfide bonds in human GILT, across the animal kingdom. However, most invertebrate GILT-like molecules lack the human-type N-terminal propeptide, as well as the human-type C-terminal with a conserved cysteine residue, suggesting differences in post translational processing and mode of action. All the three GILT-like genes are highly expressed in the hepatopancreas and up-regulated by pathogenic bacterial infection suggesting a role in immune defense against bacterial diseases. This study may provide the basis for further investigation of the expanding functions of GILT-like molecules in immunity and other physiological processes in mud crabs and other animals. PMID:26051415

  9. Increase in Thiol Oxidative Stress via Glutathione Reductase Inhibition as a Novel Approach to Enhance Cancer Sensitivity to X-Ray Irradiation

    OpenAIRE

    Zhao, Yong; Seefeldt, Teresa; Chen, Wei; Carlson, Laura; Stoebner, Adam; Hanson, Sarah; Foll, Ryan; Matthees, Duane P.; Palakurthi, Srinath; Guan, Xiangming

    2009-01-01

    Depletion of reduced form glutathione (GSH) has been extensively studied for its effect on sensitizing cancer to radiation. However, little is known about the effect of thiol oxidative stress created through an increase in glutathione disulfide (GSSG) on cancer sensitivity to radiation. In this study, an increase in GSSG was effectively created by 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylthiocarbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (2-AAPA), an irreversible glut...

  10. Measurement and meaning of cellular thiol:disufhide redox status.

    Science.gov (United States)

    Comini, Marcelo A

    2016-02-01

    The functional group of cysteine is a thiol group (SH) that, due to its chemical reactivity, is able to undergo a wide array of modifications each with the potential to confer a different property or function to the molecule harboring this residue. Most of these modifications involve the reversible oxidation of the thiol to sulfenic acid (SOH), and disulfide, including intra- and intermolecular disulfides between polypeptides and glutathione (glutathionylation). The reversibility of these oxidations allows thiol groups to serve as versatile chemical and structural transducing elements in several low molecular mass metabolites and proteins. A plethora of cellular functions such as DNA and protein synthesis, protein secretion, cytoskeleton architecture, differentiation, apoptosis, and anti-oxidant defense, are recognized to be modulated, at certain stage, by thiol-disulfide exchange mechanisms of redox active thiol groups. All organisms are equipped with enzymatic systems composed by NADPH-dependent reductases, redoxins, and peroxidases that provide kinetic control of global thiol-redox homeostasis as well as target selectivity. These redox systems are distributed in different subcellular compartments and are not in equilibrium with each other. In consequence, measuring cellular thiol-disulfide status represents a challenge for studies aimed to obtain dynamic and spatio-temporal resolution. This review provides a summary of the methods and tools available to quantify the thiol redox status of cells. PMID:26695718

  11. Thiol biochemistry of prokaryotes

    Science.gov (United States)

    Fahey, Robert C.

    1986-01-01

    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.

  12. The orphan protein bis-?-glutamylcystine reductase joins the pyridine nucleotide-disulfide reductase family

    Science.gov (United States)

    Kim, Juhan; Copley, Shelley D.

    2014-01-01

    Facile DNA sequencing became possible decades after many enzymes had been purified and characterized. Consequently, there are still “orphan” enyzmes whose activity is known but the genes that encode them have not been identified. Identification of the genes encoding orphan enzymes is important because it allows correct annotation of genes of unknown function or with mis-assigned function. Bis-?-glutamylcystine reductase (GCR) is an orphan protein that was purified in 1988. This enzyme catalyzes the reduction of bis-?-glutamylcystine. ?-Glutamylcysteine (?-Glu-Cys) is the major low molecular weight thiol in halobacteria. We purified GCR from Halobacterium sp. NRC-1 and identified the sequence of 23 tryptic peptides by NanoLC electrospray ionization tandem mass spectrometry. These peptides cover 62% of the protein predicted to be encoded by a gene in Halobacterium sp. NRC-1 that is annotated as mercuric reductase. GCR and mercuric reductase activities were assayed using enzyme that was expressed in E. coli and re-folded from inclusion bodies. The enzyme had robust GCR activity, but no mercuric reductase activity. The genomes of most, but not all, halobacteria for which whole genome sequences are available have close homologs of GCR, suggesting that there is more to be learned about the low molecular weight thiols used in halobacteria. PMID:23560638

  13. Apoptosis induction in lymphoma cells: thiol deprivation versus thiol excess.

    Czech Academy of Sciences Publication Activity Database

    Ková?, Jan; Štýbrová, Hana; Truksa, Jaroslav; Sp?váková, Kate?ina; Valenta, Tomáš

    2002-01-01

    Ro?. 48, ?. 2 (2002), s. 58-68. ISSN 0015-5500 R&D Projects: GA ?R GA301/97/1029; GA ?R GA301/01/0041 Institutional research plan: CEZ:AV0Z5052915 Keywords : Apoptosis induction * thiol deprivation * thiol excess Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 0.615, year: 2002

  14. Thiol Reactive Probes and Chemosensors

    Directory of Open Access Journals (Sweden)

    Binghe Wang

    2012-11-01

    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.

  15. Voltammetry and Electrocatalysis of Achrornobacter Xylosoxidans Copper Nitrite Reductase on Functionalized Au(111)-Electrode Surfaces

    DEFF Research Database (Denmark)

    Welinder, Anna C.; Zhang, Jingdong; Hansen, Allan G.; Moth-Poulsen, Kasper; Christensen, Hans E.M.; Kuznetsov, Alexander M.; Bjørnholm, Thomas; Ulstrup, Jens

    2007-01-01

    planar electrode surfaces is a step towards the resolution of this central issue. We report here the voltammetry of copper nitrite reductase (CNiR, Achromobacter xylosoxidons) on Au(111)-electrode surfaces modified by monolayers of a broad variety of thiol-based linker molecules. These represent...

  16. Quantification of thiols and disulfides

    DEFF Research Database (Denmark)

    Winther, Jakob R.; Thorpe, Colin

    2014-01-01

    Disulfide bond formation is a key posttranslational modification, with implications for structure, function and stability of numerous proteins. While disulfide bond formation is a necessary and essential process for many proteins, it is deleterious and disruptive for others. Cells go to great lengths to regulate thiol-disulfide bond homeostasis, typically with several, apparently redundant, systems working in parallel. Dissecting the extent of oxidation and reduction of disulfides is an ongoing challenge due, in part, to the facility of thiol/disulfide exchange reactions.

  17. Flow cytometric determination of cellular thiols.

    Science.gov (United States)

    Sen, C K; Roy, S; Packer, L

    1999-01-01

    Several biochemical techniques are based on chromatography or electrophoresis for the determination of thiols from biological samples. These techniques are indispensable for the accurate and sensitive detection of specific thiols. Flow cytometric determination of cellular thiols is a powerful technique that is perhaps best suited for clinical application, particularly for cells in blood or other body fluids. Information can be obtained from a small sample amount with a relatively little and quick sample treatment. This technique offers an unique advantage to study the thiol status of a subset of cells because data are collected from individual cells. Multiparameter flow cytometry allows the study of different subsets of immunotyped cells. A major drawback of the flow cytometric method is the lack of specificity for the determination of distinct thiols. The reaction between MBB and thiols is not specific for any particular intracellular thiol, although almost all of the entire thiol-reacted bimane emission is specific for thiols in general. This limitation can be partly overcome by the treatment of cells with known thiol regulatory agents as described in the section on the differential assessment of cellular thiols. PMID:9916203

  18. Cellular thiols as a determinant of responsiveness to menadione in cardiomyocytes.

    Science.gov (United States)

    Tzeng, W F; Chiou, T J; Wang, C P; Lee, J L; Chen, Y H

    1994-07-01

    The role of intracellular thiols in menadione-mediated toxicity was studied in neonatal rat cardiomyocytes. The sensitivity of cardiomyocytes to menadione was greater than that of skeletal muscle cells and 3T3 fibroblasts. Before cell degeneration, menadione induced marked depletion of intracellular thiols and an increase of oxidized glutathione. The sensitivity of these cells to menadione correlated with the level of depletion of intracellular thiols. After incubation of cardiomyocytes with menadione, glutathione reductase activity was inhibited and lipid peroxidation was increased. Both dicumarol (an inhibitor of DT-diaphorase) and diethyldithiocarbamate (an inhibitor of superoxide dismutase) enhanced the capacity of menadione to induce cellular damage and to cause depletion of intracellular glutathione. Decreasing intracellular glutathione by pretreatment of cells with N-ethylmaleimide or buthionine sulphoximine also increased menadione-induced cell degeneration. Preincubation with cysteine or dithiothreitol suppressed the capacity of menadione to damage the cells. Menadione-induced lipid peroxidation was also suppressed by the same treatment. These results show that the oxidative stress induced by menadione in cardiomyocytes results in the depletion of glutathione and protein thiols. Both DT-diaphorase and superoxide dismutase can protect cells from the toxicity of menadione. Cellular thiols are determinants of the responsiveness to menadione. PMID:7966357

  19. Synthesis of cyclic, multivalent Arg-Gly-Asp using sequential thiol-ene/thiol-yne photoreactions

    OpenAIRE

    Aimetti, Alex A.; Feaver, Kristen R.; Anseth, Kristi S.

    2010-01-01

    A unique method has been developed for the formation of multivalent cyclic peptides. This procedure exploits on-resin peptide cyclization using a photoinitiated thiol-ene click reaction and subsequent clustering using thiol-yne photochemistry. Both reactions utilize the sulfhydryl group on natural cysteine amino acids to participate in the thiol-mediated reactions.

  20. Flow cytometry techniques for studying cellular thiols.

    Science.gov (United States)

    Durand, R E; Olive, P L

    1983-09-01

    Cellular thiols, and especially glutathione, act as scavenger nucleophiles and can protect against toxicity, mutagenicity, or transformation by ionizing radiation and many carcinogens. Development of a rapid assay to quantitate the cellular content of thiols could thus be useful in assessing or predicting cellular risk to damage. Several fluorescent thiol-reactive drugs, usually maleimide or bromobimane derivatives, have been described for use in histopathology. Most of these agents do not distinguish between protein and nonprotein thiols, and virtually all of these fluorescent stains have normally been used after fixation of the cells or tissues. We have found that some of the probes will, however, rapidly penetrate and bind within viable cells with little associated cytotoxicity; the amount bound can be easily quantified using flow cytometry. We have used several of these agents, in conjunction with fluorescence-activated cell sorting in V79 spheroids, to examine the thiol content of cells as a function of their depth or position in the spheroid. Additionally, the radiation response of cells from different depths has been assessed following addition of exogenous thiols including glutathione and WR-2721, or after treatment with thiol-depleting agents, including DL-buthionine-S,R-sulfoximine (BSO), diethylmaleate (DEM), and dimethylfumarate (DMF). Our studies indicate that examination of the thiol content and radiation response of the sorted cells provides an improved understanding of the modes of action of these compounds. PMID:6193555

  1. Flow cytometry techniques for studying cellular thiols

    International Nuclear Information System (INIS)

    Cellular thiols, and especially glutathione, act as scavenger nucleophiles and can protect against toxicity, mutagenicity, or transformation by ionizing radiation and many carcinogens. Development of a rapid assay to quantitate the cellular content of thiols could thus be useful in assessing or predicting cellular risk to damage. Several fluorescent thiol-reactive drugs, usually maleimide or bromobimane derivatives, have been described for use in histopathology. Most of these agents do not distinguish between protein and nonprotein thiols, and virtually all of these fluorescent stains have normally been used after fixation of the cells or tissues. We have found that some of the probes will, however, rapidly penetrate and bind within viable cells with little associated cytotoxicity; the amount bound can be easily quantified using flow cytometry. We have used several of these agents, in conjunction with fluorescence-activated cell sorting in V79 spheroids, to examine the thiol content of cells as a function of their depth or position in the spheroid. Additionally, the radiation response of cells from different depths as been assessed following addition of exogenous thiols including glutathione and WR-2721, or after treatment with thiol-depleting agents, including DL-buthionine-S,R-sulfoximine (BSO), diethylmaleate (DEM), and dimethylfumarate (DMF). Our studies indicate that examination of the thiol content and radiation response of the sorted cells provides an improved understanding of the modes of action of these compounds

  2. Flow cytometry techniques for studying cellular thiols

    Energy Technology Data Exchange (ETDEWEB)

    Durand, R.E.; Olive, P.L.

    1983-09-01

    Cellular thiols, and especially glutathione, act as scavenger nucleophiles and can protect against toxicity, mutagenicity, or transformation by ionizing radiation and many carcinogens. Development of a rapid assay to quantitate the cellular content of thiols could thus be useful in assessing or predicting cellular risk to damage. Several fluorescent thiol-reactive drugs, usually maleimide or bromobimane derivatives, have been described for use in histopathology. Most of these agents do not distinguish between protein and nonprotein thiols, and virtually all of these fluorescent stains have normally been used after fixation of the cells or tissues. We have found that some of the probes will, however, rapidly penetrate and bind within viable cells with little associated cytotoxicity; the amount bound can be easily quantified using flow cytometry. We have used several of these agents, in conjunction with fluorescence-activated cell sorting in V79 spheroids, to examine the thiol content of cells as a function of their depth or position in the spheroid. Additionally, the radiation response of cells from different depths as been assessed following addition of exogenous thiols including glutathione and WR-2721, or after treatment with thiol-depleting agents, including DL-buthionine-S,R-sulfoximine (BSO), diethylmaleate (DEM), and dimethylfumarate (DMF). Our studies indicate that examination of the thiol content and radiation response of the sorted cells provides an improved understanding of the modes of action of these compounds.

  3. Protein Thiol Modifications Visualized In Vivo

    Directory of Open Access Journals (Sweden)

    Leichert Lars I

    2004-01-01

    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.

  4. Functional Analysis of Free Methionine-R-sulfoxide Reductase from Saccharomyces cerevisiae*S?

    OpenAIRE

    Le, Dung Tien; Lee, Byung Cheon; Marino, Stefano M.; Zhang, Yan; Fomenko, Dmitri E; Kaya, Alaattin; Hacioglu, Elise; Kwak, Geun-Hee; Koc, Ahmet; Kim, Hwa-Young; GLADYSHEV, Vadim N.

    2009-01-01

    Methionine sulfoxide reductases (Msrs) are oxidoreductases that catalyze thiol-dependent reduction of oxidized methionines. MsrA and MsrB are the best known Msrs that repair methionine-S-sulfoxide (Met-S-SO) and methionine-R-sulfoxide (Met-R-SO) residues in proteins, respectively. In addition, an Escherichia coli enzyme specific for free Met-R-SO, designated fRMsr, was recently discovered. In this work, we carried out comparative genomic and experimental analyses to ex...

  5. The Effects of Acrolein on Peroxiredoxins, Thioredoxins, and Thioredoxin Reductase in Human Bronchial Epithelial Cells

    OpenAIRE

    Myers, Charles R; Myers, Judith M.

    2008-01-01

    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...

  6. Role of thiols in cellular response to radiation and drugs. Symposium: thiols

    International Nuclear Information System (INIS)

    Cellular nonprotein thiols (NPSH) consist of glutathione (GSH) and other low molecular weight species such as cysteine, cysteamine, and coenzyme. A GSH is usually less than the total cellular NPSH, and with thiol reactive agents, such as diethyl maleate (DEM), its rate of depletion is in part dependent upon the cellular capacity for its resynthesis. If resynthesis is blocked by buthionine-S,R-sulfoximine(BSO), the NPSH, including GSH, is depleted more rapidly, Cellular thiol depletion by diamide, N-ethylmaleimide, and BSO may render oxygenated cells more sensitive to radiation. These cells may or may not show a reduction in the oxygen enhancement ratio (OER). Human A549 lung carcinoma cells depleted of their NPSH either by prolonged culture or by BSO treatment do not show a reduced OER but do show increased aerobic responses to radiation. Other nitrocompounds, such as misonidazole, are activated under hypoxic conditions to radical intermediates. When cellular thiols are depleted peroxide is formed. Under hypoxic conditions thiols are depleted because metabolically reduced intermediates react with GSH instead of oxygen. Thiol depletion, under hypoxic conditions, may be the reason that misonidazole and other nitrocompounds show an extra enhancement ratio with hypoxic cells. Thiol depletion by DEM or BSO alters the radiation response of hypoxic cells to misonidazole. In conclusion, we propose an altered thiol model which includes a mechanism for thiol involvement in the aerobic radiation response of cells

  7. Herpes simplex ribonucleotide reductase

    OpenAIRE

    Ingemarson, Rolf

    1989-01-01

    In all bacterial, plant and animal cells, as well as in many viruses, genetic information resides in DNA (deoxyribonucleic acid). Replication of DNA is essential for proliferation, and DNA-containing viruses (such as herpesviruses) must carry out this process within the mammalian cells they infect. The enzyme ribonucleotide reductase catalyzes the first unique step leading to the production of the four deoxy-ribonucleotides used to make DNA. Each deoxyribonucleotide is produced by reduction o...

  8. 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 [125I]-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

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

    Directory of Open Access Journals (Sweden)

    B. Leite

    2002-06-01

    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.

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

    Scientific Electronic Library Online (English)

    B., Leite; M.L., Ishida; E., Alves; H., Carrer; S.F., Pascholati; E.W., Kitajima.

    2002-06-01

    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.

  11. Roles of thiols in cellular radiosensitivity

    International Nuclear Information System (INIS)

    Cellular thiols appear to have two separable mechanisms for influencing cellular radiosensitivity: (1) a direct role, through radical scavenging and/or hydrogen donation processes, and (2) an indirect role, regulating the amount of oxygen (or other electron affinic sensitizer) able to reach the radiosensitive targets of the cell. The contribution of each is easily measured with multicell spheroids, using fluorescence activated cell sorting techniques for selective recovery of cells from any depth within spheroids. It was found that the region in the spheroid over which the transition from aerobic to anoxic conditions occurs is highly dependent on cellular thiol levels. Combining thiol depletion by DL-buthionine-S,R-sulfoximine (BSO) and electron affinic radiosensitization using misonidazole resulted in a markedly potentiated response to radiation

  12. Thiol modification in kidney: Implications for radioprotection

    International Nuclear Information System (INIS)

    Kidney radiosensitivity is frequently a dose-limiting factor when planning abdominal radiation therapy. In addition to its clinical importance, the kidney has unusual transport and metabolic activity such as high gamma-glutamyl transpeptidase (Meister Methods in Enzymol, vol. 113, pg. 571-585, 1985), making it an ideal organ to study thiol modification. Although glutahione has been most extensively investigated, attention to other thiols may be also be of interest, since some thiols may be more effective as radioprotectors. Glutathione, glutathione ester, and cysteine concentrations in the kidney can be modified. The authors believe is cysteine is an attractive agent for kidney radioprotection. The data is used in conjunction with results from radiochemical studies with model systems to design strategies for kidney radioprotection

  13. Improvement of oxidized glutathione fermentation by thiol redox metabolism engineering in Saccharomyces cerevisiae.

    Science.gov (United States)

    Hara, Kiyotaka Y; Aoki, Naoko; Kobayashi, Jyumpei; Kiriyama, Kentaro; Nishida, Keiji; Araki, Michihiro; Kondo, Akihiko

    2015-11-01

    Glutathione is a valuable tripeptide widely used in the pharmaceutical, food, and cosmetic industries. In industrial fermentation, glutathione is currently produced primarily using the yeast Saccharomyces cerevisiae. Intracellular glutathione exists in two forms; the majority is present as reduced glutathione (GSH) and a small amount is present as oxidized glutathione (GSSG). However, GSSG is more stable than GSH and is a more attractive form for the storage of glutathione extracted from yeast cells after fermentation. In this study, intracellular GSSG content was improved by engineering thiol oxidization metabolism in yeast. An engineered strain producing high amounts of glutathione from over-expression of glutathione synthases and lacking glutathione reductase was used as a platform strain. Additional over-expression of thiol oxidase (1.8.3.2) genes ERV1 or ERO1 increased the GSSG content by 2.9-fold and 2.0-fold, respectively, compared with the platform strain, without decreasing cell growth. However, over-expression of thiol oxidase gene ERV2 showed almost no effect on the GSSG content. Interestingly, ERO1 over-expression did not decrease the GSH content, raising the total glutathione content of the cell, but ERV1 over-expression decreased the GSH content, balancing the increase in the GSSG content. Furthermore, the increase in the GSSG content due to ERO1 over-expression was enhanced by additional over-expression of the gene encoding Pdi1, whose reduced form activates Ero1 in the endoplasmic reticulum. These results indicate that engineering the thiol redox metabolism of S. cerevisiae improves GSSG and is critical to increasing the total productivity and stability of glutathione. PMID:26239069

  14. Quantifying the global cellular thiol–disulfide status

    OpenAIRE

    Hansen, Rosa E.; Roth, Doris; Winther, Jakob R.

    2009-01-01

    It is widely accepted that the redox status of protein thiols is of central importance to protein structure and folding and that glutathione is an important low-molecular-mass redox regulator. However, the total cellular pools of thiols and disulfides and their relative abundance have never been determined. In this study, we have assembled a global picture of the cellular thiol–disulfide status in cultured mammalian cells. We have quantified the absolute levels of protein thiols, protein disu...

  15. Photopolymerized Thiol-Ene Systems as Shape Memory Polymers

    OpenAIRE

    Nair, Devatha P.; Cramer, Neil B.; Scott, Timothy F.; Bowman, Christopher N.; Shandas, Robin

    2010-01-01

    In this study we introduce the use of thiol-ene photopolymers as shape memory polymer systems. The thiol-ene polymer networks are compared to a commonly utilized acrylic shape memory polymer and shown to have significantly improved properties for two different thiol-ene based polymer formulations. Using thermomechanical and mechanical analysis, we demonstrate that thiol-ene based shape memory polymer systems have comparable thermomechanical properties while also exhibiting a number of advanta...

  16. Synthesis of bisnaphthyl based thiol stabilized gold nanoparticles

    International Nuclear Information System (INIS)

    Bis naphthyl based thiol stabilized gold nanoparticles were synthesized by the chemical reduction of corresponding precursor, obtained from Au(III) salt with thiol ligand 4. The organo thiol ligand 4 were prepared from 1,1/sup '/-binaphth-2,2/sup '/-ol in three steps. Furthermore, the photophysical activity of these Au-NPs was also determined. (author)

  17. Total Thiols: Biomedical Importance And Their Alteration In Various Disorders

    Directory of Open Access Journals (Sweden)

    Mungli Prakash

    2009-09-01

    Full Text Available Thiols are the organic compounds that contain a sulphydryl group. Among all the antioxidants that are available in the body, thiols constitute the major portion of the total body antioxidants and they play a significant role in defense against reactive oxygen species. Total thiols composed of both intracellular and extracellular thiols either in the free form as oxidized or reduced glutathione, or thiols bound to proteins. Among the thiols that are bound to proteins, albumin makes the major portion of the protein bound thiols, which binds to sufhydryl group at its cysteine-34 portion. Apart from their role in defense against free radicals, thiols share significant role in detoxification, signal transduction, apoptosis and various other functions at molecular level. The thiol status in the body can be assessed easily by determining the serum levels of thiols. Decreased levels of thiols has been noted in various medical disorders including chronic renal failure and other disorders related to kidney, cardiovascular disorders, stroke and other neurological disorders, diabetes mellitus, alcoholic cirrhosis and various other disorders. Therapy using thiols has been under investigation for certain disorders.

  18. Purification and characterization of morphinone reductase from Pseudomonas putida M10.

    Science.gov (United States)

    French, C E; Bruce, N C

    1994-07-01

    The NADH-dependent morphinone reductase from Pseudomonas putida M10 catalyses the reduction of morphinone and codeinone to hydromorphone and hydrocodone respectively. Morphinone reductase was purified from crude cell extracts to apparent homogeneity in a single affinity-chromatography step using Mimetic Yellow 2. The purified enzyme was a dimeric flavoprotein with two identical subunits of M(r) 41,100, binding non-covalently one molecule of FMN per subunit. The N-terminal sequence was PDTSFSNPGLFTPLQ. Morphinone reductase was active against morphinone, codeinone, neopinone and 2-cyclohexen-1-one, but not against morphine, codeine or isocodeine. The apparent Km values for codeinone and 2-cyclohexen-1-one were 0.26 mM and 5.5 mM respectively. The steroids progesterone and cortisone were potent competitive inhibitors; the apparent K1 for cortisone was 35 microM. The pH optimum for codeinone reduction was 8.0 in phosphate buffer. No reverse reaction could be detected, and NADPH could not be used as a reducing substrate in place of NADH. Morphinone reductase activity was strongly inhibited by 0.01 mM CuSO4 and p-hydroxymercuribenzoate, suggesting the presence of a vital thiol group. Steady-state kinetic studies suggested a Ping Pong (substituted enzyme) kinetic mechanism; however, product-inhibition patterns were inconsistent with a classical Ping Pong mechanism. Morphinone reductase may, like several other flavoprotein dehydrogenases, operate by a hybrid two-site Ping Pong mechanism. PMID:8037698

  19. Hypochlorite-induced oxidation of thiols

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan; Hawkins, C L

    2000-01-01

    Activated phagocytic cells generate hypochlorite (HOCl) via release of hydrogen peroxide and the enzyme myeloperoxidase. HOCl plays an important role in bacterial cell killing, but excessive or misplaced production of HOCI is also known to cause tissue damage. Studies have shown that low-molecula......Activated phagocytic cells generate hypochlorite (HOCl) via release of hydrogen peroxide and the enzyme myeloperoxidase. HOCl plays an important role in bacterial cell killing, but excessive or misplaced production of HOCI is also known to cause tissue damage. Studies have shown that low......-molecular-weight thiols such as reduced glutathione (GSH), and sulfur-containing amino acids in proteins, are major targets for HOCl. Radicals have not generally been implicated as intermediates in thiol oxidation by HOCl, though there is considerable literature evidence for the involvement of radicals in the metal ion......-, thermal- or UV light-catalysed decomposition of sulfenyl or sulfonyl chlorides which are postulated intermediates in thiol oxidation. In this study we show that thiyl radicals are generated on reaction of a number of low-molecular-weight thiols with HOCl. With sub-stoichiometric amounts of HOCl, relative...

  20. Nuclear thiol redox systems in plants.

    Science.gov (United States)

    Delorme-Hinoux, Valérie; Bangash, Sajid A K; Meyer, Andreas J; Reichheld, Jean-Philippe

    2016-02-01

    Thiol-disulfide redox regulation is essential for many cellular functions in plants. It has major roles in defense mechanisms, maintains the redox status of the cell and plays structural, with regulatory roles for many proteins. Although thiol-based redox regulation has been extensively studied in subcellular organelles such as chloroplasts, it has been much less studied in the nucleus. Thiol-disulfide redox regulation is dependent on the conserved redox proteins, glutathione/glutaredoxin (GRX) and thioredoxin (TRX) systems. We first focus on the functions of glutathione in the nucleus and discuss recent data concerning accumulation of glutathione in the nucleus. We also provide evidence that glutathione reduction is potentially active in the nucleus. Recent data suggests that the nucleus is enriched in specific GRX and TRX isoforms. We discuss the biochemical and molecular characteristics of these isoforms and focus on genetic evidences for their potential nuclear functions. Finally, we make an overview of the different thiol-based redox regulated proteins in the nucleus. These proteins are involved in various pathways including transcriptional regulation, metabolism and signaling. PMID:26795153

  1. Comparative Genomics of Thiol Oxidoreductases Reveals Widespread and Essential Functions of Thiol-based Redox Control of Cellular Processes

    OpenAIRE

    Fomenko, Dmitri E; GLADYSHEV, Vadim N.

    2012-01-01

    Aims: Redox regulation of cellular processes is an important mechanism that operates in organisms from bacteria to mammals. Much of the redox control is provided by thiol oxidoreductases: proteins that employ cysteine residues for redox catalysis. We wanted to identify thiol oxidoreductases on a genome-wide scale and use this information to obtain insights into the general principles of thiol-based redox control. Results: Thiol oxidoreductases were identified by three independent methods that...

  2. Functional and Structural Characterization of a Thiol Peroxidase from Mycobacterium tuberculosis

    Energy Technology Data Exchange (ETDEWEB)

    Rho,B.; Hung, L.; Holton, J.; Vigil, D.; Kim, S.; Park, M.; Terwilliger, T.; Pedelacq, j.

    2006-01-01

    A thiol peroxidase (Tpx) from Mycobacterium tuberculosis was functionally analyzed. The enzyme shows NADPH-linked peroxidase activity using a thioredoxin-thioredoxin reductase system as electron donor, and anti-oxidant activity in a thiol-dependent metal-catalyzed oxidation system. It reduces H{sub 2}O{sub 2}, t-butyl hydroperoxide, and cumene hydroperoxide, and is inhibited by sulfhydryl reagents. Mutational studies revealed that the peroxidatic (Cys60) and resolving (Cys93) cysteine residues are critical amino acids for catalytic activity. The X-ray structure determined to a resolution of 1.75 Angstroms shows a thioredoxin fold similar to that of other peroxiredoxin family members. Superposition with structural homologues in oxidized and reduced forms indicates that the M. tuberculosis Tpx is a member of the atypical two-Cys peroxiredoxin family. In addition, the short distance that separates the Ca atoms of Cys60 and Cys93 and the location of these cysteine residues in unstructured regions may indicate that the M. tuberculosis enzyme is oxidized, though the side-chain of Cys60 is poorly visible. It is solely in the reduced Streptococcus pneumoniae Tpx structure that both residues are part of two distinct helical segments. The M. tuberculosis Tpx is dimeric both in solution and in the crystal structure. Amino acid residues from both monomers delineate the active site pocket.

  3. Isolated menthone reductase and nucleic acid molecules encoding same

    Energy Technology Data Exchange (ETDEWEB)

    Croteau, Rodney B; Davis, Edward M; Ringer, Kerry L

    2013-04-23

    The present invention provides isolated menthone reductase proteins, isolated nucleic acid molecules encoding menthone reductase proteins, methods for expressing and isolating menthone reductase proteins, and transgenic plants expressing elevated levels of menthone reductase protein.

  4. Formate is the hydrogen donor for the anaerobic ribonucleotide reductase from Escherichia coli.

    Science.gov (United States)

    Mulliez, E; Ollagnier, S; Fontecave, M; Eliasson, R; Reichard, P

    1995-09-12

    During anaerobic growth Escherichia coli uses a specific ribonucleoside-triphosphate reductase (class III enzyme) for the production of deoxyribonucleoside triphosphates. In its active form, the enzyme contains an iron-sulfur center and an oxygen-sensitive glycyl radical (Gly-681). The radical is generated in the inactive protein from S-adenosylmethionine by an auxiliary enzyme system present in E. coli. By modification of the previous purification procedure, we now prepared a glycyl radical-containing reductase, active in the absence of the auxiliary reducing enzyme system. This reductase uses formate as hydrogen donor in the reaction. During catalysis, formate is stoichiometrically oxidized to CO2, and isotope from [3H]formate appears in water. Thus E. coli uses completely different hydrogen donors for the reduction of ribonucleotides during anaerobic and aerobic growth. The aerobic class I reductase employs redox-active thiols from thioredoxin or glutaredoxin to this purpose. The present results strengthen speculations that class III enzymes arose early during the evolution of DNA. PMID:7568012

  5. CATALYTIC ADVANTAGES PROVIDED BY SELENOCYSTEINE IN METHIONINE-S-SULFOXIDE REDUCTASES†

    Science.gov (United States)

    Kim, Hwa-Young; Fomenko, Dmitri E.; Yoon, Yeo-Eun; Gladyshev, Vadim N.

    2008-01-01

    Methionine sulfoxide reductases are key enzymes that repair oxidatively damaged proteins. Two distinct stereospecific enzyme families are responsible for this function: MsrA (methionine-S-sulfoxide reductase) and MsrB (methionine-R-sulfoxide reductase). In the present study, we identified multiple selenoprotein MsrA sequences in organisms from bacteria to animals. We characterized the selenocysteine (Sec)-containing Chlamydomonas MsrA and found that this protein exhibited 10–50-fold higher activity than either its cysteine (Cys) mutant form or the natural mouse Cys-containing MsrA, making this selenoenzyme the most efficient MsrA known. We also generated a selenoprotein form of mouse MsrA and found that the presence of Sec increased the activity of this enzyme when a resolving Cys was mutated in the protein. These data suggest that the presence of Sec improves the reduction of methionine sulfoxide by MsrAs. However, the oxidized selenoprotein could not always be efficiently reduced to regenerate the active enzyme. Overall, this study demonstrates that sporadically evolved Sec-containing forms of methionine sulfoxide reductases reflect catalytic advantages provided by Sec in these and likely other thiol-dependent oxidoreductases. PMID:17105189

  6. Regulation of yeast replicative life span by thiol oxidoreductases

    OpenAIRE

    Hacioglu, Elise; Esmer, Isil; Fomenko, Dmitri E; GLADYSHEV, Vadim N.; Koc, Ahmet

    2010-01-01

    Thiol-based redox reactions are involved in the regulation of a variety of biological functions, such as protection against oxidative stress, signal transduction and protein folding. Some proteins involved in redox regulation have been shown to modulate life span in organisms from yeast to mammals. To assess the role of thiol oxidoreductases in aging on a genome-wide scale, we analyzed the replicative life span of yeast cells lacking known and candidate thiol oxidoreductases. The data suggest...

  7. Thiols and antioxidants in radiobiology: chemical and bioanalytical problems

    International Nuclear Information System (INIS)

    Thiols may radioprotect by donating hydrogen atoms to a carbon-centred radical, but ascorbate (a better electron- than hydrogen-donor) can protect under some circumstances. The thiyl radical which may be produced is also reactive. Radioprotective efficiency may reflect both chemical reactivity and accessibility to DNA. Differences in uptake of thiols and thiol/disulphide exchange necessitate as much attention to chemical analysis of the test system as to its radiobiology. (author)

  8. Crystal-bound vs surface-bound thiols on nanocrystals.

    Science.gov (United States)

    Turo, Michael J; Macdonald, Janet E

    2014-10-28

    The use of thiol ligands as a sulfur source for nanocrystal synthesis has recently come en vogue, as the products are often high quality. A comparative study was performed of dodecanethiol-capped Cu2S prepared with elemental sulfur and thiol sulfur reagents. XPS and TGA-MS provide evidence for differing binding modes of the capping thiols. Under conditions where the thiol acts only as a ligand, the capping thiols are "surface-bound" and bond to surface cations in low coordination number sites. In contrast, when thiols are used as a sulfur source, "crystal-bound" thiols result that sit in high coordination sites and are the terminal S layer of the crystal. A (1)H NMR study shows suppressed surface reactivity and ligand exchange with crystal-bound thiols, which could limit further application of the particles. To address the challenge and opportunity of nonlabile ligands, dodecyl-3-mercaptopropanoate, a molecule possessing both a thiol and an ester, was used as the sulfur source for the synthesis of Cu2S and CuInS2. A postsynthetic base hydrolysis cleaves the ester, leaving a carboxylate corona around the nanocrystals and rendering the particles water-soluble. PMID:25219599

  9. Thiol groups of gizzard myosin heavy chains

    International Nuclear Information System (INIS)

    Proteolysis of phosphorylated and 3H-labeled dinitrophenylated chicken gizzard myosin with trypsin released major fragments of M/sub r/ 25,000, 50,000 and 66,000 in a 1:1 ratio. They contained 57% of the dinitrophenyl (N2ph) group bound to thiols of the heavy chains; 28% of the label was bound to the light chains. The fragments of M/sub r/ 25,000 and M/sub r/ 66,000 were dinitrophenylated predominantly when the K+-ATPase activity was inhibited. Thiolysis of phosphorylated and dinitrophenylated myosin with 2-mercaptoethanol removed 60% and 25% of the N2ph group from the N-terminal and M/sub r/ 66,000 fragments of the heavy chain, respectively, when 48% of the K+-ATPase activity was restored. Papain proteolysis of the tryptic digest of modified myosin released a C-terminal segment from the fragment of M/sub r/ 66,000 and it contained most of the remaining label. Proteolysis of 3H-labeled dinitrophenylated myosin alone resulted in the same digestion pattern but less of the label was bound to the heavy chain fragments. In this case, restoration of enzymic activity occurred in thiolyzed dinitrophenylated myosin when the N2ph group was removed from the light chains, predominantly. Conformational changes in gizzard myosin, mediated by phosphorylation, altered the reactivity of the thiols in specific fragments of the heavy chain. Thiol groups of the N- and C-terminal heavy chain regions are involved in maintaining the ATPase activity of myosin

  10. Atom precise platinum-thiol crowns.

    Science.gov (United States)

    George, Anu; Asha, K S; Reber, Arthur C; Biltek, Scott R; Pedicini, Anthony F; Sen, Ayusman; Khanna, Shiv N; Mandal, Sukhendu

    2015-12-14

    Ligand stabilized water soluble Pt nanoclusters were synthesized and characterized through electrospray ionization mass spectrometry. Glutathione was used as the ligand, and Pt5(SG)10, and Pt6(SG)12 clusters were synthesized. Theoretical investigations found that these clusters do not possess a metal core, but rather are most stable in a ring structure. The clusters are stabilized through the thiol ligands forming a square planar structure around each Pt atom to form a ring. The structural elucidation was confirmed through UV/Vis and IR spectroscopy. PMID:26486562

  11. 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)

  12. The second naphthol reductase of fungal melanin biosynthesis in Magnaporthe grisea: tetrahydroxynaphthalene reductase.

    Science.gov (United States)

    Thompson, J E; Fahnestock, S; Farrall, L; Liao, D I; Valent, B; Jordan, D B

    2000-11-10

    Mutants of Magnaporthe grisea harboring a defective gene for 1,3, 8-trihydroxynaphthalene reductase retain the capability to produce scytalone, thus suggesting the existence of a second naphthol reductase that can catalyze the reduction of 1,3,6, 8-tetrahydroxynaphthalene to scytalone within the fungal melanin biosynthetic pathway. The second naphthol reductase gene was cloned from M. grisea by identification of cDNA fragments with weak homology to the cDNA of trihydroxynaphthalene reductase. The amino acid sequence for the second naphthol reductase is 46% identical to that of trihydroxynaphthalene reductase. The second naphthol reductase was produced in Esherichia coli and purified to homogeneity. Substrate competition experiments indicate that the second reductase prefers tetrahydroxynaphthalene over trihydroxynaphthalene by a factor of 310; trihydroxynaphthalene reductase prefers trihydroxynaphthalene over tetrahydroxynaphthalene by a factor of 4.2. On the basis of the 1300-fold difference in substrate specificities between the two reductases, the second reductase is designated tetrahydroxynaphthalene reductase. Tetrahydroxynaphthalene reductase has a 200-fold larger K(i) for the fungicide tricyclazole than that of trihydroxynaphthalene reductase, and this accounts for the latter enzyme being the primary physiological target of the fungicide. M. grisea mutants lacking activities for both trihydroxynaphthalene and tetrahydroxynaphthalene reductases do not produce scytalone, indicating that there are no other metabolic routes to scytalone. PMID:10956664

  13. Cellular thiols: Importance in misonidazole metabolism

    International Nuclear Information System (INIS)

    Thiol depletion by buthionine S-R sulfoximine or diethyl mateate improves the effectiveness of Misonidazole as a hypoxic cell radiosensitizer and cytoxic agent. For some time the authors have been concerned with the metabolic activation of miso via the pentose cycle to cytoxic intermediates under hypoxic conditions. The pentose cycle is also important for maintaining cellular glutathione and subsequent inactivation of miso linked aerobic H/sub 2/O/sub 2/ production. Therefore it is of importance to know how thiol depletion affects metabolic activation of misonidazole and other sensitizers to potentially toxic intermediates under aerobic and hypoxic conditions. The authors have shown that nitro reduction can be monitored by measuring the stimulation of the pentose shunt, since NADPH which is formed in the shunt is a requirement for reduction of nitro compounds by tumor cells. Using A549 human lung carcinoma cells we have found that treatment with BSO under conditions that remove virtually 100% of the NPSH does not significantly affect the ability of miso to stimulate the pentose shunt. In addition, there is no effect of BSO on the response of the shunt to nitrofurazone, nor on the rate of hypoxic reduction of nitro-furazone. However, BSO does inhibit enzymes associated with inactivation of H/sub 2/O/sub 2/ produced via miso metabolism

  14. Inheritance of nitrite reductase and regulation of nitrate reductase, nitrite reductase, and glutamine synthetase isozymes.

    Science.gov (United States)

    Heath-Pagliuso, S; Huffaker, R C; Allard, R W

    1984-10-01

    Banding patterns of nitrate reductase (NR), nitrite reductase (NiR), and glutamine synthetase (GS) from leaves of diploid barley (Hordeum vulgare), tetraploid wheat (Triticum durum), hexaploid wheat (Triticum aestivum), and tetraploid wild oats (Avena barbata) were compared following starch gel electrophoresis. Two NR isozymes, which appeared to be under different regulatory control, were observed in each of the three species. The activity of the more slowly migrating nitrate reductase isozyme (NR1) was induced by NO3- in green seedlings and cycloheximide inhibited induction. However, the activity of the faster NR isozyme (NR2) was unaffected by addition of KNO3, and it was not affected by treatments of cycloheximide or chloramphenicol. Only a single isozyme of nitrite reductase was detected in surveys of three tetraploid and 18 hexaploid wheat, and 48 barley accessions; however, three isozymes associated with different ecotypes were detected in the wild oats. Inheritance patterns showed that two of the wild oat isozymes were governed by a single Mendelian locus with two codominant alleles; however, no variation was detected for the third isozyme. Treatment of excised barely and wild oat seedlings with cycloheximide and chloramphenicol showed that induction of NiR activity was greatly inhibited by cycloheximide, but only slightly by chloramphenicol. Only a single GS isozyme was detected in extracts of green leaves of wheat, barley, and wild oat seedlings. No electrophoretic variation was observed within or among any of these three species. Thus, this enzyme appears to be the most structurally conserved of the three enzymes. PMID:11541965

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

    Science.gov (United States)

    Wang, Jinling; de Montellano, Paul R Ortiz

    2003-05-30

    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

  16. Purification and kinetic analysis of cytosolic and mitochondrial thioredoxin glutathione reductase extracted from Taenia solium cysticerci.

    Science.gov (United States)

    Plancarte, Agustin; Nava, Gabriela

    2015-02-01

    Thioredoxin glutathione reductases (TGRs) (EC 1.8.1.9) were purified to homogeneity from the cytosolic (cTsTGR) and mitochondrial (mTsTGR) fractions of Taenia solium, the agent responsible for neurocysticercosis, one of the major central nervous system parasitic diseases in humans. TsTGRs had a relative molecular weight of 132,000, while the corresponding value per subunit obtained under denaturing conditions, was of 62,000. Specific activities for thioredoxin reductase and glutathione reductase substrates for both TGRs explored were in the range or lower than values obtained for other platyhelminths and mammalian TGRs. cTsTGR and mTsTGR also showed hydroperoxide reductase activity using hydroperoxide as substrate. Km(DTNB) and Kcat(DTNB) values for cTsTGR and mTsTGR (88?µM and 1.9?s(-1); 45?µM and 12.6?s(-1), respectively) and Km(GSSG) and Kcat(GSSG) values for cTsTGR and mTsTGR (6.3?µM and 0.96?s(-1); 4?µM and 1.62?s(-1), respectively) were similar to or lower than those reported for mammalian TGRs. Mass spectrometry analysis showed that 12 peptides from cTsTGR and seven from mTsTGR were a match for gi|29825896 thioredoxin glutathione reductase [Echinococcus granulosus], confirming that both enzymes are TGRs. Both T. solium TGRs were inhibited by the gold compound auranofin, a selective inhibitor of thiol-dependent flavoreductases (I???=?3.25, 2.29?nM for DTNB and GSSG substrates, respectively for cTsTGR; I???=?5.6, 25.4?nM for mTsTGR toward the same substrates in the described order). Glutathione reductase activity of cTsTGR and mTsTGR exhibited hysteretic behavior with moderate to high concentrations of GSSG; this result was not observed either with thioredoxin, DTNB or NADPH. However, the observed hysteretic kinetics was suppressed with increasing amounts of both parasitic TGRs. These data suggest the existence of an effective substitute which may account for the lack of the detoxification enzymes glutathione reductase and thioredoxin reductase in T. solium, as has been described for very few other platyhelminths. PMID:25541385

  17. Fatty acyl-CoA reductase

    Energy Technology Data Exchange (ETDEWEB)

    Reiser, Steven E.; Somerville, Chris R.

    1998-12-01

    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.

  18. On radiation protection of cells in vitro with thiols

    International Nuclear Information System (INIS)

    Data on the mechanism of in vitro cells protection with thiols have been analyzed. It is shown that hypoxia, caused by thiol autooxidation (the maximum FDI is approximately 3), makes the main contribution to cell protection from reproductive mortality in the previosly conducted experiments. Oxygen-independent component of protective effect of certain thiols (the maximum FDI is approXimately 1.5) is conditioned by metabolic changes in cell caused by them, which results in the increase enzyme repair volume of potential injuries

  19. The roles of thiol oxidoreductases in yeast replicative aging.

    Science.gov (United States)

    Hacioglu, Elise; Esmer, Isil; Fomenko, Dmitri E; Gladyshev, Vadim N; Koc, Ahmet

    2010-01-01

    Thiol-based redox reactions are involved in the regulation of a variety of biological functions, such as protection against oxidative stress, signal transduction and protein folding. Some proteins involved in redox regulation have been shown to modulate life span in organisms from yeast to mammals. To assess the role of thiol oxidoreductases in aging on a genome-wide scale, we analyzed the replicative life span of yeast cells lacking known and candidate thiol oxidoreductases. The data suggest the role of several pathways in controlling yeast replicative life span, including thioredoxin reduction, protein folding and degradation, peroxide reduction, PIP3 signaling, and ATP synthesis. PMID:20934449

  20. Regulation of yeast replicative life span by thiol oxidoreductases

    Science.gov (United States)

    Hacioglu, Elise; Esmer, Isil; Fomenko, Dmitri E.; Gladyshev, Vadim N.; Koc, Ahmet

    2011-01-01

    Thiol-based redox reactions are involved in the regulation of a variety of biological functions, such as protection against oxidative stress, signal transduction and protein folding. Some proteins involved in redox regulation have been shown to modulate life span in organisms from yeast to mammals. To assess the role of thiol oxidoreductases in aging on a genome-wide scale, we analyzed the replicative life span of yeast cells lacking known and candidate thiol oxidoreductases. The data suggest the role of several pathways in regulation of yeast aging, including thioredoxin reduction, protein folding and degradation, peroxide reduction, PIP3 signaling, and ATP synthesis. PMID:20934449

  1. Surface functionalized thiol-ene waveguides for ?uorescence biosensing in micro?uidic devices

    DEFF Research Database (Denmark)

    Feidenhans'l, Nikolaj Agentoft; Lafleur, Josiane P.; Jensen, Thomas Glasdam; Kutter, Jörg Peter

    -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...

  2. A maize gene encoding an NADPH binding enzyme highly homologous to isoflavone reductases is activated in response to sulfur starvation.

    Science.gov (United States)

    Petrucco, S; Bolchi, A; Foroni, C; Percudani, R; Rossi, G L; Ottonello, S

    1996-01-01

    we isolated a novel gene that is selectively induced both in roots and shoots in response to sulfur starvation. This gene encodes a cytosolic, monomeric protein of 33 kD that selectively binds NADPH. The predicted polypeptide is highly homologous ( > 70%) to leguminous isoflavone reductases (IFRs), but the maize protein (IRL for isoflavone reductase-like) belongs to a novel family of proteins present in a variety of plants. Anti-IRL antibodies specifically recognize IFR polypeptides, yet the maize protein is unable to use various isoflavonoids as substrates. IRL expression is correlated closely to glutathione availability: it is persistently induced in seedlings whose glutathione content is about fourfold lower than controls, and it is down-regulated rapidly when control levels of glutathione are restored. This glutathione-dependent regulation indicates that maize IRL may play a crucial role in the establishment of a thiol-independent response to oxidative stress under glutathione shortage conditions. PMID:8597660

  3. 21 CFR 864.7375 - Glutathione reductase assay.

    Science.gov (United States)

    2010-04-01

    ...2010-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food...Packages § 864.7375 Glutathione reductase assay. (a) Identification. A glutathione reductase assay is a device used to determine the...

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

    Directory of Open Access Journals (Sweden)

    Stantchev Tzanko S

    2012-12-01

    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.

  5. Facially amphiphilic thiol capped gold and silver nanoparticles

    Indian Academy of Sciences (India)

    Shreedhar Bhata; Uday Maitra

    2008-11-01

    A series of bile acid-derived facially amphiphilic thiols have been used to cap sliver and gold nanoparticles. The self-assembling properties of these steroid-capped nanoparticles have been investigated and reported in this article.

  6. Quantifying the global cellular thiol-disulfide status

    DEFF Research Database (Denmark)

    Hansen, Rosa E; Roth, Doris; Winther, Jakob R

    2009-01-01

    It is widely accepted that the redox status of protein thiols is of central importance to protein structure and folding and that glutathione is an important low-molecular-mass redox regulator. However, the total cellular pools of thiols and disulfides and their relative abundance have never been...... determined. In this study, we have assembled a global picture of the cellular thiol-disulfide status in cultured mammalian cells. We have quantified the absolute levels of protein thiols, protein disulfides, and glutathionylated protein (PSSG) in all cellular protein, including membrane proteins. These data...... were combined with quantification of reduced and oxidized glutathione in the same cells. Of the total protein cysteines, 6% and 9.6% are engaged in disulfide bond formation in HEK and HeLa cells, respectively. Furthermore, the steady-state level of PSSG is <0.1% of the total protein cysteines in both...

  7. Halogen mediated voltammetric oxidation of biological thiols and disulfides.

    Science.gov (United States)

    Valero-Ruiz, Edelmira; González-Sánchez, María I; Batchelor-McAuley, Christopher; Compton, Richard G

    2016-01-01

    The electrochemical generation of the halides, bromine and iodine, in the presence of biologically relevant organosulfur is demonstrated to result in an analytically useful response. In the case of the iodide/iodine redox couple only the thiol causes an increase in the electrochemical oxidative peak current. Conversely, the formed bromine may catalytically oxidise both thiols and disulfides. Hence, the differing reactivities of the halide ions readily allow discrimination between the closely related thiol and disulphide species. For all of the organosulfur species investigated (glutathione, cysteine and homocysteine) micromolar limits of detection are attainable. In the case of the bromine mediated oxidation this sensitivity at least partially arises from the large catalytic amplification, such that, for each disulphide molecule up to ten electrons may be transferred. Ultimately this bromine oxidation results in the formation of the sulfonate species. For the iodine mediated oxidation of the thiols the oxidation proceeds no further than to the formation of the associated disulfide. PMID:26539570

  8. Reversible inactivation of CO dehydrogenase with thiol compounds

    Energy Technology Data Exchange (ETDEWEB)

    Kreß, Oliver [Department of Microbiology, University of Bayreuth, 95440 Bayreuth (Germany); Gnida, Manuel [Department of Chemistry, University of Paderborn, 33098 Paderborn (Germany); Pelzmann, Astrid M. [Department of Microbiology, University of Bayreuth, 95440 Bayreuth (Germany); Marx, Christian [Institute of Biochemistry and Biophysics, Friedrich-Schiller-University of Jena, 07745 Jena (Germany); Meyer-Klaucke, Wolfram [Department of Chemistry, University of Paderborn, 33098 Paderborn (Germany); Meyer, Ortwin, E-mail: Ortwin.Meyer@uni-bayreuth.de [Department of Microbiology, University of Bayreuth, 95440 Bayreuth (Germany)

    2014-05-09

    Highlights: • Rather large thiols (e.g. coenzyme A) can reach the active site of CO dehydrogenase. • CO- and H{sub 2}-oxidizing activity of CO dehydrogenase is inhibited by thiols. • Inhibition by thiols was reversed by CO or upon lowering the thiol concentration. • Thiols coordinate the Cu ion in the [CuSMo(=O)OH] active site as a third ligand. - Abstract: 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 + H{sub 2}O ? CO{sub 2} + 2e{sup ?} + 2H{sup +}) 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 K{sub i}-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{sup VI}(=O)OH{sub (2)}SCu{sup 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.

  9. Induction Curing of Thiol-acrylate and Thiolene Composite Systems

    OpenAIRE

    Ye, Sheng; Cramer, Neil B.; Stevens, Blake E.; Sani, Robert L.; Bowman, Christopher N

    2011-01-01

    Induction curing is demonstrated as a novel type of in situ radiation curing that maintains most of the advantages of photocuring while eliminating the restriction of light accessibility. Induction curing is utilized to polymerize opaque composites comprised of thiol-acrylate and thiol-ene resins, nanoscale magnetic particles, and carbon nanotubes. Nanoscale magnetic particles are dispersed in the resin and upon exposure to the magnetic field, these particles lead to induction heating that ra...

  10. Mussel protein adhesion depends on thiol-mediated redox modulation

    OpenAIRE

    Yu, Jing; Wei, Wei; Danner, Eric; Ashley, Rebekah K.; Israelachvili, Jacob N.; Waite, J. Herbert

    2011-01-01

    Mussel adhesion is mediated by foot proteins (mfp) rich in a catecholic amino acid, 3, 4-dihydroxyphenylalanine (dopa), capable of forming strong bidentate interactions with a variety of surfaces. A facile tendency toward auto-oxidation, however, often renders dopa unreliable for adhesion. Mussels limit dopa oxidation during adhesive plaque formation by imposing an acidic, reducing regime based on thiol-rich mfp-6, which restores dopa by coupling the oxidation of thiols to dopaquinone reduction.

  11. Synthetic Applications of Intramolecular Thiol-Ene “Click” Reactions

    Directory of Open Access Journals (Sweden)

    Eoin M. Scanlan

    2014-11-01

    Full Text Available The intermolecular thiol-ene reaction is emerging as a highly efficient; free-radical mediated “click” process with diverse applications in biofunctionalisation and materials science. The related intramolecular thiol-ene reactions offer significant potential for the preparation of a wide range of sulphur containing heterocycles including synthetic therapeutics such as cyclic peptides and thiosugars. Herein, we review recent advances in intramolecular thiyl-radical mediated reactions and their applications for synthetic and medicinal chemistry.

  12. Protein Thiols as an Indication of Oxidative Stress

    Directory of Open Access Journals (Sweden)

    Yousef Rezaei Chianeh

    2014-06-01

    Full Text Available Thiol is an organic compound that contain sulphhydryl group that have a critical role in preventing any involvement of oxidative stress in the cell. These defensive functions are generally considered to be carried out by the low molecular weight thiol glutathione and by cysteine residues in the active sites of proteins such as thioredoxin and peroxiredoxin. In addition, there are thiols exposed on protein surfaces that are not directly involved with protein function, although they can interact with the intracellular environment.The process of protection of the cell against an oxidative damage occur by thiol and cystein residue that has a low molecular weight. These residue are present in the active sites of a protein like, peroxiredoxin and thioredoxin. Apart from intracellular antioxidant defense mechanism by protein thiol, there are presence of thiol in outer surface of protein that are not involved with the function of protein, even though they can interact with intracellular part of the cell. [Archives Medical Review Journal 2014; 23(3.000: 443-456

  13. The Expanding Landscape of the Thiol Redox Proteome.

    Science.gov (United States)

    Yang, Jing; Carroll, Kate S; Liebler, Daniel C

    2016-01-01

    Cysteine occupies a unique place in protein chemistry. The nucleophilic thiol group allows cysteine to undergo a broad range of redox modifications beyond classical thiol-disulfide redox equilibria, including S-sulfenylation (-SOH), S-sulfinylation (-SO2H), S-sulfonylation (-SO3H), S-nitrosylation (-SNO), S-sulfhydration (-SSH), S-glutathionylation (-SSG), and others. Emerging evidence suggests that these post-translational modifications (PTM) are important in cellular redox regulation and protection against oxidative damage. Identification of protein targets of thiol redox modifications is crucial to understanding their roles in biology and disease. However, analysis of these highly labile and dynamic modifications poses challenges. Recent advances in the design of probes for thiol redox forms, together with innovative mass spectrometry based chemoproteomics methods make it possible to perform global, site-specific, and quantitative analyses of thiol redox modifications in complex proteomes. Here, we review chemical proteomic strategies used to expand the landscape of thiol redox modifications. PMID:26518762

  14. Polymer surface engineering via thiol-mediated reactions

    Science.gov (United States)

    Hensarling, Ryan Matthew

    Synthesis of polymer brushes to decorate a surface with desired functionality typically involves surface-initiated polymerization (SIP) of functional, but non-reactive monomers. This approach suffers major drawbacks associated with synthesizing sufficiently thick polymer brushes containing surface-attached polymer chains of high molecular weight at high grafting density (i.e. cost, synthetic effort and functional group intolerance during polymerization). The research herein seeks to circumvent these limitations by the decoration of surfaces with polymer chains bearing specific pendent functional groups amenable to post-polymerization modification (PPM). In particular, this dissertation leverages PPM via a specific class of click reactions - thiol-click - that 1) enables the rapid generation of a diverse library of functional surfaces from a single substrates precursor, 2) utilizes a structurally diverse range of commercially available or easily attainable reagents, 3) proceeds rapidly to quantitative conversions under mild conditions and 4) opens the door to orthogonal and site-selective functionalization. In the first two studies, radical-mediated thiol-yne and base-catalyzed thiol-isocyanate reactions are demonstrated as modular platforms for the rapid and practical fabrication of highly functional, multicomponent surfaces under ambient conditions. Brush surfaces expressing a three-dimensional configuration of alkyne or isocyanate functionalities were modified with high efficiency and short reaction times using a library of commercially available thiols. In the third study, two routes to multifunctional brush surfaces were demonstrated utilizing orthogonal thiol-click reactions. In the first approach, alkyne-functionalized homopolymer brushes were modified with multiple thiols via a statistical, radical-mediated thiol-yne co-click reaction; and in the second approach, statistical copolymer brushes carrying two distinctly-addressable reactive moieties were sequentially modified via orthogonal base-catalyzed thiol-X (where X represents an isocyanate, epoxy, or ?-bromoester) and radical-mediated thiol-yne reactions. In the fourth study thiol-click PPMs are investigated in depth to determine how surface constraints affect the modification process by probing the penetration depth of functional thiol modifiers into pendent isocyanate-containing polymer brushes via neutron reflectivity studies. Also, the synthesis of tapered block copolymer brush surfaces was demonstrated by exploiting the inherent mass transport limitations of post-polymerization modification processes on reactive brush surfaces. In the fifth study a post-polymerization surface modification approach providing pendent thiol functionality along the polymer brush backbone using the photolabile protection chemistry of both o-nitrobenzyl and p-methoxyphenacyl thioethers was developed. Addressing the protecting groups with light not only affords spatial control of reactive thiol functionality but enables a plethora of thiol-mediated transformations with isocyanates and maleimides providing a modular route to create functional polymer surfaces.

  15. Binding to large enzyme pockets: small-molecule inhibitors of trypanothione reductase.

    Science.gov (United States)

    Persch, Elke; Bryson, Steve; Todoroff, Nickolay K; Eberle, Christian; Thelemann, Jonas; Dirdjaja, Natalie; Kaiser, Marcel; Weber, Maria; Derbani, Hassan; Brun, Reto; Schneider, Gisbert; Pai, Emil F; Krauth-Siegel, R Luise; Diederich, François

    2014-08-01

    The causative agents of the parasitic disease human African trypanosomiasis belong to the family of trypanosomatids. These parasitic protozoa exhibit a unique thiol redox metabolism that is based on the flavoenzyme trypanothione reductase (TR). TR was identified as a potential drug target and features a large active site that allows a multitude of possible ligand orientations, which renders rational structure-based inhibitor design highly challenging. Herein we describe the synthesis, binding properties, and kinetic analysis of a new series of small-molecule inhibitors of TR. The conjunction of biological activities, mutation studies, and virtual ligand docking simulations led to the prediction of a binding mode that was confirmed by crystal structure analysis. The crystal structures revealed that the ligands bind to the hydrophobic wall of the so-called "mepacrine binding site". The binding conformation and potency of the inhibitors varied for TR from Trypanosoma brucei and T. cruzi. PMID:24788386

  16. 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.)

  17. Identification, Characterization, and Classification of Genes Encoding Perchlorate Reductase

    OpenAIRE

    Bender, Kelly S.; Shang, Ching; Chakraborty, Romy; Belchik, Sara M.; Coates, John D.; Achenbach, Laurie A.

    2005-01-01

    The reduction of perchlorate to chlorite, the first enzymatic step in the bacterial reduction of perchlorate, is catalyzed by perchlorate reductase. The genes encoding perchlorate reductase (pcrABCD) in two Dechloromonas species were characterized. Sequence analysis of the pcrAB gene products revealed similarity to ?- and ?-subunits of microbial nitrate reductase, selenate reductase, dimethyl sulfide dehydrogenase, ethylbenzene dehydrogenase, and chlorate reductase, all of which are type II m...

  18. Identification of thiols by means of mercurated fluorescein.

    Science.gov (United States)

    Wroński, M

    1968-02-01

    A method is proposed for the identification of thiols by examination of their complexes with tetra-acetoxymercurifluorescein (TMF). It is based on the determination of the fluorescence intensity as a function of pH and exciting wavelength, and of absorbance as a function of pH at 465 and 510 mmu. The relative fluorescence of the complexes does not depend on the wavelength of the exciting light in the range 460-500 mmu. The presence of a carboxyl group in the thiol molecule results in a strong increase of fluorescence with increasing pH and an exciting wavelength > 500 mmu. PMID:18960286

  19. 5?-Reductase Isozymes in the Prostate

    OpenAIRE

    ZHU, YUAN-SHAN; Sun, Guang-Huan

    2005-01-01

    5?-reductases convert testosterone to dihydrotestosterone (DHT). There are two 5?-reductase isozymes, type 1 and type 2 in humans and animals. Mutations in type 2 isozyme with decreased enzymatic activity cause male pseudohermaphroditism. The affected 46XY individuals have high normal or elevated plasma testosterone levels with low normal or decreased DHT levels, resulting in an elevated testosterone/DHT ratios. They are born with ambiguous external genitalia and normal Wolffian differentiati...

  20. 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)

    A. Cansız

    2005-02-01

    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.

  1. New drug target in protozoan parasites: the role of thioredoxin reductase

    Science.gov (United States)

    Andrade, Rosa M.; Reed, Sharon L.

    2015-01-01

    Amebiasis causes approximately 70,000 deaths annually and is the third cause of death due to parasites worldwide. It is treated primarily with metronidazole, which has adverse side effects, is mutagenic and carcinogenic, and emergence of resistance is an increasing concern. Unfortunately, better therapeutic alternatives are lacking. Re-purposing of older FDA approved drugs is advantageous to drug discovery since safety and pharmacokinetic effects in humans are already known. In high throughput screening studies, we recently demonstrated that auranofin, a gold containing compound originally approved to treat rheumatoid arthritis, has activity against trophozoites of E. histolytica, the causative agent of amebiasis. Auranofin's anti-parasitic activity is attributed to its monovalent gold molecule that readily inhibits E. histolytica thioredoxin reductase. This anti-oxidant enzyme is the only thiol-dependent flavo-reductase present in E. histolytica. Auranofin has also shown promising activity against other protozoans of significant public health importance. Altogether, this evidence suggests that auranofin has the potential to become a broad spectrum alternative therapeutic agent for diseases with a large global burden. PMID:26483758

  2. 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

  3. Neutron-gamma irradiation and protein thiols: development of a protein thiol evaluation micro-method and application to irradiated baboons

    International Nuclear Information System (INIS)

    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)

  4. Thiol-mediated redox regulation of apoptosis. Possible roles of cellular thiols other than glutathione in T cell apoptosis.

    Science.gov (United States)

    Sato, N; Iwata, S; Nakamura, K; Hori, T; Mori, K; Yodoi, J

    1995-04-01

    Thiol redox status modulates various aspects of cellular function. We demonstrate that oxidation of cellular sulfhydryl (SH) groups induces apoptosis. In Jurkat T cells and human PBL blasts, the fraction of apoptotic nuclei increased after treatment with an SH-specific oxidant, diamide. Analysis of DNA fragmentation and nuclear morphology also indicated that SH oxidation could induce apoptosis. In the apoptosis induced by SH oxidation, the decrease of cellular glutathione was transient and the increase of glutathione disulfide was observed only after apoptotic changes had occurred. Depletion of cellular glutathione with buthionine sulfoximine failed to induce apoptosis, despite a marked decrease of cellular glutathione, which was greater than that observed in apoptosis induced by diamide. Thus, the changes of cellular glutathione or glutathione disulfide may not be the major cause of apoptosis induced by diamide. Intracellular adult T cell leukemia-derived factor/human thioredoxin, another thiol-related antioxidant protein, was oxidized by incubation with diamide. These results suggest that thiol redox status is one of the key factors of the apoptotic pathway in which thiols other than glutathione may play even more critical roles. PMID:7897207

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

    OpenAIRE

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

    1993-01-01

    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...

  6. 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.

  7. Respiratory arsenate reductase as a bidirectional enzyme

    Science.gov (United States)

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

    2009-01-01

    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.

  8. Domain Motion in Cytochrome P450 Reductase

    OpenAIRE

    Ellis, Jacqueline; Gutierrez, Aldo; Barsukov, Igor L.; Huang, Wei-Cheng; Grossmann, J. Günter; Roberts, Gordon C. K.

    2009-01-01

    NADPH-cytochrome P450 reductase (CPR), a diflavin reductase, plays a key role in the mammalian P450 mono-oxygenase system. In its crystal structure, the two flavins are close together, positioned for interflavin electron transfer but not for electron transfer to cytochrome P450. A number of lines of evidence suggest that domain motion is important in the action of the enzyme. We report NMR and small-angle x-ray scattering experiments addressing directly the question of domain organization in ...

  9. Control of dihydrofolate reductase messenger ribonucleic acid production.

    OpenAIRE

    Leys, E J; Kellems, R E

    1981-01-01

    We used methotrexate-resistant mouse cells in which dihydrofolate reductase levels are approximately 500 times normal to study the effect of growth stimulation on dihydrofolate reductase gene expression. As a result of growth stimulation, the relative rate of dihydrofolate reductase protein synthesis increased threefold, reaching a maximum between 25 and 30 h after stimulation. The relative rate of dihydrofolate reductase messenger ribonucleic acid production (i.e., the appearance of dihydrof...

  10. 21 CFR 864.7375 - Glutathione reductase assay.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Glutathione reductase assay. 864.7375 Section 864... reductase assay. (a) Identification. A glutathione reductase assay is a device used to determine the... fluorescence and photometry. The results of this assay are used in the diagnosis of liver disease,...

  11. Water electrolyte promoted oxidation of functional thiol groups.

    Science.gov (United States)

    Lauwers, K; Breynaert, E; Rombouts, I; Delcour, J A; Kirschhock, C E A

    2016-04-15

    The formation of disulfide bonds is of the utmost importance for a wide range of food products with gluten or globular proteins as functional agents. Here, the impact of mineral electrolyte composition of aqueous solutions on thiol oxidation kinetics was studied, using glutathione (GSH) and cysteine (CYS) as model systems. Interestingly, the oxidation rate of both compounds into their corresponding disulfides was significantly higher in common tap water than in ultrapure water. The systematic study of different electrolyte components showed that especially CaCl2 improved the oxidation rate of GSH. However, this effect was not observed for CYS, which indicated a strong impact of the local chemical environment on thiol oxidation kinetics. PMID:26675862

  12. Radical Scavenging Efficacy of Thiol Capped Silver Nanoparticles

    Indian Academy of Sciences (India)

    Kumudini Chandraker; Sandeep Kumar Vaishanav; Rekha Nagwanshi; Manmohan L Satnami

    2015-12-01

    Radical scavenging efficacy of L-cysteine (L-Cys), glutathione (GSH) and thioctic acid (TA) in the presence of silver nanoparticles (AgNPs) were determined by 1,1-diphenyl 2-picryl hydrazil (DPPH), nitric oxide (NO) and hydroxyl (OH) radicals as spectrophotometric assay. The hydrogen peroxide (H2O2) scavenging efficacy has been determined by titration method. Ascorbic acid has been used as standard for all radical scavenging efficacies. In general, antioxidant activity decreases in the presence of AgNPs. The covalent interactions of thiols (-SH) were found to be a key factor for the decreases in scavenging activity. The effect of thiol concentrations has been discussed. The size and shape of the nanoparticles and AgNP-SR interactions have been characterized through Transmission Electron Microscopy (TEM) and Fourier Transform Infrared (FTIR) spectroscopy, respectively.

  13. Structural formation of thiophene-2-thiol on gold

    Energy Technology Data Exchange (ETDEWEB)

    El-Kareh, Lydia; Beimborn, Axel; Mehring, Patrick; Handschak, Dominique [Experimentelle Physik 1 - TU Dortmund (Germany); Westphal, Carsten [Experimentelle Physik 1 - TU Dortmund (Germany); DELTA -TU Dortmund (Germany)

    2011-07-01

    In recent years self assembled monolayers (SAMs) have been extensively studied because of their well-defined structures resulting from simple dipping preparation. An ideal system for the understanding of self-organisation processes are alcanethiols that were widely examined during the last decades. These molecules can be prepared with different head groups leading to different applications in molecular electronics, nanotechnology, bio-sensing, and corrosion inhibition. One possible head group is thiophene. The orientation of thiophene-2-thiol adsorbed on Au(111) has been investigated by scanning tunneling microscopy (STM). Thiophene-2-thiol molecules are found forming highly ordered adlayers. High-resolution STM reveals well ordered molecular stripes of different length. On the gold surface the stripes arrange displaced with respect to the substrate lattice forming a two-dimensional molecular network.

  14. Interaction of azobenzene thiol molecules with gold nanoparticles.

    Czech Academy of Sciences Publication Activity Database

    Dammer, Ond?ej; Pfleger, Ji?í; Vl?ková, B.; Procházka, M.; Špringer, T.; Sedláková, Zde?ka

    Brno : Czech Society for New Materials and Technologies, 2006. s. 69. ISBN 80-214-3308-6. [International Conference on Nanosciences and Nanotechnologies in the Czech Republic /5./. 13.11.2006-15.11.2006, Brno] R&D Projects: GA AV ?R IAA4050406; GA ?R GD203/05/H001 Institutional research plan: CEZ:AV0Z40500505 Keywords : gold nanoparticles * SERS signal blinking * azobenzene thiol Subject RIV: CD - Macromolecular Chemistry

  15. Alkynylation of Thiols with Ethynylbenziodoxolone (EBX) Reagents: ?- or ?- ?-Addition?

    Science.gov (United States)

    Wodrich, Matthew D; Caramenti, Paola; Waser, Jerome

    2016-01-01

    The alkynylation of thiols with EthynylBenziodoXolone (EBX) reagents is a fast and chemoselective method for the synthesis of thioalkynes. Combined experimental and computational studies are reported, which led to the identification of a new mechanism for this reaction, proceeding via an initial sulfur-iodine interaction followed by ?-addition, ?-elimination, and a 1,2-shift. Depending on the substituent on the alkyne, this mechanism can be favored over the previously disclosed concerted ?-addition pathway. PMID:26652212

  16. Role of thiol pathways in TF procoagulant regulation

    OpenAIRE

    Ruf, Wolfram

    2012-01-01

    The generation of procoagulant Tissue Factor (TF) is crucial for thrombosis. TF contains a surface exposed allosteric disulfide bond that stabilizes the carboxyl-terminal domain involved in ligand interactions with coagulation factors VIIa and X. TF procoagulant activation typically occurs following cellular perturbations that also cause the appearance of procoagulant phosphatidylserine in the outer leaflet of cell membranes. However, thiol modifying agents, without suppressing phosphatidylse...

  17. Odorant polyfunctional thiols issued from bottle beer fermentation

    OpenAIRE

    Nizet, Sabrina; Gros, Jacques; Collin, Sonia; XII Weurman flavour research symposium

    2011-01-01

    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...

  18. Chiral liquid crystalline thiols for preparation of polybutadiene diols.

    Czech Academy of Sciences Publication Activity Database

    Bubnov, Alexej; Kašpar, Miroslav; Sedláková, Zde?ka; Ilavský, Michal

    2008-01-01

    Ro?. 35, ?. 5 (2008), s. 653-660. ISSN 0267-8292 R&D Projects: GA ?R GA202/05/0431; GA MŠk OC 175; GA AV ?R IAA4112401; GA AV ?R IAA100100710 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40500505 Keywords : monomers * liquid crystal * polybutadienes * chiral thiol Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.132, year: 2008

  19. New chiral thiols and related side chain liquid crystalline polymers.

    Czech Academy of Sciences Publication Activity Database

    Bubnov, Alexej; Kašpar, Miroslav; Sedláková, Zde?ka; Ilavský, Michal

    2007-01-01

    Ro?. 465, - (2007), s. 93-107. ISSN 1542-1406 R&D Projects: GA AV ?R IAA4112401; GA ?R GA202/05/0431 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40500505 Keywords : chiral thiols * differential scanning calorimetry * diols * liquid crystals * polarizing optical microscopy * polybutadien Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.554, year: 2007

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

    Science.gov (United States)

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

    1993-01-01

    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. PMID:8298460

  1. Tailored thiol-functional polyamides: synthesis and functionalization.

    Science.gov (United States)

    Mommer, Stefan; Keul, Helmut; Möller, Martin

    2014-12-01

    In this article, a synthetic concept for the preparation of polyamides with functional side groups is described. First, the synthesis of a bis(thiolactone) monomer is shown in a concise three-step route from itaconic acid and DL-homocysteine thiolactone. The reactivity of the resulting bis(thiolactone) toward hexyl amine is examined. Next, the bis(thiolactone) is reacted as A,A-type monomer with different B,B-type comonomers (1,12-diaminododecane and 1,3-bis(aminopropyl)tetramethyldisiloxane). Ring opening of the thiolactones by the diamines leads to polyamides with pendant thiol groups. Using two diamines in different ratios, the properties of the resulting polyamides are tuned (thermal properties are determined) and different molecular weights are acquired. Subsequently, the thiol groups are reacted with methyl acrylate via Michael addition to functionalize the polyamides. Functionalization of thiol-functional polyamides using poly(ethylene glycol) monomethyl ether (mPEG) acrylates (Mn = 480 and 1700 g mol(-1) ) results in water-soluble amphiphilic poly-amides with molecular weights higher than 10,000 g mol(-1) . PMID:25257791

  2. Differential stress induced by thiol adsorption on facetted nanocrystals.

    Science.gov (United States)

    Watari, Moyu; McKendry, Rachel A; Vögtli, Manuel; Aeppli, Gabriel; Soh, Yeong-Ah; Shi, Xiaowen; Xiong, Gang; Huang, Xiaojing; Harder, Ross; Robinson, Ian K

    2011-11-01

    Polycrystalline gold films coated with thiol-based self-assembled monolayers (SAM) form the basis of a wide range of nanomechanical sensor platforms. The detection of adsorbates with such devices relies on the transmission of mechanical forces, which is mediated by chemically derived stress at the organic-inorganic interface. Here, we show that the structure of a single 300-nm-diameter facetted gold nanocrystal, measured with coherent X-ray diffraction, changes profoundly after the adsorption of one of the simplest SAM-forming organic molecules. On self-assembly of propane thiol, the crystal's flat facets contract radially inwards relative to its spherical regions. Finite-element modelling indicates that this geometry change requires large stresses that are comparable to those observed in cantilever measurements. The large magnitude and slow kinetics of the contraction can be explained by an intermixed gold-sulphur layer that has recently been identified crystallographically. Our results illustrate the importance of crystal edges and grain boundaries in interface chemistry and have broad implications for the application of thiol-based SAMs, ranging from nanomechanical sensors to coating technologies. PMID:21946612

  3. Identification of the thiol ester linked lipids in apolipoprotein B

    Energy Technology Data Exchange (ETDEWEB)

    Huang, G.; Lee, D.M.; Singh, S.

    1988-03-08

    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 (/sup 14/C)methylamine at pH 8.5 at 30 degrees C. Covalent incorporation of (/sup 14/C)methylamine was observed with concomitant generation of new sulfhydryl groups, which could be blocked with (/sup 3/H)- or (/sup 14/C)iodoacetic acid. One type of the (/sup 14/C)methylamine-modified products was separated from the protein and was found to be lipid in nature. Its Rf 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.

  4. Organized thiol functional groups in mesoporous core shell colloids

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  5. Cloning and sequence analysis of D-erythrulose reductase from chicken: its close structural relation to tetrameric carbonyl reductases.

    Science.gov (United States)

    Maeda, Miki; Kaku, Hanae; Shimada, Mikio; Nishioka, Takaaki

    2002-07-01

    Sequence analysis of a cDNA for D-erythrulose reductase from chicken liver showed that the deduced open reading frame encodes the protein with a molecular mass of 26 kDa consisting of 246 amino acids. Although the reductase shares more than 60% identity in the amino acid sequence with the mouse tetrameric carbonyl reductase, these two enzymes have many biochemical differences; their substrate specificity, subcellular localization, organ distribution, etc. A three-dimensional structure of D-erythrulose reductase was predicted by comparative modeling based on the structure of the tetrameric carbonyl reductase (PDB entry = 1CYD). Most of the residues at the active site (within 4 A from the ligand) of the carbonyl reductase were also conserved in the D-erythrulose reductase. Nevertheless, Val190 and Leu146 in the active site of the tetrameric carbonyl reductase were substituted in the D-erythrulose reductase by Asn192 and His148, respectively. The substitutions in the active sites may be related to the difference in substrate specificity of the two enzymes. The phylogenic analysis of D-erythrulose reductase and the other related proteins suggests that the protein described as a carbonyl reductase D-erythrulose reductase. PMID:12200544

  6. Isolation and Characterization of cDNAs Encoding Leucoanthocyanidin Reductase and Anthocyanidin Reductase from Populus trichocarpa

    OpenAIRE

    Wang, Lijun; Jiang, Yuanzhong; Yuan, Li; Lu, Wanxiang; Yang, Li; Karim, Abdul; Luo, Keming

    2013-01-01

    Proanthocyanidins (PAs) contribute to poplar defense mechanisms against biotic and abiotic stresses. Transcripts of PA biosynthetic genes accumulated rapidly in response to infection by the fungus Marssonina brunnea f.sp. multigermtubi, treatments of salicylic acid (SA) and wounding, resulting in PA accumulation in poplar leaves. Anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR) are two key enzymes of the PA biosynthesis that produce the main subunits: (+)-catechin and (?)-...

  7. Cellular thiols and redox-regulated signal transduction.

    Science.gov (United States)

    Sen, C K

    2000-01-01

    In contrast to the conventional notion that reactive oxygen is mostly a trigger for oxidative damage of biological structures, now we know that low physiologically relevant concentrations of ROS can regulate a variety of key molecular mechanisms that may be linked with important cell functions (Fig. 4). Redox-based regulation of gene expression has emerged as a fundamental regulatory mechanism in cell biology. Several proteins, with apparent redox-sensing activity, have been described. Electron flow through side-chain functional CH2-SH groups of conserved cysteinyl residues in these proteins account for the redox-sensing properties. Protein thiol groups with high thiol-disulfide oxidation potentials are likely to be redox-sensitive. The ubiquitous endogenous thiols thioredoxin and glutathione are of central importance in redox signaling. Signals are transduced from the cell surface to the nucleus through phosphorylation and dephosphorylation chain reactions of cellular proteins at tyrosine and serine/threonine. Protein phosphorylation, one of the most fundamental mediators of cell signaling, is redox-sensitive. DNA-binding proteins are involved in the regulation of cellular processes such as replication, recombination, viral integration and transcription. Several studies show that the interaction of certain transcription regulatory proteins with their respective cognate DNA sites is also redox-regulated. Changes in the concentration of Ca2+i control a wide variety of cellular functions, including transcription and gene expression; Ca(2+)-driven protein phosphorylation and proteolytic processing of proteins are two major intracellular events that are implicated in signal transduction from the cell surface to the nucleus. Intracellular calcium homeostasis is regulated by the redox state of cellular thiols, and it is evident that cell calcium may play a critical role in the activation of the redox-sensitive transcription factor NF-kappa B. Among the several thiol agents tested for their efficacy in modulating cellular redox status, N-acetyl-L-cysteine and alpha-lipoic acid hold most promise for human use. A strong therapeutic potential of strategies that would modulate the cellular thioredoxin system has been also evident. PMID:10842745

  8. Adsorption of Dissolved Metals in the Berkeley Pit using Thiol-Functionalized Self-Assembled Monolayers on Mesoporous Supports (Thiol-SAMMS)

    International Nuclear Information System (INIS)

    The Berkeley Pit in Butte, Montana, is heavily contaminated with dissolved metals. Adsorption and extraction of these metals can be accomplished through the use of a selective adsorbent. For this research, the adsorbent used was thiol-functionalized Self-Assembled Monolayers on Mesoporous Supports (thiol-SAMMS), which was developed at Pacific Northwest National Laboratory (PNNL). Thiol-SAMMS selectively binds to numerous types of dissolved metals. The objective of this research was to evaluate the loading and kinetics of aluminum, beryllium, copper, and zinc on thiol-SAMMS. For the loading tests, a series of Berkeley Pit water to thiol-SAMMS ratios (mL:g) were tested. These ratios were 1000:1, 500:1, 100:1, and 50:1. Berkeley Pit water is acidic (pH ? 2.5). This can affect the performance of SAMMS materials. Therefore, the effect of pH was evaluated by conducting parallel series of loading tests wherein the Berkeley Pit water was neutralized before or after addition of thiol-SAMMS, and a series of kinetics tests wherein the Berkeley Pit water was neutralized before addition of thiol-SAMMS for the first test and was not neutralized for the second test. For the kinetics tests, one Berkeley Pit water to thiol-SAMMS ratio was tested, which was 2000:1. The results of the loading and kinetics tests suggest that a significant decrease in dissolved metal concentration at Berkeley Pit could be realized through neutralization of Berkeley Pit water. Thiol-SAMMS technology has a limited application under the highly acidic conditions posed by the Berkeley Pit. However, thiol-SAMMS could provide a secondary remedial technique which would complete the remedial system and remove dissolved metals from the Berkeley Pit to below drinking water standards.

  9. Severe depletion of cellular thiols and glutathione-related enzymes of a carmustine-resistant L1210 strain associates with collateral sensitivity to cyclophosphamide.

    Science.gov (United States)

    Institoris, E; Tretter, L; Gaál, D

    1993-01-01

    Cyclophosphamide (CPA) increased the life span of both carmustine (BCNU)-resistant (L1210/BCNU) and BCNU-sensitive L1210 (L1210/0) leukaemic mice; their sensitivity to CPA, however, was extremely different. The BCNU-resistant strain was much more sensitive (collaterally) to CPA than was its sensitive counterpart. The collateral sensitivity was accompanied by a severe reduction in the activity of glutathione-related enzymes and in protein thiol (SH) and non-protein SH levels in BCNU-resistant cells. The activity of glutathione reductase (GSSG-R) was 2 times higher in the L1210/0 cells than in the L1210/BCNU cells. Glutathione-S-transferase (GST) was also almost 2 times more active in the sensitive cells than in the resistant strain. To develop resistance against CPA with a single treatment (60 mg/kg) per passage, the L1210/BCNU strain needed 26 passages, whereas the L1210/0 strain required significantly fewer. The resistance developed against CPA was associated with a moderate elevation of thiols in the L1210/CPA cells, whereas this elevation was approximately 3 times more pronounced in the L1210/BCNU/CPA cells. The severely reduced activity of GST in the L1210/BCNU strain was markedly increased when these cells were made resistant to CPA; the GSSG-R activity, however, remained low, suggesting an irreversible injury of this enzyme by BCNU. PMID:8269595

  10. Control of dihydrofolate reductase messenger ribonucleic acid production

    Energy Technology Data Exchange (ETDEWEB)

    Leys, E.J.; Kellems, R.E.

    1981-11-01

    The authors used methotrexate-resistant mouse cells in which dihydrofolate reductase levels are approximately 500 times normal to study the effect of growth stimulation on dihydrofolate reductase gene expression. As a result of growth stimulation, the relative rate of dihydrofolate reductase protein synthesis increased threefold, reaching a maximum between 25 and 30 h after stimulation. The relative rate of dihydrofolate reductase messenger ribonucleic acid production (i.e., the appearance of dihydrofolate reductase messenger ribonucleic acid in the cytoplasm) increased threefold after growth stimulation and was accompanied by a corresponding increase in the relative steady-state level of dihydrofolate reductase ribonucleic acid in the nucleus. However, the increase in the nuclear level of dihydrofolate reductase ribonucleic acid was not accompanied by a significant increase in the relative rate of transcription of the dihydrofolate reductase genes. These data indicated that the relative rate of appearance of dihydrofolate reductase messenger ribonucleic acid in the cytoplasm depends on the relative stability of the dihydrofolate reductase ribonucleic acid sequences in the nucleus and is not dependent on the relative rate of transcription of the dihydrofolate reductase genes.

  11. Mercuric reductase activity and evidence of broad-spectrum mercury resistance among clinical isolates of rapidly growing mycobacteria

    International Nuclear Information System (INIS)

    Resistance to mercury was evaluated in 356 rapidly growing mycobacteria belonging to eight taxonomic groups. Resistance to inorganic Hg2+ ranged from 0% among the unnamed third biovariant complex of Mycobacterium fortuitum to 83% among M. chelonae-like organisms. With cell extracts and 203Hg(NO3)2 as the substrate, mercuric reductase (HgRe) activity was demonstrable in six of eight taxonomic groups. HgRe activity was inducible and required NADPH or NADH and a thiol donor for optimai activity. Species with HgRe activity were also resistant to organomercurial compounds, including phenylmercuric acetate. Attempts at intraspecies and intragenus transfer of HgRe activity by conjugation or transformation were unsuccessful. Mercury resistance is common in rapidly growing mycobacteria and appears to function via the same inducible enzyme systems already defined in other bacterial species. This system offers potential as a strain marker for epidemiologic investigations and for studying genetic systems in rapidly growing mycobacteria

  12. 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 [14C]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

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

    DEFF Research Database (Denmark)

    Sikanen, Tiina M; Lafleur, Josiane P.

    2013-01-01

    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.

  14. Solvent-Free Synthesis and Fluorescence of a Thiol-Reactive Sensor for Undergraduate Organic Laboratories

    OpenAIRE

    Patterson, Anastasia L.; May, Mary D.; Visser, Bryan J.; Kislukhin, Alexander A.; Vosburg, David A.

    2013-01-01

    A green organic laboratory experiment was developed in which students synthesize a sensor for thiols using a microscale, solventless Diels–Alder reaction at room temperature or 37 °C. The molecular probe is easily purified by column chromatography in a Pasteur pipet and characterized by thin-layer chromatography and NMR spectroscopy. The thiol-reactive sensor becomes intensely fluorescent upon exposure to thiols from N-acetylcysteine, bovine serum albumin, or human hair (pretreated with a red...

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

    OpenAIRE

    Claudino, Mauro

    2011-01-01

    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 (methyl...

  16. Influence of nar (nitrate reductase) genes on nitrate inhibition of formate-hydrogen lyase and fumarate reductase gene expression in Escherichia coli K-12.

    OpenAIRE

    Stewart, V.; Berg, B L

    1988-01-01

    In Escherichia coli, aerobiosis inhibits the synthesis of enzymes for anaerobic respiration (e.g., nitrate reductase and fumarate reductase) and for fermentation (e.g., formate-hydrogen lyase). Anaerobically, nitrate induces nitrate reductase synthesis and inhibits the formation of both fumarate reductase and formate-hydrogen lyase. Previous work has shown that narL+ is required for the effects of nitrate on synthesis of both nitrate reductase and fumarate reductase. Another gene, narK (whose...

  17. Resolution of oxidative stress by thioredoxin reductase: Cysteine versus selenocysteine

    Directory of Open Access Journals (Sweden)

    Brian Cunniff

    2014-01-01

    Full Text Available Thioredoxin reductase (TR catalyzes the reduction of thioredoxin (TRX, which in turn reduces mammalian typical 2-Cys peroxiredoxins (PRXs 1–4, thiol peroxidases implicated in redox homeostasis and cell signaling. Typical 2-Cys PRXs are inactivated by hyperoxidation of the peroxidatic cysteine to cysteine-sulfinic acid, and regenerated in a two-step process involving retro-reduction by sulfiredoxin (SRX and reduction by TRX. Here transient exposure to menadione and glucose oxidase was used to examine the dynamics of oxidative inactivation and reactivation of PRXs in mouse C10 cells expressing various isoforms of TR, including wild type cytoplasmic TR1 (Sec-TR1 and mitochondrial TR2 (Sec-TR2 that encode selenocysteine, as well as mutants of TR1 and TR2 in which the selenocysteine codon was changed to encode cysteine (Cys-TR1 or Cys-TR2. In C10 cells endogenous TR activity was insensitive to levels of hydrogen peroxide that hyperoxidize PRXs. Expression of Sec-TR1 increased TR activity, reduced the basal cytoplasmic redox state, and increased the rate of reduction of a redox-responsive cytoplasmic GFP probe (roGFP, but did not influence either the rate of inactivation or the rate of retro-reduction of PRXs. In comparison to roGFP, which was reduced within minutes once oxidants were removed reduction of 2-Cys PRXs occurred over many hours. Expression of wild type Sec-TR1 or Sec-TR2, but not Cys-TR1 or TR2, increased the rate of reduction of PRXs and improved cell survival after menadione exposure. These results indicate that expression levels of TR do not reduce the severity of initial oxidative insults, but rather govern the rate of reduction of cellular factors required for cell viability. Because Sec-TR is completely insensitive to cytotoxic levels of hydrogen peroxide, we suggest TR functions at the top of a redox pyramid that governs the oxidation state of peroxiredoxins and other protein factors, thereby dictating a hierarchy of phenotypic responses to oxidative insults.

  18. Integration between anticipatory blocking and redox signaling by the peroxiredoxin/thioredoxin/thioredoxin-reductase system.

    Science.gov (United States)

    Selvaggio, Gianluca; Coelho, Pedro M B M; Salvador, Armindo

    2014-10-01

    Cells are occasionally exposed to high H2O2 concentrations, often preceding exposure to other electrophylic compounds. Both H2O2 and these compounds can irreversibly modify protein thiols, with deleterious consequences. Induction of enzymatic defenses against those agents is too slow to avoid significant damage. Cells may solve this conundrum by reversibly "blocking" the thiols once H2O2 concentrations begin to increase. We term this mechanism "anticipatory blocking" because it acts in anticipation of irreversible damage upon detection of early signs of stress. Here we examine the design requirements for the Peroxiredoxin/Thioredoxin/Thioredoxin-Reductase/Protein-Dithiol System (PTTRDS) to effectively integrate H2O2 signaling and anticipatory blocking of protein dithiols as disulfides, and we compared them to the designs found in cells. To that effect, we developed a minimal model of the PTTRDS, and we defined a set of quantitative performance criteria that embody the requirements for (a) efficient scavenging capacity, (b) low NADPH consumption, (c) effective signal propagation, and (d) effective anticipatory blocking. We then sought the design principles (relationships among rate constants and species concentrations) that warrant fulfillment of all these criteria. Experimental data indicates that the design of the PTTRDS in human erythrocytes fulfills these principles and thus accomplishes effective integration between anticipatory blocking, antioxidant protection and redox signaling. A more general analysis suggests that the same principles hold in a wide variety of cell types and organisms. We acknowledge grants PEst-C/SAU/LA0001/2013-2014, PEst-OE/QUI/UI0612/2013, FCOMP-01-0124-FEDER-020978 (PTDC/QUI-BIQ/119657/2010) financed by FEDER through the "Programa Operacional Factores de Competitividade, COMPETE" and by national funds through "FCT, Fundação para a Ciência e a Tecnologia". PMID:26461388

  19. A Two-Photon Fluorescent Probe for Lysosomal Thiols in Live Cells and Tissues.

    Science.gov (United States)

    Fan, Jiangli; Han, Zhichao; Kang, Yao; Peng, Xiaojun

    2016-01-01

    Lysosome-specific fluorescent probes are exclusive to elucidate the functions of lysosomal thiols. Moreover, two-photon microscopy offers advantages of less phototoxicity, better three dimensional spatial localization, deeper penetration depth and lower self-absorption. However, such fluorescent probes for thiols are still rare. In this work, an efficient two-photon fluorophore 1,8-naphthalimide-based probe conjugating a 2,4-dinitrobenzenesulfonyl chloride and morpholine was designed and synthesized, which exhibited high selectivity and sensitivity towards lysosomal thiols by turn-on fluorescence method quantitatively and was successfully applied to the imaging of thiols in live cells and tissues by two-photon microscopy. PMID:26794434

  20. Solvent-Free Synthesis and Fluorescence of a Thiol-Reactive Sensor for Undergraduate Organic Laboratories.

    Science.gov (United States)

    Patterson, Anastasia L; May, Mary D; Visser, Bryan J; Kislukhin, Alexander A; Vosburg, David A

    2013-12-10

    A green organic laboratory experiment was developed in which students synthesize a sensor for thiols using a microscale, solventless Diels-Alder reaction at room temperature or 37 °C. The molecular probe is easily purified by column chromatography in a Pasteur pipet and characterized by thin-layer chromatography and NMR spectroscopy. The thiol-reactive sensor becomes intensely fluorescent upon exposure to thiols from N-acetylcysteine, bovine serum albumin, or human hair (pretreated with a reducing agent to reveal cysteine thiols in ?-keratin). This fluorescence is observable even with micrograms of probe. PMID:24415795

  1. 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

  2. Thermal and Chemical Stability of Thiol Bonding on Gold Nanostars.

    Science.gov (United States)

    Borzenkov, Mykola; Chirico, Giuseppe; D'Alfonso, Laura; Sironi, Laura; Collini, Maddalena; Cabrini, Elisa; Dacarro, Giacomo; Milanese, Chiara; Pallavicini, Piersandro; Taglietti, Angelo; Bernhard, Claire; Denat, Franck

    2015-07-28

    The stability of thiol bonding on the surface of star-shaped gold nanoparticles was studied as a function of temperature in water and in a set of biologically relevant conditions. The stability was evaluated by monitoring the release of a model fluorescent dye, Bodipy-thiol (BDP-SH), from gold nanostars (GNSs) cocoated with poly(ethylene glycol) thiol (PEG-SH). The increase in the BDP-SH fluorescence emission, quenched when bound to the GNSs, was exploited to this purpose. A maximum 15% dye release in aqueous solution was found when the bulk temperature of gold nanostars solutions was increased to T = 42 °C, the maximum physiological temperature. This fraction reduces 3-5% for temperatures lower than 40 °C. Similar results were found when the temperature increase was obtained by laser excitation of the near-infrared (NIR) localized surface plasmon resonance of the GNSs, which are photothermally responsive. Besides the direct impact of temperature, an increased BDP-SH release was observed upon changing the chemical composition of the solvent from pure water to phosphate-buffered saline and culture media solutions. Moreover, also a significant fraction of PEG-SH was released from the GNS surface due to the increase in temperature. We monitored it with a different approach, that is, by using a coating of ?-mercapto-?-amino PEG labeled with tetramethylrhodamine isothiocyanate on the amino group, that after heating was separated from GNS by ultracentrifugation and the released PEG was determined by spectrofluorimetric techniques on the supernatant solution. These results suggest some specific limitations in the use of the gold-thiolate bond for coating of nanomaterials with organic compounds in biological environments. These limitations come from the duration and the intensity of the thermal treatment and from the medium composition and could also be exploited in biological media to modulate the in vivo release of drugs. PMID:26154493

  3. Spontaneous assembly of silylethane-thiol derivatives on Au(111): a chemically robust thiol protecting group as the precursor for the direct formation of aromatic gold thiolate monolayers.

    Science.gov (United States)

    Niebel, Claude; Calard, François; Jarrosson, Thibaut; Lère-Porte, Jean-Pierre; Breton, Tony; Serein-Spirau, Françoise

    2015-05-01

    Self-assembled monolayers (SAMs) on gold were obtained by the direct absorption of a fully conjugated phenylenethienylene derivative () presenting robust silylethane-thiol protecting groups as anchoring agents. The thiol deprotection and SAM formation have been evidenced by quartz crystal microbalance (QCM) measurements and X-ray photoelectron spectroscopy (XPS), and have been compared to the SAM obtained from its thioacetate analog (5). The chemically robust silylethane-thiol protecting group appeared as a surprisingly effective anchoring agent for the preparation of aromatic SAMs on Au(111), suitable for subsequent post-functionalization. PMID:25848655

  4. Suspended hybrid films assembled from thiol-capped gold nanoparticles

    OpenAIRE

    Zhang, Yu Xin; Huang, Ming; Hao, Xiao Dong; Dong, Meng; Li, Xin Lu; Huang, Jia Mu

    2012-01-01

    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 p...

  5. Communication: vacuum ultraviolet photoabsorption of interstellar icy thiols.

    Science.gov (United States)

    Bhuin, Radha Gobinda; Sivaraman, Bhalamurugan; Lo, Jen-Iu; Sekhar, B N Raja; Cheng, Bing-Ming; Pradeep, Thalappil; Mason, Nigel John

    2014-12-21

    Following the recent identification of ethanethiol in the interstellar medium (ISM) we have carried out Vacuum UltraViolet (VUV) spectroscopy studies of ethanethiol (CH3CH2SH) from 10 K until sublimation in an ultrahigh vacuum chamber simulating astrochemical conditions. These results are compared with those of methanethiol (CH3SH), the lower order thiol also reported to be present in the ISM. VUV spectra recorded at higher temperature reveal conformational changes in the ice and phase transitions whilst evidence for dimer production is also presented. PMID:25527912

  6. Liquid crystalline polymers with chiral side-chain thiols.

    Czech Academy of Sciences Publication Activity Database

    Bubnov, Alexej M.; Kašpar, Miroslav; Sedláková, Zde?ka; Gari?, M.; Obadovi?, D. Ž.; Ilavský, Michal

    Warsaw : Military University of Technology, 2005, s. 11-19. ISBN N. [Conference on Liquid Crystals /16./. Stare Jablonki (PL), 18.09.2005-21.09.2005] R&D Projects: GA ?R GP202/03/P011; GA ?R GA202/05/0431; GA AV ?R IAA4112401 Grant ostatní: COST(XE) D35 WG13 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40500505 Keywords : chiral liquid crystals * polybutadiene diols * thiols * side-chain polymers * mesomorphis properties Subject RIV: BM - Solid Matter Physics ; Magnetism

  7. Biliverdin reductase: A major physiologic cytoprotectant

    OpenAIRE

    Barañano, David E.; Rao, Mahil; Ferris, Christopher D.; Snyder, Solomon H.

    2002-01-01

    Bilirubin, an abundant pigment that causes jaundice, has long lacked any clear physiologic role. It arises from enzymatic reduction by biliverdin reductase of biliverdin, a product of heme oxygenase activity. Bilirubin is a potent antioxidant that we show can protect cells from a 10,000-fold excess of H2O2. We report that bilirubin is a major physiologic antioxidant cytoprotectant. Thus, cellular depletion of bilirubin by RNA interference markedly augments tissue levels of reactive oxygen spe...

  8. Tinkering with a viral ribonucleotide reductase

    OpenAIRE

    Lembo, David

    2009-01-01

    Ribonucleotide reductase (RNR), a crucial enzyme for nucleotide anabolism, is encoded by all living organisms and by large DNA viruses such as the herpesviruses. Surprisingly, the beta-herpesvirus subfamily RNR R1 subunit homologues are catalytically inactive and their function remained enigmatic for many years. Recent work sheds light on the function of M45, the murine cytomegalovirus R1 homologue; during viral evolution, M45 apparently lost its original RNR activity but gained the ability, ...

  9. Ribonucleotide reductases: essential enzymes for bacterial life

    OpenAIRE

    Torrents, Eduard

    2014-01-01

    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 importan...

  10. Active sites of thioredoxin reductases: Why selenoproteins?

    OpenAIRE

    Gromer, Stephan; Johansson, Linda; Bauer, Holger; Arscott, L. David; Rauch, Susanne; Ballou, David P.; Charles H. Williams; Schirmer, R Heiner; Arnér, Elias S. J.

    2003-01-01

    Selenium, an essential trace element for mammals, is incorporated into a selected class of selenoproteins as selenocysteine. All known isoenzymes of mammalian thioredoxin (Trx) reductases (TrxRs) employ selenium in the C-terminal redox center -Gly-Cys-Sec-Gly-COOH for reduction of Trx and other substrates, whereas the corresponding sequence in Drosophila melanogaster TrxR is -Ser-Cys-Cys-Ser-COOH. Surprisingly, the catalytic competence of these orthologous enzymes is similar, whereas direct S...

  11. Study of Highly Selective and Efficient Thiol Derivatization using Selenium Reagents by Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Kehua; Zhang, Yun W.; Tang, Bo; Laskin, Julia; Roach, Patrick J.; Chen, Hao

    2010-08-15

    Biological thiols are critical physiological components and their detection often involves derivatization. This paper reports a systemic mass spectrometry (MS) investigation of the cleavage of Se-N bond by thiol to form a new Se-S bond, the new selenium chemistry for thiol labeling. Our data shows that the reaction is highly selective, rapid, reversible and efficient. For instance, among twenty amino acids, only cysteine was found to be reactive with Se-N containing reagents and the reaction takes place in seconds. By adding dithiothreitol (DTT), the newly formed Se-S bond of peptides/proteins can be reduced back to free thiol. The high selectivity and excellent reversibility of the reaction provide potential of using this chemistry for selective identification of thiol compounds or enriching and purifying thiol peptides/proteins. In addition, the derivatized thiol peptides have interesting dissociation behavior, which is tunable using different selenium reagents. For example, by introducing an adjacent nucleophilic group into the selenium reagent in the case of using ebselen, the reaction product of ebselen with glutathione (GSH) is easy to lose the selenium tag upon collision-induced dissociation (CID), which is useful to "fish out" those peptides containing free cysteine residues by precursor ion scan. By contrast, the selenium tag of N-(phenylseleno) phthalimide reagent can be stable and survive in CID process, which would be of value in pinpointing thiol location using a top-down proteomic approach. Also, the high conversion yield of the reaction allows the counting of total number of thiol in proteins. We believe that ebselen or N-(phenylseleno) phthalimide as tagging thiol-protein reagents will have important applications in both qualitative and quantitative analysis of different thiol-proteins derived from living cells by MS method.

  12. INHIBITION OF TYPE I 5?-REDUCTASE BY MEDICINAL PLANT EXTRACTS

    OpenAIRE

    Patil Vijaya; Samuel Grace; Mirapurkar Shubhangi; R. Krishna Mohan; Dasgupta Debjani

    2011-01-01

    Type I 5?-reductase has been implicated in skin disorders such as acne, hirsutism and male pattern baldness and its inhibition offers a potential treatment for these disorders. The aim of this study was to investigate the inhibition of type I 5?-reductase activity by extracts from Indian medicinal plants. Plant extracts were screened and selected based on their ability to inhibit Propionibacterium acnes and Staphylococcus epidermidis. Since type I 5?-reductase metabolises testosterone to ?4-a...

  13. Cloning and nitrate induction of nitrate reductase mRNA

    OpenAIRE

    Cheng, Chi-Lien; Dewdney, Julia; Kleinhofs, Andris; Goodman, Howard M.

    1986-01-01

    Nitrate is the major source of nitrogen taken from the soil by higher plants but requires reduction to ammonia prior to incorporation into amino acids. The first enzyme in the reducing pathway is a nitrate-inducible enzyme, nitrate reductase (EC 1.6.6.1). A specific polyclonal antiserum raised against purified barley nitrate reductase has been used to immunoprecipitate in vivo labeled protein and in vitro translation products, demonstrating that nitrate induction increases nitrate reductase p...

  14. SCREENING OF HMG CO A REDUCTASE INHIBITOR PRODUCING MARINE ACTINOMYCETES

    OpenAIRE

    SRINU, PHANI BHUSHAN,MOGES, SRILAKSHMI, SANKAR, PRABHAKAR,LAKSHMINARAYANA

    2013-01-01

    The objective of the present study was screening of 3-hydroxy-3- methyl glutaryl Co A (HMG CoA) reductase inhibitor producing marine actinomycetes. A total of 65 morphologically different actinomycetes were screened for HMG CoA reductase inhibitor production in a two stage submerged fermentation and evaluated for HMG CoA reductase inhibitor activity by agar diffusion and thin layer chromatography technique using lovostatin as a control. Among 65 marine Actinomycete strains, only one strain pr...

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

    Science.gov (United States)

    Zheng, Feng; Pratt, Derek A

    2013-09-25

    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

  16. Direct Synthesis of Thioethers from Carboxylates and Thiols Catalyzed by FeCl3.

    Science.gov (United States)

    Venkatesham, Kunuru; Bhujanga Rao, Chitturi; Dokuburra, Chanti Babu; Bunce, Richard A; Venkateswarlu, Yenamandra

    2015-11-20

    A new and efficient method has been developed for the synthesis of thioethers from carboxylates and thiols. The reaction proceeds via a Fe(III)-catalyzed direct displacement of carboxylates from benzylic or allylic esters by heterocyclic thiols. Short reaction times, good to excellent yields of products, and few side reactions are the significant features of the new protocol. PMID:26497695

  17. The role of thiols in cellular response to radiation and drugs

    International Nuclear Information System (INIS)

    Cellular nonprotein thiols (NPSH) consist of glutathione (GSH) and other low molecular weight species such as cysteine, cysteamine, and coenzyme A. GSH is usually less than the total cellular NPSH, and with thiol reactive agents, such as diethyl maleate (DEM), its rate of depletion is in part dependent upon the cellular capacity for its resynthesis. If resynthesis is blocked by buthionine-S,R-sulfoximine(BSO), the NPSH, including GSH, is depleted more rapidly, Cellular thiol depletion by diamide, N-ethylmaleimide, and BSO may render oxygenated cells more sensitive to radiation. These cells may or may not show a reduction in the oxygen enhancement ratio (OER). Human A549 lung carcinoma cells depleted of their NPSH either by prolonged culture or by BSO treatment do not show a reduced OER but do show increased aerobic responses to radiation. Some nitroheterocyclic radiosensitizing drugs also deplete cellular thiols under aerobic conditions. Such reactivity may be the reason that they show anomalous radiation sensitization (i.e., better than predicted on the basis of electron affinity). Other nitrocompounds, such as misonidazole, are activated under hypoxic conditions to radical intermediates. When cellular thiols are depleted peroxide is formed. Under hypoxic conditions thiols are depleted because metabolically reduced intermediates react with GSH instead of oxygen. Thiol depletion, under hypoxic conditions, may be the reason that misonidazole and other nitrocompounds show an extra enhancement ratio with hypoxic cells. Thiol depletion by DEM or BSO alters the radiation response of hypoxic cells to misonidazole

  18. Visible-Light-Driven Photocatalytic Initiation of Radical Thiol-Ene Reactions Using Bismuth Oxide.

    Science.gov (United States)

    Fadeyi, Olugbeminiyi O; Mousseau, James J; Feng, Yiqing; Allais, Christophe; Nuhant, Philippe; Chen, Ming Z; Pierce, Betsy; Robinson, Ralph

    2015-12-01

    A nontoxic and inexpensive photocatalytic initiation of anti-Markovnikov hydrothiolation of olefins using visible light is reported. This method is characterized by low catalyst loading, thereby enabling a mild and selective method for radical initiation in thiol-ene reactions between a wide scope of olefins and thiols. PMID:26572219

  19. Charge Transport of MoS2 Supported by Thiol-Decorated Self-Assembled Monolayer

    Science.gov (United States)

    Naveh, Doron; Artel, Vlada; Kirshner, Moshe

    2015-03-01

    Intrinsic charge transport in MoS2 supported by thiols was recently reported and was attributed to passivation of sulfur vacancies and suppression of charged impurities from the dielectric substrate. In this talk we will present the transport characteristics of single layer and few-layer MoS2 on thiol-decorated self-assembled alkyl-siloxane monolayer.

  20. Lithium BINOL phosphate catalyzed desymmetrization of meso-epoxides with aromatic thiols.

    Science.gov (United States)

    Ingle, Gajendrasingh; Mormino, Michael G; Antilla, Jon C

    2014-11-01

    A highly enantioselective method for desymmetrization of meso-epoxides using thiols is reported. This is the first example of epoxide activation achieved using metal BINOL phosphates. The reaction has a broad scope in terms of epoxide substrates and aromatic thiol nucleophiles. The resulting ?-hydroxyl sulfides are obtained in excellent yield and enantioselectivity. PMID:25317934

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

    DEFF Research Database (Denmark)

    Lafleur, Josiane P.; Kwapiszewski, Radoslaw; Jensen, Thomas Glasdam; Kutter, Jörg Peter

    ” and “ene” monomers present in the microfluidic chip bulk material provides a simple and efficient way of tuning the chip’s surface chemistry. Here, thiol-ene chips displaying an excess of functional thiol groups at their surfaces are functionalized with biotin and streptavidin in a controlled fashion...

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

    DEFF Research Database (Denmark)

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

    " and "ene" monomers present in the microfluidic chip bulk material provides a simple and efficient way of tuning the chip's surface chemistry. Here, thiol-ene chips displaying an excess of functional thiol groups at their surfaces are functionalized with biotin and streptavidin in a controlled fashion...

  3. Distribution and immunological characterization of microbial aldehyde reductases.

    Science.gov (United States)

    Kataoka, M; Shimizu, S; Yamada, H

    1992-01-01

    The distribution of microbial aldo-keto reductases was examined and their immunochemical characterization was performed. p-Nitrobenzaldehyde, pyridine-3-aldehyde and ethyl 4-chloro-3-oxobutanoate reductase activities were found to be widely distributed in a variety of microorganisms. In immunodiffusion studies, most yeasts belonging to the genera Sporobolomyces, Sporidiobolus and Rhodotorula formed precipitin bands with anti-Sporobolomyces salmonicolor aldehyde reductase serum. Furthermore, the results of immunotitration experiments suggested that Sporobolomyces salmonicolor AKU 4429 contains other enzyme(s) which can reduce p-nitrobenzaldehyde, pyridine-3-aldehyde and/or ethyl 4-chloro-3-oxobutanoate, and which are inactivated by anti-Sporobolomyces salmonicolor aldehyde reductase serum. PMID:1510561

  4. Sepiapterin reductase deficiency - Genetics Home Reference [Genetics Home Reference (Conditions)

    Lifescience Database Archive (English)

    Full Text Available Conditions Genes Chromosomes Handbook Glossary Resources Sepiapterin reductase deficiency Relate ... Movement abnormalities are often worse late in the day . Most affected individuals have delayed developmen ...

  5. SCREENING OF HMG CO A REDUCTASE INHIBITOR PRODUCING MARINE ACTINOMYCETES

    Directory of Open Access Journals (Sweden)

    SRINU, PHANI BHUSHAN,MOGES, SRILAKSHMI, SANKAR, PRABHAKAR,LAKSHMINARAYANA

    2013-09-01

    Full Text Available The objective of the present study was screening of 3-hydroxy-3- methyl glutaryl Co A (HMG CoA reductase inhibitor producing marine actinomycetes. A total of 65 morphologically different actinomycetes were screened for HMG CoA reductase inhibitor production in a two stage submerged fermentation and evaluated for HMG CoA reductase inhibitor activity by agar diffusion and thin layer chromatography technique using lovostatin as a control. Among 65 marine Actinomycete strains, only one strain produced HMG Co A reductase inhibitor

  6. A glutathione-specific aldose reductase of Leishmania donovani and its potential implications for methylglyoxal detoxification pathway.

    Science.gov (United States)

    Rath, Jyoti; Gowri, V S; Chauhan, Swati C; Padmanabhan, Prasad K; Srinivasan, N; Madhubala, Rentala

    2009-01-15

    Methylglyoxal is mainly catabolized by two major enzymatic pathways. The first is the ubiquitous detoxification pathway, the glyoxalase pathway. In addition to the glyoxalase pathway, aldose reductase pathway also plays a crucial role in lowering the levels of methylglyoxal. The gene encoding aldose reductase (ALR) has been cloned from Leishmania donovani, a protozoan parasite causing visceral leishmaniasis. DNA sequence analysis revealed an open reading frame (ORF) of approximately 855 bp encoding a putative protein of 284 amino acids with a calculated molecular mass of 31.7 kDa and a predicted isoelectric point of 5.85. The sequence identity between L. donovani ALR (LdALR) and mammals and plants is only 36-44%. The ORF is a single copy gene. A protein with a molecular mass that matched the estimated approximately 74 kDa according to the amino acid composition of LdALR with a maltose binding tag present at its N-terminal end was induced by heterologous expression of LdALR in Escherichia coli. In the presence of glutathione, recombinant LdALR reduced methylglyoxal with a K(m) of approximately 112 microM. Comparative structural analysis of the human ALR structure with LdALR model suggests that the active site anchoring the N-terminal end of the glutathione is highly conserved. However, the C-terminal end of the glutathione backbone is expected to be exposed in LdALR, as the residues anchoring the C-terminal end of the glutathione backbone come from the three loop regions in human, which are apparently shortened in the LdALR structure. Thus, the computational analysis provides clues about the expected mode of glutathione binding and its interactions with the protein. This is the first report of the role of an ALR in the metabolic disposal of methylglyoxal in L. donovani and of thiol binding to a kinetoplastid aldose reductase. PMID:18983902

  7. The association between plasma thiol levels and left ventricular diastolic dysfunction in patient with hypertension.

    Science.gov (United States)

    Erkus, Musluhittin Emre; Altiparmak, Ibrahim Halil; Akyuz, Ali Riza; Demirbag, Recep; Sezen, Yusuf; Gunebakmaz, Ozgur; Neselioglu, Salim; Erel, Ozcan

    2015-12-01

    The balance of oxidant and antioxidant status plays an important role in the left ventricular diastolic dysfunction (LVDD) in patients with hypertension (HT). Thiol is an important part of antioxidant system in the body. The aim of this study was to investigate the relationship between plasma thiol levels and LVDD in patients with HT. A total of 138 patients with newly diagnosed essential hypertensive and 20 age-gender matched subjects as control group enrolled in the study. After echocardiographic assessment, the hypertensive patients were divided into three groups: Group 1: without LVDD (n = 41); group 2: with LVDD grade 1 (n = 57); and group 3: with LVDD grade 2 (n = 40). Plasma thiol, lipid and glucose levels were measured in all subjects. Plasma thiol levels were significantly different between the groups (all of p role in the pathogenesis of diastolic function. Increased thiol levels may provide protection against the development of diastolic dysfunction. PMID:26252832

  8. Thiol-independent activity of a cholesterol-binding enterohemolysin produced by enteropathogenic Escherichia coli

    Directory of Open Access Journals (Sweden)

    Figueirêdo P.M.S.

    2003-01-01

    Full Text Available Enterohemolysin produced by Escherichia coli associated with infant diarrhea showed characteristics similar to those of thiol-activated hemolysins produced by Gram-positive bacteria, including inactivation by cholesterol, lytic activity towards eukaryotic cells and thermoinstability. However, enterohemolysin activity was not inactivated by oxidation or by SH group-blocking agents (1 mM HgCl2, 1 mM iodoacetic acid and the hemolysin (100 µg/ml was not lethal to mice, in contrast to the lethality of the thiol-activated hemolysin family to animals. Earlier reports showed that intravenous injection of partially purified streptolysin O preparations (0.2 µg was rapidly lethal to mice. These results suggest that E. coli enterohemolysin is not a thiol-activated hemolysin, despite its ability to bind cholesterol, probably due to the absence of free thiol-group(s that characterize the active form of the thiol-activated hemolysin molecule.

  9. Thiol-independent activity of a cholesterol-binding enterohemolysin produced by enteropathogenic Escherichia coli

    Scientific Electronic Library Online (English)

    P.M.S., Figueirêdo; C.F., Catani; T., Yano.

    2003-11-01

    Full Text Available Enterohemolysin produced by Escherichia coli associated with infant diarrhea showed characteristics similar to those of thiol-activated hemolysins produced by Gram-positive bacteria, including inactivation by cholesterol, lytic activity towards eukaryotic cells and thermoinstability. However, entero [...] hemolysin activity was not inactivated by oxidation or by SH group-blocking agents (1 mM HgCl2, 1 mM iodoacetic acid) and the hemolysin (100 µg/ml) was not lethal to mice, in contrast to the lethality of the thiol-activated hemolysin family to animals. Earlier reports showed that intravenous injection of partially purified streptolysin O preparations (0.2 µg) was rapidly lethal to mice. These results suggest that E. coli enterohemolysin is not a thiol-activated hemolysin, despite its ability to bind cholesterol, probably due to the absence of free thiol-group(s) that characterize the active form of the thiol-activated hemolysin molecule.

  10. Bioreduction and reoxidation of uranium enhanced by thiol functional groups in natural organic matter.

    Science.gov (United States)

    Luo, Hong-Wei; Xu, Fang

    2016-03-01

    Although natural organic matter (NOM) is known to affect biological reduction of U(VI) and subsequent reoxidation of U(IV), the underlying mechanisms remain unclear. This study investigated the redox reactions of sulfide with NOM to form thiol functional groups, which can greatly enhance U(VI) bioreduction and U(IV) reoxidation. Results showed that humic acid (HA) was found to be more effective than fulvic acid (FA) in producing thiol groups, both U(VI) bioreduction and U(IV) reoxidation rates increased with the increase of thiols content in HA and FA. These findings suggested that among other redox sites, thiol groups in NOM may play an important role in the electron transport between uranium and microbial cells, and are of great environmental implications because they provided direct proof that thiol groups are responsible for bioremediation and immobilization of uranium when it enters into the natural environments such as soil and groundwater. PMID:26751128

  11. Widespread occurrence of bacterial thiol methyltransferases and the biogenic emission of methylated sulfur gases

    Energy Technology Data Exchange (ETDEWEB)

    Drotar, A.; Burton, G.A. Jr.; Tavernier, J.E.; Fall, R.

    1987-07-01

    A majority of heterotrophic bacteria isolated from soil, water, sediment, vegetation, and marine algae cultures methylated sulfide, producing methanethiol. This was demonstrated (i) with intact cells by measuring the emission of methanethiol with a sulfur-selective chemiluminescence detector, and (ii) in cell extracts by detection of sulfide-dependent thiol methyltransferase activity. Extracts of two Pseudomonas isolates were fractionated by gel-filtration and ion-exchange chromatography, and with sulfide as the substrate a single peak of thiol methyltransferase activity was seen in each case. Extracts of several bacterial strains also contained thiol methyltransferase activity with organic thiols as substrates. Thus, S-adenosylmethionine-dependent thiol methyltransferase activities are widespread in bacteria and may contribute to biogenic emissions of methylated sulfur gases and to the production of methyl thioethers.

  12. Alkyl thiols as a sulfur precursor for the preparation of monodisperse metal sulfide nanostructures

    Science.gov (United States)

    Jun, Shinae; Jang, Eunjoo; Chung, Youngsu

    2006-10-01

    We demonstrate a new method for preparing metal sulfide nanocrystals using alkyl thiols as a sulfur precursor. Alkyl thiols have many advantages for practical synthesis because they are miscible with most organic solvents and very stable under an air atmosphere. CdS nanocrystals were made with CdO and thiols with different alkyl chains such as n-octanethiol and octadecanethiol. They exhibited uniform size, highly crystalline structure and a sharp photoluminescence spectrum. Also, CdSe/CdS core/shell nanocrystals can be prepared by single injection of a mixture consisting of alkyl thiol and Se in trioctylphosphine to a Cd precursor. A reaction scheme is proposed as alkyl thiols react with the metal precursor to form stable metal thiolate intermediates during the initial period of reaction, and the thiolate decomposes slowly to form homogeneous nuclei.

  13. Alkyl thiols as a sulfur precursor for the preparation of monodisperse metal sulfide nanostructures

    International Nuclear Information System (INIS)

    We demonstrate a new method for preparing metal sulfide nanocrystals using alkyl thiols as a sulfur precursor. Alkyl thiols have many advantages for practical synthesis because they are miscible with most organic solvents and very stable under an air atmosphere. CdS nanocrystals were made with CdO and thiols with different alkyl chains such as n-octanethiol and octadecanethiol. They exhibited uniform size, highly crystalline structure and a sharp photoluminescence spectrum. Also, CdSe/CdS core/shell nanocrystals can be prepared by single injection of a mixture consisting of alkyl thiol and Se in trioctylphosphine to a Cd precursor. A reaction scheme is proposed as alkyl thiols react with the metal precursor to form stable metal thiolate intermediates during the initial period of reaction, and the thiolate decomposes slowly to form homogeneous nuclei

  14. Moderate physical exercise induces the oxidation of human blood protein thiols.

    Science.gov (United States)

    Inayama, Takayo; Oka, Jun; Kashiba, Misato; Saito, Makoto; Higuchi, Mitsuru; Umegaki, Keizo; Yamamoto, Yorihiro; Matsuda, Mitsuo

    2002-03-15

    Exercise is known to induce the oxidation of blood low-molecular-weight (LMW) thiols such as reduced glutathione (GSH). We previously reported that full-marathon running induced a decrease in human plasma levels of protein-bound sulfhydryl groups (p-SHs). Moderate exercise, a 30-min running at the intensity of the individual ventilatory threshold, performed by untrained healthy females caused a significant decrease in erythrocyte levels of p-SHs (mostly hemoglobin cysteine residues) and LMW thiols, but their levels returned to each baseline by 2 h. No significant change in plasma LMW thiols was observed. However, plasma levels of p-SHs significantly decreased after running and remained unchanged after 24 h. These results suggest that moderate exercise causes the oxidation of blood thiols, especially protein-bound thiols. PMID:12148696

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

    DEFF Research Database (Denmark)

    Lafleur, Josiane P.; Kwapiszewski, Radoslaw

    2012-01-01

    The ability to immobilize biomolecules at specific locations on the surface of solid supports is central to many biochip applications. This paper reports the rapid one-step photochemical surface patterning of biomolecules in thiol-ene microfluidic chips. Adjusting the stoichiometric ratio of “thiol” and “ene” monomers present in the microfluidic chip bulk material provides a simple and efficient way of tuning the chip’s surface chemistry. Here, thiol-ene chips displaying an excess of functional thiol groups at their surfaces are functionalized with biotin and streptavidin in a controlled fashion using photolithography. We also present quantitative data on the number of functional groups available for surface modification on thiol-ene substrates and their stability.

  16. NAD-dependent cross-linking of dinitrogenase reductase and dinitrogenase reductase ADP-ribosyltransferase from Rhodospirillum rubrum.

    OpenAIRE

    Grunwald, S K; Ludden, P W

    1997-01-01

    Chemical cross-linking of dinitrogenase reductase and dinitrogenase reductase ADP-ribosyltransferase (DRAT) from Rhodospirillum rubrum has been investigated with a cross-linking system utilizing two reagents, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and sulfo-N-hydroxysuccinimide. Cross-linking between dinitrogenase reductase and DRAT requires the presence of NAD, the cellular ADP-ribose donor, or a NAD analog containing an unmodified nicotinamide group, such as nicotinamide hypoxanthin...

  17. Functional Diversity of Cysteine Residues in Proteins and Unique Features of Catalytic Redox-active Cysteines in Thiol Oxidoreductases

    OpenAIRE

    Fomenko, Dmitri E; Marino, Stefano M.; GLADYSHEV, Vadim N.

    2008-01-01

    Thiol-dependent redox systems are involved in regulation of diverse biological processes, such as response to stress, signal transduction, and protein folding. The thiol-based redox control is provided by mechanistically similar, but structurally distinct families of enzymes known as thiol oxidoreductases. Many such enzymes have been characterized, but identities and functions of the entire sets of thiol oxidoreductases in organisms are not known. Extreme sequence and structural divergence ma...

  18. Rapid and simple preparation of thiol-ene emulsion-templated monoliths and their application as enzymatic microreactors

    DEFF Research Database (Denmark)

    Lafleur, Josiane P; Senkbeil, Silja; Novotny, Jakub; Nys, Gwenaël; Bøgelund, Nanna; Rand, Kasper D; Foret, Frantisek; Kutter, Jörg P

    2015-01-01

    A novel, rapid and simple method for the preparation of emulsion-templated monoliths in microfluidic channels based on thiol-ene chemistry is presented. The method allows monolith synthesis and anchoring inside thiol-ene microchannels in a single photoinitiated step. Characterization by scanning electron microscopy showed that the methanol-based emulsion templating process resulted in a network of highly interconnected and regular thiol-ene beads anchored solidly inside thiol-ene microchannels. ...

  19. Modifications of cellular thiols during growth and squamous differentiation of cultured human bronchial epithelial cells.

    Science.gov (United States)

    Atzori, L; Dypbukt, J M; Hybbinette, S S; Moldéus, P; Grafström, R C

    1994-03-01

    Thiol modifications during growth and differentiation of cultured normal human bronchial epithelial cells was studied by analysis of their content and redox state of low-molecular-weight thiols and protein thiols. Subculture of the cells with trypsin decreased the cellular content of the major low-molecular-weight thiol, i.e., reduced glutathione, although the glutathione content had returned to levels comparable to those before subculture already after 4 h in conjunction with cell attachment. During subsequent culture, increases in the cellular contents of glutathione, total cysteine equivalents, and total protein thiols occurred. These modifications in the amounts and redox balance of thiols were transient and preceded the major growth phase. Exposure of cells at clonal density to either diethylmaleate, a thiol-depleting agent, or buthionine sulfoximine, an inhibitor of glutathione synthesis, decreased the proliferative ability of the cells as demonstrated by a markedly decreased colony forming efficiency. Moreover, in mass cultures exposed to buthionine sulfoximine, a marked depletion of the glutathione content was again accompanied by inhibition of growth. Exposure of the cells to agents known to induce growth arrest and terminal squamous differentiation, i.e., fetal bovine serum, Ca2+, or transforming growth factor-beta 1, resulted in increased levels of reduced glutathione. No consistent alteration in the contents of the other thiols was noted. Overall, the results demonstrate consistent variations in the amounts and redox state of cellular thiols, particularly reduced glutathione, supporting a role of thiols in regulation of growth and squamous differentiation of human bronchial epithelial cells. PMID:8125149

  20. Mechanism of action of clostridial glycine reductase: Isolation and characterization of a covalent acetyl enzyme intermediate

    International Nuclear Information System (INIS)

    Clostridial glycine reductase consists of proteins A, B, and C and catalyzes the reaction glycine + Pi + 2e- ? acetyl phosphate + NH4+. Evidence was previously obtained that is consistent with the involvement of an acyl enzyme intermediate in this reaction. The authors now demonstrate that protein C catalyzes exchange of [32P]Pi into acetyl phosphate, providing additional support for an acetyl enzyme intermediate on protein C. Furthermore, they have isolated acetyl protein C and shown that it is qualitatively, catalytically competent. Acetyl protein C can be obtained through the forward reaction from protein C and Se-(carboxymethyl)selenocysteine-protein A, which is generated by the reaction of glycine with proteins A and B. Acetyl protein C can also be generated through the reverse reaction by the addition of acetyl phosphate to protein C. Both procedures lead to the same acetyl enzyme. The acetyl enzyme reacts with Pi to give acetyl phosphate. When [14C]acetyl protein C is denaturated with TCA and redissolved with urea, radioactivity remained associated with the protein. Treatment with KBH4 removes all the radioactivity associated with protein C, resulting in the formation of [14C]ethanol. They conclude that a thiol group on protein C is acetylated. Proteins A and C together catalyze the exchange of tritium atoms from [3H]H2O into acetyl phosphate. This exchange reaction supports the proposal that an enol of the acetyl enzyme is an intermediate in the reaction sequence

  1. Structure and function of NADPH-cytochrome P450 reductase and nitric oxide synthase reductase domain

    International Nuclear Information System (INIS)

    NADPH-cytochrome P450 reductase (CPR) and the nitric oxide synthase (NOS) reductase domains are members of the FAD-FMN family of proteins. The FAD accepts two reducing equivalents from NADPH (dehydrogenase flavin) and FMN acts as a one-electron carrier (flavodoxin-type flavin) for the transfer from NADPH to the heme protein, in which the FMNH ·/FMNH2 couple donates electrons to cytochrome P450 at constant oxidation-reduction potential. Although the interflavin electron transfer between FAD and FMN is not strictly regulated in CPR, electron transfer is activated in neuronal NOS reductase domain upon binding calmodulin (CaM), in which the CaM-bound activated form can function by a similar mechanism to that of CPR. The oxygenated form and spin state of substrate-bound cytochrome P450 in perfused rat liver are also discussed in terms of stepwise one-electron transfer from CPR. This review provides a historical perspective of the microsomal mixed-function oxidases including CPR and P450. In addition, a new model for the redox-linked conformational changes during the catalytic cycle for both CPR and NOS reductase domain is also discussed

  2. Photo-curable siloxane hybrid material fabricated by a thiol-ene reaction of sol-gel synthesized oligosiloxanes.

    Science.gov (United States)

    Kim, Joon-Soo; Yang, SeungCheol; Park, HyungJin; Bae, Byeong-Soo

    2011-06-01

    The thiol-ene reaction of a sol-gel synthesized oligosiloxane thiol-ene mixture was processed through UV irradiation, resulting in transparency, high refractive index, good thermal stability and especially excellent electrical insulation materials. It provides new strong potential of the thiol-ene system for application in dielectric materials. PMID:21537501

  3. Biliverdin reductase: a target for cancer therapy?

    OpenAIRE

    Gibbs, Peter E. M; Miralem, Tihomir; Maines, Mahin D.

    2015-01-01

    Biliverdin reductase (BVR) is a multifunctional protein that is the primary source of the potent antioxidant, bilirubin. BVR regulates activities/functions in the insulin/IGF-1/IRK/PI3K/MAPK pathways. Activation of certain kinases in these pathways is/are hallmark(s) of cancerous cells. The protein is a scaffold/bridge and intracellular transporter of kinases that regulate growth and proliferation of cells, including PKCs, ERK and Akt, and their targets including NF-?B, Elk1, HO-1, and iNOS. ...

  4. The narL gene product activates the nitrate reductase operon and represses the fumarate reductase and trimethylamine N-oxide reductase operons in Escherichia coli.

    OpenAIRE

    Iuchi, S; Lin, E C

    1987-01-01

    Escherichia coli, which can utilize O2, nitrate, fumarate, or trimethylamine N-oxide (Me3NO) as terminal electron acceptor, preferentially utilizes the one with the highest redox potential. Thus O2 prevents induction of nitrate, fumarate, and Me3NO reductases, and nitrate curtails the induction of fumarate and Me3NO reductases. Under anaerobic conditions the narL gene product, in the presence of nitrate, is known to activate transcription of the narC operon, which encodes nitrate reductase. T...

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

    Energy Technology Data Exchange (ETDEWEB)

    Osmanbas, Oemer A.; Koca, Atif [Marmara University, Department of Chemical Engineering, Faculty of Engineering, 34722 Goeztepe, Istanbul (Turkey); Oezcesmeci, Ibrahim; Okur, Ali Ihsan; Guel, Ahmet [Department of Chemistry, Technical University of Istanbul, Maslak, 34469 Istanbul (Turkey)

    2008-06-01

    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 [Co{sup I}Pc{sup 2-}]{sup 1-} and/or [Co{sup I}Pc{sup 3-}]{sup 2-} species depending on the pH of the aqueous solution. (author)

  6. Functionalization of the living diatom Thalassiosira weissflogii with thiol moieties

    Science.gov (United States)

    Lang, Yvonne; Del Monte, Francisco; Collins, Liam; Rodriguez, Brian J.; Thompson, Kerry; Dockery, Peter; Finn, David P.; Pandit, Abhay

    2013-11-01

    Biomineralization processes identified within diatoms have inspired the design of synthetic silica structures in vitro using alkoxysilane precursors. Here we explore the use of the machinery within the living diatom to fabricate organo-silica constructs using a combination of alkoxysilane and organoalkoxysilane precursors. We report on the incorporation of thiol moieties into the diatom during frustule synthesis. Formation of valves within the parent diatom is monitored using fluorescence microscopy, and the modification of the chemical composition of the diatom is confirmed using energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and 29Si-nuclear magnetic resonance spectroscopy. Chemical modification is achieved without loss of the nano-scale architectural features of the frustule. Extension of this work may allow the chemistry of the diatom to be tailored during synthesis.

  7. Preparation and comparison between different thiol-protected Au nanoparticles

    International Nuclear Information System (INIS)

    We report on the synthesis of monolayer-protected gold cluster (MPCs) in aquatic phase under different conditions. Three thiols, i.e., 2-mercaptoethanesulfonic acid (MPS), 3-mercaptopropionic acid (MPA), and cystamine (CYS) have been used as the protecting monolayer. Furthermore, we studied the effect of varying the ratio between the concentrations of the protecting layer, the gold ions, and the reducing agent in the preparation solution. Comparison was based on measuring the average diameter, stability, and size distribution of the MPCs. Best results were obtained for MPS-based MPCs and that the optimum molar concentration ratio between the protecting layer, the gold ions, and the reducing agent was 1:1:2.

  8. Biliverdin reductase: a target for cancer therapy?

    Science.gov (United States)

    Gibbs, Peter E M; Miralem, Tihomir; Maines, Mahin D

    2015-01-01

    Biliverdin reductase (BVR) is a multifunctional protein that is the primary source of the potent antioxidant, bilirubin. BVR regulates activities/functions in the insulin/IGF-1/IRK/PI3K/MAPK pathways. Activation of certain kinases in these pathways is/are hallmark(s) of cancerous cells. The protein is a scaffold/bridge and intracellular transporter of kinases that regulate growth and proliferation of cells, including PKCs, ERK and Akt, and their targets including NF-?B, Elk1, HO-1, and iNOS. The scaffold and transport functions enable activated BVR to relocate from the cytosol to the nucleus or to the plasma membrane, depending on the activating stimulus. This enables the reductase to function in diverse signaling pathways. And, its expression at the transcript and protein levels are increased in human tumors and the infiltrating T-cells, monocytes and circulating lymphocytes, as well as the circulating and infiltrating macrophages. These functions suggest that the cytoprotective role of BVR may be permissive for cancer/tumor growth. In this review, we summarize the recent developments that define the pro-growth activities of BVR, particularly with respect to its input into the MAPK signaling pathway and present evidence that BVR-based peptides inhibit activation of protein kinases, including MEK, PKC?, and ERK as well as downstream targets including Elk1 and iNOS, and thus offers a credible novel approach to reduce cancer cell proliferation. PMID:26089799

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-05-15

    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.

  10. Disulfide-Linked Dinitroxides for Monitoring Cellular Thiol Redox Status through Electron Paramagnetic Resonance Spectroscopy.

    Science.gov (United States)

    Legenzov, Eric A; Sims, Stephen J; Dirda, Nathaniel D A; Rosen, Gerald M; Kao, Joseph P Y

    2015-12-01

    Intracellular thiol-disulfide redox balance is crucial to cell health, and may be a key determinant of a cancer's response to chemotherapy and radiation therapy. The ability to assess intracellular thiol-disulfide balance may thus be useful not only in predicting responsiveness of cancers to therapy, but in assessing predisposition to disease. Assays of thiols in biology have relied on colorimetry or fluorimetry, both of which require UV-visible photons, which do not penetrate the body. Low-frequency electron paramagnetic resonance imaging (EPRI) is an emerging magnetic imaging technique that uses radio waves, which penetrate the body well. Therefore, in combination with tailored imaging agents, EPRI affords the opportunity to image physiology within the body. In this study, we have prepared water-soluble and membrane-permeant disulfide-linked dinitroxides, at natural isotopic abundance, and with D,(15)N-substitution. Thiols such as glutathione cleave the disulfides, with simple bimolecular kinetics, to yield the monomeric nitroxide species, with distinctive changes in the EPR spectrum. Using the D,(15)N-substituted disulfide-dinitroxide and EPR spectroscopy, we have obtained quantitative estimates of accessible intracellular thiol in cultured human lymphocytes. Our estimates are in good agreement with published measurements. This suggests that in vivo EPRI of thiol-disulfide balance is feasible. Finally, we discuss the constraints on the design of probe molecules that would be useful for in vivo EPRI of thiol redox status. PMID:26523485

  11. Biochemical characterization of thioredoxin reductase from Babesia bovis.

    Science.gov (United States)

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

    2014-04-01

    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

  12. Profiling of thiol-containing compounds by stable isotope labeling double precursor ion scan mass spectrometry.

    Science.gov (United States)

    Liu, Ping; Huang, Yun-Qing; Cai, Wen-Jing; Yuan, Bi-Feng; Feng, Yu-Qi

    2014-10-01

    Here we developed a novel strategy of isotope labeling in combination with high-performance liquid chromatography-double precursor ion scan mass spectrometry (IL-LC-DPIS-MS) analysis for nontargeted profiling of thiol-containing compounds. In this strategy, we synthesized a pair of isotope labeling reagents (?-bromoacetonylquinolinium bromide, BQB; ?-bromoacetonylquinolinium-d7 bromide, BQB-d7) that contain a reactive group, an isotopically labeled moiety, and an ionizable group to selectively label thiol-containing compounds. The BQB and BQB-d7 labeled compounds can generate two characteristic product ions m/z 218 and 225, which contain an isotope tag and therefore were used for double precursor ion scans in mass spectrometry analysis. The peak pairs with characteristic mass differences can be readily extracted from the two precursor ion scan (PIS) spectra and assigned as potential thiol-containing candidates, which facilitates the identification of analytes. BQB and BQB-d7 labeled thiol-containing compounds can be clearly distinguished by generating two individual ion chromatograms. Thus, thiol-containing compounds from two samples labeled with different isotope reagents are ionized at the same time but recorded separately by mass spectrometry, offering good identification and accurate quantification by eliminating the MS response fluctuation and mutual interference from the two labeled samples. Using the IL-LC-DPIS-MS strategy, we profiled the thiol-containing compounds in beer and human urine, and 21 and 103 thiol candidates were discovered in beer and human urine, respectively. In addition, 9 and 17 thiol candidates in beer and human urine were successfully identified by further comparison with thiol standards or tandem mass spectrometry analysis. Taken together, the IL-LC-DPIS-MS method is demonstrated to be a promising strategy in the profiling of compounds with identical groups in metabolomics study. PMID:25222826

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-01-01

    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.

  14. Properties of the cysteine residues and the iron-sulfur cluster of the assimilatory 5'-adenylyl sulfate reductase from Enteromorpha intestinalis.

    Science.gov (United States)

    Kim, Sung-Kun; Rahman, Afroza; Conover, Richard C; Johnson, Michael K; Mason, Jeremy T; Gomes, Varinnia; Hirasawa, Masakazu; Moore, Mace L; Leustek, Thomas; Knaff, David B

    2006-04-18

    The 5'-adenylyl sulfate (APS) reductase from the marine macrophytic green alga Enteromorpha intestinalis uses reduced glutathione as the electron donor for the reduction of APS to 5'-AMP and sulfite. The E. intestinalis enzyme (EiAPR) is composed of a reductase domain and a glutaredoxin-like C-terminal domain. The enzyme contains a single [4Fe-4S] cluster as its sole prosthetic group. Three of the enzyme's eight cysteine residues (Cys166, Cys257, and Cys260) serve as ligands to the iron-sulfur cluster. Site-directed mutagenesis experiments and resonance Raman spectroscopy are consistent with the presence of a cluster in which only three of the four ligands to the cluster irons contributed by the protein are cysteine residues. Site-directed mutagenesis experiments suggest that the thiol group of Cys250, a residue found only in algal APS reductases, is not an absolute requirement for activity. The other four cysteines that do not serve as cluster ligands, all of which are required for activity, are involved in the formation of two redox-active disulfide/dithiol couples. The couple involving Cys342 and Cys345 has an E(m) value at pH 7.0 of -140 mV, and the one involving Cys165 and Cys285 has an E(m) value at pH 7.0 of -290 mV. The C-terminal portion of EiAPR, expressed separately, exhibits the cystine reductase activity characteristic of glutaredoxins. It is proposed that the Cys342-Cys345 disulfide provides the site for entry of electrons from reduced glutathione and that the Cys166-Cys285 disulfide may serve as a structural element that is essential for keeping the enzyme in the catalytically active conformation. PMID:16605269

  15. Preparation of macroporous thiol sorbents for the removal of toxic metal ion from water

    International Nuclear Information System (INIS)

    A sorbent with thiol groups was prepared from a macroporous strongly basic anion exchange resin of styrene-divinylbenzene type (Lewatit MP 500). The key step of the synthesis is nucleophilic attack of the quaternary benzyltrimethylammonium groups on the resin by sulfur containing nucleophiles. In addition to traditional application of thiol sorbents to sorption of heavy metal cations, sorption of arsenate and other toxic oxo anions was studied. The unreacted hydrophilic quaternary ammonium groups promote more complete utilization of thiols and may pre-concentrate arsenic oxo-anions in the resin via electrostatic binding. The sorbents after sorption could be regenerated by an aqueous solution of sodium (poly)sulfide. (authors)

  16. Quinoline-2-thiol Derivatives as Fluorescent Sensors for Metals, pH and HNO

    Directory of Open Access Journals (Sweden)

    Naphtali A. O’Connor

    2014-06-01

    Full Text Available A tautomeric equilibrium exists for quinoline-2-thiol and quinoline-2(1H-thione. Quantum mechanical calculations predict the thione is the major tautomer and this is confirmed by the absorption spectra. The utility of quinolone-2-thiol/quinoline-2(1H-thione as a chromophore for developing fluorescent sensors is explored. No fluorescence is observed when excited at absorption maxima, however a fluorescence increase is observed when exposed to HNO, a molecule of import as a cardiovascular therapeutic. Alkylated quinoline-2-thiol derivatives are found to be fluorescent and show a reduction in fluorescence when exposed to metals and changes in pH.

  17. Preparation and Preliminary Dielectric Characterization of Structured C60-Thiol-Ene Polymer Nanocomposites Assembled Using the Thiol-Ene Click Reaction

    Directory of Open Access Journals (Sweden)

    Hanaa M. Ahmed

    2015-11-01

    Full Text Available Fullerene-containing materials have the ability to store and release electrical energy. Therefore, fullerenes may ultimately find use in high-voltage equipment devices or as super capacitors for high electric energy storage due to this ease of manipulating their excellent dielectric properties and their high volume resistivity. A series of structured fullerene (C60 polymer nanocomposites were assembled using the thiol-ene click reaction, between alkyl thiols and allyl functionalized C60 derivatives. The resulting high-density C60-urethane-thiol-ene (C60-Thiol-Ene networks possessed excellent mechanical properties. These novel networks were characterized using standard techniques, including infrared spectroscopy (FTIR, differential scanning calorimetry (DSC, dynamic mechanical analysis (DMA, and thermal gravimetric analysis (TGA. The dielectric spectra for the prepared samples were determined over a broad frequency range at room temperature using a broadband dielectric spectrometer and a semiconductor characterization system. The changes in thermo-mechanical and electrical properties of these novel fullerene-thiol-ene composite films were measured as a function of the C60 content, and samples characterized by high dielectric permittivity and low dielectric loss were produced. In this process, variations in chemical composition of the networks were correlated to performance characteristics.

  18. 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.

  19. The orphan protein bis-?-glutamylcystine reductase joins the pyridine nucleotide-disulfide reductase family

    OpenAIRE

    Kim, Juhan; Copley, Shelley D.

    2013-01-01

    Facile DNA sequencing became possible decades after many enzymes had been purified and characterized. Consequently, there are still “orphan” enyzmes whose activity is known but the genes that encode them have not been identified. Identification of the genes encoding orphan enzymes is important because it allows correct annotation of genes of unknown function or with mis-assigned function. Bis-?-glutamylcystine reductase (GCR) is an orphan protein that was purified in 1988. This enzyme catalyz...

  20. Atmospheric reactivity of alcohols, thiols and fluoroalcohols with chlorine atoms

    Science.gov (United States)

    Garzon Ruiz, Andres

    Alcohols, thiols and fluoroalcohols are volatile organic compounds (VOCs) which are emitted to the atmosphere from both natural (vegetation, oceans, volcanoes, etc.) and anthropogenic sources (fuels, solvents, wastewater, incinerators, refrigerants, etc.). These pollutants can be eliminated from the troposphere by deposition on the terrestrial surface, direct photolysis or reaction with different tropospheric oxidants. Reactions of VOCs with tropospheric oxidants are involved in the well-known atmospheric phenomenon of photochemical smog or the production of tropospheric ozone. The oxidation of these VOCs in the troposphere is mainly initiated by reaction with OH radicals during the daytime and with NO radicals at night. However, in recent years, the oxidation by chlorine atoms (Cl) has gained great importance in the study of atmospheric reactions because they may exert some influence in the boundary layer, particularly in marine and coastal environments. In general, Cl atoms are much more reactive species than OH and NO; radicals and therefore low concentrations of Cl may compete with OH and NO3 in hydrocarbon oxidation processes. The main source of tropospheric Cl atoms is believed to be the photolysis of chlorine-containing molecules generated by heterogeneous reactions of sea salt aerosols. It has also been proposed that Cl atoms, produced in the photolysis of Cl2 emitted from industrial processes, may enhance hydrocarbon oxidation rates and ozone production in urban environments. In this work, a kinetic, theoretical and mechanistic study of the reaction of several alcohols, thiols, and fluoroalcohols with Cl atoms has been carried out. Pulsed laser photolysis-fluorescence resonance (PLP-RF) technique was used for the kinetic study as a function of temperature and pressure. An environmental chamber-Fourier transform infrared (FTIR) system was also employed in the kinetic studies. Tropospheric lifetimes of these pollutants were estimated using obtained kinetic data. Products of these reactions were determined by FTIR and derivatization with 2,4-dinitrophenylhydrazine and HPLC analysis. Finally, in order to determine the main reaction pathways a theoretical study at QCISD(T)/6-311G**//MP2(Full)(6-311C** level was performed for each reaction.

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

    Directory of Open Access Journals (Sweden)

    Simons Janet

    2011-01-01

    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.

  2. Mechanism of misonidazole-linked cytotoxicity and altered radiation response: role of cellular thiols

    International Nuclear Information System (INIS)

    Results are briefly presented of a study of the effect of different concentrations (1 mM, 5mM, and 15 mM) of misonidazole on the endogenous non-protein thiols (NPSH) of dense-cell suspensions of Ehrlich cells made hypoxic by their own metabolic consumption of oxygen. Thiol loss occurred at all drug concentrations. The effects of 15-minute incubations at different concentration of misonidazole on the thiol content of dense suspensions of hypoxic V79 lung-cells compared with Erhlich cells is also shown. There appeared to be no change in NPSH of EMT6 tumour, measured in vivo five hours following a 1 mg/kg dose of misonidazole. Removal of thiol in complete growth medium containing serum was greatest for misonidazole, followed by the nitroheterocyclic radiosensitizing compounds SR 2508 and SR 2555. (U.K.)

  3. Kinetic and Thermodynamic Aspects of Cellular Thiol-Disulfide Redox Regulation

    DEFF Research Database (Denmark)

    Jensen, Kristine Steen; Hansen, Rosa Erritzøe; Winther, Jakob R

    2009-01-01

    Regulation of intracellular thiol-disulfide redox status is an essential part of cellular homeostasis. This involves the regulation of both oxidative and reductive pathways, production of oxidant scavengers and, importantly, the ability of cells to respond to changes in the redox environment. In...... the cytosol regulatory disulfide bonds are typically formed in spite of the prevailing reducing conditions and may thereby function as redox switches. Such disulfide bonds are protected from enzymatic reduction by kinetic barriers and are thus allowed to exist long enough to elicit the signal. Factors...... that affect the rate of thiol-disulfide exchange and stability of disulfide bonds are discussed within the framework of the underlying chemical foundations. This includes the effect of thiol acidity (pKa), the local electrostatic environment, molecular strain and entropy. Even though a thiol...

  4. Studies of thiol additions of silane coupling agents by vibrational spectroscopy

    Science.gov (United States)

    Li, Ying-Sing; Vecchio, N. E.

    2007-08-01

    Raman and infrared spectroscopies have been used to determine the addition reaction of mercaptopropyltrimethoxysilane (MPTMS) to allyltrimethoxysilane (ATMS) and 7-octenyltrichlorosilane based on the vibrational intensity variation of thiol and vinyl groups in the reaction mixtures. Due to the distinct and moderate intensity of Raman bands observed in the present experiment, the identification with Raman spectroscopic method is more sensitive than that with FTIR spectroscopy. In the presence of UV radiation, thiol addition reaction has been observed in the direct mixing samples of silanes. Hybrid sol-gels prepared with the use of MPTMS and ATMS as precursors in both acidic and basic conditions have revealed the progression of thiol addition under the UV radiation exposure. UV radiation is similarly effective to induce the thiol addition in the sol-gel coated aluminum tiles. Without UV radiation, the use of free radical initiator in the sol-gel samples might also help to induce the addition reaction.

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

    Directory of Open Access Journals (Sweden)

    BradleyOlsen

    2014-05-01

    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.

  6. Redox Mediators in Visible Light Photocatalysis: Photocatalytic Radical Thiol–Ene Additions

    Science.gov (United States)

    2015-01-01

    Synthetically useful radical thiol–ene reactions can be initiated by visible light irradiation in the presence of transition metal polypyridyl photocatalysts. The success of this method relies upon the use of p-toluidine as an essential additive. Using these conditions, high-yielding thiol–ene reactions of cysteine-containing biomolecules can be accomplished using biocompatibile wavelengths of visible light, under aqueous conditions, and with the thiol component as the limiting reagent. We present evidence that p-toluidine serves as a redox mediator that is capable of catalyzing the otherwise inefficient photooxidation of thiols to the key thiyl radical intermediate. Thus, we show that co-catalytic oxidants can be important in the design of synthetic reactions involving visible light photoredox catalysis. PMID:24428433

  7. Domain Motion in Cytochrome P450 Reductase

    Science.gov (United States)

    Ellis, Jacqueline; Gutierrez, Aldo; Barsukov, Igor L.; Huang, Wei-Cheng; Grossmann, J. Günter; Roberts, Gordon C. K.

    2009-01-01

    NADPH-cytochrome P450 reductase (CPR), a diflavin reductase, plays a key role in the mammalian P450 mono-oxygenase system. In its crystal structure, the two flavins are close together, positioned for interflavin electron transfer but not for electron transfer to cytochrome P450. A number of lines of evidence suggest that domain motion is important in the action of the enzyme. We report NMR and small-angle x-ray scattering experiments addressing directly the question of domain organization in human CPR. Comparison of the 1H-15N heteronuclear single quantum correlation spectrum of CPR with that of the isolated FMN domain permitted identification of residues in the FMN domain whose environment differs in the two situations. These include several residues that are solvent-exposed in the CPR crystal structure, indicating the existence of a second conformation in which the FMN domain is involved in a different interdomain interface. Small-angle x-ray scattering experiments showed that oxidized and NADPH-reduced CPRs have different overall shapes. The scattering curve of the reduced enzyme can be adequately explained by the crystal structure, whereas analysis of the data for the oxidized enzyme indicates that it exists as a mixture of approximately equal amounts of two conformations, one consistent with the crystal structure and one a more extended structure consistent with that inferred from the NMR data. The correlation between the effects of adenosine 2′,5′-bisphosphate and NADPH on the scattering curve and their effects on the rate of interflavin electron transfer suggests that this conformational equilibrium is physiologically relevant. PMID:19858215

  8. Thioredoxin f1 and NADPH-Dependent Thioredoxin Reductase C Have Overlapping Functions in Regulating Photosynthetic Metabolism and Plant Growth in Response to Varying Light Conditions

    DEFF Research Database (Denmark)

    Thormählen, Ina; Meitzel, Tobias; Groysman, Julia; Öchsner, Alexandra Bianca; von Roepenack-Lahaye, Edda; Naranjo, Belén; Cejudo, Francisco J; Geigenberger, Peter

    2015-01-01

    Two different thiol redox systems exist in plant chloroplasts, the ferredoxin-thioredoxin (Trx) system, which depends on ferredoxin reduced by the photosynthetic electron transport chain and, thus, on light, and the NADPH-dependent Trx reductase C (NTRC) system, which relies on NADPH and thus may...... be linked to sugar metabolism in the dark. Previous studies suggested, therefore, that the two different systems may have different functions in plants. We now report that there is a previously unrecognized functional redundancy of Trx f1 and NTRC in regulating photosynthetic metabolism and growth....... In Arabidopsis (Arabidopsis thaliana) mutants, combined, but not single, deficiencies of Trx f1 and NTRC led to severe growth inhibition and perturbed light acclimation, accompanied by strong impairments of Calvin-Benson cycle activity and starch accumulation. Light activation of key enzymes of these...

  9. Can thiol compounds be used as biomarkers of aquatic ecosystem contamination by cadmium?

    OpenAIRE

    Ková?ová, Jana; Svobodová, Zde?ka

    2009-01-01

    Due to anthropogenic activities, heavy metals still represent a threat for various trophic levels. If aquatic animals are exposed to heavy metals we can obviously observe considerable toxicity. It is well known that an organism affected by cadmium (Cd) synthesize low molecular mass thiol compounds rich in cysteine (Cys), such as metallothioneins (MT) and glutathione (GSH/GSSG). The aim of this study was to summarize the effect of Cd on level of thiol compounds in aquatic organisms, and evalua...

  10. Cellular thiols in rat liver cell lines possessing different growth characteristics.

    Science.gov (United States)

    Principe, P; Riley, P A; Slater, T F

    1991-04-01

    Thiol levels were measured in three cell lines derived from rat hepatocytes with different growth rates and degrees of tumorigenicity: IAR20 having normal epithelial morphology and no tumour forming ability; IAR6.1 being a chemically-transformed malignant cell line; and IAR6.1RT7 derived from an epithelial tumour obtained after injection of IAR6.1 cells into a syngenic animal. The mean levels of GSH, GSSG, low molecular weight thiols (LMWT), macromolecular thiols (MT) and total reactive protein sulphur (TRPS), expressed as nmoles-SH mg-1 protein, were found to be 25.5, 7.5, 50.1, 114.5 and 143.6 respectively for IAR20; 37.6, 3.9, 65.4, 126.8 and 148.4 for IAR6.1; 17.2, 4.4, 52.3, 141.0 and 168.2 for IAR6.1RT7. Cultures were treated with D,L-buthionine-S,R-sulphoximine (BSO) to cause greater than 70 per cent depletion of GSH and the measurements of cellular thiols repeated. Although treatment with BSO caused a substantive decrease in the LMWT fraction, there were no major changes in macromolecular thiols or in total reactive protein sulphur. The respective mean values for LMWT, MT and TRPS (expressed as nmoles-SH mg-1 protein) were 19.4, 109.8, 136.3 for IAR20; 17.2, 119.3, 143.6 for IAR6.1; 21.6, 150.7 and 163.5 for IAR6.1RT7. It is concluded that significant differences in thiol levels exist between the three rat liver cell lines studied. However, severe acute depletion of GSH is not reflected by changes in the levels of macromolecular thiols which suggests that there is only a slow equilibrium between these two major thiol pools. PMID:1934313

  11. Thiols in Nitric Oxide Synthase-Containing Nocardia sp. Strain NRRL 5646▿

    OpenAIRE

    Lee, Sungwon; Bergeron, Hélène; Lau, Peter C. K.; Rosazza, John P. N.

    2007-01-01

    Mycothiol (MSH) [1-d-myo-inosityl-2-(N-acetyl-l-cysteinyl)amido-2-deoxy-α-d-glucopyranoside], isolated as the bimane derivative, was established to be the major thiol in Nocardia sp. strain NRRL 5646, a species most closely related to Nocardia brasiliensis strain DSM 43758T. Thiol formation and detection of MSH-dependent formaldehyde dehydrogenase activity in cell extracts are relevant to the possible modulation of nitric oxide toxicity generated by strain NRRL 5646.

  12. Mussel protein adhesion depends on interprotein thiol-mediated redox modulation.

    Science.gov (United States)

    Yu, Jing; Wei, Wei; Danner, Eric; Ashley, Rebekah K; Israelachvili, Jacob N; Waite, J Herbert

    2011-09-01

    Mussel adhesion is mediated by foot proteins (mfps) rich in a catecholic amino acid, 3,4-dihydroxyphenylalanine (dopa), capable of forming strong bidentate interactions with a variety of surfaces. A tendency toward facile auto-oxidation, however, often renders dopa unreliable for adhesion. We demonstrate that mussels limit dopa oxidation during adhesive plaque formation by imposing an acidic, reducing regime based on the thiol-rich mfp-6, which restores dopa by coupling the oxidation of thiols to dopaquinone reduction. PMID:21804534

  13. Expression, purification, crystallization and initial X-ray diffraction analysis of thiol peroxidase from Yersinia pseudotuberculosis

    International Nuclear Information System (INIS)

    Recombinant thiol peroxidase from Y. pseudotuberculosis has been purified and crystallized in three crystal forms. Thiol peroxidase is an atypical 2-Cys peroxiredoxin that reduces alkyl hydroperoxides. Wild-type and C61S mutant protein have been recombinantly expressed in Escherichia coli and purified using nickel-affinity chromatography. Initial crystallization trials yielded three crystal forms in three different space groups (P21, P64 and P212121) both in the presence and the absence of DTT

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

    OpenAIRE

    Lyumugabe Loshima, François

    2012-01-01

    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...

  15. Thiol peroxidases mediate specific genome-wide regulation of gene expression in response to hydrogen peroxide

    OpenAIRE

    Fomenko, Dmitri E; Koc, Ahmet; Agisheva, Natalia; Jacobsen, Michael; Kaya, Alaattin; Malinouski, Mikalai; Rutherford, Julian C.; Siu, Kam-Leung; Jin, Dong-Yan; Winge, Dennis R; GLADYSHEV, Vadim N.

    2011-01-01

    Hydrogen peroxide is thought to regulate cellular processes by direct oxidation of numerous cellular proteins, whereas antioxidants, most notably thiol peroxidases, are thought to reduce peroxides and inhibit H2O2 response. However, thiol peroxidases have also been implicated in activation of transcription factors and signaling. It remains unclear if these enzymes stimulate or inhibit redox regulation and whether this regulation is widespread or limited to a few cellular components. Herein, w...

  16. High catalase and low thiol levels in adult-ADHD patients

    Directory of Open Access Journals (Sweden)

    gokay alpak

    2014-01-01

    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.

  17. The Role of Thiol on Degradation of Pentaerythrityl Tetranitrate and Isosorbide Dinitrate

    OpenAIRE

    J.S. Pamudji; R.E. Kartasasmita; M.R. Suwitono; Ibrahim, S.

    2011-01-01

    Thiols such as N-acetylcystein (NAC) are used to replenish glutathione (GSH) level, with regard to their function in the maintenance of cellular reduction-oxidation balance and control of oxidative stress. Thiols play a role in the reductive metabolism of nitrates to NO, an important signaling molecule in the cardiovascular system as well as other systems throughout the body. This study aimed to evaluate the influence of NAC on decomposition of different organic nitrate esters according to it...

  18. Interactions between volatile and nonvolatile coffee components. 2. Mechanistic study focused on volatile thiols.

    Science.gov (United States)

    Charles-Bernard, Marielle; Roberts, Deborah D; Kraehenbuehl, Karin

    2005-06-01

    This study is the second of two publications that investigate the interactions between volatile and nonvolatile components in coffee brew. The purpose here was to shed some light into the chemical mechanisms responsible for the decrease of volatile thiols when in contact with coffee nonvolatiles. A mixture of volatile thiols covering a large range of physicochemical properties was monitored over time in the presence of a coffee brew model. The binding potential was estimated by SPME-GC-MS. Additives inhibiting specific reaction pathways were preincubated with the coffee brew 1 h prior to addition of the volatile compounds. Degradation kinetics of the volatile thiols were characterized by their rate constants k(obs). The effect of individual additives was shown by calculating k(rel), the relative rate constant as compared to the reference without additive. The conclusion was that thiols, mainly responsible for the "roasty" and "burnt" notes, disappear via two main chemical mechanisms. The results suggest that nucleophilic addition is the major pathway for thiol degradation. Addition occurs on oxidized species generated in the matrix in the presence of air. This mechanism prevails for aliphatic thiols (e.g., ethanethiol, methanethiol). Benzylic thiols (such as 2-furfurylthiol) can react in parallel via another pathway that is slowed in the absence of oxygen and in the presence of a radical scavenger. This points to a radical mechanism, but further work is needed to support this hypothesis. A direct correlation between thiol hydrophobicity and the magnitude of the interactions was shown as well. Therefore, weak physical interactions or hydrophobic assistance accelerating chemical reactions cannot be excluded at this point of the study. PMID:15913305

  19. Content of endogenous thiols and radioresistance of gemmating cells of Saccharomyces ellipsoideus and Saccharomyces cerevisiale yeasts

    International Nuclear Information System (INIS)

    It has been shown that gemmating cells of ''wild type'' yeasts are more radioresistant and contain more endogenous thiols, than resting cells. Gemmating cells of Saccharomyces cerevisial yeasts, carrying the mutation rad 51, as to radioresistance and content of SH groups do not differ from resting cells. The results obtained testify to a connec-- tion between increased radioresistance of the yeast gemmating cells and increased content of endogenous thiols in them

  20. Microfluidics using a thiol-acrylate resin for fluorescence-based pathogen detection assays.

    Science.gov (United States)

    Zhang, W; Tullier, M P; Patel, K; Carranza, A; Pojman, J A; Radadia, A D

    2015-11-01

    We demonstrate thiol-acrylate microfluidics prepared via soft lithography for single-step protein immobilization and fluorescence-based pathogen detection. Such microfluidics are formed via room temperature curing, and bonded without oxygen plasma. The background fluorescence of the resin was found to be similar to PDMS for several filter sets. We also show that thiol-acrylate devices are able to bond to gold-coated surfaces, which allows for integration with microfabricated sensors. PMID:26371689

  1. Aldo keto reductases 1B in endocrinology and metabolism

    OpenAIRE

    AntoineMartinez

    2012-01-01

    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 r...

  2. The role of the thiol group in protein modification with methylglyoxal

    Directory of Open Access Journals (Sweden)

    JELENA M. AĆIMOVIĆ

    2009-08-01

    Full Text Available Methylglyoxal is a highly reactive α-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.

  3. Oxidant-mediated modification of the cellular thiols is sufficient for arginase activation in cultured cells.

    Science.gov (United States)

    Iyamu, Efemwonkiekie W; Perdew, Harrison A; Woods, Gerald M

    2012-01-01

    Increased arginase activity in the vasculature has been implicated in the regulation of nitric oxide (NO) homeostasis, leading to the development of vascular disease and the promotion of tumor cell growth. Recently, we showed that cysteine, in the presence of iron, promotes arginase activity by driving the Fenton reaction. In the present report, we showed that induction of oxidative stress in erythroleukemic cells with the thiol-specific oxidant, diamide, led to an increase in arginase activity by 42% (P = 0.02; vs. control). By using specific antibodies, it was demonstrated that this increase correlated with an increase in arginase-1 levels in the cells and with corresponding decreases in glutathione and protein thiol levels. Treatment of cells with aurothiomalate (ATM), a protein thiol-complexing agent, diminished the activity of arginase and arginase-1 levels by 19.5 and 35.2%, respectively (vs. control) and significantly decreased both glutathione and protein thiol levels, further implicating the thiol redox system in the cellular activation of arginase. Furthermore, diamide significantly altered the kinetics of arginase, resulting in the doubling of its V(max) (vs. control). Our presented data demonstrate, for the first time that the intracellular arginase activation is may be enhanced in part, via a cellular thiol-mediated mechanism. PMID:21918827

  4. Oxidative stress and decreased thiol level in patients with migraine: cross-sectional study.

    Science.gov (United States)

    Eren, Yasemin; Dirik, Ebru; Ne?elio?lu, Salim; Erel, Özcan

    2015-12-01

    Although migraine is a neurological disorder known since long, its physiopathology remains unclear. Recent studies suggest that migraine is associated with oxidative stress; however, they report divergent results. The aim of the present study was to evaluate total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), and serum thiol level in migraine patients with or without aura. The study group consisted of 141 migraine patients. The control group included 70 healthy subjects. TAS, TOS, OSI were evaluated using a method developed by Erel. Serum thiol level was measured using the Hu method. No difference was found in TAS, TOS, OSI between the patients and controls. The level of thiol was significantly lower in patients than in controls. Negative correlations were detected between thiol level and Migraine Disability Assessment score in patients. Although TAS, TOS, and OSI were similar to those of the control group, serum thiol level, an important marker of antioxidant capacity, was significantly lower in migraines compared with controls, and caused more serious disability. Novel treatment approaches may be developed based on these data, and compounds containing thiol, such as alpha lipoic acid and N-acetyl cysteine, may be used in prophylaxis. PMID:25595415

  5. Tunable thiol-epoxy shape memory polymer foams

    Science.gov (United States)

    Ellson, Gregory; Di Prima, Matthew; Ware, Taylor; Tang, Xiling; Voit, Walter

    2015-05-01

    Shape memory polymers (SMPs) are uniquely suited to a number of applications due to their shape storage and recovery abilities and the wide range of available chemistries. However, many of the desired performance properties are tied to the polymer chemistry which can make optimization difficult. The use of foaming techniques is one way to tune mechanical response of an SMP without changing the polymer chemistry. In this work, a novel thiol-epoxy SMP was foamed using glass microspheres (40 and 50% by volume Q-Cel 6019), using expandable polymer microspheres (1% 930 DU 120), and by a chemical blowing agent (1% XOP-341). Each approach created SMP foam with a differing density and microstructure from the others. Thermal and thermomechanical analysis was performed to observe the behavioral difference between the foaming techniques and to confirm that the glass transition (Tg) was relatively unchanged near 50 °C while the glassy modulus varied from 19.1 to 345 MPa and the rubbery modulus varied from 0.04 to 2.2 MPa. The compressive behavior of the foams was characterized through static compression testing at different temperatures, and cyclic compression testing at Tg. Constrained shape recovery testing showed a range of peak recovery stress from 5 MPa for the syntactic Q-Cel foams to ˜0.1 MPa for the chemically blown XOP-341 foam. These results showed that multiple foaming approaches can be used with a novel SMP to vary the mechanical response independent of Tg and polymer chemistry.

  6. D-erythrulose reductase can also reduce diacetyl: further purification and characterization of D-erythrulose reductase from chicken liver.

    Science.gov (United States)

    Maeda, M; Hosomi, S; Mizoguchi, T; Nishihara, T

    1998-04-01

    We have discovered new characteristics of D-erythrulose reductase, namely, that it can catalyze reduction of not only D-erythrulose but also such diketones as diacetyl. These substrates have a common structure with two neighboring carbonyls possibly in s-cis plane structure, showing that the enzyme may rigorously distinguish between substrates and other compounds. D-Erythrulose reductase was predominantly located in the kidney and the liver of the chicken. The obtained results suggest that D-erythrulose reductase plays an important role in metabolizing alpha-dicarbonyls in animal organs, because these diketones widely occur in natural foods. PMID:9538249

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

    OpenAIRE

    Russ, Rainer; Rau, Jörg; Stolz, Andreas

    2000-01-01

    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 gene ...

  8. Crystallization and diffraction analysis of thioredoxin reductase from Streptomyces coelicolor

    International Nuclear Information System (INIS)

    Thioredoxin reductase from S. coelicolor was crystallized and diffraction data were collected to 2.4 Å resolution. Thioredoxin reductases are homodimeric flavoenzymes that catalyze the transfer of electrons from NADPH to oxidized thioredoxin substrate. Bacterial thioredoxin reductases represent a promising target for the development of new antibiotics. Recombinant thioredoxin reductase TrxB from Streptomyces coelicolor was crystallized using the hanging-drop vapour-diffusion method. X-ray diffraction data were collected from cryocooled crystals to 2.4 Å resolution using a synchrotron-radiation source. The crystals belonged to the primitive monoclinic space group P21, with unit-cell parameters a = 82.9, b = 60.6, c = 135.4 Å, α = γ = 90.0, β = 96.5°

  9. 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

  10. Thioredoxin f1 and NADPH-Dependent Thioredoxin Reductase C Have Overlapping Functions in Regulating Photosynthetic Metabolism and Plant Growth in Response to Varying Light Conditions.

    Science.gov (United States)

    Thormählen, Ina; Meitzel, Tobias; Groysman, Julia; Öchsner, Alexandra Bianca; von Roepenack-Lahaye, Edda; Naranjo, Belén; Cejudo, Francisco J; Geigenberger, Peter

    2015-11-01

    Two different thiol redox systems exist in plant chloroplasts, the ferredoxin-thioredoxin (Trx) system, which depends on ferredoxin reduced by the photosynthetic electron transport chain and, thus, on light, and the NADPH-dependent Trx reductase C (NTRC) system, which relies on NADPH and thus may be linked to sugar metabolism in the dark. Previous studies suggested, therefore, that the two different systems may have different functions in plants. We now report that there is a previously unrecognized functional redundancy of Trx f1 and NTRC in regulating photosynthetic metabolism and growth. In Arabidopsis (Arabidopsis thaliana) mutants, combined, but not single, deficiencies of Trx f1 and NTRC led to severe growth inhibition and perturbed light acclimation, accompanied by strong impairments of Calvin-Benson cycle activity and starch accumulation. Light activation of key enzymes of these pathways, fructose-1,6-bisphosphatase and ADP-glucose pyrophosphorylase, was almost completely abolished. The subsequent increase in NADPH-NADP(+) and ATP-ADP ratios led to increased nitrogen assimilation, NADP-malate dehydrogenase activation, and light vulnerability of photosystem I core proteins. In an additional approach, reporter studies show that Trx f1 and NTRC proteins are both colocalized in the same chloroplast substructure. Results provide genetic evidence that light- and NADPH-dependent thiol redox systems interact at the level of Trx f1 and NTRC to coordinately participate in the regulation of the Calvin-Benson cycle, starch metabolism, and growth in response to varying light conditions. PMID:26338951

  11. Size-controlled silver nanoparticles stabilized on thiol-functionalized MIL-53(Al) frameworks

    Science.gov (United States)

    Cheng, Xinquan; Liu, Min; Zhang, Anfeng; Hu, Shen; Song, Chunshan; Zhang, Guoliang; Guo, Xinwen

    2015-05-01

    A postsynthetic modification method was used to prepare thiol-functionalized metal-organic frameworks (MOFs) by the amidation of mercaptoacetic acid with the amine group, which is present in the frameworks of NH2-MIL-53(Al). By doing this, the thiol group has been successfully grafted on the MOF, which perfectly combined the highly developed pore structures of the MOF with the strong coordination ability of the thiol group. The resulting thiol-functionalized MIL-53(Al) showed a significantly high adsorption capacity for heavy metal ions like Ag+ (182.8 mg g-1). Even more importantly, these grafted thiol groups can be used as anchoring groups for stabilizing metal nanoparticles (NPs) with controllable sizes. Taking silver as an example, monodispersed Ag NPs encapsulated in the cages of MIL-53(Al) have been prepared by using a two-step procedure. In addition, the particle size of the Ag NPs was adjustable to some extent by controlling the initial loading amount. The average size of the smallest Ag NPs is 3.9 +/- 0.9 nm, which is hard to obtain for Ag NPs because of their strong tendency to aggregate.A postsynthetic modification method was used to prepare thiol-functionalized metal-organic frameworks (MOFs) by the amidation of mercaptoacetic acid with the amine group, which is present in the frameworks of NH2-MIL-53(Al). By doing this, the thiol group has been successfully grafted on the MOF, which perfectly combined the highly developed pore structures of the MOF with the strong coordination ability of the thiol group. The resulting thiol-functionalized MIL-53(Al) showed a significantly high adsorption capacity for heavy metal ions like Ag+ (182.8 mg g-1). Even more importantly, these grafted thiol groups can be used as anchoring groups for stabilizing metal nanoparticles (NPs) with controllable sizes. Taking silver as an example, monodispersed Ag NPs encapsulated in the cages of MIL-53(Al) have been prepared by using a two-step procedure. In addition, the particle size of the Ag NPs was adjustable to some extent by controlling the initial loading amount. The average size of the smallest Ag NPs is 3.9 +/- 0.9 nm, which is hard to obtain for Ag NPs because of their strong tendency to aggregate. Electronic supplementary information (ESI) available: Nitrogen and argon adsorption/desorption isotherms, TG and DTG curves, UV-vis diffuse reflectance spectra, temperature dependent XRD patterns, and XRD patterns. See DOI: 10.1039/c5nr01292a

  12. Escherichia coli ribonucleotide reductase expression is cell cycle regulated.

    OpenAIRE

    SUN, L.; Fuchs, J A

    1992-01-01

    The expression of the genes encoding ribonucleotide reductase in Escherichia coli was investigated in cultures synchronized by obtaining the smallest cells in a population after sucrose gradient centrifugation. Specific activity of ribonucleotide reductase and DNA initiation were found to increase in parallel, periodically as a function of the cell cycle. The expression of nrd was also determined in cells synchronized by periodic repeated doubling in a phosphate limited medium. Antibodies dir...

  13. Deletion of steroid 5?-reductase 2 gene in male pseudohermaphroditism

    OpenAIRE

    Andersson, Stefan; Berman, David M.; Jenkins, Elizabeth P.; RUSSELL, DAVID W.

    1991-01-01

    The conversion of testosterone into dihydrotestosterone by steroid 5?-reductase is a key reaction in androgen action, and is essential both for the formation of the male phenotype during embryogenesis and for androgen-mediated growth of tissues such as the prostate1,2. Single gene defects that impair this conversion lead to pseudohermaphroditism in which 46 X, Y males have male internal urogenital tracts, but female external genitalia3. We have described the isolation of a human 5?-reductase ...

  14. Expression of bacterial mercuric ion reductase in Saccharomyces cerevisiae.

    OpenAIRE

    Rensing, C; Kües, U; Stahl, U.; Nies, D H; Friedrich, B

    1992-01-01

    The gene merA coding for bacterial mercuric ion reductase was cloned under the control of the yeast promoter for alcohol dehydrogenase I in the yeast-Escherichia coli shuttle plasmid pADH040-2 and transformed into Saccharomyces cerevisiae AH22. The resulting transformant harbored stable copies of the merA-containing hybrid plasmid, displayed a fivefold increase in the MIC of mercuric chloride, and synthesized mercuric ion reductase activity.

  15. Structure, thermal and dielectric properties of LC thiol with azobenzene mesogenic group and comb-like polybutadiene-diols modified with this thiol.

    Czech Academy of Sciences Publication Activity Database

    Ilavský, Michal; Jigounov, A.; Nedbal, J.; Pissis, P.; Baldrian, Josef; Sedláková, Zde?ka

    Praha : Ústav makromolekulární chemie AS CR, v. v. i, 2007 - (Kahovec, J.). s. 61 ISBN 978-80-85009-55-2. [Microsymposium on Nanostructured Polymers and Polymer Nanocomposites /46./. 08.07.2007-12.07.2007, Praha] R&D Projects: GA AV ?R IAA4112401 Keywords : LC thiol * polybutadiene- diols Subject RIV: CD - Macromolecular Chemistry

  16. Cloning, expression and antigenicity of the L. donovani reductase.

    Science.gov (United States)

    Jensen, A T; Kemp, K; Theander, T G; Handman, E

    2001-06-01

    The protozoan parasite Leishmania undergoes a morphological and biochemical transformation from the promastigote to the amastigote form during its life cycle, which is reflected in the expression of stage-specific proteins. One of these proteins shows homology to a superfamily of reductase proteins. We have cloned the reductase gene from L donovani and have shown that it differs in only one nucleotide from the L. major homologue, resulting in one amino acid change. A cytosine (C) to guanine (G) transposition in the coding sequence leads to a nonconserved substitution of asparagine (N) for lysine (K). Only 2 of 22 plasma samples from patients with visceral leishmaniasis were found to have detectable anti-reductase antibodies and peripheral blood mononuclear cells (PBMC) from one of three individuals previously infected with visceral leishmaniasis proliferated in the presence of recombinant reductase protein. Interestingly, 6 of 10 PBMC isolated from Danish controls proliferated in the presence of the reductase protein. Intracellular IFNgamma was found in a significant percentage of cells in all the tested PBMC cultures from Danes, whereas IL4 was only found in a small proportion of cells, or not at all. The results indicate the presence of cross-reacting CD45R0 memory T-cells in individuals not exposed to Leishmania. Several previous studies have shown that T-cells from nonexposed individuals often respond to crude Leishmania antigen preparations. The present study suggests that this reactivity is partly caused by T-cells recognising L. donovani reductase. PMID:11506479

  17. INHIBITION OF TYPE I 5?-REDUCTASE BY MEDICINAL PLANT EXTRACTS

    Directory of Open Access Journals (Sweden)

    Patil Vijaya

    2011-03-01

    Full Text Available Type I 5?-reductase has been implicated in skin disorders such as acne, hirsutism and male pattern baldness and its inhibition offers a potential treatment for these disorders. The aim of this study was to investigate the inhibition of type I 5?-reductase activity by extracts from Indian medicinal plants. Plant extracts were screened and selected based on their ability to inhibit Propionibacterium acnes and Staphylococcus epidermidis. Since type I 5?-reductase metabolises testosterone to ?4-androstene-3, 17-dione, the activity of enzyme was determined using RIA for testosterone and ?4-androstene-3, 17-dione. It was found that methanolic extract of Embelia ribes was a potent inhibitor of type I 5?-reductase (IC50:100?g/mL. Extracts of Vitex negundo, Terminalia chebula, and Terminalia bellerica which also inhibited type I 5?-reductase (IC50: 200-390 ?g /mL. Therefore herbal formulation of these plant extracts may be used in the treatment of skin disorders involving type I 5?-reductase.

  18. Effect of flutamide on 5 alpha-reductases, 5 beta-reductases, and 3-hydroxysteroid dehydrogenases in rat liver.

    Science.gov (United States)

    Graef, V; Golf, S W; Tyrell, C; Fehler, M

    1987-06-01

    Flutamide (0.5 mM) decreased in vitro the activity of NADH-5 alpha-reductase (substrate testosterone) in liver homogenate of male and female rats, whereas no change of activity of NADPH-5 alpha-reductase was observed. NADH- and NADPH-5 beta-reductase activity increased only in liver of female, but not of male rats. NAD+-3 beta-hydroxysteroid dehydrogenase and NAD+-3 alpha-hydroxysteroid dehydrogenase (substrate 5 alpha-dihydro-testosterone) in liver homogenate from female rats were inhibited by flutamide (0.5 mM), whereas the activity of NADP+-3 alpha-hydroxysteroid dehydrogenase (substrate 5 alpha-dihydrotestosterone) and of NAD+-3 alpha-hydroxysteroid dehydrogenase (substrate 5 beta-dihydrotestosterone) increased in presence of flutamide. The activity of NADH- and NADPH-5 alpha-reductase decreased after flutamide administration to female rats at a dose of 5 mg per day for 7 days. PMID:3483296

  19. 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.

  20. Electrochemistry behavior of endogenous thiols on fluorine doped tin oxide electrodes

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  1. 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

  2. Regulation of cellular thiols in human lymphocytes by alpha-lipoic acid: a flow cytometric analysis.

    Science.gov (United States)

    Sen, C K; Roy, S; Han, D; Packer, L

    1997-01-01

    Modulation of cellular thiols is an effective therapeutic strategy, particularly in the treatment of AIDS. Lipoic acid, a metabolic antioxidant, functions as a redox modulator and has proven clinically beneficial effects. It is also used as a dietary supplement. We utilized the specific capabilities of N-ethylmaleimide to block total cellular thiols, phenylarsine oxide to block vicinal dithiols, and buthionine sulfoximine to deplete cellular GSH to flow cytometrically investigate how these thiol pools are influenced by exogenous lipoate treatment. Low concentrations of lipoate and its analogue lipoamide increased Jurkat cell GSH in a dose-dependent manner between 10 (25 microM for lipoamide) to 100 microM. This was also observed in mitogenically stimulated peripheral blood lymphocytes (PBL). Studies with Jurkat cells and its Wurzburg subclone showed that lipoate dependent increase in cellular GSH was similar in CD4+ and - cells. Chronic (16 week) exposure of cells to lipoate resulted in further increase of total cellular thiols, vicinal dithiols, and GSH. High concentration (2 and 5 mM) of lipoate exhibited cell shrinkage, thiol depletion, and DNA fragmentation effects. Based on similar effects of octanoic acid, the cytotoxic effects of lipoate at high concentration could be attributed to its fatty acid structure. In certain diseases such as AIDS and cancer, elevated plasma glutamate lowers cellular GSH by inhibiting cystine uptake. Low concentrations of lipoate and lipoamide were able to bypass the adverse effect of elevated extracellular glutamate. A heterogeneity in the thiol status of PBL was observed. Lipoate, lipoamide, or N-acetylcysteine corrected the deficient thiol status of cell subpopulations. Hence, the favorable effects of low concentrations of lipoate treatment appears clinically relevant. PMID:9098099

  3. The mechanism of Hg2+ toxicity in cultured human oral fibroblasts: the involvement of cellular thiols.

    Science.gov (United States)

    Liu, Y; Cotgreave, I; Atzori, L; Grafström, R C

    1992-11-30

    To study amalgam-related toxicity in a primary target cell type, human oral fibroblasts were grown in a low-serum medium containing 1.25% fetal bovine serum and exposed to Hg2+, a corrosion product of amalgam. A 1-h exposure to various concentrations of Hg2+ resulted in a dose-dependent loss of colony forming efficiency. Removal of the low-molecular-weight thiol cysteine from the medium increased the toxicity of Hg2+ almost 50-fold in comparison with complete medium or medium without fetal bovine serum. Accordingly, fetal bovine serum was not found to contain detectable levels of low-molecular-weight thiols. The levels of cellular free protein thiols were shown to be depleted Hg2+ at significantly lower concentrations of the metal ion than those required to decrease the levels of the major cellular low-molecular weight thiol glutathione. These decreases were dependent on the exposure conditions, i.e. the presence of serum and thiols, in a manner similar to the effect on colony forming efficiency. Other functions commonly related to cell viability, including the accumulation of the vital dye neutral red, the cytosolic retention of deoxyglucose and the mitochondrial reduction of tetrazolium were also inhibited by Hg2+, albeit at higher concentrations. Finally, the depletion of cellular glutathione, by pre-exposure of the cells to the glutathione synthesis inhibitor buthionine sulfoximine, somewhat increased the toxicity of Hg2+ and potentiated the depletion of protein thiols. Taken together, the toxicity of Hg2+ in human oral fibroblasts was demonstrated in several assays of which colony forming efficiency was the most sensitive, cell killing by this agent was related to its high affinity for protein thiols, whereas glutathione showed a significant, but limited, ability to protect the cells from Hg2+ toxicity. PMID:1458551

  4. The protective effects of resveratrol against changes in blood platelet thiols induced by platinum compounds.

    Science.gov (United States)

    Olas, B; Wachowicz, B; Bald, E; G?owacki, R

    2004-06-01

    Cisplatin (cis-diamminedichloroplatinum II, cisPt) is especially useful in the treatment of epithelial malignancies, however, the use of cisplatin is accompanied by several toxicities including haematological toxicity. Contrary to cisplatin, selenium-cisplatin conjugate ((NH(3))(2)Pt(SeO(3)); Se-Pt) has only a slight toxicity effect on blood platelet function. In the mechanism of platinum compounds action on platelets thiols are involved. The aim of the present studies was to examine in vitro how trans-resveratrol (trans-3,4',5-trihydroxystilbene) acts on the levels of platelet glutathione (GSH) and other thiol-containing compounds and how, as an antioxidant, protecs blood platelets against the oxidative stress caused by platinum compounds (cisPt and Se-Pt). To analyse the level of thiols in human blood platelets treated with platinum compounds and with resveratrol the classical technique HPLC has been used. Blood platelets isolated by differential centrifugation of human blood were incubated (30 min, 37 degrees C) with cisPt or Se-Pt at dose of 10 microg/ml that inhibits platelet function and with resveratrol (25 microg/ml). The obtained results indicate that platinum compounds caused in platelets a decrease of both, reduced glutathione (GSH) and free thiols of cysteine (CSH) and cysteinylglycine (CGSH). The pool of these compounds in unreduced form was increased. Platinum compounds caused the reduction of platelet protein thiols. Resveratrol (after 30 min action) at the concentration of 25 microg/ml partly reduced the platinum compounds induced decrease of platelet thiols, particularly thiols in acid-soluble fraction. PMID:15213366

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

    OpenAIRE

    Peters Joost H; van Schaik Annie; Peters Wilbert HM; Van Goor Harry

    2007-01-01

    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...

  6. Preparing mono-dispersed liquid core PDMS microcapsules from thiol–ene–epoxy-tailored flow-focusing microfluidic devices

    DEFF Research Database (Denmark)

    Mazurek, Piotr Stanislaw; Daugaard, Anders Egede; Skolimowski, Maciej; Hvilsted, Søren; Skov, Anne Ladegaard

    2015-01-01

    An applied dual-cure system based on thiol–ene and thiol–epoxy “click chemistry” reactions was proved to be an extremely effective and easy to use tool for preparing microfluidic chips, thereby allowing for precise control over material properties and providing the possibility of covalently bonding chip wafers. Different thiol–ene–epoxy-based polymer compositions were tested with the help of DSC and ATR FTIR, in order to investigate their physical and chemical properties. Water contact angles we...

  7. Methylenetetrahydrofolate Reductase Activity and Folate Metabolism

    Directory of Open Access Journals (Sweden)

    Nursen Keser

    2014-04-01

    Full Text Available Folate is a vital B vitamin which is easily water-soluble. It is a natural source which is found in the herbal and animal foods. Folate has important duties in the human metabolism, one of them is the adjustment of the level of plasma homocysteine. Reduction in MTHFR (methylenetetrahydrofolate reductase,which is in charge of the metabolism of homocysteine activity affects the level of homocysteine. Therefore MTHFR is an important enzyme in folate metabolism. Some of the mutations occurring in the MTHFR gene is a risk factor for various diseases and may be caused the hyperhomocysteinemia or the homocystinuria, and they also may lead to metabolic problems. MTHFR is effective in the important pathways such as DNA synthesis, methylation reactions and synthesis of RNA. C677T and A1298C are the most commonly occurring polymorphisms in the gene of MTHFR. The frequency of these polymorphisms show differences in the populations. MTHFR, folate distribution, metabolism of homocysteine and S-adenosylmethionine, by the MTHFR methylation the genetic defects have the potential of affecting the risk of disease in the negative or positive way.

  8. Aldose reductase, oxidative stress and diabetic mellitus

    Directory of Open Access Journals (Sweden)

    JohnHwa

    2012-05-01

    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.

  9. Functional Analysis of Free Methionine-R-sulfoxide Reductase from Saccharomyces cerevisiae*S?

    Science.gov (United States)

    Le, Dung Tien; Lee, Byung Cheon; Marino, Stefano M.; Zhang, Yan; Fomenko, Dmitri E.; Kaya, Alaattin; Hacioglu, Elise; Kwak, Geun-Hee; Koc, Ahmet; Kim, Hwa-Young; Gladyshev, Vadim N.

    2009-01-01

    Methionine sulfoxide reductases (Msrs) are oxidoreductases that catalyze thiol-dependent reduction of oxidized methionines. MsrA and MsrB are the best known Msrs that repair methionine-S-sulfoxide (Met-S-SO) and methionine-R-sulfoxide (Met-R-SO) residues in proteins, respectively. In addition, an Escherichia coli enzyme specific for free Met-R-SO, designated fRMsr, was recently discovered. In this work, we carried out comparative genomic and experimental analyses to examine occurrence, evolution, and function of fRMsr. This protein is present in single copies and two mutually exclusive subtypes in about half of prokaryotes and unicellular eukaryotes but is missing in higher plants and animals. A Saccharomyces cerevisiae fRMsr homolog was found to reduce free Met-R-SO but not free Met-S-SO or dabsyl-Met-R-SO. fRMsr was responsible for growth of yeast cells on Met-R-SO, and the double fRMsr/MsrA mutant could not grow on a mixture of methionine sulfoxides. However, in the presence of methionine, even the triple fRMsr/MsrA/MsrB mutant was viable. In addition, fRMsr deletion strain showed an increased sensitivity to oxidative stress and a decreased life span, whereas overexpression of fRMsr conferred higher resistance to oxidants. Molecular modeling and cysteine residue targeting by thioredoxin pointed to Cys101 as catalytic and Cys125 as resolving residues in yeast fRMsr. These residues as well as a third Cys, resolving Cys91, clustered in the structure, and each was required for the catalytic activity of the enzyme. The data show that fRMsr is the main enzyme responsible for the reduction of free Met-R-SO in S. cerevisiae. PMID:19049972

  10. Functional analysis of free methionine-R-sulfoxide reductase from Saccharomyces cerevisiae.

    Science.gov (United States)

    Le, Dung Tien; Lee, Byung Cheon; Marino, Stefano M; Zhang, Yan; Fomenko, Dmitri E; Kaya, Alaattin; Hacioglu, Elise; Kwak, Geun-Hee; Koc, Ahmet; Kim, Hwa-Young; Gladyshev, Vadim N

    2009-02-13

    Methionine sulfoxide reductases (Msrs) are oxidoreductases that catalyze thiol-dependent reduction of oxidized methionines. MsrA and MsrB are the best known Msrs that repair methionine-S-sulfoxide (Met-S-SO) and methionine-R-sulfoxide (Met-R-SO) residues in proteins, respectively. In addition, an Escherichia coli enzyme specific for free Met-R-SO, designated fRMsr, was recently discovered. In this work, we carried out comparative genomic and experimental analyses to examine occurrence, evolution, and function of fRMsr. This protein is present in single copies and two mutually exclusive subtypes in about half of prokaryotes and unicellular eukaryotes but is missing in higher plants and animals. A Saccharomyces cerevisiae fRMsr homolog was found to reduce free Met-R-SO but not free Met-S-SO or dabsyl-Met-R-SO. fRMsr was responsible for growth of yeast cells on Met-R-SO, and the double fRMsr/MsrA mutant could not grow on a mixture of methionine sulfoxides. However, in the presence of methionine, even the triple fRMsr/MsrA/MsrB mutant was viable. In addition, fRMsr deletion strain showed an increased sensitivity to oxidative stress and a decreased life span, whereas overexpression of fRMsr conferred higher resistance to oxidants. Molecular modeling and cysteine residue targeting by thioredoxin pointed to Cys(101) as catalytic and Cys(125) as resolving residues in yeast fRMsr. These residues as well as a third Cys, resolving Cys(91), clustered in the structure, and each was required for the catalytic activity of the enzyme. The data show that fRMsr is the main enzyme responsible for the reduction of free Met-R-SO in S. cerevisiae. PMID:19049972

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

    DEFF Research Database (Denmark)

    López-Mirabal, H Reynaldo; Thorsen, Michael; Kielland-Brandt, Morten C; Toledano, Michel B; Winther, Jakob R

    2007-01-01

    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-c......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...

  12. Thiol groups controls on arsenite binding by organic matter: new experimental and modeling evidence.

    Science.gov (United States)

    Catrouillet, Charlotte; Davranche, Mélanie; Dia, Aline; Bouhnik-Le Coz, Martine; Pédrot, Mathieu; Marsac, Rémi; Gruau, Gérard

    2015-12-15

    Although it has been suggested that several mechanisms can describe the direct binding of As(III) to organic matter (OM), more recently, the thiol functional group of humic acid (HA) was shown to be an important potential binding site for As(III). Isotherm experiments on As(III) sorption to HAs, that have either been grafted with thiol or not, were thus conducted to investigate the preferential As(III) binding sites. There was a low level of binding of As(III) to HA, which was strongly dependent on the abundance of the thiols. Experimental datasets were used to develop a new model (the modified PHREEQC-Model VI), which defines HA as a group of discrete carboxylic, phenolic and thiol sites. Protonation/deprotonation constants were determined for each group of sites (pKA=4.28±0.03; ΔpKA=2.13±0.10; pKB=7.11±0.26; ΔpKB=3.52±0.49; pKS=5.82±0.052; ΔpKS=6.12±0.12 for the carboxylic, phenolic and thiols sites, respectively) from HAs that were either grafted with thiol or not. The pKS value corresponds to that of single thiol-containing organic ligands. Two binding models were tested: the Mono model, which considered that As(III) is bound to the HA thiol site as monodentate complexes, and the Tri model, which considered that As(III) is bound as tridentate complexes. A simulation of the available literature datasets was used to validate the Mono model, with logKMS=2.91±0.04, i.e. the monodentate hypothesis. This study highlighted the importance of thiol groups in OM reactivity and, notably, determined the As(III) concentration bound to OM (considering that Fe is lacking or at least negligible) and was used to develop a model that is able to determine the As(III) concentrations bound to OM. PMID:26348657

  13. Characterization of photopolymerizable nanoparticle-(thiol-ene) polymer composites for volume holographic recording at 404 nm

    Science.gov (United States)

    Kawana, Masaru; Takahashi, Jun-ichiro; Yasui, Satoru; Tomita, Yasuo

    2014-05-01

    We report on volume holographic recording in thiol-ene based nanoparticle-polymer composites (NPCs) at a wavelength of 404 nm by using a highly coherent blue diode laser. We study the photopolymerization dynamics of two types of thiol-ene based NPCs doped with different blue-sensitive initiator/sensitizer systems (Darocur ® TPO and Irgacure ® 784/BzO2) at various doping concentrations. We also characterize a volume holographic grating recorded in these two types of thiol-ene based NPCs. Such material characterization includes the refractive index modulation, the material recording sensitivity and polymerization shrinkage. It is shown that Darocur R _ TPO provides larger refractive index modulation and higher material recording sensitivity than those with Irgacure ® 784/BzO2 but these two blue-sensitive initiator/sensitizer systems amount to meeting the requirements of the refractive index modulation and the material recording sensitivity for holographic data storage. However, it is found that shrinkage reduction of a volume grating recorded in these two types of thiol-ene based NPCs at 404 nm is not as effective as the same thiol-ene based NPC doped with Irgacure ® 784/BzO2 at 532 nm.

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

    Energy Technology Data Exchange (ETDEWEB)

    McNally, N.J.; Soranson, J.A.

    1989-05-01

    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.

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

    Science.gov (United States)

    McNally, N J; Soranson, J A

    1989-05-01

    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. PMID:2715087

  16. 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

  17. Oxidation of the albumin thiol to sulfenic acid and its implications in the intravascular compartment

    Scientific Electronic Library Online (English)

    L., Turell; S., Carballal; H., Botti; R., Radi; B., Alvarez.

    2009-04-01

    Full Text Available Human serum albumin (HSA) is the most abundant protein in the intravascular compartment. It possesses a single thiol, Cys34, which constitutes ~80% of the total thiols in plasma. This thiol is able to scavenge plasma oxidants. A central intermediate in this potential antioxidant activity of human se [...] rum albumin is sulfenic acid (HSA-SOH). Work from our laboratories has demonstrated the formation of a relatively stable sulfenic acid in albumin through complementary spectrophotometric and mass spectrometric approaches. Recently, we have been able to obtain quantitative data that allowed us to measure the rate constants of sulfenic acid reactions with molecules of analytical and biological interest. Kinetic considerations led us to conclude that the most likely fate for sulfenic acid formed in the plasma environment is the reaction with low molecular weight thiols to form mixed disulfides, a reversible modification that is actually observed in ~25% of circulating albumin. Another possible fate for sulfenic acid is further oxidation to sulfinic and sulfonic acids. These irreversible modifications are also detected in the circulation. Oxidized forms of albumin are increased in different pathophysiological conditions and sulfenic acid lies in a mechanistic junction, relating oxidizing species to final thiol oxidation products.

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

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

    Science.gov (United States)

    Hoang, Van Duc; Phuong Dang, Tuyet; Khieu Dinh, Quang; Phu Nguyen, Huu; Vu, Anh Tuan

    2010-09-01

    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.

  20. 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

  1. Thiol peroxidases mediate specific genome-wide regulation of gene expression in response to hydrogen peroxide.

    Science.gov (United States)

    Fomenko, Dmitri E; Koc, Ahmet; Agisheva, Natalia; Jacobsen, Michael; Kaya, Alaattin; Malinouski, Mikalai; Rutherford, Julian C; Siu, Kam-Leung; Jin, Dong-Yan; Winge, Dennis R; Gladyshev, Vadim N

    2011-02-15

    Hydrogen peroxide is thought to regulate cellular processes by direct oxidation of numerous cellular proteins, whereas antioxidants, most notably thiol peroxidases, are thought to reduce peroxides and inhibit H(2)O(2) response. However, thiol peroxidases have also been implicated in activation of transcription factors and signaling. It remains unclear if these enzymes stimulate or inhibit redox regulation and whether this regulation is widespread or limited to a few cellular components. Herein, we found that Saccharomyces cerevisiae cells lacking all eight thiol peroxidases were viable and withstood redox stresses. They transcriptionally responded to various redox treatments, but were unable to activate and repress gene expression in response to H(2)O(2). Further studies involving redox transcription factors suggested that thiol peroxidases are major regulators of global gene expression in response to H(2)O(2). The data suggest that thiol peroxidases sense and transfer oxidative signals to the signaling proteins and regulate transcription, whereas a direct interaction between H(2)O(2) and other cellular proteins plays a secondary role. PMID:21282621

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  3. Radiosensitization, thiol oxidation, and inhibition of DNA repair by SR 4077

    International Nuclear Information System (INIS)

    The mechanism of radiosensitization by diazenedicarboxylic acid bis(N),N-piperidide (SR 4077), a less toxic analog of diamide, was studied using Chinese hamster ovary cells. SR 4077 gave an average SER of 1.58 for postirradiation incubations of 0.5, 1.0, or 2.0 h. Intracellular GSH and protein thiols decreased rapidly following drug addition and GSSG increased. The GSH/GSSG ratio shifted to 1/1.6 after SR 4077 addition but returned to greater than 10/1 between 0.5 and 1.0 h. After 4 h, total intracellular GSH was only 58% of pretreatment level and extracellular GSSG increased. Protein thiols decreased to 18% of pretreatment values, recovered most rapidly between 0.5 and 1.0 h, and reached 87% of pretreatment level after 4 h. A decrease in DNA single-strand break repair as measured by alkaline filter elution rate over 0.5 h was seen, and the initial rate of repair was slower than in cells not treated with SR 4077. DNA double-strand break repair as measured by neutral filter elution rate was delayed during the first hour after irradiation when cells were treated with SR 4077. The times for maximum radiosensitization, GSH and protein thiol oxidation and recovery, and DNA strand break repair kinetics were closely linked. We propose that a protein thiol(s) required in repair processes was reversibly oxidized during SR 4077 treatment

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

    Directory of Open Access Journals (Sweden)

    Peters Joost H

    2007-02-01

    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.

  5. Characterization of volume holographic recording in photopolymerizable nanoparticle-(thiol-ene) polymer composites at 404 nm

    Science.gov (United States)

    Kawana, Masaru; Takahashi, Jun-ichiro; Yasui, Satoru; Tomita, Yasuo

    2015-02-01

    We report on the photopolymerization dynamics and the volume holographic recording properties of a thiol-ene based nanoparticle-polymer composite (NPC) doped with a blue-sensitive photoinitiator, Darocur® TPO, by using a highly coherent blue diode laser operating at a wavelength of 404 nm. Our study indicates that volume gratings recorded in the NPC amount to meeting the material requirements of refractive index modulation and material recording sensitivity for holographic data storage media. It is also found that polymerization shrinkage of recorded NPC gratings is higher than that of the same thiol-ene based NPC with a green (523 nm)-sensitive photoinitiator, Irgacure® 784/BzO2. We attribute such a difference in shrinkage to the photopolymerization dynamics at these recording wavelengths. We show that this shrinkage increase at 404 nm can be mitigated to some extent by controlling the thiol-ene stoichiometry in the NPC.

  6. Immobilization of Ag-deposited Au nanoprisms by thiol-coupling and oil-coating methods

    Science.gov (United States)

    Noda, Yuta; Hayakawa, Tomokatsu

    2016-01-01

    We have demonstrated the immobilization of Ag-deposited Au (Au@Ag) nanoprisms on glass substrates by two different methods: self-assembly on a thiol-modified glass (thiol-coupling method) and evaporation of the Au@Ag nanoprism colloidal solution in silicone oil (oil-coating method). In the thiol-coupling method, the Au@Ag nanoprisms were well dispersed and accumulated on the substrates as single or stacked layers. On the other hand, the oil-coating method allowed Au@Ag nanoprisms to accumulate as multilayers without excessive agglomeration. The multilayers of Au@Ag nanoprisms were subjected to surface-enhanced Raman scattering (SERS), and a very low concentration (2.1 × 10‑5 M) of rhodamine 6G molecules was sensitively detected.

  7. Enhancement in the Glass Transition Temperature in Latent Thiol-Epoxy Click Cured Thermosets

    Directory of Open Access Journals (Sweden)

    Dailyn Guzmán

    2015-04-01

    Full Text Available Tri and tetrafunctional thiol were used as curing agent for diglycidyl ether of bisphenol A (DGEBA catalyzed by a commercially available amine precursor, LC-80. Triglycidyl isocianurate (TGIC was added in different proportions to the mixture to increase rigidity and glass transition temperature (Tg. The cooperative effect of increasing functionality of thiol and the presence of TGIC in the formulation leads to an increased Tg without affecting thermal stability. The kinetics of the curing of mixtures was studied by calorimetry under isothermal and non-isothermal conditions. The latent characteristics of the formulations containing amine precursors were investigated by rheometry and calorimetry. The increase in the functionality of the thiol produces a slight decrease in the storage lifetime of the mixture. The materials obtained with tetrathiol as curing agent showed the highest values of Young’s modulus and Tg.

  8. Aqueous Synthesis of Peptide Thioesters from Amino Acids and a Thiol Using 1,1?-Carbonyldiimidazole

    Science.gov (United States)

    Weber, Arthur L.

    2005-10-01

    A new method was developed for the synthesis of peptide thioesters from free amino acids and thiols in water. This one-pot simple method involves two steps: (1) activation in water of an amino acid presumably as its N-carboxyanhydride (NCA) using 1,1?-carbonyldiimidazole (CDI), and (2) subsequent condensation of the activated amino acid-NCA in the presence of a thiol. With this method citrulline peptide thioesters containing up to 10 amino acid residues were prepared in a single reaction. This aqueous synthetic method provides a simple way to prepare peptide thioesters for studies of peptide replication involving ligation of peptide thioesters on peptide templates. The relevance of peptide replication to the origin-of-life process is supported by previous studies showing that amino acid thioesters (peptide thioester precursors) can be synthesized under prebiotic conditions by reaction of small sugars with ammonia and a thiol.

  9. Competitive reduction of perferrylmyoglobin radicals by protein thiols and plant phenols.

    Science.gov (United States)

    Jongberg, Sisse; Lund, Marianne N; Skibsted, Leif H; Davies, Michael J

    2014-11-19

    Radical transfer from perferrylmyoglobin to other target species (myofibrillar proteins, MPI) and bovine serum albumin (BSA), extracts from green tea (GTE), maté (ME), and rosemary (RE), and three phenolic compounds, catechin, caffeic acid, and carnosic acid) was investigated by electron paramagnetic resonance (EPR) spectroscopy to determine the concentrations of plant extracts required to protect against protein oxidation. Blocking of MPI thiol groups by N-ethylmaleimide was found to reduce the rate of reaction of MPI with perferrylmyoglobin radicals, signifying the importance of protein thiols as radical scavengers. GTE had the highest phenolic content of the three extracts and was most effective as a radical scavenger. IC50 values indicated that the molar ratio between phenols in plant extract and MPI thiols needs to be >15 in order to obtain efficient protection against protein-to-protein radical transfer in meat. Caffeic acid was found most effective among the plant phenols. PMID:25343706

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

    International Nuclear Information System (INIS)

    Highlights: • Diamond surfaces were functionalized with organic molecules using a novel approach. • Used biomimicry to select a molecule to bind NO, similar to the human body. • Molecular orbital theory predicted the molecule-analyte oxidation behavior. • A thiol moiety was attached to an amine surface tether on the diamond surface. • XPS analysis verified each surface functionalization step. - Abstract: 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

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  12. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez-Legorreta, Teresa [Departamento de Recursos del Mar, CINVESTAV-IPN, Unidad Merida, Apdo. Postal 73-Cordemex, Merida, Yucatan 97310 (Mexico); Mendoza-Cozatl, David; Moreno-Sanchez, Rafael [Departamento de Bioquimica, Instituto Nacional de Cardiologia, Mexico D.F. 14080 (Mexico); Gold-Bouchot, Gerardo [Departamento de Recursos del Mar, CINVESTAV-IPN, Unidad Merida, Apdo. Postal 73-Cordemex, Merida, Yucatan 97310 (Mexico)], E-mail: gold@mda.cinvestav.mx

    2008-01-20

    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{sub 2} concentrations (0, 30, 50 and 70 {mu}M). 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sund, James B., E-mail: jim@jamessund.com [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Causey, Corey P. [Departments of Chemistry and Biochemistry, Duke University, Durham, NC (United States); Wolter, Scott D. [Department of Physics, Elon University, Elon, NC 27244 (United States); Parker, Charles B., E-mail: charles.parker@duke.edu [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Stoner, Brian R. [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Research Triangle Institute (RTI) International, Research Triangle Park, NC (United States); Toone, Eric J. [Departments of Chemistry and Biochemistry, Duke University, Durham, NC (United States); Glass, Jeffrey T. [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States)

    2014-05-01

    Highlights: • Diamond surfaces were functionalized with organic molecules using a novel approach. • Used biomimicry to select a molecule to bind NO, similar to the human body. • Molecular orbital theory predicted the molecule-analyte oxidation behavior. • A thiol moiety was attached to an amine surface tether on the diamond surface. • XPS analysis verified each surface functionalization step. - Abstract: 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.

  15. Characterization of a sulfite reductase from Desulfovibrio vulgaris

    International Nuclear Information System (INIS)

    A low-molecular-weight (M/sub r/ = 27,200) sulfite reductase from Desulfovibrio vulgaris was studied with Moessbauer, EPR, and chemical techniques. This sulfite reductase was found to contain one siroheme and one [4Fe-4S] cluster. As purified, the siroheme is low-spin ferric (S = 1/2) which exhibits characteristic EPR resonances at g = 2.44, 2.36, and 1.77. At 150 K, the observed Moessbauer parameters, ?E/sub Q/ = 2.49 +/- 0.02 mm/s and ? = 0.31 +/- 0.02 mm/s, for the siroheme are typical for low-spin ferric complexes. The [4Fe-4S] cluster is in the 2+ state. The Moessbauer parameters, ?E/sub Q/ = 0.95 +/- 0.02 mm/s and ? = 0.38 +/- 0.02 mm/s, for the cluster are almost identical to those observed for the [4Fe-4S]2+ cluster in the hemoprotein subunit of the sulfite reductase from Escherichia coli. Similar to the hemoprotein subunit of E. coli sulfite reductase, low-temperature Moessbauer spectra of D. vulgaris sulfite reductase recorded with weak and strong applied fields also show evidence for an exchange-coupled siroheme-[4Fe-4S] unit. 31 references, 4 figures, 1 table

  16. The role of biliverdin reductase in colorectal cancer

    International Nuclear Information System (INIS)

    In recent years, the effects of biliverdin and bilirubin have been studied extensively, and an inhibitory effect of bile pigments in cancer progression has been proposed. In this study we focused on the effects of biliverdin reductase, the enzyme that converts biliverdin to bilirubin, in colorectal cancer. For in vitro experiments we used a human colorectal carcinoma cell line and transfected it with an expression construct of shRNA specific for biliverdin reductase, to create cells with stable knock-down of enzyme expression. Cell proliferation was analyzed using the CASY model TT cell counting device. Western blot protein analysis was performed to study intracellular signaling cascades. Samples of human colorectal cancer were analyzed using immunohistochemistry. We were able to confirm the antiproliferative effects of bile pigments on cancer cells in vitro. However, this effect was attenuated in biliverdin reductase knock down cells. ERK and Akt activation seen under biliverdin and bilirubin treatment was also reduced in biliverdin reductase deficient cells. Immunohistochemical analysis of tumor samples from patients with colorectal cancer showed elevated biliverdin reductase levels. High enzyme expression was associated with lower overall and disease free patient survival. We conclude that BVR is required for bile pigment mediated effects regarding cancer cell proliferation and modulation of intracellular signaling cascades. The role of BVR overexpression in vivo and its exact influence on cancer progression and patient survival need to be further investigated. (author)

  17. The Arabidopsis thaliana sulfiredoxin is a plastidic cysteine-sulfinic acid reductase involved in the photooxidative stress response.

    Science.gov (United States)

    Rey, Pascal; Bécuwe, Noëlle; Barrault, Marie-Bénédicte; Rumeau, Dominique; Havaux, Michel; Biteau, Benoît; Toledano, Michel B

    2007-02-01

    The 2-cysteine peroxiredoxins (2-Cys-Prxs) are antioxidants that reduce peroxides through a thiol-based mechanism. During catalysis, these ubiquitous enzymes are occasionally inactivated by the substrate-dependent oxidation of the catalytic cysteine to the sulfinic acid (-SO2H) form, and are reactivated by reduction by sulfiredoxin (Srx), an enzyme recently identified in yeast and in mammal cells. In plants, 2-Cys-Prxs constitute the most abundant Prxs and are located in chloroplasts. Here we have characterized the unique Srx gene in Arabidopsis thaliana (AtSrx) from a functional point of view, and analyzed the phenotype of two AtSrx knockout (AtSrx-) mutant lines. AtSrx is a chloroplastic enzyme displaying sulfinic acid reductase activity, as shown by the ability of the recombinant AtSrx to reduce the overoxidized 2-Cys-Prx form in vitro, and by the accumulation of the overoxidized Prx in mutant lines lacking Srx in vivo. Furthermore, AtSrx mutants exhibit an increased tolerance to photooxidative stress generated by high light combined with low temperature. These data establish that, as in yeast and in mammals, plant 2-Cys-Prxs are subject to substrate-mediated inactivation reversed by Srx, and suggest that the 2-Cys-Prx redox status and sulfiredoxin are parts of a signaling mechanism participating in plant responses to oxidative stress. PMID:17217469

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

    Energy Technology Data Exchange (ETDEWEB)

    Droux, M.; Miginiac-Maslow, M.; Jacquot, J.P.; Gadal, P.; Crawford, N.A.; Kosower, N.S.; Buchanan, B.B.

    1987-07-01

    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 (/sup 14/C)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.

  19. Stretching of BDT-gold molecular junctions: Thiol or thiolate termination?

    KAUST Repository

    Souza, Amaury De Melo

    2014-01-01

    It is often assumed that the hydrogen atoms in the thiol groups of a benzene-1,4-dithiol dissociate when Au-benzene-1,4-dithiol-Au junctions are formed. We demonstrate, by stability and transport property calculations, that this assumption cannot be made. We show that the dissociative adsorption of methanethiol and benzene-1,4-dithiol molecules on a flat Au(111) surface is energetically unfavorable and that the activation barrier for this reaction is as high as 1 eV. For the molecule in the junction, our results show, for all electrode geometries studied, that the thiol junctions are energetically more stable than their thiolate counterparts. Due to the fact that density functional theory (DFT) within the local density approximation (LDA) underestimates the energy difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital by several electron-volts, and that it does not capture the renormalization of the energy levels due to the image charge effect, the conductance of the Au-benzene-1,4-dithiol-Au junctions is overestimated. After taking into account corrections due to image charge effects by means of constrained-DFT calculations and electrostatic classical models, we apply a scissor operator to correct the DFT energy level positions, and calculate the transport properties of the thiol and thiolate molecular junctions as a function of the electrode separation. For the thiol junctions, we show that the conductance decreases as the electrode separation increases, whereas the opposite trend is found for the thiolate junctions. Both behaviors have been observed in experiments, therefore pointing to the possible coexistence of both thiol and thiolate junctions. Moreover, the corrected conductance values, for both thiol and thiolate, are up to two orders of magnitude smaller than those calculated with DFT-LDA. This brings the theoretical results in quantitatively good agreement with experimental data.

  20. Radiosensitization by oxygen and radioprotection by Thiols: Experimental evaluation of a theoretical model

    International Nuclear Information System (INIS)

    The general purpose of the investigations presented in this thesis was a further elucidation of the mechanism by which oxygen sensitizes cells and tissues to radiation. Recently, the 'X model' was put forward as an explanation for the oxygen effect. The model postulated that oxygen and cellular thiols compete for radiation induced target radicals, oxygen fixing and thiols repairing the radiation damage, the latter, however, with the reservation that only a certain proportion of the damage is reparable. The study summarized in the thesis was performed with the aim of testing the validity of the model by a comparative analysis of the theoretical predictions with experimental observations. Human fibroblasts and Chinese hamster cells in culture were used as experimental cell material. The thiol level of the cells varied either due to a genetic damage, or to treatment with buthionine sulphoximine (BSO) which decreased the thiol content, or to treatment with dithiothreitol or N-acetylcysteine which increased it. Exposures to radiation were made in severe hypoxia or in the presence of oxygen in varying concentrations. The yield of DNA breaks, expressing the effect of the initial radical reactions and, in a few cases, clonogenic survival, expressing also the effect of additional superimposed enzymatic repair processes, were chosen as measure of the radiation response. Four different predictions of the X model were tested experimentally. In all cases a good general agreement between the pattern of the radiation response, predicted by the X model, and the experimental observations was found. In contrast, major differences were noted between the experimental data and the prediction of an alternative model in which, as opposed to the X model, radiation induced radical damage is assumed to be reparable by thiols in full. The validity of the X model, indicated by these investigations suggests that, in general two types of damage are produced by radiation, only one of which can be repaired by thiols. (au)

  1. [Stabilization of heavy metals in municipal solid waste incineration fly ash with the thiol collectors].

    Science.gov (United States)

    Zhang, Hai-Jun; Yu, Ying; Ni, Yu-Wen; Li, Yong-Xian; Wang, Shu-Qiu; Chen, Ji-Ping

    2007-08-01

    Three kinds of thiol collector, sodium diethyldithiocarbamate (DDTC), potassium ethyl xanthate (EXT) and ammonium dibutyl dithiphosphate (DDTP), were adopted to stabilize heavy metals from municipal solid waste incineration fly ash (MSWI fly ash). The concentration of the three thiol collectors was all 62.5 micromol x g(-1) fly ash. Scanning electron microscopic observation shows that, the thiol collectors evenly cover on the surface of fly ash which makes the angles of mineral crystal ambiguous. Furthermore, the leaching characteristics of heavy metal Cu, Pb, Cd, Cr and Zn in fly ash were analyzed according to the toxicity characteristic leaching procedure (TCLP) and the horizontal vibration method. Comparing with Na2S, thiol collectors present better stabilization effects for Cu and Pb when the extractant is 0.1 mol x L(-1) acetic acid. DDTC stabilizes almost all the acid-extractable Cu, and DDTP stabilizes 69.2% of acid-extractable Pb. When extracted by water, the stabilization ratios of the five heavy metals by DDTC, EXT and DDTP are 72.6%, 73.5% and 76.8%, respectively, significantly higher than that by Na2S (52.4%). The affinity preference of the thiol collectors for the five heavy metals is generally in the order of Cu > Pb > Cr > Cd > Zn. Also, over 60% of the collector participates in the chelating reaction with the acid-extractable heavy metals. Under neutral and alkali condition (pH > 6) the chelators of heavy metal-thiol collector are steady, but partly dissolved under acid condition (pH < 6). Evidently, in order to obtain better heavy metal stabilization effects, it is important to maintain the acid buffer capacity of stabilized fly ash at a higher level. PMID:17926431

  2. Mercury impairment of mouse thymocyte survival in vitro: involvement of cellular thiols.

    Science.gov (United States)

    Mondal, Tapan K; Li, Daming; Swami, Kamal; Dean, J Kenneth; Hauer, Charles; Lawrence, David A

    2005-04-01

    Heavy metals are well known to be able to induce immunotoxicity, but comparative metal studies related to apoptosis have not been conducted. In the present study, the effects of arsenic, cadmium, gold, lead, manganese, and mercury on thymocytes from BALB/c mice were analyzed. Thymic cells were cultured for 3-24 h in vitro in the absence or presence of metal, and markers of apoptosis or cell death, including annexin V binding, DNA loss/oligonucleosomal fragmentation, 7-amino-actinomycin D uptake (loss of impermeance), changes of the mitochondrial membrane potential (JC-1 fluorescence), and Western analysis of cellular thiols, were assayed. Mercury (Hg) was the only metal shown to be consistently toxic with the dose and times utilized. Cadmium (Cd) was the only other metal tested that also produced some significant level of DNA loss; however, the induction of apoptosis by Cd was not as consistent as that observed with Hg. When Hg was added with 2-mercaptoethanol (2-ME), Hg produced greater toxicity. Endogenous DNA synthesis by thymocytes was immediately inhibited by Hg and Hg + 2-ME. The Hg + 2-ME-induced apoptosis appeared to be associated with altered levels of cellular thiols, in that glutathione (GSH) depletion was significant in comparison to the non-metal control and Hg alone. The increased Hg-induced toxicity in the presence of 2-ME likely was due to the ability of 2-ME to enhance (10- to 20-fold) the cellular uptake of Hg. Western analysis with biotin maleimide demonstrated that Hg + 2-ME and to a lesser extent the positive control dexamethasone eliminated many reactive thiols; the major thiol-reactive protein still reactive with the maleimide probe had an approximate Molecular Mass of 45 kD. Surprisingly, Hg alone enhanced the expression of this thiol-expressing protein, which by Mass Spectrometry (MS)/MS analysis was shown to be beta-actin. Hg also produced the appearance of yet to be identified new proteins. Based on the results with Hg + 2-ME, it is suggested that numerous protein thiols participate in maintenance of cell survival and their loss is associated with apoptosis. The increased expression of new thiol-reactive proteins or thiol-reactive proteins with altered electrophoretic profiles needs to be further investigated. However, the enhanced toxicity attributed to Hg + 2-ME suggests that increased intracellular oxidative stress, observed as increased depletion of GSH, is responsible for the accelerated cell death. PMID:15805047

  3. Patterned Hydrophilization of Nanoporous 1,2?PB by Thiol?ene Photochemistry

    DEFF Research Database (Denmark)

    Berthold, Anton; Sagar, Kaushal Shashikant; Ndoni, Sokol

    2011-01-01

    We present an efficient method for functionalizing the large polymer–air interface of a gyroid nanoporous polymer. The hydrophilicity of nanoporous cross?linked 1,2?polybutadiene is tuned by thiol?ene photo?grafting of mercaptosuccinic acid or sodium 2?mercaptoethanesulfonate. The reaction is monitored by FT?IR, UV–Vis, contact angle, and gravimetry. Overall quantum yields are calculated for the two thiol?ene “click” reactions in nano?confinement, neatly revealing their chain?like nature. Top–do...

  4. Mechanism of misonidazole linked cytotoxicity and altered radiation response: role of cellular thiols

    International Nuclear Information System (INIS)

    The effectiveness of misonidazole as a hypoxic radiosensitizer of mammalian cells is increased by prolonged exposure of hypoxic cells to the drug. It was found that drug intermediates might react with endogenous non-protein thiols (NPSH). These thiols function to protect the cell against deleterious intermediates that could otherwise attach and modify critical macromolecules such as DNA, RNA and protein. This paper presents studies on the effects of misonidazole, as well as newly developed hypoxic cell radiosensitizers, in an attempt to (1) identify the alterations in the NPSH, and (2) elucidate the role that the changes in NPSH play in cytotoxic and radiosensitizing effects of nitro compounds

  5. Thiol groups controls on arsenite binding by organic matter: New experimental and modeling evidence

    OpenAIRE

    Catrouillet, Charlotte; Davranche, Mélanie; Dia, Aline; Bouhnik-Le Coz, Martine; Pédrot, Mathieu; Marsac, Rémi; Gruau, Gérard

    2015-01-01

    Although it has been suggested that several mechanisms can describe the direct binding ofAs(III) to organic matter (OM), more recently, the thiol functional group of humic acid (HA)was shown to be an important potential binding site for As(III). Isotherm experiments onAs(III) sorption to HAs, that have either been grafted with thiol or not, were thus conducted toinvestigate the preferential As(III) binding sites. There was a low level of binding of As(III) toHA, which was strongly dependent o...

  6. Reversible electron transfer reaction between polyaniline and thiol/disulfide couples

    Energy Technology Data Exchange (ETDEWEB)

    Tatsuma, Tetsu; Matsui, Hiroshi; Shouji, Eiichi; Oyama, Noboru [Tokyo Univ. of Agriculture and Technology (Japan)

    1996-08-15

    Reversible electron transfer was observed between polyaniline (PAn) and thiol/disulfide couples of 2,5-dimercapto-1,3,4-thiadazole (DMcT), 2-mercapto-5-methyl-1,3,4-thiadiazole, 2-mercaptopyridine, and thiophenol. Thus, PAn can be used as a molecular current collector for those insulating organosulfur compounds, which are promising high-capacity energy storage materials. Among those couples, DMc Tex hibits the fastest reversible electron transfer. Electron transfer from other aromatic and aliphatic thiols to oxidized PAn is also observed. Effects of protons on the reactions and reaction kinetics are discussed. 10 refs., 10 figs., 1 tab.

  7. Effect of kidney damage on the mobilisation of mercury by thiol-complexing agents

    OpenAIRE

    Tandon, S.K.; Magos, L.

    1980-01-01

    ABSTRACT Mobilisation of mercury by thiol-complexing agents is the accepted treatment for chronic mercury intoxication. The success of such treatment is judged by the urinary excretion of mercury which might be modified by existing kidney damage caused either by the mercury itself or by other factors. In the present work the ability of three thiol-complexing agents, D-penicillamine, N-acetyl-D, L-penicillamine, and 2,3-dimercaptosuccinic acid (DMSA) to remove mercury from a damaged kidney and...

  8. POTENTIOMETRIC RESPONSE OF A GRAPHITE ELECTRODE MODIFIED WITH COBALT PHTHALOCYANINE FOR THIOLS AND DISULFIDES

    OpenAIRE

    Zagal, José H.; JAIME J.H. HENRIQUEZ

    2000-01-01

    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 ...

  9. Diamond surface functionalization with biomimicry - Amine surface tether and thiol moiety for electrochemical sensors

    Science.gov (United States)

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

    2014-05-01

    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.

  10. Synthesis of Biobased Polyols by Thiol-Ene Coupling from Vegetable Oils

    OpenAIRE

    Desroches, Myriam; Caillol, Sylvain; Lapinte, Vincent; Auvergne, Rémi; Boutevin, Bernard

    2011-01-01

    A model study of the radical addition of 2-mercaptoethanol onto oleic acid was performed under mild conditions (generation of radicals under UV light at room temperature without any photoinitiator). To evaluate the efficiency and the robustness of thiol-ene reaction, experimental parameters were varied, such as the irradiation intensity (ranging from 0.5 to 15.0 W/cm2), the thiol/double bond ratio (ranging from 1.2/1 to 5.0/1), the solvent/double bond ratio (ranging from 0/1 to 500/1), and th...

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

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Hvilsted, Søren

    2009-01-01

    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...... 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...

  12. Metal triflate-mediated coupling of allylgermanes with thiols: a facile route to thiogermanes.

    Science.gov (United States)

    Kuci?ski, K; Pawlu?, P; Hreczycho, G

    2015-06-28

    A novel coupling reaction of thiols with (2-methylallyl)germanes catalyzed by metal triflates has been developed. This reaction provides a direct and efficient method to afford thiogermanes and opens a valuable and general synthetic route for the Ge-S cross-coupling with the elimination of isobutylene as a single by-product. Scandium(iii) triflate demonstrates the highest catalytic activity among the tested triflates. All reactions were carried out under extremely mild conditions to give thiogermanes in excellent yields. This Ge-S coupling reaction shows high generality for the variety of thiols. PMID:26006777

  13. Therapeutic efficacy of green tea polyphenols on cellular thiols in 4-Nitroquinoline 1-oxide-induced oral carcinogenesis.

    Science.gov (United States)

    Srinivasan, Periasamy; Sabitha, Kuruvimalai Ekambaram; Shyamaladevi, Chennam Srinivasulu

    2004-10-15

    In cancer, a high flux of oxidants not only depletes the cellular thiols, but damages the whole cell as well. Epidemiological studies suggest green tea may mitigate cancers in human and animal models for which several mechanisms have been proposed. In the present investigation, the levels of cellular thiols such as reduced glutathione (GSH), oxidised glutathione (GSSG), protein thiols (PSH), total thiols, lipid peroxidation product conjugated dienes and the activity of gamma glutamyl transferase (GGT) were assessed in tongue and oral cavity. In 4-Nitroquinoline 1-oxide- (4-NQO) induced rats, there was a decrease in the levels of GSH, PSH and total thiols and an increase in the levels of GSSG, conjugated dienes and the activity of GGT. On supplementation of green tea polyphenols (GTP) for 30 days (200 mg/kg) for the oral cancer-induced rats, there was a moderate increase in the levels of GSH, PSH and total thiols and a decrease in the levels of GSSG, conjugated dienes and the activity of GGT. Thus, GTP reduces the oxidant production thereby maintains the endogenous low molecular weight cellular thiols in oral cancer-induced rats. From the results, it can be concluded that GTP supplementation enhances the cellular thiol status thereby mitigate oral cancer. PMID:15501430

  14. Rapid and simple preparation of thiol-ene emulsion-templated monoliths and their application as enzymatic microreactors

    DEFF Research Database (Denmark)

    Lafleur, Josiane P; Senkbeil, Silja; Novotny, Jakub; Nys, Gwenaël; Bøgelund, Nanna; Rand, Kasper D; Foret, Frantisek; Kutter, Jörg P

    2015-01-01

    electron microscopy showed that the methanol-based emulsion templating process resulted in a network of highly interconnected and regular thiol-ene beads anchored solidly inside thiol-ene microchannels. Surface area measurements indicate that the monoliths are macroporous, with no or little micro- or...

  15. Intramolecular electron transfer in Pseudomonas aeruginosa cd(1) nitrite reductase

    DEFF Research Database (Denmark)

    Farver, Ole; Brunori, Maurizio; Cutruzzolà, Francesca; Rinaldo, Serena; Wherland, Scot; Pecht, Israel

    2009-01-01

    The cd(1) nitrite reductases, which catalyze the reduction of nitrite to nitric oxide, are homodimers of 60 kDa subunits, each containing one heme-c and one heme-d(1). Heme-c is the electron entry site, whereas heme-d(1) constitutes the catalytic center. The 3D structure of Pseudomonas aeruginosa...... controlling this internal ET step. In this study we have investigated the internal ET in the wild-type and His369Ala mutant of P. aeruginosa nitrite reductases and have observed similar cooperativity to that of the Pseudomonas stutzeri enzyme. Heme-c was initially reduced, in an essentially diffusion...... nitrite reductase has been determined in both fully oxidized and reduced states. Intramolecular electron transfer (ET), between c and d(1) hemes is an essential step in the catalytic cycle. In earlier studies of the Pseudomonas stutzeri enzyme, we observed that a marked negative cooperativity is...

  16. Pseudo-constitutivity of nitrate-responsive genes in nitrate reductase mutants

    OpenAIRE

    Schinko, Thorsten; Gallmetzer, Andreas; Amillis, Sotiris; Strauss, Joseph

    2013-01-01

    ? Constitutive phenotype in nitrate-reductase mutants depends on nitrate transporters. ? Intracellular nitrate derives from media components. ? Internal nitrate generation from nitric oxide. ? Nitrate transporters are functional in cells lacking nitrate reductase.

  17. Aldo keto reductases 1B in endocrinology and metabolism

    Directory of Open Access Journals (Sweden)

    AntoineMartinez

    2012-08-01

    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.

  18. Effects of chain-transferring thiol functionalities on the performance of nanoparticle-polymer composite volume gratings.

    Science.gov (United States)

    Guo, Jinxin; Fujii, Ryuta; Ono, Takanori; Klepp, Jürgen; Pruner, Christian; Fally, Martin; Tomita, Yasuo

    2014-12-01

    We report influences of varying functionalities of thiols as chain transfer agents on the spatial frequency response, polymerization shrinkage, and thermal stability of a volume grating recorded in a photopolymerizable ZrO₂ nanoparticle-polymer composite film. It is shown that a substantial increase in the saturated refractive index modulation is realized at high spatial frequencies by doping with multifunctional thiols. Moreover, the incorporation of multifunctional thiols considerably suppresses polymerization shrinkage of recorded volume gratings and thermal changes in refractive index and film thickness as compared with the case of mono-thiol. These results indicate that multifunctional thiols provide effective control of the properties of nanoparticle-polymer composite volume gratings for various applications in light and neutron optics. PMID:25490667

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

    DEFF Research Database (Denmark)

    Lokanathan, Arcot R.

    2011-01-01

    , 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......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...... 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...

  20. Two transcripts encode rat cytochrome b5 reductase.

    OpenAIRE

    Pietrini, G.; Carrera, P.; Borgese, N

    1988-01-01

    A cDNA expression library in lambda gt11 was screened with affinity-purified polyclonal anti-rat cytochrome b5 reductase antibodies. One positive clone out of 450,000 clones was isolated and found to be incomplete. This clone was used to rescreen the library, and a second, overlapping clone that contained the entire coding sequence was isolated. RNA gel blots showed that the two overlapping clones contained approximately 90% of the reductase mRNA sequence. Sequencing data showed (i) that rat ...

  1. Spirulina ferredoxin-NADP+ reductase. The complete amino acid sequence.

    Science.gov (United States)

    Yao, Y; Tamura, T; Wada, K; Matsubara, H; Kodo, K

    1984-05-01

    The amino acid sequence of ferredoxin-NADP+ oxidoreductase [EC 1.18.1.2, FNR] from Spirulina sp., a blue-green alga, was determined. Spirulina ferredoxin-NADP+ oxidoreductase was composed of 294 amino acid residues and the molecular weight of the holoenzyme was 34,135. An apparent homology of the amino(N)-terminal region was found between ferredoxin-NADP+ reductases from Spirulina and spinach. We also found some sequence similarities in human erythrocyte glutathione reductase and p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens, both of which are NADPH-dependent FAD enzymes. PMID:6430889

  2. Intramolecular electron transfer in Pseudomonas aeruginosa cd(1) nitrite reductase

    DEFF Research Database (Denmark)

    Farver, Ole; Brunori, Maurizio; Cutruzzolà, Francesca; Rinaldo, Serena; Wherland, Scot; Pecht, Israel

    2009-01-01

    The cd(1) nitrite reductases, which catalyze the reduction of nitrite to nitric oxide, are homodimers of 60 kDa subunits, each containing one heme-c and one heme-d(1). Heme-c is the electron entry site, whereas heme-d(1) constitutes the catalytic center. The 3D structure of Pseudomonas aeruginosa nitrite reductase has been determined in both fully oxidized and reduced states. Intramolecular electron transfer (ET), between c and d(1) hemes is an essential step in the catalytic cycle. In earlier s...

  3. Repression of nitrate reductase activity and loss of antigenically detectable protein in Neurospora crassa.

    OpenAIRE

    Amy, N K; Garrett, R H

    1980-01-01

    Experiments were performed to determine whether conditions which cause the rapid loss of nitrate reductase activity in Neurospora crassa mycelia were accompanied by the loss of antigenically detectable nitrate reductase protein. When mycelia with nitrate reductase activity were transferred to ammonia media, there was a rapid loss in the reduced nicotinamide adenine dinucleotide-nitrate reductase activity plus the parallel loss of the reduced nicotinamide adenine dinucleotide-diaphorase and th...

  4. Purification and Characterization of a Novel Erythrose Reductase from Candida magnoliae

    OpenAIRE

    Lee, Jung-Kul; Kim, Sang-Yong; Ryu, Yeon-Woo; Seo, Jin-Ho; Kim, Jung-Hoe

    2003-01-01

    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...

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

    OpenAIRE

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

    1987-01-01

    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...

  6. Reactivities of some thiol collectors and their interactions with Ag (+1) ion by molecular modeling

    International Nuclear Information System (INIS)

    The most commonly used collectors for sulfide minerals in the mining industry are the thiol collectors for the recovery of these minerals from their associated gangues by froth flotation. For this reason, a great deal of attention has been paid to understand the attachment mechanism of thiol collectors to metal sulfide surfaces. The density functional theory (DFT) calculations at the B3LYP/3-21G* and B3LYP/6-31++G** levels were employed to propose the flotation responses of these thiol collectors, namely, diethyl dithiocarbamate, ethyl dithiocarbamate, ethyl dithiocarbonate, ethyl trithiocarbonate and ethyl dithiophosphate ions, and to study the interaction energies of these collectors with Ag (+1) ion in connection to acanthite (Ag2S) mineral. The calculated interaction energies, ?E, were interpreted in terms of the highest occupied molecular orbital (HOMO) energies of the isolated collector ions. The results show that the HOMOs are strongly localized to the sulfur atoms and the HOMO energies can be used as a reactivity descriptor for the flotation ability of the thiol collectors. Using the HOMO and ?E energies, the reactivity order of the collectors is found to be (C2H5)2NCS2- > C2H5NHCS2- > C2H5OCS2- > C2H5SCS2- > (C2H5O)(OH)PS2-. The theoretically obtained results are in good agreement with the experimental data reported

  7. 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 103dm3mol-1s-1). The so-formed planar ether radical is 'repaired' by the thiol (k = 6 x 108dm3mol-1s-1) thereby regenerating a cis-or trans-2,5-dimethyltetrahydrofuran molecule. In this reaction a thiyl radical is reproduced. Thus trans-2,5-Me2 THF from cis-2,5-Me2THF 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-Me2THF concentration of 1 x 10-2mol dm-3 using DTT as the thiol, G(cis-2,5-Me2THF) = 160 has been found. The chain reaction is very sensitive to impurities and also to disulphides such as those radiolytically formed. 2,5-Me2THF 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)

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

    Science.gov (United States)

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

    2013-08-01

    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

  9. Topography of Escherichia coli ribosomal proteins. The order of reactivity of thiol groups*

    Science.gov (United States)

    Bakardjieva, Anastasia; Crichton, Robert R.

    1974-01-01

    1. 30S and 50S ribosomal subunits of Escherichia coli were treated with N-[2,3-14C]-ethylmaleimide and iodo[14C]acetamide. 2. The proteins in the native subunits which reacted with the reagents were S1,‡ S2, S12, S13, S18, S21, L2, L5, L6, L10, L11, L15, L17, L20, L26+28 and L27. 3. Several proteins, such as S1, S12, S14, S18, L2, L6, L10, L11 and either L26 or 28, had thiol groups in an oxidized form and reacted to a greater extent after reduction with ?-mercaptoethanol or dithiothreitol. 4. The total number of thiol groups in 30S and 50S subunits was determined as 16–17 and 26–27 respectively. The total number of thiol groups in each ribosomal protein was also determined. 5. The reaction of 30S and 50S subunits with iodoacetamide under several different conditions established the order of reactivity of thiol groups. PMID:4618476

  10. Quantitative interpretation of the transition voltages in gold-poly(phenylene) thiol-gold molecular junctions

    KAUST Repository

    Wu, Kunlin

    2013-01-01

    The transition voltage of three different asymmetric Au/poly(phenylene) thiol/Au molecular junctions in which the central molecule is either benzene thiol, biphenyl thiol, or terphenyl thiol is investigated by first-principles quantum transport simulations. For all the junctions, the calculated transition voltage at positive polarity is in quantitative agreement with the experimental values and shows weak dependence on alterations of the Au-phenyl contact. When compared to the strong coupling at the Au-S contact, which dominates the alignment of various molecular orbitals with respect to the electrode Fermi level, the coupling at the Au-phenyl contact produces only a weak perturbation. Therefore, variations of the Au-phenyl contact can only have a minor influence on the transition voltage. These findings not only provide an explanation to the uniformity in the transition voltages found for π-conjugated molecules measured with different experimental methods, but also demonstrate the advantage of transition voltage spectroscopy as a tool for determining the positions of molecular levels in molecular devices. © 2013 AIP Publishing LLC.

  11. Aroma extraction dilution analysis of Sauternes wines. Key role of polyfunctional thiols.

    Science.gov (United States)

    Bailly, Sabine; Jerkovic, Vesna; Marchand-Brynaert, Jacqueline; Collin, Sonia

    2006-09-20

    The aim of the present work was to investigate Sauternes wine aromas. In all wine extracts, polyfunctional thiols were revealed to have a huge impact. A very strong bacon-petroleum odor emerged at RI = 845 from a CP-Sil5-CB column. Two thiols proved to participate in this perception: 3-methyl-3-sulfanylbutanal and 2-methylfuran-3-thiol. A strong synergetic effect was evidenced between the two compounds. The former, never mentioned before in wines, and not found in the musts of this study, is most probably synthesized during fermentation. 3-Methylbut-2-ene-1-thiol, 3-sulfanylpropyl acetate, 3-sulfanylhexan-1-ol, and 3-sulfanylheptanal also contribute to the global aromas of Sauternes wines. Among other key odorants, the presence of a varietal aroma (alpha-terpineol), sotolon, fermentation alcohols (3-methylbutan-1-ol and 2-phenylethanol) and esters (ethyl butyrate, ethyl hexanoate, and ethyl isovalerate), carbonyls (trans-non-2-enal and beta-damascenone), and wood flavors (guaiacol, vanillin, eugenol, beta-methyl-gamma-octalactone, and Furaneol) is worth stressing. PMID:16968087

  12. Quantitative interpretation of the transition voltages in gold-poly(phenylene) thiol-gold molecular junctions

    International Nuclear Information System (INIS)

    The transition voltage of three different asymmetric Au/poly(phenylene) thiol/Au molecular junctions in which the central molecule is either benzene thiol, biphenyl thiol, or terphenyl thiol is investigated by first-principles quantum transport simulations. For all the junctions, the calculated transition voltage at positive polarity is in quantitative agreement with the experimental values and shows weak dependence on alterations of the Au-phenyl contact. When compared to the strong coupling at the Au-S contact, which dominates the alignment of various molecular orbitals with respect to the electrode Fermi level, the coupling at the Au-phenyl contact produces only a weak perturbation. Therefore, variations of the Au-phenyl contact can only have a minor influence on the transition voltage. These findings not only provide an explanation to the uniformity in the transition voltages found for ?-conjugated molecules measured with different experimental methods, but also demonstrate the advantage of transition voltage spectroscopy as a tool for determining the positions of molecular levels in molecular devices

  13. Characterization of the membrane-associated thiol oxidase activity of rat small-intestinal epithelium.

    Science.gov (United States)

    Lash, L H; Jones, D P

    1983-08-01

    The membrane-associated thiol oxidase of rat small-intestinal epithelium was studied to determine its subcellular localization and properties. The brush-border and basal-lateral regions of the plasma membrane were isolated by density-gradient centrifugation in Percoll. The intestinal oxidase was localized by use of marker enzymes to the basal-lateral region of the plasma membrane. The reaction stoichiometry and activity with a variety of low-molecular-weight thiols were determined. The oxidase activity was inhibited by EDTA, bathocuproine disulfonate, N-ethylmaleimide, and H2O2; this suggests that copper and a sulfhydryl group are involved in catalysis. Oxidase activity in EDTA-treated basal-lateral membranes was reconstituted with CuSO4, which suggests the requirement for copper. These results show that the intestinal oxidase is very similar to the renal oxidase, and because of the subcellular localization and accessibility to extracellular thiols, suggests that the intestinal oxidase may be important in the maintenance of the plasma thiol:disulfide ratio. PMID:6614926

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

    Directory of Open Access Journals (Sweden)

    Mark R. Geier

    2013-08-01

    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.

  15. GC/MS DETERMINATION OF 1-P-MENTHEN-8-THIOL IN GRAPEFRUIT JUICE

    Science.gov (United States)

    P-menthene-8-thiol is a very potent aroma compound found in grapefruit juice. It currently is not measured commercially because it is present in only trace quantities and due to the fact that it requires an expensive specialized detector. However, in this report, it is shown that utilizing a stand...

  16. Synthesis and Microstructural Investigations of Organometallic Pd(II) Thiol-Gold Nanoparticles Hybrids

    Science.gov (United States)

    Vitale, Floriana; Vitaliano, Rosa; Battocchio, Chiara; Fratoddi, Ilaria; Giannini, Cinzia; Piscopiello, Emanuela; Guagliardi, Antonella; Cervellino, Antonio; Polzonetti, Giovanni; Russo, Maria Vittoria; Tapfer, Leander

    2008-11-01

    In this work the synthesis and characterization of gold nanoparticles functionalized by a novel thiol-organometallic complex containing Pd(II) centers is presented. Pd(II) thiol, trans, trans-[dithiolate-dibis(tributylphosphine)dipalladium(II)-4,4'-diethynylbiphenyl] was synthesized and linked to Au nanoparticles by the chemical reduction of a metal salt precursor. The new hybrid made of organometallic Pd(II) thiol-gold nanoparticles, shows through a single S bridge a direct link between Pd(II) and Au nanoparticles. The size-control of the Au nanoparticles (diameter range 2-10 nm) was achieved by choosing the suitable AuCl4 -/thiol molar ratio. The size, strain, shape, and crystalline structure of these functionalized nanoparticles were determined by a full-pattern X-ray powder diffraction analysis, high-resolution TEM, and X-ray photoelectron spectroscopy. Photoluminescence spectroscopy measurements of the hybrid system show emission peaks at 418 and 440 nm. The hybrid was exposed to gaseous NO x with the aim to evaluate the suitability for applications in sensor devices; XPS measurements permitted to ascertain and investigate the hybrid -gas interaction.

  17. Thiol-based antioxidants elicit mitochondrial oxidation via respiratory complex III.

    Science.gov (United States)

    Kolossov, Vladimir L; Beaudoin, Jessica N; Ponnuraj, Nagendraprabhu; DiLiberto, Stephen J; Hanafin, William P; Kenis, Paul J A; Gaskins, H Rex

    2015-07-15

    Excessive oxidation is widely accepted as a precursor to deleterious cellular function. On the other hand, an awareness of the role of reductive stress as a similar pathological insult is emerging. Here we report early dynamic changes in compartmentalized glutathione (GSH) redox potentials in living cells in response to exogenously supplied thiol-based antioxidants. Noninvasive monitoring of intracellular thiol-disulfide exchange via a genetically encoded biosensor targeted to cytosol and mitochondria revealed unexpectedly rapid oxidation of the mitochondrial matrix in response to GSH ethyl ester or N-acetyl-l-cysteine. Oxidation of the probe occurred within seconds in a concentration-dependent manner and was attenuated with the membrane-permeable ROS scavenger tiron. In contrast, the cytosolic sensor did not respond to similar treatments. Surprisingly, the immediate mitochondrial oxidation was not abrogated by depolarization of mitochondrial membrane potential or inhibition of mitochondrial GSH uptake. After detection of elevated levels of mitochondrial ROS, we systematically inhibited multisubunit protein complexes of the mitochondrial respiratory chain and determined that respiratory complex III is a downstream target of thiol-based compounds. Disabling complex III with myxothiazol completely blocked matrix oxidation induced with GSH ethyl ester or N-acetyl-l-cysteine. Our findings provide new evidence of a functional link between exogenous thiol-containing antioxidants and mitochondrial respiration. PMID:25994788

  18. Coumarins give misleading absorbance with Ellman's reagent suggestive of thiol conjugates.

    Science.gov (United States)

    Berlich, Maik; Menge, Sieglinde; Bruns, Ina; Schmidt, Juergen; Schneider, Bernd; Krauss, Gerd-Joachim

    2002-03-01

    In the course of a screening for phytochelatins in cadmium-exposed bryophytes in the terrestrial mosses Polytrichum formosum and Atrichum undulatum we detected compounds with absorption properties and retention times similar to phytochelatins when applying the commonly used standard method RP-HPLC and post-column derivatization with thiol-specific DTNB (Ellman) reagent. Moreover, as with phytochelatins known in other plants, the concentrations of these compounds increased slightly after Cd stress. The concentration of the precursor glutathione (gamma-ECG), however, increased in the presence of Cd. In order to verify the identity of these putative phytochelatins we performed LC-ESI-MS analyses as well as 1H NMR on extracts from P. formosum and A. undulatum. Spectroscopic investigations indicated that the detected compounds were neither phytochelatins nor other thiol compounds. From the results of HPLC-1H NMR and mass spectrometry we concluded that at least one of these substances was a coumarin, probably a 5,8-dihydroxy-7-methoxycoumarin-5-beta-glucopyranoside, which has already been described for A. undulatum and P. formosum. The results of our investigations prove that under the basic pH conditions essential for the Ellman test for thiol compounds, coumarins show comparable UV/VIS absorption properties. Therefore, a positive post-column Ellman reaction cannot unambiguously prove the presence of thiol-containing compounds in plants. PMID:11996355

  19. Thiol peroxidase deficiency leads to increased mutational load and decreased fitness in Saccharomyces cerevisiae.

    Science.gov (United States)

    Kaya, Alaattin; Lobanov, Alexei V; Gerashchenko, Maxim V; Koren, Amnon; Fomenko, Dmitri E; Koc, Ahmet; Gladyshev, Vadim N

    2014-11-01

    Thiol peroxidases are critical enzymes in the redox control of cellular processes that function by reducing low levels of hydroperoxides and regulating redox signaling. These proteins were also shown to regulate genome stability, but how their dysfunction affects the actual mutations in the genome is not known. Saccharomyces cerevisiae has eight thiol peroxidases of glutathione peroxidase and peroxiredoxin families, and the mutant lacking all these genes (?8) is viable. In this study, we employed two independent ?8 isolates to analyze the genome-wide mutation spectrum that results from deficiency in these enzymes. Deletion of these genes was accompanied by a dramatic increase in point mutations, many of which clustered in close proximity and scattered throughout the genome, suggesting strong mutational bias. We further subjected multiple lines of wild-type and ?8 cells to long-term mutation accumulation, followed by genome sequencing and phenotypic characterization. ?8 lines showed a significant increase in nonrecurrent point mutations and indels. The original ?8 cells exhibited reduced growth rate and decreased life span, which were further reduced in all ?8 mutation accumulation lines. Although the mutation spectrum of the two independent isolates was different, similar patterns of gene expression were observed, suggesting the direct contribution of thiol peroxidases to the observed phenotypes. Expression of a single thiol peroxidase could partially restore the growth phenotype of ?8 cells. This study shows how deficiency in nonessential, yet critical and conserved oxidoreductase function, leads to increased mutational load and decreased fitness. PMID:25173844

  20. Enantiospecific synthesis of [2.2]paracyclophane-4-thiol and derivatives

    Directory of Open Access Journals (Sweden)

    Gareth J. Rowlands

    2009-03-01

    Full Text Available This paper describes a simple route to enantiomerically enriched [2.2]paracyclophane-4-thiol via the stereospecific introduction of a chiral sulfoxide to the [2.2]paracyclophane skeleton. The first synthesis of an enantiomerically enriched planar chiral benzothiazole is also reported.

  1. Synthesis and Microstructural Investigations of Organometallic Pd(II Thiol-Gold Nanoparticles Hybrids

    Directory of Open Access Journals (Sweden)

    Cervellino Antonio

    2008-01-01

    Full Text Available Abstract In this work the synthesis and characterization of gold nanoparticles functionalized by a novel thiol-organometallic complex containing Pd(II centers is presented. Pd(II thiol,trans, trans-[dithiolate-dibis(tributylphosphinedipalladium(II-4,4?-diethynylbiphenyl] was synthesized and linked to Au nanoparticles by the chemical reduction of a metal salt precursor. The new hybrid made of organometallic Pd(II thiol-gold nanoparticles, shows through a single S bridge a direct link between Pd(II and Au nanoparticles. The size-control of the Au nanoparticles (diameter range 2–10 nm was achieved by choosing the suitable AuCl4 ?/thiol molar ratio. The size, strain, shape, and crystalline structure of these functionalized nanoparticles were determined by a full-pattern X-ray powder diffraction analysis, high-resolution TEM, and X-ray photoelectron spectroscopy. Photoluminescence spectroscopy measurements of the hybrid system show emission peaks at 418 and 440 nm. The hybrid was exposed to gaseous NO x with the aim to evaluate the suitability for applications in sensor devices; XPS measurements permitted to ascertain and investigate the hybrid –gas interaction.

  2. Tritium isotopic exchange between hydrogen sulfide and methyl thiol in gas phase

    International Nuclear Information System (INIS)

    The tritium exchange reaction between HTS and CH3SH was carried out. The degree of tritium exchange was estimated. Its dependence on time of reaction is shown. The dependence of the rate of exchange on the concentrations of methyl thiol and hydrogen sulfide is presented too. (Z.R.)

  3. Chemo-enzymatic synthesis of ?-terpineol thioacetate and thiol derivatives and their use as flavouring compounds.

    Science.gov (United States)

    Bel-Rhlid, Rachid; Fleury Rey, Yvette; Welti, Dieter; Fumeaux, René; Moine, Deborah

    2015-01-01

    Reaction of (R,S)-?-terpineol with thioacetic acid in food-grade n-hexane resulted into two ?-terpineol thioacetate derivatives with the same molecular weight. After 5?h of reaction time, (R,S)-?-terpineol was completely transformed and the mixture analysed by different chromatographic techniques. The aroma character of the ?-terpineol thioacetates was described as exotic, sweet, blackcurrant, roasted and sulphury. Of eight lipases and two esterases assayed, only non-immobilized pig liver esterase (PLE) hydrolysed ?-terpineol thioacetates into the corresponding ?-terpineol thiols. When reactions were performed in 0.2?m phosphate buffer at pH?8.0 and 30?°C with non-immobilized PLE, ?-terpineol thiols were produced in an optimal yield of 88% after 24?h of reaction time. The aroma character of ?-terpineol thiols was described as green, exotic and fresh grapefruit. Flavouring powders were prepared by freeze-drying the ?-terpineol thioacetates and ?-terpineol thiols in the presence of maltodextrine. Preliminary applications showed that these flavouring preparations could be used to improve the flavour quality of lighter cooked notes and tropical fruit aromas. PMID:25400090

  4. Influence cadmium ions on the synthesis of thiol compounds for flax

    Directory of Open Access Journals (Sweden)

    Olga Krystofova

    2010-12-01

    Full Text Available Evaluation of the effectiveness of phytoremediation technologies isvery difficult. One way to quickly and inexpensively identifyphytoremediation potential of plants is found easily detectablemarker. In our study, we examined the content of thiol compoundsin plants, of Flax effects of various concentrations of cadmium ions.

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

    DEFF Research Database (Denmark)

    Lafleur, Josiane P.; Kwapiszewski, Radoslaw; Jensen, Thomas Glasdam; Kutter, Jörg Peter

    2013-01-01

    ! 17 SH nm"2. Biotin alkyne was patterned directly inside thiol–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...

  6. Metabolism of the Synthetic Progestogen Norethynodrel by Human Ketosteroid Reductases of the Aldo-Keto Reductase Superfamily

    OpenAIRE

    Jin, Yi; Duan, Ling; Chen, Mo; Penning, Trevor M.; Kloosterboer, Helenius J.

    2011-01-01

    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 and ...

  7. Highly sensitive simultaneous detection of cultured cellular thiols by laser induced fluorescence-capillary electrophoresis.

    Science.gov (United States)

    Zinellu, Angelo; Sotgia, Salvatore; Posadino, Anna M; Pasciu, Valeria; Perino, Maria G; Tadolini, Bruna; Deiana, Luca; Carru, Ciriaco

    2005-03-01

    We have recently described a new method to determine physiological thiols, in which the quantification of plasma homocysteine, cysteine, cysteinylglycine, glutathione, and glutamylcysteine was achieved after derivatization with 5-iodoacetamidofluorescein. Samples were separated and measured by capillary electrophoresis with laser-induced fluorescence in an uncoated fused-silica capillary, using a phosphate/borate run buffer and the organic base N-Methyl-D-glucamine as effective electrolyte addictive to obtain a baseline peak separation. In this paper, we propose an improvement of our method useful for the analysis of the intracellular thiols in different cultured cells. In particular, we studied run buffer and injection conditions in order to increase the sensitivity of the assay and we found that, by incrementing two times the injected volume and using the water plug before the sample injection, the sensitivity of our previous method was increased by about ten times. To maintain a good resolution between peaks, particularly between homocysteine and the internal standard d-penicillamine, we lengthened the run time by incrementing the concentration of the electrolyte buffer and the organic base d-glucamine and by decreasing the cartridge temperature from 40 to 25 degrees C. After these changes in electrophoretical parameters, cellular thiols were baseline-resolved in less than 14 min instead of 9 min as in our previous method, but the limit of quantification is increased from 50 to 1 nmol/L. This new procedure allows also to measure the intracellular thiols commonly found at low concentration, such as cysteinylglycine, glutamylcysteine, and homocysteine. The new analytical method performance was assessed by measuring the intracellular thiols in three different cell lines, i.e., HUVEC, ECV304, and R1 stem cells. PMID:15706569

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

    Directory of Open Access Journals (Sweden)

    Amrit Kaur Bansal

    2009-01-01

    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.

  9. Isolation and expression of the Pneumocystis carinii dihydrofolate reductase gene

    DEFF Research Database (Denmark)

    Edman, J C; Edman, U; Cao, Mi-Mi; Lundgren, B; Kovacs, J A; Santi, D V

    1989-01-01

    Pneumocystis carinii dihydrofolate reductase (DHFR; 5,6,7,8-tetrahydrofolate: NADP+ oxidoreductase, EC 1.5.1.3) cDNA sequences have been isolated by their ability to confer trimethoprim resistance to Escherichia coli. Consistent with the recent conclusion that P. carinii is a member of the Fungi...

  10. Thioredoxin and NADP-thioredoxin reductase from cultured carrot cells

    Science.gov (United States)

    Johnson, T. C.; Cao, R. Q.; Kung, J. E.; Buchanan, B. B.

    1987-01-01

    Dark-grown carrot (Daucus carota L.) tissue cultures were found to contain both protein components of the NADP/thioredoxin system--NADP-thioredoxin reductase and the thioredoxin characteristic of heterotrophic systems, thioredoxin h. Thioredoxin h was purified to apparent homogeneity and, like typical bacterial counterparts, was a 12-kdalton (kDa) acidic protein capable of activating chloroplast NADP-malate dehydrogenase (EC 1.1.1.82) more effectively than fructose-1,6-bisphosphatase (EC 3.1.3.11). NADP-thioredoxin reductase (EC 1.6.4.5) was partially purified and found to be an arsenite-sensitive enzyme composed of two 34-kDa subunits. Carrot NADP-thioredoxin reductase resembled more closely its counterpart from bacteria rather than animal cells in acceptor (thioredoxin) specificity. Upon greening of the cells, the content of NADP-thioredoxin-reductase activity, and, to a lesser extent, thioredoxin h decreased. The results confirm the presence of a heterotrophic-type thioredoxin system in plant cells and raise the question of its physiological function.

  11. The Kinetics and Inhibition of the Enzyme Methemoglobin Reductase

    Science.gov (United States)

    Splittgerber, A. G.; And Others

    1975-01-01

    Describes an undergraduate biochemistry experiment which involves the preparation and kinetics of an oxidation-reduction enzyme system, methemoglobin reductase. A crude enzyme extract is prepared and assayed spectrophotometrically. The enzyme system obeys Michaelis-Menton kinetics with respect to both substrate and the NADH cofactor. (MLH)

  12. Fatty Acyl-CoA Reductase 1 Deficiency

    Directory of Open Access Journals (Sweden)

    Charles N Swisher

    2015-01-01

    Full Text Available Investigators from Erlangen, Germany; Calgary, CA; and Kafranbel, Syria, identified mutations in the gene, fatty acyl-CoA reductase 1 (FAR1 deficiency, adding to three other genes involved in plasmalogen biosynthesis, in two families affected by severe intellectual disability, early-onset epilepsy, microcephaly, congenital cataracts, growth retardation, and spasticity.

  13. The arsenic hyperaccumulating Pteris vittata expresses two arsenate reductases

    Science.gov (United States)

    Cesaro, Patrizia; Cattaneo, Chiara; Bona, Elisa; Berta, Graziella; Cavaletto, Maria

    2015-09-01

    Enzymatic reduction of arsenate to arsenite is the first known step in arsenate metabolism in all organisms. Although the presence of one mRNA arsenate reductase (PvACR2) has been characterized in gametophytes of P. vittata, no arsenate reductase protein has been directly observed in this arsenic hyperaccumulating fern, yet. In order to assess the possible presence of arsenate reductase in P. vittata, two recombinant proteins, ACR2-His6 and Trx-His6-S-Pv2.5-8 were prepared in Escherichia coli, purified and used to produce polyclonal antibodies. The presence of these two enzymes was evaluated by qRT-PCR, immunoblotting and direct MS analysis. Enzymatic activity was detected in crude extracts. For the first time we detected and identified two arsenate reductase proteins (PvACR2 and Pv2.5-8) in sporophytes and gametophytes of P. vittata. Despite an increase of the mRNA levels for both proteins in roots, no difference was observed at the protein level after arsenic treatment. Overall, our data demonstrate the constitutive protein expression of PvACR2 and Pv2.5-8 in P. vittata tissues and propose their specific role in the complex metabolic network of arsenic reduction.

  14. Differential molecular response of monodehydroascorbate reductase and glutathione reductase by nitration and S-nitrosylation.

    Science.gov (United States)

    Begara-Morales, Juan C; Sánchez-Calvo, Beatriz; Chaki, Mounira; Mata-Pérez, Capilla; Valderrama, Raquel; Padilla, María N; López-Jaramillo, Javier; Luque, Francisco; Corpas, Francisco J; Barroso, Juan B

    2015-09-01

    The ascorbate-glutathione cycle is a metabolic pathway that detoxifies hydrogen peroxide and involves enzymatic and non-enzymatic antioxidants. Proteomic studies have shown that some enzymes in this cycle such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), and glutathione reductase (GR) are potential targets for post-translational modifications (PMTs) mediated by nitric oxide-derived molecules. Using purified recombinant pea peroxisomal MDAR and cytosolic and chloroplastic GR enzymes produced in Escherichia coli, the effects of peroxynitrite (ONOO(-)) and S-nitrosoglutathione (GSNO) which are known to mediate protein nitration and S-nitrosylation processes, respectively, were analysed. Although ONOO(-) and GSNO inhibit peroxisomal MDAR activity, chloroplastic and cytosolic GR were not affected by these molecules. Mass spectrometric analysis of the nitrated MDAR revealed that Tyr213, Try292, and Tyr345 were exclusively nitrated to 3-nitrotyrosine by ONOO(-). The location of these residues in the structure of pea peroxisomal MDAR reveals that Tyr345 is found at 3.3 Å of His313 which is involved in the NADP-binding site. Site-directed mutagenesis confirmed Tyr345 as the primary site of nitration responsible for the inhibition of MDAR activity by ONOO(-). These results provide new insights into the molecular regulation of MDAR which is deactivated by nitration and S-nitrosylation. However, GR was not affected by ONOO(-) or GSNO, suggesting the existence of a mechanism to conserve redox status by maintaining the level of reduced GSH. Under a nitro-oxidative stress induced by salinity (150mM NaCl), MDAR expression (mRNA, protein, and enzyme activity levels) was increased, probably to compensate the inhibitory effects of S-nitrosylation and nitration on the enzyme. The present data show the modulation of the antioxidative response of key enzymes in the ascorbate-glutathione cycle by nitric oxide (NO)-PTMs, thus indicating the close involvement of NO and reactive oxygen species metabolism in antioxidant defence against nitro-oxidative stress situations in plants. PMID:26116026

  15. Differential molecular response of monodehydroascorbate reductase and glutathione reductase by nitration and S-nitrosylation

    Science.gov (United States)

    Begara-Morales, Juan C.; Sánchez-Calvo, Beatriz; Chaki, Mounira; Mata-Pérez, Capilla; Valderrama, Raquel; Padilla, María N.; Luque, Francisco; Corpas, Francisco J.; Barroso, Juan B.

    2015-01-01

    The ascorbate–glutathione cycle is a metabolic pathway that detoxifies hydrogen peroxide and involves enzymatic and non-enzymatic antioxidants. Proteomic studies have shown that some enzymes in this cycle such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), and glutathione reductase (GR) are potential targets for post-translational modifications (PMTs) mediated by nitric oxide-derived molecules. Using purified recombinant pea peroxisomal MDAR and cytosolic and chloroplastic GR enzymes produced in Escherichia coli, the effects of peroxynitrite (ONOO–) and S-nitrosoglutathione (GSNO) which are known to mediate protein nitration and S-nitrosylation processes, respectively, were analysed. Although ONOO– and GSNO inhibit peroxisomal MDAR activity, chloroplastic and cytosolic GR were not affected by these molecules. Mass spectrometric analysis of the nitrated MDAR revealed that Tyr213, Try292, and Tyr345 were exclusively nitrated to 3-nitrotyrosine by ONOO–. The location of these residues in the structure of pea peroxisomal MDAR reveals that Tyr345 is found at 3.3 Å of His313 which is involved in the NADP-binding site. Site-directed mutagenesis confirmed Tyr345 as the primary site of nitration responsible for the inhibition of MDAR activity by ONOO–. These results provide new insights into the molecular regulation of MDAR which is deactivated by nitration and S-nitrosylation. However, GR was not affected by ONOO– or GSNO, suggesting the existence of a mechanism to conserve redox status by maintaining the level of reduced GSH. Under a nitro-oxidative stress induced by salinity (150mM NaCl), MDAR expression (mRNA, protein, and enzyme activity levels) was increased, probably to compensate the inhibitory effects of S-nitrosylation and nitration on the enzyme. The present data show the modulation of the antioxidative response of key enzymes in the ascorbate–glutathione cycle by nitric oxide (NO)-PTMs, thus indicating the close involvement of NO and reactive oxygen species metabolism in antioxidant defence against nitro-oxidative stress situations in plants. PMID:26116026

  16. Rapid and simple preparation of thiol-ene emulsion-templated monoliths and their application as enzymatic microreactors

    DEFF Research Database (Denmark)

    Lafleur, Josiane P; Senkbeil, Silja

    2015-01-01

    A novel, rapid and simple method for the preparation of emulsion-templated monoliths in microfluidic channels based on thiol-ene chemistry is presented. The method allows monolith synthesis and anchoring inside thiol-ene microchannels in a single photoinitiated step. Characterization by scanning electron microscopy showed that the methanol-based emulsion templating process resulted in a network of highly interconnected and regular thiol-ene beads anchored solidly inside thiol-ene microchannels. Surface area measurements indicate that the monoliths are macroporous, with no or little micro- or mesopores. As a demonstration, galactose oxidase and peptide-N-glycosidase F (PNGase F) were immobilized at the surface of the synthesized thiol-ene monoliths via two different mechanisms. First, cysteine groups on the protein surface were used for reversible covalent linkage to free thiol functional groups on the monoliths. Second, covalent linkage was achieved via free primary amino groups on the protein surface by means of thiol-ene click chemistry and l-ascorbic acid linkage. Thus prepared galactose oxidase and PNGase F microreactors demonstrated good enzymatic activity in a galactose assay and the deglycosilation of ribonuclease B, respectively.

  17. 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.

  18. 3-Oxoacyl-[ACP] reductase from oilseed rape (Brassica napus).

    Science.gov (United States)

    Sheldon, P S; Kekwick, R G; Smith, C G; Sidebottom, C; Slabas, A R

    1992-04-01

    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

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

    DEFF Research Database (Denmark)

    Lokanathan, Arcot R.

    2011-01-01

    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

  20. Mitochondrial thiol modification by a targeted electrophile inhibits metabolism in breast adenocarcinoma cells by inhibiting enzyme activity and protein levels

    Science.gov (United States)

    Smith, M. Ryan; Vayalil, Praveen K.; Zhou, Fen; Benavides, Gloria A.; Beggs, Reena R.; Golzarian, Hafez; Nijampatnam, Bhavitavya; Oliver, Patsy G.; Smith, Robin A.J.; Murphy, Michael P.; Velu, Sadanandan E.; Landar, Aimee

    2016-01-01

    Many cancer cells follow an aberrant metabolic program to maintain energy for rapid cell proliferation. Metabolic reprogramming often involves the upregulation of glutaminolysis to generate reducing equivalents for the electron transport chain and amino acids for protein synthesis. Critical enzymes involved in metabolism possess a reactive thiolate group, which can be modified by certain oxidants. In the current study, we show that modification of mitochondrial protein thiols by a model compound, iodobutyl triphenylphosphonium (IBTP), decreased mitochondrial metabolism and ATP in MDA-MB 231 (MB231) breast adenocarcinoma cells up to 6 days after an initial 24 h treatment. Mitochondrial thiol modification also depressed oxygen consumption rates (OCR) in a dose-dependent manner to a greater extent than a non-thiol modifying analog, suggesting that thiol reactivity is an important factor in the inhibition of cancer cell metabolism. In non-tumorigenic MCF-10A cells, IBTP also decreased OCR; however the extracellular acidification rate was significantly increased at all but the highest concentration (10 µM) of IBTP indicating that thiol modification can have significantly different effects on bioenergetics in tumorigenic versus non-tumorigenic cells. ATP and other adenonucleotide levels were also decreased by thiol modification up to 6 days post-treatment, indicating a decreased overall energetic state in MB231 cells. Cellular proliferation of MB231 cells was also inhibited up to 6 days post-treatment with little change to cell viability. Targeted metabolomic analyses revealed that thiol modification caused depletion of both Krebs cycle and glutaminolysis intermediates. Further experiments revealed that the activity of the Krebs cycle enzyme, aconitase, was attenuated in response to thiol modification. Additionally, the inhibition of glutaminolysis corresponded to decreased glutaminase C (GAC) protein levels, although other protein levels were unaffected. This study demonstrates for the first time that mitochondrial thiol modification inhibits metabolism via inhibition of both aconitase and GAC in a breast cancer cell model. PMID:26774751

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  2. Crystal structures of pinoresinol-lariciresinol and phenylcoumaran benzylic ether reductases and their relationship to isoflavone reductases

    Science.gov (United States)

    Min, Tongpil; Kasahara, Hiroyuki; Bedgar, Diana L.; Youn, Buhyun; Lawrence, Paulraj K.; Gang, David R.; Halls, Steven C.; Park, HaJeung; Hilsenbeck, Jacqueline L.; Davin, Laurence B.; Lewis, Norman G.; Kang, ChulHee

    2003-01-01

    Despite the importance of plant lignans and isoflavonoids in human health protection (e.g. for both treatment and prevention of onset of various cancers) as well as in plant biology (e.g. in defense functions and in heartwood development), systematic studies on the enzymes involved in their biosynthesis have only recently begun. In this investigation, three NADPH-dependent aromatic alcohol reductases were comprehensively studied, namely pinoresinol-lariciresinol reductase (PLR), phenylcoumaran benzylic ether reductase (PCBER), and isoflavone reductase (IFR), which are involved in central steps to the various important bioactive lignans and isoflavonoids. Of particular interest was in determining how differing regio- and enantiospecificities are achieved with the different enzymes, despite each apparently going through similar enone intermediates. Initially, the three-dimensional x-ray crystal structures of both PLR_Tp1 and PCBER_Pt1 were solved and refined to 2.5 and 2.2 A resolutions, respectively. Not only do they share high gene sequence similarity, but their structures are similar, having a continuous alpha/beta NADPH-binding domain and a smaller substrate-binding domain. IFR (whose crystal structure is not yet obtained) was also compared (modeled) with PLR and PCBER and was deduced to have the same overall basic structure. The basis for the distinct enantio-specific and regio-specific reactions of PCBER, PLR, and IFR, as well as the reaction mechanism and participating residues involved (as identified by site-directed mutagenesis), are discussed.

  3. Sucrose mimics the light induction of Arabidopsis nitrate reductase gene transcription

    DEFF Research Database (Denmark)

    Cheng, Chi-Lien; Acedo, Gregoria N

    1992-01-01

    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.

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

    International Nuclear Information System (INIS)

    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 LC50,48h (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 (?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.

  5. 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)

    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

    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.

  6. 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

  7. Functionalization of embedded thiol-ene waveguides for evanescent wave-induced fluorescence detection in a microfluidic device

    DEFF Research Database (Denmark)

    Feidenhans, Nikolaj A.; Jensen, Thomas Glasdam; Lafleur, Josiane P.; Kutter, Jörg P.

    functionalized with biotin using photografting. The biotin was used for immobilization of fluorescently labelled streptavidin, and experiments revealed a linear correlation between streptavidin concentration and fluorescent intensity. To further demonstrate the attractiveness of using thiol-ene for optofluidic...

  8. Functionalization of embedded thiol-ene waveguides for evanescent wave induced fluorescence detection in a microfluidic device

    DEFF Research Database (Denmark)

    Feidenhans'l, Nikolaj Agentoft; Jensen, Thomas Glasdam; Lafleur, Josiane P.; Kutter, Jörg Peter

    functionalized with biotin using photografting. The biotin was used for immobilization of fluorescently labelled streptavidin, and experiments revealed a linear correlation between streptavidin concentration and fluorescent intensity. To further demonstrate the attractiveness of using thiol?ene for optofluidic...

  9. Modification of porous silicon rugate filters through thiol-yne photochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Soeriyadi, Alexander H., E-mail: alexander.soeriyadi@unsw.edu.au; Zhu, Ying, E-mail: alexander.soeriyadi@unsw.edu.au; Gooding, J. Justin, E-mail: justin.gooding@unsw.edu.au [Australian Centre for Nanomedicine and School of Chemistry, University of New South Wales, Sydney 2052 (Australia); Reece, Peter [School of Physics, University of New South Wales, Sydney 2052 (Australia)

    2014-02-24

    Porous silicon (PSi) has a considerable potential as biosensor platform. In particular, the ability to modify the surface chemistry of porous silicon is of interest. Here we present a generic method to modify the surface of porous silicon through thiol-yne photochemistry initiated by a radical initiator. Firstly, a freshly etched porous silicon substrate is modified through thermal hydrosilylation with 1,8-nonadiyne to passivate the surface and introduce alkyne functionalities. The alkyne functional surface could then be further reacted with thiol species in the presence of a radical initiator and UV light. Functionalization of the PSi rugate filter is followed with optical reflectivity measurements as well as high resolution X-ray photoelectron spectroscopy (XPS)

  10. The Role of Thiol on Degradation of Pentaerythrityl Tetranitrate and Isosorbide Dinitrate

    Directory of Open Access Journals (Sweden)

    J.S. Pamudji

    2011-01-01

    Full Text Available Thiols such as N-acetylcystein (NAC are used to replenish glutathione (GSH level, with regard to their function in the maintenance of cellular reduction-oxidation balance and control of oxidative stress. Thiols play a role in the reductive metabolism of nitrates to NO, an important signaling molecule in the cardiovascular system as well as other systems throughout the body. This study aimed to evaluate the influence of NAC on decomposition of different organic nitrate esters according to its potential i.e., pentaerythrityl tetranitrate (PETN and isosorbide dinitrate (ISDN. The results showed that NAC gives a rapid and significant decrease of PETN and ISDN during the incubation period. During the experiment, about 85% of PETN were decomposed, while the decomposition of ISDN was about 20%. Detection of nitrite and elucidation of disulphide bond of NAC gives evidence that confirms the presence of reactions.

  11. Thiol- and Biotin-Labeled Probes for Oligonucleotide Quartz Crystal Microbalance Biosensors of Microalga Alexandrium Minutum

    Directory of Open Access Journals (Sweden)

    Mathieu Lazerges

    2012-07-01

    Full Text Available Two quartz crystal microbalance oligonucleotide biosensors of a toxic microalga gene sequence (Alexandrium Minutum have been designed. Grafting on a gold surface of 20-base thiol- or biotin-labeled probe, and selective hybridization with the complementary 20-base target, have been monitored in situ with a 27 MHz quartz crystal microbalance under controlled hydrodynamic conditions. The frequency of the set up is stable to within a few hertz, corresponding to the nanogram scale, for three hour experiments. DNA recognition by the two biosensors is efficient and selective. Hybridization kinetic curves indicate that the biosensor designed with the thiol-labeled probe is more sensitive, and that the biosensor designed with the biotin-labeled probe has a shorter time response and a higher hybridization efficiency.

  12. Enantioselective syntheses and sensory properties of 2-methyl-tetrahydrofuran-3-thiol acetates.

    Science.gov (United States)

    Dai, Yifeng; Shao, Junqiang; Yang, Shaoxiang; Sun, Baoguo; Liu, Yongguo; Ning, Ting; Tian, Hongyu

    2015-01-21

    The enantioselective synthesis of four stereoisomers of 2-methyl-tetrahydrofuran-3-thiol acetate was achieved. The two enantiomers of the important intermediate cis-2-methyl-3-hydroxy-tetrahydrofuran were obtained by Sharpless asymmetric dihydroxylation (AD), whereas the two enantiomers of trans-2-methyl-3-hydroxy-tetrahydrofuran were derived from the corresponding optically active cis-isomers by Mitsunobu reaction. Each stereoisomer of 2-methyl-3-hydroxy-tetrahydrofuran went through mesylation and nucleophilic substitution to afford the corresponding product with specific configuration. (2R,3S)- and (2R,3R)-2-methyl-tetrahydrofuran-3-thiol acetate were obtained in 80% ee, whereas the (2S,3R)- and (2S,3S)-isomers were in 62% ee. The odor properties of the synthesized four stereoisomers were evaluated by gas chromatography-olfactometry (GC-O), which revealed perceptible differences among stereoisomers both in odor features and in intensities. PMID:25560460

  13. Patterned Hydrophilization of Nanoporous 1,2?PB by Thiol?ene Photochemistry

    DEFF Research Database (Denmark)

    Berthold, Anton; Sagar, Kaushal Shashikant

    2011-01-01

    We present an efficient method for functionalizing the large polymer–air interface of a gyroid nanoporous polymer. The hydrophilicity of nanoporous cross?linked 1,2?polybutadiene is tuned by thiol?ene photo?grafting of mercaptosuccinic acid or sodium 2?mercaptoethanesulfonate. The reaction is monitored by FT?IR, UV–Vis, contact angle, and gravimetry. Overall quantum yields are calculated for the two thiol?ene “click” reactions in nano?confinement, neatly revealing their chain?like nature. Top–down photolithographic patterning is demonstrated, realizing hydrophilic nanoporous “corridors” exclusively hosting water. The presented approach can be relevant for many applications where, e.g., high control and contrast in hydrophilicity, chemical functionality or refractive index are needed.

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

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Hvilsted, Søren

    2008-01-01

    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, subsequ......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...

  15. Patterned Hydrophilization of Nanoporous 1,2?PB by Thiol?ene Photochemistry

    DEFF Research Database (Denmark)

    Berthold, Anton; Sagar, Kaushal Shashikant; Ndoni, Sokol

    2011-01-01

    We present an efficient method for functionalizing the large polymer–air interface of a gyroid nanoporous polymer. The hydrophilicity of nanoporous cross?linked 1,2?polybutadiene is tuned by thiol?ene photo?grafting of mercaptosuccinic acid or sodium 2?mercaptoethanesulfonate. The reaction is...... monitored by FT?IR, UV–Vis, contact angle, and gravimetry. Overall quantum yields are calculated for the two thiol?ene “click” reactions in nano?confinement, neatly revealing their chain?like nature. Top–down photolithographic patterning is demonstrated, realizing hydrophilic nanoporous “corridors......” exclusively hosting water. The presented approach can be relevant for many applications where, e.g., high control and contrast in hydrophilicity, chemical functionality or refractive index are needed....

  16. Tritium isotopic exchange between hydrogen sulfide and thiols in gas phase

    International Nuclear Information System (INIS)

    It has been established that the rate constant of tritium isotopic exchange between hydrogen sulfide and thiols within the temperature range 293-333K is given by k[dm3.mole-1.s-1]=p.exp[-6000[J.mole-1]/RT] where p are (6+-1.7)x10-2, (4.6+-0.5)x10-2, (3.8+-0.7)x10-2, (7.1+-1.2)x10-3 for methyl, ethyl, n-propyl, i-propyl thiol, respectively. The total order of the reaction is equal to 2, and the partial orders in respect to H2S and thol are equal to 1. The mechanism of the isotopic exchange is discussed. (author)

  17. Field effect on digestive ripening of thiol-capped gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Meng-Lin; Peng, J. S.; Lee, Sanboh, E-mail: sblee@mx.nthu.edu.tw [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Yang, Fuqian [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506 (United States)

    2014-02-07

    We studied the digestive ripening of thiol-capped gold nanoparticles under simultaneous action of electric field and reflux heating in a silicone oil bath at 130?°C, using transmission electron microscopy. Observation revealed that a polydispersed gold nanoparticle system reached the state of nearly monodispersity under the action of an electric field and the thiol-capped gold nanoparticles carried negative charges. The electric field caused the increase of the particle size for the nearly monodispersed gold nanoparticle system. The self-assembly of the nearly monodisperse gold nanoparticles under the action of an electric field of a high field intensity was observed. The gold nanoparticles tended to form self-assembled nanostructures of six-fold symmetry. This study provides a new route for system engineering to control the particle size of metallic nanoparticles by electric field and digestive ripening.

  18. Determination of the potential of zero charge of Au(111) modified with thiol monolayers.

    Science.gov (United States)

    Ramírez, Pablo; Andreu, Rafael; Cuesta, Angel; Calzado, Carmen J; Calvente, Juan José

    2007-09-01

    A new method is proposed for the determination of the potential of zero charge of gold electrodes modified with thiol monolayers. It makes use of the immersion technique, in combination with a vapor deposition protocol to build the thiol monolayers. As compared to previous methods, the present approach provides more accurate results, particularly in the case of long-chain alkanethiol monolayers, and it is applicable to any monolayer irrespective of its degree of hydrophilicity. Results are presented for a series of 12 alkanethiol monolayers and for 11-mercaptoundecanol and 11-mercaptoundecanoic acid monolayers. Good agreement is found between the variation of the potential of zero charge along the alkanethiol series with the corresponding change of the surface work function. The potential of zero charge of the 11-mercaptoundecanoic acid monolayer is shown to depend on the extent of dissociation of the acid, thus opening the possibility of applying this type of measurements to the study of surface ionization processes. PMID:17676927

  19. Pendant thiol groups-attached Pd(II) for initiating metal deposition

    International Nuclear Information System (INIS)

    A new activation method has been developed for initiating electroless metal deposition on silicon substrates without SnCl2 sensitization and roughening condition. Silicon wafers are first coated with thiol-terminated self-assembled monolayers (SAMs), and then catalyzed with a stable tin-free Pd(II)-based colloidal solution. Atomic force microscopy (AFM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were used to characterize the step-by-step surfaces and study the binding mechanism of Pd(II) with SAMs onto surfaces. Results show that Pd(II) oligomer particles are chemisorbed on pendant thiol surfaces through S-Pd bonds. This process involves fewer steps than the conventional Sn/Pd combined activation one. Furthermore, the chemical bound initiator possesses longevity and can be stored for a long time before metallization

  20. Pendant thiol groups-attached Pd(II) for initiating metal deposition

    Energy Technology Data Exchange (ETDEWEB)

    Xu Lina; Liao Jianhui; Huang Lan; Gu Ning; Zhang Haiqian; Liu Juzheng

    2003-04-30

    A new activation method has been developed for initiating electroless metal deposition on silicon substrates without SnCl{sub 2} sensitization and roughening condition. Silicon wafers are first coated with thiol-terminated self-assembled monolayers (SAMs), and then catalyzed with a stable tin-free Pd(II)-based colloidal solution. Atomic force microscopy (AFM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were used to characterize the step-by-step surfaces and study the binding mechanism of Pd(II) with SAMs onto surfaces. Results show that Pd(II) oligomer particles are chemisorbed on pendant thiol surfaces through S-Pd bonds. This process involves fewer steps than the conventional Sn/Pd combined activation one. Furthermore, the chemical bound initiator possesses longevity and can be stored for a long time before metallization.

  1. Characterization of Helicobacter pylori adhesin thiol peroxidase (HP0390) purified from Escherichia coli

    Indian Academy of Sciences (India)

    Huyen Thi Minh Nguyen; Kwang-Ho Nam; Yasar Saleem; Key-Sun Kim

    2010-06-01

    The antioxidant protein, adhesin thiol peroxidase (HpTpx or HP0390), plays an important role in enabling Helicobacter pylori to survive gastric oxidative stress. The bacterium colonizes the host stomach and produces gastric cancer. However, little information is available about the biochemical characteristics of HpTpx. We expressed recombinant HpTpx in Escherichia coli, purified to homogeneity, and characterized it. The results showed that HpTpx existed in a monomeric hydrodynamic form and the enzyme fully retained its peroxidase and antioxidant activities. The catalytic reaction of the enzyme was similar to an atypical 2-cysteine peroxiredoxin (Prx). The conformation of the enzyme was observed in the presence and absence of dithiothreitol (DTT); similar to other known thiol peroxidases, conformational change was observed in HpTpx by the addition of DTT.

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

    Science.gov (United States)

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

    2013-03-13

    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 (stone, and cotton fabric. PMID:23410965

  3. Molecular cloning and characterization of a cDNA encoding pea monodehydroascorbate reductase.

    Science.gov (United States)

    Murthy, S S; Zilinskas, B A

    1994-12-01

    Monodehydroascorbate radicals are generated in plant cells enzymatically by the hydrogen peroxide scavenging enzyme, ascorbate peroxidase, and nonenzymatically via the univalent oxidation of ascorbate by superoxide, hydroxyl, and various organic radicals. Regeneration of ascorbate is achieved by monodehydroascorbate reductase (EC 1.6.5.4) using NAD(P)H as an electron donor or, alternatively, by a set of two coupled reactions requiring dehydroascorbate reductase, glutathione reductase, glutathione, and NAD(P)H. As monodehydroascorbate reductase is a key enzyme in maintaining reduced pools of ascorbate, an important antioxidant, we undertook this study to learn more about its structure, function, and regulation. Herein we report the molecular cloning and characterization of a cDNA encoding monodehydroascorbate reductase of pea (Pisum sativum L.). The cDNA encodes a 433-amino acid polypeptide that shows, respectively, 73 and 87% identity with peptide fragments from soybean and cucumber monodehydroascorbate reductase. Monodehydroascorbate reductase contains the NAD(P)H and FAD binding domains of other flavin oxidoreductases. The cloned enzyme lacks a transit peptide, but the sequence of the carboxyl terminus is Ser-Lys-Ile, similar to the targeting motif found in peroxisomal proteins. When expressed in Escherichia coli fused to maltose-binding protein, monodehydroascorbate reductase has enzymatic properties comparable with purified soybean and cucumber monodehydroascorbate reductase. Northern blot analysis shows that the monodehydroascorbate reductase transcript is 1.6 kilobase in size and is expressed at relatively low levels in all plant tissues examined. PMID:7983054

  4. Photoreactivation of nitrate reductase production in Nicotiana tabacum var. Xanthi

    International Nuclear Information System (INIS)

    Ultraviolet (254 nm) irradiation of liquid-cultured tobacco cells inhibited the production of nitrate reductase; subsequent illumination with white light allowed a partial restoration of the synthesis of the enzyme (photoreactivation). Ultraviolet irradiation of these same cells also inhibited their ability to incorporate labeled uridine and labeled amino acids. Subsequent illumination with white light gave a partial restoration of the ability of the cells to incorporate uridine while a similar post-ultraviolet-irradiation treatment failed to restore the amino acid incorporation. The system in tobacco known to repair ultraviolet-damaged viral RNA thus does not seem to repair ultraviolet damage to the protein-synthesizing system of the cell. The photoreactivation of nitrate reductase production is best explained by the action of a DNA photorepairing system

  5. A Dendritic Thioester Hydrogel Based on Thiol-Thioester Exchange as a Dissolvable Sealant System for Wound Closure

    OpenAIRE

    Ghobril, Cynthia; Charoen, Kristie; Rodriguez, Edward K; Nazarian, Ara; Grinstaff, Mark W

    2013-01-01

    A dissolvable dendritic thioester hydrogel based on thiol-thioester exchange for wound closure is reported. The hydrogel sealant adheres strongly to tissues, closes an ex vivo vein puncture, and withstands high pressures placed on a wound. The hydrogel sealant can be completely washed off upon exposure to thiolates based on thiol-thioester exchange and allow gradual wound re-exposure during definitive surgical care.

  6. CxxS: Fold-independent redox motif revealed by genome-wide searches for thiol/disulfide oxidoreductase function

    OpenAIRE

    Fomenko, Dmitri E; GLADYSHEV, Vadim N.

    2002-01-01

    Redox reactions involving thiol groups in proteins are major participants in cellular redox regulation and antioxidant defense. Although mechanistically similar, thiol-dependent redox processes are catalyzed by structurally distinct families of enzymes, which are difficult to identify by available protein function prediction programs. Herein, we identified a functional motif, CxxS (cysteine separated from serine by two other residues), that was often conserved in redox enzymes, but rarely in ...

  7. Thiol-ene microfluidic devices for microchip electrophoresis: Effects of curing conditions and monomer composition on surface properties.

    Science.gov (United States)

    Tähkä, Sari M; Bonabi, Ashkan; Nordberg, Maria-Elisa; Kanerva, Meeri; Jokinen, Ville P; Sikanen, Tiina M

    2015-12-24

    Thiol-ene polymer formulations are raising growing interest as new low-cost fabrication materials for microfluidic devices. This study addresses their feasibility for microchip electrophoresis (MCE) via characterization of the effects of UV curing conditions and aging on the surface charge and wetting properties. A detailed comparison is made between stoichiometric thiol-ene (1:1) and thiol-ene formulations bearing 50% molar excess of allyls ("enes"), both prepared without photoinitiator or other polymer modifiers. Our results show that the surface charge of thiol-ene 1:1 increases along with increasing UV exposure dose until a threshold (here, about 200J/cm(2)), whereas the surface charge of thiol-ene 2:3 decreases as a function of increasing UV dose. However, no significant change in the surface charge upon storage in ambient air was observed over a period of 14 days (independent of the curing conditions). The water contact angles of thiol-ene 2:3 (typically 70-75°) were found to be less dependent on the UV dose and storing time. Instead, water contact angles of thiol-ene 1:1 slightly decrease (from initial 90 to 95° to about 70°) as a function of UV increasing exposure dose and storing time. Most importantly, both thiol-ene formulations remain relatively hydrophilic over extended periods of time, which favors their use in MCE applications. Here, MCE separation of biologically active peptides and selected fluorescent dyes is demonstrated in combination with laser-induced fluorescence detection showing high separation efficiency (theoretical plates 8200 per 4cm for peptides and 1500-2700 per 4cm for fluorescent dyes) and lower limits of detection in the sub-?M (visible range) or low-?M (near-UV range) level. PMID:26654831

  8. 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)

    Anita M. Raut

    2013-04-01

    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.

  9. Probing Conformational Changes of Prestin with Thiol-Reactive Optical Switches

    OpenAIRE

    fang, Jie; Sakata, Tomoyo; Marriott, Gerard; Iwasa, Kuni H

    2008-01-01

    Thiol-reactive optical switch probes were used to examine conformational changes of prestin-based membrane motor. Because this motor is based on mechanoelectric coupling similar to piezoelectricity, the motile activity can be monitored by charge movements across the plasma membrane, which appears as nonlinear capacitance. When the plasma membrane is conjugated with the probes, optically induced spiro-merocyanine transition positively shifted nonlinear capacitance of outer hair cells and prest...

  10. Thiol isomerases negatively regulate the cellular shedding activity of ADAM17.

    OpenAIRE

    Willems, Sofie H; Tape, Christopher James; Stanley, Peter L.D.; Taylor, Neil A.; Mills, Ian G; Neal, David E; Mccafferty, John; Murphy, Gillian

    2010-01-01

    Abstract The disintegrin metalloprotease ADAM17 can rapidly modulate cell surface signalling events by the proteolytic release of soluble forms of pro-ligands for cellular receptors. Many regulatory pathways effect ADAM17 sheddase activity, but the mechanisms for its activation are still not clear. We have utilized a cell based ADAM17 assay to show that thiol isomerases, specifically protein disulphide isomerase, could be responsible for maintaining ADAM17 in ...

  11. Photolithographic fabrication of solid–liquid core waveguides by thiol-ene chemistry

    DEFF Research Database (Denmark)

    Sagar, Kaushal Shashikant; Gopalakrishnan, Nimi; Christiansen, Mads Brøkner; Kristensen, Anders; Ndoni, Sokol

    2011-01-01

    In this work we demonstrate an efficient and cleanroom compatible method for the fabrication of solid–liquid core waveguides based on nanoporous polymers. We have used thiol-ene photo-grafting to tune and pattern the hydrophilicity of an originally hydrophobic nanoporous 1, 2-polybutadiene. The generated refractive index contrast between the patterned water-filled volume and the surrounding empty hydrophobic porous polymer allows for light confinement within the water-filled volume—the solid–liq...

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

    Directory of Open Access Journals (Sweden)

    Mingzhong Cai

    2009-09-01

    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.

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

    OpenAIRE

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

    2013-01-01

    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 oxida...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-01

    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)

  15. Thiol- and Biotin-Labeled Probes for Oligonucleotide Quartz Crystal Microbalance Biosensors of Microalga Alexandrium Minutum

    OpenAIRE

    Mathieu Lazerges; Hubert Perrot; Niriniony Rabehagasoa; Chantal Compère

    2012-01-01

    Two quartz crystal microbalance oligonucleotide biosensors of a toxic microalga gene sequence (Alexandrium Minutum) have been designed. Grafting on a gold surface of 20-base thiol- or biotin-labeled probe, and selective hybridization with the complementary 20-base target, have been monitored in situ with a 27 MHz quartz crystal microbalance under controlled hydrodynamic conditions. The frequency of the set up is stable to within a few hertz, corresponding to the nanogram scale, for three hour...

  16. Immobilization of enzymes via microcontact printing and thiol-ene click chemistry.

    Science.gov (United States)

    Buhl, Moritz; Vonhören, Benjamin; Ravoo, Bart Jan

    2015-06-17

    This Communication describes a bioconjugation method for the generation of enzyme microarrays on surfaces using photochemical thiol-ene chemistry in combination with microcontact printing. Glucose oxidase and lactase were readily immobilized (i.e., printing time 2 min) on alkene terminated self-assembled monolayers on glass as demonstrated by X-ray photoelectron spectroscopy and fluorescence microscopy. Furthermore, the activity of both immobilized enzymes was confirmed in single enzyme as well as cascade transformations. PMID:26030726

  17. Evaluation of serum thiol levels in patients with non ST elevation acute coronary syndrome

    OpenAIRE

    Fatih TANRIVERD?; KAVAKLI, Havva ?AH?N; KURTO?LU ÇEL?K, Gülhan; ?ÇME, Ferhat; ?ENER, Alp; KARAKAYALI, Onur; Vural, Sevilay

    2014-01-01

    Imbalance between antioxidant and oxidant systems in the body play an important role in the pathogenesis of coronary atherosclerosis and its complications. The aim of this clinical study was to investigate total serum thiol (TS-H) levels in patients with non ST Elevation Acute Coronary Syndrome (NSTE-ACS) patients and relationships between these results and cardiac markers. This study included 55 patients and a control group consisted of 50 healthy people. Samples for serum total TS-H levels ...

  18. Synthesis of Non-spherical Glycopolymer-Decorated Nanoparticles: Combing Thiol-ene with Catecholic Chemistry.

    Science.gov (United States)

    Li, Xiao; Zhang, Weidong; Chen, Gaojian

    2016-01-01

    Glycopolymers with carbohydrate side chains are currently being applied in many fields, with much potential for disease treatment. The shape of glycopolymer-bearing nanoparticles has obvious effects on the nanoparticle-cell interaction and is therefore important for the applications of glycopolymers in biological systems. Here a synthetic approach to prepare non-spherical glycopolymer-coated iron oxide nanoparticles is provided, by combing the convenience of inorganic shape control, catecholic chemistry, and thiol-ene reaction. PMID:26537471

  19. Adaptive aneuploidy protects against thiol peroxidase deficiency by increasing respiration via key mitochondrial proteins.

    Science.gov (United States)

    Kaya, Alaattin; Gerashchenko, Maxim V; Seim, Inge; Labarre, Jean; Toledano, Michel B; Gladyshev, Vadim N

    2015-08-25

    Aerobic respiration is a fundamental energy-generating process; however, there is cost associated with living in an oxygen-rich environment, because partially reduced oxygen species can damage cellular components. Organisms evolved enzymes that alleviate this damage and protect the intracellular milieu, most notably thiol peroxidases, which are abundant and conserved enzymes that mediate hydrogen peroxide signaling and act as the first line of defense against oxidants in nearly all living organisms. Deletion of all eight thiol peroxidase genes in yeast (?8 strain) is not lethal, but results in slow growth and a high mutation rate. Here we characterized mechanisms that allow yeast cells to survive under conditions of thiol peroxidase deficiency. Two independent ?8 strains increased mitochondrial content, altered mitochondrial distribution, and became dependent on respiration for growth but they were not hypersensitive to H2O2. In addition, both strains independently acquired a second copy of chromosome XI and increased expression of genes encoded by it. Survival of ?8 cells was dependent on mitochondrial cytochrome-c peroxidase (CCP1) and UTH1, present on chromosome XI. Coexpression of these genes in ?8 cells led to the elimination of the extra copy of chromosome XI and improved cell growth, whereas deletion of either gene was lethal. Thus, thiol peroxidase deficiency requires dosage compensation of CCP1 and UTH1 via chromosome XI aneuploidy, wherein these proteins support hydroperoxide removal with the reducing equivalents generated by the electron transport chain. To our knowledge, this is the first evidence of adaptive aneuploidy counteracting oxidative stress. PMID:26261310

  20. Mitochondrial Sulfide Detoxification Requires a Functional Isoform O-Acetylserine(thiol)lyase C in Arabidopsis thaliana

    OpenAIRE

    Álvarez, Consolación; García, Irene; Romero, Luis C; Gotor, Cecilia

    2012-01-01

    In non-cyanogenic species, the main source of cyanide derives from ethylene and camalexin biosyntheses. In mitochondria, cyanide is a potent inhibitor of the cytochrome c oxidase and is metabolised by the β-Cyanoalanine synthase CYS-C1, catalysing the conversion of cysteine and cyanide to hydrogen sulfide and β- cyanoalanine. The hydrogen sulfide released also inhibits the cytochrome c oxidase and needs to be detoxified by the O-acetylserine(thiol)lyase mitochondrial isoform, OAS-C, which cat...

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

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Hvilsted, Søren

    2009-01-01

    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 capp...

  2. Polarographic determination of europium(III) with 3-hydroxypyridine-2-thiol

    Energy Technology Data Exchange (ETDEWEB)

    Sindhu, R.S.; Katyal, M.; Puri, B.K.

    1987-11-20

    The polarographic behavior of europium(III) has been studied in 3-hydroxypyridine-2-thiol (HPT) as the supporting electrolyte. The polarographic wave in this electrolyte is diffusion controlled, quasi-reversible, and well defined, and there is no need of a maximum suppressor. The interference of various ions has been studied in detail, and this method has been utilized for the quantitative determination of europium in various synthetic samples

  3. Thiol dependent recovery of catalytic activity from oxidized protein tyrosine phosphatases

    OpenAIRE

    Parsons, Zachary D.; Gates, Kent S.

    2013-01-01

    Protein tyrosine phosphatases (PTPs) play an important role in the regulation of mammalian signal transduction. During some cell signaling processes, the generation of endogenous hydrogen peroxide inactivates selected PTPs via oxidation of the enzyme's catalytic cysteine thiolate group. Importantly, low molecular weight and protein thiols in the cell have the potential to regenerate the catalytically active PTPs. Here we examined the recovery of catalytic activity from two oxidatively-inactiv...

  4. The effect of a thiol-containing organic molecule on molybdenum adsorption onto pyrite

    Science.gov (United States)

    Freund, Carla; Wishard, Anthony; Brenner, Ryan; Sobel, Marisa; Mizelle, Jack; Kim, Alex; Meyer, Drew A.; Morford, Jennifer L.

    2016-02-01

    The effect of a small thiol-containing organic molecule on the adsorption of Mo to pyrite was investigated through the use of equilibration experiments with molybdate (MoO42-), tetrathiomolybdate (MoS42-), and 2-mercaptopropionic acid (2MPA). MoO42-, MoS42-, and 2MPA individually adsorb to pyrite through the formation of specific interactions with the mineral surface. In select combination experiments, 2MPA effectively out-competes MoO42- for pyrite surface sites, which is indicative of the relatively weaker MoO42--pyrite interactions. Results suggest that the presence of 2MPA on the pyrite surface would inhibit MoO42- access to catalytic mineral surface sites for the transformation of MoO42- to MoS42-. In contrast, thiols are not expected to be an obstacle to Mo uptake once the "switch point", or the critical H2S concentration required for the formation of MoS42-, has been surpassed. This is due to the stronger adsorption of MoS42- to the pyrite surface. EXAFS results support weak specific interactions with little change to the MoO42- environment upon adsorption to pyrite. In contrast, larger changes to the Mo-S internuclear distances during MoS42- adsorption to pyrite support a more substantial structural change upon adsorption. MoS42- is able to bind to both the pyrite surface and a thiol-containing organic molecule to form a ternary structure on the pyrite surface, and may provide for a molecular-level connection between Mo and thiol-containing organic molecules. Mo(VI) is reduced to Mo(IV) during MoS42- adsorption to pyrite as a result of ligand-induced reduction, thereby confirming that the thiolated form of Mo is necessary for Mo reduction.

  5. Liquid-Crystalline Thiol- and Disulfide-Based Dendrimers for the Functionalization of Gold Nanoparticles

    OpenAIRE

    Frein, Stéphane; Boudon, Julien; Vonlanthen, Mireille; Scharf, Toral; Barberá, Joaquín; Süss-Fink, Georg; Bu?rgi, Thomas; Deschenaux, Robert

    2009-01-01

    Liquid-crystalline dendrons carrying either a thiol or disulfide function which display nematic, smectic A, columnar, or chiral nematic phases have been synthesized. Their mesomorphic properties are in agreement with the nature of the mesogenic units and structure of the dendrons. The first-generation poly(aryl ester) dendron containing two cyanobiphenyl mesogenic units was used to functionalize gold nanoparticles. For full coverage, a smectic-like supramolecular organization on the nanometer...

  6. Inhibition of the metallo-beta-lactamase produced from Serratia marcescens by thiol compounds.

    Science.gov (United States)

    Goto, M; Takahashi, T; Yamashita, F; Koreeda, A; Mori, H; Ohta, M; Arakawa, Y

    1997-11-01

    Low molecular weight thiol compounds have been found to be strong inhibitors of metallo-beta-lactamase (IMP-1) produced by Serratia marcescens TN9106, which was expressed by Echerichia coli JM109 cells. Mercaptoacetic acid and 2-mercaptopropionic acid strongly and competitively inhibited IMP-1 with Ki of 0.23 and 0.19 microM, respectively. 2-Mercaptoethanol reversibly inhibited IMP-1 but did not show simple competitive inhibition. PMID:9401719

  7. Surface spectroscopic and electrochemical investigations of aromatic and heteroaromatic thiols on gold single crystal surfaces

    OpenAIRE

    Whelan, Caroline

    1998-01-01

    This thesis is devoted to the study of aromatic and heteroaromatic thiol selfassembly on Au single crystal surfaces. A range of surface spectroscopic and electrochemical techniques have been used to investigate the formation of complex assemblies in terms of the types of surface intermediates formed, adsórbate orientation and the mechanism of adsorption from the gas and liquid phases. The self-assembly process is reviewed, with particular emphasis on aromatic self-assembled monolayers (SA...

  8. Thiol-mediated multiple mechanisms centered on selenodiglutathione determine selenium cytotoxicity against MCF-7 cancer cells.

    Science.gov (United States)

    Tobe, Takao; Ueda, Koji; Ando, Motozumi; Okamoto, Yoshinori; Kojima, Nakao

    2015-06-01

    Selenium (Se) is an essential antioxidative micronutrient but can exert cancer-selective cytotoxicity if the nutritional levels are too high. Selenodiglutathione (GSSeSG) is a primary Se metabolite conjugated with two glutathione (GSH) moieties. GSSeSG has been suggested to be an important molecule for cytotoxicity. Here, we propose the underlying mechanisms for the potent cytotoxicity of GSSeSG: cellular intake; reductive metabolism; production of reactive oxygen species; oxidative damage to DNA; apoptosis induction. GSSeSG rather than selenite decreased cell viability and induced apoptosis accompanied by increases in intracellular Se contents. Therefore, GSSeSG-specific cytotoxicity may be ascribed to its preferable incorporation. Base oxidation and strand fragmentation in genomic DNA preceded cell death, suggesting that oxidative stress (including DNA damage) is crucial for GSSeSG cytotoxicity. Strand breaks of purified DNA were caused by the coexistence of GSSeSG and thiols (GSH, cysteine, homocysteine), but not the oxidized form or non-thiol reductants. This implies the important role of intracellular thiols in the mechanism of Se toxicity. GSH-assisted DNA strand breaks were inhibited by specific scavengers for hydrogen peroxide or hydroxyl radicals. The GSSeSG metabolite selenide induced some DNA strand breaks without GSH, whereas elemental Se did so only with GSH. These observations suggest involvement of Fenton-type reaction in the absence of transition metals and reactivation of inert elemental Se. Overall, our results suggest that chemical interactions between Se and the sulfur of thiols are crucial for the toxicity mechanisms of Se. PMID:25783495

  9. Direct recognition and quantification by voltammetry of thiol/thioamide mixes in seawater.

    Science.gov (United States)

    Laglera, Luis M; Tovar-Sánchez, Antonio

    2012-01-30

    Thiols and thioamides form part of the pool of reduced sulfur substances (RSS) that modify the health of aquatic ecosystems acting as radical scavengers and heavy metal ligands. Their concentrations could be easily determined in seawater by cathodic stripping voltammetry (CSV) were it not be for the coalescence of their responses in a single peak. Here, we modified the traditional CSV method of RSS analysis to allow individual recognition and quantification in thiol/thioamide mixes. Glutathione, cysteine, thiourea and thioacetamide in UV digested seawater were repeatedly analyzed shifting the deposition potential (E(dep)) in the range +0.07 to -0.4V at high resolution. The representation of peak height (i(p)) and peak potential (E(p)) vs E(dep) resulted in different and distinctive profiles for each substance that allowed the selection of adequate E(dep) ranges for their separate quantification. Copper saturation modified thiol profiles and cancelled the response of thioamides. The vs E(dep) profiles explained the nature of the different thiols and thioamides present in the sample and permitted their individual quantification with excellent accuracy. The utility of the method was put to test with seawater modified with natural unknown RSS from pore waters and Posidonia oceanica exudates. Although both samples gave similar CSV signals, the vs E(dep) profiles unveiled completely different electrochemical behaviors incompatible with a similar nature. Based on those profiles we hypothesized that pore waters released a glutathione/thiourea mix and that one or several unidentified RSS formed part of P. oceanica exudates. The analytical scheme proposed here opens a new door to the use of direct voltammetry in the qualitative and quantitative determination of RSS in natural waters. PMID:22284523

  10. Two methylenetetrahydrofolate reductase gene (MTHFR) polymorphisms, schizophrenia and bipolar disorder

    DEFF Research Database (Denmark)

    Jönsson, Erik G; Larsson, Kristina; Vares, Maria; Hansen, Thomas; Wang, August G; Djurovic, Srdjan; Rønningen, Kjersti S; Andreassen, Ole A; Agartz, Ingrid; Werge, Thomas; Terenius, Lars; Hall, Håkan

    2008-01-01

    Recent meta-analyses of the methylenetetrahydrofolate reductase gene (MTHFR) have suggested association between two of its functional single gene polymorphisms (SNPs; C677T and A1298C) and schizophrenia. Studies have also suggested association between MTHFR C677T and A1298C variation and bipolar disorder. In a replication attempt the MTHFR C677T and A1298C SNPs were analyzed in three Scandinavian schizophrenia case-control samples. In addition, Norwegian patients with bipolar disorder were inves...

  11. S-Nitrosoglutathione Reductase: An Important Regulator in Human Asthma

    OpenAIRE

    Que, Loretta G.; Yang, Zhonghui; Stamler, Jonathan S.; Lugogo, Njira L.; Kraft, Monica

    2009-01-01

    Rationale: Nitric oxide bioactivity, mediated through the formation of S-nitrosothiols (SNOs), has a significant effect on bronchomotor tone. S-Nitrosoglutathione is an endogenous bronchodilator that is decreased in children with asthmatic respiratory failure and in adults with asthma undergoing segmental airway challenge. Recently we showed that S-nitrosoglutathione reductase (GSNOR) regulates endogenous SNOs. Mice with genetic deletion of GSNOR are protected from airway hyperresponsivity in...

  12. Aldose reductase inhibition abolishes glucose-induced endothelial dysfunction.

    Czech Academy of Sciences Publication Activity Database

    Pekarová, Michaela; Chatzopoulou, M.; Nicolaou, I.; Demopoulos, V.; Lojek, Antonín; Papežíková, Ivana

    Tren?ianske Teplice, 2008. s. 105-106. ISSN 1337-6853. [TOXCON 2008, Integration of Toxicological Research Within V4, 13th Interdisciplinary Toxicology Conference. 27.05.2008-30.05.2008, Tren?ianske Teplice] R&D Projects: GA ?R(CZ) GP204/07/P539 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : aldose reductase * endothelial dysfunction * hyperglycemia Subject RIV: BO - Biophysics

  13. The mechanism of high Mr thioredoxin reductase from Drosophila melanogaster.

    Science.gov (United States)

    Bauer, Holger; Massey, Vincent; Arscott, L David; Schirmer, R Heiner; Ballou, David P; Williams, Charles H

    2003-08-29

    Drosophila melanogaster thioredoxin reductase-1 (DmTrxR-1) is a key flavoenzyme in dipteran insects, where it substitutes for glutathione reductase. DmTrxR-1 belongs to the family of dimeric, high Mr thioredoxin reductases, which catalyze reduction of thioredoxin by NADPH. Thioredoxin reductase has an N-terminal redox-active disulfide (Cys57-Cys62) adjacent to the flavin and a redox-active C-terminal cysteine pair (Cys489'-Cys490' in the other subunit) that transfer electrons from Cys57-Cys62 to the substrate thioredoxin. Cys489'-Cys490' functions similarly to Cys495-Sec496 (Sec = selenocysteine) and Cys535-XXXX-Cys540 in human and parasite Plasmodium falciparum enzymes, but a catalytic redox center formed by adjacent Cys residues, as observed in DmTrxR-1, is unprecedented. Our data show, for the first time in a high Mr TrxR, that DmTrxR-1 oscillates between the 2-electron reduced state, EH2, and the 4-electron state, EH4, in catalysis, after the initial priming reduction of the oxidized enzyme (Eox) to EH2. The reductive half-reaction consumes 2 eq of NADPH in two observable steps to produce EH4. The first equivalent yields a FADH--NADP+ charge-transfer complex that reduces the adjacent disulfide to form a thiolate-flavin charge-transfer complex. EH4 reacts with thioredoxin rapidly to produce EH2. In contrast, Eox formation is slow and incomplete; thus, EH2 of wild-type cannot reduce thioredoxin at catalytically competent rates. Mutants lacking the C-terminal redox center, C489S, C490S, and C489S/C490S, are incapable of reducing thioredoxin and can only be reduced to EH2 forms. Additional data suggest that Cys57 attacks Cys490' in the interchange reaction between the N-terminal dithiol and the C-terminal disulfide. PMID:12816954

  14. Potentiation of antiherpetic activity of acyclovir by ribonucleotide reductase inhibition.

    OpenAIRE

    Spector, T.; Averett, D R; Nelson, D J; Lambe, C U; Morrison, R W; St Clair, M H; Furman, P A

    1985-01-01

    Compound A723U, a 2-acetylpyridine thiosemicarbazone, produced apparent inactivation of herpes simplex virus type 1 (HSV-1) ribonucleotide reductase. Inactivation occurred after A723U formed a reversible complex with the enzyme and only while the enzyme was catalyzing the formation of deoxynucleotides. A723U inhibited HSV-1 replication at concentrations that were not toxic to the confluent host cells. Most importantly, A723U and acyclovir (ACV) were found to exhibit mutual potentiation of the...

  15. Bcl2 induces DNA replication stress by inhibiting ribonucleotide reductase

    OpenAIRE

    Xie, Maohua; Yen, Yun; Owonikoko, Taofeek K.; Ramalingam, Suresh S.; Khuri, Fadlo R.; Curran, Walter J.; Doetsch, Paul W; Deng, Xingming

    2013-01-01

    DNA replication stress is an inefficient DNA synthesis process that leads replication forks to progress slowly or stall. Two main factors that cause replication stress are alterations in pools of deoxyribonucleotide (dNTP) precursors required for DNA synthesis and changes in the activity of proteins required for synthesis of dNTPs. Ribonucleotide reductase (RNR), containing regulatory hRRM1 and catalytic hRRM2 subunits, is the enzyme that catalyzes the conversion of ribonucleoside diphosphate...

  16. Regulation of ribonucleotide reductase by Spd1 involves multiple mechanisms

    OpenAIRE

    Nestoras, Konstantinos; Mohammed, Asma Hadi; Schreurs, Ann-Sofie; Fleck, Oliver; Watson, Adam T.; Poitelea, Marius; O'Shea, Charlotte; Chahwan, Charly; Holmberg, Christian; Kragelund, Birthe B.; Nielsen, Olaf; Osborne, Mark; Carr, Antony M.; Liu, Cong

    2010-01-01

    The correct levels of deoxyribonucleotide triphosphates and their relative abundance are important to maintain genomic integrity. Ribonucleotide reductase (RNR) regulation is complex and multifaceted. RNR is regulated allosterically by two nucleotide-binding sites, by transcriptional control, and by small inhibitory proteins that associate with the R1 catalytic subunit. In addition, the subcellular localization of the R2 subunit is regulated through the cell cycle and in response to DNA damag...

  17. Binding of Natural and Synthetic Polyphenols to Human Dihydrofolate Reductase

    OpenAIRE

    José Neptuno Rodríguez-López; Juan Cabezas-Herrera; Soledad Chazarra; Luís Sánchez-del-Campo; Magalí Sáez-Ayala

    2009-01-01

    Dihydrofolate reductase (DHFR) is the subject of intensive investigation since it appears to be the primary target enzyme for antifolate drugs. Fluorescence quenching experiments show that the ester bond-containing tea polyphenols (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin gallate (ECG) are potent inhibitors of DHFR with dissociation constants (KD) of 0.9 and 1.8 ?M, respectively, while polyphenols lacking the ester bound gallate moiety [e.g., (-)-epigallocatechin (EGC) and (-)-e...

  18. Characterization of Binding Pocket Flexibility of Aldose Reductase

    OpenAIRE

    Zentgraf, Matthias

    2006-01-01

    Aldose Reductase (AR) is the first enzyme of the 'sorbitol pathway'. It is an NADPH dependent enzyme and catalyzes the reduction of various aldehydes to the corresponding alcohols. Its binding pocket shows intrinsic flexibility which is mainly mediated by a small loop region. A specificity pocket can be opened or closed via this loop stretch. In the first part of this work the relevance of considering protein flexibility in ...

  19. Current Status of 5?-Reductase Inhibitors in Prostate Disease Management

    OpenAIRE

    Kang, Dong Il; Chung, Jae Il

    2013-01-01

    The key enzyme in the androgen synthesis and androgen receptor pathways is 5?-reductase (5-AR), which occurs as three isoenzymes. Types I and II 5-ARs the most important clinically, and two different 5-AR inhibitors (5-ARIs), finasteride and dutasteride, have been developed. Several urology associations have recommended and upgraded the use of 5-ARIs for an enlarged prostate with lower urinary tract symptoms. In the Prostate Cancer Prevention Trial and the Reduction by Dutasteride of Prostate...

  20. Modulation of tau phosphorylation within its microtubule-binding domain by cellular thiols.

    Science.gov (United States)

    Jenkins, S M; Johnson, G V

    1999-11-01

    Tau is a microtubule-stabilizing protein that is functionally modulated by alterations in its phosphorylation state. Because phosphorylation regulates both normal and pathological tau functioning, it is of importance to identify the signaling pathways that regulate tau phosphorylation in vivo. The present study examined changes in tau phosphorylation and function in response to modulation of cellular thiol content. Treatment of cells with phenylarsine oxide, which reacts with vicinal thiols, selectively increased tau phosphorylation within its microtubule-binding domain, at the non-Ser/Thr-Pro sites Ser262/356, while decreasing tau phosphorylation at Ser/ Thr-Pro sites outside this region. This increase in tau phosphorylation correlated with a decrease in the amount of tau associated with the cytoskeleton and decreased microtubule stability. Phenylarsine oxide-induced tau phosphorylation was inhibited by oxidants and by the protein kinase inhibitor staurosporine. Although staurosporine completely eliminated the increase in tau phosphorylation at Ser262/356, as detected by immunostaining with 12E8, it had a comparatively minor effect on the changes in tau localization induced by phenylarsine oxide. The results suggest that regulation of cellular thiols is important for modulating tau phosphorylation and function in situ. Additionally, although phosphorylation of Ser262/356 decreases tau's interaction with the cytoskeleton, phosphorylation of these residues alone is not sufficient for the phenylarsine oxide-induced changes in tau localization. PMID:10537042

  1. 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

  2. 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.

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

    Directory of Open Access Journals (Sweden)

    James R. Roede

    2013-01-01

    Full Text Available 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/CySS redox potential (EhCySS is associated with aging and disease risk in humans. The purpose of this study was to determine age-related changes in plasma redox metabolites and corresponding redox potentials (Eh to further validate the marmoset as a nonhuman primate model of aging. We measured plasma thiol redox states in marmosets and used existing human data with multivariate adaptive regression splines (MARS to model the relationships between age and redox metabolites. A classification accuracy of 70.2% and an AUC of 0.703 were achieved using the MARS model built from the marmoset redox data to classify the human samples as young or old. These results show that common marmosets provide a useful model for thiol redox biology of aging.

  4. Thiol-disulfide oxidoreductases are essential for the production of the lantibiotic sublancin 168.

    Science.gov (United States)

    Dorenbos, Ronald; Stein, Torsten; Kabel, Jorrit; Bruand, Claude; Bolhuis, Albert; Bron, Sierd; Quax, Wim J; Van Dijl, Jan Maarten

    2002-05-10

    Thiol-disulfide oxidoreductases are required for disulfide bond formation in proteins that are exported from the cytoplasm. Four enzymes of this type, termed BdbA, BdbB, BdbC, and BdbD, have been identified in the Gram-positive eubacterium Bacillus subtilis. BdbC and BdbD have been shown to be critical for the folding of a protein required for DNA uptake during natural competence. In contrast, no function has been assigned so far to the BdbA and BdbB proteins. The bdbA and bdbB genes are located in one operon that also contains the genes specifying the lantibiotic sublancin 168 and the ATP-binding cassette transporter SunT. Interestingly sublancin 168 contains two disulfide bonds. The present studies demonstrate that SunT and BdbB, but not BdbA, are required for the production of active sublancin 168. In addition, the BdbB paralogue BdbC is at least partly able to replace BdbB in sublancin 168 production. These observations show the unprecedented involvement of thiol-disulfide oxidoreductases in the synthesis of a peptide antibiotic. Notably BdbB cannot complement BdbC in competence development, showing that these two closely related thiol-disulfide oxidoreductases have different, but partly overlapping, substrate specificities. PMID:11872755

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

    Directory of Open Access Journals (Sweden)

    Claudio Larosa

    2009-09-01

    Full Text Available 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 size, was mixed according to a doping protocol employing different concentrations of thiol gold nanoparticles vs. polycarbonate. The presence of nanoparticles in the polymer films was confirmed by the spectrophotometric detection of the characteristic absorbance marker peak at 540–580 nm. The nanostructured films obtained show a better coverage in the UV-vis range (250–450 nm even at very low doping ratios, of the order of 1:1,000. These results offer a very promising approach towards the development of efficient nanostructured materials for applications to optical lenses.

  6. Rapid approach to biobased telechelics through two one-pot thiol-ene click reactions.

    Science.gov (United States)

    Lluch, Cristina; Ronda, Joan C; Galià, Marina; Lligadas, Gerard; Cádiz, Virginia

    2010-06-14

    The application of environmentally friendly thiol-ene chemistry to the preparation of biobased telechelics is presented in this work. This methodology is based on two one-pot photoinitiated thiol-ene click processes: step-growth polymerization using a 3,6-dioxa-1,8-octanedithiol and end-group postpolymerization modification with three functional thiols: 2-mercaptoethanol, 3-mercaptopropionic acid, and 3-mercaptopropyltrimethoxysilane. We applied this approach to a potentially 100% biomass-derived monomer, allyl ester of 10-undecenoic acid (UDA). To show the generality and scope of this methodology, a series of well-defined telechelics with molecular weight ranging from 1000-3000 g/mol and hydroxyl, carboxyl, or trimethoxysilyl groups at the polymer terminus were prepared. An exhaustive (1)H NMR and MALDI-TOF MS analyses demonstrates the highly end-group fidelity of this methodology being an interesting procedure for the accelerated preparation of telechelics derived from divinyl monomers. UDA-based thelechelic diol prepared using this methodology was reacted with 4,4'-methylenebis(phenylisocyanate) and 1,4-butanediol as the chain extender to obtain multiblock poly(ester urethane). PMID:20462176

  7. Building thiol and metal-thiolate functions into coordination nets: Clues from a simple molecule

    Science.gov (United States)

    He, Jun; Yang, Chen; Xu, Zhengtao; Zeller, Matthias; Hunter, Allen D.; Lin, Jianhua

    2009-07-01

    The simple and easy-to-prepare bifunctional molecule 2,5-dimercapto-1,4-benzenedicarboxylic acid (H 4DMBD) interacts with the increasingly harder metal ions of Cu +, Pb 2+ and Eu 3+ to form the coordination networks of Cu 6(DMBD) 3(en) 4(Hen) 6 ( 1), Pb 2(DMBD)(en) 2 ( 2) and Eu 2(H 2DMBD) 3(DEF) 4 ( 3), where the carboxyl and thiol groups bind with distinct preference to the hard and soft metal ions, respectively. Notably, 1 features uncoordinated carboxylate groups and Cu 3 cluster units integrated via the thiolate groups into an extended network with significant interaction between the metal centers and the organic molecules; 2 features a 2D coordination net based on the mercapto and carboxylic groups all bonded to the Pb 2+ ions; 3 features free-standing thiol groups inside the channels of a metal-carboxylate-based network. This study illustrates the rich solid state structural features and potential functions offered by the carboxyl-thiol combination.

  8. Thiol derivatization of Xanthan gum and its evaluation as a mucoadhesive polymer.

    Science.gov (United States)

    Bhatia, Meenakshi; Ahuja, Munish; Mehta, Heena

    2015-10-20

    Thiol-derivatization of xanthan gum polysaccharide was carried out by esterification with mercaptopropionic acid and thioglycolic acid. Thiol-derivatization was confirmed by Fourier-transformed infra-red spectroscopy. Xanthan-mercaptopropionic acid conjugate and xanthan-thioglycolic acid conjugate were found to possess 432.68mM and 465.02mM of thiol groups as determined by Ellman's method respectively. Comparative evaluation of mucoadhesive property of metronidazole loaded buccal pellets of xanthan and thiolated xanthan gum using chicken buccal pouch membrane revealed higher ex vivo bioadhesion time of thiolated xanthan gum as compared to xanthan gum. Improved mucoadhesive property of thiolated xanthan gum over the xanthan gum can be attributed to the formation of disulfide bond between mucus and thiolated xanthan gum. In vitro release study conducted using phosphate buffer (pH 6.8) revealed a sustained release profile of metronidazole from thiolated xanthan pellets as compared to xanthan pellets. In conclusion, thiolation of xanthan improves its mucoadhesive property and sustained the release of metronidazole over a prolonged period. PMID:26256167

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

    Directory of Open Access Journals (Sweden)

    Adam Nawrath

    2012-10-01

    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.

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

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Hvilsted, SØren

    2009-01-01

    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.

  11. Synthesis of thiol-functionalized spent grain as a novel adsorbent for divalent metal ions.

    Science.gov (United States)

    Chai, Liyuan; Li, Qingzhu; Zhu, Yonghua; Zhang, Zhiyuan; Wang, Qingwei; Wang, Yunyan; Yang, Zhihui

    2010-08-01

    Spent grain (SG) was functionalized with thioglycolic acid in N,N-dimethylformamide (DMF) medium using sodium bisulfate monohydrate (NaHSO(4).H(2)O) as a catalyst, followed by treatment with sodium sulfide nonahydrate (Na(2)S.9H(2)O). Characterization of thiol-functionalized spent grain (TFSG) was performed using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. These analytical results revealed the emergence of S-H and C=O groups after the chemical modification, indicating that thiol groups were successfully grafted onto TFSG. As compared with SG, TFSG showed significant improvement in terms of metal loading capacity. Typically, adsorption capacity for Zn(2+) was increased from 125.76 mg g(-1) of SG to 227.37 mg g(-1) of TFSG, which was confirmed by X-ray fluorescence (XRF) analysis. This increase may be attributed to both the formation of ester linkage and the grafting of thiol groups onto TFSG. The experimental results indicate that TFSG is a promising adsorbent for removal heavy metals from contaminated water. PMID:20338755

  12. Quantification of Polyfunctional Thiols in Wine by HS-SPME-GC-MS Following Extractive Alkylation

    Directory of Open Access Journals (Sweden)

    Lauren E. Musumeci

    2015-07-01

    Full Text Available Analyses of key odorous polyfunctional volatile thiols in wines (3-mercaptohexanol (3-MH, 3-mercaptohexylacetate (3-MHA, and 4-mercapto-4-methyl-2-pentanone (4-MMP are challenging due to their high reactivity and ultra-trace concentrations, especially when using conventional gas-chromatography electron impact mass spectrometry (GC-EI-MS. We describe a method in which thiols are converted to pentafluorobenzyl (PFB derivatives by extractive alkylation and the organic layer is evaporated prior to headspace solid phase microextraction (HS-SPME and GC-EI-MS analysis. Optimal parameters were determined by response surface area modeling. The addition of NaCl solution to the dried SPME vials prior to extraction resulted in up to less than fivefold improvement in detection limits. Using 40 mL wine samples, limits of detection for 4-MMP, 3-MH, and 3-MHA were 0.9 ng/L, 1 ng/L, and 17 ng/L, respectively. Good recovery (90%–109% and precision (5%–11% RSD were achieved in wine matrices. The new method was used to survey polyfunctional thiol concentrations in 61 commercial California and New York State wines produced from V. vinifera (Riesling, Gewürztraminer, Cabernet Sauvignon, Sauvignon blanc and non-varietal rosé wines, V. labruscana (Niagara, and Vitis spp. (Cayuga White. Mean 4-MMP concentrations in New York Niagara (17 ng/L were not significantly different from concentrations in Sauvignon blanc, but were significantly higher than 4-MMP in other varietal wines.

  13. A new turn-on chemosensor for bio-thiols based on the nanoaggregates of a tetraphenylethene-coumarin fluorophore

    Science.gov (United States)

    Lou, Xiaoding; Zhao, Zujin; Hong, Yuning; Dong, Chao; Min, Xuehong; Zhuang, Yuan; Xu, Xuemei; Jia, Yongmei; Xia, Fan; Tang, Ben Zhong

    2014-11-01

    In this work, a tetraphenylethene-coumarin hybrid fluorophore (TPE-Cou) that contains a Schiff base form is designed and synthesized. A combination of plentiful optical properties and chemical reactivity towards thiols allows TPE-Cou to work as an excellent turn-on probe of thiols with a wide linear range, revealing the great potential of this dye as a quantitative fluorescence indicator. By means of NMR and optical spectrum analyses, a mechanistic picture at the molecular level has been drawn to illustrate how this dye works as a bio-thiol-sensitive fluorescent probe.In this work, a tetraphenylethene-coumarin hybrid fluorophore (TPE-Cou) that contains a Schiff base form is designed and synthesized. A combination of plentiful optical properties and chemical reactivity towards thiols allows TPE-Cou to work as an excellent turn-on probe of thiols with a wide linear range, revealing the great potential of this dye as a quantitative fluorescence indicator. By means of NMR and optical spectrum analyses, a mechanistic picture at the molecular level has been drawn to illustrate how this dye works as a bio-thiol-sensitive fluorescent probe. Electronic supplementary information (ESI) available: Details of the experimental procedure and analytical data are provided. See DOI: 10.1039/c4nr04593a

  14. Functional diversity of cysteine residues in proteins and unique features of catalytic redox-active cysteines in thiol oxidoreductases.

    Science.gov (United States)

    Fomenko, Dmitri E; Marino, Stefano M; Gladyshev, Vadim N

    2008-09-30

    Thiol-dependent redox systems are involved in regulation of diverse biological processes, such as response to stress, signal transduction, and protein folding. The thiol-based redox control is provided by mechanistically similar, but structurally distinct families of enzymes known as thiol oxidoreductases. Many such enzymes have been characterized, but identities and functions of the entire sets of thiol oxidoreductases in organisms are not known. Extreme sequence and structural divergence makes identification of these proteins difficult. Thiol oxidoreductases contain a redox-active cysteine residue, or its functional analog selenocysteine, in their active sites. Here, we describe computational methods for in silico prediction of thiol oxidoreductases in nucleotide and protein sequence databases and identification of their redox-active cysteines. We discuss different functional categories of cysteine residues, describe methods for discrimination between catalytic and noncatalytic and between redox and non-redox cysteine residues and highlight unique properties of the redox-active cysteines based on evolutionary conservation, secondary and three-dimensional structures, and sporadic replacement of cysteines with catalytically superior selenocysteine residues. PMID:18648218

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

    CERN Document Server

    Demir, Firuz

    2012-01-01

    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 ...

  16. Highly Selective Fluorescent Turn-On Probe for Protein Thiols in Biotin Receptor-Positive Cancer Cells.

    Science.gov (United States)

    Sun, Qian; Sun, Deheng; Song, Lun; Chen, Zhuo; Chen, Zhaoyang; Zhang, Weibing; Qian, Junhong

    2016-03-15

    Sulfhydryl-containing proteins play critical roles in various physiological and biological processes, and the activities of those proteins have been reported to be susceptible to thiol oxidation. Therefore, the development of protein thiol target fluorescent probe is highly desirable. In the present work, a biotinylated coumarin fluorescence "off-on" probe SQ for selectively detecting protein thiols in biotin receptor-positive cancer cells was designed with a 2,4-dinitrobenzenesulfony as the thiol receptor. The probe exhibited dramatic fluorescence responses toward sulfhydryl-containing proteins (ovalbumin (OVA), bovine serum albumin (BSA)): up to 170-fold fluorescence enhancement with 70 nm blue-shift was observed with the addition of OVA. However, low molecular weight thiols (Cys, glutathione (GSH), Hcy) caused negligible fluorescence changes of SQ. In addition, biotin receptor-positive Hela cells displayed strong red and green fluorescence after incubation of SQ for 1 h; neither red nor green fluorescence signal could be visualized in biotin-negative normal lung Wi38 cells. These results imply that the probe has potential application in fluorescent imaging protein thiols on the surface of Hela cells. PMID:26902836

  17. Resin-assisted enrichment of thiols as a general strategy for proteomic profiling of cysteine-based reversible modifications

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Jia [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gaffrey, Matthew J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Su, Dian [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Genentech Inc., South San Francisco, CA (United States); Liu, Tao [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Camp, David G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Smith, Richard D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qian, Weijun [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-12-12

    Reversible modifications on cysteine thiols play a significant role in redox signaling and regulation. A number of reversible redox modifications, including disulfide formation, S-nitrosylation, and S-glutathionylation, have been recognized for their significance in various physiological and pathological processes. Here we describe in detail a resin-assisted thiol-affinity enrichment protocol for both biochemical and proteomics applications. This protocol serves as a general approach for specific isolation of thiol-containing proteins or peptides derived from reversible redox-modified proteins. This approach utilizes thiol-affinity resins to directly capture thiol-containing proteins or peptides through a disulfide exchange reaction followed by on-resin protein digestion and on-resin multiplexed isobaric labeling to facilitate LC-MS/MS based quantitative site-specific analysis of redox modifications. The overall approach requires a much simpler workflow with increased specificity compared to the commonly used biotin switch technique. By coupling different selective reduction strategies, the resin-assisted approach provides the researcher with a useful tool capable of enriching different types of reversible modifications on protein thiols. Procedures for selective enrichment and analyses of S-nitrosylation and total reversible cysteine oxidation are presented to demonstrate the utility of this general strategy.

  18. para-sulfobenzoyloxybromobimane: a new membrane-impermeable reagent useful for the analysis of thiols and their export from cells.

    Science.gov (United States)

    Newton, G L; Aguilera, J A; Fahey, R C; Ward, J F; Radkowsky, A E; Kosower, E M

    1992-02-14

    para-Sulfonylbenzoyloxybromobimane (sBBr) was shown to be similar to the fluorescent labeling agent monobromobimane (mBBr) in reacting rapidly and selectively with thiols to produce stable derivatives which are readily separated by HPLC. Chromatography of the sBBr derivative provides a useful means of confirming the identification of an unknown thiol based upon the chromatography of its mBBr derivative and can be useful for quantitative determination of polycationic thiols for which chromatography of the mBBr derivative is unsatisfactory. Unlike mBBr, which readily penetrates cells, sBBr was found not to be taken up by cells. These characteristics allow sBBr to be used, in conjunction with mBBr, to quantify the export of thiols from cells, as illustrated for GSH and the radioprotective drug WR1065, from V79 cells. Simultaneous determination of GSH and glutathione disulfides in cell culture medium could be achieved by labeling of thiols with sBBr followed by reduction of disulfides with dithiothreitol, labeling of the resulting thiols with mBBr, and HPLC analysis for both glutathione derivatives. PMID:1621960

  19. Structural and functional diversity of ferredoxin-NADP(+) reductases.

    Science.gov (United States)

    Aliverti, Alessandro; Pandini, Vittorio; Pennati, Andrea; de Rosa, Matteo; Zanetti, Giuliana

    2008-06-15

    Although all ferredoxin-NADP(+) reductases (FNRs) catalyze the same reaction, i.e. the transfer of reducing equivalents between NADP(H) and ferredoxin, they belong to two unrelated families of proteins: the plant-type and the glutathione reductase-type of FNRs. Aim of this review is to provide a general classification scheme for these enzymes, to be used as a framework for the comparison of their properties. Furthermore, we report on some recent findings, which significantly increased the understanding of the structure-function relationships of FNRs, i.e. the ability of adrenodoxin reductase and its homologs to catalyze the oxidation of NADP(+) to its 4-oxo derivative, and the properties of plant-type FNRs from non-photosynthetic organisms. Plant-type FNRs from bacteria and Apicomplexan parasites provide examples of novel ways of FAD- and NADP(H)-binding. The recent characterization of an FNR from Plasmodium falciparum brings these enzymes into the field of drug design. PMID:18307973

  20. Cloning and sequence of the human adrenodoxin reductase gene

    International Nuclear Information System (INIS)

    Adrenodoxin reductase is a flavoprotein mediating electron transport to all mitochondrial forms of cytochrome P450. The authors 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 peptide and the apparent FAD binding site. The remaining 10 exons are clustered in a region of only 4.3 kilobases, separated from the first two exons by a large intron of about 5.6 kilobases. Two forms of human adrenodoxin reductase mRNA, differing by the presence or absence of 18 bases in the middle of the sequence, arise from alternate splicing at the 5' end of exon 7. This alternately spliced region is directly adjacent to the NADPH binding site, which is entirely contained in exon 6. The immediate 5' flanking region lacks TATA and CAAT boxes; however, this region is rich in G+C and contains six copies of the sequence GGGCGGG, resembling promoter sequences of housekeeping genes. RNase protection experiments show that transcription is initiated from multiple sites in the 5' flanking region, located about 21-91 base pairs upstream from the AUG translational initiation codon

  1. The occurrence of nitrate reductase in leaves of prunus species.

    Science.gov (United States)

    Leece, D R; Dilley, D R; Kenworthy, A L

    1972-05-01

    Nitrate reductase was found in leaves of apricot Prunus armeniaca, sour cherry P. cerasus, sweet cherry P. avium, and plum P. domestica, but not in peach P. persica, from trees grown in sand culture receiving a nitrate containing nutrient solution. Nitrate was found in the leaves of all species. Nitrate and nitrate reductase were found in leaves of field-grown apricot, sour cherry, and plum trees. The enzyme-extracting medium contained insoluble polyvinylpyrrolidone, and including dithiothreitol or mercaptobenzothiazole did not improve enzyme recovery. Inclusion of cherry leaf extract diminished, and peach leaf extract abolished, recovery of nitrate reductase from oat tissue. Low molecular weight phenols liberated during extraction were probably responsible for inactivation of the enzyme. The enzyme from apricot was two to three times as active as from the other species. Both nicotine adenine diphosphopyridine nucleotide and flavin mononucleotide were effective electron donors. The enzyme was readily induced in apricot leaves by 10 mm nitrate supplied through the leaf petiole. PMID:16658037

  2. Nitrate reductase gene involvement in hexachlorobiphenyl dechlorination by Phanerochaete chrysosporium

    International Nuclear Information System (INIS)

    Polychlorobiphenyl (PCB) degradation usually occurs through reductive dechlorination under anaerobic conditions and phenolic ring cleavage under aerobic conditions. In this paper, we provide evidence of nitrate reductase (NaR) mediated dechlorination of hexachlorobiphenyl (PCB-153) in Phanerochaete chrysosporium under non-ligninolytic condition and the gene involved. The NaR enzyme and its cofactor, molybdenum (Mo), were found to mediate reductive dechlorination of PCBs even in aerobic condition. Tungsten (W), a competitive inhibitor of this enzyme, was found to suppress this dechlorination. Chlorine release assay provided further evidence of this nitrate reductase mediated dechlorination. Commercially available pure NaR enzyme from Aspergillus was used to confirm these results. Through homology search using TBLASTN program, NaR gene was identified, primers were designed and the RT-PCR product was sequenced. The NaR gene was then annotated in the P. chrysosporium genome (GenBank accession no. AY700576). This is the first report regarding the presence of nitrate reductase gene in this fungus with the explanation why this fungus can dechlorinate PCBs even in aerobic condition. These fungal inoculums are used commercially as pellets in sawdust for enhanced bioremediation of PCBs at the risk of depleting soil nitrates. Hence, the addition of nitrates to the pellets will reduce this risk as well as enhance its activity

  3. Characterization of a salt-induced DhAHP, a gene coding for alkyl hydroperoxide reductase, from the extremely halophilic yeast Debaryomyces hansenii

    Directory of Open Access Journals (Sweden)

    Ku Maurice SB

    2009-08-01

    Full Text Available Abstract Background Debaryomyces hansenii is one of the most salt tolerant species of yeast and has become a model organism for the study of tolerance mechanisms against salinity. The goal of this study was to identify key upregulated genes that are involved in its adaptation to high salinity. Results By using forward subtractive hybridization we have cloned and sequenced DhAHP from D. hansenii that is significantly upregulated during salinity stress. DhAHP is orthologous to the alkly hydroperoxide reductase of the peroxiredoxin gene family, which catalyzes the reduction of peroxides at the expense of thiol compounds. The full-lengthed cDNA of DhAHP has 674 bp of nucleotide and contains a 516 bp open reading frame (ORF encoding a deduced protein of 172 amino acid residues (18.3 kDa. D. hansenii Ahp is a cytosolic protein that belongs to the Ahp of the 1-Cys type peroxiredoxins. Phylogentically, the DhAhp and Candida albicans Ahp11 (Swiss-Prot: Q5AF44 share a common ancestry but show divergent evolution. Silence of its expression in D. hansenii by RNAi resulted in decreased tolerance to salt whereas overexpression of DhAHP in D. hansenii and the salt-sensitive yeasts Saccharomyces cereviasiae and Pichia methanolica conferred a higher tolerance with a reduced level of reactive oxygen species. Conclusion In conclusion, for the first time our study has identified alkly hydroperoxide reductase as a key protein involved in the salt tolerance of the extremely halophilic D. hansenii. Apparently, this enzyme plays a multi-functional role in the yeast's adaptation to salinity; it serves as a peroxidase in scavenging reactive oxygen species, as a molecular chaperone in protecting essential proteins from denaturation, and as a redox sensor in regulating H2O2-mediated cell defense signaling.

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

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Hvilsted, SØren

    2008-01-01

    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.

  5. POTENTIOMETRIC RESPONSE OF A GRAPHITE ELECTRODE MODIFIED WITH COBALT PHTHALOCYANINE FOR THIOLS AND DISULFIDES

    Directory of Open Access Journals (Sweden)

    JOSÉ H. ZAGAL

    2000-06-01

    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

  6. Analysis of nitrate reductase mRNA expression and nitrate reductase activity in response to nitrogen supply

    Directory of Open Access Journals (Sweden)

    Gholamreza Kavoosi

    2014-06-01

    Full Text Available Nitrate is one of the major sources of nitrogen for the growth of plants. It is taken up by plant roots and transported to the leaves where it is reduced to nitrite in the. The main objective of this research was to investigate stimulatory effects of sodium nitrate, potassium nitrate, ammonia and urea on the production/generation of the nitrate reductase mRNA in Triticum aestivum plants. The plants were grown in standard nutrient solution for 21 days and then starved in a media without nitrate for seven days. Starved plants were stimulated with various concentrations of sodium nitrate, potassium nitrate, ammonia and urea, and the expression of nitrate reductase mRNA was analyzed by real-time PCR. Our results indicated that starvation caused significant decrease in the production of nitrate reductase mRNA in the plant leaf. Sodium and potassium nitrate were capable of restoring the production of nitrate mRNA in a dose-dependent manner, since 50 mM of each produced the highest level of the mRNA. The stimulatory effect of potassium nitrate was higher than sodium nitrate, while ammonia and urea did not show such activity. At low concentrations, sodium nitrate and potassium nitrate caused significant increase in the nitrate/nitrite mRNA production, whereas high concentrations of these salts suppressed the expression of this gene considerably.

  7. Characterization and regulation of Leishmania major 3-hydroxy-3-methylglutaryl-CoA reductase

    DEFF Research Database (Denmark)

    Montalvetti, A; Pena Diaz, Javier; Hurtado, R; Ruiz-Pérez, L M; González-Pacanowska, D

    In eukaryotes the enzyme 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase catalyses the synthesis of mevalonic acid, a common precursor to all isoprenoid compounds. Here we report the isolation and overexpression of the gene coding for HMG-CoA reductase from Leishmania major. The protein from L...... the amount of reductase protein. Western- and Northern-blot analyses indicate that this activation is apparently performed via post-transcriptional control....

  8. Localization of the cytochrome cd1 and copper nitrite reductases in denitrifying bacteria.

    OpenAIRE

    Coyne, M S; Arunakumari, A; Pankratz, H S; Tiedje, J. M.

    1990-01-01

    The locations of cytochrome cd1 nitrite reductases in Pseudomonas aeruginosa and Pseudomonas fluorescens and copper nitrite reductases in Achromobacter cycloclastes and Achromobacter xylosoxidans were identified. Immunogold labeling with colloidal-gold probes showed that the nitrite reductases were synthesized exclusively in anaerobically grown (denitrifying) cells. Little immunogold label occurred in the cytoplasm of these four strains; most was found in the periplasmic space or was associat...

  9. Characterization and regulation of the gene encoding nitrite reductase in Rhodobacter sphaeroides 2.4.3.

    OpenAIRE

    Tosques, I E; Kwiatkowski, A V; Shi, J.; Shapleigh, J P

    1997-01-01

    Nitrite reductase catalyzes the reduction of nitrite to nitric oxide, the first step in denitrification to produce a gaseous product. We have cloned the gene nirK, which encodes the copper-type nitrite reductase from a denitrifying variant of Rhodobacter sphaeroides, strain 2.4.3. The deduced open reading frame has significant identity with other copper-type nitrite reductases. Analysis of the promoter region shows that transcription initiates 31 bases upstream of the translation start codon....

  10. Sucrose mimics the light induction of Arabidopsis nitrate reductase gene transcription.

    OpenAIRE

    Cheng, C. L.; Acedo, G N; Cristinsin, M; Conkling, M.A.

    1992-01-01

    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 migh...

  11. Expression Cloning and Regulation of Steroid 5?-Reductase, an Enzyme Essential for Male Sexual Differentiation*

    OpenAIRE

    Andersson, Stefan; Bishop, Richard W.; RUSSELL, DAVID W.

    1989-01-01

    The conversion of testosterone into the more potent androgen, dihydrotestosterone, catalyzed by the enzyme steroid 5?-reductase, is required for the differentiation of male external genitalia. Here, we report the isolation of cDNA clones encoding the rat steroid 5?-reductase using expression cloning in Xenopus oocytes. DNA sequence analysis demonstrates that the liver and ventral prostate forms of steroid 5?-reductase are identical hydrophobic proteins of 29 kDa. The amount of steroid 5?-redu...

  12. CATALYTIC ADVANTAGES PROVIDED BY SELENOCYSTEINE IN METHIONINE-S-SULFOXIDE REDUCTASES†

    OpenAIRE

    Kim, Hwa-Young; Fomenko, Dmitri E; Yoon, Yeo-Eun; GLADYSHEV, Vadim N.

    2006-01-01

    Methionine sulfoxide reductases are key enzymes that repair oxidatively damaged proteins. Two distinct stereospecific enzyme families are responsible for this function: MsrA (methionine-S-sulfoxide reductase) and MsrB (methionine-R-sulfoxide reductase). In the present study, we identified multiple selenoprotein MsrA sequences in organisms from bacteria to animals. We characterized the selenocysteine (Sec)-containing Chlamydomonas MsrA and found that this protein exhibited 10–50-fold higher ac...

  13. Enhanced dihydroflavonol-4-reductase activity and NAD homeostasis leading to cell death tolerance in transgenic rice

    OpenAIRE

    Hayashi, Mitsunori; TAKAHASHI, HIDEYUKI; Tamura, Katsunori; Huang, Jirong; Yu, Li-hua; KAWAI-YAMADA, MAKI; Tezuka, Takafumi; UCHIMIYA, HIROFUMI

    2005-01-01

    The maize Hm1 gene encoding the NADPH-dependent HC-toxin reductase is capable of detoxifying HC-toxin of fungus Cochliobolus carbonum. Here, we conducted the metabolic and biochemical analysis in transgenic rice plants overexpressing an HC-toxin reductase-like gene in rice (YK1 gene). Methods employing NADPH oxidation and capillary electrophoresis mass spectrometry analysis confirmed that YK1 possessed dihydroflavonol-4-reductase activity in vitro and in vivo. The overexpression of YK1 in bot...

  14. Sucrose mimics the light induction of Arabidopsis nitrate reductase gene transcription

    DEFF Research Database (Denmark)

    Cheng, Chi-Lien; Acedo, Gregoria N; Kristensen, Michael; Conkling, Mark A

    1992-01-01

    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 p...

  15. Identification of the 7-hydroxymethyl chlorophyll a reductase of the chlorophyll cycle in Arabidopsis.

    Science.gov (United States)

    Meguro, Miki; Ito, Hisashi; Takabayashi, Atsushi; Tanaka, Ryouichi; Tanaka, Ayumi

    2011-09-01

    The interconversion of chlorophyll a and chlorophyll b, referred to as the chlorophyll cycle, plays a crucial role in the processes of greening, acclimation to light intensity, and senescence. The chlorophyll cycle consists of three reactions: the conversions of chlorophyll a to chlorophyll b by chlorophyllide a oxygenase, chlorophyll b to 7-hydroxymethyl chlorophyll a by chlorophyll b reductase, and 7-hydroxymethyl chlorophyll a to chlorophyll a by 7-hydroxymethyl chlorophyll a reductase. We identified 7-hydroxymethyl chlorophyll a reductase, which is the last remaining unidentified enzyme of the chlorophyll cycle, from Arabidopsis thaliana by genetic and biochemical methods. Recombinant 7-hydroxymethyl chlorophyll a reductase converted 7-hydroxymethyl chlorophyll a to chlorophyll a using ferredoxin. Both sequence and biochemical analyses showed that 7-hydroxymethyl chlorophyll a reductase contains flavin adenine dinucleotide and an iron-sulfur center. In addition, a phylogenetic analysis elucidated the evolution of 7-hydroxymethyl chlorophyll a reductase from divinyl chlorophyllide vinyl reductase. A mutant lacking 7-hydroxymethyl chlorophyll a reductase was found to accumulate 7-hydroxymethyl chlorophyll a and pheophorbide a. Furthermore, this accumulation of pheophorbide a in the mutant was rescued by the inactivation of the chlorophyll b reductase gene. The downregulation of pheophorbide a oxygenase activity is discussed in relation to 7-hydroxymethyl chlorophyll a accumulation. PMID:21934147

  16. Structure of the Molybdenum Site of EEcherichia Coli Trimethylamine N-Oxide Reductase

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, L.; Nelson, K.Johnson; Rajagopalan, K.V.; George, G.N.

    2009-05-28

    We report a structural characterization of the molybdenum site of recombinant Escherichia coli trimethylamine N-oxide (TMAO) reductase using X-ray absorption spectroscopy. The enzyme active site shows considerable similarity to that of dimethyl sulfoxide (DMSO) reductase, in that, like DMSO reductase, the TMAO reductase active site can exist in multiple forms. Examination of the published crystal structure of TMAO oxidase from Shewanella massilia indicates that the postulated Mo coordination structure is chemically impossible. The presence of multiple active site structures provides a potential explanation for the anomalous features reported from the crystal structure.

  17. Properties of the NAD(P)H-dependent xylose reductase from the xylosefermenting yeast Pichia stipitis:

    OpenAIRE

    Verduyn, C.; Van Kleef, R.; Frank Jzn, J.; Schreuder, H.; van Dijken, J P; Scheffers, W A

    1985-01-01

    Xylose reductase from the xylose-fermenting yeast Pichia stipitis was purified to electrophoretic and spectral homogeneity via ion-exchange, affinity and highperformance gel chromatography. The enzyme was active with various aldose substrates, such as DL-glyceraldehyde, L-arabinose, D-xylose, D-ribose, D-galactose and D-glucose. Hence the xylose reductase of Pichia stipitis is an aldose reductase (EC 1.1. 1.21). Unlike all aldose reductases characterized so far, the enzyme from this yeast ...

  18. Study on the method of 5?-reductase type 2 gene expression and its distribution in epididymis

    International Nuclear Information System (INIS)

    Objective: To study the gene expression method of 5?-reductase isozymes type 2 and the distribution of mRNA in the regions of epididymis. Methods: The authors extracted the total RNA through guanidinium, synthesized ?-32P-cDNA probe of 5?-reductase type 2 and determined the changes of gene expression in the regions of epididymis using Northern blot. Results: All parts of the epididymis expressed 5?-reductase type 2 gene, but the expression levels of 5?-reductase in caput was higher than that of corpus and cauda. Conclusion: The higher level of expression in caput and corpus may be relative to its function

  19. Influence of extra-cellular and intra-cellular acting thiol oxidants on the 45calcium 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)

  20. Hypothiocyanous acid reactivity with low-molecular-mass and protein thiols: absolute rate constants and assessment of biological relevance.

    Science.gov (United States)

    Skaff, Ojia; Pattison, David I; Davies, Michael J

    2009-08-15

    MPO (myeloperoxidase) catalyses the oxidation of chloride, bromide and thiocyanate by H(2)O(2) to HOCl (hypochlorous acid), HOBr (hypobromous acid) and HOSCN (hypothiocyanous acid, also know as cyanosulfenic acid) respectively. Specificity constants indicate that thiocyanate, SCN-, is a major substrate for MPO. HOSCN is also a major oxidant generated by other peroxidases including salivary, gastric and eosinophil peroxidases. Whereas HOCl and HOBr are powerful oxidizing agents, HOSCN appears to be a less reactive, but more thiol-specific oxidant. Although it is established that HOSCN selectively targets thiols, absolute kinetic data for the reactions of thiols with HOSCN are absent from the literature. This study shows for the first time that the reactions of HOSCN with low-molecular-mass thiol residues occur with rate constants in the range from 7.3 x 10(3) M(-1).s(-1) (for N-acetyl-cysteine at pH 7.4) to 7.7 x 10(6) M(-1).s(-1) (for 5-thio-2-nitrobenzoic acid at pH 6.0). An inverse relationship between the rate of reaction and the pKa of the thiol group was observed. The rates of reaction of HOSCN with thiol-containing proteins were also investigated for four proteins (creatine kinase, BSA, beta-lactoglobulin and beta-L-crystallins). The values obtained for cysteine residues on these proteins are in the range 1 x 10(4)- 7 x 10(4) M(-1).s(-1). These second-order rate constants indicate that HOSCN is a major mediator of thiol oxidation in biological systems exposed to peroxidase/H(2)O(2) systems at (patho)physiological concentrations of halide and SCN- ions, and that HOSCN may play an important role in inflammation-induced oxidative damage. PMID:19492988

  1. biliverdin. Is there a role for biliverdin reductase?

    Directory of Open Access Journals (Sweden)

    AndreasDaiber

    2012-03-01

    Full Text Available Reactive oxygen species (ROS and signaling events are involved in the pathogenesis of endothelial dysfunction and represent a major contribution to vascular regulation. Molecular signaling is highly dependent on reactive oxygen species. But depending on the amount of ROS production it might have toxic or protective effects. Despite a large number of negative outcomes in large clinical trials (e.g. HOPE, HOPE-TOO, antioxidant molecules and agents are important players to influence the critical balance between production and elimination of RONS. However, chronic systemic antioxidant therapy lacks clinical efficacy, probably by interfering with important physiological redox signaling pathways. Therefore, it may be a much more promising attempt to induce intrinsic antioxidant pathways in order to increase the antioxidants not systemically but at the place of oxidative stress and complications. Among others, heme oxygenase (HO has been shown to be important for attenuating the overall production of ROS in a broad range of disease states through its ability to degrade heme and to produce carbon monoxide (CO, biliverdin/bilirubin, and the release of free iron with subsequent ferritin induction. With the present review we would like to highlight the important antioxidant role of the heme oxygenase system and especially discuss the contribution of the biliverdin, bilirubin and biliverdin reductase to these beneficial effects. The bilierdin reductase was reported to confer an antioxidant redox amplification cycle by which low, physiological bilirubin concentrations confer potent antioxidant protection via recycling of biliverdin from oxidized bilirubin by the biliverdin reductase, linking this sink for oxidants to the NADPH pool. To date the existence and role of this antioxidant redox cycle is still under debate and we present and discuss the pros and cons as well as our own findings on this topic.

  2. Synthesis and characterization of thiol-ene functionalized siloxanes and evaluation of their polymerization kinetics, network properties, and dental applications

    Science.gov (United States)

    Cole, Megan A.

    We explored formation-structure-property relationships in thiol-ene functionalized oligosiloxanes to create crosslinked networks. Specifically, nine oligomers were synthesized, three with thiol-functional silane repeats and three with allyl-functional silane repeats. Structural variations in each oligomer were systematically induced through the incorporation of non-reactive repeats bearing either diphenyl or di-n-octyl moieties, and the oligomer molecular weight was limited by the presence of monofunctional silane condensation species. The molecular weights and chain compositions of all oligomers were ascertained and subsequently used in the evaluation of network properties formed upon photopolymerization of thiol- and ene-functional reactants. Polymerization kinetics of the thiol-ene functionalized siloxanes were also investigated using photoinitiation owing to the spatial and temporal control afforded by this technique. In particular, the effects of the viscosity of the ene-functionalized oligomer and the degree of thiol functionalization on the observed polymerization rate were determined. Results showed that the speed of polymerization varied with changes to the rate-limiting step, which was heavily influenced by neighboring non-reactive functionalities. Moreover, the thiol-ene reaction was found to exhibity unimolecular termination exclusively in siloxane-based systems. Proposed use of the thiol-ene functionalized siloxane system as a dental impression material necessitated the development of a redox initiation scheme. Evaluation of the benzoylperoxide/dimethyl-p-toluidine redox pair in traditional systems showed bulk thiol-ene polymerizations comparable to photoinitiation with the added advantage of uninhibited depth control, as also demonstrated in small molecule thiol-ene coupling reactions initiated by this same redox system. Application of the redox pair to the siloxane system allowed for the viscoelastic properties as well as the feature replication abilities to be compared against commercial impression materials. The siloxane system was found to match the commercial material for strain recovery and stress relaxation and exceed its replication properties though it would require greater overall strength to function adequately in the clinical setting.

  3. Regulation of ribonucleotide reductase by Spd1 involves multiple mechanisms

    DEFF Research Database (Denmark)

    Nestoras, Konstantinos; Mohammed, Asma Hadi; Schreurs, Ann-Sofie; Fleck, Oliver; Watson, Adam T; Poitelea, Marius; O'Shea, Charlotte; Chahwan, Charly; Holmberg, Christian; Kragelund, Birthe B; Nielsen, Olaf; Osborne, Mark; Carr, Antony M; Liu, Cong

    2010-01-01

    The correct levels of deoxyribonucleotide triphosphates and their relative abundance are important to maintain genomic integrity. Ribonucleotide reductase (RNR) regulation is complex and multifaceted. RNR is regulated allosterically by two nucleotide-binding sites, by transcriptional control, and......2 nuclear import, as predicted by its relationship to Saccharomyces cerevisiae Dif1. We demonstrate that Spd1 can interact with both R1 and R2, and show that the major restraint of RNR in vivo by Spd1 is unrelated to R2 subcellular localization. Finally, we identify a new behavior for RNR complexes...

  4. Methylenetetrahydrofolate Reductase C677T: Hypoplastic Left Heart and Thrombosis.

    Science.gov (United States)

    Spronk, Kimberly J; Olivero, Anthony D; Haw, Marcus P; Vettukattil, Joseph J

    2015-10-01

    The incidence of congenital heart defects is higher in infants with mutation of methylenetetrahydrofolate reductase (MTHFR) gene. The MTHFR C677T gene decreases the bioavailability of folate and increases plasma homocysteine, a risk factor for thrombosis. There have been no reported cases in the literature on the clinical implications of this procoagulable state in the setting of cyanotic heart disease, which itself has prothrombotic predisposition. Two patients with hypoplastic left heart syndrome developed postoperative thrombotic complications, both were homozygous for MTHFR C677T. We present these cases and highlight the implications of MTHFR mutation in the management of complex congenital heart disease. PMID:26467879

  5. Vibrio harveyi Nitroreductase Is Also a Chromate Reductase

    OpenAIRE

    Kwak, Young Hak; Lee, Dong Seok; Kim, Han Bok

    2003-01-01

    The chromate reductase purified from Pseudomonas ambigua was found to be homologous with several nitroreductases. Escherichia coli DH5? and Vibrio harveyi KCTC 2720 nitroreductases were chosen for the present study, and their chromate-reducing activities were determined. A fusion between glutathione S-transferase (GST) and E. coli DH5? NfsA (GST-EcNfsA), a fusion between GST and E. coli DH5? NfsB (GST-EcNfsB), and a fusion between GST and V. harveyi KCTC 2720 NfsA (GST-VhNfsA) were prepared f...

  6. Methylenetetrahydrofolate reductase (MTHFR) deficiency presenting as a rash.

    LENUS (Irish Health Repository)

    Crushell, Ellen

    2012-09-01

    We report on the case of a 2-year-old girl recently diagnosed with Methylenetetrahydrofolate reductase (MTHFR) deficiency who originally presented in the neonatal period with a distinctive rash. At 11 weeks of age she developed seizures, she had acquired microcephaly and developmental delay. The rash deteriorated dramatically following commencement of phenobarbitone; both rash and seizures abated following empiric introduction of pyridoxine and folinic acid as treatment of possible vitamin responsive seizures. We postulate that phenobarbitone in combination with MTHFR deficiency may have caused her rash to deteriorate and subsequent folinic acid was helpful in treating the rash and preventing further acute neurological decline as commonly associated with this condition.

  7. PURIFICATION AND CHARACTERIZATION OF GLUTATHIONE REDUCTASE FROM TURKEY LIVER

    OpenAIRE

    liver, Purification and characterization of glu

    2012-01-01

    This study aimed to purify glutathione reductase (GR) from turkey liver and investigate some of its characteristic features. The purification procedure comprised 2 steps: homogenate preparation and 2',5'-ADP Sepharose 4B affinity gel chromatography. Thanks to the 2 consecutive procedures, the enzyme, having the specific activity of 606.67 EU mg protein-1, was purified with a yield of 10.75% and 2476-fold, and, in order to control enzyme purity, SDS-PAGE was done. Optimal pH, stable ...

  8. delta1-piperideine-2-carboxylate reductase of Pseudomonas putida.

    OpenAIRE

    Payton, C W; Chang, Y. F.

    1982-01-01

    Pseudomonas putida metabolizes D-lysine to delta 1-piperideine-2-carboxylate and L-pipecolate. The second step of this catabolic pathway is catalyzed by delta 1-piperideine-2-carboxylate reductase. This enzyme was isolated and purified from cells grown on DL-lysine as substrate. The enzyme was very unstable, resulting in low recovery of activity and low purity after a six-step purification procedure. The enzyme had a pH optimum of 8.0 to 8.3. The Km values for delta 1-piperideine-2-carboxylat...

  9. Tioredoxin reductase – a new target for molecular medical investigations

    Directory of Open Access Journals (Sweden)

    Pawe? Zagrodzki

    2002-06-01

    Full Text Available Thioredoxin reductase (TrxR is the first selenoenzyme containing selenocysteine in the active center and FAD as a second prosthetic group. TrxR catalyses the NADPH-dependent reduction of thioredoxin and of many other physiologically important substrates. TrxR exhibits a many-fold increase in the activity in tumor cells and stimulates their proliferation as well the phenotype changes. Some gold compounds and a number of other clinically and experimentally tested drugs have been shown to inhibit TrxR. The involvement of TrxR/Trx/NADPH system in a broad spectrum of cellular processes renders it a potential target for therapeutic approaches.

  10. Advantages and drawbacks of Thiol-ene based resins for 3D-printing

    Science.gov (United States)

    Leonards, Holger; Engelhardt, Sascha; Hoffmann, Andreas; Pongratz, Ludwig; Schriever, Sascha; Bläsius, Jana; Wehner, Martin; Gillner, Arnold

    2015-03-01

    The technology of 3D printing is conquering the world and awakens the interest of many users in the most varying of applications. New formulation approaches for photo-sensitive thiol-ene resins in combination with various printing technologies, like stereolithography (SLA), projection based printing/digital light processing (DLP) or two-photon polymerization (TPP) are presented. Thiol-ene polymerizations are known for its fast and quantitative reaction and to form highly homogeneous polymer networks. As the resins are locally and temporally photo-curable the polymerization type is very promising for 3D-printing. By using suitable wavelengths, photoinitiator-free fabrication is feasible for single- and two photon induced polymerization. In this paper divinyl ethers of polyethylene glycols in combination with star-shaped tetrathiols were used to design a simple test-system for photo-curable thiol-ene resins. In order to control and improve curing depth and lateral resolution in 3D-polymerization processes, either additives in chemical formulation or process parameters can be changed. The achieved curing depth and resolution limits depend on the applied fabrication method. While two-/multiphoton induced lithography offers the possibility of micron- to sub-micron resolution it lacks in built-up speed. Hence single-photon polymerization is a fast alternative with optimization potential in sub-10-micron resolution. Absorber- and initiator free compositions were developed in order to avoid aging, yellowing and toxicity of resulting products. They can be cured with UV-laser radiation below 300 nm. The development at Fraunhofer ILT is focusing on new applications in the field of medical products and implants, technical products with respect to mechanical properties or optical properties of 3D-printed objects. Recent process results with model system (polyethylene glycol divinylether/ Pentaerithrytol tetrakis (3-mercaptopropionat), Raman measurements of polymer conversion and surface modifications using bifunctional crosslinkers are presented with advantages, drawbacks and a general outlook.

  11. Protein Tyrosine Nitration and Thiol Oxidation by Peroxynitrite—Strategies to Prevent These Oxidative Modifications

    Directory of Open Access Journals (Sweden)

    Thomas Münzel

    2013-04-01

    Full Text Available The reaction product of nitric oxide and superoxide, peroxynitrite, is a potent biological oxidant. The most important oxidative protein modifications described for peroxynitrite are cysteine-thiol oxidation and tyrosine nitration. We have previously demonstrated that intrinsic heme-thiolate (P450-dependent enzymatic catalysis increases the nitration of tyrosine 430 in prostacyclin synthase and results in loss of activity which contributes to endothelial dysfunction. We here report the sensitive peroxynitrite-dependent nitration of an over-expressed and partially purified human prostacyclin synthase (3.3 ?M with an EC50 value of 5 ?M. Microsomal thiols in these preparations effectively compete for peroxynitrite and block the nitration of other proteins up to 50 ?M peroxynitrite. Purified, recombinant PGIS showed a half-maximal nitration by 10 ?M 3-morpholino sydnonimine (Sin-1 which increased in the presence of bicarbonate, and was only marginally induced by freely diffusing NO2-radicals generated by a peroxidase/nitrite/hydrogen peroxide system. Based on these observations, we would like to emphasize that prostacyclin synthase is among the most efficiently and sensitively nitrated proteins investigated by us so far. In the second part of the study, we identified two classes of peroxynitrite scavengers, blocking either peroxynitrite anion-mediated thiol oxidations or phenol/tyrosine nitrations by free radical mechanisms. Dithiopurines and dithiopyrimidines were highly effective in inhibiting both reaction types which could make this class of compounds interesting therapeutic tools. In the present work, we highlighted the impact of experimental conditions on the outcome of peroxynitrite-mediated nitrations. The limitations identified in this work need to be considered in the assessment of experimental data involving peroxynitrite.

  12. Determination of cellular thiols and glutathione-related enzyme activities: versatility of high-performance liquid chromatography-spectrofluorimetric detection.

    Science.gov (United States)

    Parmentier, C; Leroy, P; Wellman, M; Nicolas, A

    1998-11-20

    A high-performance liquid chromatography (HPLC) method to determine the most important cellular thiols [reduced glutathione (GSH), cysteine, gamma-glutamylcysteine and cysteinylglycine] is described. Separation relies upon isocratic ion-pairing reversed-phase chromatography and detection is operated by spectrofluorimetry coupled with post-column derivatization reactions using either N-(1-pyrenyl)maleimide (NPM) or ortho-phthalaldehyde (OPA). When OPA is used without co-reagent, only GSH and gamma-glutamylcysteine are detected (heterobifunctional reaction). However, either the OPA reaction in the presence of glycine in the mobile phase (thiol-selective reaction) or NPM allows the detection of all the cited thiols. The HPLC system has been validated as concerning linearity, accuracy and precision. The low detection limits reached (in the pmol range for each thiol injected) allow the screening and the quantification of thiols (as NPM derivatives) in V79cl and V79HGGT cells as well as the measurement of two cytosolic enzymes related to the glutathione synthesis, using the heterobifunctional OPA reaction. PMID:9869362

  13. Spectrofluorimetric determination of total free thiols based on formation of complexes of Ce(III) with disulfide bonds

    International Nuclear Information System (INIS)

    A simple, rapid, and sensitive determination of total free thiol groups in biological samples using cerium (IV) as a fluorescence probe is reported. The protocol is based on the oxidation of thiols by Ce(IV) and the formation the Ce(III) disulfide complex, which gives a fluorescence enhancement of Ce(III) at 352 nm. Using glutathione (GSH) and cysteine as model compounds, incubation with Ce(IV) at 25 oC for 6 min results in fluorescence, whose intensity is proportional to the thiol concentration in the range of 1.00-160 nM. The detection limits for GSH and cysteine are 0.05 and 0.08 nM, respectively. Other common metal ions and amino acids have little interference to the thiol detection. Cu(II) was used as a fluorescence quencher to eliminate potential interference from tryptophan. The method has been successfully applied to assays of free thiol contents in pig liver tissue samples, with a RSD lower than 2.5% and recovery between 100.6% and 102.3%.

  14. Surface Modification of Polydivinylbenzene Microspheres with a Fluorinated Glycopolymer Using Thiol-Halogen Click Chemistry.

    Science.gov (United States)

    Song, Wentao; Granville, Anthony M

    2016-01-01

    Distillation-precipitation polymerization of divinylbenzene was applied to obtain uniform-sized polymeric microspheres. The microspheres were then modified with polypentafluorostyrene chains utilizing surface-initiated atom transfer radical polymerization techniques. The hydrophobic fluoropolymer-coated microsphere was then converted to a hydrophilic biopolymer by performing thiol-halogen click chemistry between polypentafluorostyrene and 1-thio-?-D-glucose sodium salt. The semi-fluorinated glycopolymer showed good binding ability with Concanavalin A as determined by confocal microscopy and turbidity experiments. PMID:26537469

  15. Subcellular Localization of Thiol-Capped CdTe Quantum Dots in Living Cells

    Directory of Open Access Journals (Sweden)

    Chen Ji-Yao

    2009-01-01

    Full Text Available Abstract Internalization and dynamic subcellular distribution of thiol-capped CdTe quantum dots (QDs in living cells were studied by means of laser scanning confocal microscopy. These unfunctionalized QDs were well internalized into human hepatocellular carcinoma and rat basophilic leukemia cells in vitro. Co-localizations of QDs with lysosomes and Golgi complexes were observed, indicating that in addition to the well-known endosome-lysosome endocytosis pathway, the Golgi complex is also a main destination of the endocytosed QDs. The movement of the endocytosed QDs toward the Golgi complex in the perinuclear region of the cell was demonstrated.

  16. Thiol-based H2O2 signalling in microbial systems

    Directory of Open Access Journals (Sweden)

    Susanna Boronat

    2014-01-01

    Full Text Available Cysteine residues, and in particular their thiolate groups, react not only with reactive oxygen species but also with electrophiles and with reactive nitrogen species. Thus, cysteine oxidation has often been linked to the toxic effects of some of these reactive molecules. However, thiol-based switches are common in protein sensors of antioxidant cascades, in both prokaryotic and eukaryotic organisms. We will describe here three redox sensors, the transcription factors OxyR, Yap1 and Pap1, which respond by disulfide bond formation to hydrogen peroxide stress, focusing specially on the differences among the three peroxide-sensing mechanisms.

  17. Subcellular Localization of Thiol-Capped CdTe Quantum Dots in Living Cells

    Science.gov (United States)

    Zhang, Yu; Mi, Lan; Xiong, Rongling; Wang, Pei-Nan; Chen, Ji-Yao; Yang, Wuli; Wang, Changchun; Peng, Qian

    2009-07-01

    Internalization and dynamic subcellular distribution of thiol-capped CdTe quantum dots (QDs) in living cells were studied by means of laser scanning confocal microscopy. These unfunctionalized QDs were well internalized into human hepatocellular carcinoma and rat basophilic leukemia cells in vitro. Co-localizations of QDs with lysosomes and Golgi complexes were observed, indicating that in addition to the well-known endosome-lysosome endocytosis pathway, the Golgi complex is also a main destination of the endocytosed QDs. The movement of the endocytosed QDs toward the Golgi complex in the perinuclear region of the cell was demonstrated.

  18. Characterization of thiol-functionalised silica films deposited on electrode surfaces

    Scientific Electronic Library Online (English)

    Ivana, Cesarino; Éder Tadeu Gomes, Cavalheiro.

    2008-12-01

    Full Text Available Thiol-functionalised silica films were deposited on various electrode surfaces (gold, platinum, glassy carbon) by spin-coating sol-gel mixtures in the presence of a surfactant template. Film formation occurred by evaporation induced self-assembly (EISA) involving the hydrolysis and (co)condensation [...] of silane and organosilane precursors on the electrode surface. The characterization of such material was performed by IR spectroscopy, thermogravimetry (TG), elemental analysis (EA), atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV).

  19. X-ray absorption fine structure spectroscopy studies of thiol-capped copper nanoparticles

    International Nuclear Information System (INIS)

    Monodisperse Copper nanoparticles with controllable sizes of 0.6 and 1.8nm were synthesized via modifying Brust-Schiffrin two-phase method. This route involves a slow reduction of [TOA]2[CuBr4] precursor in toluene, with particles sizes rationally controlled by the S/Cu ratio. Size-dependent inter-atomic distance contraction in the thiol-capped copper nanoparticles was investigated by Extended X-ray Absorption Fine Structure (EXAFS). The analysis revealed a shortened Cu-Cu inter-atomic distance, indicating strong surface interaction, in accord with the larger effect expected for ultrasmall particals (<2nm).

  20. X-ray absorption fine structure spectroscopy studies of thiol-capped copper nanoparticles

    Science.gov (United States)

    Huang, Y. Y.; Yao, T.; Sun, Z. H.; Wei, S. Q.

    2013-04-01

    Monodisperse Copper nanoparticles with controllable sizes of 0.6 and 1.8nm were synthesized via modifying Brust-Schiffrin two-phase method. This route involves a slow reduction of [TOA]2[CuBr4] precursor in toluene, with particles sizes rationally controlled by the S/Cu ratio. Size-dependent inter-atomic distance contraction in the thiol-capped copper nanoparticles was investigated by Extended X-ray Absorption Fine Structure (EXAFS). The analysis revealed a shortened Cu-Cu inter-atomic distance, indicating strong surface interaction, in accord with the larger effect expected for ultrasmall particals (<2nm).

  1. Synthesis of novel thiol-functionalized mesoporous silica nanorods and their sorbent properties on heavy metals

    Science.gov (United States)

    Chen, Xi; Cai, Qiang; Sun, Lin-Hao; Zhang, Wei; Jiang, Xing-Yu

    2012-09-01

    Novel thiol-functionalized mesoporous silica nanorods (MSNRs) were synthesized through a base co-condensation method, in which two organoalkoxysilanes, tetraethoxylsilane (TEOS) and bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT), were used as silica precursors simultaneously. TESPT was firstly used for both morphology control and inner surface functionalization of mesoporous silica hybrid materials. The microstructures as well as porous character of the MSNRs were characterized by means of SEM, XRD, TEM and N2 sorption measurements. Infrared spectrum analysis and heavy metal ions (Ag+ and Cd2+) adsorption measurements were carried out to confirm the functionalized framework of MSNRs.

  2. Monitoring of Saccharomyces cerevisiae cell proliferation on thiol-modified planar gold microelectrodes using impedance spectroscopy

    DEFF Research Database (Denmark)

    Heiskanen, Arto; Spegel, Christer F; Kostesha, Natalie; Ruzgas, Tautgirdas; Emnéus, Jenny

    2008-01-01

    An impedance spectroscopic study of the interaction between thiol-modified Au electrodes and Saccharomyces cerevisiae of strain EBY44 revealed that the cells formed an integral part of the interface, modulating the capacitive properties until a complete monolayer was obtained, whereas the charge transfer resistance (R-ct) to the redox process of [Fe(CN)6](3-14-) showed a linear relationship to the number of cells even beyond the monolayer coverage. R,, showed strong pH dependence upon increasing...

  3. Characterization of thiol-functionalised silica films deposited on electrode surfaces

    Directory of Open Access Journals (Sweden)

    Ivana Cesarino

    2008-12-01

    Full Text Available Thiol-functionalised silica films were deposited on various electrode surfaces (gold, platinum, glassy carbon by spin-coating sol-gel mixtures in the presence of a surfactant template. Film formation occurred by evaporation induced self-assembly (EISA involving the hydrolysis and (cocondensation of silane and organosilane precursors on the electrode surface. The characterization of such material was performed by IR spectroscopy, thermogravimetry (TG, elemental analysis (EA, atomic force microscopy (AFM, scanning electron microscopy (SEM and cyclic voltammetry (CV.

  4. Biochemical Characterization of a Thiol-Activated, Oxidation Stable Keratinase from Bacillus pumilus KS12

    OpenAIRE

    Rinky Rajput; Richa Sharma; Rani Gupta

    2010-01-01

    An extracellular keratinase from Bacillus pumilus KS12 was purified by DEAE ion exchange chromatography. It was a 45?kDa monomer as determined by SDS PAGE analysis. It was found to be an alkaline, serine protease with pH and temperature optima of 10 and 60C?, respectively. It was thiol activated with two- and eight-fold enhancement in presence of 10 mM DTT and ?-mercaptoethanol, respectively. In addition, its activity was stimulated in the presence of various surfactants,...

  5. Gold nanoparticles decorated with oligo(ethylene glycol) thiols: protein resistance and colloidal stability.

    OpenAIRE

    Zhang, F.; Skoda, MW; Jacobs, RM; Zorn, S; Martin, RA; Martin, CM; Clark, GF; Goerigk, G.; Schreiber, F.

    2007-01-01

    The interactions between proteins and gold colloids functionalized with protein-resistant oligo(ethylene glycol) (OEG) thiol, HS(CH2)11(OCH2CH2)6OMe (EG6OMe), in aqueous solution have been studied by small-angle X-ray scattering (SAXS) and UV-vis spectroscopy. The mean size, 2R, and the size distribution of the decorated gold colloids have been characterized by SAXS. The monolayer-protected gold colloids have no correlations due to the low volume fraction in solution and are stable in a wide ...

  6. Liquid crystalline polybutadiene diols with chiral thiol side-chain units.

    Czech Academy of Sciences Publication Activity Database

    Kašpar, Miroslav; Bubnov, Alexej M.; Sedláková, Zde?ka; Stojanovi?, M.; Havlí?ek, J.; Obadovi?, D.; Ilavský, Michal

    2008-01-01

    Ro?. 44, ?. 1 (2008), s. 233-243. ISSN 0014-3057 R&D Projects: GA ?R GP202/03/P011; GA ?R GA202/05/0431; GA MŠk OC 175; GA AV ?R IAA100100710; GA AV ?R IAA4112401 Grant ostatní: MSEP(CS) 141020; ESF-COST(XE) D35 WG13-05 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40500505 Keywords : chiral thiols * liquid crystal * polybutadiene * diols * side-chain polymer * polarizing optical microscopy * X-ray * dielectric spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.143, year: 2008

  7. Spectrophotometric determination of tungstate using an iron salt, a thiol and oxygen

    International Nuclear Information System (INIS)

    A simple, fast and inexpensive method for the determination of tungstate have been developed. The determination uses only reagents that are commonly found in biochemistry laboratories, i.e., iron(II) ammonium sulphate or iron(III) chloride, a thiol such as cysteine, 2-aminoethanethiol or 2-thioethanol, oxygen gas and a buffer (phthalate, acetate or glutarate) at pH 5.8. A compound of unknown structure is formed, which has an absorbance maximum at 475 nm (for cysteine) with epsilon = 420 l mol-1 cm-1, allowing the determination of 0.5 - 10 μmol of tungstate in a volume of 1 ml. (author)

  8. Acute changes in intracellular ions or pH and regulation of aldose reductase activity.

    Science.gov (United States)

    Sands, J M; Schrader, D C

    1991-08-01

    Sorbitol production in the renal medulla increases in dehydrated rats, indicating that aldose reductase activity varies with the state of hydration. This response could be due to an increased synthesis of the enzyme (Moriyama T et al. J Biol Chem 1989:264:16810-16814) and/or a change in aldose reductase activity caused by acute changes in intracellular ionic composition, ionic strength, osmolality, or pH. Aldose reductase activity in tubules dissected from kidneys of control rats and rats undergoing water diuresis was measured, and the tubules were permeabilized so that changes in intracellular composition that would occur during dehydration could be induced experimentally. Aldose reductase activity did not change consistently as sodium, potassium, chloride, or osmolality were varied. Aldose reductase activity did increase acutely when sulfate was raised or when pH was lowered to pH 6.2 to 6.8, corresponding to the pH optimum of the enzyme. The small magnitude of change in enzyme activity suggests that the major influence of dehydration on aldose reductase activity is to increase enzyme synthesis. It was concluded that aldose reductase activity is not acutely regulated by changes in sodium, potassium, chloride, or osmolality. The stability of aldose reductase activity despite changes in ionic composition or osmolality supports the hypothesis that acute regulation of intracellular sorbitol content occurs by variation in cell sorbitol permeability and not by variation in cell sorbitol production. PMID:1954333

  9. Evaluation of 5?-reductase inhibitory activity of certain herbs useful as antiandrogens.

    Science.gov (United States)

    Nahata, A; Dixit, V K

    2014-08-01

    This study demonstrates 5?-reductase inhibitory activity of certain herbs useful in the management of androgenic disorders. Ganoderma lucidum (Curtis) P. Karst (GL), Urtica dioica Linn. (UD), Caesalpinia bonducella Fleming. (CB), Tribulus terrestris Linn. (TT), Pedalium murex Linn. (PM), Sphaeranthus indicus Linn. (SI), Cuscuta reflexa Roxb. (CR), Citrullus colocynthis Schrad. (CC), Benincasa hispida Cogn. (BH), Phyllanthus niruri Linn. (PN) and Echinops echinatus Linn. (EE) were included in the study. Petroleum ether, ethanol and aqueous extracts of these herbs were tested for their 5?-reductase inhibitory activity against the standard 5?-reductase inhibitor, finasteride. A biochemical method to determine the activity of 5?-reductase was used to evaluate the inhibition of different extracts to the enzyme. The optical density (OD) value of each sample was measured continuously with ultraviolet spectrophotometer for the reason that the substrate NADPH has a specific absorbance at 340 nm. As the enzyme 5?-reductase uses NADPH as a substrate, so in the presence of 5?-reductase inhibitor, the NADPH concentration will increase with the function of time. This method thus implicates the activity of 5?-reductase. The method proved to be extremely useful to screen the herbs for their 5?-reductase inhibitory potential. GL, UD, BH, SI and CR came out to be promising candidates for further exploring their antiandrogenic properties. PMID:23710567

  10. Co-Expression of Monodehydroascorbate Reductase and Dehydroascorbate Reductase from Brassica rapa Effectively Confers Tolerance to Freezing-Induced Oxidative Stress

    OpenAIRE

    Shin, Sun-Young; Kim, Myung-hee; Kim, Yul-Ho; Park, Hyang-Mi; Yoon, Ho-Sung

    2013-01-01

    Plants are exposed to various environmental stresses and have therefore developed antioxidant enzymes and molecules to protect their cellular components against toxicity derived from reactive oxygen species (ROS). Ascorbate is a very important antioxidant molecule in plants, and monodehydroascorbate reductase (MDHAR; EC 1.6.5.4) and dehydroascorbate reductase (DHAR; EC 1.8.5.1) are essential to regeneration of ascorbate for maintenance of ROS scavenging ability. The MDHAR and DHAR genes from ...

  11. Transgenic Tobacco Overexpressing Tea cDNA Encoding Dihydroflavonol 4-Reductase and Anthocyanidin Reductase Induces Early Flowering and Provides Biotic Stress Tolerance

    OpenAIRE

    Kumar, Vinay; Nadda, Gireesh; Kumar, Sanjay; Yadav, Sudesh Kumar

    2013-01-01

    Flavan-3-ols contribute significantly to flavonoid content of tea (Camellia sinensis L.). Dihydroflavonol 4-reductase (DFR) and anthocyanidin reductase (ANR) are known to be key regulatory enzymes of flavan-3-ols biosynthesis. In this study, we have generated the transgenic tobacco overexpressing individually tea cDNA CsDFR and CsANR encoding for DFR and ANR to evaluate their influence on developmental and protective abilities of plant against biotic stress. The transgenic lines of CsDFR and ...

  12. The effect of ionic and non-ionic surfactants on the growth, nitrate reductase and nitrite reductase activities of Spirodela polyrrhiza (L. Schleiden

    Directory of Open Access Journals (Sweden)

    Józef Buczek

    2014-02-01

    Full Text Available Inclusion into the medium of 5 mg•dm-3 of non-ionic (ENF or ionic (DBST surfactant caused 50-60% inhibition of nitrite reductase MR activity in S. polyrrhiza. At the same time, increased accumulation of NO2- in the plant tissues and lowering of the total and soluble protein contents were found. DBST also lowered the nitrate reductase (NR activity and the dry mass of the plants.

  13. Characterization of the norB Gene, Encoding Nitric Oxide Reductase, in the Nondenitrifying Cyanobacterium Synechocystis sp. Strain PCC6803

    OpenAIRE

    Büsch, Andrea; Friedrich, Bärbel; Cramm, Rainer

    2002-01-01

    A norB gene encoding a putative nitric oxide reductase is present in the genome of the nondenitrifying cyanobacterium Synechocystis sp. strain PCC6803. The gene product belongs to the quinol-oxidizing single-subunit class of nitric oxide reductases, discovered recently in the denitrifier Ralstonia eutropha. Heterologous complementation of a nitric oxide reductase-negative mutant of R. eutropha with norB from Synechocystis restored nitric oxide reductase activity. With reduced menadione as the...

  14. Crystallization and preliminary characterization of dihydropteridine reductase from Dictyostelium discoideum

    International Nuclear Information System (INIS)

    The dihydropteridine reductase from D. discoideum has been crystallized. Diffraction data were collected from a rectangular-shaped crystal to 2.16 Å resolution. Dihydropteridine reductase from Dictyostelium discoideum (dicDHPR) can produce d-threo-BH4 [6R-(1?R,2?R)-5,6,7,8-tetrahydrobiopterin], a stereoisomer of l-erythro-BH4, in the last step of tetrahydrobiopterin (BH4) recycling. In this reaction, DHPR uses NADH as a cofactor to reduce quinonoid dihydrobiopterin back to BH4. To date, the enzyme has been purified to homogeneity from many sources. In this report, the dicDHPR–NAD complex has been crystallized using the hanging-drop vapour-diffusion method with PEG 3350 as a precipitant. Rectangular-shaped crystals were obtained. Crystals grew to maximum dimensions of 0.4 × 0.6 × 0.1 mm. The crystal belonged to space group P21, with unit-cell parameters a = 49.81, b = 129.90, c = 78.76 Å, ? = 100.00°, and contained four molecules in the asymmetric unit, forming two closely interacting dicDHPR–NAD dimers. Diffraction data were collected to 2.16 Å resolution using synchrotron radiation. The crystal structure has been determined using the molecular-replacement method

  15. Relationship of non-protein thiol pools and accumulated Cd or Hg in the marine macrophyte Posidonia oceanica (L.) Delile

    Energy Technology Data Exchange (ETDEWEB)

    Maserti, B.E. [National Research Council (CNR), Institute of Biophysics, Area della Ricerca CNR, Via Moruzzi 1, 56125 Pisa (Italy)]. E-mail: bianca.elena.maserti@pi.ibf.cnr.it; Ferrillo, V. [National Research Council (CNR), Institute of Biophysics, Area della Ricerca CNR, Via Moruzzi 1, 56125 Pisa (Italy); University of Pisa, Department of Agricultural Plant, Section of Genetics, Via Matteotti 1, 56100 Pisa (Italy); Avdis, O. [National Centre for Marine Research (N.C.M.R.), 16604 Hellenion (Greece); Nesti, U. [National Research Council (CNR), Institute of Biophysics, Area della Ricerca CNR, Via Moruzzi 1, 56125 Pisa (Italy); Central Institute for Marine Research (I.C.R.A.M.), Via di Casalotti, 300-00166 Rome (Italy); Di Garbo, A. [National Research Council (CNR), Institute of Biophysics, Area della Ricerca CNR, Via Moruzzi 1, 56125 Pisa (Italy); Catsiki, A. [National Centre for Marine Research (N.C.M.R.), 16604 Hellenion (Greece); Maestrini, P.L. [University of Pisa, Department of Agricultural Plant, Section of Genetics, Via Matteotti 1, 56100 Pisa (Italy)

    2005-11-10

    The accumulation of cadmium or mercury and the effect of these elements on the levels of non-protein thiols in the blades of the marine macrophyte Posidonia oceanica were investigated. A significant accumulation of cadmium or mercury, dependent on metal concentration supplied, was observed in metal-treated blades. In the blades treated either with cadmium or mercury, a significant increase in the levels of non-protein thiols (other than glutathione) and a marked depletion of the reduced glutathione content as a function of the metal, exposure time and metal concentration supplied were found. This investigation provides first experimental report on the relationship between non-protein thiol pools and accumulated cadmium or mercury in P. oceanica.

  16. Antioxidative Mechanisms of Sulfite and Protein-Derived Thiols during Early Stages of Metal Induced Oxidative Reactions in Beer.

    Science.gov (United States)

    Lund, Marianne N; Krämer, Anna C; Andersen, Mogens L

    2015-09-23

    The radical-mediated reactions occurring during the early stages of beer storage were studied by following the rate of oxygen consumption, radical formation as detected by electron spin resonance spectroscopy, and concentrations of the antioxidant compounds sulfite and thiols. Addition of either Fe(III) or Fe(II) had similar effects, indicating that a fast redox equilibrium is obtained between the two species in beer. Addition of iron in combination with hydrogen peroxide gave the most pronounced levels of oxidation due to a direct initiation of ethanol oxidation through generation of hydroxyl radicals by the Fenton reaction. The concentration of sulfite decreased more than the thiol concentration, suggesting that thiols play a secondary role as antioxidants by mainly quenching 1-hydroxyethyl radicals that are intermediates in the oxidation of ethanol. Increasing the temperature had a minor effect on the rate of oxygen consumption. PMID:26325117

  17. Preparing mono-dispersed liquid core PDMS microcapsules from thiol–ene–epoxy-tailored flow-focusing microfluidic devices

    DEFF Research Database (Denmark)

    Mazurek, Piotr Stanislaw; Daugaard, Anders Egede

    2015-01-01

    An applied dual-cure system based on thiol–ene and thiol–epoxy “click chemistry” reactions was proved to be an extremely effective and easy to use tool for preparing microfluidic chips, thereby allowing for precise control over material properties and providing the possibility of covalently bonding chip wafers. Different thiol–ene–epoxy-based polymer compositions were tested with the help of DSC and ATR FTIR, in order to investigate their physical and chemical properties. Water contact angles were determined, thus verifying the high efficiency and selectivity of the chemical surface modification of compositions in relation to high hydrophilicity and hydrophobicity. An obtained microfluidic device was subsequently used in order to produce PDMS microcapsules of very narrow size distribution and which contained various common liquids, such as water and ethanol, as well as an ionic liquid 2-hydroxyethylammonium formate.

  18. Preparing mono-dispersed liquid core PDMS microcapsules from thiol-ene-epoxy-tailored flow-focusing microfluidic devices

    DEFF Research Database (Denmark)

    Mazurek, Piotr Stanislaw; Daugaard, Anders Egede

    2015-01-01

    An applied dual-cure system based on thiol-ene and thiol-epoxy "click chemistry" reactions was proved to be an extremely effective and easy to use tool for preparing microfluidic chips, thereby allowing for precise control over material properties and providing the possibility of covalently bonding chip wafers. Different thiol-ene-epoxy-based polymer compositions were tested with the help of DSC and ATR FTIR, in order to investigate their physical and chemical properties. Water contact angles were determined, thus verifying the high efficiency and selectivity of the chemical surface modification of compositions in relation to high hydrophilicity and hydrophobicity. An obtained microfluidic device was subsequently used in order to produce PDMS microcapsules of very narrow size distribution and which contained various common liquids, such as water and ethanol, as well as an ionic liquid 2-hydroxyethylammonium formate.

  19. Trypanothione Reductase: A Viable Chemotherapeutic Target for Antitrypanosomal and Antileishmanial Drug Design

    Directory of Open Access Journals (Sweden)

    M. Omar F. Khan

    2007-01-01

    Full Text Available Trypanosomiasis and leishmaniasis are two debilitating disease groups caused by parasites of Trypanosoma and Leishmania spp. and affecting millions of people worldwide. A brief outline of the potential targets for rational drug design against these diseases are presented, with an emphasis placed on the enzyme trypanothione reductase. Trypanothione reductase was identified as unique to parasites and proposed to be an effective target against trypanosomiasis and leishmaniasis. The biochemical basis of selecting this enzyme as a target, with reference to the simile and contrast to human analogous enzyme glutathione reductase, and the structural aspects of its active site are presented. The process of designing selective inhibitors for the enzyme trypanothione reductase has been discussed. An overview of the different chemical classes of inhibitors of trypanothione reductase with their inhibitory activities against the parasites and their prospects as future chemotherapeutic agents are briefl y revealed.

  20. Irreversible inactivation of trypanothione reductase by unsaturated Mannich bases: a divinyl ketone as key intermediate.

    Science.gov (United States)

    Lee, Brittany; Bauer, Holger; Melchers, Johannes; Ruppert, Thomas; Rattray, Lauren; Yardley, Vanessa; Davioud-Charvet, Elisabeth; Krauth-Siegel, R Luise

    2005-11-17

    Trypanothione reductase is a flavoenzyme unique to trypanosomatid parasites. Here we show that unsaturated Mannich bases irreversibly inactivate trypanothione reductase from Trypanosoma cruzi, the causative agent of Chagas' disease. The inhibitory potency of the compounds strongly increased upon storage of the DMSO stock solutions. HPLC, NMR, and mass spectrometry data of potential intermediates revealed a divinyl ketone as the active compound inactivating the enzyme. ESI- and MALDI-TOF mass spectrometry of trypanothione reductase modified by the Mannich base or the divinyl ketone showed specific alkylation of the active site Cys52 by a 5-(2'chlorophenyl)-3-oxo-4-pentenyl substituent. The reaction mechanism and the site of alkylation differ from those in Plasmodium falciparum thioredoxin reductase where the C-terminal redox active dithiol is modified. After deamination, unsaturated Mannich bases are highly reactive in polycondensation with trypanothione. Interaction of these compounds with both trypanothione and trypanothione reductase could account for their potent trypanocidal effect against Trypanosoma brucei. PMID:16279799

  1. Product-mediated regulation reveals the polymorphic nature of the yeast assimilatory nitrate reductase.

    Science.gov (United States)

    Choudary, P V

    1993-01-01

    Nitrite functioned as an effective inducer of nitrate reductase, the enzyme responsible for the reduction of nitrate in the nitrate assimilation pathway in Candida utilis. Nitrite-induced synthesis of nitrate reductase in C. utilis was repressed by various metabolites of nitrate, including ammonia. Readily-assimilable sources of nitrogen such as ammonia and glutamate exerted a stronger repression on nitrate reductase induction than did less-readily assimilable hydrazine and hydroxylamine. Nitrite-mediated induction of nitrate reductase appeared more sensitive to repression by nitrate metabolites than was nitrate-mediated induction. Based on the inducer-specific differences in the sensitivity of the enzyme to repression by various intermediary metabolites and on other properties, it is proposed that the C. utilis nitrate reductase is either polymorphic or utilizes alternative receptor(s) for binding various gratuitous inducers including nitrite in initiating the induction pathway. PMID:8336554

  2. The effect of NaCl intake on 9-ketoprostaglandin reductase activity in the rabbit kidney.

    Science.gov (United States)

    Watkins, J D; Jarabak, J

    1985-08-01

    Renal 9-ketoprostaglandin reductase activity from rabbits fed 0.3 g or 2.5 g NaCl per 100 g chow was measured in both centrifuged homogenates and in purified enzyme fractions. There was no salt related increase in 9-ketoprostaglandin reductase activity. PGA1-glutathione, 9, 10-phenanthrenequinone, and 4-nitrobenzaldehyde were better substrates for the purified 9-ketoprostaglandin reductases than was PGE2. Several carbonyl reductases were isolated which used PGA1-glutathione, 9, 10-phenanthrenequinone, and 4-nitrobenzaldehyde, but not PGE2, as substrates. Although PGA1-glutathione was a more faithful indicator of PGE2-related 9-ketoprostaglandin reductase activity than either 9, 10-phenanthrenequione or 4-nitrobenzaldehyde, it did not always provide an accurate estimate of that activity. PMID:3901124

  3. Immunological identification and distribution of dissimilatory heme cd1 and nonheme copper nitrite reductases in denitrifying bacteria.

    OpenAIRE

    Coyne, M S; Arunakumari, A; Averill, B A; Tiedje, J.M.

    1989-01-01

    Polyclonal antibodies were used to identify heme or copper nitrite reductases in the following groups: 23 taxonomically diverse denitrifiers from culture collections, 100 numerically dominant denitrifiers from geographically diverse environments, and 51 denitrifiers from a culture collection not selected for denitrification. Antisera were raised against heme nitrite reductases from Pseudomonas aeruginosa and Pseudomonas stutzeri and against copper nitrite reductase from Achromobacter cyclocla...

  4. Mixing thiols on the surface of silver nanoparticles: preserving antibacterial properties while introducing SERS activity

    International Nuclear Information System (INIS)

    Controlling the surface composition of self-assembled monolayers is one of the major experimental challenges in nanotechnology. Despite the significant interest of the scientific community and the considerable number of publications related to this topic, the potential in this field is still far from being fully exploited.We present in this study a versatile method to coat silver nanoparticles (AgNPs) having average diameter of 7 nm with mixed monolayers of two thiols, achieving a precise control of surface composition. Different combinations of thiols have been investigated, and the nanomaterials obtained have been characterized by complementary experimental techniques, addressing the composition of the mixed monolayer. The surface-enhanced Raman spectroscopy (SERS) effect on a Raman reporter (7-mercapto-4-methylcoumarine) introduced into the mixed monolayers has also been investigated. The antibacterial activity of the coated AgNPs was investigated, showing that the colloids were active against Escherichia coli and Staphilococcus aureus irrespective of the nature of the mixed monolayer. These materials are good candidates as SERS-tags for biological applications

  5. Cellular thiols and reactive oxygen species in drug-induced apoptosis.

    Science.gov (United States)

    Davis, W; Ronai, Z; Tew, K D

    2001-01-01

    In higher eukaryotes, reactive oxygen species (ROS) are generated during respiration in mitochondria in the course of reduction of molecular oxygen as well as by distinct enzyme systems. ROS have been implicated in the regulation of diverse cellular functions including defense against pathogens, intracellular signaling, transcriptional activation, proliferation, and apoptosis. The reduction-oxidation (redox) state of the cell is primarily a consequence of the precise balance between the levels of ROS and endogenous thiol buffers present in the cell, such as glutathione and thioredoxin, which protect cells from oxidative damage. Dramatic elevation of ROS, exceeding compensatory changes in the level of the endogenous thiol buffers, may result in the sustained activation of signaling pathways and expression of genes that induce apoptosis in affected cells. Many cytotoxic drugs function selectively to kill cancer cells by the abrogation of proliferative signals, leading to cell death, and numerous reports have demonstrated that ROS are generated following treatment with these drugs. In this review, we will summarize recent contributions to our understanding of the importance of cytotoxic drug-induced modulation of cellular redox status for signaling and transcription leading to activation of apoptotic effector mechanisms. PMID:11123355

  6. Surface modification of silicate glass using 3-(mercaptopropyl)trimethoxysilane for thiol-ene polymerization.

    Science.gov (United States)

    Chen, Jiun-Jeng; Struk, Kimberly N; Brennan, Anthony B

    2011-11-15

    A thiol-ene polymerization was accomplished on silicate glass slides to graft a series of homopolymers and copolymers using 3-(mercaptopropyl)trimethoxysilane (MTS) as both a silane coupling agent and initiator. MTS was initially covalently bonded to an acid cleaned glass surface via a classical sol-gel reaction. Poly(acrylic acid) (PAA), poly(acrylamide) (PAAm), poly(methyl acrylate) (PMA), poly(acrylamido-2-methyl-propanesulfonic acid) (PAMPS), and the copolymer poly(AA-co-AAm-co-MA-co-AMPS) were grafted from the thiol group of MTS. The surface chemistry of the MTS modified slides and polymer grafts was characterized with attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Surface texture was evaluated with tapping mode atomic force microscopy (TM-AFM). The Owens-Wendt-Kaelble (OWK) and Lifshitz-van der Waals acid-base (LW-AB) methods were used to evaluate surface energies by sessile drop contact angle method. The synthetic approach demonstrated a facile, rapid method for grafting to glass surfaces. PMID:21870797

  7. Adsorption characteristics of self-assembled thiol and dithiol layer on gold

    International Nuclear Information System (INIS)

    Monolayers of functional proteins are important in many fields related to pure and applied biochemistry and biophysics. The formation of extended uniform protein monolayers by single- or multiple-step self-chemisorption depends on the quality of the functionalized gold surface. The optical and the electrical properties of the 1-nonanethiol and 1,9-nonanedithiol deposited on gold with the self-assembled technique were investigated. We use cyclic voltammetry and impedance spectroscopy to characterize the insulating properties of the two layers. The analysis of the impedance spectra in terms of equivalent circuit of the gold/electrolyte and gold/SAM/electrolyte interface allows defining the thickness of the two thiols and the percentage of coverage area. Atomic force microscopy, contact angle measurement and Fourier transform infra-red spectroscopy have been used for homogeneity, hydrophobic properties and molecular structure of the formed thiols layer, respectively. The measured thickness with impedance spectroscopy fit well the results found with atomic force microscopy

  8. Thermal stabilization and plasticization of poly(vinyl chloride) by ester thiols: Update and current status

    International Nuclear Information System (INIS)

    Poly(vinyl chloride) (PVC) is one of the most important medical plastics. Recently, however, the safety of flexible PVC containing the common plasticizer, di(2-ethylhexyl) phthalate, has been called into question. Widely used heat stabilizers for PVC that incorporate toxic heavy metals also have fallen into disfavor. In order to address these problems, we have synthesized and tested, as potential replacements, several organic thiols that contain one or more carboxylate ester functions and thus are highly compatible with the polymer. When introduced into PVC at high loading levels (e.g., 30-35 parts by weight), the ester thiols are extremely effective as heat stabilizers and also useful as primary plasticizers. When used at a low loading level (e.g., 3 parts by weight), they still are excellent heat stabilizers for both plasticized and rigid PVC. Importantly, their high potency is achieved in the absence of any costabilizers that incorporate heavy metals. Their syntheses are simple and straightforward, and their odors are not offensive, because their volatilities are low. Described here are some typical results obtained with this new additive technology, which was licensed for commercialization in 2005

  9. Transcriptional activation by heat and cold of a thiol protease gene in tomato. [Lycopersicon esculentum

    Energy Technology Data Exchange (ETDEWEB)

    Schaffer, M.A.; Fischer, R.L. (Univ. of California, Berkeley (USA))

    1990-08-01

    We previously determined that low temperature induces the accumulation in tomato (Lycopersicon esculentum) fruit of a cloned mRNA, designated C14, encoding a polypeptide related to thiol proteases. We now demonstrate that C14 mRNA accumulation is a response common to both high (40{degree}C) and low (4{degree}C) temperature stresses. Exposure of tomato fruit to 40{degree}C results in the accumulation of C14 mRNA, by 8 hours. This response is more rapid than that to 4{degree}C, but slower than the induction of many heat shock messages by 40{degree}C, and therefore unique. We have also studied the mechanism by which heat and cold exposure activate C14 gene expression. Both high and low temperature regulate protease gene expression through transcriptional induction of a single C14 gene. A hypothesis for the function of C14 thiol protease gene expression in response to heat and cold is discussed.

  10. Adsorption Behavior of Thiols on Metal surfaces; A Density Functional Theory Study

    Science.gov (United States)

    Yourdshahyan, Yashar; Rappe, Andrew

    2003-03-01

    The interaction of thiol molecules with the Au(111) surface was investigated with state-of-the-art first-principles methods. We report theoretical evidence for the existence of a physisorption precursor to chemisorption, in agreement with experiment. The origins of inconsistency in recent studies regarding the adsorption site, geometry, and energetics of CH_3S on the Au(111) surface were also investigated. We show that the chemisorption site is between the hollow and bridge sites, with a large molecular tilting angle relative to the surface normal. The molecular structure of the overlayer is coverage dependent, with the molecular tilting angle increasing with decreasing coverage. Increasing chain length up to three carbon atoms affects both the chemisorption energetics and the tilt angle. The inconsistency of tilting angles, reported for the fcc site is found to be a consequence of multiple local minima. The ordered structure of thiol molecules at different coverages was also investigated, confirming the recent experimental findings that the c(4×2) structure model is preferred over (3×3)R30^rc.

  11. Thiol peroxidase-like activity of some intramolecularly coordinated diorganyl diselenides

    Indian Academy of Sciences (India)

    Sangit Kumar; Harkesh B Singh

    2005-11-01

    Several new diaryl diselenides having intramolecular coordinating groups have been synthesized by ortho-lithiation/Na2Se2 routes in good yield. Bis[2-(N-phenylferrocenecarboxamide)] diselenide (10), bis[2-(N-tert-butylferrocenecarboxamide)] diselenide (11), ()()-bis[2(--phenethylferrocenecarboxamide)] diselenide (12) were synthesized by the ortho-lithiation route. Bis[2-(N,N-dimethylaminomethylnaphthyl)] diselenide (13) was synthesized by lithium/bromide exchange reaction whereas bis(2,4-dinitrophenyl) diselenide (14) was prepared by the reaction of disodium diselenide with 2,4- dinitro-1-chlorobenzene. Thiol peroxidase-like activities of the diorganodiselenides have been evaluated by using H2O2 as substrate and PhSH as cosubstrate. Diselenides (13) and (14) with dimethylaminomethyl- or nitro-donor groups in close proximity to selenium, show much better thiol peroxidase-like activities compared to diselenides 10-12 with amide donor groups. Cyclic voltammetry study of diselenides 10-12 derived from redox-active ferrocenamide has been carried out.

  12. Detection of thiol-based redox switch processes in parasites - facts and future.

    Science.gov (United States)

    Rahbari, Mahsa; Diederich, Kathrin; Becker, Katja; Krauth-Siegel, R Luise; Jortzik, Esther

    2015-05-01

    Malaria and African trypanosomiasis are tropical diseases caused by the protozoa Plasmodium and Trypanosoma, respectively. The parasites undergo complex life cycles in the mammalian host and insect vector, during which they are exposed to oxidative and nitrosative challenges induced by the host immune system and endogenous processes. Attacking the parasite's redox metabolism is a target mechanism of several known antiparasitic drugs and a promising approach to novel drug development. Apart from this aspect, oxidation of cysteine residues plays a key role in protein-protein interaction, metabolic responses to redox events, and signaling. Understanding the role and dynamics of reactive oxygen species and thiol switches in regulating cellular redox homeostasis is crucial for both basic and applied biomedical approaches. Numerous techniques have therefore been established to detect redox changes in parasites including biochemical methods, fluorescent dyes, and genetically encoded probes. In this review, we aim to give an insight into the characteristics of redox networks in the pathogens Plasmodium and Trypanosoma, including a comprehensive overview of the consequences of specific deletions of redox-associated genes. Furthermore, we summarize mechanisms and detection methods of thiol switches in both parasites and discuss their specificity and sensitivity. PMID:25741735

  13. An XPS study of heterocyclic thiol self-assembly on Au(111)

    Science.gov (United States)

    Whelan, Caroline M.; Smyth, Malcolm R.; Barnes, Colin J.; Brown, Norman M. D.; Anderson, Colin A.

    1998-09-01

    The adsorption of the heterocyclic thiol 2-mercaptobenzimidazole (2MBI) self-assembled on Au(111) from the liquid phase has been studied using high resolution X-ray photoelectron spectroscopy (XPS). On the basis of chemical shifts of the nitrogen (1s) and sulphur (2p) electron binding energies for liquid assembled layers, it is concluded that the molecule bonds to Au in the thiol form. A secondary co-ordination with the surface via the unprotonated nitrogen heteroatom is also possible. Angular dependence of core level intensities and a packing density/layer thickness estimation is consistent with a single monolayer of 2MBI adopting a `flat-lying' orientation, although slight inclination of the plane of the molecule cannot be ruled out. Liquid phase self-assembly resulted in films which also contained oxygen and excess carbon. Direct in situ sublimation of 2MBI onto Au(111) yielded oxygen-free layers, however, partial decomposition of the molecule occurs resulting in the formation of atomic sulphur. In the case of ex situ sublimed films, atomic and higher oxidation state sulphur are observed.

  14. Modulating the physicochemical and structural properties of gold-functionalized protein nanotubes through thiol surface modification.

    Science.gov (United States)

    Carreño-Fuentes, Liliana; Plascencia-Villa, Germán; Palomares, Laura A; Moya, Sergio E; Ramírez, Octavio T

    2014-12-16

    Biomolecules are advantageous scaffolds for the synthesis and ordering of metallic nanoparticles. Rotavirus VP6 nanotubes possess intrinsic affinity to metal ions, a property that has been exploited to synthesize gold nanoparticles over them. The resulting nanobiomaterials have unique properties useful for novel applications. However, the formed nanobiomaterials lack of colloidal stability and flocculate, limiting their functionality. Here we demonstrate that it is possible to synthesize thiol-protected gold nanoparticles over VP6 nanotubes, which resulted in soluble nanobiomaterials. With this strategy, it was possible to modulate the size, colloidal stability, and surface plasmon resonance of the synthesized nanoparticles by controlling the content of the thiolated ligands. Two types of water-soluble ligands were tested, a small linear ligand, sodium 3-mercapto-1-propanesulfonate (MPS), and a bulky ligand, 5-mercaptopentyl ?-D-glucopyranoside (GlcC5SH). The synthesized nanobiomaterials had a higher stability in suspension, as determined by Z-potential measurements. To the extent of our knowledge, this is the first time that a rational strategy is developed to modulate the particular properties of metal nanoparticles in situ synthesized over a protein bioscaffold through thiol coating, achieving a high spatial and structural organization of nanoparticles in a single integrative hybrid structure. PMID:25409000

  15. Developments in Dynamic Covalent Chemistries from the Reaction of Thiols with Hexahydrotriazines.

    Science.gov (United States)

    Wojtecki, Rudy J; Jones, Gavin O; Yuen, Alexander Y; Chin, Willy; Boday, Dylan J; Nelson, Alshakim; García, Jeannette M; Yang, Yi Yan; Hedrick, James L

    2015-11-18

    Dynamic covalent chemistries have garnered significant attention for their potential to revolutionize technologies in the material fields (engineering, biomedical, and sensors) and synthetic design strategies as they provide access to stimuli responsiveness and adaptive behaviors. However, only a limited number of molecular motifs have been known to display this dynamic behavior under mild conditions. Here, we identified a dynamic covalent motif-thioaminals-that is produced from the reaction of hexahydrotriazines (HTs) with thiols. Furthermore, we report on the synthesis of a new family of step-growth polymers based on this motif. The condensation efficiently proceeds to quantitative yields within a short time frame and offers versatility in functional group tolerance; thus, it can be exploited to synthesize both small molecule thioaminals as well as high molecular weight polymers from the step-growth polymerization of HTs with dithiols. Careful evaluation of substituted HTs and organic thiols supported by DFT calculations led to a chemically diverse library of polymers based on this motif. Finally, dynamic substitution reactions were employed toward the facile preparation of functional oligomers and macromolecules. This dynamic covalent motif is particularly attractive for a range of applications that include material design and drug delivery due to the economic feasibility of synthesis. PMID:26505551

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

    Energy Technology Data Exchange (ETDEWEB)

    Çubuk, Soner, E-mail: sonercubuk@marmara.edu.tr; Kahraman, Memet Vezir; Yetimo?lu, Ece Kök; Kenan, Sibel

    2014-02-17

    Graphical abstract: -- Highlights: •Photopolymerized fluorescence sensor for Au(III) analysis has been developed. •Preparation of polymeric sensor is simple and quick. •Fluorescence sensor used for analysis of Au(III) in real samples. -- Abstract: 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.

  17. Mitochondrial thiol oxidase Erv1: both shuttle cysteine residues are required for its function with distinct roles

    OpenAIRE

    Ang, Swee Kim; Zhang, Mengqi; Lodi, Tiziana; Lu, Hui

    2014-01-01

    Erv1 (essential for respiration and viability 1), is an essential component of the MIA (mitochondrial import and assembly) pathway, playing an important role in the oxidative folding of mitochondrial intermembrane space proteins. In the MIA pathway, Mia40, a thiol oxidoreductase with a CPC motif at its active site, oxidizes newly imported substrate proteins. Erv1 a FAD-dependent thiol oxidase, in turn reoxidizes Mia40 via its N-terminal Cys30–Cys33 shuttle disulfide. However, it is unclear ho...

  18. A novel fluorogenic probe for the investigation of free thiols: Application to kinetic measurements of acetylcholinesterase activity.

    Science.gov (United States)

    Mertens, Matthias D; Bierwisch, Anne; Li, Tianwei; Gütschow, Michael; Thiermann, Horst; Wille, Timo; Elsinghorst, Paul W

    2016-02-26

    A novel coumarin-derived thiol probe, based on the thiol-promoted cleavage of a quenching 2,4-dinitrobenzenesulfonyl group is described. The probe shows a sensitive fluorescence turn-on and sufficient solubility in aqueous environments. As a proof of concept, a new assay for AChE activity was developed as a useful addition to the established Ellman method. The observed reaction kinetics followed an asymmetric sigmoidal pattern and were successfully evaluated applying a three parameter Gompertz equation. Providing a linear relationship between the detected fluorescence formation curves and corresponding enzyme activities, this probe appears as a valuable tool for AChE activity measurements. PMID:26494253

  19. Stereoretentive palladium-catalyzed arylation, alkenylation, and alkynylation of 1-thiosugars and thiols using aminobiphenyl palladacycle precatalyst at room temperature.

    Science.gov (United States)

    Bruneau, Alexandre; Roche, Maxime; Hamze, Abdallah; Brion, Jean-Daniel; Alami, Mouad; Messaoudi, Samir

    2015-06-01

    A general and efficient protocol for the palladium-catalyzed functionalization of mono- and polyglycosyl thiols by using the palladacycle precatalyst G3-XantPhos was developed. The C-S bond-forming reaction was achieved rapidly at room temperature with various functionalized (hetero)aryl-, alkenyl-, and alkynyl halides. The functional group tolerance on the electrophilic partner is typically high and anomer selectivities of thioglycosides are high in all cases studied. New sulfur nucleophiles such as thiophenols, alkythiols, and thioaminoacids (cysteine) were also successfully coupled to lead to the most general and practical method yet reported for the functionalization of thiols. PMID:25876554

  20. Monodehydroascorbate reductase 2 and dehydroascorbate reductase 5 are crucial for a mutualistic interaction between Piriformospora indica and Arabidopsis.

    Science.gov (United States)

    Vadassery, Jyothilakshmi; Tripathi, Swati; Prasad, Ram; Varma, Ajit; Oelmüller, Ralf

    2009-08-15

    Ascorbate is a major antioxidant and radical scavenger in plants. Monodehydroascorbate reductase (MDAR) and dehydroascorbate reductase (DHAR) are two enzymes of the ascorbate-glutathione cycle that maintain ascorbate in its reduced state. MDAR2 (At3g09940) and DHAR5 (At1g19570) expression was upregulated in the roots and shoots of Arabidopsis seedlings co-cultivated with the root-colonizing endophytic fungus Piriformospora indica, or that were exposed to a cell wall extract or a culture filtrate from the fungus. Growth and seed production were not promoted by Piriformospora indica in mdar2 (SALK_0776335C) and dhar5 (SALK_029966C) T-DNA insertion lines, while colonized wild-type plants were larger and produced more seeds compared to the uncolonized controls. After 3 weeks of drought stress, growth and seed production were reduced in Piriformospora indica-colonized plants compared to the uncolonized control, and the roots of the drought-stressed insertion lines were colonized more heavily by the fungus than were wild-type plants. Upregulation of the message for the antimicrobial PDF1.2 protein in drought-stressed insertion lines indicated that MDAR2 and DHAR5 are crucial for producing sufficient ascorbate to maintain the interaction between Piriformospora indica and Arabidopsis in a mutualistic state. PMID:19386380

  1. Ligand effects on the stability of thiol-stabilized gold nanoclusters: Au25(SR)18-, Au38(SR)24, and Au102(SR)44

    Science.gov (United States)

    Jung, Jaehoon; Kang, Sunwoo; Han, Young-Kyu

    2012-06-01

    We have studied the electrochemical and thermodynamic stability of Au25(SR)18-, Au38(SR)24, and Au102(SR)44, R = CH3, C6H13, CH2CH2Ph, Ph, PhF, and PhCOOH, in order to examine ligand effects on the stability of thiol-stabilized gold nanoclusters, Aum(SR)n. Aliphatic thiols, in general, have higher electrochemical and thermodynamic stability than aromatic thiols, and the -SCH2CH2Ph thiol is particularly appealing because of its high electrochemical and thermodynamic stability. The stabilization of Aum by nSR for Aum(SR)n can be rationalized by the stabilization of an Au atom by an SR for the simple molecule AuSR, regardless of interligand interaction and system size and shape. Thiol moieties play a strong role in the electron oxidation and reduction of Aum(SR)n. Accounting for the characteristics of thiol ligands is essential for understanding the electronic and thermodynamic stability of thiol-stabilized gold nanoclusters.We have studied the electrochemical and thermodynamic stability of Au25(SR)18-, Au38(SR)24, and Au102(SR)44, R = CH3, C6H13, CH2CH2Ph, Ph, PhF, and PhCOOH, in order to examine ligand effects on the stability of thiol-stabilized gold nanoclusters, Aum(SR)n. Aliphatic thiols, in general, have higher electrochemical and thermodynamic stability than aromatic thiols, and the -SCH2CH2Ph thiol is particularly appealing because of its high electrochemical and thermodynamic stability. The stabilization of Aum by nSR for Aum(SR)n can be rationalized by the stabilization of an Au atom by an SR for the simple molecule AuSR, regardless of interligand interaction and system size and shape. Thiol moieties play a strong role in the electron oxidation and reduction of Aum(SR)n. Accounting for the characteristics of thiol ligands is essential for understanding the electronic and thermodynamic stability of thiol-stabilized gold nanoclusters. Electronic supplementary information (ESI) available: HOMO, LUMO, and HOMO-LUMO gaps; optimized geometries and radial distribution functions of r(Au-Au) for Au25(SR)18-, Au38(SR)24 and Au102(SR)44. See DOI: 10.1039/c2nr30501a

  2. Redox biology of Mycobacterium tuberculosis H37Rv: protein-protein interaction between GlgB and WhiB1 involves exchange of thiol-disulfide

    Science.gov (United States)

    Garg, Saurabh; Alam, Md Suhail; Bajpai, Richa; Kishan, KV Radha; Agrawal, Pushpa

    2009-01-01

    Background Mycobacterium tuberculosis, an intracellular pathogen encounters redox stress throughout its life inside the host. In order to protect itself from the redox onslaughts of host immune system, M. tuberculosis appears to have developed accessory thioredoxin-like proteins which are represented by ORFs encoding WhiB-like proteins. We have earlier reported that WhiB1/Rv3219 is a thioredoxin like protein of M. tuberculosis and functions as a protein disulfide reductase. Generally thioredoxins have many substrate proteins. The current study aims to identify the substrate protein(s) of M. tuberculosis WhiB1. Results Using yeast two-hybrid screen, we identified alpha (1,4)-glucan branching enzyme (GlgB) of M. tuberculosis as a interaction partner of WhiB1. In vitro GST pull down assay confirmed the direct physical interaction between GlgB and WhiB1. Both mass spectrometry data of tryptic digests and in vitro labeling of cysteine residues with 4-acetamido-4' maleimidyl-stilbene-2, 2'-disulfonic acid showed that in GlgB, C95 and C658 are free but C193 and C617 form an intra-molecular disulfide bond. WhiB1 has a C37XXC40 motif thus a C40S mutation renders C37 to exist as a free thiol to form a hetero-disulfide bond with the cysteine residue of substrate protein. A disulfide mediated binary complex formation between GlgB and WhiB1C40S was shown by both in-solution protein-protein interaction and thioredoxin affinity chromatography. Finally, transfer of reducing equivalent from WhiB1 to GlgB disulfide was confirmed by 4-acetamido-4' maleimidyl-stilbene-2, 2'-disulfonic acid trapping by the reduced disulfide of GlgB. Two different thioredoxins, TrxB/Rv1471 and TrxC/Rv3914 of M. tuberculosis could not perform this reaction suggesting that the reduction of GlgB by WhiB1 is specific. Conclusion We conclude that M. tuberculosis GlgB has one intra-molecular disulfide bond which is formed between C193 and C617. WhiB1, a thioredoxin like protein interacts with GlgB and transfers its electrons to the disulfide thus reduces the intra-molecular disulfide bond of GlgB. For the first time, we report that GlgB is one of the in vivo substrate of M. tuberculosis WhiB1. PMID:19121228

  3. Redox biology of Mycobacterium tuberculosis H37Rv: protein-protein interaction between GlgB and WhiB1 involves exchange of thiol-disulfide

    Directory of Open Access Journals (Sweden)

    Kishan KV Radha

    2009-01-01

    Full Text Available Abstract Background Mycobacterium tuberculosis, an intracellular pathogen encounters redox stress throughout its life inside the host. In order to protect itself from the redox onslaughts of host immune system, M. tuberculosis appears to have developed accessory thioredoxin-like proteins which are represented by ORFs encoding WhiB-like proteins. We have earlier reported that WhiB1/Rv3219 is a thioredoxin like protein of M. tuberculosis and functions as a protein disulfide reductase. Generally thioredoxins have many substrate proteins. The current study aims to identify the substrate protein(s of M. tuberculosis WhiB1. Results Using yeast two-hybrid screen, we identified alpha (1,4-glucan branching enzyme (GlgB of M. tuberculosis as a interaction partner of WhiB1. In vitro GST pull down assay confirmed the direct physical interaction between GlgB and WhiB1. Both mass spectrometry data of tryptic digests and in vitro labeling of cysteine residues with 4-acetamido-4' maleimidyl-stilbene-2, 2'-disulfonic acid showed that in GlgB, C95 and C658 are free but C193 and C617 form an intra-molecular disulfide bond. WhiB1 has a C37XXC40 motif thus a C40S mutation renders C37 to exist as a free thiol to form a hetero-disulfide bond with the cysteine residue of substrate protein. A disulfide mediated binary complex formation between GlgB and WhiB1C40S was shown by both in-solution protein-protein interaction and thioredoxin affinity chromatography. Finally, transfer of reducing equivalent from WhiB1 to GlgB disulfide was confirmed by 4-acetamido-4' maleimidyl-stilbene-2, 2'-disulfonic acid trapping by the reduced disulfide of GlgB. Two different thioredoxins, TrxB/Rv1471 and TrxC/Rv3914 of M. tuberculosis could not perform this reaction suggesting that the reduction of GlgB by WhiB1 is specific. Conclusion We conclude that M. tuberculosis GlgB has one intra-molecular disulfide bond which is formed between C193 and C617. WhiB1, a thioredoxin like protein interacts with GlgB and transfers its electrons to the disulfide thus reduces the intra-molecular disulfide bond of GlgB. For the first time, we report that GlgB is one of the in vivo substrate of M. tuberculosis WhiB1.

  4. Poly(ethylene glycol)-based thiol-ene hydrogel coatings-curing chemistry, aqueous stability, and potential marine antifouling applications.

    Science.gov (United States)

    Lundberg, Pontus; Bruin, Anouk; Klijnstra, Job W; Nyström, Andreas M; Johansson, Mats; Malkoch, Michael; Hult, Anders

    2010-03-01

    Photocured thiol-ene hydrogel coatings based on poly(ethylene glycol) (PEG) were investigated for marine antifouling purposes. By varying the PEG length, vinylic end-group, and thiol cross-linker, a library of hydrogel coatings with different structural composition was efficiently accomplished, with or without ester linkages. The thiol-methacrylate and thiol-allyl systems were evaluated with respect to curing, degradation, as well as antifouling properties. Methacrylate-based systems exhibited homopolymerization, whereas allyl-based systems reacted more selectively through thiol-ene couplings reaction. The ester-free hydrogels elucidated higher hydrolytic stability whereas longer PEG chains accelerated the degradation process. The antifouling properties were evaluated by protein adsorption with Bovine serum albumin (BSA) and bioassays with the marine bacteria, Cobetia marina, and the marine diatom, Amphora coffeaeformis; in all tests, longer PEG lengths improved the antifouling properties. PMID:20356297

  5. Glucose-6-phosphate dehydrogenase and glutathione reductase activity in methemoglobin reduction by methylene blue and cyst amine: study on glucose-6-phosphate dehydrogenase-deficient individuals, on normal subjects and on riboflavin-treated subjects

    Directory of Open Access Journals (Sweden)

    Benedito Barraviera

    1988-10-01

    Full Text Available The authors have standardized methods for evaluation of the activity of the glucose-6-phosphate dehydrogenase and of glutathione reductase. The general principle of the first method was based on methemoglobin formation by sodium nitrite followed by stimulation of the glucose-6-phosphate dehydrogenase with methylene blue. Forty six adults (23 males and 23 females were studied. Subjects were not G6PD deficient and were aged 20 to 30 years. The results showed that methemoglobin reduction by methylene blue was 154.40 and 139.90 mg/min (p<0.05 for males and females, respectively, in whole blood, and 221.10 and 207.85 mg/min (n.s., respectively, in washed red cells. These data showed that using washed red cells and 0.7g% sodium nitrite concentration produced no differences between sexes and also shortened reading time for the residual amount of methemoglobin to 90 minutes. Glutathione reductase activity was evaluated on the basis of the fact that cystamine (a thiol agent binds to the SH groups of hemoglobin, forming complexes. These complexes are reversed by the action of glutathione reductase, with methemoglobin reduction occurring simultaneously with this reaction. Thirty two adults (16 males and 16 females were studied. Subjects were not G6PD deficient and were aged 20 to 30 years. Methemoglobin reduction by cystamine was 81.27 and 91.13 mg/min (p<0.01 for males and females, respectively. These data showed that using washed red cells and 0.1 M cystamine concentration permits a reading of the residual amount of methemoglobin at 180 minutes of incubation. Glutathione reductase activity was evaluated by methemoglobin reduction by cystamine in 14 females before and after treatment with 10 mg riboflavin per day for 8 days. The results were 73.69 and 94.26 jug/min (p<0.01 before and after treatment, showing that riboflavin treatment increase glutathione reductase activity even in normal individuals. Three Black G6PD-deficient individuals (2 males and 1 female were also studied. The G6PD and glutathione reductase were partially activated, the change being more intense in males. On the basis of race and of the laboratory characteristics observed, it is possible to suggest that the G6PD deficiency of these individuals is of the African type and that the female is heterozygous for this deficiency. Analysis of the results as a whole permitted us to conclude that the methods proposed here were efficient for evaluating the activity of the glucose-6-phosphate dehydrogenase and of glutathione reductase. The latter is dependent on the pentose pathway, which generates NADPH, and on riboflavin, a FAD precursor vitamin.

  6. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase from Arabidopsis thaliana is structurally distinct from the yeast and animal enzymes.

    OpenAIRE

    Learned, R M; Fink, G. R.

    1989-01-01

    We have isolated the Arabidopsis thaliana gene (HMG1) encoding 3-hydroxy-3-methylglutaryl-CoA reductase [HMG-CoA reductase; (S)-mevalonate:NAD+ oxido-reductase (CoA-acylating), EC 1.1.1.88], the catalyst of the first committed step in isoprenoid biosynthesis. cDNA copies of the plant gene were identified by hybridization with a short, highly conserved segment of yeast HMG-CoA reductase as probe. DNA sequence analysis reveals that the COOH-terminal domain of the Arabidopsis HMG-CoA reductase (...

  7. Two methylenetetrahydrofolate reductase gene (MTHFR) polymorphisms, schizophrenia and bipolar disorder

    DEFF Research Database (Denmark)

    Jönsson, Erik G; Larsson, Kristina; Vares, Maria; Hansen, Thomas; Wang, August G; Djurovic, Srdjan; Rønningen, Kjersti S; Andreassen, Ole A; Agartz, Ingrid; Werge, Thomas; Terenius, Lars; Hall, Håkan

    disorder. In a replication attempt the MTHFR C677T and A1298C SNPs were analyzed in three Scandinavian schizophrenia case-control samples. In addition, Norwegian patients with bipolar disorder were investigated. There were no statistically significant allele or genotype case-control differences. The...... present Scandinavian results do not verify previous associations between the putative functional MTHFR gene polymorphisms and schizophrenia or bipolar disorder. However, when combined with previous studies in meta-analyses there is still evidence for association between the MTHFR C677T polymorphism and......Recent meta-analyses of the methylenetetrahydrofolate reductase gene (MTHFR) have suggested association between two of its functional single gene polymorphisms (SNPs; C677T and A1298C) and schizophrenia. Studies have also suggested association between MTHFR C677T and A1298C variation and bipolar...

  8. Structure of a bacterial homologue of vitamin K epoxide reductase

    Energy Technology Data Exchange (ETDEWEB)

    Li, Weikai; Schulman, Sol; Dutton, Rachel J.; Boyd, Dana; Beckwith, Jon; Rapoport, Tom A. (Harvard-Med); (HHMI)

    2010-03-19

    Vitamin K epoxide reductase (VKOR) generates vitamin K hydroquinone to sustain {gamma}-carboxylation of many blood coagulation factors. Here, we report the 3.6 {angstrom} crystal structure of a bacterial homologue of VKOR from Synechococcus sp. The structure shows VKOR in complex with its naturally fused redox partner, a thioredoxin-like domain, and corresponds to an arrested state of electron transfer. The catalytic core of VKOR is a four transmembrane helix bundle that surrounds a quinone, connected through an additional transmembrane segment with the periplasmic thioredoxin-like domain. We propose a pathway for how VKOR uses electrons from cysteines of newly synthesized proteins to reduce a quinone, a mechanism confirmed by in vitro reconstitution of vitamin K-dependent disulphide bridge formation. Our results have implications for the mechanism of the mammalian VKOR and explain how mutations can cause resistance to the VKOR inhibitor warfarin, the most commonly used oral anticoagulant.

  9. Crystal structure of isoflavone reductase from alfalfa (Medicago sativa L.).

    Science.gov (United States)

    Wang, Xiaoqiang; He, Xianzhi; Lin, Jianqiao; Shao, Hui; Chang, Zhenzhan; Dixon, Richard A

    2006-05-19

    Isoflavonoids play important roles in plant defense and exhibit a range of mammalian health-promoting activities. Isoflavone reductase (IFR) specifically recognizes isoflavones and catalyzes a stereospecific NADPH-dependent reduction to (3R)-isoflavanone. The crystal structure of Medicago sativa IFR with deletion of residues 39-47 has been determined at 1.6A resolution. Structural analysis, molecular modeling and docking, and comparison with the structures of other NADPH-dependent enzymes, defined the putative binding sites for co-factor and substrate and potential key residues for enzyme activity and substrate specificity. Further mutagenesis has confirmed the role of Lys144 as a catalytic residue. This study provides a structural basis for understanding the enzymatic mechanism and substrate specificity of IFRs as well as the functions of IFR-like proteins. PMID:16600295

  10. Genetic Evidence for a Molybdopterin-Containing Tellurate Reductase

    Science.gov (United States)

    Theisen, Joanne; Zylstra, Gerben J.

    2013-01-01

    The genetic identity and cofactor composition of the bacterial tellurate reductase are currently unknown. In this study, we examined the requirement of molybdopterin biosynthesis and molybdate transporter genes for tellurate reduction in Escherichia coli K-12. The results show that mutants deleted of the moaA, moaB, moaE, or mog gene in the molybdopterin biosynthesis pathway lost the ability to reduce tellurate. Deletion of the modB or modC gene in the molybdate transport pathway also resulted in complete loss of tellurate reduction activity. Genetic complementation by the wild-type sequences restored tellurate reduction activity in the mutant strains. These findings provide genetic evidence that tellurate reduction in E. coli involves a molybdoenzyme. PMID:23475618

  11. A calibration curve for immobilized dihydrofolate reductase activity assay

    Directory of Open Access Journals (Sweden)

    Priyanka Singh

    2015-09-01

    Full Text Available An assay was developed for measuring the active-site concentration, activity, and thereby the catalytic turnover rate (kcat of an immobilized dihydrofolate reductase model system (Singh et al., (2015, Anal. Biochem. This data article contains a calibration plot for the developed assay. In the calibration plot rate is plotted as a function of DHFR concentration and shows linear relationship. The concentration of immobilized enzyme was varied by using 5 different size mica chips. The dsDNA concentration was the same for all chips, assuming that the surface area of the mica chip dictates the resulting amount of bound enzyme (i.e. larger sized chip would have more bound DHFR. The activity and concentration of each chip was measured.

  12. A calibration curve for immobilized dihydrofolate reductase activity assay

    Science.gov (United States)

    Singh, Priyanka; Morris, Holly; Tivanski, Alexei V.; Kohen, Amnon

    2015-01-01

    An assay was developed for measuring the active-site concentration, activity, and thereby the catalytic turnover rate (kcat) of an immobilized dihydrofolate reductase model system (Singh et al., (2015), Anal. Biochem). This data article contains a calibration plot for the developed assay. In the calibration plot rate is plotted as a function of DHFR concentration and shows linear relationship. The concentration of immobilized enzyme was varied by using 5 different size mica chips. The dsDNA concentration was the same for all chips, assuming that the surface area of the mica chip dictates the resulting amount of bound enzyme (i.e. larger sized chip would have more bound DHFR). The activity and concentration of each chip was measured. PMID:26217755

  13. Treatment of diabetic autonomic neuropathy with an aldose reductase inhibitor.

    Science.gov (United States)

    Faes, T J; Yff, G A; DeWeerdt, O; Lanting, P; Heimans, J J; Bertelsmann, F W

    1993-01-01

    To evaluate the effects of the aldose reductase inhibitor Ponalrestat (Statil) on diabetic autonomic neuropathy, a double-blind placebo controlled trial was carried out on a group of 34 diabetic patients with documented cardiac autonomic neuropathy. After a 4-week, placebo run-in period, patients were randomised for treatment with 600 mg Statil or placebo for another 24 weeks. Moreover, the reliability of the autonomic nerve function tests was investigated by comparing the results at onset and at week 4. Fifteen patients treated with Statil and 12 with placebo completed the study. Neither symptom scores nor cardiovascular reflexes, pupil reflexes and skin vasomotor reflexes improved after Statil therapy, which led us to conclude that Statil is not effective in the treatment of diabetic autonomic neuropathy. Reliability coefficients for cardiovascular reflexes and pupil reflex showed high values, ranging from 60% to 80%. Therefore these methods are recommended in future therapy trials. PMID:8482988

  14. Isolation and expression of the Pneumocystis carinii dihydrofolate reductase gene

    DEFF Research Database (Denmark)

    Edman, J C; Edman, U

    1989-01-01

    Pneumocystis carinii dihydrofolate reductase (DHFR; 5,6,7,8-tetrahydrofolate: NADP+ oxidoreductase, EC 1.5.1.3) cDNA sequences have been isolated by their ability to confer trimethoprim resistance to Escherichia coli. Consistent with the recent conclusion that P. carinii is a member of the Fungi, sequence analysis and chromosomal localization show that DHFR is neither physically nor genetically linked to thymidylate synthase. Expression of recombinant P. carinii DHFR in heterologous hosts provides an abundant source of the enzyme that may form a basis for the development of new therapies for this enigmatic pathogen. Studies with the recombinant enzyme show that trimethoprim is a very poor inhibitor of P. carinii DHFR and, in fact, is a more potent inhibitor of human DHFR.

  15. Mechanism of inhibition of ribonucleotide reductase with motexafin gadolinium (MGd)

    International Nuclear Information System (INIS)

    Motexafin gadolinium (MGd) is an expanded porphyrin anticancer agent which selectively targets tumor cells and works as a radiation enhancer, with promising results in clinical trials. Its mechanism of action is oxidation of intracellular reducing molecules and acting as a direct inhibitor of mammalian ribonucleotide reductase (RNR). This paper focuses on the mechanism of inhibition of RNR by MGd. Our experimental data present at least two pathways for inhibition of RNR; one precluding subunits oligomerization and the other direct inhibition of the large catalytic subunit of the enzyme. Co-localization of MGd and RNR in the cytoplasm particularly in the S-phase may account for its inhibitory properties. These data can elucidate an important effect of MGd on the cancer cells with overproduction of RNR and its efficacy as an anticancer agent and not only as a general radiosensitizer.

  16. Regulation of ribonucleotide reductase by Spd1 involves multiple mechanisms

    DEFF Research Database (Denmark)

    Nestoras, Konstantinos; Mohammed, Asma Hadi

    2010-01-01

    The correct levels of deoxyribonucleotide triphosphates and their relative abundance are important to maintain genomic integrity. Ribonucleotide reductase (RNR) regulation is complex and multifaceted. RNR is regulated allosterically by two nucleotide-binding sites, by transcriptional control, and by small inhibitory proteins that associate with the R1 catalytic subunit. In addition, the subcellular localization of the R2 subunit is regulated through the cell cycle and in response to DNA damage. We show that the fission yeast small RNR inhibitor Spd1 is intrinsically disordered and regulates R2 nuclear import, as predicted by its relationship to Saccharomyces cerevisiae Dif1. We demonstrate that Spd1 can interact with both R1 and R2, and show that the major restraint of RNR in vivo by Spd1 is unrelated to R2 subcellular localization. Finally, we identify a new behavior for RNR complexes that potentially provides yet another mechanism to regulate dNTP synthesis via modulation of RNR complex architecture.

  17. Pulse radiolysis studies on superoxide reductase from Treponema pallidum

    CERN Document Server

    Nivière, V; Fontecave, M; Houée-Levin, C

    2015-01-01

    Superoxide reductases (SORs) are small metalloenzymes, which catalyze reduction of O2*- to H2O2. The reaction of the enzyme from Treponema pallidum with superoxide was studied by pulse radiolysis methods. The first step is an extremely fast bi-molecular reaction of the ferrous center with O2, with a rate constant of 6 x 10 (8) M(-1) s(-1). A first intermediate is formed which is converted to a second one with a slower rate constant of 4800 s(-1). This latter value is 10 times higher than the corresponding one previously reported in the case of SOR from Desulfoarculus baarsii. The reconstituted spectra for the two intermediates are consistent with formation of transient iron-peroxide species.

  18. Synthesis and ribonucleotide reductase inhibitory activity of thiosemicarbazones.

    Science.gov (United States)

    Krishnan, Kesavan; Prathiba, Kumari; Jayaprakash, Venkatesan; Basu, Arijit; Mishra, Nibha; Zhou, Bingsen; Hu, Shuya; Yen, Yun

    2008-12-01

    Ribonucleotide reductase (RR) is an important therapeutic target for anticancer drugs. The structure of human RR features a 1:1 complex of two homodimeric subunits, hRRM1 and hRRM2. Prokaryotically expressed and highly purified recombinant human RR subunits, hRRM1 and hRRM2, were used for holoenzyme-based [(3)H]CDP reduction in vitro assay. Ten new thiosemicarbazones (7-16) were synthesized and screened for their RR inhibitory activity. Two thiosemicarbazones derived from p-hydroxy benzaldehyde (9 and 10) were found to be active but less potent than the standard, Hydroxyurea (HU). Guided by the activity of compounds 9 and 10, 11 new thiosemicarbazones (17-27) derived from p-hydroxy benzaldehyde were prepared and screened for their RR inhibitory activity. All the 11 compounds were more potent than HU. PMID:18976907

  19. Alterations in cytoskeletal organization and homeostasis of cellular thiols in cadmium-resistant cells.

    Science.gov (United States)

    Li, W; Kagan, H M; Chou, I N

    1994-05-01

    To understand further the mechanisms of cadmium toxicity, cytoskeletal organization and homeostasis of cellular thiols were examined in cadmium-resistant cells isolated from Swiss mouse 3T3 cells by incubation in graded concentrations of CdCl2 (Cd2+) in the culture medium. Cd(2+)-resistant cells displayed profound alterations in their cytoskeletal organization characterized by the appearance of many elongated, tadpole-shaped cells with a high density of microtubules (MT) and microfilaments (MF), with the former being mainly distributed along the long axis of the cell. Exposure of Cd(2+)-resistant cells to 50 microM Cd2+ for 16 hr did not cause apparent cytoskeletal perturbations, whereas treatment of parental cells with 5 microM Cd2+ for the same duration produced a severe loss of MT and smeared patches of MF. Thus, the cytoskeleton of Cd(2+)-resistant cells is markedly more preserved and protected against Cd2+ damage than that of their parental counterparts. Cd(2+)-resistant cells contained a higher basal level of protein sulfhydryls (PSH) in both the cytoskeletal and cytosolic fractions than the parental cells. Exposure to 50 microM Cd2+ further increased cellular PSH contents, reaching 192 and 215% of the basal levels for the cytoskeletal and cytosolic fractions, respectively. Although 5 microM Cd2+ exposure also elevated the amounts of PSH in parental cells, the "absolute" values were still below the corresponding basal levels in Cd(2+)-resistant cells. Furthermore, Cd(2+)-resistant cells also exhibited enhanced basal levels of metallothionein and cellular glutathione (GSH), amounting to 19- and 2.1-fold of the parental basal levels, respectively. Thus, the Cd(2+)-resistant cells produced larger quantities of both protein and nonprotein thiol-containing elements than the parental cells. Interestingly, exposure of Cd(2+)-resistant cells to 50 microM Cd2+ also further increased metallothionein and cellular GSH to 178 and 138% of the basal levels, respectively. Based on the affinity of Cd2+ for sulfhydryls as a mechanism of Cd2+ toxicity, we propose that the coordinately increased levels of metallothionein, GSH, and PSH in Cd(2+)-resistant cells would provide a mechanistic basis for the homeostasis of cellular thiols which may collectively contribute to the cytoskeletal preservation by protecting the cytoskeleton from Cd2+ insult. PMID:8184421

  20. Pyrroline-5-Carboxylate Reductase in Chlorella autotrophica and Chlorella saccharophila in Relation to Osmoregulation.

    Science.gov (United States)

    Laliberté, G; Hellebust, J A

    1989-11-01

    Pyrroline-5-carboxylate (P5C) reductase (EC 1.5.1.2), which catalyzes the reduction of P5C to proline, was partially purified from two Chlorella species; Chlorella autotrophica, a euryhaline marine alga that responds to increases in salinity by accumulating proline and ions, and Chlorella saccharophila, which does not accumulate proline for osmoregulation. From the elution profile of this enzyme from an anion exchange column in Tris-HCl buffer (pH 7.6), containing sorbitol and glycine betaine, it was shown that P5C reductase from C. autotrophica was a neutral protein whereas the enzyme from C. saccharophila was negatively charged. The kinetic mechanisms of the reductase was characteristic of a ping-pong mechanism with double competitive substrate inhibition. Both enzymes showed high specificity for NADH as cofactor. The affinities of the reductases for their substrates did not change when the cells were grown at different salinities. In both algae, the apparent K(m) values of the reductase for P5C and NADH were 0.17 and 0.10 millimolar, respectively. A fourfold increase in maximal velocity of the reductase was observed when C. autotrophica was transferred from 50 to 150% artificial sea water. Even though the reductase was inhibited by NaCl, KCl, and proline, it still showed appreciable activity in the presence of these compounds at molar concentrations. A possible role for the regulation of proline synthesis at the step catalyzed by P5C reductase is discussed in relation to the specificity of P5C reductase for NADH and its responses to salt treatments. PMID:16667157