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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?

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

    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

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

    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

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

    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.

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

    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

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

    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

  7. Cysteine reactivity and thiol-disulfide interchange pathways in AhpF and AhpC of the bacterial alkyl hydroperoxide reductase system†

    Jönsson, Thomas J.; Ellis, Holly R.; Poole, Leslie B.

    2007-01-01

    AhpC and AhpF from Salmonella typhimurium undergo a series of electron transfers to catalyze the pyridine nucleotide-dependent reduction of hydroperoxide substrates. AhpC, the peroxide-reducing (peroxiredoxin) component of this alkyl hydroperoxidase system, is an important scavenger of endogenous hydrogen peroxide in bacteria and acts through a reactive, peroxidatic cysteine, Cys46, and a second cysteine, Cys165, that forms an active site disulfide bond. AhpF, a separate disulfide reductase p...

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

    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

  9. Thiol biochemistry of prokaryotes

    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.

  10. Electroanalysis of Plant Thiols

    Rene Kizek*; Miroslava Beklova; Libuse Trnkova*; Vojtech Adam; Josef Zehnalek; Ladislav Havel; Jiri Pikula; Jiri Baloun; Karel Stejskal; Ondrej Zitka; Pavel Hanustiak; Vaclav Diopan; Dalibor Huska; Veronika Supalkova

    2007-01-01

    Due to unique physico-chemical properties of –SH moiety thiols comprise widegroup of biologically important compounds. A review devoted to biological functions ofglutathione and phytochelatins with literature survey of methods used to analysis of thesecompounds and their interactions with cadmium(II) ions and Murashige-Skoog medium ispresented. For these purposes electrochemical techniques are used. Moreover, we revealedthe effect of three different cadmium concentrations (0, 10 and 100 ...

  11. A comprehensive study of thiol reduction gene expression under stress conditions in Arabidopsis thaliana.

    Belin, C; Bashandy, T; Cela, J; Delorme-Hinoux, V; Riondet, C; Reichheld, J P

    2015-02-01

    Thiol reduction proteins are key regulators of the redox state of the cell, managing development and stress response programs. In plants, thiol reduction proteins, namely thioredoxin (TRX), glutaredoxin (GRX), and their respective reducers glutathione reductase (GR) and thioredoxin reductase (TR), are organized in complex multigene families. In order to decipher the function of the different proteins, it is necessary to have a clear picture of their respective expression profiles. By collecting information from gene expression databases, we have performed a comprehensive in silico study of the expression of all members of different classes of thiol reduction genes (TRX, GRX) in Arabidopsis thaliana. Tissue expression profiles and response to many biotic and abiotic stress conditions have been studied systematically. Altogether, the significance of our data is discussed with respect to published biochemical and genetic studies. PMID:24428628

  12. Electroanalysis of Plant Thiols

    Rene Kizek

    2007-06-01

    Full Text Available Due to unique physico-chemical properties of –SH moiety thiols comprise widegroup of biologically important compounds. A review devoted to biological functions ofglutathione and phytochelatins with literature survey of methods used to analysis of thesecompounds and their interactions with cadmium(II ions and Murashige-Skoog medium ispresented. For these purposes electrochemical techniques are used. Moreover, we revealedthe effect of three different cadmium concentrations (0, 10 and 100 μM on cadmiumuptake and thiols content in maize plants during 192 hours long experiments usingdifferential pulse anodic stripping voltammetry to detect cadmium(II ions and highperformance liquid chromatography with electrochemical detection to determineglutathione. Cadmium concentration determined in tissues of the plants cultivated innutrient solution containing 10 μM Cd was very low up to 96 hours long exposition andthen the concentration of Cd markedly increased. On the contrary, the addition of 100 μMCd caused an immediate sharp increase in all maize plant parts to 96 hours Cd expositionbut subsequently the Cd concentration increased more slowly. A high performance liquidchromatography with electrochemical detection was used for glutathione determination intreated maize plants after 96 and 192 hours of treatment. The highest total content of glutathione per one plant was 6 μg (96 h, 10 μM Cd in comparison with non-treated plant (control where glutathione content was 1.5 μg. It can be concluded that electrochemical techniques have proved to be useful to analyse plant thiols.

  13. Electroanalysis of Plant Thiols

    Supalkova, Veronika; Huska, Dalibor; Diopan, Vaclav; Hanustiak, Pavel; Zitka, Ondrej; Stejskal, Karel; Baloun, Jiri; Pikula, Jiri; Havel, Ladislav; Zehnalek, Josef; Adam, Vojtech; Trnkova, Libuse; Beklova, Miroslava; Kizek, Rene

    2007-01-01

    Due to unique physico-chemical properties of –SH moiety thiols comprise wide group of biologically important compounds. A review devoted to biological functions of glutathione and phytochelatins with literature survey of methods used to analysis of these compounds and their interactions with cadmium(II) ions and Murashige-Skoog medium is presented. For these purposes electrochemical techniques are used. Moreover, we revealed the effect of three different cadmium concentrations (0, 10 and 100 μM) on cadmium uptake and thiols content in maize plants during 192 hours long experiments using differential pulse anodic stripping voltammetry to detect cadmium(II) ions and high performance liquid chromatography with electrochemical detection to determine glutathione. Cadmium concentration determined in tissues of the plants cultivated in nutrient solution containing 10 μM Cd was very low up to 96 hours long exposition and then the concentration of Cd markedly increased. On the contrary, the addition of 100 μM Cd caused an immediate sharp increase in all maize plant parts to 96 hours Cd exposition but subsequently the Cd concentration increased more slowly. A high performance liquid chromatography with electrochemical detection was used for glutathione determination in treated maize plants after 96 and 192 hours of treatment. The highest total content of glutathione per one plant was 6 μg (96 h, 10 μM Cd) in comparison with non-treated plant (control) where glutathione content was 1.5 μg. It can be concluded that electrochemical techniques have proved to be useful to analyse plant thiols.

  14. Quantification of thiols and disulfides

    Winther, Jakob R.; Thorpe, Colin

    2014-01-01

    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....

  15. Thiol Reactive Probes and Chemosensors

    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.

  16. Thiol redox homeostasis in neurodegenerative disease

    Gethin J. McBean

    2015-08-01

    Full Text Available This review provides an overview of the biochemistry of thiol redox couples and the significance of thiol redox homeostasis in neurodegenerative disease. The discussion is centred on cysteine/cystine redox balance, the significance of the xc− cystine–glutamate exchanger and the association between protein thiol redox balance and neurodegeneration, with particular reference to Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and glaucoma. The role of thiol disulphide oxidoreductases in providing neuroprotection is also discussed.

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

    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.

  18. Hypochlorite-induced oxidation of thiols

    Davies, Michael Jonathan; Hawkins, C L

    2000-01-01

    -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...

  19. Protein Thiol Modifications Visualized In Vivo

    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.

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

    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...

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

    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

  2. Herpes simplex ribonucleotide reductase

    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...

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

    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

  4. Photopolymerized Thiol-Ene Systems as Shape Memory Polymers

    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...

  5. Quantifying the global cellular thioldisulfide status

    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 thioldisulfide status in cultured mammalian cells. We have quantified the absolute levels of protein thiols, protein disu...

  6. Glutathione reductase: solvent equilibrium and kinetic isotope effects

    Glutathione reductase catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG). The kinetic mechanism is ping-pong, and we have investigated the rate-limiting nature of proton-transfer steps in the reactions catalyzed by the spinach, yeast, and human erythrocyte glutathione reductases using a combination of alternate substrate and solvent kinetic isotope effects. With NADPH or GSSG as the variable substrate, at a fixed, saturating concentration of the other substrate, solvent kinetic isotope effects were observed on V but not V/K. Plots of Vm vs mole fraction of D2O (proton inventories) were linear in both cases for the yeast, spinach, and human erythrocyte enzymes. When solvent kinetic isotope effect studies were performed with DTNB instead of GSSG as an alternate substrate, a solvent kinetic isotope effect of 1.0 was observed. Solvent kinetic isotope effect measurements were also performed on the asymmetric disulfides GSSNB and GSSNP by using human erythrocyte glutathione reductase. The Km values for GSSNB and GSSNP were 70 microM and 13 microM, respectively, and V values were 62 and 57% of the one calculated for GSSG, respectively. Both of these substrates yield solvent kinetic isotope effects greater than 1.0 on both V and V/K and linear proton inventories, indicating that a single proton-transfer step is still rate limiting. These data are discussed in relationship to the chemical mechanism of GSSG reduction and the identity of the proton-transfer step whose rate is sensitive to solvent isotopic composition. Finally, the solvent equilibrium isotope effect measured with yeast glutathione reductase is 4.98, which allows us to calculate a fractionation factor for the thiol moiety of GSH of 0.456

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

    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.

  8. Synthesis of bisnaphthyl based thiol stabilized gold nanoparticles

    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)

  9. Human brain aldehyde reductases: relationship to succinic semialdehyde reductase and aldose reductase.

    Hoffman, P L; Wermuth, B; von Wartburg, J P

    1980-08-01

    Human brain contains multiple forms of aldehyde-reducing enzymes. One major form (AR3), as previously shown, has properties that indicate its identity with NADPH-dependent aldehyde reductase isolated from brain and other organs of various species; i.e., low molecular weight, use of NADPH as the preferred cofactor, and sensitivity to inhibition by barbiturates. A second form of aldehyde reductase ("SSA reductase") specifically reduces succinic semialdehyde (SSA) to produce gamma-hydroxybutyrate. This enzyme form has a higher molecular weight than AR3, and uses NADH as well as NADPH as cofactor. SSA reductase was not inhibited by pyrazole, oxalate, or barbiturates, and the only effective inhibitor found was the flavonoid quercetine. Although AR3 can also reduce SSA, the relative specificity of SSA reductase may enhance its in vivo role. A third form of human brain aldehyde reductase, AR2, appears to be comparable to aldose reductases characterized in several species, on the basis of its activity pattern with various sugar aldehydes and its response to characteristic inhibitors and activators, as well as kinetic parameters. This enzyme is also the most active in reducing the aldehyde derivatives of biogenic amines. These studies suggest that the various forms of human brain aldehyde reductases may have specific physiological functions. PMID:6778961

  10. Synthesis of polylactide with thiol end groups

    Popelka, Štěpán; Rypáček, František

    2003-01-01

    Roč. 68, č. 6 (2003), s. 1131-1140. ISSN 0010-0765 R&D Projects: GA ČR GA203/99/0576 Institutional research plan: CEZ:AV0Z4050913 Keywords : polylactides * thiol-functionalized polymers * end group modification Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.041, year: 2003

  11. Nuclear thiol redox systems in plants.

    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

  12. The 2-Cys Peroxiredoxin Alkyl Hydroperoxide Reductase C Binds Heme and Participates in Its Intracellular Availability in Streptococcus agalactiae*

    Lechardeur, Delphine; Fernandez, Annabelle; Robert, Bruno; Gaudu, Philippe; Trieu-Cuot, Patrick,; Lamberet, Gilles; Gruss, Alexandra

    2010-01-01

    Heme is a redox-reactive molecule with vital and complex roles in bacterial metabolism, survival, and virulence. However, few intracellular heme partners were identified to date and are not well conserved in bacteria. The opportunistic pathogen Streptococcus agalactiae (group B Streptococcus) is a heme auxotroph, which acquires exogenous heme to activate an aerobic respiratory chain. We identified the alkyl hydroperoxide reductase AhpC, a member of the highly conserved thiol-dependent 2-Cys p...

  13. Microfluidic devices using thiol-ene polymers

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

    2013-12-01

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

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

    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

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

    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...... lead to close to complete non-catalytic monolayer interfacial electron transfer function and electrocatalysis with activity approaching enzyme activity in homogeneous solution. Thiophenol (combined hydrophobic stacking and interdispersed water molecules), 4-methyl-thiophenol (hydrophobic and water...

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

    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.

  17. Tunable degradation of maleimide-thiol adducts in reducing environments

    Baldwin, Aaron D.; Kiick, Kristi L.

    2011-01-01

    Addition chemistries are widely used in preparing biological conjugates, and in particular, maleimide-thiol adducts have been widely employed. Here we show that the resulting succinimide thioether formed by a Michael type addition of a thiol to N-ethylmaleimide (NEM), generally accepted as stable, can in fact undergo retro and exchange reactions in the presence of other thiol compounds at physiological pH and temperature, offering a novel strategy for controlled release. Model studies (1H NMR...

  18. Alkyl Hydroperoxide Reductase Repair by Helicobacter pylori Methionine Sulfoxide Reductase

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

    2013-01-01

    Protein exposure to oxidants such as HOCl leads to formation of methionine sulfoxide (MetSO) residues, which can be repaired by methionine sulfoxide reductase (Msr). A Helicobacter pylori msr strain was more sensitive to HOCl-mediated killing than the parent. Because of its abundance in H. pylori and its high methionine content, alkyl hydroperoxide reductase C (AhpC) was hypothesized to be prone to methionine oxidation. AhpC was expressed as a recombinant protein in Escherichia coli. AhpC ...

  19. Isolated menthone reductase and nucleic acid molecules encoding same

    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.

  20. Enrichment of O-GlcNAc-modified peptides using novel thiol-alkyne and thiol-disulfide exchange.

    Tsumoto, Hiroki; Ogasawara, Daisuke; Hashii, Noritaka; Suzuki, Takayoshi; Akimoto, Yoshihiro; Endo, Tamao; Miura, Yuri

    2015-07-01

    We have developed a selective method for the enrichment of O-linked β-N-acetylglucosamine (O-GlcNAc)-modified peptides, which uses a newly synthesized thiol-alkyne and a thiol-disulfide exchange. First, O-GlcNAc-modified peptides were enzymatically labeled with an azide-containing GalNAc analog. Then, the azide moiety was reacted with thiol-alkyne through a copper(I)-catalyzed azide-alkyne cycloaddition. The thiol-modified peptides were enriched with thiol-reactive resin through a thiol-disulfide exchange. At least 500fmol of O-GlcNAc-modified peptides was selectively isolated from α-crystallin tryptic peptides and detected by mass spectrometry. This novel enrichment strategy could be used for O-GlcNAcome analysis of biological samples. PMID:25980911

  1. Thiol groups of gizzard myosin heavy chains

    Bailin, G.

    1986-05-01

    Proteolysis of phosphorylated and /sup 3/H-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 (N/sub 2/ph) 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/sup +/-ATPase activity was inhibited. Thiolysis of phosphorylated and dinitrophenylated myosin with 2-mercaptoethanol removed 60% and 25% of the N/sub 2/ph group from the N-terminal and M/sub r/ 66,000 fragments of the heavy chain, respectively, when 48% of the K/sup +/-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 /sup 3/H-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 N/sub 2/ph 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.

  2. Thiol groups of gizzard myosin heavy chains

    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

  3. Thiol-ene-based monolithic microreactors

    Novotný, Jakub; Lafleur, J. P.; Kutter, J. P.

    Brno : Institute of Analytical Chemistry AS CR, 2014 - (Foret, F.; Křenková, J.; Drobníková, I.; Guttman, A.; Klepárník, K.), s. 53-55 ISBN 978-80-904959-2-0. [CECE 2014. International Interdisciplinary Meeting on Bioanalysis /11./. Brno (CZ), 20.10.2014-22.10.2014] Institutional support: RVO:68081715 Keywords : thiol-ene * monolith * enzyme immobilization Subject RIV: CB - Analytical Chemistry, Separation http://www.ce-ce.org/CECE2014/CECE%202014%20proceedings_full.pdf

  4. Atom precise platinum-thiol crowns.

    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

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

    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)

  6. Characterization of a broad-range disulfide reductase from Streptomyces clavuligerus and its possible role in beta-lactam antibiotic biosynthesis.

    Aharonowitz, Y; Av-Gay, Y; Schreiber, R; Cohen, G.

    1993-01-01

    Streptomyces clavuligerus is a potent producer of penicillin and cephalosporin antibiotics. A key step in the biosynthesis of these beta-lactam compounds is the cyclization of the thiol tripeptide delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV) to isopenicillin N by the enzyme isopenicillin N synthase (IPNS). However, bis-ACV, the oxidized disulfide form of the tripeptide, is not a substrate for IPNS. We show here that S. clavuligerus possesses an NADPH-dependent disulfide reductase of...

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

    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

  8. On radiation protection of cells in vitro with thiols

    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

  9. Kinetics of cisplatin binding to cellular DNA and modulations by thiol-blocking agents and thiol drugs.

    Sadowitz, Peter D; Hubbard, Bradley A; Dabrowiak, James C; Goodisman, Jerry; Tacka, Kirk A; Aktas, Mehmet K; Cunningham, Mary J; Dubowy, Ronald L; Souid, Abdul-Kader

    2002-02-01

    DNA platination by cisplatin (CDDP) was investigated in peripheral blood mononuclear cells and ovarian cancer cells using atomic absorption spectroscopy. Plots showing the amount of platinum (Pt) bound to DNA versus the molar concentration of cisplatin in the incubation medium ([CDDP]) were nonlinear. For [CDDP] < about 5 microM, the amount of Pt bound to DNA increased slowly with added drug. However, for larger [CDDP], the slope of the plot increased significantly. To study the role of thiols in affecting cisplatin binding to DNA, cells were treated with N-ethylmaleimide, which modifies thiol groups, rendering them incapable of binding cisplatin. Analysis using high-pressure liquid chromatography showed that approximately 99% of cellular glutathione was modified by N-ethylmaleimide. A plot of the amount of Pt bound to DNA versus [CDDP] for thiol-blocked cells is linear, with a slope similar to that of unblocked cells at high [CDDP]. Neither S-2-(3 aminopropylamino)ethanethiol (WR-1065) nor mesna, when added at clinically achievable concentrations (i.e., < approximately 300 microM), affected DNA platination. However, DNA platination was totally abolished by millimolar concentrations of the drug thiols (approximately 1.25 mM WR-1065 or approximately 5 mM mesna). Thus, the data show that endogenous thiols intercept cellular cisplatin, but this mechanism is less important at high [CDDP]. Moreover, therapeutic concentrations of drug thiols do not significantly affect DNA platination. A simple model that reproduces the experimental results of the amount of cisplatin binding to DNA as a function of [CDDP], time, and thiol content is proposed. The model takes into account passage of cisplatin and thiols through the cell membrane, binding of cisplatin to cellular thiols, and platination of DNA. PMID:11792689

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

    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...

  11. Fatty acyl-CoA reductase

    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.

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

    Valero-Ruiz, Edelmira; Gonzlez-Snchez, Mara 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

  13. Facially amphiphilic thiol capped gold and silver nanoparticles

    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.

  14. Intracellular thiols: involvement in drug metabolism and radiation response

    Nitro compunds are activated by coupled enzyme reactions to oxygen reactive intermediates leading to the formation of peroxide, under aerobic conditions, and to the depletion of thiols, under anaerobic conditions. Some nitro compounds as substrates for glutathione-S-transferase, show peroxide production without prior thiol removal. Other drugs reacting spontaneouly with glutathione also produce peroxide. Glutathione plays an important role in the metabolism of the nitrocompounds either by directly reacting with them or their reduced intermediates such as the nitroso, nitro and hydroxyl radical. In the case of misonidazole, protection against their cytotoxic effects can be achieved by the addition of exogenous thiols such as glutathione or cysteamine. Results indicate that oxygen and peroxide electrodes provide convenient means for measuring the products of metabolic activation of nitro compounds. Mechanisms are proposed whereby protein, nonprotein and glutathione thiols can interact with drug radicals or with DNA radicals. 60 references, 14 figures, 5 tables

  15. Quantifying the global cellular thiol-disulfide status

    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...

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

    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.

  17. Reversible inactivation of CO dehydrogenase with thiol compounds

    Highlights: • Rather large thiols (e.g. coenzyme A) can reach the active site of CO dehydrogenase. • CO- and H2-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 + H2O → CO2 + 2e− + 2H+) which proceeds at a unique [CuSMo(=O)OH] metal cluster. Because of changing activities of CO dehydrogenase, particularly in subcellular fractions, we speculated whether the enzyme would be subject to regulation by thiols (RSH). Here we establish inhibition of CO dehydrogenase by thiols and report the corresponding Ki-values (mM): L-cysteine (5.2), D-cysteine (9.7), N-acetyl-L-cysteine (8.2), D,L-homocysteine (25.8), L-cysteine–glycine (2.0), dithiothreitol (4.1), coenzyme A (8.3), and 2-mercaptoethanol (9.3). Inhibition of the enzyme was reversed by CO or upon lowering the thiol concentration. Electron paramagnetic resonance spectroscopy (EPR) and X-ray absorption spectroscopy (XAS) of thiol-inhibited CO dehydrogenase revealed a bimetallic site in which the RSH coordinates to the Cu-ion as a third ligand ([MoVI(=O)OH(2)SCuI(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

  18. Reversible inactivation of CO dehydrogenase with thiol compounds

    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.

  19. Synthetic Applications of Intramolecular Thiol-Ene Click Reactions

    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.

  20. Oxidative Thiol Modifications in Pro- and Eukaryotic Organisms

    Brandes, Nicolas

    2010-01-01

    Cystein spielt eine wichtige Rolle in der Biochemie vieler Proteine. Aufgrund der Redox-Eigenschaften und der hohen Reaktivität der freien Thiol-Gruppe sowie dessen Fähigkeit Metallionen zu koordinieren, ist Cystein oft Bestandteil von katalytischen Zentren vieler Enzyme. Zudem lassen sich Cysteine durch reaktive Sauerstoff- und Stickstoffspezies leicht reversibel oxidativ modifizieren. In den letzten Jahren wurde gezeigt, dass Proteine redox-bedingte Thiol-Modifikationen nutzen, um Veränderu...

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

    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...

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

    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. Protein Thiols as an Indication of Oxidative Stress

    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

  4. Short communication: characterization of soluble thiols in bovine milk.

    Niero, G; De Marchi, M; Masi, A; Penasa, M; Cassandro, M

    2015-09-01

    Antioxidants are molecules essential for the maintenance of cell homeostasis and their intake through the diet has positive effects on human health. Among antioxidants, low-molecular-weight (LMW) thiols represent an important class of compounds. The aim of this study was to identify LMW thiols in bovine milk. A total of 96 individual milk samples from Brown Swiss, Holstein-Friesian, Alpine Grey, and Simmental cattle breeds were collected in 8 herds. The LMW thiols were extracted from the soluble fraction of milk and, following a derivatization protocol, they were separated by reverse phase HPLC and detected fluorimetrically. Six thiol species were detected and 2, glutathione (GSH) and cysteine-glycine (Cys-Gly), were identified and quantified. Regardless of the breed, the average concentration of Cys-Gly in milk was greater than that of GSH. Overall, milk from dual-purpose breeds (Simmental and Alpine Grey) was richer in LMW thiols than milk from dairy cows (Holstein-Friesian and Brown Swiss). Glutathione and Cys-Gly, closely linked metabolically, were strongly correlated. Pearson correlations of Cys-Gly with protein and casein contents were moderately low, and no relationship was found between GSH and milk chemical composition. Future research should focus on the identification of all detected LMW thiol species. PMID:26188581

  5. Redox Initiation of Bulk Thiol-Ene Polymerizations

    Cole, Megan A.; Jankousky, Katherine C.; Bowman, Christopher N.

    2013-01-01

    The unique formation-structure-property attributes and reaction behavior of the thiol-ene “click” reaction have been explored extensively for photochemically and thermally initiated reactions but have been much less explored for redox initiation. Therefore, the objective of this work is to characterize fully the impact of the initiation system, monomer structure, degree of functionalization, and inhibitor level on the redox-mediated thiol-ene polymerization rate and behavior. Moreover, this study confirms the ability of redox initiation to achieve full conversion of desired thiol-ene “click” products for small molecules in solution. For the multifunctional thiol-ene systems, polymerization rate was shown to be comparable to photo- and thermally initiated systems, but with the additional advantages of unlimited depth of cure and mild reaction conditions. Additionally, the network properties of the redox-initiated thiol-ene systems were on par with a photocured material formulated with identical monomers and radical initiating potential. Lastly, control over the polymerization rate and preceding induction period was garnered from the concentration of inhibitor included in the reaction mixture. The mechanism of action of quinone inhibition in redox-mediated thiol-ene polymerizations is shown to depend on both the presence of an aniline reducing agent and the concentration of inhibitor, with quinone concentrations in great excess of oxidizing agent concentrations actually leading to heightened polymerization rates when aniline is present. PMID:23565125

  6. Polymer surface engineering via thiol-mediated reactions

    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.

  7. Roles of thioredoxin and thioredoxin reductase in the resistance to oxidative stress in Lactobacillus casei.

    Serata, Masaki; Iino, Tohru; Yasuda, Emi; Sako, Tomoyuki

    2012-04-01

    The Lactobacillus casei strain Shirota used in this study has in the genome four putative thioredoxin genes designated trxA1, trxA2, trxA3 and trxA4, and one putative thioredoxin reductase gene designated trxB. To elucidate the roles of the thioredoxins and the thioredoxin reductase against oxidative stress in L. casei, we constructed gene disruption mutants, in which each of the genes trxA1, trxA2 and trxB, or both trxA1 and trxA2 were disrupted, and we characterized their growth and response to oxidative stresses. In aerobic conditions, the trxA1 (MS108) and the trxA2 (MS109) mutants had moderate growth defects, and the trxA1 trxA2 double mutant (MS110) had a severe growth defect, which was characterized by elongation of doubling time and a lower final turbidity level. Furthermore, the trxB mutant (MS111), which is defective in thioredoxin reductase, lost the ability to grow under aerobic conditions, although it grew partially under anaerobic conditions. The growth of these mutants, however, could be substantially restored by the addition of dithiothreitol or reduced glutathione. In addition, MS110 and MS111 were more sensitive to hydrogen peroxide and disulfide stress than the wild-type. In particular, the stress sensitivity of MS111 was significantly increased. On the other hand, transcription of all these genes was only weakly affected by these oxidative stresses. Taken together, these results suggest that the thioredoxin-thioredoxin reductase system is the major thiol/disulfide redox system and is essential to allow the facultative anaerobe L. casei to grow under aerobic conditions. PMID:22301908

  8. alpha-Lipoic acid modulates thiol antioxidant defenses and attenuates exercise-induced oxidative stress in standardbred trotters.

    Kinnunen, Susanna; Oksala, Niku; Hyyppä, Seppo; Sen, Chandan K; Radak, Zsolt; Laaksonen, David E; Szabó, Bernadett; Jakus, Judit; Atalay, Mustafa

    2009-08-01

    Several micronutrient supplementation strategies are used to cope with oxidative stress, although their benefits have recently been questioned. The aim of the present study was to examine the effects of DL-alpha-lipoic acid (LA) in response to acute exercise and during recovery in horses. Six standardbred trotters were tested on the treadmill before and after 5-week LA supplementation (25 mg/kg body weight/day). According to electron paramagnetic resonance measurements, strenuous aerobic exercise increased significantly free radical formation in the gluteus medius muscle, which was prevented by LA supplementation. The activities of thioredoxin reductase and glutathione reductase in muscle were significantly increased in LA-treated horses, but neither LA nor exercise affected muscle thioredoxin activity. LA increased the concentration of total glutathione in muscle at rest and during recovery. Treatment with LA blunted the exercise-induced increase in plasma oxygen radical absorbance capacity and decreased the post-exercise levels of lipid hydroperoxides in plasma and malondialdehyde in plasma and in muscle. These findings suggest that LA enhances thiol antioxidant defences and decreases exercise-induced oxidative stress in skeletal muscle. PMID:19548154

  9. Protection by thiols against poisoning by radiomimetic agents. Chapter 8

    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.)

  10. The impact of thiol peroxidases on redox regulation.

    Flohé, Leopold

    2016-01-01

    The biology of glutathione peroxidases and peroxiredoxins is reviewed with emphasis on their role in metabolic regulation. Apart from their obvious function in balancing oxidative challenge, these thiol peroxidases are not only implicated in orchestrating the adaptive response to oxidative stress, but also in regulating signaling triggered by hormones, growth factors and cytokines. The mechanisms presently discussed comprise dampening of redox-sensitive regulatory processes by elimination of hydroperoxides, suppression of lipoxygenase activity, committing suicide to save H2O2 for signaling, direct binding to receptors or regulatory proteins in a peroxidase activity-independent manner, or acting as sensors for hydroperoxides and as transducers of oxidant signals. The various mechanistic proposals are discussed in the light of kinetic data, which unfortunately are scarce. Taking into account pivotal criteria of a meaningful regulatory circuit, kinetic plausibility and specificity, the mechanistic concepts implying a direct sensor/transducer function of the thiol peroxidases appear most appealing. With rate constants for the reaction with hydroperoxide of 10(5)-10(8) M(-1) s(-1), thiol peroxidases are qualified as kinetically preferred hydroperoxide sensors, and the ability of the oxidized enzymes to react with defined protein thiols lends specificity to the transduction process. The versatility of thiol peroxidases, however, allows multiple ways of interaction with regulatory pathways. PMID:26291534

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

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

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

    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

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

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

  14. Identification of thiols by means of mercurated fluorescein.

    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

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

    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 α- and β-subunits of microbial nitrate reductase, selenate reductase, dimethyl sulfide dehydrogenase, ethylbenzene dehydrogenase, and chlorate reductase, all of which are type II m...

  16. 5-Furan-2yl[1,3,4]oxadiazole-2-thiol, 5-Furan-2yl-4H [1,2,4] triazole-3-thiol and Their Thiol-Thione Tautomerism

    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.

  17. Multiple aldehyde reductases of human brain.

    Hoffman, P L; Wermuth, B; von Wartburg, J P

    1980-01-01

    Human brain contains four forms of aldehyde reducing enzymes. One major activity, designated AR3, has properties indicating its identity with the NADPH-dependent aldehyde reductase, EC 1.1.1.2. The other major form of human brain enzyme, AR1, which is also NADPH-dependent, reduces both aldehyde and ketone-containing substrates, including vitamin K3 (menadione) and daunorubicin, a cancer chemotherapeutic agent. This enzyme is very sensitive to inhibition by the flavonoids quercitrin and quercetine, and may be analogous to a daunorubicin reductase previously described in liver of other species. One minor form of human brain aldehyde reductase, AR2, demonstrates substrate specificity and inhibitor sensitivity which suggest its similarity to aldose reductases found in lens and other tissues of many species. This enzyme, which can also use NADH as cofactor to some extent, is the most active in reducing the aldehyde derivatives of the biogenic amines. The fourth human brain enzyme ("SSA reductase") differs from the other forms in its ability to use NADH as well as or better than NADPH as cofactor, and in its molecular weight, which is nearly twice that of the other forms. It is quite specific for succinic semialdehyde (SSA) as substrate, and was found to be significantly inhibited only by quercetine and quercitrin. AR3 can also reduce SSA, and both enzymes may contribute to the production of gamma-hydroxybutyric acid in vivo. These results indicate that the human brain aldehyde reductases can play relatively specific physiologic roles. PMID:7424738

  18. Quantification of protein-derived thiols during atmosphere-controlled brewing in laboratory scale

    Murmann, Anne Nordmark; Andersen, Preben; Mauch, Alexander; Lund, Marianne Nissen

    2016-01-01

    An atmosphere-controlled brewing system was built to study thiol oxidation during brewing in laboratory scale under conditions with limited oxygen exposure. Quantification of free and total thiols and protein showed that thiols were lost during wort boiling possibly owing to protein precipitation...

  19. Naphthalimide Scaffold Provides Versatile Platform for Selective Thiol Sensing and Protein Labeling.

    Zhou, Pengcheng; Yao, Juan; Hu, Guodong; Fang, Jianguo

    2016-04-15

    Reversible thiol modifications are fundamental of cellular redox regulation. Specific thiol detection, including thiol sensing and protein thiols labeling, is critical to study such modifications. We reported the discovery of 4-methylsulfonyl-N-n-butyl-1,8-naphthalimide (MSBN), a highly selective fluorogenic probe for thiols based on the 1,8-naphthalimide scaffold. Thiols react with MSBN nearly quantitatively via nucleophilic aromatic substitution to replace the methylsulfonyl group and restore the quenched fluorescence (>100-fold increase). MSBN was employed to selectively image thiols in live cells and specifically label protein thiols with a turn-on signal to determine diverse reversible protein thiol modifications. In addition, we introduced a bulky group into the MSBN as a mass tag to create a probe MSBN-TPP, which readily discriminates the reduced thioredoxin from the oxidized one. The specific reaction of MSBN with thiols and the easy manipulation of the naphthalimide unit enable MSBN a versatile scaffold in developing novel probes for thiol-based protein bioconjugation and studying various thiol modifications. PMID:26813105

  20. Thioredoxin-related Protein 32 Is an Arsenite-regulated Thiol Reductase of the Proteasome 19 S Particle*S⃞

    Wiseman, R Luke; Chin, King-Tung; Haynes, Cole M.; Stanhill, Ariel; Xu, Chong-Feng; Roguev, Assen; Krogan, Nevan J.; Neubert, Thomas A.; Ron, David

    2009-01-01

    Perturbation of the cytoplasmic protein folding environment by exposure to oxidative stress-inducing As(III)-containing compounds challenges the ubiquitin-proteasome system. Here we report on mass spectrometric analysis of As(III)-induced changes in the proteasome's composition in samples prepared by stable isotope labeling with amino acids in cell culture, using mammalian cells in which TRP32 (thioredoxin-related protein of 32 kDa; also referred to as TXNL1) was ident...

  1. Preparation of Novel Hydrolyzing Urethane Modified Thiol-Ene Networks

    Bridget S. Confait

    2011-10-01

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

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

    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

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

    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. Arsenate reduction: thiol cascade chemistry with convergent evolution.

    Messens, Joris; Silver, Simon

    2006-09-01

    The frequent abundance of arsenic in the environment has guided the evolution of enzymes for the reduction of arsenate. The arsenate reductases (ArsC) from different sources have unrelated sequences and structural folds, and can be divided into different classes on the basis of their structures, reduction mechanisms and the locations of catalytic cysteine residues. The thioredoxin-coupled arsenate reductase class is represented by Staphylococcus aureus pI258 ArsC and Bacillus subtilis ArsC. The ArsC from Escherichia coli plasmid R773 and the eukaryotic ACR2p reductase from Saccharomyces cerevisiae represent two distinct glutaredoxin-linked ArsC classes. All are small cytoplasmic redox enzymes that reduce arsenate to arsenite by the sequential involvement of three different thiolate nucleophiles that function as a redox cascade. In contrast, the ArrAB complex is a bacterial heterodimeric periplasmic or a surface-anchored arsenate reductase that functions as a terminal electron acceptor and transfers electrons from the membrane respiratory chain to arsenate. Finally, the less well documented arsenate reductase activity of the monomeric arsenic(III) methylase, which is an S-adenosylmethionine (AdoMet)-dependent methyltransferase. After each oxidative methylation cycle and before the next methylation step, As(V) is reduced to As(III). Methylation by this enzyme is also considered an arsenic-resistance mechanism for bacteria, fungi and mammals. PMID:16905151

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

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

    2011-06-28

    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 rapidly initiates the polymerization. Heat transfer profiles and reaction kinetics of the samples are modeled during the reactions with varying induction heater power, species concentration, species type and sample thickness, and the model is compared with the experimental results. Thiol-ene polymerizations achieved full conversion between 1.5 minutes and 1 hour, depending on the field intensity and the composition, with the maximum reaction temperature decreasing from 146 - 87 °C when the induction heater power was decreased from 8 - 3 kW. The polymerization reactions of the thiol-acrylate system were demonstrated to achieve full conversion between 0.6 and 30 minutes with maximum temperatures from 139 to 86 °C. The experimental behavior was characterized and the temperature profile modeled for the thiol-acrylate composite comprised of sub100nm nickel particles and induction heater power in the range of 32 to 20 kW. A 9°C average deviation was observed between the modeling and experimental results for the maximum temperature rise. The model also was utilized to predict reaction temperatures and kinetics for systems with varying thermal initiator concentration, initiator half-life, monomer molecular weight and temperature gradients in samples with varying thickness, thereby demonstrating that induction curing represents a designable and tunable polymerization method. Finally, induction curing was utilized to cure thiol-acrylate systems containing carbon nanotubes where 1 wt% carbon nanotubes resulted in systems where the storage modulus increased from 17.6 ± 0.2 to 21.6 ± 0.1 MPa and an electrical conductivity that increased from <10(-7) to 0.33 ± 0.5 S/m. PMID:21765552

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

    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...

  7. Respiratory arsenate reductase as a bidirectional enzyme

    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. Respiratory arsenate reductase as a bidirectional enzyme

    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.

  9. Respiratory arsenate reductase as a bidirectional enzyme

    Richey, Christine [Department of Biological Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, PA 15282 (United States); Chovanec, Peter [Department of Biological Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, PA 15282 (United States); Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA 15282 (United States); Hoeft, Shelley E.; Oremland, Ronald S. [U.S. Geological Survey, 345 Middlefield Rd., MS 480, Menlo Park, CA 94025 (United States); Basu, Partha [Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA 15282 (United States); Stolz, John F., E-mail: stolz@duq.edu [Department of Biological Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, PA 15282 (United States)

    2009-05-01

    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.

  10. Water electrolyte promoted oxidation of functional thiol groups.

    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

  11. Radical Scavenging Efficacy of Thiol Capped Silver Nanoparticles

    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.

  12. Thiol-ene/methacrylate systems for mechanical damping

    McNair, Olivia; Senyurt, Askim; Wei, Huanyu; Gould, Trent; Piland, Scott; Hoyle, Charles; Savin, Daniel

    2010-03-01

    Ternary thiol-ene-methacrylate (TEMA) networks as materials for mechanical energy damping are unique to the sports world. Using a photoinitiation process, TEMA systems are formed via an initial thiol-ene step-growth mechanism along with traditional radical polymerization of acrylate and ene monomers. Final networks have two-part morphologies: acrylate homopolymer sectors imbedded in a multi-component mesh. Several (TEMA) systems have been synthesized and analyzed via thermal and mechanical probing. Initial studies on these ternary systems have shown excellent properties compared to traditional ethylene vinyl alcohol (EVA) copolymers. For example, PEMA networks exhibit glass transition temperatures 33 K higher than EVA, resulting in improved damping at room temperature. This research will help develop relationships between tan delta, glass transition and their effects on mechanical energy damping for ternary (TEMA) systems.

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

    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. Water electrolyte promoted oxidation of functional thiol groups

    Lauwers, Karl; Breynaert, Eric; Rombouts, Ine; Delcour, Jan; Kirschhock, Christine

    2016-01-01

    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...

  15. Thiol-functionalized anthraquinones: mass spectrometry and electrochemical studies

    Niedziałkowski, Paweł; Ossowski, Tadeusz; Majewski, Radosław; Nowakowska, Zdzisława; Schroeder, Grzegorz

    2011-01-01

    Abstract In this work, the synthesis of various thiol-functionalized anthraquinone compounds is presented. The studied compounds were characterized by mass spectrometry and the main fragmentation pathways are discussed. The compounds studied formed stable self-assembled monolayers (SAMs) in the gold surface. The parameters for the reduction processes in the gold surface of the studied new anthraquinones were determined by cyclic voltamperometry tests. Graphical abstract

  16. Functional Conducting Polymers via Thiol-ene Chemistry

    Martin, David C.; Kathleen E. Feldman

    2012-01-01

    We demonstrate here that thiol-ene chemistry can be used to provide side-chain functionalized monomers based on 3,4-propylenedioxythiophene (ProDOT) containing ionic, neutral, hydrophobic, and hydrophilic side chains. All reactions gave high yields and purification could generally be accomplished through precipitation. These monomers were polymerized either chemically or electro-chemically to give soluble materials or conductive films, respectively. This strategy provides for facile tuning of...

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

    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

  18. Domain Motion in Cytochrome P450 Reductase

    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 ...

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

    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.

  20. Organized thiol functional groups in mesoporous core shell colloids

    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.

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

    Mommer, Stefan; Keul, Helmut; Mller, 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. Analytical detection of biological thiols in a microchip capillary channel.

    Chand, Rohit; Jha, Sandeep Kumar; Islam, Kamrul; Han, Dawoon; Shin, Ik-Soo; Kim, Yong-Sang

    2013-02-15

    Sulfur-containing amino acids, such as cysteine and homocysteine play crucial roles in biological systems for the diagnosis of medical states. In this regard, this paper deals with separation, aliquot and detection of amino thiols on a microchip capillary electrophoresis with electrochemical detection in an inverted double Y-shaped microchannel. Unlike the conventional capillary electrophoresis, the modified microchannel design helps in storing the separated thiols in different reservoirs for further analysis, if required; and also eliminates the need of electrodes regeneration. The device was fabricated using conventional photolithographic technique which consisted of gold microelectrodes on a soda lime glass wafer and microchannels in PDMS mold. Multiple detections were performed using in-house fabricated dual potentiostat. Based on amperometric detection, cysteine and homocysteine were analyzed in 105 s and 120 s, respectively after diverting in branched channels. Repeated experiments proved the good reproducibility of the device. The device produced a linear response for both cysteine and homocysteine in electrochemical analysis. To prove the practicality of device, we also analyzed cysteine and homocysteine in real blood samples without any pre-treatment. Upon calculation, the device showed a very low limit of detection of 0.05 μM. The modified microchip design shall find a broad range of analytical applications involving assays of thiols and other biological compounds. PMID:22940195

  3. Thermal and Mechanical Properties of Sequential and Simultaneous Thiol-Ene-Isocyanate Networks

    McNair, Olivia; Brent, Davis; Savin, Daniel

    2011-03-01

    Ternary networks containing having stoichiometrically balanced thiol /(ene+isocyanate) ranging from 0 to 20 mol% isocyanate were synthesized via sequential or simultaneous thiol/ene and thiol/isocyanate click reactions. The effects of cross-link density were studied using three thiols, GDMP (difunctional), 3T (trifunctional) and 4T (tetrafunctional) respectively. TEA catalyzes the isocyanate-thiol coupling and chain extension, while the photoinitiator DMPA initiates a radical thiol-ene crosslinking process. Real-time FTIR was used to study kinetics of both light and dark reactions utilizing thiol, ene and isocyanate peaks which appear independently. It was found that difunctional thiols and isocyanates reacted initially, forming chain extended prepolymers end-capped with thiol functionalities. Upon UV irradiation, thiol functionalized prepolymers reacted with TTT, a trifunctional ene, forming networks containing incorporated thiourethane linkages. Initial DSC results indicated higher Tgs for higher cross-linked networks; however, isocyanate content has significant effects on each system. Films were also be thermally characterized via DMA and mechanical properties measured using MTS.

  4. Estimation of reactive thiol concentrations in dissolved organic matter and bacterial cell membranes in aquatic systems.

    Joe-Wong, Claresta; Shoenfelt, Elizabeth; Hauser, Emily J; Crompton, Nyssa; Myneni, Satish C B

    2012-09-18

    Organic thiols are highly reactive ligands and play an important role in the speciation of several metals and organic pollutants in the environment. Although small thiols can be isolated and their concentrations can be estimated using chromatographic and derivatization techniques, estimating concentrations of thiols associated with biomacromolecules and humic substances has been difficult. Here we present a fluorescence-spectroscopy-based method for estimating thiol concentrations in biomacromolecules and cell membranes using one of the soluble bromobimanes, monobromo(trimethylammonio)bimane (qBBr). The fluorescence of this molecule increases significantly when it binds to a thiol. The change in the sample fluorescence due to thiols reacting with qBBr is used to determine thiol concentration in a sample. Using this method, small thiols such as cysteine and glutathione can be detected in clean solutions down to ~50 nM without their separation and prior concentration. Thiols associated with dissolved organic matter (DOM) can be detected down to low micromolar concentration, depending on the DOM background fluorescence. The charge on qBBr prevents its rapid diffusion across cell membranes, so qBBr is ideal for estimating thiol concentration at the cell membrane-water interface. This method was successfully used to determine the thiol concentration on the cell envelope of intact Bacillus subtilis to nanomolar concentration without any special sample preparation. Among the chemical species tested for potential interferences (other reduced sulfides methionine and cystine, carboxylate, salt (MgCl(2))), carboxylates significantly influenced the absolute fluorescence signal of the thiol-qBBr complex. However, this does not affect the detection of thiols in heterogeneous mixtures using the presented method. PMID:22916681

  5. 21 CFR 864.7375 - Glutathione reductase assay.

    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,...

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

    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

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

    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.

  8. Operation of trans-thylakoid thiol-metabolizing pathways in photosynthesis

    Karamoko, Mohamed; Gabilly, Stéphane T.; Hamel, Patrice P.

    2013-01-01

    Thiol oxidation to disulfides and the reverse reaction, i.e., disulfide reduction to free thiols, are under the control of catalysts in vivo. Enzymatically assisted thiol-disulfide chemistry is required for the biogenesis of all energy-transducing membrane systems. However, until recently, this had only been demonstrated for the bacterial plasma membrane. Long considered to be vacant, the thylakoid lumen has now moved to the forefront of photosynthesis research with the realization that its p...

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

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

    1994-12-31

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

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

    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

  11. Determination of acidity and nucleophilicity in thiols by reaction with monobromobimane and fluorescence detection.

    Sardi, Florencia; Manta, Bruno; Portillo-Ledesma, Stephanie; Knoops, Bernard; Comini, Marcelo A; Ferrer-Sueta, Gerardo

    2013-01-01

    A method based on the differential reactivity of thiol and thiolate with monobromobimane (mBBr) has been developed to measure nucleophilicity and acidity of protein and low-molecular-weight thiols. Nucleophilicity of the thiolate is measured as the pH-independent second-order rate constant of its reaction with mBBr. The ionization constants of the thiols are obtained through the pH dependence of either second-order rate constant or initial rate of reaction. For readily available thiols, the a...

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

    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.

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

    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

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

    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 α-mercapto-ω-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

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

    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 14, 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.

  16. 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.

    Niebel, Claude; Calard, Franois; Jarrosson, Thibaut; Lre-Porte, Jean-Pierre; Breton, Tony; Serein-Spirau, Franoise

    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

  17. Functional Conducting Polymers via Thiol-ene Chemistry

    David C. Martin

    2012-08-01

    Full Text Available We demonstrate here that thiol-ene chemistry can be used to provide side-chain functionalized monomers based on 3,4-propylenedioxythiophene (ProDOT containing ionic, neutral, hydrophobic, and hydrophilic side chains. All reactions gave high yields and purification could generally be accomplished through precipitation. These monomers were polymerized either chemically or electro-chemically to give soluble materials or conductive films, respectively. This strategy provides for facile tuning of the solubility, film surface chemistry, and film morphology of this class of conducting polymers.

  18. Polysulfides Link H2S to Protein Thiol Oxidation

    Greiner, Romy; Pálinkás, Zoltán; Bäsell, Katrin; Becher, Dörte; Antelmann, Haike; Nagy, Péter; Dick, Tobias P.

    2013-01-01

    Aims: Hydrogen sulfide (H2S) is suggested to act as a gaseous signaling molecule in a variety of physiological processes. Its molecular mechanism of action was proposed to involve protein S-sulfhydration, that is, conversion of cysteinyl thiolates (Cys-S−) to persulfides (Cys-S-S−). A central and unresolved question is how H2S—that is, a molecule with sulfur in its lowest possible oxidation state (−2)—can lead to oxidative thiol modifications. Results: Using the lipid phosphatase PTEN as a mo...

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

    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.

  20. Aldose reductase inhibition suppresses airway inflammation

    Yadav, Umesh C. S.; Ramana, Kota V.; Srivastava, Satish K

    2011-01-01

    Airway inflammation induced by reactive oxygen species-mediated activation of redox-sensitive transcription factors is the hallmark of asthma, a prevalent chronic respiratory disease. In various cellular and animal models, we have recently demonstrated that, in response to multiple stimuli, aldose reductase (AKR1B1) regulates the inflammatory signals via NF-kappa B activation. Since NF-κB activation is implicated in asthma pathogenesis, we investigated whether AKR1B1 inhibition could prevent ...

  1. Ribonucleotide reductases: essential enzymes for bacterial life

    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...

  2. Active sites of thioredoxin reductases: Why selenoproteins?

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

  3. Biliverdin reductase: A major physiologic cytoprotectant

    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...

  4. Lithium BINOL Phosphate Catalyzed Desymmetrization of meso-Epoxides with Aromatic Thiols

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

    2014-01-01

    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 β-hydroxyl sulfides are obtained in excellent yield and enantioselectivity.

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

    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

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

    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

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

    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

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

    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...

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

    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...

  10. Mechanism-based inhibition of a mutant Escherichia coli ribonucleotide reductase (cysteine-225 → serine) by its substrate CDP

    The B1 subunit of Escherichia coli ribonucleotide reductase has been overexpressed using the pT7-5/pGP1-2 system developed by Tabor and Richardson. This method has allowed the preparation of two mutant B1 subunits in which two of the four thiols postulated to be within the active site of the enzyme, Cys-225 and Cys-759, have been changed to serines. Incubation of the [Ser225]B1 mutant with the B2 subunit, [U-14C]CDP, and the allosteric effector ATP results in production of cytosine, destruction of the tyrosyl radical in B2, radiolabeling of the protein, and cleavage of the B1 subunit into two pieces of 26 and 61.5 kDa. This process is independent of the identity of reductant. The [Ser759]B1 mutant reduces CDP in the presence of thioredoxin/thioredoxin reductase at 7.7% the rate of wild-type B1. When dithiothreitol is utilized as reductant, however, the rate of CDP reduction with [Ser759]B1 is identical to that observed with wild type

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

    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.

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

    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

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

    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

  15. Characterization of the chlorate reductase from Pseudomonas chloritidismutans

    Wolterink, A.F.W.M.; Schiltz, E; Hagedoorn, P.L.; Hagen, W.R.; Kengen, S.W.M.; Stams, A.J.M.

    2003-01-01

    A chlorate reductase has been purified from the chlorate-reducing strain Pseudomonas chloritidismutans. Comparison with the periplasmic (per)chlorate reductase of strain GR-1 showed that the cytoplasmic chlorate reductase of P. chloritidismutans reduced only chlorate and bromate. Differences were also found in N-terminal sequences, molecular weight, and subunit composition. Metal analysis and electron paramagnetic resonance measurements showed the presence of iron and molybdenum, which are al...

  16. Characterization of the Chlorate Reductase from Pseudomonas chloritidismutans

    2003-01-01

    A chlorate reductase has been purified from the chlorate-reducing strain Pseudomonas chloritidismutans. Comparison with the periplasmic (per)chlorate reductase of strain GR-1 showed that the cytoplasmic chlorate reductase of P. chloritidismutans reduced only chlorate and bromate. Differences were also found in N-terminal sequences, molecular weight, and subunit composition. Metal analysis and electron paramagnetic resonance measurements showed the presence of iron and molybdenum, which are al...

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

    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...

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

    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

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

    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...

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

    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.

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

    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.

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

    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

  3. Mercury Binding Sites in Thiol-Functionalized Mesostructured Silica

    Thiol-functionalized mesostructured silica with anhydrous compositions of (SiO2)1-x(LSiO1.5)x, where L is a mercaptopropyl group and x is the fraction of functionalized framework silicon centers, are effective trapping agents for the removal of mercuric(II) ions from water. In the present work, we investigate the mercury-binding mechanism for representative thiol-functionalized mesostructures by atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data and by Raman spectroscopy. The mesostructures with wormhole framework structures and compositions corresponding to x = 0.30 and 0.50 were prepared by direct assembly methods in the presence of a structure-directing amine porogen. PDF analyses of five mercury-loaded compositions with Hg/S ratios of 0.50-1.30 provided evidence for the bridging of thiolate sulfur atoms to two metal ion centers and the formation of chain structures on the pore surfaces. We find no evidence for Hg-O bonds and can rule out oxygen coordination of the mercury at greater than the 10% level. The relative intensities of the PDF peaks corresponding to Hg-S and Hg-Hg atomic pairs indicate that the mercury centers cluster on the functionalized surfaces by virtue of thiolate bridging, regardless of the overall mercury loading. However, the Raman results indicate that the complexation of mercury centers by thiolate depends on the mercury loading. At low mercury loadings (Hg/S (le) 0.5), the dominant species is an electrically neutral complex in which mercury most likely is tetrahedrally coordinated to bridging thiolate ligands, as in Hg(SBut)2. At higher loadings (Hg/S 1.0-1.3), mercury complex cations predominate, as evidenced by the presence of charge-balancing anions (nitrate) on the surface. This cationic form of bound mercury is assigned a linear coordination to two bridging thiolate ligands.

  4. Structure and mechanism of dimethylsulfoxide reductase, a molybdopterin-containing enzyme of DMSO reductase family

    Full text: Apart from nitrogenase, enzymes containing molybdenum are members of a superfamily, the molybdopterin-containing enzymes. Most of these enzymes catalyse an oxygen atom transfer and two electron transfer reaction. During catalysis the Mo at the active site cycles between the Mo(VI) and Mo(IV) states. The DMSO reductase family of molybdopterin-containing enzymes all contain a bis(molybdopterin guanine dinucleotide)Mo cofactor and over thirty examples have now been described. Over the last five years crystal structures of dimethylsulfoxide (DMSO) reductase and four other enzymes of the DMSO reductase family have revealed that enzymes of this family have a similar tertiary structure. The Mo atom at the active site is coordinated by four thiolate ligands provided by the dithiolene side chains of the two MGD molecules of the bis(MGD)Mo cofactor as well as a ligand provided by an amino acid side chain. In addition, an oxygen atom in the form of an oxo, hydroxo or aqua group is also coordinated to the Mo atom. In the case of dimethylsulfoxide reductase X-ray crystallography of the product-reduced species and Raman spectroscopy has demonstrated that the enzyme contains a single exchangeable oxo group that is H-bonded to W116

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

    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

  6. Genetic identification of a respiratory arsenate reductase

    Saltikov, Chad W.; Newman, Dianne K.

    2003-01-01

    For more than a decade, it has been recognized that arsenate [H2AsO41-; As(V)] can be used by microorganisms as a terminal electron acceptor in anaerobic respiration. Given the toxicity of arsenic, the mechanistic basis of this process is intriguing, as is its evolutionary origin. Here we show that a two-gene cluster (arrAB; arsenate respiratory reduction) in the bacterium Shewanella sp. strain ANA-3 specifically confers respiratory As(V) reductase activity. Mutants with in-frame deletions of...

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

    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

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

    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.

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

    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

  10. Thiazolidine-Protected β-Thiol Asparagine: Applications in One-Pot Ligation-Desulfurization Chemistry.

    Sayers, Jessica; Thompson, Robert E; Perry, Kristen J; Malins, Lara R; Payne, Richard J

    2015-10-01

    The synthesis of a β-thiol asparagine derivative bearing a novel (2,4,6-trimethoxyphenyl)thiazolidine protecting group is described. The efficient incorporation of the amino acid into the N-termini of peptides is demonstrated as well as the utility of the β-thiol asparagine moiety for rapid ligation reactions with peptide thioesters. The streamlined synthesis of native peptide products could be accomplished using a one-pot radical desulfurization of the β-thiol auxiliary following the ligation event. The utility of the amino acid is highlighted in the efficient one-pot assembly of the HIV entry inhibitor enfuvirtide. PMID:26398220

  11. Der Thiol:Disulfid-Redox Metabolismus und der Blaulichtrezeptor Lmo0799 von Listeria monocytogenes

    Ondrusch, Nicolai

    2010-01-01

    Der Thiol-Redox-Metabolismus, der in allen lebenden Zellen zu finden ist, wirkt oxidativem Stress entgegen. Des Weiteren dient er auch der Aufrechterhaltung der intrazellulären Thiol:Disulfid-Balance, die wiederum für die Funktion vieler Proteine essentiell ist. Auch stellt er Reduktionsäquivalente für die Produktion von Desoxyribonucleotiden für die DNA-Synthese bereit und hilft oxidierte Proteine zu reparieren. Der Thiol:Disulfid-Redox-Metabolismus (TDRM) unterscheidet sich von anderen meta...

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

    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.

  13. Canopy and seasonal profiles of nitrate reductase in soybeans

    Harper, J.E.; Hageman, R.H.

    1972-01-01

    Nitrate reductase activity of soybeans (Glycine max L. Merr.) was evaluated in soil plots and outdoor hydroponic gravel culture systems throughout the growing season. Nitrate reductase profiles within the plant canopy were also established. Mean activity per gram fresh weight per hour of the entire plant canopy was highest in the seedling stage while total activity (activity per gram fresh weight per hour times the total leaf weight) reached a maximum when plants were in the full bloom to midpod fill stage. Nitrate reductase activity per gram fresh weight per hour was highest in the uppermost leaf just prior to full expansion and declined with leaf positions lower in the canopy. Total nitrate reductase activity per leaf was also highest in the uppermost fully expanded leaf during early growth stages. Maximum total activity shifted to leaf positions lower in the plant canopy with later growth stages. Nitrate reductase activity of soybeans grown in hydroponic systems was significantly higher than activity of adjacent soil grown plants at later growth stages, which suggested that under normal field conditions the potential for nitrate utilization may not be realized. Nitrate reductase activity per gram fresh weight per hour and nitrate content were positively correlated over the growing season with plants grown in either soil or solution culture. Computations based upon the nitrate reductase assay of plants grown in hydroponics indicated that from 1.7 to 1.8 grams N could have been supplied to the plant via the nitrate reductase process. 11 references, 9 figures, 3 tables.

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

    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.

  15. Characterization of two alkyl hydroperoxide reductase C homologs alkyl hydroperoxide reductase C_H1 and alkyl hydroperoxide reductase C_H2 in Bacillus subtilis

    Cha, Mee-Kyung; Bae, Yoo-Jeen; Kim, Kyu-Jeong; Park, Byung-Joon; Kim, Il-Han

    2015-01-01

    AIM: To identify alkyl hydroperoxide reductase subunit C (AhpC) homologs in Bacillus subtilis (B. subtilis) and to characterize their structural and biochemical properties. AhpC is responsible for the detoxification of reactive oxygen species in bacteria.

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

    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

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

    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.

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

    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.

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

    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.)

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

    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.

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

    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. Application of metal-modified silica gels as sorbents for alkane-thiols

    In order to elaborate high effective method of purification of industry wastes from alkane-thiols the sorption properties of silica gels modified by ions of heavy metals are studied. The optimal conditions of sorption are defined.

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

    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.

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

    Kov?ov, Jana; Svobodov, 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...

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

    Claudio Larosa; Enrico Stura; Roberto Eggenhöffner; Claudio Nicolini

    2009-01-01

    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...

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

    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

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

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

    2013-01-01

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

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

    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

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

    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

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

    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.

  11. HPLC determination of thiol-containing anti-browning additives in fruit and vegetable products

    Voldrich, M.; Dupont, D.; Dobias, J.; Philippon, J

    1995-01-01

    The HPLC determination of residual thiol-containing anti-browning additives (cysteine, N-accetyl-cysteine and reduced glutathione) in treated fruit and vegetable products using the Ellman's reagent is described. The thiols were isolated by extraction with solvent containing NaF, EDTA, acetic and ascorbic acids and derivatized with the Ellman's reagent in an aqueous medium at pH 8.0. The resulting disulphides were determined by reverse phase HPLC with mobile phase consisting of methanol and ph...

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

    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

  13. Proanthocyanidin synthesis in Theobroma cacao: genes encoding anthocyanidin synthase, anthocyanidin reductase, and leucoanthocyanidin reductase

    Liu, Yi; Shi, Zi; Maximova, Siela; Payne, Mark J.; Guiltinan, Mark J

    2013-01-01

    Background The proanthocyanidins (PAs), a subgroup of flavonoids, accumulate to levels of approximately 10% total dry weight of cacao seeds. PAs have been associated with human health benefits and also play important roles in pest and disease defense throughout the plant. Results To dissect the genetic basis of PA biosynthetic pathway in cacao (Theobroma cacao), we have isolated three genes encoding key PA synthesis enzymes, anthocyanidin synthase (ANS), anthocyanidin reductase (ANR) and leuc...

  14. Oligomerization of Indole Derivatives with Incorporation of Thiols

    Jarl E.S. Wikberg

    2008-08-01

    Full Text Available Abstract: Two molecules of indole derivative, e.g. indole-5-carboxylic acid, reacted with one molecule of thiol, e.g. 1,2-ethanedithiol, in the presence of trifluoroacetic acid to yield adducts such as 3-[2-(2-amino-5-carboxyphenyl-1-(2-mercaptoethylthioethyl]-1Hindole-5-carboxylic acid. Parallel formation of dimers, such as 2,3-dihydro-1H,1'H-2,3'-biindole-5,5'-dicarboxylic acid and trimers, such as 3,3'-[2-(2-amino-5-carboxyphenyl ethane-1,1-diyl]bis(1H-indole-5-carboxylic acid of the indole derivatives was also observed. Reaction of a mixture of indole and indole-5-carboxylic acid with 2-phenylethanethiol proceeded in a regioselective way, affording 3-[2-(2-aminophenyl-1-(phenethylthioethyl]-1H-indole-5-carboxylic acid. An additional product of this reaction was 3-[2-(2-aminophenyl-1-(phenethylthioethyl]-2,3-dihydro-1H,1'H-2,3'-biindole-5'-carboxylic acid, which upon standing in DMSO-d6 solution gave 3-[2-(2-aminophenyl-1-(phenethylthioethyl]-1H,1'H-2,3'-biindole-5'-carboxylic acid. Structures of all compounds were elucidated by NMR, and a mechanism for their formation was suggested.

  15. Submerged nanocontact printing (SnCP) of thiols.

    Caballero, David; Samitier, Josep; Errachid, Abdelhamid

    2009-11-01

    Biological patterned surfaces having sub-micron scale resolution are of great importance in many fields of life science and biomedicine. Different techniques have been proposed for surface patterning at the nanoscale. However, most of them present some limitations regarding the patterned area size or are time-consuming. Micro/nanocontact printing is the most representative soft lithography-based technique for surface patterning at the nanoscale. Unfortunately, conventional micro/nanocontact printing also suffers from problems such as diffusion and stamp collapsing that limit pattern resolution. To overcome these problems, a simple way of patterning thiols under liquid media using submerged nanocontact printing (SnCP) over large areas (approximately cm2) achieving nanosize resolution is presented. The technique is also low cost and any special equipment neither laboratory conditions are required. Nanostructured poly(dimethyl siloxane) stamps are replicated from commercially available digital video disks. SnCP is used to stamp patterns of 200 nm 1-octadecanethiol lines in liquid media, avoiding ink diffusion and stamp collapsing, over large areas on gold substrates compared with conventional procedures. Atomic force microscopy measurements reveal that the patterns have been successfully transferred with high fidelity. This is an easy, direct, effective and low cost methodology for molecule patterning immobilization which is of interest in those areas that require nanoscale structures over large areas, such as tissue engineering or biosensor applications. PMID:19908552

  16. Tunable thiol-epoxy shape memory polymer foams

    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.

  17. Human erythrocyte thiol methyltransferase: radiochemical microassay and biochemical properties

    A radiochemical microassay for the measurement of thiol methyltransferase (TMT) activity in human red blood cell (RBC) membranes has been developed. Both 2-mercaptoethanol and dithiothreitol were used as substrates for the enzyme. The pH optimum of the reaction was approximately 9.0 when glycine-NaOH was used as a buffer. The apparent Michaelis-Menten (Ksub(M)) value for the methyl donor for the reaction, S-adenosyl-L-methionine, was 43 μmol/l. Human RBC TMT activity was neither activated nor inhibited by Ca2+, Mg2+, or tropolone, but the enzyme was inhibited by SKF 525A and by reagents that react with sulfhydryl grcups. The mean TMT activity in blood from 289 randomly selected adult white subjects was 10.93 +- 3.22 units per mg protein (mean +- S.D.). The activity was the same in samples from men and women. The results of experiments in which TMT activity was measured in mixtures of RBC membranes with relatively ''low'' and relatively ''high'' activities provided no evidence that individual variations in the enzyme activity were due to variations in endogenous TMT activators or inhibitors. (Auth.)

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

    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.

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

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

    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

  20. Solution structure of an arsenate reductase-related protein, YffB, from Brucella melitensis, the etiological agent responsible for brucellosis

    B. melitensis is a NIAID Category B microorganism that is responsible for brucellosis and is a potential agent for biological warfare. Here, the solution structure of the 116-residue arsenate reductase-related protein Bm-YffB (BR0369) from this organism is reported. Brucella melitensis is the etiological agent responsible for brucellosis. Present in the B. melitensis genome is a 116-residue protein related to arsenate reductases (Bm-YffB; BR0369). Arsenate reductases (ArsC) convert arsenate ion (H2AsO4−), a compound that is toxic to bacteria, to arsenite ion (AsO2−), a product that may be efficiently exported out of the cell. Consequently, Bm-YffB is a potential drug target because if arsenate reduction is the protein’s major biological function then disabling the cell’s ability to reduce arsenate would make these cells more sensitive to the deleterious effects of arsenate. Size-exclusion chromatography and NMR spectroscopy indicate that Bm-YffB is a monomer in solution. The solution structure of Bm-YffB shows that the protein consists of two domains: a four-stranded mixed β-sheet flanked by two α-helices on one side and an α-helical bundle. The α/β domain is characteristic of the fold of thioredoxin-like proteins and the overall structure is generally similar to those of known arsenate reductases despite the marginal sequence similarity. Chemical shift perturbation studies with 15N-labeled Bm-YffB show that the protein binds reduced glutathione at a site adjacent to a region similar to the HX3CX3R catalytic sequence motif that is important for arsenic detoxification activity in the classical arsenate-reductase family of proteins. The latter observation supports the hypothesis that the ArsC-YffB family of proteins may function as glutathione-dependent thiol reductases. However, comparison of the structure of Bm-YffB with the structures of proteins from the classical ArsC family suggest that the mechanism and possibly the function of Bm-YffB and other related proteins (ArsC-YffB) may differ from those of the ArsC family of proteins

  1. Domain Motion in Cytochrome P450 Reductase

    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

  2. Nitrite Reductase Activity in Engineered Azurin Variants.

    Berry, Steven M; Strange, Jacob N; Bladholm, Erika L; Khatiwada, Balabhadra; Hedstrom, Christine G; Sauer, Alexandra M

    2016-05-01

    Nitrite reductase (NiR) activity was examined in a series of dicopper P.a. azurin variants in which a surface binding copper site was added through site-directed mutagenesis. Four variants were synthesized with copper binding motifs inspired by the catalytic type 2 copper binding sites found in the native noncoupled dinuclear copper enzymes nitrite reductase and peptidylglycine α-hydroxylating monooxygenase. The four azurin variants, denoted Az-NiR, Az-NiR3His, Az-PHM, and Az-PHM3His, maintained the azurin electron transfer copper center, with the second designed copper site located over 13 Å away and consisting of mutations Asn10His,Gln14Asp,Asn16His-azurin, Asn10His,Gln14His,Asn16His-azurin, Gln8Met,Gln14His,Asn16His-azurin, and Gln8His,Gln14His,Asn16His-azurin, respectively. UV-visible absorption spectroscopy, EPR spectroscopy, and electrochemistry of the sites demonstrate copper binding as well as interaction with small exogenous ligands. The nitrite reduction activity of the variants was determined, including the catalytic Michaelis-Menten parameters. The variants showed activity (0.34-0.59 min(-1)) that was slower than that of native NiRs but comparable to that of other model systems. There were small variations in activity of the four variants that correlated with the number of histidines in the added copper site. Catalysis was found to be reversible, with nitrite produced from NO. Reactions starting with reduced azurin variants demonstrated that electrons from both copper centers were used to reduce nitrite, although steady-state catalysis required the T2 copper center and did not require the T1 center. Finally, experiments separating rates of enzyme reduction from rates of reoxidation by nitrite demonstrated that the reaction with nitrite was rate limiting during catalysis. PMID:27055058

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

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

    2015-01-01

    . 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......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...

  4. Small-scale polymer structures enabled by thiol-ene copolymer systems

    Kasprzak, Scott Edward

    2009-12-01

    The research described herein is aimed at exploring the thermomechanical properties of thiol-ene polymers in bulk form, investigating the ability of thiol-ene polymers to behave desirably as photolithographic media, and providing the first characterization of the mechanical properties of two-photon stereolithography-produced polymer structures. The thiol-ene polymerization reaction itself is well-characterized and described in the literature, but the thermomechanical properties of thiol-ene and thiol-ene/acrylate polymers still require more rigorous study. Understanding the behavior of thiol-ene networks is a crucial step towards their expanded use in bulk form, and particularly in specialized applications such as shape memory devices. Additionally, the thiol-ene polymerization reaction mechanism exhibits unique properties which make these polymers well suited to photolithography, overcoming the typical dichotomy of current materials which either exhibit excellent photolithographic behavior or have controllable properties. Finally, before two-photon stereolithography can create mechanisms and devices which can serve any mechanically functional role, the mechanical properties of the polymers they produce must be quantitatively characterized, which is complicated by the extremely small scale at which these structures are produced. As such, mechanical characterization to date has been strictly qualitative. Fourier transfer infrared spectroscopy revealed functional group conversion information and sol-fraction testing revealed the presence of unconverted monomer and impurities, while dynamic mechanical analysis (DMA) and tensile testing revealed the thermomechanical responses of the systems. Nanoindentation was employed to characterize the mechanical properties of micrometer-scale polymer structures produced by two-photon stereolithography. Optical and electron microscopy were exploited to provide both quantitative and qualitative evaluations of thiol-ene/acrylate and acrylate performance in small-scale polymerization regimes. The broad objective of the research was to explore thiol-ene polymer behavior both in bulk and at the small scale in an effort to supplement the material library currently used in these fields and to expand the design envelope available to researchers. The significance of the research is the advancement of a more complete and fundamental understanding of thiol-ene polymerization from kinetics to final properties, the quantitative establishment of the mechanical properties of materials created with two-photon stereolithography, and the comprehensive characterization of a supplementary class of photopatternable polymers with greater property tunability than is possible with currently used materials.

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

    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

  6. Synthesis of alkenyl sulfides through the iron-catalyzed cross-coupling reaction of vinyl halides with thiols.

    Lin, Yun-Yung; Wang, Yu-Jen; Lin, Che-Hung; Cheng, Jun-Hao; Lee, Chin-Fa

    2012-07-20

    We report here the iron-catalyzed cross-coupling reaction of alkyl vinyl halides with thiols. While many works are devoted to the coupling of thiols with alkyl vinyl iodides, interestingly, the known S-vinylation of vinyl bromides and chlorides is limited to 1-(2-bromovinyl)benzene and 1-(2-chlorovinyl)benzene. Investigation on the coupling reaction of challenging alkyl vinyl bromides and chlorides with thiols is rare. Since the coupling of 1-(2-bromovinyl)benzene and 1-(2-chlorovinyl)benzene with thiols can be performed in the absence of any catalyst, here we focus on the coupling of thiols with alkyl vinyl halides. This system is generally reactive for alkyl vinyl iodides and bromides to provide the products in good yields. 1-(Chloromethylidene)-4-tert-butyl-cyclohexane was also coupled with thiols, giving the targets in moderate yields. PMID:22708836

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

    Thormhlen, Ina; Meitzel, Tobias; Groysman, Julia; chsner, Alexandra Bianca; von Roepenack-Lahaye, Edda; Naranjo, Beln; 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

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

    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. 5α-reductase activity in rat adipose tissue

    We measured the 5 α-reductase activity in isolated cell preparations of rat adipose tissue using the formation of [3H] dihydrotestosterone from [3H] testosterone as an endpoint. Stromal cells were prepared from the epididymal fat pad, perinephric fat, and subcutaneous fat of male rats and from perinephric fat of female rats. Adipocytes were prepared from the epididymal fat pad and perinephric fat of male rats. Stromal cells from the epididymal fat pad and perinephric fat contained greater 5α-reductase activity than did the adipocytes from these depots. Stromal cells from the epididymal fat pad contained greater activity than those from perinephric and subcutaneous depots. Perinephric stromal cells from female rats were slightly more active than those from male rats. Estradiol (10-8 M), when added to the medium, caused a 90% decrease in 5α-reductase activity. Aromatase activity was minimal, several orders of magnitude less than 5α-reductase activity in each tissue studied

  10. Regulation of ribonucleotide reductase by Spd1 involves multiple mechanisms

    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...

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

    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.

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

    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

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

    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.

  14. Aldose reductase inhibitory activity and antioxidant capacity of pomegranate extracts

    Karasu, Çimen; CUMAOĞLU, Ahmet; Gürpinar, Ali Rifat; KARTAL, Murat; Kovacikova, Lucia; Milackova, Ivana; Stefek, Milan

    2012-01-01

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

  15. Quantification of protein thiols and dithiols in the picomolar range using sodium borohydride and 4,4'-dithiodipyridine.

    Hansen, Rosa E; Østergaard, Henrik; Nørgaard, Per; Winther, Jakob R

    2007-04-01

    Experimental determination of the number of thiols in a protein requires methodology that combines high sensitivity and reproducibility with low intrinsic thiol oxidation disposition. In detection of disulfide bonds, it is also necessary to efficiently reduce disulfides and to quantify the liberated thiols. Ellman's reagent (5,5'-dithiobis-[2-nitrobenzoic acid], DTNB) is the most widely used reagent for quantification of protein thiols, whereas dithiothreitol (DTT) is commonly used for disulfide reduction. DTNB suffers from a relatively low sensitivity, whereas DTT reduction is inconvenient because the reagent must be removed before thiol quantification. Furthermore, both reagents require a reaction pH > 7.0 where oxidation by ambient molecular oxygen is significant. Here we describe a quick and highly sensitive assay for protein thiol and dithiol quantification using the reducing agent sodium borohydride and the thiol reagent 4,4'-dithiodipyridine (4-DPS). Because borohydride is efficiently destroyed by the addition of acid, the complete reduction and quantification can be performed conveniently in one tube without desalting steps. Furthermore, the use of reverse-phase high-performance liquid chromatography for the thiol quantification by 4-DPS reduces the detection limit to the picomolar range (equivalent to 1 microg of a 50-kDa protein containing 1 thiol) while at the same time maintaining low pH throughout the procedure. PMID:17286954

  16. Facile homolytic CS bond breaking: the reaction of 2-propene-1-thiol on Mo(110)

    Wiegand, B. C.; Friend, C. M.; Uvdal, P.; Napier, M. E.

    1996-06-01

    Investigations of 2-propene-1-thiol on Mo(110) show that the facility for thiol desulfurization correlates with the homolytic CS bond strength of the thiol. A substantial amount of CS bond scission occurs upon adsorption of 2-propene-1-thiol on Mo(110) at 120 K based on X-ray photoelectron data. 2-Propene-1-thiol has an extremely weak CS bond because of the resonance stabilization of the allyl radical. Propene, the product of 2-propene-1-thiol hydrogenolysis, evolves into the gas phase in the range 160-250 K; the propene evolution being controlled by the rate of desorption. Vibrational (electron energy loss) spectra are consistent with formation of 2-propene-1-thiolate via SH bond cleavage, as well as hydrocarbon fragments at low temperature. A large fraction of the thiolate desulfurizes at 120 K to afford propene. A second hydrocarbon species is formed in the range 160-200 K, characterized by a low-frequency CH stretch mode at 2770 cm -1, which reacts further below 250 K. The CC bond in the thiol and in the propene product leads to a greater degree of non-selective reaction than is anticipated from a comparison of saturated thiols. Only in the order of 50% of the thiol reacts to afford propene, despite the facility for CS bond scission.

  17. Evaluation of Thiol Raman Activities and pKa Values Using Internally Referenced Raman-Based pH Titration.

    Suwandaratne, Nuwanthi; Hu, Juan; Siriwardana, Kumudu; Gadogbe, Manuel; Zhang, Dongmao

    2016-04-01

    Thiols, including organothiol and thiol-containing biomolecules, are among the most important classes of chemicals that are used broadly in organic synthesis, biological chemistry, and nanosciences. Thiol pKa values are key indicators of thiol reactivity and functionality. Reported herein is an internally referenced Raman-based pH titration method that enables reliable quantification of thiol pKa values for both mono- and dithiols in water. The degree of thiol ionization is monitored directly using the peak intensity of the S-H stretching feature in the 2600 cm(-1) region relative to an internal reference peak as a function of the titration solution's pH. The thiol pKa values and Raman activity relative to its internal reference were then determined by curve fitting the experimental data with equations derived on the basis of the Henderson-Hasselbalch equation. Using this Raman titration method, we determined for the first time the first and second thiol pKa values for 1,2-benzenedithiol in water. This Raman-based method is convenient to implement, and its underlying theory is easy to follow. It should therefore have broad application for thiol pKa determinations and verification. PMID:26956547

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

    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.

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

    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

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

    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

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

    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.

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

    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

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

    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.

  4. Pore surface engineering in a zirconium metal–organic framework via thiol-ene reaction

    A porous olefin-functionalized Zr(IV)-based metal–organic framework, denoted as UiO-68-allyl, has been constructed. Our results clearly demonstrated that the surface of UiO-68-allyl could be decorated with organic molecule (ethanethiol) via thiol-ene reaction. More importantly, the crystallinity of the framework were maintained during the post-synthetic modification process. However, the microporosity of the framework is retained but the surface area decreased, due to the grafting of ethylthio groups into the pores. From our studies, we can conclude that the strategy of post-synthetic modification of UiO-68-allyl via thiol-ene reaction may be general. Furthermore, we may anchor other desired functional group onto the pore walls in Zr-MOFs via thiol-ene reaction, enabling more potential applications. - graphical abstract: In this manuscript, we reported the post-synthetic modification of an olefin-functionalized Zr(IV)-based metal–organic framework via thiol-ene reaction. - Highlights: • A porous olefin-functionalized Zr(IV)-based metal–organic framework has been constructed. • The surface of olefin-functionalized Zr-MOF could be decorated with organic molecules via thiol-ene reaction. • The crystallinity and permanent porosity of the framework were maintained during the post-synthetic modification process

  5. A Central Role for Thiols in Plant Tolerance to Abiotic Stress

    Lyuben Zagorchev

    2013-04-01

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

  6. A central role for thiols in plant tolerance to abiotic stress.

    Zagorchev, Lyuben; Seal, Charlotte E; Kranner, Ilse; Odjakova, Mariela

    2013-01-01

    Abiotic stress poses major problems to agriculture and increasing efforts are being made to understand plant stress response and tolerance mechanisms and to develop new tools that underpin successful agriculture. However, the molecular mechanisms of plant stress tolerance are not fully understood, and the data available is incomplete and sometimes contradictory. Here, we review the significance of protein and non-protein thiol compounds in relation to plant tolerance of abiotic stress. First, the roles of the amino acids cysteine and methionine, are discussed, followed by an extensive discussion of the low-molecular-weight tripeptide, thiol glutathione, which plays a central part in plant stress response and oxidative signalling and of glutathione-related enzymes, including those involved in the biosynthesis of non-protein thiol compounds. Special attention is given to the glutathione redox state, to phytochelatins and to the role of glutathione in the regulation of the cell cycle. The protein thiol section focuses on glutaredoxins and thioredoxins, proteins with oxidoreductase activity, which are involved in protein glutathionylation. The review concludes with a brief overview of and future perspectives for the involvement of plant thiols in abiotic stress tolerance. PMID:23549272

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

    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

  8. Pore surface engineering in a zirconium metal–organic framework via thiol-ene reaction

    Gui, Bo; Hu, Guiping; Zhou, Tailin; Wang, Cheng, E-mail: chengwang@whu.edu.cn

    2015-03-15

    A porous olefin-functionalized Zr(IV)-based metal–organic framework, denoted as UiO-68-allyl, has been constructed. Our results clearly demonstrated that the surface of UiO-68-allyl could be decorated with organic molecule (ethanethiol) via thiol-ene reaction. More importantly, the crystallinity of the framework were maintained during the post-synthetic modification process. However, the microporosity of the framework is retained but the surface area decreased, due to the grafting of ethylthio groups into the pores. From our studies, we can conclude that the strategy of post-synthetic modification of UiO-68-allyl via thiol-ene reaction may be general. Furthermore, we may anchor other desired functional group onto the pore walls in Zr-MOFs via thiol-ene reaction, enabling more potential applications. - graphical abstract: In this manuscript, we reported the post-synthetic modification of an olefin-functionalized Zr(IV)-based metal–organic framework via thiol-ene reaction. - Highlights: • A porous olefin-functionalized Zr(IV)-based metal–organic framework has been constructed. • The surface of olefin-functionalized Zr-MOF could be decorated with organic molecules via thiol-ene reaction. • The crystallinity and permanent porosity of the framework were maintained during the post-synthetic modification process.

  9. Methylenetetrahydrofolate Reductase Activity and Folate Metabolism

    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.

  10. Aldose reductase mediates retinal microglia activation.

    Chang, Kun-Che; Shieh, Biehuoy; Petrash, J Mark

    2016-04-29

    Retinal microglia (RMG) are one of the major immune cells in charge of surveillance of inflammatory responses in the eye. In the absence of an inflammatory stimulus, RMG reside predominately in the ganglion layer and inner or outer plexiform layers. However, under stress RMG become activated and migrate into the inner nuclear layer (INL) or outer nuclear layer (ONL). Activated RMG in cell culture secrete pro-inflammatory cytokines in a manner sensitive to downregulation by aldose reductase inhibitors. In this study, we utilized CX3CR1(GFP) mice carrying AR mutant alleles to evaluate the role of AR on RMG activation and migration in vivo. When tested on an AR(WT) background, IP injection of LPS induced RMG activation and migration into the INL and ONL. However, this phenomenon was largely prevented by AR inhibitors or in AR null mice, or was exacerbated in transgenic mice that over-express AR. LPS-induced increases in ocular levels of TNF-α and CX3CL-1 in WT mice were substantially lower in AR null mice or were reduced by AR inhibitor treatment. These studies demonstrate that AR expression in RMG may contribute to the proinflammatory phenotypes common to various eye diseases such as uveitis and diabetic retinopathy. PMID:27033597

  11. Binding of Fidarestat Stereoisomers with Aldose Reductase

    Dae-Sil Lee

    2006-11-01

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

  12. Mutant AhpC peroxiredoxins suppress thiol-disulfide redox deficiencies and acquire deglutathionylating activity

    Yamamoto, Yuji; Ritz, Dani; Planson, Anne-Gaëlle; Jönsson, Thomas J.; Faulkner, Melinda J.; Boyd, Dana; Beckwith, Jon; Poole, Leslie B.

    2008-01-01

    The bacterial peroxiredoxin AhpC, a cysteine-dependent peroxidase, can be converted through a single amino acid insertion to a disulfide reductase, AhpC*, active in the glutathione and glutaredoxin pathway. Here we show that, whereas AhpC* is inactive as a peroxidase, other point mutants in AhpC can confer the in vivo disulfide reductase activity without abrogating peroxidase activity. Moreover, AhpC* and several point mutants tested in vitro exhibit an enhanced reductase activity toward mixe...

  13. Expression, purification, crystallization and preliminary X-ray crystallographic studies of alkyl hydroperoxide reductase (AhpC) from the cyanobacterium Anabaena sp. PCC 7120

    Alkyl hydroperoxide reductase from Anabaena sp. PCC 7120 was expressed, purified and crystallized. Diffraction data to 2.5 Å resolution revealed that the crystals belonged to space group P212121, with unit-cell parameters a = 80, b = 102, c = 109.6 Å. Alkyl hydroperoxide reductase (AhpC) is a key component of a large family of thiol-specific antioxidant (TSA) proteins distributed among prokaryotes and eukaryotes. AhpC is involved in the detoxification of reactive oxygen species (ROS) and reactive sulfur species (RSS). Sequence analysis of AhpC from the cyanobacterium Anabaena sp. PCC 7120 shows that this protein belongs to the 1-Cys class of peroxiredoxins (Prxs). It has recently been reported that enhanced expression of this protein in Escherichia coli offers tolerance to multiple stresses such as heat, salt, copper, cadmium, pesticides and UV-B. However, the structural features and the mechanism behind this process remain unclear. To provide insights into its biochemical function, AhpC was expressed, purified and crystallized by the hanging-drop vapour-diffusion method. Diffraction data were collected to a maximum d-spacing of 2.5 Å using synchrotron radiation. The crystal belonged to space group P212121, with unit-cell parameters a = 80, b = 102, c = 109.6 Å. The structure of AhpC from Anabaena sp. PCC 7120 was determined by molecular-replacement methods using the human Prx enzyme hORF6 as the template

  14. The role of light in the inducation of nitrate reductase and nitrite reductase in cucumber seedlings

    J. Buczek

    2015-05-01

    Full Text Available The activity of nitrate reductase (NR and nitrite reductase (NiR was investigated in vivo and in vitro in the roots and NR activity in 3-day-old cotyledons of cucumber seedlings. NR activity in the roots appears almost immediately after addition of nitrate ions to the induction medium, whereas, in the cotyledones NR induction is delayed. In general light enhances NR activity in the cotyledons and depresses it in the roots in experiments of short duration. Etiolation of the cotyledons reduces NR activity in the roots and leads to disappearance of the activity of this enzyme in the cotyledons, whereas the NR activity of roots kept in darkness, after transfer of the etiolated plants to light, increases threefold. In roots growing in darkness a delay in NiR induction is observed, while in those growing in ligth it occurs at the same time as NR induction. Chlormaphenicol (CAP, cycloheximide (CHI and actinomycin D (ACM applied at the beginning of the period of seedling induction with initrates inhibit NR activity in the cotyledons, whereas in the roots only CHI and ACM exert such an effect. To sum up, NR is synthesized in cucumber roots and cotyledons de novo on the cytoplasmic polyribosomes, and light per se is not indispensable for this synthesis, but it has an indirect influence on the activity level of NR and NiR both in the roots and the cotyledons.

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

    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.

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

    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

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

    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.

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

    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.

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

    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 CdCl2 concentrations (0, 30, 50 and 70 μM). Levels of cadmium, cysteine, glutathione (GSH), γ-glutamylcysteine (γ-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 γ-EC. This is the first report of induction of thiol peptides, presumably phytochelatins, by a trace metal in a sea grass species

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

    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.

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

    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.

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

    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.

  3. Mutations in the RAM network confer resistance to the thiol oxidant 4,4'-dipyridyl disulfide

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

    2008-01-01

    Thiol oxidants are expected to have multiple effects in living cells. Hence, mutations giving resistance to such agents are likely to reveal important targets and/or mechanisms influencing the cellular capacity to withstand thiol oxidation. A screen for mutants resistant to the thiol......-specific oxidant dipyridyl disulfide (DPS) yielded tao3-516, which is impaired in the function of the RAM signaling network protein Tao3/Pag1p. We suggest that the DPS-resistance of the tao3-516 mutant might be due to deficient cell-cycle-regulated production of the chitinase Cts1p, which functions in post...... might relate to bypass for abnormal septum-associated protein sorting. The broad resistance toward oxidants (DPS, diamide and H(2)O(2)) of the Deltacts1 strain links cell wall function to the resistance to oxidative stress and suggests the existence of targets that are common for these oxidants....

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

    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), mat (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

  5. Study of radiation induced oxidation of thiol compounds in aqueous solutions

    The radiolysis of 2-aminoethanethiol and 2-mercapto-1-sulfonic acid in oxygen-containing aqueous solutions was studied. The values of the yields G(-O2) and G(-RSH) at different pH, thiol concentrations and dose rates are obtained. For 2-aminoethanethiol the yields of taurine in the solutions in the presence of N2O and O2 are obtained too. Reaction of 2-aminoethanethiol with superoxide radical-anions was studied, the O2- anions being generated by nonradiation methods. The mechanism of chain reaction is suggested including the formation of electron-exited states of thiol molecules and products molecules, followed by the energy transfer from the products to another thiol molecules. 19 refs.; 6 figs.; 2 tabs

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

    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.

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

    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

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

    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.

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

    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

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

    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.

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

    Kuciński, K; Pawluć, 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

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

    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...

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

    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

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

    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.

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

    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...

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

    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 ...

  17. Human cytochrome b5 reductase: structure, function, and potential applications.

    Elahian, Fatemeh; Sepehrizadeh, Zargham; Moghimi, Bahareh; Mirzaei, Seyed Abbas

    2014-06-01

    Cytochrome b5 reductase is a flavoprotein that is produced as two different isoforms that have different localizations. The amphipathic microsomal isoform, found in all cell types with the exception of erythrocytes, consists of one hydrophobic membrane-anchoring domain and a larger hydrophilic flavin catalytic domain. The soluble cytochrome b5 reductase isoform, found in human erythrocytes, is a truncated protein that is encoded by an alternative transcript and consists of the larger domain only. Cytochrome b5 reductase is involved in the transfer of reducing equivalents from the physiological electron donor, NADH, via an FAD domain to the small molecules of cytochrome b5. This protein has received much attention from researchers due to its involvement in many oxidation and reduction reactions, such as the reduction of methemoglobin to hemoglobin. Autosomal cytochrome b5 reductase gene deficiency manifests with the accumulation of oxidized Fe+3 and recessive congenital methemoglobinemia in humans. In this article, we provide a comprehensive overview of the structure and function of cytochrome b5 reductase from different eukaryotic sources and its potential use in the food industry, biosensor, and diagnostic areas. PMID:23113554

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

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

    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 studies of the Pseudomonas stutzeri enzyme, we observed that a marked negative cooperativity is...... 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...

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

    Zhuang, Guisheng; Jensen, Thomas Glasdam; Kutter, Jörg Peter

    In this paper, a thiol-ene based polymer waveguide, defined by UV-assisted soft lithography, is designed, fabricated and characterized. Waveguides are formed by filling microfluidic channels with a high refractive index liquid mixture of ‘thiol’ and ‘ene’ monomers (e.g., trimethylolpropane tris(3...

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

    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.

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

    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

  3. Kinetic and thermodynamic aspects of cellular thiol-disulfide redox regulation.

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

    2009-05-01

    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 (pK(a)), the local electrostatic environment, molecular strain, and entropy. Even though a thiol-disulfide exchange reaction is thermodynamically favorable, it will only take place if the activation energy to form the transition state complex can be overcome. This is accomplished by enzymes, such as the oxidoreductases, that direct reactions in thermodynamically favorable directions by decreasing the activation energy barrier. PMID:19014315

  4. Building thiol and metal-thiolate functions into coordination nets: Clues from a simple molecule

    The simple and easy-to-prepare bifunctional molecule 2,5-dimercapto-1,4-benzenedicarboxylic acid (H4DMBD) interacts with the increasingly harder metal ions of Cu+, Pb2+ and Eu3+ to form the coordination networks of Cu6(DMBD)3(en)4(Hen)6 (1), Pb2(DMBD)(en)2 (2) and Eu2(H2DMBD)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 Cu3 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 Pb2+ 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. - Graphical Abstract: Molecule 2,5-dimercapto-1,4-benzenedicarboxylic acid was reacted with Cu+, Pb2+ and Eu3+ ions to explore solid state networks with the rich structural features arising from the carboxyl-thiol combination.

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

    Javakhishvili, Irakli; Hvilsted, Søren

    2008-01-01

    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...

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

    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...

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

    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.

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

    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

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

    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.

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

    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.

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

    Olga Krystofova; Václav Diopan; Jiří Baloun; Vojtech Adam; Rene Kizek*

    2010-01-01

    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.

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

    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 210 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.

  13. Effect of thiols enrichment on Cr(VI) photo-reduction by natural organic matter (NOM).

    Luo, Hong-Wei

    2016-05-01

    Photochemical redox transformation of Cr(VI)-NOM complexes substantially affects transport and speciation of less toxic Cr(III) in natural waters. However, the underlying mechanisms remain unclear. This study reported photochemical reactions of Cr(VI) with thiol-enriched NOM under acidic condition. More effective thiols enrichment in humic acid (HA) was observed than that in fulvic acid (FA), thereby resulting in a higher reduction capacity and faster rate of Cr(VI) photo-reduction. Chemical addition of sulfide to HA formed a large number of S-containing molecular formulae, which subsequently disappeared following reactions with Cr(VI) under solar irradiation. Cr(VI) photo-reduction in thiol-enriched HA consumed more S-containing formulae. Solar irradiation caused a rapid loss of the reduction capacities and thiol contents in HA and FA. All these findings can provide useful information for understanding the biogeochemical cycles of chromium and sulfur, and are also of environmental significance because they may partially account for photo-transformation of Cr(VI) when chromium enters into the aquatic environment as acidic industrial effluents. PMID:26946114

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

    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

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

    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.

  16. Endothelium-dependent vasorelaxation in inhibited by in vivo depletion of vascular thiol levels

    Laursen, J B; Boesgaard, S; Trautner, S; Rubin, I; Poulsen, H E; Aldershvile, J

    2001-01-01

    ) affected by BSO (BSO: 4415 +/- 123, control: 4105 +/- 455 counts/mg; n = 6) in rat aorta. It is concluded that in vivo thiol depletion results in endothelial dysfunction and a reduced receptor-mediated vascular relaxation. This effect is caused by reduced endothelial NO formation....

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

    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

  18. Plasmid-encoded diacetyl (acetoin) reductase in Leuconostoc pseudomesenteroides

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

    2003-01-01

    A plasmid-borne diacetyl (acetoin) reductase (butA) from Leuconostoc pseudomesenteroides CHCC2114 was sequenced and cloned. Nucleotide sequence analysis revealed an open reading frame encoding a protein of 257 amino acids which had high identity at the amino acid level to diacetyl (acetoin......) reductases reported previously. Downstream of the butA gene of L. pseudomesenteroides, but coding in the opposite orientation, a putative DNA recombinase was identified. A two-step PCR approach was used to construct FPR02, a butA mutant of the wild-type strain, CHCC2114. FPR02 had significantly reduced...

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

    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 μM, 1000 μM 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.

  20. Determination of thiol metabolites in human urine by stable isotope labeling in combination with pseudo-targeted mass spectrometry analysis

    Liu, Ping; Qi, Chu-Bo; Zhu, Quan-Fei; Yuan, Bi-Feng; Feng, Yu-Qi

    2016-02-01

    Precursor ion scan and multiple reaction monitoring scan (MRM) are two typical scan modes in mass spectrometry analysis. Here, we developed a strategy by combining stable isotope labeling (IL) with liquid chromatography-mass spectrometry (LC-MS) under double precursor ion scan (DPI) and MRM for analysis of thiols in 5 types of human cancer urine. Firstly, the IL-LC-DPI-MS method was applied for non-targeted profiling of thiols from cancer samples. Compared to traditional full scan mode, the DPI method significantly improved identification selectivity and accuracy. 103 thiol candidates were discovered in all cancers and 6 thiols were identified by their standards. It is worth noting that pantetheine, for the first time, was identified in human urine. Secondly, the IL-LC-MRM-MS method was developed for relative quantification of thiols in cancers compared to healthy controls. All the MRM transitions of light and heavy labeled thiols were acquired from urines by using DPI method. Compared to DPI method, the sensitivity of MRM improved by 2.1–11.3 folds. In addition, the concentration of homocysteine, γ-glutamylcysteine and pantetheine enhanced more than two folds in cancer patients compared to healthy controls. Taken together, the method demonstrated to be a promising strategy for identification and comprehensive quantification of thiols in human urines.

  1. Reaction Mechanisms of Metals with Hydrogen Sulfide and Thiols in Model Wine. Part 1: Copper-Catalyzed Oxidation.

    Kreitman, Gal Y; Danilewicz, John C; Jeffery, David W; Elias, Ryan J

    2016-05-25

    Sulfidic off-odors as a result of hydrogen sulfide (H2S) and low-molecular-weight thiols are commonly encountered in wine production. These odors are usually removed by the process of Cu(II) fining, a process that remains poorly understood. The present study aims to elucidate the underlying mechanisms by which Cu(II) interacts with H2S and thiol compounds (RSH) under wine-like conditions. Copper complex formation was monitored along with H2S, thiol, oxygen, and acetaldehyde concentrations after the addition of Cu(II) (50 or 100 μM) to air-saturated model wine solutions containing H2S, cysteine, 6-sulfanylhexan-1-ol, or 3-sulfanylhexan-1-ol (300 μM each). The presence of H2S and thiols in excess to Cu(II) led to the rapid formation of ∼1.4:1 H2S/Cu and ∼2:1 thiol/Cu complexes, resulting in the oxidation of H2S and thiols and reduction of Cu(II) to Cu(I), which reacted with oxygen. H2S was observed to initially oxidize rather than form insoluble copper sulfide. The proposed reaction mechanisms provide insight into the extent to which H2S can be selectively removed in the presence of thiols in wine. PMID:27133282

  2. The design of redox active thiol peroxidase mimics: Dihydrolipoic acid recognition correlates with cytotoxicity and prooxidant action.

    Zadehvakili, B; McNeill, S M; Fawcett, J P; Giles, G I

    2016-03-15

    Redox active molecules containing organoselenium or organotellurium groups catalyse the oxidation of cellular thiols by hydrogen peroxide and are currently being developed as therapeutic agents. Potentially these synthetic thiol peroxidase (TPx) mimics can protect cells from oxidative stress by catalysing the reduction of reactive oxygen species by the cellular thiol glutathione, an activity which mimics the function of the antioxidant enzyme glutathione peroxidase. Alternatively they can act as prooxidants by catalysing the oxidation of essential thiol species within the cell. However the structure-activity relationships which determine the choice of thiol substrate, and hence the overall antioxidant or prooxidant outcome of drug administration, remain unknown. We report the first study that relates the pharmacological properties of TPx mimics with their solubility and catalytic activity using different thiol substrates. We used a series of structurally related compounds PhMCnH2n+1 (M=Se, Te; n=4-7) and investigated their ability to catalyse the oxidation of the cellular thiols glutathione and dihydrolipoic acid by hydrogen peroxide. The resulting rate constants (kobs) were then related to compound cytotoxicity and antioxidant versus prooxidant action in A549 cancer cells. The results show that the dihydrolipoic acid kobs values correlate with both cytotoxicity and prooxidant function. This enabled us to define a relationship, IC50=10+280e(-5(DHLA)(kobs)()), which allows the prediction of TPx mimic cytotoxicity. In contrast, hydrophobicity and glutathione kobs were unrelated to the compounds' redox pharmacology. PMID:26801688

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

    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

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

    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,...

  5. Thioredoxin reductase from s. Coelicolor as a drug target

    Koháryová, M.; Brynda, Jiří; Řezáčová, Pavlína; Kollárová, M.

    2015-01-01

    Roč. 282, Suppl 1 (2015), s. 396. ISSN 1742-464X. [ Congress of the Federation of European Biochemical Societies (FEBS) - The Biochemical Basis of Life /40./. 04.07.2015-09.07.2015, Berlin] Institutional support: RVO:61388963 ; RVO:68378050 Keywords : thioredoxin reductase * protein structure * drugs Subject RIV: CE - Biochemistry

  6. The intramolecular electron transfer between copper sites of nitrite reductase

    Farver, O; Eady, R R; Abraham, Z H; Pecht, I

    1998-01-01

    The intramolecular electron transfer (ET) between the type 1 Cu(I) and the type 2 Cu(II) sites of Alcaligenes xylosoxidans dissimilatory nitrite reductase (AxNiR) has been studied in order to compare it with the analogous process taking place in ascorbate oxidase (AO). This internal process is in...

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

    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.

  8. The arsenic hyperaccumulating Pteris vittata expresses two arsenate reductases

    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.

  9. Fatty Acyl-CoA Reductase 1 Deficiency

    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.

  10. The Kinetics and Inhibition of the Enzyme Methemoglobin Reductase

    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)

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

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

    2015-01-01

    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......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...

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

    Begara-Morales, Juan C; Snchez-Calvo, Beatriz; Chaki, Mounira; Mata-Prez, Capilla; Valderrama, Raquel; Padilla, Mara N; Lpez-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 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

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

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

    2015-01-01

    The ascorbateglutathione 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 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 ascorbateglutathione 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

  14. 3-Oxoacyl-[ACP] reductase from oilseed rape (Brassica napus).

    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

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

    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.

  16. Antimicrobial, dehydroascorbate reductase, and monodehydroascorbate reductase activities of defensin from sweet potato [Ipomoea batatas (L.) Lam. 'Tainong 57'] storage roots.

    Huang, Guan-Jhong; Lai, Hsin-Chih; Chang, Yuan-Shiun; Sheu, Ming-Jyh; Lu, Te-Ling; Huang, Shyh-Shyun; Lin, Yaw-Huei

    2008-05-14

    A cDNA encoding a small cysteine-rich protein designated defensin (SPD1) was isolated from sweet potato storage roots. On the basis of the amino acid sequence similarity and conserved residues, it is suggested that SPD1 is a member of the plant defensin family. Recombinant SPD1 protein overproduced in Escherichia coli was purified by Ni (2+)-chelated affinity chromatography. A recombinant protein from the storage root cDNA clone effectively inhibited the trypsin activity in a dose-dependent manner. Both the corresponding mRNA and protein level were found to be highest in the storage roots, followed by sprout. SPD1 reduced dehydroascorbate (DHA) in the presence of glutathione to regenerate l-ascorbic acid (AsA). However, without glutathione, SPD1 has very low DHA reductase activity, and AsA was oxidized by AsA oxidase to generate monodehydroascorbate (MDA) free radical. MDA was also reduced by SPD1 to AsA in the presence of NADH, mimicking the MDA reductase catalyzed reaction. These data suggest that SPD1 has both DHA reductase and MDA reductase activities. SPD1 was also shown to inhibit the growth of both fungi and bacteria. SPD1 is apparently the first reported plant defensin exhibiting DHA and MDA activities in vitro. PMID:18393437

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

    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 (ΦPSII), 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.

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

    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...... antioxidant pools of glutathione (GSH) and thioredoxin are required for resistance to DPS. We found that DPS-sensitive mutants display increases in the disulfide form of GSH (GSSG) during DPS exposure that roughly correlate with their more oxidizing GSH redox potential in the cytosol and their degree of DPS...

  19. Rocket fuel for the quantification of S-nitrosothiols. Highly specific reduction of S-nitrosothiols to thiols by methylhydrazine.

    Wiesweg, M; Berchner-Pfannschmidt, U; Fandrey, J; Petrat, F; de Groot, H; Kirsch, M

    2013-02-01

    Reduction of S-nitrosothiols to the corresponding thiol function is the key step in analyzing S-nitrosocysteinyl residues in proteins. Though it has been shown to give low yields, ascorbate-dependent reduction is commonly performed in the frequently used biotin-switch technique. We demonstrate that the compound methylhydrazine can act as a specific and efficient reducing agent for S-nitrosothiols. The corresponding thiol function is exclusively generated from low molecular weight and proteinaceous S-nitrosothiols while methylhydrazine failed to reduce disulfides. It was possible to optimize the experimental conditions so that thiol autoxidation is excluded, and high reaction yields (>90%) are obtained for the thiol function. The biotin-switch technique performed with methylhydrazine-dependent reduction shows remarkably improved sensitivity compared to the ascorbate-dependent procedure. PMID:23181469

  20. Functionalization of Two-Dimensional MoS2 : On the Reaction Between MoS2 and Organic Thiols.

    Chen, Xin; Berner, Nina C; Backes, Claudia; Duesberg, Georg S; McDonald, Aidan R

    2016-05-01

    Two-dimensional layered transition metal dichalcogenides (TMDs) have attracted great interest owing to their unique properties and a wide array of potential applications. However, due to their inert nature, pristine TMDs are very challenging to functionalize. We demonstrate a general route to functionalize exfoliated 2H-MoS2 with cysteine. Critically, MoS2 was found to be facilitating the oxidation of the thiol cysteine to the disulfide cystine during functionalization. The resulting cystine was physisorbed on MoS2 rather than coordinated as a thiol (cysteine) filling S-vacancies in the 2H-MoS2 surface, as originally conceived. These observations were found to be true for other organic thiols and indeed other TMDs. Our findings suggest that functionalization of two-dimensional MoS2 using organic thiols may not yield covalently or datively tethered functionalities, rather, in this instance, they yield physisorbed disulfides that are easily removed. PMID:27038093

  1. Odorant Screening and Quantitation of Thiols in Carmenere Red Wine by Gas Chromatography-Olfactometry and Stable Isotope Dilution Assays.

    Pavez, Carolina; Agosin, Eduardo; Steinhaus, Martin

    2016-05-01

    The sensory impact of thiols in Vitis vinifera 'Carmenere' red wines was evaluated. For this purpose, aroma extract dilution analysis was applied to the thiols isolated from a Carmenere red wine by affinity chromatography with a mercurated agarose gel. Results revealed the presence of four odorants, identified as 2-furanylmethanethiol, 3-sulfanylhexyl acetate, 3-sulfanyl-1-hexanol, and 2-methyl-3-sulfanyl-1-butanol, with the latter being described here for the first time in Carmenere red wines. Quantitation of the four thiols in the Carmenere wine screened by aroma extract dilution analysis and in three additional Carmenere wines by stable isotope dilution assays resulted in concentrations above the respective orthonasal odor detection threshold values. Triangle tests applied to wine model solutions with and without the addition of the four thiols showed significant differences, thus suggesting that the compounds do have the potential to influence the overall aroma of red wine. PMID:27070203

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

    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...... 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...

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

    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...

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

    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)

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

    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)

  6. XAFS, SAXS and HREM characterization of Pd nanoparticles capped with n-alkyl thiol molecules

    We report a structural characterization of palladium nanoparticles, with an average diameter of 1.2 nm, capped with three different n-alkyl thiol molecules (n=12, 16 and 18). For this purpose several experimental techniques were used, namely X-ray absorption fine structure (XAFS), small angle X-ray scattering (SAXS) and high-resolution electron transmission microscopy (HRTEM). SAXS and HRTEM results yielded the sizes of the Pd nanoparticles in each sample. The effects of sulfur-palladium interaction on the structural and electronic properties of the studied material were derived from XAFS results. This study indicates the presence of sulfurized palladium in the bulk of the three studied capped Pd nanoparticles. Slight variations in the degree of sulfidation were detected for nanoclusters with different thiol chain lengths

  7. XAFS, SAXS and HREM characterization of Pd nanoparticles capped with n-alkyl thiol molecules

    Ramallo-Lopez, J.M. [Dto. Fisica, FCE, UNLP e IFLP-INIFTA (CONICET). CC67- CP 1900 La Plata (Argentina)]. E-mail: ramallo@fisica.unlp.edu.ar; Giovanetti, L. [Dto. Fisica, FCE, UNLP e IFLP-INIFTA (CONICET). CC67- CP 1900 La Plata (Argentina); Craievich, A.F. [Institute of Physics, University of Sao Paulo, CEP 05508-900 Sao Paulo, SP (Brazil); Vicentin, F.C. [Laboratorio Nacional de Luz Sincrotron, Caixa Postal 6192, 13084-971 Campinas, SP (Brazil); Marin-Almazo, M. [Instituto Nacional de Investigaciones Nucleares-Mexico D. F. (Mexico); Jose-Yacaman, M. [Texas Materials Institute Center for Nano and Molecular Tech-Austin TX (United States); Requejo, F.G. [Dto. Fisica, FCE, UNLP e IFLP-INIFTA (CONICET). CC67- CP 1900 La Plata (Argentina)

    2007-02-01

    We report a structural characterization of palladium nanoparticles, with an average diameter of 1.2 nm, capped with three different n-alkyl thiol molecules (n=12, 16 and 18). For this purpose several experimental techniques were used, namely X-ray absorption fine structure (XAFS), small angle X-ray scattering (SAXS) and high-resolution electron transmission microscopy (HRTEM). SAXS and HRTEM results yielded the sizes of the Pd nanoparticles in each sample. The effects of sulfur-palladium interaction on the structural and electronic properties of the studied material were derived from XAFS results. This study indicates the presence of sulfurized palladium in the bulk of the three studied capped Pd nanoparticles. Slight variations in the degree of sulfidation were detected for nanoclusters with different thiol chain lengths.

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

    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.

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

    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 ini...... 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....

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

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

    2011-01-01

    We present an efficient method for functionalizing the large polymerair 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, UVVis, 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. Topdown 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....

  11. Thiol-ene Photocrosslinking of Cytocompatible Resilin-Like Polypeptide-PEG Hydrogels.

    McGann, Christopher L; Dumm, Rebekah E; Jurusik, Anna K; Sidhu, Ishnoor; Kiick, Kristi L

    2016-01-01

    A range of chemical strategies have been used for crosslinking recombinant polypeptide hydrogels, although only a few have employed photocrosslinking approaches. Here, we capitalize on the novel insect protein, resilin, and the versatility of click reactions to introduce a resilin-like polypeptide (RLP) that is capable of photoinitiated thiol-ene crosslinking. Lysine residues of the RLP were functionalized with norbornene acid as confirmed via 1H-NMR spectroscopy. The RLPNs were subsequently photocrosslinked with multi-arm PEG thiols in the presence of a photoinitiator to form elastic hybrid hydrogels. The crosslinking reaction and resulting RLP-PEG networks demonstrated cytocompatibility with human mesenchymal stem cells in both 2D cell-adhesion and 3D photoencapsulation studies. PMID:26435299

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

    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

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

    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.

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

    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

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

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

  16. Fatty Acid Derived Monomers and Related Polymers Via Thiol-ene (Click) Additions.

    Türünç, Oĝuz; Meier, Michael A R

    2010-10-18

    Thiol-ene additions of methyl 10-undecenoate, a castor oil derived renewable platform chemical, were studied with the goal of preparing a set of renewable monomers. Good to excellent yields were obtained for these solvent and initiator free thiol-ene additions. The resulting monomers were then polymerized using TBD as a catalyst, to linear as well as hyperbranched polyesters that also contain thio-ether linkages. All thus prepared polymers were fully characterized (NMR, GPC, DSC, and TGA) and the results of these investigations will be discussed within this contribution. The thermal analysis of these polymers revealed melting points in the range from 50 to 71 °C. Moreover, no significant weight loss was observed below 300 °C. PMID:21567600

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

    Lee, Jungmin; Varadan, Vijay K.

    2011-04-01

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

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

    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.

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

    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.

  20. The effects of acrolein on peroxiredoxins, thioredoxins, and thioredoxin reductase in human bronchial epithelial cells

    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 μM 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 μM 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

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

    Frein, Stphane; Boudon, Julien; Vonlanthen, Mireille; Scharf, Toral; Barber, Joaqun; Sss-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...

  2. Surface plasmon resonance and magnetism of thiol-capped gold nanoparticles

    Guerrero, Estefanía; Muñoz-Márquez, Miguel Ángel; García, M.A.; Crespo, Patricia; Fernández-Pinel, Enrique; Hernando, Antonio; Fernández-Camacho, A.

    2008-01-01

    Surface plasmon resonance measurements and magnetic characterization studies have been carried out for two types of thiol-capped gold nanoparticles (NPs) with similar diameters between 2.0 and 2.5 nm and different organic molecules linked to the sulfur atom: dodecanethiol and tiopronin. In addition, Au NPs capped with tetraoctyl ammonium bromide have also been included in the investigation since such capping molecules weakly interact with the gold surface atoms and, therefore, this system can...

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

    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.

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

    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...

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

    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...

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

    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)

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

    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)

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

    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.

  9. Automated synthesis of [18F] FBEM for labeling of thiol containing compounds

    Paris, Jérôme; Thonon, David; Kaisin, Geoffroy; Goblet, David; Goukens, Eve; Lacroix, Simon; Luxen, André

    2011-01-01

    [18F]FBEM, i.e. N-[2-(4-[18F]fluorobenzamido)ethyl]maleimide, is a useful synthon employed for the specific radiolabeling of thiol containing compounds, including peptides and proteins. The aim of the present work was to develop a fast, reproducible and fully automated synthesis of this compound in order to improve its availabilty as well as for obvious radioprotection matters.

  10. A Central Role for Thiols in Plant Tolerance to Abiotic Stress

    Lyuben Zagorchev; Seal, Charlotte E.; Ilse Kranner; Mariela Odjakova

    2013-01-01

    Abiotic stress poses major problems to agriculture and increasing efforts are being made to understand plant stress response and tolerance mechanisms and to develop new tools that underpin successful agriculture. However, the molecular mechanisms of plant stress tolerance are not fully understood, and the data available is incomplete and sometimes contradictory. Here, we review the significance of protein and non-protein thiol compounds in relation to plant tolerance of abiotic stress. First,...

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

    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

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

    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...

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

    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 ...

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

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

    2013-01-01

    Using N-(2-Aminoethyl)maleimide-cysteine(StBu) (Mal-Cys) as a medium, protein thiols were converted into N-terminal cysteines. After a biocompatible condensation reaction between the N-terminal cysteine and fluorescent probe 2-cyanobenzothiazole-Gly-Gly-Gly-fluorescein isothiocyanate (CBT-GGG-FITC), a new fluorogenic structure Luciferin-GGG-FITC was obtained. The latter exhibits near one order of magnitude (7 folds) enhanced fluorescence emission compared to the precursor moiety due to fluore...

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

    Buhl, Moritz; Vonhren, 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

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

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

    2007-01-01

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

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

    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-μM (visible range) or low-μM (near-UV range) level. PMID:26654831

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

    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.

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

    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.

  20. Protein S-Mycothiolation Functions as Redox-Switch and Thiol Protection Mechanism in Corynebacterium glutamicum Under Hypochlorite Stress

    Chi, Bui Khanh; Busche, Tobias; Van Laer, Koen; Bäsell, Katrin; Becher, Dörte; Clermont, Lina; Seibold, Gerd M.; Persicke, Marcus; Kalinowski, Jörn; Messens, Joris; Antelmann, Haike

    2014-01-01

    Aims: Protein S-bacillithiolation was recently discovered as important thiol protection and redox-switch mechanism in response to hypochlorite stress in Firmicutes bacteria. Here we used transcriptomics to analyze the NaOCl stress response in the mycothiol (MSH)-producing Corynebacterium glutamicum. We further applied thiol-redox proteomics and mass spectrometry (MS) to identify protein S-mycothiolation. Results: Transcriptomics revealed the strong upregulation of the disulfide stress σH regu...

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

    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.

  2. Protective effects of exogenous glutathione and related thiol compounds against drug-induced liver injury.

    Masubuchi, Yasuhiro; Nakayama, Junpei; Sadakata, Yuka

    2011-01-01

    An overdose of acetaminophen (APAP) causes liver injury both in experimental animals and humans. N-acetylcysteine (NAC) is clinically used as an antidote for APAP intoxication, and it is thought to act by providing cysteine as a precursor of glutathione, which traps a reactive metabolite of APAP. Other hepatoprotective mechanisms of NAC have also been suggested. Here, we examined the effects of thiol compounds with different abilities to restore hepatic glutathione, on hepatotoxicity of APAP and furosemide in mice. Overnight-fasted male CD-1 mice were given APAP or furosemide intraperitoneally. NAC, cysteine, glutathione, or glutathione-monoethyl ester was administered concomitantly with APAP or furosemide. All thiol compounds used in this study effectively protected mice against APAP-induced liver injury. Only glutathione-monoethyl ester completely prevented APAP-induced early hepatic glutathione depletion. Cysteine also significantly restored hepatic glutathione levels. NAC partially restored glutathione levels. Exogenous glutathione had no effect on hepatic glutathione loss. NAC and glutathione highly stimulated the hepatic expression of cytokines, particularly interleukin-6, which might be involved in the alleviation of APAP hepatotoxicity. Furosemide-induced liver injury, which does not accompany hepatic glutathione depletion, was also attenuated by NAC and exogenous glutathione, supporting their protective mechanisms other than replenishment of glutathione. In conclusion, exogenous thiols could alleviate drug-induced liver injury. NAC and glutathione might exert their effects, at least partially, via mechanisms that are independent of increasing hepatic glutathione, but probably act through cytokine-mediated and anti-inflammatory mechanisms. PMID:21372386

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

    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.

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

    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 γ-glutamylcysteine synthetase (γ-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 μg, 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.

  5. Thiol proteinase inhibitor - Oryzacystatin. Molecular cloning and expression in E. coli

    Insect depredation is a major reason for the reduction in crop yields world-wide. Promising results have already been achieved with transgenic plants expression cowpea trypsin inhibitor (CpTI) genes and modified delta-endotoxin genes. Insects, in general, hydrolyse ingested proteins with a variety of proteinase. The effect of the serine proteinase inhibitor against Lepidopteran insects is probably caused by the preponderance of serine type gut proteinase and a luminal pH in the neutral to alkaline range. On the other hand, the insect orders Coleoptera and Hemiptera have gut pHs in the mildly acidic range and commonly have thiol type gut proteinases. Plant transformation with a gene coding for a thiol proteinase inhibitor has been suggested as a strategy for interfering with the digestive physiology of Coleopteran and Hemipteran insects. Co-transformation of both the serine proteinase inhibitor and the thiol proteinase inhibitor genes might result in a broader spectrum of activity and increased durability of protection

  6. Enhancement of volatile thiol release of Saccharomyces cerevisiae strains using molecular breeding.

    Dufour, Matthieu; Zimmer, Adrien; Thibon, Cécile; Marullo, Philippe

    2013-07-01

    Cysteine-conjugated volatile thiols are powerful aromatic compounds that contribute to the fruity notes of many white wines and especially Sauvignon Blanc. Genetic selection programs of wine yeast starters able to produce more volatile thiols constitute, therefore, an important goal for the wine industry. Recent investigations on yeast metabolism suggested that the ß-lyase Irc7p and the control of its gene expression by nitrogen catabolite repression constitute a rational way for yeast genetic improvement. This work demonstrates that the use of a natural ure2 mutation can be used to design wine starters with an enhanced capacity of volatile thiols production. By applying backcrosses driven by molecular markers, this allelic form was introduced in different starter backgrounds. Our investigations demonstrate that the ure2 inheritance is able to enhance the production of 4MMP (recently renamed 4MSP) and 3MH (recently renamed 3SH). For 4MMP, this effect depends of the presence of the allele IRC7LT encoding a long form of the Irc7 protein. Moreover, a correlation in between the expression level of this allelic form and 4MMP production was found within industrial starters. All together, these results emphasised the use of molecular breeding for improving quantitative traits of industrial strains without the use of genetically modifying strategies. PMID:23423325

  7. Polyhedral Oligomeric Silsesquioxane-Containing Thiol-ene Fibers with Tunable Thermal and Mechanical Properties.

    Fang, Yichen; Ha, Heonjoo; Shanmuganathan, Kadhiravan; Ellison, Christopher J

    2016-05-01

    Polyhedral oligomeric silsesquioxanes (POSS) are versatile inorganic-organic hybrid building blocks that have potential applications as reinforcement nanofillers, thermal stabilizers, and catalyst supports for metal nanoparticles. However, fabrication of fibrous materials with high POSS content has been a challenge because of the aggregation and solubility limits of POSS units. In this paper, we describe a robust and environmentally friendly fabrication approach of inorganic-organic hybrid POSS fibers by integrating UV initiated thiol-ene polymerization and centrifugal fiber spinning. The use of monomeric liquids in this approach not only reduces the consumption of heat energy and solvent, but it also promotes homogeneous mixing of organic and inorganic components that allows integration of large amount of POSS (up to 80 wt %) into the polymer network. The POSS containing thiol-ene fibers exhibited enhanced thermomechanical properties compared to purely organic analogs as revealed by substantial increases in residual weight and a factor of 4 increase in modulus after thermal treatment at 1000 °C. This simple fabrication approach combined with the tunability in fiber properties afforded by tailoring monomer composition make POSS containing thiol-ene fibers attractive candidates for catalyst supports and filtration media, particularly in high-temperature and harsh environments. PMID:27057758

  8. Photoinduced Cross-Linking of Dynamic Poly(disulfide) Films via Thiol Oxidative Coupling.

    Feillée, Noémi; Chemtob, Abraham; Ley, Christian; Croutxé-Barghorn, Céline; Allonas, Xavier; Ponche, Arnaud; Le Nouen, Didier; Majjad, Hicham; Jacomine, Léandro

    2016-01-01

    Initially developed as an elastomer with an excellent record of barrier and chemical resistance properties, poly(disulfide) has experienced a revival linked to the dynamic nature of the S-S covalent bond. A novel photobase-catalyzed oxidative polymerization of multifunctional thiols to poly(disulfide) network is reported. Based solely on air oxidation, the single-step process is triggered by the photodecarboxylation of a xanthone acetic acid liberating a strong bicyclic guanidine base. Starting with a 1 μm thick film based on trithiol poly(ethylene oxide) oligomer, the UV-mediated oxidation of thiols to disulfides occurs in a matter of minutes both selectively, i.e., without overoxidation, and quantitatively as assessed by a range of spectroscopic techniques. Thiolate formation and film thickness determine the reaction rates and yield. Spatial control of the photopolymerization serves to generate robust micropatterns, while the reductive cleavage of S-S bridges allows the recycling of 40% of the initial thiol groups. PMID:26502361

  9. Building thiol and metal-thiolate functions into coordination nets: Clues from a simple molecule

    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.

  10. DNA repair by thiols in air shows two radicals make a double-strand break

    Using agarose gel electrophoresis, we have measured the yields of DNA single- and double-strand breaks (SSBs and DSBs) for plasmid DNA γ-irradiated in aerobic aqueous solution. The presence during irradiation of either of the thiols cysteamine or N-(2-thioethyl)-1,3-diaminopropane (WR-1065) resulted in a concentration-dependent decrease in the yield of SSBs and a much greater decrease in the yield of DSBs. This large differential protective effect was not produced by thioethers or an alcohol of structural similarity to the two thiols, suggesting that repair of DSB radical precursors by thiols is more efficient than for SSB precursors. These observations suggest the existence of a diradical intermediate in the formation of DSBs. The results argue against a major contribution by a single radical mechanism involving interstrand radical transfer via hydrogen abstraction by a peroxyl intermediate, since the half-life of this radical transfer reaction appears to be significantly greater than the lifetime of the intermediate. 35 refs., 7 figs

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

    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 ...

  12. A new turn-on chemosensor for bio-thiols based on the nanoaggregates of a tetraphenylethene-coumarin fluorophore

    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

  13. Highly Selective Fluorescent Turn-On Probe for Protein Thiols in Biotin Receptor-Positive Cancer Cells.

    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

  14. para-sulfobenzoyloxybromobimane: a new membrane-impermeable reagent useful for the analysis of thiols and their export from cells.

    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

  15. Resin-assisted enrichment of thiols as a general strategy for proteomic profiling of cysteine-based reversible modifications

    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.

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

    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

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

    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

  18. Regulation of ribonucleotide reductase by Spd1 involves multiple mechanisms

    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...

  19. Rapid Identification of Aldose Reductase Inhibitory Compounds from Perilla frutescens

    Soon Sung Lim; Ji Hun Paek; Kuk Hyun Shin; Young-Hee Kang; Jae-Yong Lee

    2013-01-01

    The ethyl acetate (EtOAc) soluble fraction of methanol extracts of Perilla frutescens (P. frutescens) inhibits aldose reductase (AR), the key enzyme in the polyol pathway. Our investigation of inhibitory compounds from the EtOAc soluble fraction of P. frutescens was followed by identification of the inhibitory compounds by a combination of HPLC microfractionation and a 96-well enzyme assay. This allowed the biological activities to be efficiently matched with selected HPLC peaks. Structural a...

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

    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...

  1. Bcl2 induces DNA replication stress by inhibiting ribonucleotide reductase

    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...

  2. Role of Helicobacter pylori methionine sulfoxide reductase in urease maturation

    Kuhns, Lisa G.; Mahawar, Manish; Sharp, Joshua S.; Benoit, Stéphane; Maier, Robert J

    2013-01-01

    The persistence of the gastric pathogen Helicobacter pylori is due in part to urease and Msr (methionine sulfoxide reductase). Upon exposure to relatively mild (21% partial pressure of O2) oxidative stress, a Δmsr mutant showed both decreased urease specific activity in cell-free extracts and decreased nickel associated with the partially purified urease fraction as compared with the parent strain, yet urease apoprotein levels were the same for the Δmsr and wild-type extracts. Urease activity...

  3. Characterization of Binding Pocket Flexibility of Aldose Reductase

    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 ...

  4. Structural and functional diversity of ferredoxin-NADP(+) reductases.

    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

  5. Perchlorate Reductase Is Distinguished by Active Site Aromatic Gate Residues.

    Youngblut, Matthew D; Tsai, Chi-Lin; Clark, Iain C; Carlson, Hans K; Maglaqui, Adrian P; Gau-Pan, Phonchien S; Redford, Steven A; Wong, Alan; Tainer, John A; Coates, John D

    2016-04-22

    Perchlorate is an important ion on both Earth and Mars. Perchlorate reductase (PcrAB), a specialized member of the dimethylsulfoxide reductase superfamily, catalyzes the first step of microbial perchlorate respiration, but little is known about the biochemistry, specificity, structure, and mechanism of PcrAB. Here we characterize the biophysics and phylogeny of this enzyme and report the 1.86-Å resolution PcrAB complex crystal structure. Biochemical analysis revealed a relatively high perchlorate affinity (Km = 6 μm) and a characteristic substrate inhibition compared with the highly similar respiratory nitrate reductase NarGHI, which has a relatively much lower affinity for perchlorate (Km = 1.1 mm) and no substrate inhibition. Structural analysis of oxidized and reduced PcrAB with and without the substrate analog SeO3 (2-) bound to the active site identified key residues in the positively charged and funnel-shaped substrate access tunnel that gated substrate entrance and product release while trapping transiently produced chlorate. The structures suggest gating was associated with shifts of a Phe residue between open and closed conformations plus an Asp residue carboxylate shift between monodentate and bidentate coordination to the active site molybdenum atom. Taken together, structural and mutational analyses of gate residues suggest key roles of these gate residues for substrate entrance and product release. Our combined results provide the first detailed structural insight into the mechanism of biological perchlorate reduction, a critical component of the chlorine redox cycle on Earth. PMID:26940877

  6. Nitrate reductase gene involvement in hexachlorobiphenyl dechlorination by Phanerochaete chrysosporium

    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

  7. Cloning and sequence of the human adrenodoxin reductase gene

    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

  8. Characterization of a salt-induced DhAHP, a gene coding for alkyl hydroperoxide reductase, from the extremely halophilic yeast Debaryomyces hansenii

    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.

  9. Influence of extra-cellular and intra-cellular acting thiol oxidants on the 45calcium uptake by the islets of Langerhans of the rat

    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)

  10. Immunological comparison of the NADH:nitrate reductase from different cucumber tissues

    Jolanta Marciniak

    2014-02-01

    Full Text Available Soluble nitrate reductase from cucumber roots (Cucumis sativus L. was isolated and purified with blue-Sepharose 4B. Specific antibodies against the NR protein were raised by immunization of a goat. Using polyclonal antibodies anti-NR properties of the nitrate reductase from various cucumber tissues were examined. Experiments showed difference in immuno-logical properties of nitrate reductase (NR from cotyledon roots and leaves.

  11. Characterization and regulation of the gene encoding nitrite reductase in Rhodobacter sphaeroides 2.4.3.

    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....

  12. Enhanced dihydroflavonol-4-reductase activity and NAD homeostasis leading to cell death tolerance in transgenic rice

    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...

  13. Immunological comparison of the NADH:nitrate reductase from different cucumber tissues

    Jolanta Marciniak; Grażyna Kłobus; Józef Buczek; Tadeusz Stefaniak; Jarosław Mazur

    2014-01-01

    Soluble nitrate reductase from cucumber roots (Cucumis sativus L.) was isolated and purified with blue-Sepharose 4B. Specific antibodies against the NR protein were raised by immunization of a goat. Using polyclonal antibodies anti-NR properties of the nitrate reductase from various cucumber tissues were examined. Experiments showed difference in immuno-logical properties of nitrate reductase (NR) from cotyledon roots and leaves.

  14. Localization of the cytochrome cd1 and copper nitrite reductases in denitrifying bacteria.

    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...

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

    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 play, via photosynthesis, in the regulation of nitrate reductase gene expression. We show that sucrose...

  16. Structure of the Molybdenum Site of EEcherichia Coli Trimethylamine N-Oxide Reductase

    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. Synthesis and characterization of thiol-ene functionalized siloxanes and evaluation of their polymerization kinetics, network properties, and dental applications

    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.

  18. Protein Tyrosine Nitration and Thiol Oxidation by PeroxynitriteStrategies to Prevent These Oxidative Modifications

    Thomas Mnzel

    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.

  19. Advantages and drawbacks of Thiol-ene based resins for 3D-printing

    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.

  20. Quantification of Polyfunctional Thiols in Wine by HS-SPME-GC-MS Following Extractive Alkylation

    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.

  1. Activation of room temperature ferromagnetism in ZnO films by surface functionalization with thiol and amine

    Jayalakshmi, G.; Gopalakrishnan, N. [Thin Film Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli 620015 (India); Balasubramanian, T., E-mail: bala@nitt.edu [Thin Film Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli 620015 (India)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer Room temperature ferromagnetism (RTFM) is observed in surface functionalized ZnO films. Black-Right-Pointing-Pointer Surface functionalization is a new approach to make ZnO as ferromagnetic. Black-Right-Pointing-Pointer The RTFM is attributed to the interaction between the adsorbates and the surface of ZnO. Black-Right-Pointing-Pointer The oxygen vacancies are passivated upon surface functionalization. - Abstract: In this paper, we report the activation of room temperature ferromagnetism in ZnO films by surface functionalization with thiol and amine. The pure and surface functionalized ZnO films have been examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and vibrating sample magnetometer (VSM) measurements. XRD measurements show that all the films have single phase and (0 0 2) preferred orientation. The chemical bonding of ZnO with thiol and amine molecules has been confirmed by XPS measurements. The quenching of visible emission in PL spectra indicates that the surface defects are passivated by functionalization with thiol and amine. Surface functionalization of ZnO films with thiol and amine induces robust room temperature ferromagnetism in ZnO films as evidenced from VSM measurements. It is concluded that the observed ferromagnetic behavior in functionalized ZnO films is attributed to the different electronegativity of the atom in the thiol (or amine) and the surface of ZnO.

  2. Energy of the Lowest Unoccupied Molecular Orbital, Thiol Reactivity, and Toxicity of Three Monobrominated Water Disinfection Byproducts

    Pals, Justin A.; Wagner, Elizabeth D.; Plewa, Michael J.

    2016-01-01

    Disinfection of drinking water protects public health against waterborne pathogens. However, during disinfection, toxic disinfection byproducts (DBPs) are formed. Exposure to DBPs was associated with increased risk of bladder cancer in humans. DBPs are generated at concentrations below their carcinogenic potencies; it is unclear how exposure leads to adverse health outcomes. We used computational estimates of the energy of the lowest unoccupied molecular orbital (ELUMO) to predict thiol reactivity and additive toxicity among soft electrophile DBPs. Bromoacetic acid (BAA) was identified as non-thiol-reactive, which was supported by in chemico and in vitro data. Bromoacetonitrile (BAN) and bromoacetamide (BAM) were thiol-reactive. Genotoxicity induced by these compounds was reduced by increasing the thiol pool with N-acetyl l-cysteine (NAC), while NAC had little effect on BAA. BAN and BAM shared depletion of glutathione (GSH) or cellular thiols as a molecular initiating event (MIE), whereas BAA induces toxicity through another pathway. Binary mixtures of BAM and BAN expressed a potentiating effect in genotoxicity. We found that soft electrophile DBPs could be an important predictor of common mechanism groups that demonstrated additive toxicity. In silico estimates of ELUMO could be used to identify the most relevant DBPs that are the forcing factors of the toxicity of finished drinking waters. PMID:26854864

  3. Spectrofluorimetric determination of total free thiols based on formation of complexes of Ce(III) with disulfide bonds

    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%.

  4. Simultaneous determination of eight biologically active thiol compounds using gradient elution-liquid chromatography with Coul-Array detection.

    Petrlova, Jitka; Mikelova, Radka; Stejskal, Karel; Kleckerova, Andrea; Zitka, Ondrej; Petrek, Jiri; Havel, Ladislav; Zehnalek, Josef; Vojtech, Adam; Trnkova, Libuse; Kizek, Rene

    2006-05-01

    The most active form of sulfur in biomolecules is the thiol group, present in a number of biologically active compounds. Here we present a comprehensive study of thiol analysis using flow injection analysis/HPLC with electrochemical detection. The effect of different potentials of working electrodes, of organic solvent contents in the mobile phase, and of isocratic and gradient elution on simultaneous determination of thiol compounds (cysteine, cystine, N-acetylcysteine, homocysteine, reduced and oxidised glutathione, desglycinephytochelatin, and phytochelatins) are described and discussed. These thiol compounds were well separated and detected under optimised HPLC-electrochemical detection conditions (mobile phase: 80 mM trifluoroacetic acid and methanol with a gradient profile starting at 97:3 (TFA:methanol), kept constant for the first 8 min, then decreasing to 85:15 during one minute, kept constant for 8 min, and finally increasing linearly up to 97:3 from 17 to 18 min; the flow rate was 0.8 mL/min, column and detector temperature 25 degrees C, and the electrode potential 900 mV). We were able to determine tens of femtomoles (3 S/N) of the thiols per injection (5 microL), except for phytochelatin5 whose detection limit was 2.1 pmole. This technique was consequently used for simultaneous determination of compounds of interest in biological samples (maize tissue and human blood serum). PMID:16830732

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

    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...

  6. Thiol-based H2O2 signalling in microbial systems

    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.

  7. The reaction of Grignard reagents with Bunte salts: a thiol-free synthesis of sulfides.

    Reeves, Jonathan T; Camara, Kaddy; Han, Zhengxu S; Xu, Yibo; Lee, Heewon; Busacca, Carl A; Senanayake, Chris H

    2014-02-21

    S-Alkyl, S-aryl, and S-vinyl thiosulfate sodium salts (Bunte salts) react with Grignard reagents to give sulfides in good yields. The S-alkyl Bunte salts are prepared from odorless sodium thiosulfate by an SN2 reaction with alkyl halides. A Cu-catalyzed coupling of sodium thiosulfate with aryl and vinyl halides was developed to access S-aryl and S-vinyl Bunte salts. The reaction is amenable to a broad structural array of Bunte salts and Grignard reagents. Importantly, this route to sulfides avoids the use of malodorous thiol starting materials or byproducts. PMID:24512478

  8. Subcellular Localization of Thiol-Capped CdTe Quantum Dots in Living Cells

    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.

  9. X-ray absorption fine structure spectroscopy studies of thiol-capped copper nanoparticles

    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).

  10. Synthesis of novel thiol-functionalized mesoporous silica nanorods and their sorbent properties on heavy metals

    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.

  11. Surface Modification of Polydivinylbenzene Microspheres with a Fluorinated Glycopolymer Using Thiol-Halogen Click Chemistry.

    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

  12. Spectrophotometric determination of tungstate using an iron salt, a thiol and oxygen

    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)

  13. Biochemical Characterization of a Thiol-Activated, Oxidation Stable Keratinase from Bacillus pumilus KS12

    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 β-mercaptoethanol, respectively. In addition, its activity was stimulated in the presence of various surfactants,...

  14. Characterization of thiol-functionalised silica films deposited on electrode surfaces

    Ivana, Cesarino; der 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).

  15. X-ray absorption fine structure spectroscopy studies of thiol-capped copper nanoparticles

    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).

  16. Characterization of thiol-functionalised silica films deposited on electrode surfaces

    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.

  17. biliverdin. Is there a role for biliverdin reductase?

    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.

  18. Methylenetetrahydrofolate Reductase C677T: Hypoplastic Left Heart and Thrombosis.

    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

  19. Tioredoxin reductase a new target for molecular medical investigations

    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.

  20. Terpenoids from Diplophyllum taxifolium with quinone reductase-inducing activity.

    Wang, Xiao; Zhang, Jiao-Zhen; Zhou, Jin-Chuan; Shen, Tao; Lou, Hong-Xiang

    2016-03-01

    Two new ent-prenylaromadendrane-type diterpenoids, diplotaxifols A (1) and B (2), a new ent-eudesmol, ent-eudesma-4(15),11(13)-dien-6α,12-diol (3), eight new eudesmanolides enantiomers (4-11) of the corresponding compounds from higher plants along with four known ent-eudesmanolides (12-15) were isolated from the 95% EtOH extract of Chinese liverwort Diplophyllum taxifolium. Their structures were elucidated on the basis of MS, NMR and IR spectral data, and confirmed by single-crystal X-ray diffraction analysis. The quinone reductase-inducing activity of the compounds was evaluated. PMID:26656409

  1. Methylenetetrahydrofolate reductase (MTHFR) deficiency presenting as a rash.

    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.

  2. CdS quantum dots for measurement of the size-dependent optical properties of thiol capping

    The optical- and size-dependent properties of CdS quantum dots (QDs) were analyzed in the presence and absence of different capping agents in aqueous medium. The QDs have been characterized by UV–Vis, Photoluminescence, Fourier-transform infrared spectroscopy, X-ray diffraction, and Fluorescence lifetime measurements. QDs with the presence of thiol group in cubic phase with small grain size were observed in XRD and decrease in particle size of the same with increase in band gap is deduced through UV–Vis and XRD studies. The FT-IR spectrum confirms the interaction of thiol group with CdS. Fluorescence lifetime of capped QDs was higher compared to uncapped CdS QDs. The surface passivation of thiol group on CdS is shown in photoluminescence studies.Graphical Abstract

  3. Relationship of non-protein thiol pools and accumulated Cd or Hg in the marine macrophyte Posidonia oceanica (L.) Delile

    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.

  4. Chitosan scaffold modified with D-(+) raffinose and enriched with thiol-modified gelatin for improved osteoblast adhesion.

    Galli, C; Parisi, L; Elviri, L; Bianchera, A; Smerieri, A; Lagonegro, P; Lumetti, S; Manfredi, E; Bettini, R; Macaluso, G M

    2016-02-01

    The aim of the present study was to investigate whether chitosan-based scaffolds modified with D-(+) raffinose and enriched with thiol-modified gelatin could selectively improve osteoblast adhesion and proliferation. 2, 3 and 4.5% chitosan films were prepared. Chitosan suitability for tissue engineering was confirmed by protein adsorption assay. Scaffolds were incubated with a 2.5 mg ml(-1) BSA solution and the decrease of protein content in the supernatants was measured by spectrophotometry. Chitosan films were then enriched with thiol-modified gelatin and their ability to bind BSA was also measured. Then, 2% chitosan discs with or without thiol-modified gelatin were used as culture substrates for MC3T3-E1 cells. After 72 h cells were stained with trypan blue or with calcein AM and propidium iodide for morphology, viability and proliferation assays. Moreover, cell viability was measured at 48, 72, 96 and 168 h to obtain a growth curve. Chitosan films efficiently bound and retained BSA proportionally to the concentration of chitosan discs. The amount of protein retained was higher on chitosan enriched with thiol-modified gelatin. Moreover, chitosan discs allowed the adhesion and the viability of cells, but inhibited their proliferation. The functionalization of chitosan with thiol-modified gelatin enhanced cell spreading and proliferation. Our data confirm that chitosan is a suitable material for tissue engineering. Moreover, our data show that the enrichment of chitosan with thiol-modified gelatin enhances its biological properties. PMID:26836318

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

    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

  6. Facile Fabrication of Polymerizable Ionic Liquid Based-Gel Beads via Thiol-ene Chemistry.

    Taghavikish, Mona; Subianto, Surya; Dutta, Naba Kumar; Choudhury, Namita Roy

    2015-08-12

    Multipurpose gel beads prepared from natural or synthetic polymers have received significant attention in various applications such as drug delivery, coatings, and electrolytes because of their versatility and unique performance as micro- and nanocontainers.1 However, comparatively little work has been done on poly(ionic liquid)-based materials despite their unique ionic characteristics. Thus, in this contribution we report the facile preparation of polymerizable ionic liquid-based gel beads using thiol-ene click chemistry. This novel system incorporates pentaerythritol tetra (3-mercaptopropionate) (PETKMP) and 1,4-di(vinylimidazolium) butane bisbromide in a thiol-ene-based photopolymerization to fabricate the gel beads. Their chemical structure, thermal and mechanical properties have been investigated using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The gel beads possess low Tg and their ionic functionalities attribute self-healing properties and their ability to uptake small molecules or organic compounds offers their potential use as pH sensing material and macrocontainers. PMID:26171715

  7. Reaction of [3H]-taurine maleimide with platelet surface thiols

    Taurine Maleimide (2-maleimidoethanesulfonate, TM) was synthesized from [2-3H]-taurine and methoxycarbonylmaleimide (MCM). The yield of a 1 μmol synthesis approached 100% (based on taurine) when MCM was used in 4-fold excess. The product (TM*) was purified by ion exchange chromatography. TM* reacted irreversibly with thiol groups on the surface of washed human platelets, leading to incorporation of radioactivity into platelet pellets. Incorporation was blocked by cysteine, mercuribenzenesulfonate (MBS), dithiobisnitrobenzoate, and N-ethylmaleimide, but not by taurine or by inhibitors of anion transport. Reaction of TM* with platelets showed the dependence on time and concentration characteristics of a bimolecular reaction. The number of reactive sites ranged from 1 to 5 x 105/platelet, and the apparent rate constant from 1 to 3 x 103/(M x min). TM was less effective than MBS as an inhibitor of platelet aggregation induced by several agents. TM had no effect on the uptake of serotonin, taurine, or phosphate by the platelets, processes which are sensitive to MBS. These differences, considered with the similarity in size and charge of TM and MBS, suggest that classes of thiols defined as exofacial by their accessibility to MBS can differ substantially in their reactivity with other impermeant reagents

  8. Transcriptional activation by heat and cold of a thiol protease gene in tomato. [Lycopersicon esculentum

    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.

  9. Mixing thiols on the surface of silver nanoparticles: preserving antibacterial properties while introducing SERS activity

    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 7nm 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

  10. Adsorption Behavior of Thiols on Metal surfaces; A Density Functional Theory Study

    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(42) structure model is preferred over (33)R30^rc.

  11. Thiol peroxidase-like activity of some intramolecularly coordinated diorganyl diselenides

    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. Novel technological strategies to enhance tropical thiol precursors in winemaking by-products.

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

    2016-09-15

    Grape pomace is a winemaking by-product that can be used to extract oenological tannins. Recently, some grape skin tannins were shown to contain very high amounts of two polyfunctional thiol precursors (3-S-glutathionylhexan-1-ol, 3-S-cysteinylhexan-1-ol) whose free forms are responsible for appreciated tropical-like flavours. This study shows that an oxidative treatment (no SO2) of white grape pomace and the presence of grape leaves and stems can increase the content of the above mentioned precursors. Moreover, it shows significant differences between Sauvignon Blanc, Gewuerztraminer and Mueller-Thurgau grape pomace for the 3-mercaptohexan-1-ol precursors and 4-S-cysteinyl-4-methylpentan-2-one. The grape cultivar is crucial, but the technological ability of enhancing the level of the volatile thiol precursors simply by treating the grape marc in different ways is a promising and powerful tool for the production of potentially flavouring tannins intended for food and beverage industry. PMID:27080874

  13. Surface modification of silicate glass using 3-(mercaptopropyl)trimethoxysilane for thiol-ene polymerization.

    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

  14. Thiol-modified gold nanoparticles deposited on silica support using dip coating

    Graphical abstract: - Highlights: • Thin layers of gold were deposited on glass substrate. • Layers were modified by two different ligands, 1,4-dithiothreitol and L-glutathione. • Red shift of SPR band was observed in spectra after modification of Au by thiols. • Charge transfer between Au and S atoms leads to ferromagnetic behaviour of samples. - Abstract: In our work, we have prepared thin layers of gold nanoparticles deposited via dip coating technique on silica glass substrate. The prepared thin layers were modified by two different ligands, namely 1,4-dithiothreitol (sample Au-DTT NPs) and L-glutathione (sample Au-GSH NPs). The spectral, structural and magnetic properties of the prepared samples were investigated. The modification of Au nanoparticles with thiol ligands leads to change of their plasmon resonance fields, as indicated by UV–vis spectra. The magnetic measurements showed that the magnetization of the samples is composed from two magnetic contributions: diamagnetic contribution and low field ferromagnetic contribution. Our experimental results show that the charge transfer between Au and S atoms gives rise to the ferromagnetic behaviour of prepared thin layers

  15. Adsorption characteristics of self-assembled thiol and dithiol layer on gold

    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

  16. Altered Thiol Chemistry in Human Amyotrophic Lateral Sclerosis-linked Mutants of Superoxide Dismutase 1*

    Solsona, Carles; Kahn, Thomas B.; Badilla, Carmen L.; Álvarez-Zaldiernas, Cristina; Blasi, Juan; Fernandez, Julio M.; Alegre-Cebollada, Jorge

    2014-01-01

    Neurodegenerative diseases share a common characteristic, the presence of intracellular or extracellular deposits of protein aggregates in nervous tissues. Amyotrophic Lateral Sclerosis (ALS) is a severe and fatal neurodegenerative disorder, which affects preferentially motoneurons. Changes in the redox state of superoxide dismutase 1 (SOD1) are associated with the onset and development of familial forms of ALS. In human SOD1 (hSOD1), a conserved disulfide bond and two free cysteine residues can engage in anomalous thiol/disulfide exchange resulting in non-native disulfides, a hallmark of ALS that is related to protein misfolding and aggregation. Because of the many competing reaction pathways, traditional bulk techniques fall short at quantifying individual thiol/disulfide exchange reactions. Here, we adapt recently developed single-bond chemistry techniques to study individual disulfide isomerization reactions in hSOD1. Mechanical unfolding of hSOD1 leads to the formation of a polypeptide loop held by the disulfide. This loop behaves as a molecular jump rope that brings reactive Cys-111 close to the disulfide. Using force-clamp spectroscopy, we monitor nucleophilic attack of Cys-111 at either sulfur of the disulfide and determine the selectivity of the reaction. Disease-causing mutations G93A and A4V show greatly altered reactivity patterns, which may contribute to the progression of familial ALS. PMID:25096579

  17. Altered thiol chemistry in human amyotrophic lateral sclerosis-linked mutants of superoxide dismutase 1.

    Solsona, Carles; Kahn, Thomas B; Badilla, Carmen L; Álvarez-Zaldiernas, Cristina; Blasi, Juan; Fernandez, Julio M; Alegre-Cebollada, Jorge

    2014-09-26

    Neurodegenerative diseases share a common characteristic, the presence of intracellular or extracellular deposits of protein aggregates in nervous tissues. Amyotrophic Lateral Sclerosis (ALS) is a severe and fatal neurodegenerative disorder, which affects preferentially motoneurons. Changes in the redox state of superoxide dismutase 1 (SOD1) are associated with the onset and development of familial forms of ALS. In human SOD1 (hSOD1), a conserved disulfide bond and two free cysteine residues can engage in anomalous thiol/disulfide exchange resulting in non-native disulfides, a hallmark of ALS that is related to protein misfolding and aggregation. Because of the many competing reaction pathways, traditional bulk techniques fall short at quantifying individual thiol/disulfide exchange reactions. Here, we adapt recently developed single-bond chemistry techniques to study individual disulfide isomerization reactions in hSOD1. Mechanical unfolding of hSOD1 leads to the formation of a polypeptide loop held by the disulfide. This loop behaves as a molecular jump rope that brings reactive Cys-111 close to the disulfide. Using force-clamp spectroscopy, we monitor nucleophilic attack of Cys-111 at either sulfur of the disulfide and determine the selectivity of the reaction. Disease-causing mutations G93A and A4V show greatly altered reactivity patterns, which may contribute to the progression of familial ALS. PMID:25096579

  18. Thiol-Functionalized Gold-Nanoscale Organic Hybrid Materials-Attractive to Soft glasses

    Agrawal, Akanksha; Archer, Lynden

    2014-03-01

    We report on the flow properties of self-suspended nanoparticles based on gold nanoparticles densely grafted with polyethylene glycol methyl ether thiol(PEG) chains. We studied the effect of temperature, olume fraction and polymer chain length on the transition from attractive glass to soft glassy flow behavior. Gold nanoparticles densely grafted with short PEG-thiol chains(MW 800,2kDa and 6kDa)are shown to form self-suspended systems over a range of polymer grafting densities and particle volume fractions, φ.Transmission electron and atomic force microscopy measurements reveal that the particles are uniformly dispersed. Oscillatory shear measurements performed on low φ systems show a two-step yielding behavior reflecting bond breaking and cage breaking transitions at the nanoscale; both characteristics of soft glassy materials dominated by attractive forces. With increased temperature a transition to one-step yielding and subsequently back to two-step yielding is observed. At high φ a single yielding transition and soft glassy flow behavior are observed. We employ SAXS, vibration spectroscopy, thermal analysis, and rheology to interrogate the configuration state of the tethered chains and particle-particle interactions in detail. King Abdullah Univeristy of Science and Technology (KAUST), National Science Foundation, Cornell Center for Materials Research (CCMR), Advance Photon Source at Argonne National Lab.

  19. Effects of polyamines and thiols on the radiation sensitivity of bacterial transforming DNA

    The effects of polyamines on the loss of biological activity of bacterial transforming DNA irradiated in the absence and presence of sulphydryl-containing compounds has been investigated. When O2-saturated DNA solutions are irradiated, the degree of radioprotection by polyamines generally correlates with the efficiency of scavenging of OH· radicals. In N2 the protection does not show that correlation; several possible reasons are discussed. With the exception of spermine, the polyamines are slightly more protective of oxygenated DNA than of hypoxic DNA. When DNA is irradiated in the presence of both polyamines and thiols, the combined protection is usually greater than that exhibited by either agent alone. When irradiation is in oxygen, the combined agents appear to operate by the same mechanism, namely OH· radical scavenging. In N2-saturated solutions, polyamines and dithiothreitol appear to act by different, non-interactive mechanisms; however WR1065 and polyamines may radioprotect by the same mechanism. The results suggest that polyamines may reduce the ability of some thiols to radioprotect DNA. (author)

  20. Biostability enhancement of oil core - polysaccharide multilayer shell via photoinitiator free thiol-ene 'click' reaction.

    Calcagno, Vincenzo; Vecchione, Raffaele; Sagliano, Angela; Carella, Antonio; Guarnieri, Daniela; Belli, Valentina; Raiola, Luca; Roviello, Antonio; Netti, Paolo A

    2016-06-01

    Layer-by-layer of polyelectrolytes has emerged as one of the easiest and most controlled techniques to deposit ultrathin polymer layers mainly driven by electrostatic interactions. However, this kind of interaction results to be weak and easily breakable in physiological environment. Here we report on the preparation of nanocapsules completely made of natural biomaterials: a lipophilic core (soybean oil and egg lecithin as surfactant) as nanometric template and a polysaccharide-based multilayer shell (glycol chitosan and heparin) covalently cross-linked. We first modified glycol chitosan with a thiol moiety and heparin with an alkene moiety, respectively, and then we built a polymer multilayer film with a covalent cross-linkage among layers, exploiting the light initiated thiol-ene reaction, known as click chemistry. We showed the possibility to perform the covalent cross-linkage without any photoinitiator or metal catalyst, thus avoiding cytotoxic effects and further purification steps. The so realized nanocapsules resulted to be stable and completely biocompatible and, therefore, of interest for the biotechnology fields, mainly for drug delivery. PMID:26962765

  1. Thermal stabilization and plasticization of poly(vinyl chloride) by ester thiols: Update and current status

    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

  2. Thiol-modified gold nanoparticles deposited on silica support using dip coating

    Magura, Jozef [Department of Inorganic Chemistry, Faculty of Science, P.J. Šafárik University, Moyzesova 11, SK-041 54 Košice (Slovakia); Zeleňáková, Adriana [Department of Condensed Matter Physics, Faculty of Science, P.J. Šafárik University, Park Angelinum 9, 041 54 Košice (Slovakia); Zeleňák, Vladimír, E-mail: vladimir.zelenak@upjs.sk [Department of Inorganic Chemistry, Faculty of Science, P.J. Šafárik University, Moyzesova 11, SK-041 54 Košice (Slovakia); Kaňuchová, Maria [Institute of Montaneous Sciences and Environmental Protection, Technical University of Košice, Park Komenského 19, 043 84 Košice (Slovakia)

    2014-10-01

    Graphical abstract: - Highlights: • Thin layers of gold were deposited on glass substrate. • Layers were modified by two different ligands, 1,4-dithiothreitol and L-glutathione. • Red shift of SPR band was observed in spectra after modification of Au by thiols. • Charge transfer between Au and S atoms leads to ferromagnetic behaviour of samples. - Abstract: In our work, we have prepared thin layers of gold nanoparticles deposited via dip coating technique on silica glass substrate. The prepared thin layers were modified by two different ligands, namely 1,4-dithiothreitol (sample Au-DTT NPs) and L-glutathione (sample Au-GSH NPs). The spectral, structural and magnetic properties of the prepared samples were investigated. The modification of Au nanoparticles with thiol ligands leads to change of their plasmon resonance fields, as indicated by UV–vis spectra. The magnetic measurements showed that the magnetization of the samples is composed from two magnetic contributions: diamagnetic contribution and low field ferromagnetic contribution. Our experimental results show that the charge transfer between Au and S atoms gives rise to the ferromagnetic behaviour of prepared thin layers.

  3. A novel twist on molecular interactions between thioredoxin and nicotinamide adenine dinucleotide phosphate-dependent thioredoxin reductase

    Kirkensgaard, Kristine Groth; Hägglund, Per; Shahpiri, Azar; Finnie, Christine; Henriksen, Anette; Svensson, Birte

    2013-01-01

    The ubiquitous disulfide reductase thioredoxin (Trx) regulates several important biological processes such as seed germination in plants. Oxidized cytosolic Trx is regenerated by nicotinamide adenine dinucleotide phosphate (NADPH)-dependent thioredoxin reductase (NTR) in a multistep transfer of r...

  4. Determination of the specific activities of methionine sulfoxide reductase A and B by capillary electrophoresis

    A capillary electrophoresis (CE) method for the determination of methionine sulfoxide reductase A and methionine sulfoxide reductase B activities in mouse liver is described. The method is based on detection of the 4-(dimethylamino)azobenzene-4’-sulfonyl derivative of L-methionine (dabsyl Met), the ...

  5. Maleylacetate reductases in chloroaromatic-degrading bacteria using the modified ortho pathway: comparison of catalytic properties.

    Müller, D.; Schlömann, M; Reineke, W.

    1996-01-01

    The maleylacetate reductases from Pseudomonas aeruginosa RHO1 and Alcaligenes eutrophus JMP134 were tested for activity and affinity to various maleylacetates as well as dechlorinating properties. The dechlorinating activity and the kcat/Km values revealed high-level similarity of these reductases to that of Pseudomonas sp. strain B13.

  6. Acute changes in intracellular ions or pH and regulation of aldose reductase activity.

    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

  7. Evaluation of 5?-reductase inhibitory activity of certain herbs useful as antiandrogens.

    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

  8. Transcription factors involved in controlling the expression of nitrate reductase genes in higher plants.

    Yanagisawa, Shuichi

    2014-12-01

    Nitrate reductase is a key enzyme in nitrogen assimilation, and it catalyzes the nitrate-to-nitrite reduction process in plants. A variety of factors, including nitrate, light, metabolites, phytohormones, low temperature, and drought, modulate the expression levels of nitrate reductase genes as well as nitrate reductase activity, which is consistent with its physiological role. Recently, several transcription factors involved in controlling the expression of nitrate reductase genes have been identified in Arabidopsis. NODULE-INCEPTION-like proteins (NLPs) are transcription factors responsible for nitrate-inducible expression of nitrate reductase genes. Since NLPs also control nitrate-inducible expression of genes encoding nitrate transporter, nitrite transporter, and nitrite reductase, the expression levels of nitrate reduction pathway-associated genes are coordinately modulated by NLPs in response to nitrate. LATERAL ORGAN BOUNDARIES DOMAIN (LBD) transcription factors (LBD37-LBD39) are strong candidates for transcription factors mediating negative feedback regulation in response to increases in the contents of nitrogen-containing metabolites, whereas LONG HYPOCOTYL 5 (HY5) that promotes photomorphogenesis in light may be a transcription factor involved in light-induced expression of a nitrate reductase gene. Furthermore, unidentified transcription factors likely mediate other signals and regulate the expression of nitrate reductase genes. This review presents a summary of our current knowledge of such transcription factors. PMID:25443843

  9. Functions of Flavin Reductase and Quinone Reductase in 2,4,6-Trichlorophenol Degradation by Cupriavidus necator JMP134▿

    Belchik, Sara Mae; XUN, Luying

    2007-01-01

    The tcpRXABCYD operon of Cupriavidus necator JMP134 is involved in the degradation of 2,4,6-trichlorophenol (2,4,6-TCP), a toxic pollutant. TcpA is a reduced flavin adenine dinucleotide (FADH2)-dependent monooxygenase that converts 2,4,6-TCP to 6-chlorohydroxyquinone. It has been implied via genetic analysis that TcpX acts as an FAD reductase to supply TcpA with FADH2, whereas the function of TcpB in 2,4,6-TCP degradation is still unclear. In order to provide direct biochemical evidence for t...

  10. The antioxidant protein alkylhydroperoxide reductase of Helicobacter pylori switches from a peroxide reductase to a molecular chaperone function

    Chuang, Ming-Hong; Wu, Ming-Shiang; Lo, Wan-Lin; Lin, Jaw-Town; Wong, Chi-Huey; Chiou, Shyh-Horng

    2006-01-01

    Helicobacter pylori, an oxygen-sensitive microaerophilic bacterium, contains many antioxidant proteins, among which alkylhydroperoxide reductase (AhpC) is the most abundant. The function of AhpC is to protect H. pylori from a hyperoxidative environment by reduction of toxic organic hydroperoxides. We have found that the sequence of AhpC from H. pylori is more homologous to mammalian peroxiredoxins than to eubacterial AhpC. We have also found that the protein structure of AhpC could shift from...

  11. Mitochondrial thiol oxidase Erv1: both shuttle cysteine residues are required for its function with distinct roles

    Ang, SweeKim; 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 Cys30Cys33 shuttle disulfide. However, it is unclear ho...

  12. A novel fluorogenic probe for the investigation of free thiols: Application to kinetic measurements of acetylcholinesterase activity.

    Mertens, Matthias D; Bierwisch, Anne; Li, Tianwei; Gtschow, 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

  13. The effect of ionic and non-ionic surfactants on the growth, nitrate reductase and nitrite reductase activities of Spirodela polyrrhiza (L. Schleiden

    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.

  14. Crystallization and preliminary characterization of dihydropteridine reductase from Dictyostelium discoideum

    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, β = 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. Nitrate metabolism in tobacco leaves overexpressing Arabidopsis nitrite reductase.

    Davenport, Susie; Le Lay, Pascaline; Sanchez-Tamburrrino, Juan Pablo

    2015-12-01

    Primary nitrogen assimilation in plants includes the reduction of nitrite to ammonium in the chloroplasts by the enzyme nitrite reductase (NiR EC:1.7.7.1) or in the plastids of non-photosynthetic organs. Here we report on a study overexpressing the Arabidopsis thaliana NiR (AtNiR) gene in tobacco plants under the control of a constitutive promoter (CERV - Carnation Etched Ring Virus). The aim was to overexpress AtNiR in an attempt to alter the level of residual nitrite in the leaf which can act as precursor to the formation of nitrosamines. The impact of increasing the activity of AtNiR produced an increase in leaf protein and a stay-green phenotype in the primary transformed AtNiR population. Investigation of the T1 homozygous population demonstrated elevated nitrate reductase (NR) activity, reductions in leaf nitrite and nitrate and the amino acids proline, glutamine and glutamate. Chlorophyl content of the transgenic lines was increased, as evidenced by the stay-green phenotype. This reveals the importance of NiR in primary nitrogen assimilation and how modification of this key enzyme affects both the nitrogen and carbon metabolism of tobacco plants. PMID:26447683

  16. Hydroxymethylglutaryl-coenzyme A reductase-containing hepatocytes are distributed periportally in normal and mevinolin-treated rat livers.

    Singer, I. I.; Kawka, D. W.; Kazazis, D M; Alberts, A W; Chen, J. S.; Huff, J W; Ness, G C

    1984-01-01

    Mevinolin is a potent inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase; EC 1.1.1.34), an enzyme that catalyzes the rate-limiting step in cholesterol biosynthesis. We have been studying the hepatic distribution of reductase with immunofluorescence microscopy and liver ultrastructure with electron microscopy in normal and drug-treated rats. In control animals, only about 20% of the hepatocytes were reductase positive. These cells were localized in the periportal l...

  17. The effect of NaCl intake on 9-ketoprostaglandin reductase activity in the rabbit kidney.

    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

  18. Product-mediated regulation reveals the polymorphic nature of the yeast assimilatory nitrate reductase.

    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

  19. Trypanothione Reductase: A Viable Chemotherapeutic Target for Antitrypanosomal and Antileishmanial Drug Design

    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. Ligand effects on the stability of thiol-stabilized gold nanoclusters: Au25(SR)18-, Au38(SR)24, and Au102(SR)44

    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

  1. Immunological identification and distribution of dissimilatory heme cd1 and nonheme copper nitrite reductases in denitrifying bacteria.

    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...

  2. Vibrio harveyi Nitroreductase Is Also a Chromate Reductase

    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 DH5α 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 DH5α NfsA (GST-EcNfsA), a fusion between GST and E. coli DH5α NfsB (GST-EcNfsB), and a fusion between GST and V. harveyi KCTC 2720 NfsA (GST-VhNfsA) were prepared for their overproduction and easy purification. GST-EcNfsA, GST-EcNFsB, and GST-VhNFsA efficiently reduced nitrofurazone and 2,4,6-trinitrotoluene (TNT) as their nitro substrates. The Km values for GST-EcNfsA, GST-EcNfsB, and GST-VhNfsA for chromate reduction were 11.8, 23.5, and 5.4 μM, respectively. The Vmax values for GST-EcNfsA, GST-EcNfsB, and GST-VhNfsA were 3.8, 3.9, and 10.7 nmol/min/mg of protein, respectively. GST-VhNfsA was the most effective of the three chromate reductases, as determined by each Vmax/Km value. The optimal temperatures of GST-EcNfsA, GST-EcNfsB, and GST-VhNfsA for chromate reduction were 55, 30, and 30°C, respectively. Thus, it is confirmed that nitroreductase can also act as a chromate reductase. Nitroreductases may be used in chromate remediation. GST-EcNfsA, GST-EcNfsB, and GST-VhNfsA have a molecular mass of 50 kDa and exist as a monomer in solution. Thin-layer chromatography showed that GST-EcNfsA, GST-EcNfsB, and GST-VhNfsA contain FMN as a cofactor. GST-VhNfsA reduced Cr(VI) to Cr(III). Cr(III) was much less toxic to E. coli than Cr(VI). PMID:12902220

  3. Ultrasound-Accelerated Synthesis of Asymmetrical Thiosulfonate S-Esters by Base-Promoted Reaction of Sulfonyl Chlorides with Thiols

    Pham, Hien Thi; Nguyen, Ngoc-Lan Thi; Duus, Fritz; Luu, Thi Xuan Thi

    2015-01-01

    Amberlyst A-26, Mg-Al hydrotalcite, potassium fluoride absorbed on alumina, triethylamine and pyridine have been tested as base catalysts and reagents for the reaction of sulfonyl chlorides with thiols to prepare thiosulfonate S-esters. The reactions were performed under solvent-free conditions or...

  4. A Route to Aliphatic Poly(ester)s with Thiol Pendant Groups: From Monomer Design to Editable Porous Scaffolds.

    Fuoco, Tiziana; Finne-Wistrand, Anna; Pappalardo, Daniela

    2016-04-11

    Biodegradable aliphatic polyesters such as poly(lactide) and poly(ε-caprolactone), largely used in tissue engineering applications, lack suitable functional groups and biological cues to enable interactions with cells. Because of the ubiquity of thiol groups in the biological environment and the pliability of thiol chemistry, we aimed to design and synthesize poly(ester) chains bearing pendant thiol-protected groups. To achieve this, 3-methyl-6-(tritylthiomethyl)-1,4-dioxane-2,5-dione, a lactide-type monomer possessing a pendant thiol-protected group, was synthesized. This molecule, when used as a monomer in controlled ring-opening polymerization in combination with lactide and ε-caprolactone, appeared to be a convenient "building block" for the preparation of functionalized aliphatic copolyesters, which were easily modified further. A polymeric sample bearing pyridyl disulfide groups, able to bind a cysteine-containing peptide, was efficiently obtained from a two-step modification reaction. Porous scaffolds were then prepared by blending this latter copolymer sample with poly(l-lactide-co-ε-caprolactone) followed by salt leaching. A further disulfide exchange reaction performed in aqueous medium formed porous scaffolds with covalently linked arginine-glycine-aspartic acid sequences. The scaffolds were characterized by thermal and mechanical tests, and scanning electron microscopy surface images revealed a highly porous morphology. Moreover, a cytotoxicity test indicated good cell viability. PMID:26915640

  5. Quantification of protein thiols and dithiols in the picomolar range using sodium borohydride and 4,4'-dithiodipyridine

    Hansen, Rosa E; Østergaard, Henrik; Nørgaard, Per; Winther, Jakob R

    2007-01-01

    sodium borohydride and the thiol reagent 4,4'-dithiodipyridine (4-DPS). Because borohydride is efficiently destroyed by the addition of acid, the complete reduction and quantification can be performed conveniently in one tube without desalting steps. Furthermore, the use of reverse-phase high...

  6. Low molecular mass thiols, disulfides and protein mixed disulfides in rat tissues: influence of sample manipulation, oxidative stress and ageing.

    Giustarini D; Dalle-Donne I; Milzani A; Rossi R

    2011-04-01

    Most of the data in studies investigating the contribution of oxidative stress to some human diseases and to ageing derive from measurements carried out in blood, on the basis of the assumption that any alteration of the hematic thiol/disulfide balance should reflect a corresponding alteration in other less accessible tissues. But it is evident that the information that can be gleaned from a direct analysis in specific tissues is largely greater. Nevertheless, the accurate measurement of disulfides is frequently hampered by the artifactual oxidation occurring during sample manipulation as a consequence of the presence of heme-proteins. Therefore, the levels of disulfide forms of low molecular mass thiols in tissues are still poorly investigated, even if their measurements could represent a powerful index of the oxidative status. Here we have used an artifact-free procedure to measure low molecular mass thiols and their disulfides in different rat tissues. Our findings suggest that disulfides are a reliable biomarker of even slight oxidative damage. In tissues of aged rats we observed that either oxidative stress or glutathione depletion alone can occur in different tissues during ageing. Interestingly, among the investigated thiols, only homocysteine showed a tendency to increase in some organs with ageing.

  7. DEPLETION OF CELLULAR PROTEIN THIOLS AS AN INDICATOR OF ARYLATION IN ISOLATED TROUT HEPATOCYTES EXPOSED TO 1,4-BENZOQUINONE

    A method for the measurement of protein thiols (PrSH), un-reacted as well as oxidized, i.e. dithiothreitol recoverable, was adapted for the determination of PrSH depletion in isolated rainbow trout hepatocytes exposed to an arylating agent, 1,4-benzoquinone (BQ). Toxicant analysi...

  8. Removal of lead(II ions from aqueous solutions using cashew nut shell liquid-templated thiol-silica materials

    J. E. G. Mdoe

    2014-09-01

    Full Text Available A range of thiol-silica composites were prepared using cashew nut shell liquid (CNSL or one of its phenolic constituents, cardanol, as templates. The procedure involved formation of a CNSL or cardanol emulsion in a water-ethanol system into which (3-mercaptopropyl-trimethoxysilane and tetraethyl orthosilicate were simultaneously added at various ratios. The reaction mixture was aged at room temperature for 18 h followed by a Soxhlet extraction of the template and drying. The materials were characterized by diffuse reflectance Fourier transform infrared, nitrogen physisorption, scanning electron microscopy and acid titration. Results indicated that indeed the thiol-silica composites were successfully prepared, with thiol group loadings ranging from 1.6-2.5 mmol/g. The materials were tested for lead(II adsorption, and results showed that they had maximum adsorption capacities up to 66.7 mg/g, depending on the thiol group loading and type of template used in preparing the adsorbent. DOI: http://dx.doi.org/10.4314/bcse.v28i3.5

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

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

    2015-01-01

    Reaction of (R,S)-α-terpineol with thioacetic acid in food-grade n-hexane resulted into two α-terpineol thioacetate derivatives with the same molecular weight. After 5 h of reaction time, (R,S)-α-terpineol was completely transformed and the mixture analysed by different chromatographic techniques. The aroma character of the α-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 α-terpineol thioacetates into the corresponding α-terpineol thiols. When reactions were performed in 0.2 m phosphate buffer at pH 8.0 and 30 °C with non-immobilized PLE, α-terpineol thiols were produced in an optimal yield of 88% after 24 h of reaction time. The aroma character of α-terpineol thiols was described as green, exotic and fresh grapefruit. Flavouring powders were prepared by freeze-drying the α-terpineol thioacetates and α-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

  10. Adsorption kinetics and mechanical properties of thiol-modified DNA-oligos on gold investigated by microcantilever sensors

    Marie, Rodolphe Charly Willy; Jensenius, Henriette; Thaysen, Jacob; Christensen, Claus Bo Vöge; Boisen, Anja

    adsorption depends on the concentration of the oligo solution. Based on the calculated rate constants a surface free energy of the thiol-modified DNA-oligo adsorption on gold is found to be -32.4 kJ mol(-1). The adsorption experiments also indicate that first a single layer of DNA-oligos is assembled on the...

  11. In situ generated hypoiodous acid in an efficient and heterogeneous catalytic system for the homo-oxidative coupling of thiols

    Ghorbani-Choghamarani Arash

    2013-01-01

    Full Text Available Supported hydrogen peroxide on polyvinylpolypyrrolidone (PVPH2O2, silica sulfuric acid (SiO2-OSO3H and catalytic amounts of potassium iodide (KI has been developed as a heterogeneous medium for the rapid oxidative coupling of thiols into symmetrical homodisulfides. This oxidizing system proceeds under extremely mild conditions and gives no other oxidized side products.

  12. A contact angle and ToF-SIMS study of SAM-thiol interactions on polycrystalline gold

    Tencer, Michal; Nie, Heng-Yong; Berini, Pierre

    2011-02-01

    A process of chemical differentiation of neighboring Au features on a substrate (for biosensing applications) involves a step, where after electrochemical removal of a self-assembled monolayer (SAM) from one feature, another SAM is deposited onto it by incubation with a different thiol. During this incubation step, other undesorbed features are also exposed to this thiol which may lead to a partial SAM-thiol exhange, the extent of which is a function of time. Here, such surface reactions were followed on polystalline Au in both directions using contact angle measurements and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The thiols involved were dodecanethiol (DDT) which forms SAM promoting adsorption of proteins and 11-mercaptoundecyl)tri(ethylene glycol) (TPEG) whose SAM prevents such adsorption. The surface reactions in both directions cannot be described by a simple pseudo-first-order kinetics. It was found that while the DDT SAM interaction with a TPEG solution leads eventually to a total replacement, the reverse process, TPEG SAM interaction with DDT, leads to no noticeable exchange over the first 3 h and then asymptotically approaches ∼50% replacement.

  13. 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

    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.

  14. An Improved Isotope Coded Affinity Tag Technology for Thiol Redox Proteomics

    Ning Zhu

    2012-01-01

    Full Text Available Isotope Coded Affinity Tag (ICAT is a gel-free technology for quantitative proteomics. In ICAT procedure, strong cation exchange chromatography (SCX using increased potassium chloride gradient is recommended for peptide fractionation. Here we report optimization of hydrophilic interaction chromatography (HILIC as an alternative strategy for peptide fractionation of ICAT samples. HILIC exhibits high separation efficiency and does not require any downstream desalting steps. Compared to SCX based ICAT, integration of HILIC into the ICAT technology has resulted in high rates of protein identification, cysteine mapping, and quantification of cysteine-containing peptides. The improved technology has shown utility in thiol redox proteomics. Interestingly, results from HILIC ICAT and SCX ICAT are complementary. Implementation of both provides high coverage analysis of a complex proteome.

  15. Reversible, self cross-linking nanowires from thiol-functionalized polythiophene diblock copolymers.

    Hammer, Brenton A G; Reyes-Martinez, Marcos A; Bokel, Felicia A; Liu, Feng; Russell, Thomas P; Hayward, Ryan C; Briseno, Alejandro L; Emrick, Todd

    2014-05-28

    Poly(3-hexylthiophene)-block-poly(3-(3-thioacetylpropyl) oxymethylthiophene) (P3HT)-b-(P3TT) diblock copolymers were synthesized and manipulated by solvent-induced crystallization to afford reversibly cross-linked semiconductor nanowires. To cross-link the nanowires, we deprotected the thioacetate groups to thiols and they subsequently oxidized to disulfides. Cross-linked nanowires maintained their structural integrity in solvents that normally dissolve the polymers. These robust nanowires could be reduced to the fully solvated polymer, representing a novel, reversible cross-linking procedure for functional P3HT-based nanowire fibrils. Field-effect transistor measurements were carried out to determine the charge transport properties of these nanostructures. PMID:24735371

  16. The enhanced cytotoxicity of misonidazole in the thiol depleted state - An oxygen dependent mechanism

    Incubating A549 cells in the presence of L-buthionine-S, R-sulfoximine and misonidazole under aerobic conditions results in lowered rates of cell growth and greater cytotoxicity than is seen with either drug alone. The authors previously demonstrated the accumulation of hydrogen peroxide from cells treated with misonidazole following the inhibition of GSH-peroxidase with thiol depleting agents. They hypothesize that the enhancement of misonidazole toxicity by L-BSO results from the increased exposure to hydrogen peroxide, and the possible formation of the highly reactive hydroxyl radical in the presence of trace metals via Fenton chemistry. Support for this hypothesis comes from their observations that addition of radical scavengers (such as SOD and catalase) and nutritional antioxidants (vitamin E) to the culture medium will partially inhibit the cytotoxic effects. Further work is being done to measure the products of reaction of toxic oxygen species with cellular macromolecules, i.e. lipids

  17. Probing conformational changes of prestin with thiol-reactive optical switches.

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

    2008-09-15

    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 prestin-transfected cells by approximately 10 mV. These shifts were reversible and were eliminated by pretreatment with iodoacetamide. However, they were little affected by pretreatment with biotin maleimide, which cannot reach the cytoplasmic surface. Our results showed that merocyanine states, with a larger dipole moment, interact with the motor's extended conformation stronger than with the compact conformation by 1.6 x 10(-21) J/molecule. The interaction sites are near the cytoplasmic side of the motor protein. PMID:18556757

  18. Surface Analysis of Gold Nanoparticles Functionalized with Thiol-Modified Glucose SAMs for Biosensor Applications

    Spampinato, Valentina; Parracino, Maria Antonietta; La Spina, Rita; Rossi, Francois; Ceccone, Giacomo

    2016-01-01

    In this work, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Principal Component Analysis (PCA) and X-ray Photoelectron Spectroscopy (XPS) have been used to characterize the surface chemistry of gold substrates before and after functionalization with thiol-modified glucose self-assembled monolayers and subsequent biochemical specific recognition of maltose binding protein (MBP). The results indicate that the surface functionalization is achieved both on flat and nanoparticles gold substrates thus showing the potential of the developed system as biodetection platform. Moreover, the method presented here has been found to be a sound and valid approach to characterize the surface chemistry of nanoparticles functionalized with large molecules. Both techniques were proved to be very useful tools for monitoring all the functionalization steps, including the investigation of the biological behavior of the glucose-modified particles in the presence of the maltose binding protein. PMID:26973830

  19. Thiol reductive stress induces cellulose-anchored biofilm formation in Mycobacterium tuberculosis

    Trivedi, Abhishek; Mavi, Parminder Singh; Bhatt, Deepak; Kumar, Ashwani

    2016-01-01

    Mycobacterium tuberculosis (Mtb) forms biofilms harbouring antibiotic-tolerant bacilli in vitro, but the factors that induce biofilm formation and the nature of the extracellular material that holds the cells together are poorly understood. Here we show that intracellular thiol reductive stress (TRS) induces formation of Mtb biofilms in vitro, which harbour drug-tolerant but metabolically active bacteria with unchanged levels of ATP/ADP, NAD+/NADH and NADP+/NADPH. The development of these biofilms requires DNA, RNA and protein synthesis. Transcriptional analysis suggests that Mtb modulates only ∼7% of its genes for survival in biofilms. In addition to proteins, lipids and DNA, the extracellular material in these biofilms is primarily composed of polysaccharides, with cellulose being a key component. Our results contribute to a better understanding of the mechanisms underlying Mtb biofilm formation, although the clinical relevance of Mtb biofilms in human tuberculosis remains unclear. PMID:27109928

  20. Polysiloxane-based luminescent elastomers prepared by thiol-ene "click" chemistry.

    Zuo, Yujing; Lu, Haifeng; Xue, Lei; Wang, Xianming; Wu, Lianfeng; Feng, Shengyu

    2014-09-26

    Side-chain vinyl poly(dimethylsiloxane) has been modified with mercaptopropionic acid, methyl 3-mercaptopropionate, and mercaptosuccinic acid. Coordinative bonding of Eu(III) to the functionalized polysiloxanes was then carried out and crosslinked silicone elastomers were prepared by thiol-ene curing reactions of these composites. All these europium complexes could be cast to form transparent, uniform, thin elastomers with good flexibility and thermal stability. The networks were characterized by FTIR, NMR, UV/Vis, and luminescence spectroscopy as well as by scanning electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The europium elastomer luminophores exhibited intense red light at 617 nm under UV excitation at room temperature due to the (5)D0 →(7)F2 transition in Eu(III) ions. The newly synthesized luminescent materials offer many advantages, including the desired mechanical flexibility. They cannot be dissolved or fused, and so they have potential for use in optical and electronic applications. PMID:25168644

  1. Single molecular switch based on thiol tethered iron(II)clathrochelate on gold

    Molecular electronics has been associated with high density nano-electronic devices. Developments of molecular electronic devices were based on reversible switching of molecules between the two conductive states. In this paper, self-assembled monolayers of dodecanethiol (DDT) and thiol tethered iron(II)clathrochelate (IC) have been prepared on gold film. The electrochemical and electronic properties of IC molecules inserted into the dodecanethiol monolayer (IC-DDT SAM) were investigated using voltammetric, electrochemical impedance spectroscopy (EIS), scanning tunneling microscopy (STM) and cross-wire tunneling measurements. The voltage triggered switching behaviour of IC molecules on mixed SAM was demonstrated. Deposition of polyaniline on the redox sites of IC-DDT SAM using electrochemical polymerization of aniline was performed in order to confirm that this monolayer acts as nano-patterned semiconducting electrode surface.

  2. Conserved water-mediated H-bonding dynamics of catalytic Asn 175 in plant thiol protease

    Tapas K Nandi; Hridoy R Bairagya; Bishnu P Mukhopadhyay; K Sekar; Dipankar Sukul; Asim K Bera

    2009-03-01

    The role of invariant water molecules in the activity of plant cysteine protease is ubiquitous in nature. On analysing the 11 different Protein DataBank (PDB) structures of plant thiol proteases, the two invariant water molecules W1 and W2 (W220 and W222 in the template 1PPN structure) were observed to form H-bonds with the Ob atom of Asn 175. Extensive energy minimization and molecular dynamics simulation studies up to 2 ns on all the PDB and solvated structures clearly revealed the involvement of the H-bonding association of the two water molecules in fixing the orientation of the asparagine residue of the catalytic triad. From this study, it is suggested that H-bonding of the water molecule at the W1 invariant site better stabilizes the Asn residue at the active site of the catalytic triad.

  3. Oxidative damage induced by herbicides is mediated by thiol oxidation and hydroperoxides production.

    Braconi, Daniela; Bernardini, Giulia; Fiorani, Mara; Azzolini, Catia; Marzocchi, Barbara; Proietti, Fabrizio; Collodel, Giulia; Santucci, Annalisa

    2010-08-01

    Toxicological and environmental issues are associated with the extensive use of agricultural pesticides, although the knowledge of their toxic effects as commercial formulations is still far from being complete. This work investigated the impact of three herbicides as commercial formulations on the oxidative status of a wild type Saccharomyces cerevisiae strain. With yeast being a well-established model of eukaryotic cells, especially as far as regards the stress response, these results may be indicative of potential damages on higher eukaryotes. It was found that herbicide-mediated toxicity towards yeast cells could be the result of an increased production of hydroperoxides (like in the case of the herbicides Pointer and Silglif) or advanced oxidation protein products and lipid peroxidation (especially in the case of the herbicide Proper Energy). Through a redox-proteomic approach it was found also that, besides a common signature, each herbicide showed a specific pattern for protein thiols oxidation. PMID:20528566

  4. Analysis of citrate-capped gold and silver nanoparticles by thiol ligand exchange capillary electrophoresis

    We report on the capillary electrophoretic behavior of citrate-capped gold and silver nanoparticles in aqueous medium when applying a ligand-exchange surface reaction with thiols. Gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) of similar size (39 ± 6 and 41 ± 7 nm, respectively) and shape were synthesized, covered with a citrate shell, and characterized by microscopic and spectroscopic techniques. The analysis of these NPs by CE was accomplished by using a buffer solution (pH 9.7; 40 mM SDS, 10 mM CAPS; 0.1 % methanol) containing the anions of thioctic acid or thiomalic acid. These are capable of differently interacting with the surface of the AuNPs and AgNPs and thus introducing additional negative charges. This results in different migration times due to the formation of differently charged nanoparticles. (author)

  5. Long-timescale dynamics of thiol capped Au nanoparticle clusters at the air-water interface

    Choudhuri, Madhumita; Datta, Alokmay

    2014-04-01

    A two-dimensional network of thiol-capped Au nanoparticle (AuNP) clusters is self-organized on a Stearic Acid (amphiphilic fatty acid) Langmuir monolayer on water surface. The AuNP clusters are found to form a pattern of connected and enclosed microspaces in the stearic acid template. The network features can be controlled by changing the surface pressure of the monolayer during compression. The two-dimensional dynamics of this network has been studied over a long timescale using Brewster Angle Microscopy (BAM). The dynamics is very slow, indicating the stability of the network system, and is essentially driven by the tendency to lower the number of nodes or joints in the network.

  6. HY5 and HYH are positive regulators of nitrate reductase in seedlings and rosette stage plants.

    Jonassen, Else Müller; Lea, Unni S; Lillo, Cathrine

    2008-02-01

    HY5 and HYH are bZIP transcription factors well known to be involved in photomorphogenesis and light signalling. Loss-of-function mutants of HY5 and HYH revealed that these genes are essential for induction of a key enzyme in nitrogen assimilation, nitrate reductase (EC 1.7.1.1). In Arabidopsis thaliana seedlings nitrate reductase was expressed under low irradiance far-red or red light at the same level as under higher irradiance, photosynthetic active, white light. However, high NR expression at low light levels occurred only in the presence of sucrose in the growth medium. Sucrose did not promote expression in darkness. Whereas HY5 was necessary for high nitrate reductase expression in far-red light, HYH was important in red light. COP1 is known to promote degradation of HY5 and HYH, and in the cop1 mutant, nitrate reductase activity was relatively high also in darkness. PhyA and PhyB mutants were tested, and confirmed the phytochrome dependency for far-red and red light induction of nitrate reductase in seedlings. In rosette leaves of 3-week-old green plants the daily increase in nitrate reductase expression in response to light-on was abolished in the hyh and hy5 hyh double mutant. The hy5 hyh double mutant had lower nitrate reductase activity than any of the single mutants in photosynthetic active light in both seedlings and rosette leaves. PMID:17929051

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

    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

    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 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...

  8. Crystal structure of isoflavone reductase from alfalfa (Medicago sativa L.).

    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

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

    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...

  10. Pulse radiolysis studies on superoxide reductase from Treponema pallidum

    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.

  11. Structure of a bacterial homologue of vitamin K epoxide reductase

    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.

  12. Atomistic simulations of thiol-terminated modifiers for hybrid photovoltaic interfaces

    Malloci, G. [Istituto Officina dei Materiali (CNR-IOM), Unit di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Italy); Petrozza, A. [Center for Nano Science and Technology @Polimi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, I-20133 Milano (Italy); Mattoni, A., E-mail: mattoni@iom.cnr.it [Istituto Officina dei Materiali (CNR-IOM), Unit di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Italy)

    2014-06-02

    Small aromatic molecules such as benzene or pyridine derivatives are often used as interface modifiers (IMs) at polymer/metal oxide hybrid interfaces. We performed a theoretical investigation on prototypical thiol-terminated IMs aimed at improving the photovoltaic performances of poly(3-hexylthiophene)/TiO{sub 2} devices. By means of first-principles calculations in the framework of the density functional theory we investigate 3-furanthiol (3FT), 4-mercaptobenzoicacid (4MB), and 6-isoquinolinethiol (6QT) molecules. We discuss the role of these molecules as modifiers alternative to 4-mercaptopyridine (4MP) which has recently shown to induce a large improvement in the overall power conversion efficiency of mesoporous films of TiO{sub 2} infiltrated by poly(3-hexylthiophene). The IMs investigated are expected to keep the beneficial features of 4MP giving at the same time the possibility to further tune the interlayer properties (e.g., its thickness, stability, and density). Dense interlayers of 6QT turn out to be slightly unstable since the titania substrate induces a compressive strain in the molecular film. On the contrary, we predict very stable films for both 3FT and 4MB molecules, which makes them interesting candidates for future experimental investigations. - Highlights: We performed a theoretical investigation on thiol-terminated interface modifiers. We investigate 3-furanthiol (3FT), 4-mercaptobenzoicacid (4MB), and 6-isoquinolinethiol molecules. We discuss the role of these molecules as modifiers alternative to 4-mercaptopyridine. Dense interlayers of 6-isoquinolinethiol turn out to be slightly unstable. We predict very stable self-assembled thin-films for both 3FT and 4MB molecules.

  13. Potentiometric determination of trace amounts of volatile thiols in natural gas

    A potentiometric titration method was developed for the determination of volatile thiols in natural gas. An apparatus was devised for the quantitative absorption of volatile thiols. The measurements were performed in an ethanolic ammonium buffer solution containing a known amount of silver nitrate as supporting electrolyte. The excess silver was precipitated by a known amount of potassium iodide. The excess of iodide was back titrated potentiometrically with a standard solution of silver nitrate. The direct titration of the excess silver ions with a standard solution of potassium iodide gave a poor accuracy compared with the back titration method. Iodide selective electrode was employed as an indicator electrode and a silver-silver chloride electrode as reference electrode. The accuracy and reproducibility of the method were established by preparing several synthetic samples in which ethanthiol containing from 346.61 to 12.11 μUg mercaptan sulfur was taken as standard nitrogen as carrier gas with an optimum flow rate of 31.5 L/hr. The results obtained expressed in the form of Grans plot showed an error ranging from 0.16 to 2.39% by weight and the relative standard deviation did not exceed 2.20%. The amount of mercaptan sulfur determined in Iraqi natural gas taken directly in a cylinder from Dora refinery, Baghdad, Iraq, and after six months of storage we 23.15 Ug/L and 21.25 Ug/L respectively with a relative standard deviation not exceeded 1%. The interferences of hydrogen sulfide could be eliminated by absorption in cadimium acetate containing solution. Other sulfur containing compounds e.g. disulfides, sulfoxides which may be present in natural gas do not interfere with the analysis

  14. Synergistic Effects of Bismuth Thiols and Various Antibiotics Against Pseudomonas aeruginosa Biofilm

    Maryam Varposhti

    2014-03-01

    Full Text Available Background: Pseudomonas aeruginosa is an opportunistic pathogen that takes advantages of some weaknesses in the immune system to initiate an infection. Biofilms of P. aeruginosa can cause chronic opportunistic infections in immunocompromised and elderly patients. This bacterium is considered as a model organism to study antibiotic resistance as well as biofilm formation. In the biofilm structures, bacteria are protected from many harmful environmental factors such as fluctuations in the level of oxygen and nutrients, and the alterations of pH as well as sensitivity to antibiotics. Decreased permeability of biofilms is one of the important reasons of antimicrobial resistance in bacteria. Objectives: In this study the anti-biofilm activity of bismuth thiols in combination with ciprofloxacin, imipenem and ceftazidime against the P. aeruginosa biofilm was investigated. Materials and Methods: Checkerboard method was used to test the susceptibility of biofilms against various antimicrobial combinations. The biofilm formation was measured by 2,3-bis (2-methoxy-4-nitro-5-sulfo-phenyl-2H-tetrazolium-5-carboxanilide (XTT colorimetric assay. The fractional bio-film inhibitory concentration was reported for each agent. Results: The combination of bismuth ethanedithiol with ciprofloxacin showed synergistic inhibitory effect on the P. aeruginosa biofilm formation. The combination of bismuth ethanedithiol ciprofloxacin, ceftazidime and imipenem showed synergistic inhibitory effects on the biofilm formation. Furthermore, the combination of bismuth ethanedithiol, imipenem and ceftazidime did not show any synergistic inhibitory effect on biofilm formation. Conclusions: Our studies show that using appropriate concentrations of bismuth thiols in combination with various antibiotics can act synergistically against P. aeruginosa biofilm formation. Keywords: Biofilms; Pseudomonas aeruginosa; Antibacterial Agents

  15. Differential regulation of tissue thiol-disulfide redox status in a murine model of peritonitis

    Benton Shana M

    2012-10-01

    Full Text Available Abstract Background Glutathione (GSH/glutathione disulfide (GSSG and cysteine (Cys/cystine (CySS are major redox pools with important roles in cytoprotection. We determined the impact of septic peritonitis on thiol-disulfide redox status in mice. Methods FVB/N mice (6–12 week old; 8/group underwent laparotomy with cecal ligation and puncture (CLP or laparotomy alone (control. Sections of ileum, colon, lung and liver were obtained and GSH, GSSG, Cys and CySS concentrations determined by HPLC 24 h after laparotomy. Redox potential [Eh in millivolts (mV] of the GSH/GSSG and Cys/CySS pools was calculated using the Nernst equation. Data were analyzed by ANOVA (mean ± SE. Results GSH/GSSG Eh in ileum, colon, and liver was significantly oxidized in septic mice versus control mice (ileum: septic −202±4 versus control −228±2 mV; colon: -195±8 versus −214±1 mV; and liver: -194±3 vs. -210±1 mV, all Ph was unchanged with CLP, while liver and lung Cys/CySS Eh became significantly more reducing (liver: septic = −103±3 versus control −90±2 mV; lung: -101±5 versus −81±1 mV, each P Conclusions Septic peritonitis induced by CLP oxidizes ileal and colonic GSH/GSSG redox but Cys/CySS Eh remains unchanged in these intestinal tissues. In liver, CLP oxidizes the GSH/GSSG redox pool and CyS/CySS Eh becomes more reducing; in lung, CLP does not alter GSH/GSSG Eh, and Cys/CySS Eh is less oxidized. CLP-induced infection/inflammation differentially regulates major thiol-disulfide redox pools in this murine model.

  16. Functional activation of beta-adrenergic receptors by thiols in the presence or absence of agonists.

    Pedersen, S E; Ross, E M

    1985-11-15

    Treatment of beta-adrenergic receptor with dithiothreitol (DTT) or other thiol compounds caused its functional activation in the presence or absence of agonist ligands. Such activation was observed in reconstituted unilamellar phospholipid vesicles that contained beta-adrenergic receptors, purified to greater than or equal to 95% homogeneity from turkey erythrocyte plasma membranes, and the stimulatory GTP-binding protein of the adenylate cyclase system (Gs) purified from rabbit liver. Incubation of the vesicles with 2-10 mM DTT at 0 degrees C for 1 h increased the rate (4-5-fold) and the extent (3-4-fold) of activation of Gs by guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) binding, an effect about equivalent to the addition of beta-adrenergic agonists. Treatment with DTT also markedly potentiated the ability of agonists to stimulate GTP gamma S binding, increasing the initial rate about 10-fold. DTT treatment was as effective as agonist in stimulating GTPase activity, and maximal stimulation was obtained when DTT-treated vesicles were assayed in the presence of agonist. Other thiol compounds produced effects similar to those of DTT but were at least 10-fold less potent. Stimulation of GTP gamma S binding or GTPase activity required active receptor, and treatment of the receptor with DTT prior to reconstitution also increased its efficacy. There was no effect of DTT on Gs alone. Thus, the site of action of DTT appears to be on the beta-adrenergic receptor itself, and the reduction of disulfides and the binding of agonist act synergistically to activate the receptor. DTT treatment made the receptor more labile to thermal denaturation. Inclusion of cholesterol or cholesteryl-hemisuccinate (5-25%) in the vesicles protected the reduced receptor against such denaturation and enhanced its recovery during reconstitution. No effect of cholesterol or cholesteryl-hemisuccinate was observed on the stability of the nonreduced receptor, which was comparable to that observed in native membranes. PMID:2997196

  17. Size-controlled synthesis, surface functionalization, and biological applications of thiol-organosilica particles.

    Nakamura, Michihiro; Ozaki, Shuji; Abe, Masahiro; Doi, Hiroyuki; Matsumoto, Toshio; Ishimura, Kazunori

    2010-08-01

    Thiol-organosilica particles of a narrow size distribution, made from 3-mercaptopropyltrimethoxysilane (MPMS), were prepared by means of a one-pot synthesis. We examined three synthetic conditions at high temperature (100 degrees C), including the Stöber synthesis and two entirely aqueous syntheses. Under all conditions, the sizes of MPMS particles were well controlled, and the average of the coefficient of variation for the size distribution was less than 20%. The incubation times required for formation of MPMS particles were shorter at high temperature than at low temperature. MPMS particles internally functionalized with fluorescent dye were also prepared by means of the same one-pot synthesis. On flow cytometry analysis these MPMS particles showed distinct peaks of scattering due to well-controlled sizes of particles as well as due to fluorescence signals. Real-time observation of interaction between fluorescent MPMPS particles and cultured cells could be observed under fluorescent microscopy with bright light. The surface of the as-prepared MPMS particles contained exposed mercaptopropyl residues, and the ability to adsorb proteins was at least 6 times higher than that of gold nanopaticles. In addition, fluorescein-labeled proteins adsorbed to the surface of the particles were quantitatively detected at the pg/ml level by flow cytometry. MPMS particles surface functionalized with anti-CD20 antibody using adsorption could bind with lymphoma cells expressing CD20 specifically. In this paper, we demonstrated the possibility of size-controlled thiol-organosilica particles for wild range of biological applications. PMID:20417071

  18. The modulation of carbonyl reductase 1 by polyphenols.

    Bouov, Iva; Sklov, Lenka; Sou?ek, Pavel; Matoukov, Petra

    2015-11-01

    Carbonyl reductase 1 (CBR1), an enzyme belonging to the short-chain dehydrogenases/reductases family, has been detected in all human tissues. CBR1 catalyzes the reduction of many xenobiotics, including important drugs (e.g. anthracyclines, nabumetone, bupropion, dolasetron) and harmful carbonyls and quinones. Moreover, it participates in the metabolism of a number of endogenous compounds and it may play a role in certain pathologies. Plant polyphenols are not only present in many human food sources, but are also a component of many popular dietary supplements and herbal medicines. Many studies reviewed herein have demonstrated the potency of certain flavonoids, stilbenes and curcuminoids in the inhibition of the activity of CBR1. Interactions of these polyphenols with transcriptional factors, which regulate CBR1 expression, have also been reported in several studies. As CBR1 plays an important role in drug metabolism as well as in the protection of the organism against potentially harmful carbonyls, the modulation of its expression/activity may have significant pharmacological and/or toxicological consequences. Some polyphenols (e.g. luteolin, apigenin and curcumin) have been shown to be very potent CBR1 inhibitors. The inhibition of CBR1 seems useful regarding the increased efficacy of anthracycline therapy, but it may cause the worse detoxification of reactive carbonyls. Nevertheless, all known information about the interactions of polyphenols with CBR1 have only been based on the results of in vitro studies. With respect to the high importance of CBR1 and the frequent consumption of polyphenols, in vivo studies would be very helpful for the evaluation of risks/benefits of polyphenol interactions with CBR1. PMID:26415702

  19. Fatty acyl-CoA reductases of birds

    Hellenbrand Janine

    2011-12-01

    Full Text Available Abstract Background Birds clean and lubricate their feathers with waxes that are produced in the uropygial gland, a holocrine gland located on their back above the tail. The type and the composition of the secreted wax esters are dependent on the bird species, for instance the wax ester secretion of goose contains branched-chain fatty acids and unbranched fatty alcohols, whereas that of barn owl contains fatty acids and alcohols both of which are branched. Alcohol-forming fatty acyl-CoA reductases (FAR catalyze the reduction of activated acyl groups to fatty alcohols that can be esterified with acyl-CoA thioesters forming wax esters. Results cDNA sequences encoding fatty acyl-CoA reductases were cloned from the uropygial glands of barn owl (Tyto alba, domestic chicken (Gallus gallus domesticus and domestic goose (Anser anser domesticus. Heterologous expression in Saccharomyces cerevisiae showed that they encode membrane associated enzymes which catalyze a NADPH dependent reduction of acyl-CoA thioesters to fatty alcohols. By feeding studies of transgenic yeast cultures and in vitro enzyme assays with membrane fractions of transgenic yeast cells two groups of isozymes with different properties were identified, termed FAR1 and FAR2. The FAR1 group mainly synthesized 1-hexadecanol and accepted substrates in the range between 14 and 18 carbon atoms, whereas the FAR2 group preferred stearoyl-CoA and accepted substrates between 16 and 20 carbon atoms. Expression studies with tissues of domestic chicken indicated that FAR transcripts were not restricted to the uropygial gland. Conclusion The data of our study suggest that the identified and characterized avian FAR isozymes, FAR1 and FAR2, can be involved in wax ester biosynthesis and in other pathways like ether lipid synthesis.

  20. Isolation and characterization of nitric oxide reductase from Paracoccus halodenitrificans.

    Sakurai, N; Sakurai, T

    1997-11-11

    Nitric oxide reductase was isolated from the membrane fraction of a denitrifying bacterium, Paracoccus halodenitrificans, in the presence of n-dodecyl beta-D-maltoside. A relatively simple and effective procedure to purify NO reductase using DEAE-Toyopearl and hydroxyapatite (ceramic) chromatographies has been developed. The enzyme consisted of two subunits with molecular masses of 20 and 42 kDa associated with the c-type heme and two b-type hemes, respectively. The optical and magnetic circular dichroism (MCD) spectra of the oxidized (as isolated) and reduced enzymes indicated that the heme c is in the low-spin state and the hemes b are in the high- and low-spin states. The EPR spectrum also showed the presence of the split high-spin component (g perpendicular = 6.6, 6.0) and two low spin components (gz,y,x = 2.96, 2.26, 1.46, gz = 3.59). Although the presence of an extra iron was suggested from atomic absorption spectroscopy, a non-heme iron could not be detected by colorimetric titrations using ferene and 2-(5-nitro-2-pyridylazo)- 5-(N-propyl-N-sulfopropylamino)phenolate (PAPS). One of the extra signals at g = 4.3 and 2.00 might come from a non-heme iron, while they may originate from an adventitious iron and a certain nonmetallic radical, respectively. When CO acted on the reduced enzyme, both of the low-spin hemes were not affected, and when NO acted on the reduced enzyme, the optical and MCD spectra were of a mixture of the oxidized and reduced enzymes. Consequently, the reduction of NO was supposed to take place at the high-spin heme b. The heme c and the low-spin heme b centers were considered to function as electron mediators during the intermolecular and intramolecular processes. PMID:9374857

  1. Identification of imine reductase-specific sequence motifs.

    Fademrecht, Silvia; Scheller, Philipp N; Nestl, Bettina M; Hauer, Bernhard; Pleiss, Jürgen

    2016-05-01

    Chiral amines are valuable building blocks for the production of a variety of pharmaceuticals, agrochemicals and other specialty chemicals. Only recently, imine reductases (IREDs) were discovered which catalyze the stereoselective reduction of imines to chiral amines. Although several IREDs were biochemically characterized in the last few years, knowledge of the reaction mechanism and the molecular basis of substrate specificity and stereoselectivity is limited. To gain further insights into the sequence-function relationships, the Imine Reductase Engineering Database (www.IRED.BioCatNet.de) was established and a systematic analysis of 530 putative IREDs was performed. A standard numbering scheme based on R-IRED-Sk was introduced to facilitate the identification and communication of structurally equivalent positions in different proteins. A conservation analysis revealed a highly conserved cofactor binding region and a predominantly hydrophobic substrate binding cleft. Two IRED-specific motifs were identified, the cofactor binding motif GLGxMGx5 [ATS]x4 Gx4 [VIL]WNR[TS]x2 [KR] and the active site motif Gx[DE]x[GDA]x[APS]x3 {K}x[ASL]x[LMVIAG]. Our results indicate a preference toward NADPH for all IREDs and explain why, despite their sequence similarity to β-hydroxyacid dehydrogenases (β-HADs), no conversion of β-hydroxyacids has been observed. Superfamily-specific conservations were investigated to explore the molecular basis of their stereopreference. Based on our analysis and previous experimental results on IRED mutants, an exclusive role of standard position 187 for stereoselectivity is excluded. Alternatively, two standard positions 139 and 194 were identified which are superfamily-specifically conserved and differ in R- and S-selective enzymes. Proteins 2016; 84:600-610. © 2016 Wiley Periodicals, Inc. PMID:26857686

  2. Organic and inorganic mercurials have distinct effects on cellular thiols, metal homeostasis, and Fe-binding proteins in Escherichia coli.

    LaVoie, Stephen P; Mapolelo, Daphne T; Cowart, Darin M; Polacco, Benjamin J; Johnson, Michael K; Scott, Robert A; Miller, Susan M; Summers, Anne O

    2015-12-01

    The protean chemical properties of the toxic metal mercury (Hg) have made it attractive in diverse applications since antiquity. However, growing public concern has led to an international agreement to decrease its impact on health and the environment. During a recent proteomics study of acute Hg exposure in E. coli, we also examined the effects of inorganic and organic Hg compounds on thiol and metal homeostases. On brief exposure, lower concentrations of divalent inorganic mercury Hg(II) blocked bulk cellular thiols and protein-associated thiols more completely than higher concentrations of monovalent organomercurials, phenylmercuric acetate (PMA) and merthiolate (MT). Cells bound Hg(II) and PMA in excess of their available thiol ligands; X-ray absorption spectroscopy indicated nitrogens as likely additional ligands. The mercurials released protein-bound iron (Fe) more effectively than common organic oxidants and all disturbed the Na(+)/K(+) electrolyte balance, but none provoked efflux of six essential transition metals including Fe. PMA and MT made stable cysteine monothiol adducts in many Fe-binding proteins, but stable Hg(II) adducts were only seen in CysXxx(n)Cys peptides. We conclude that on acute exposure: (a) the distinct effects of mercurials on thiol and Fe homeostases reflected their different uptake and valences; (b) their similar effects on essential metal and electrolyte homeostases reflected the energy dependence of these processes; and (c) peptide phenylmercury-adducts were more stable or detectable in mass spectrometry than Hg(II)-adducts. These first in vivo observations in a well-defined model organism reveal differences upon acute exposure to inorganic and organic mercurials that may underlie their distinct toxicology. PMID:26498643

  3. Thiol-Activatable Triplet-Triplet Annihilation Upconversion with Maleimide-Perylene as the Caged Triplet Acceptor/Emitter.

    Mahmood, Zafar; Zhao, Jianzhang

    2016-01-15

    Efficient thiol-activated triplet-triplet annihilation (TTA) upconversion system was devised with maleimide-caged perylene (Py-M) as the thiol-activatable triplet acceptor/emitter and with diiodoBodipy as the triplet photosensitizer. The photophysical processes were studied with steady-state UV-vis absorption spectroscopy, fluorescence spectroscopy, electrochemical properties, and nanosecond transient absorption spectroscopy. The triplet acceptor/emitter Py-M shows week fluorescence (ΦF = 0.8%), and no upconversion (ΦUC = 0%) was observed. The quenching of fluorescence of Py-M is due to photoinduced electron-transfer (PET) process from perylene to maleimide-caging unit, which quenches the singlet excited state of perylene. The fluorescence of Py-M was enhanced by 200-fold (ΦF = 97%) upon addition of thiols such as 2-mercaptoethanol, and the ΦUC was increased to 5.9%. The unique feature of this thiol-activated TTA upconversion is that the activation is based on addition reaction of the thiols with the caged acceptor/emitter, and no side products were formed. The previously reported cleavage approach gives side products which are detrimental to the TTA upconversion. With nanosecond transient absorption spectroscopy, we found that the triplet excited state of Py-M was not quenched by any PET process, which is different from singlet excited state (fluorescence) of Py-M. The results are useful for study of the triplet excited states of organic chromophores and for activatable TTA upconversion. PMID:26694534

  4. Thiomers: Influence of molecular mass and thiol group content of poly(acrylic acid) on efflux pump inhibition.

    Grabovac, Vjera; Laffleur, Flavia; Bernkop-Schnürch, Andreas

    2015-09-30

    The aim of the present study was to investigate the influence of molecular mass and thiol group content of poly(acrylic acid)-cysteine conjugates on the permeation of sulforhodamine 101 and penicillin G. acting as substrates for multidrug resistance-associated protein 2 efflux pump. Poly(acrylic acids) of 2 kDa, 100 kDa, 250 kDa, 450 kDa and 3000 kDa were conjugated with cysteine. The thiol group content of all these polymers was in the range from 343.3 ± 48.4 μmol/g to 450.3 ± 76.1 μmol/g. Transport studies were performed on rat small intestine mounted in Ussing-type chambers. Since 250 kDa poly(acrylic acid) showed the highest permeation enhancing effect, additionally thiolated 250 kDa polyacrylates displaying 157.2 μmol/g, 223.0 ± 18.1 and 355.9 μmol/g thiol groups were synthesized in order to investigate the influence of thiol group content on the permeation enhancement. The permeation of sulforhodamine was 3.93- and 3.85-fold improved using 250 kDa poly(acrylic acid)-cysteine conjugate exhibiting 355.9 ± 39.5 μmol/g and 223.0 ± 18.1 μmol/g thiol groups. Using the same conjugates the permeation of penicillin G was 1.70- and 1.59-fold improved, respectively. The study demonstrates that thiolated poly(acrylic acid) inhibits Mrp2 mediated transport and that the extent of inhibition depends on the molecular mass and degree of thiolation of the polymer. PMID:26238816

  5. Pyrroline-5-Carboxylate Reductase in Chlorella autotrophica and Chlorella saccharophila in Relation to Osmoregulation.

    Lalibert, 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

  6. Ribonucleotide reductase activity is regulated by proliferating cell nuclear antigen (PCNA)

    Salguero, Israel; Guarino, Estrella; Shepherd, Marianne; Deegan, Tom; Havens, Courtney G; MacNeill, Stuart A.; Walter, Johannes C.; Kearsey, Stephen E.

    2012-01-01

    Synthesis of dNTPs is required for both DNA replication and DNA repair and is catalyzed by ribonucleotide reductases (RNR), which convert ribonucleotides to their deoxy forms [1, 2]. Maintaining the correct levels of dNTPs for DNA synthesis is important for minimising the mutation rate [3-7], and this is achieved by tight regulation of ribonucleotide reductase [2, 8, 9]. In fission yeast, ribonucleotide reductase is regulated in part by a small protein inhibitor, Spd1, which is degraded in S ...

  7. Chemical cytometry of thiols using capillary zone electrophoresis-laser induced fluorescence and TMPAB-o-M, an improved fluorogenic reagent.

    Guo, Xiao-Feng; Arceo, Jennifer; Huge, Bonnie Jaskowski; Ludwig, Katelyn R; Dovichi, Norman J

    2016-02-01

    Low molecular weight thiol compounds play crucial roles in many physiological processes. Most methods for determination of thiol compounds are population-averaged; few methods for quantification of thiol compounds in single cells have been reported. We report an ultrasensitive method for determination of thiol compounds in single cells by use of 1,3,5,7-tetramethyl-8-phenyl-(2-maleimide)-difluoroboradiaza-s-indacene (TMPAB-o-M), a fluorogenic probe with useful spectral properties, coupled with capillary zone electrophoresis and laser induced fluorescence detection using a post-column sheath flow cuvette. TMPAB-o-M provides low background, high sensitivity, and excellent reactivity. After optimization of the separation method, we achieved baseline separation of labeled glutathione (GSH), cysteine (Cys), homocysteine, and γ-glutamylcysteine within 11 min, and produced concentration limits of detection from 10 to 20 pM and mass LODs of 65 to 100 zmol. The method was applied for analysis of thiol containing compounds in both cell homogenates and in single HCT-29 and MCF-10A cells. GSH was the main thiol, and Cys was also detected in both cell types. Cells were treated with N-ethylmaleimide, which significantly attenuated thiol levels. PMID:26814594

  8. Hydrogen-transfer and charge transfer in photochemical and high energy radiation induced reactions: effects of thiols. Final report, February 1, 1960-january 31, 1979

    Absorption of ultraviolet or visible light, or high energy radiation, may lead to highly reactive free radicals. Thiols affect the reactions of these radicals in the following ways: (1) transfer of hydrogen from sulfur of the thiol to a substrate radical, converting the radical to a stable molecule, and the thiol to a reactive thiyl radical; and (2) transfer of hydrogen from a substrate radical or molecule to thiyl, regenerating thiol. The thiol is thus used repeatedly and a single molecule may affect the consequences of many quanta. Three effects may ensue, depending upon the system irradiated: (1) the substrate radicals may be converted by thiol-thiyl to the original molecules, and protection against radiation damage is afforded. (2) The radicals may be converted to molecules not identical with the starting materials, and in both cases damage caused by radical combination processes is prevented. (3) Product yields may be increased where the initial radicals might otherwise regenerate starting materials. It was shown that rates of reaction of excited species can be correlated with triplet energies and reduction potentials, and with ionization potentials, that amines are very reactive toward excited carbonyl compounds of all types, and that yields of products from these reactions can be increased by thiols, leading to increased efficiency in utilization of light

  9. Applying the designed multiple ligands approach to inhibit dihydrofolate reductase and thioredoxin reductase for anti-proliferative activity.

    Ng, Hui-Li; Chen, Shangying; Chew, Eng-Hui; Chui, Wai-Keung

    2016-06-10

    The development of multi-targeting drugs is currently being explored as an attractive alternative to combination therapy, especially for the treatment of complex diseases such as cancer. Dihydrofolate reductase (DHFR) and thioredoxin reductase (TrxR) are enzymes belonging to two unrelated cellular pathways that are known to contribute towards cancer cell growth and survival. In order to evaluate whether simultaneous inhibition of DHFR and TrxR by dihydrotriazines (DHFR-targeting) and chalcones (TrxR-targeting) may be beneficial, breast MCF-7 and colorectal HCT116 carcinoma cells were treated with combinations of selected dihydrotriazines and chalcones at a 1:1 M ratio. Two combinations demonstrated synergy at low-to-moderate concentrations. Based on this result, four merged dihydrotriazine-chalcone compounds were designed and synthesized. Two compounds, 11a [DHFR IC50 = 56.4 μM, TrxR IC50 (60 min) = 12.6 μM] and 11b [DHFR IC50 = 2.4 μM, TrxR IC50 (60 min) = 10.1 μM], demonstrated in vitro inhibition of DHFR and TrxR. The compounds showed growth inhibitory activity against MCF-7 and HCT116 cells, but lacked cytotoxicity. Molecular docking experiments showed 11b to possess rational binding modes to both the enzymes. In conclusion, this study has not only identified the dihydrotriazine and chalcone scaffolds as good starting points for the development of dual inhibitors of DHFR and TrxR, but also demonstrated the synthetic feasibility of producing a chemical entity that could result in simultaneous inhibition of DHFR and TrxR. Future efforts to improve the antiproliferative profiles of such compounds will look at alternative ways of integrating the two pharmacophoric scaffolds. PMID:26994844

  10. Inhibition of glutathione synthesis eliminates the adaptive response of ascitic hepatoma 22 cells to nedaplatin that targets thioredoxin reductase

    Wang, Yijun [School of Tea and Food Science, Anhui Agricultural University, Hefei 230036, Anhui (China); Lu, Hongjuan [Productivity Center of Jiangsu Province, Nanjing 210042, Jiangsu (China); Wang, Dongxu; Li, Shengrong; Sun, Kang; Wan, Xiaochun [School of Tea and Food Science, Anhui Agricultural University, Hefei 230036, Anhui (China); Taylor, Ethan Will [Department of Nanoscience, Joint School of Nanoscience and Nanoengineering, University of North Carolina at Greensboro, Greensboro, NC 27402 (United States); Zhang, Jinsong, E-mail: zjs@ahau.edu.cn [School of Tea and Food Science, Anhui Agricultural University, Hefei 230036, Anhui (China)

    2012-12-15

    Thioredoxin reductase (TrxR) is a target for cancer therapy and the anticancer mechanism of cisplatin involves TrxR inhibition. We hypothesize that the anticancer drug nedaplatin (NDP), an analogue of cisplatin and a second-generation platinum complex, also targets TrxR. Furthermore, we investigate whether the therapeutic efficacy of NDP can be enhanced by simultaneous modulation of 1) TrxR, via NDP, and 2) glutathione (GSH), via the GSH synthesis inhibitor buthionine sulfoximine (BSO). Mice bearing ascitic hepatoma 22 (H22) cells were treated with NDP alone or NDP plus BSO. TrxR activity of H22 cells was inhibited by NDP in a dose-dependent manner. A high correlation between the inhibition of TrxR activity at 6 h and the inhibition of ascitic fluid volume at 72 h was established (r = 0.978, p < 0.01). As an adaptive response, the viable ascitic cancer cells after NDP treatment displayed an enlarged cell phenotype, assembled with several-fold more antioxidant enzymes and GSH-predominant non-protein free thiols. This adaptive response was largely eliminated when BSO was co-administered with NDP, leading to the decimation of the H22 cell population without enhancing renal toxicity, since at this dose, NDP did not inhibit renal TrxR activity. In conclusion, the pharmacological effect of NDP involves TrxR inhibition, and the adaptive response of NDP-treated ascitic H22 cells can be efficiently counteracted by BSO. Simultaneous modulation of TrxR and GSH on ascitic H22 cells using NDP plus BSO greatly enhances therapeutic efficacy as compared with the single modulation of TrxR using NDP alone. -- Highlights: ► Nedaplatin at a pharmacological dose inhibits TrxR in cancer cells but not in kidney. ► The nedaplatin-treated cancer cells exhibit adaptive response. ► Buthionine sulfoximine inhibits glutathione in both cancer cells and kidney. ► Buthionine sulfoximine counteracts the adaptive response to the nedaplatin treatment. ► Buthionine sulfoximine does not aggravate renal toxicity of the nedaplatin treatment.

  11. Inhibition of glutathione synthesis eliminates the adaptive response of ascitic hepatoma 22 cells to nedaplatin that targets thioredoxin reductase

    Thioredoxin reductase (TrxR) is a target for cancer therapy and the anticancer mechanism of cisplatin involves TrxR inhibition. We hypothesize that the anticancer drug nedaplatin (NDP), an analogue of cisplatin and a second-generation platinum complex, also targets TrxR. Furthermore, we investigate whether the therapeutic efficacy of NDP can be enhanced by simultaneous modulation of 1) TrxR, via NDP, and 2) glutathione (GSH), via the GSH synthesis inhibitor buthionine sulfoximine (BSO). Mice bearing ascitic hepatoma 22 (H22) cells were treated with NDP alone or NDP plus BSO. TrxR activity of H22 cells was inhibited by NDP in a dose-dependent manner. A high correlation between the inhibition of TrxR activity at 6 h and the inhibition of ascitic fluid volume at 72 h was established (r = 0.978, p < 0.01). As an adaptive response, the viable ascitic cancer cells after NDP treatment displayed an enlarged cell phenotype, assembled with several-fold more antioxidant enzymes and GSH-predominant non-protein free thiols. This adaptive response was largely eliminated when BSO was co-administered with NDP, leading to the decimation of the H22 cell population without enhancing renal toxicity, since at this dose, NDP did not inhibit renal TrxR activity. In conclusion, the pharmacological effect of NDP involves TrxR inhibition, and the adaptive response of NDP-treated ascitic H22 cells can be efficiently counteracted by BSO. Simultaneous modulation of TrxR and GSH on ascitic H22 cells using NDP plus BSO greatly enhances therapeutic efficacy as compared with the single modulation of TrxR using NDP alone. -- Highlights: ► Nedaplatin at a pharmacological dose inhibits TrxR in cancer cells but not in kidney. ► The nedaplatin-treated cancer cells exhibit adaptive response. ► Buthionine sulfoximine inhibits glutathione in both cancer cells and kidney. ► Buthionine sulfoximine counteracts the adaptive response to the nedaplatin treatment. ► Buthionine sulfoximine does not aggravate renal toxicity of the nedaplatin treatment.

  12. Potentiometric study of rhenium (V) complex formation with 4-methyl-1.2.4-triazol thiol-5 in the medium of 7 mol/l HBr

    Present article is devoted to potentiometric study of rhenium (V) complex formation with 4-methyl-1.2.4-triazol thiol-5 in the medium of 7 mol/l HBr. The function of formation of oxo bromine-4-methyl-1.2.4-triazol thiol complexes of rhenium (V) in the medium of 5 mol/l HBr at 273 K temperature was determined. The function of formation of oxo bromine-4-methyl-1.2.4-triazol thiol complexes of rhenium (V) in the medium of 5 mol/l HBr at 298 K temperature was determined as well.

  13. Molecular characterization of five patients with homocystinuria due to severe methylenetetrahydrofolate reductase deficiency

    Urreizti, R; Moya-García, A A; Pino-Ángeles, A; Cozar, M; Langkilde, A; Fanhoe, U; Esteves, C; Arribas, J; Vilaseca, M A; Pérez-Dueñas, B; Pineda, M; González, V; Artuch, R; Baldellou, A; Vilarinho, L; Fowler, B; Ribes, A; Sánchez-Jiménez, F; Grinberg, D; Balcells, S

    2010-01-01

    homocystinuria due to severe MTHFR deficiency. Methylenetetrahydrofolate reductase (MTHFR) plays a major role in folate metabolism. Disturbed function of the enzyme results in hyperhomocysteinemia and causes severe vascular and neurological disorders and developmental delay. Five patients suspected of having non...

  14. Characterization and regulation of Leishmania major 3-hydroxy-3-methylglutaryl-CoA reductase

    Montalvetti, A; Pena Diaz, Javier; Hurtado, R; Ruiz-Pérez, L M; González-Pacanowska, D

    Leishmania lacks the membrane domain characteristic of eukaryotic cells but exhibits sequence similarity with eukaryotic reductases. Highly purified protein was achieved by ammonium sulphate precipitation followed by chromatography on hydroxyapatite. Kinetic parameters were determined for the protozoan...

  15. Molecular profiling and functional insights of rock bream (Oplegnathus fasciatus) thioredoxin reductase 3-like molecule: investigation of its transcriptional modulation in response to live pathogen stress.

    Elvitigala, Don Anushka Sandaruwan; Whang, Ilson; Lee, Jehee

    2015-10-01

    The thioredoxin (Trx) system plays a significant role in cellular antioxidative defense by dismutating the surpluses of reactive oxygen species. Thus, the role of thioredoxin reductase (TrxR) cannot be ignored, owing to its participation in initiating the Trx enzyme cascade. Here, we report the identification and molecular characterization of a teleostean TrxR (RbTrxR-3) ortholog that showed high similarity with the TrxR-3 isoforms of other vertebrates. The complete RbTrxR-3 coding sequence comprised 1800 nucleotides, encoding a 600-amino acid protein with a predicted molecular mass of ~66 kDa. RbTrxR-3 consisted of 16 exons separated by 15 introns and had a total length of 12,658 bp. In silico analysis of the RbTrxR-3 protein sequence revealed that it possesses typical TrxR domain architecture. Moreover, using multiple sequence alignment and pairwise sequence alignment strategies, we showed that RbTrxR-3 has high overall sequence similarity to other teleostean TrxR-3 proteins, including highly conserved active site residues. Phylogenetic reconstruction of RbTrxR-3 affirmed its close evolutionary relationship with fish TrxR-3 orthologs, as indicated by its clustering pattern. RbTrxR-3 transcriptional analysis, performed using quantitative polymerase chain reaction (qPCR), showed that RbTrxR-3 was ubiquitously distributed, with the highest level of mRNA expression in the blood, followed by the gill, and liver. Live bacterial and viral stimuli triggered the modulation of RbTrxR-3 basal transcription in liver tissues that correlated temporally with that of its putative substrate, rock bream thioredoxin1 under the same conditions of pathogenic stress. Finally, resembling the typical function of TrxR protein, purified recombinant RbTrxR-3 showed detectable dose-dependent thiol reductase activity against 5,5'-dithiobis (2-nitrobenzoic) acid. Taken together, these results suggest that RbTrxR-3 plays a role in the host Trx system under conditions of oxidative and pathogenic stress. PMID:26055087

  16. Interaction of Product Analogs with the Active Site of Rhodobacter sphaeroides Dimethylsulfoxide Reductase

    George, Graham N.; Nelson, Kimberly Johnson; Harris, Hugh H.; Doonan, Christian J.; Rajagopalan, K V

    2007-01-01

    We report a structural characterization using X-ray absorption spectroscopy of Rhodobacter sphaeroides dimethylsulfoxide (DMSO) reductase reduced with trimethylarsine, and show that this is structurally analogous to the physiologically relevant dimethylsulfide-reduced DMSO reductase. Our data unambiguously indicate that these species should be regarded as formal MoIV species, and indicate a classical coordination complex of trimethylarsine oxide, with no special structural distortions. The si...

  17. Expression of the mouse dihydrofolate reductase complementary deoxyribonucleic acid in simian virus 40 vectors.

    Subramani, S.; Mulligan, R.; Berg, P

    1981-01-01

    A mouse complementary deoxyribonucleic acid segment coding for the enzyme dihydrofolate reductase has been cloned in two general classes of vectors containing simian virus 40 deoxyribonucleic acid: (i) those that can be propagated as virions in permissive cells and (ii) those that can be introduced into and maintained stably in various mammalian cells. Both types of vectors express the mouse dihydrofolate reductase by using signals supplied by simian virus 40 deoxyribonucleic acid sequences. ...

  18. Vitamin K Epoxide Reductase Complex 1 (VKORC1) Gene Polymorphisms in Population of Eastern Croatia

    Mandić, Dario; Mandić, Sanja; Samardžija, Marina; Samardžija, Marko

    2013-01-01

    Vitamin K epoxide reductase (VKOR) is a key enzyme in the g-carboxylation of proteins associated with important bodily functions (coagulation, bone metabolism, etc.). This feature is particularly used in warfarin therapy, which blocks the VKOR enzyme and leads to production of dysfunctional coagulation proteins. Genetic factors, particularly vitamin K epoxide reductase complex 1 (VKORC1) gene, have greatest influence on warfarin therapy. The aim of this study was to determine the distribution...

  19. Phytoalexin synthesis in soybean cells: elicitor induction of reductase involved in biosynthesis of 6'-deoxychalcone.

    Welle, R; Grisebach, H

    1989-07-01

    Chromatofocusing on Mono P proved to be an efficient purification procedure for the NADPH-dependent reductase from soybean (Glycine max L.) cell cultures which acts together with chalcone synthase in the biosynthesis of 2',4',4-trihydroxychalcone (6'-deoxychalcone). By isoelectric focusing the pI of reductase was determined to be 6.3. Addition of pure soybean reductase to cell-free extracts from stimulated cell cultures of parsley and bean (Phaseolus vulgaris) and from young flowers of Dahlia variabilis caused in each case synthesis of 6'-deoxychalcone. When 4-coumaroyl-CoA was replaced by caffeoyl-CoA in the reductase assay, formation of 2',4',3,4-tetrahydrochalcone (butein) was observed. A polyclonal antireductase antiserum was raised in rabbits and proved to be specific in Ouchterlony diffusion experiments, Western blots and immunotitration. The reductase antiserum showed no cross-reactivity with soybean chalcone synthase (CHS). A biotin/[125I]streptavidin system provided a quantitative Western blot for the reductase. Changes in the activities, amounts of protein, and mRNA activities of reductase and CHS were determined after challenge of soybean cell cultures by elicitor (from Phytophthora megasperma f.sp. glycinea or yeast). For both enzymes a pronounced and parallel increase in activity and amounts of protein was observed after elicitor addition with a maximum at about 16 h after challenge. Parallel increases in mRNA activities occurred earlier. The results indicate a parallel induction of de novo synthesis of reductase and CHS which coact in synthesis of 6'-deoxychalcone. PMID:2500065

  20. Acceleration of an aldo-keto reductase by minimal loop engineering

    Krump, C.; Vogl, M.; Brecker, L.; Nidetzky, B.; Kratzer, R.

    2014-01-01

    Aldo-keto reductases tighten coenzyme binding by forming a hydrogen bond across the pyrophosphate group of NAD(P)(H). Mutation of the hydrogen bonding anchor Lys24 in Candida tenuis xylose reductase prevents fastening of the safety belt around NAD(H). The loosened NAD(H) binding leads to increased turnover numbers (kcat) for reductions of bulky-bulky ketones at constant substrate and coenzyme affinities (i.e. Km Ketone, Km NADH). PMID:24951537

  1. Targeting thioredoxin reductase is a basis for cancer therapy by arsenic trioxide

    Lu, Jun; Chew, Eng-Hui; Holmgren, Arne

    2007-01-01

    Arsenic trioxide (ATO) is an effective cancer therapeutic drug for acute promyelocytic leukemia and has potential anticancer activity against a wide range of solid tumors. ATO exerts its effect mainly through elevated oxidative stress, but the exact molecular mechanism remains elusive. The thioredoxin (Trx) system comprising NADPH, thioredoxin reductase (TrxR), and Trx and the glutathione (GSH) system composed of NADPH, glutathione reductase, and GSH supported by glutaredoxin are the two elec...

  2. Molecular pharmacology and antitumor activity of palmarumycin based inhibitors of thioredoxin reductase.

    Powis, Garth; Wipf, Peter; Lynch, Stephen M.; Birmingham, Anne; Kirkpatrick, D. Lynn

    2006-01-01

    The cytosolic thioredoxin (Trx) redox system comprising Trx-1 and the NADPH dependent thioredoxin reductase -1 reductase (TrxR-1) is an important regulator of cell growth and survival. Trx-1 is overexpressed in many human tumors where it is associated with increased cell proliferation, decreased apoptosis and decreased patient survival. We hypothesized that TrxR-1 provides a target to inhibit the activity of overexpressed Trx-1 for the development of novel anticancer agents. We found that the...

  3. Design and synthesis of hepatoselective, pyrrole-based HMG-CoA reductase inhibitors.

    Pfefferkorn, Jeffrey A; Song, Yuntao; Sun, Kuai-Lin; Miller, Steven R; Trivedi, Bharat K; Choi, Chulho; Sorenson, Roderick J; Bratton, Larry D; Unangst, Paul C; Larsen, Scott D; Poel, Toni-Jo; Cheng, Xue-Min; Lee, Chitase; Erasga, Noe; Auerbach, Bruce; Askew, Valerie; Dillon, Lisa; Hanselman, Jeffrey C; Lin, Zhiwu; Lu, Gina; Robertson, Andrew; Olsen, Karl; Mertz, Thomas; Sekerke, Catherine; Pavlovsky, Alexander; Harris, Melissa S; Bainbridge, Graeme; Caspers, Nicole; Chen, Huifen; Eberstadt, Matthias

    2007-08-15

    This manuscript describes the design and synthesis of a series of pyrrole-based inhibitors of HMG-CoA reductase for the treatment of hypercholesterolemia. Analogs were optimized using structure-based design and physical property considerations resulting in the identification of 44, a hepatoselective HMG-CoA reductase inhibitor with excellent acute and chronic efficacy in a pre-clinical animal models. PMID:17574412

  4. Glutathione reductase is not required for maintenance of reduced glutathione in Escherichia coli K-12.

    Tuggle, C K; Fuchs, J A

    1985-01-01

    Seven independently isolated glutathione reductase-deficient (gor) Escherichia coli mutants were found to have an in vivo glutathione redox state that did not significantly differ from that of the parental strain, 98 to 99% reduced. Strains containing both a gor mutation and either a trxA mutation (thioredoxin deficient) or a trxB mutation (thioredoxin reductase deficient) were able to maintain a 94 to 96% reduced glutathione pool, suggesting that glutathione can be reduced independently of g...

  5. Thiol-thione tautomeric analysis, spectroscopic (FT-IR, Laser-Raman, NMR and UV-vis) properties and DFT computations of 5-(3-pyridyl)-4H-1,2,4-triazole-3-thiol molecule.

    Gökce, Halil; Öztürk, Nuri; Ceylan, Ümit; Alpaslan, Yelda Bingöl; Alpaslan, Gökhan

    2016-06-15

    In this study, the 5-(3-pyridyl)-4H-1,2,4-triazole-3-thiol molecule (C7H6N4S) molecule has been characterized by using FT-IR, Laser-Raman, NMR and UV-vis spectroscopies. Quantum chemical calculations have been performed to investigate the molecular structure (thione-thiol tautomerism), vibrational wavenumbers, electronic transition absorption wavelengths in DMSO solvent and vacuum, proton and carbon-13 NMR chemical shifts and HOMOs-LUMOs energies at DFT/B3LYP/6-311++G(d,p) level for all five tautomers of the title molecule. The obtained results show that the calculated vibrational wavenumbers, NMR chemical shifts and UV-vis wavelengths are in a good agreement with experimental data. PMID:27054702

  6. Nitrate reductase activity and its relationship with applied nitrogen in soybean

    Field experiments were conducted to study the nitrate reductase activity and its relationship to nitrogen by using frame tests (pot without bottom), sand culture and 15N-urea at transplanting in soybean variety Suinong 14. Results showed that the activity of nitrate reductase in leaf changed as a signal peak curve with the soybean growth, lower in vegetative growth phase, higher in reproductive growth period and reached the peak in blooming period, then decreased gradually. Nitrogen application showed obvious effect on the nitrate reductase activity. The activities of nitrate reductase in leaves followed the order of N135 > N90 > N45 > N0 in vegetative growth stage, no clear regularity was found during the whole reproductive growth period. The activities of nitrate reductase in leaves were accorded with the order of upper leaves > mid leaves > lower leaves, and it was very significant differences (P15N labeling method during beginning seed stage and full seed stage shown that 15N abundance in various organs at different node position also followed the same order, suggesting that high level of nitrate reductase activity at upper leaves of soybean promoted the assimilation of NO3-. (authors)

  7. Purification and characterization of (+)dihydroflavonol (3-hydroxyflavanone) 4-reductase from flowers of Dahlia variabilis.

    Fischer, D; Stich, K; Britsch, L; Grisebach, H

    1988-07-01

    Individual flowers from inflorescences of Dahlia variabilis (cv Scarlet Star) in young developmental stages contained relatively high activity of (+)-dihydroflavonol (DHF) 4-reductase. The DHF reductase was purified from such flowers to apparent homogeneity by a five-step procedure. This included affinity adsorption on Blue Sepharose and elution of the enzyme with NADP+. By gel filtration and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis it was shown that DHF reductase contains only one polypeptide chain with a Mr of about 41,000. The reductase required NADPH as cofactor and catalyzed transfer of the pro-S hydrogen of NADPH to the substrate. Flavanones and dihydroflavonols (3-hydroxyflavanones) were substrates for DHF reductase with pH optima of about 6.0 for flavanones and of about 6.8 for dihydroflavonols. Flavanones were reduced to the corresponding flavan-4-ols and (+)-dihydroflavonols to flavan-3,4-cis-diols. Apparent Michaelis constants determined for (2S)-naringenin, (2S)-eriodicytol, (+)-dihydrokaempferol, (+)-dihydroquercetin, and NADPH were, respectively, 2.3, 2, 10, 15, and 42 microM. V/Km values were higher for dihydroflavonols than for flavanones. Conversion of dihydromyricetin to leucodelphinidin was also catalyzed by the enzyme at a low rate, whereas flavones and flavonols were not accepted as substrates. DHF reductase was not inhibited by metal chelators. PMID:3293532

  8. Binding of enterolactone and enterodiol to human serum albumin: increase of cysteine-34 thiol group reactivity.

    Takić, Marija M; Jovanović, Vesna B; Pavićević, Ivan D; Uzelac, Tamara N; Aćimović, Jelena M; Ristić-Medić, Danijela K; Mandić, Ljuba M

    2016-02-17

    The interaction of polyphenolic molecules with human serum albumin (HSA) could lead to changes in the reactivity of the HSA Cys34 thiol group (HSA-SH). The influences of enterolactone (EL) and enterodiol (ED) binding on HSA-SH reactivity in fatty acid (FA)-free HSA, and in HSA with bound stearic acid (S) in S/HSA molar ratios of 1 : 1 and 4 : 1, were investigated by the determination of the pseudo first order rate constants (k') for the thiol reaction with 5,5'-dithiobis-(2-nitrobenzoic acid). The binding affinities and binding sites of EL and ED were also determined, using fluorescence measurements of the intrinsic fluorescence of Trp214 and diazepam (binding site marker). EL and ED binding to HSA increased the reactivity of HSA-SH in all assayed HSA-enterolignan complexes by 9.1-33.1%. The strongest effects were obtained for FA-free HSA-enterolignan complexes. S modulated/reduced the effect of EL on HSA-SH reactivity, while its influence on the effect of ED was negligible. The binding of enterolignans to HSA was investigated: the binding constants were the highest for FA-free HSA (EL: 11.64 × 10(4) M(-1) and ED: 5.59 × 10(4) M(-1) at 37 °C) and the lowest for S/HSA 4 : 1-enterolignan complexes (EL: 2.43 × 10(4) M(-1) and ED: 1.92 × 10(4) M(-1)). When the S/HSA ratio was increased, the binding affinities and number of binding sites for EL and ED were decreased. At the same time, a high correlation between binding constants and increased Cys34 reactivity was found (r = 0.974). Competitive experiments using diazepam indicated that the binding of ED and of EL was located in the hydrophobic pocket of site II in HSA. Overall, it is evident that stearic acid could modulate the enterolignan effects on HSA-SH reactivity as well as their binding to HSA. This finding could be important for pharmacokinetics and the expression of enterolignan antioxidant effects in vivo after an intake of lignan rich food. PMID:26838610

  9. Spectroscopic Characterization of Extracellular Polymeric Substances from Escherichia coli and Serratia marcescens: Suppression using Sub-Inhibitory Concentrations of Bismuth Thiols

    Badireddy, Appala R.; Korpol, Bhoom Reddy; Chellam, Shankararaman; Gassman, Paul L.; Engelhard, Mark H.; Lea, Alan S.; Rosso, Kevin M.

    2008-10-21

    Free and capsular EPS produced by Escherichia coli and Serratia marcescens were characterized in detail using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES). Total EPS production decreased upon treatment with sub-inhibitory concentrations of lipophilic bismuth thiols (bismuth dimercaptopropanol, BisBAL; bismuth ethanedithiol, BisEDT; and bismuth pyrithione, BisPYR), BisBAL being most effective. Bismuth thiols also influenced acetylation and carboxylation of polysaccharides in EPS from S. marcescens. Extensive homology between EPS samples in the presence and absence of bismuth was observed with proteins, polysaccharides, and nucleic acids varying predominantly only in the total amount expressed. Second derivative analysis of the amide I region of FTIR spectra revealed decreases in protein secondary structures in the presence of bismuth thiols. Hence, anti-fouling properties of bismuth thiols appear to originate in their ability to suppress O-acetylation and protein secondary structures in addition to total EPS secretion.

  10. Low polymerization-shrinkage nanoparticle-polymer composite films based on thiol-ene photopolymerization for holographic data storage

    Tomita, Yasuo; Hata, Eiji; Omura, Koji; Yasui, Satoru

    2010-05-01

    We demonstrate volume holographic recording in nanoparticle-polymer composites using thiol-ene monomers capable of step-growth polymerization by which shrinkage can be reduced as low as 0.2%. The reduced shrinkage is comparable to other low-shrinkage dry photopolymer systems such as those including a high content of inert binder components and using monomers capable of cationic ring-opening polymerization. It is shown that the thiol-ene based organic nanoparticle-polymer composites possess the refractive index modulation and the material sensitivity of 8×10-3 and 1014 cm/J, respectively, in the green, larger than the minimum acceptable values of 0.005 and 500 cm/J for holographic data storage.

  11. X-ray magnetic circular dichroism and small angle neutron scattering studies of thiol capped gold nanoparticles.

    de la Venta, J; Bouzas, V; Pucci, A; Laguna-Marco, M A; Haskel, D; te Velthuis, S G E; Hoffmann, A; Lal, J; Bleuel, M; Ruggeri, G; de Julin Fernndez, C; Garca, M A

    2009-11-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 x 10(-4) was found at the Au L3 edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M(S), of 0.06 emu/g(Au). SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences. PMID:19908546

  12. SYNTHESIS, STRUCTURAL CHARACTERIZATION AND ENZYME INHIBITION STUDIES ON 5-(2-NITROSTYRYL)-1,3,4-OXADIAZOLE-2-THIOL DERIVATIVES

    MUHAMMAD ATHAR, ABBASI; ADNAN, AKHTAR; , AZIZ-UR-REHMAN; KHADIJA, NAFEESA; SABAHAT ZAHRA, SIDDIQUI; KHALID MOHAMMED, KHAN; MUHAMMAD, ASHRAF; SYEDA ABIDA, EJAZ.

    2013-12-01

    Full Text Available In the present work, S-substituted derivatives of 5-(2-nitrostyryl)-1,3,4-oxadiazole-2-thiol (4) were synthesized by successive conversions of 3-(2-nitrophenyl) acrylic acid (1) into its respective ester, hydrazide and 1,3,4-oxadiazole. Finally the target compounds were obtained by reaction of 5-(2- [...] nitrostyryl)-1,3,4-oxadiazole-2-thiol (4) with a series of various electrophiles, (5a-I), in NN-dimethyl formamide (DMF) in the presence of sodium hydride (NaH). The structural characterization of these newly synthesized compounds was done by IR, H-NMR, HR-MS and EI-MS spectral data. All these compounds were evaluated for their enzyme inhibitory potentials and found to exhibit broad range spectrum against acetylcholinesterase, butyrylcholinestrase and lipoxygenase enzymes.

  13. Glutamine synthetase isoforms in nitrogen-fixing soybean nodules: distinct oligomeric structures and thiol-based regulation.

    Masalkar, Pintu D; Roberts, Daniel M

    2015-01-16

    Legume root nodule glutamine synthetase (GS) catalyzes the assimilation of ammonia produced by nitrogen fixation. Two GS isoform subtypes (GS1? and GS1?) are present in soybean nodules. GS1? isoforms differ from GS1? isoforms in terms of their susceptibility to reversible inhibition by intersubunit disulfide bond formation between C159 and C92 at the shared active site at subunit interfaces. Although nodule GS enzymes share 86% amino acid sequence identity, analytical ultracentrifugation experiments showed that GS1? is a dodecamer, whereas the GS1? is a decamer. It is proposed that this difference contributes to the differential thiol sensitivity of each isoform, and that GS1?1 may be a target of thiol-based regulation. PMID:25497014

  14. Multicomponent domino reactions of hydrazinecarbodithioates: concise access to 3-substituted 5-thiol-1,3,4-thiadiazolines.

    Jia, Huihui; Feng, Huangdi; Sun, Zhihua

    2015-08-14

    Two classes of addition/cycloaddition cascade reactions of hydrazinecarbodithioate (1) have been developed under mild reaction conditions. Reaction of hydrazinecarbodithioate (1) with formaldehyde solution (2) and propiolic acid (3) gives 3-propargyl-5-thiol-2,3-dihydro-1,3,4-thiadiazoles (5) via a decarboxylative coupling/cycloaddition domino sequence. When propiolic acid (3) is switched to phenyl boronic acid (4), a petasis/cycloaddition domino reaction is instead observed, in which 3-benzyl-5-thiol-2,3-dihydro-1,3,4-thiadiazoles (6) are obtained. Both these reactions show a wide range of functional-group compatibility for propiolic acids and aryl boronic acids, and give the corresponding products in moderate to good yields. PMID:26153819

  15. X-ray magnetic circular dichroism and small angle neutron scattering study of thiol capped gold nanoparticles.

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; Pinel, E. F.; te Velthuis, S. G. E.; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian, C.; Garcia, M. A.; Univ. Complutense de Madrid; Inst. de Magnetismo Aplicado UCM; Univ. Pisa; Univ. di Padova

    2009-11-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  16. X-ray magnetic circular dichroism and small angle neutron scattering studies of thiol capped gold nanoparticles.

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; te Velthuis, S. G. E; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian Fernandez, C.; Garcia, M. A.; Univ.Complutense de Madrid; Inst. de Magnetismo Aplicado; Univ. of Pisa; Lab. di Magnetismo Molecolare

    2009-01-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  17. Study of steady state and time resolved photoluminescence of thiol capped CdS nanocrystalline powders dispersed in N,N-dimethylformamide

    The microwave (MW) assisted synthesis of thiol capped cadmium sulfide (CdS) nanocrystallites/quantum dots (QDs) was performed through the reaction of cadmium acetate with thiourea in N,N-dimethylformamide (DMF) by keeping the MW irradiation time fixed (40 s) in the presence of a thiol containing capping agent. Three capping agents, namely, benzyl mercaptan (BM), 1-butanethiol (BT) and 2-mercaptoethanol (ME) were used. The concentration of the precursors was varied to check the change in the average size of the thiol capped CdS nanocrystals formed. The nanocrystallites were characterized by usual procedure. The UV-vis absorption spectra and the photoluminescence (PL) spectra of the CdS nanocrystalline powders dispersed in DMF were studied. It was observed that with increase in concentration of the capping agent (BM), there is a shift in the nature of emission (PL) from trap associated PL to the band edge luminescence in the case of BM capped CdS nanocrystalline powders dispersed in DMF possibly due to better surface passivation. The relative PL quantum yield of the thiol capped CdS nanocrystalline powders dispersed in DMF was calculated under various experimental conditions. Time-correlated single-photon counting experiments were performed to study the time-resolved photoluminescence of the CdS nanocrystalline powders dispersed in DMF. The observed emission decay profiles have been simulated using the multiexponential model. The emission decay profiles for thiol capped CdS nanocrystalline powders dispersed in DMF depend on the nature of the capping agents (thiols) used to passivate the CdS nanocrystallites. The time resolved PL studies show that the average values of PL lifetime are related to the size and size distribution of the prepared thiol capped CdS nanocrystallites. - Highlights: ? Synthesis of thiol capped CdS quantum dots (QDs) in DMF and isolated as powders. ? Effect of concentration of reactants on the size of the thiol capped CdS QDs. ? Optical properties of thiol capped CdS QD powders dispersed in DMF. ? Higher concentration of capping reduces the surface defects. ? Higher PL quantum yield of thiol capped CdS QD powders dispersed in DMF.

  18. Thioredoxin Cross-Linking by Nitrogen Mustard in Lung Epithelial Cells: Formation of Multimeric Thioredoxin/Thioredoxin Reductase Complexes and Inhibition of Disulfide Reduction.

    Jan, Yi-Hua; Heck, Diane E; Casillas, Robert P; Laskin, Debra L; Laskin, Jeffrey D

    2015-11-16

    The thioredoxin (Trx) system, which consists of Trx and thioredoxin reductase (TrxR), is a major cellular disulfide reduction system important in antioxidant defense. TrxR is a target of mechlorethamine (methylbis(2-chloroethyl)amine; HN2), a bifunctional alkylating agent that covalently binds to selenocysteine/cysteine residues in the redox centers of the enzyme, leading to inactivation and toxicity. Mammalian Trx contains two catalytic cysteines; herein, we determined if HN2 also targets Trx. HN2 caused a time- and concentration-dependent inhibition of purified Trx and Trx in A549 lung epithelial cells. Three Trx cross-linked protein complexes were identified in both cytosolic and nuclear fractions of HN2-treated cells. LC-MS/MS of these complexes identified both Trx and TrxR, indicating that HN2 cross-linked TrxR and Trx. This is supported by our findings of a significant decrease of Trx/TrxR complexes in cytosolic TrxR knockdown cells after HN2 treatment. Using purified recombinant enzymes, the formation of protein cross-links and enzyme inhibition were found to be redox status-dependent; reduced Trx was more sensitive to HN2 inactivation than the oxidized enzyme, and Trx/TrxR cross-links were only observed using reduced enzyme. These data suggest that HN2 directly targets catalytic cysteine residues in Trx resulting in enzyme inactivation and protein complex formation. LC-MS/MS confirmed that HN2 directly alkylated cysteine residues on Trx, including Cys32 and Cys35 in the redox center of the enzyme. Inhibition of the Trx system by HN2 can disrupt cellular thiol-disulfide balance, contributing to vesicant-induced lung toxicity. PMID:26451472

  19. Regulation of ribonucleotide reductase by Spd1 involves multiple mechanisms.

    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

    2010-06-01

    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. PMID:20516199

  20. Rapid identification of aldose reductase inhibitory compounds from Perilla frutescens.

    Paek, Ji Hun; Shin, Kuk Hyun; Kang, Young-Hee; Lee, Jae-Yong; Lim, Soon Sung

    2013-01-01

    The ethyl acetate (EtOAc) soluble fraction of methanol extracts of Perilla frutescens (P. frutescens) inhibits aldose reductase (AR), the key enzyme in the polyol pathway. Our investigation of inhibitory compounds from the EtOAc soluble fraction of P. frutescens was followed by identification of the inhibitory compounds by a combination of HPLC microfractionation and a 96-well enzyme assay. This allowed the biological activities to be efficiently matched with selected HPLC peaks. Structural analyses of the active compounds were performed by LC-MS(n). The main AR inhibiting compounds were tentatively identified as chlorogenic acid and rosmarinic acid by LC-MS(n). A two-step high speed counter current chromatography (HSCCC) isolation method was developed with a solvent system of n-hexane-ethyl acetate-methanol-water at 1.5:5:1:5, v/v and 3:7:5:5, v/v. The chemical structures of the isolated compounds were determined by (1)H- and (13)C-nuclear magnetic resonance spectrometry (NMR). The main compounds inhibiting AR in the EtOAc fraction of methanol extracts of P. frutescens were identified as chlorogenic acid (2) (IC50 = 3.16 μ M), rosmarinic acid (4) (IC50 = 2.77 μ M), luteolin (5) (IC50 = 6.34 μ M), and methyl rosmarinic acid (6) (IC50 = 4.03 μ M). PMID:24308003