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

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

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

2007-01-01

2

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

Science.gov (United States)

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.

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

2000-01-01

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

Science.gov (United States)

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

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

2014-06-01

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Interaction of adenanthin with glutathione and thiol enzymes: Selectivity for thioredoxin reductase and inhibition of peroxiredoxin recycling.  

Science.gov (United States)

The diterpenoid, adenanthin, represses tumor growth and prolongs survival in mouse promyelocytic leukemia models (Liu et al., Nat. Chem. Biol. 8, 486, 2012). It was proposed that this was done by inactivating peroxiredoxins (Prxs) 1 and 2 through the formation of an adduct specifically on the resolving Cys residue. We confirmed that adenanthin underwent Michael addition to isolated Prx2, thereby inhibiting oxidation to a disulfide-linked dimer. However, contrary to the original report, both the peroxidatic and the resolving Cys residues could be derivatized. Glutathione also formed an adenanthin adduct, reacting with a second-order rate constant of 25±5M(-1)s(-1). With 50µM adenanthin, the peroxidatic and resolving Cys of Prx2 reacted with half-times of 7 and 40min, respectively, compared with 10min for GSH. When erythrocytes or Jurkat T cells were treated with adenanthin, we saw no evidence for a reaction with Prxs 1 or 2. Instead, adenanthin caused time- and concentration-dependent loss of GSH followed by dimerization of the Prxs. Prxs undergo continuous oxidation in cells and are normally recycled by thioredoxin reductase and thioredoxin. Our results indicate that Prx reduction was inhibited. We observed rapid inhibition of purified thioredoxin reductase (half-time 5min with 2µM adenanthin) and in cells, thioredoxin reductase was much more sensitive than GSH and loss of both preceded accumulation of oxidized Prxs. Thus, adenanthin is not a specific Prx inhibitor, and its reported antitumor and anti-inflammatory effects are more likely to involve more general inhibition of thioredoxin and/or glutathione redox pathways. PMID:25289458

Soethoudt, Marjolein; Peskin, Alexander V; Dickerhof, Nina; Paton, Louise N; Pace, Paul E; Winterbourn, Christine C

2014-12-01

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Molecular cloning and expression analysis of interferon-gamma inducible lysosomal thiol reductase (GILT)-like cDNA from disk abalone (Haliotis discus discus).  

Science.gov (United States)

Interferon Gamma (IFN-gamma) Inducible Lysosomal Thiol reductase (GILT) has been described as a key enzyme in processing and presentation of major histocompatibility complex (MHC) class II restricted antigen (Ag) by catalyzing disulfide bond (S-S) reduction in mammals. Abalone GILT-like (AbGILT) full-length cDNA was isolated from the normalized disk abalone cDNA library. The 807-bp AbGILT cDNA consists of an open reading frame of 684-bp, encoding 228 amino acid residues. The predicted AbGILT protein has a molecular weight of 25kDa and an isoelectric point of 7.8. The N-terminus of the AbGILT was found to have a putative signal peptide with a cleavage site amino acid position at 19-20. AbGILT contains two active site C-XX-C motifs, ((23)CLDC(26) and (46)CPYC(49)) which motif is highly conserved in GILT protein family. AbGILT exhibited a characteristic GILT signature sequence (92)CQHGX(2)ECX(2)NX(4)C(107) and 12 cysteine residues representing 5% in the mature peptide. Phylogenetic analysis showed that AbGILT has been derived from a common ancestor with other GILT proteins. RT-PCR results showed that AbGILT expression was up-regulated in the gill, mantle and digestive tract 24h post injection of phytohemagglutinin (PHA) while Vibrio alginolyticus up-regulation appeared in the gill and digestive tract after 48h. In contrast, AbGILT expression was not up-regulated by poly inosinic-cytidylic acid (poly I:C) during the 48h induction. However, AbGILT was constitutively expressed in gill, mantle, and digestive tract tissues suggesting that it may maintain first line of innate immune defense at basal level in disk abalone. PMID:17599346

De Zoysa, Mahanama; Lee, Jehee

2007-11-01

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Identification of interferon-?-inducible-lysosomal thiol reductase (GILT) gene in goldfish (Carassius auratus) and its immune response to LPS challenge.  

Science.gov (United States)

The interferon-?-inducible lysosomal thiol reductase (GILT) has been demonstrated to play an important role in the processing and presentation of MHC class II restricted antigen (Ag) by catalyzing disulfide bond reduction. In this study, we cloned a GILT gene homolog from goldfish (designated gGILT), a kind of precious freshwater fish with high market value. The open reading frame of gGILT consists of 756 bases encoding a protein of 251 amino acids with an estimated molecular mass of 27.8 kDa and a theoretical isoelectric point of 5.24. The deduced protein possesses the typical structural features of known GILT proteins, including an active-site motif, a GILT signature sequence, and 10 conserved cysteines. RT-PCR results showed that gGILT and gIFN-? (goldfish IFN-?) mRNA were expressed in a tissue-specific manner and obviously up-regulated in splenocytes and the cells from head kidney after induction with LPS. Recombinant gGILT fused with His6 tag was efficiently expressed in Escherichia coli BL21 (DE3) and purified by Ni-NTA affinity chromatography. Further study revealed that gGILT was capable of catalyzing the reduction of the interchain disulfide bonds from intact IgG. This study shows that gGILT may be involved in the immune response to bacteria challenge and maintain first line of innate immune defense at basal level in goldfish. It also provides the basis for investigating on the role of GILT using goldfish as an animal model. PMID:25447639

Li, Jian Feng; Li, Jian; Wang, Zhi Guo; Liu, Hong Zhen; Zhao, You Long; Zhang, Jin Xi; Zhang, Shuang Quan; Liu, Jun Ping

2015-02-01

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Direct and nitroxyl (HNO)-mediated reactions of acyloxy nitroso compounds with the thiol-containing proteins glyceraldehyde 3-phosphate dehydrogenase and alkyl hydroperoxide reductase subunit C.  

Science.gov (United States)

Nitroxyl (HNO) reacts with thiols, and this reactivity requires the use of donors with 1-nitrosocyclohexyl acetate, pivalate, and trifluoroacetate, forming a new group. These acyloxy nitroso compounds inhibit glyceraldehyde 3-phosphate dehydrogenase (GAPDH) by forming a reduction reversible active site disulfide and a reduction irreversible sulfinic acid or sulfinamide modification at Cys244. Addition of these acyloxy nitroso compounds to AhpC C165S yields a sulfinic acid and sulfinamide modification. A potential mechanism for these transformations includes nucleophilic addition of the protein thiol to a nitroso compound to yield an N-hydroxysulfenamide, which reacts with thiol to give disulfide or rearranges to sulfinamides. Known HNO donors produce the unsubstituted protein sulfinamide as the major product, while the acetate and pivalate give substituted sulfinamides that hydrolyze to sulfinic acids. These results suggest that nitroso compounds form a general class of thiol-modifying compounds, allowing their further exploration. PMID:23895568

Mitroka, Susan; Shoman, Mai E; DuMond, Jenna F; Bellavia, Landon; Aly, Omar M; Abdel-Aziz, Mohamed; Kim-Shapiro, Daniel B; King, S Bruce

2013-09-12

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

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

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

2009-01-01

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

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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...

Jo?nsson, Thomas J.; Ellis, Holly R.; Poole, Leslie B.

2007-01-01

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Postischemic Deactivation of Cardiac Aldose Reductase: ROLE OF GLUTATHIONE S-TRANSFERASE P AND GLUTAREDOXIN IN REGENERATION OF REDUCED THIOLS FROM SULFENIC ACIDS*  

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Aldose reductase (AR) is a multifunctional enzyme that catalyzes the reduction of glucose and lipid peroxidation-derived aldehydes. During myocardial ischemia, the activity of AR is increased due to the oxidation of its cysteine residues to sulfenic acids. It is not known, however, whether the activated, sulfenic form of the protein (AR-SOH) is converted back to its reduced, unactivated state (AR-SH). We report here that in perfused mouse hearts activation of AR during 15 min of global ischem...

Wetzelberger, Karin; Baba, Shahid P.; Thirunavukkarasu, Mahesh; Ho, Ye-shih; Maulik, Nilanjana; Barski, Oleg A.; Conklin, Daniel J.; Bhatnagar, Aruni

2010-01-01

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Thiols, thiol depletion, and thermosensitivity  

International Nuclear Information System (INIS)

Hyperthermia sensitization or tolerance is subject to cellular events that may occur at membrane, nuclear, and cytoplasmic sites. We have studied the effects of elevated temperatures on the oxidative-reductive state of the cell by measuring and altering glutathione (GSH) concentrations. GSH plays a pivotal role in maintaining the overall cellular redox state and detoxification of peroxides. Continuous heating at 42.50C or acute exposure at 430C or 45.50C resulted in rapid elevations of cellular GSH to 120 to 200% of control values. Qualitatively, the more severe the heat exposure, the quicker the maximal GSH levels are attained. Ethanol, a compound that also induces thermal tolerance, likewise increases intracellular GSH concentrations. GSH depletion by two different modalities, diethylmaleate (DEM) and buthionine sulfoximine (BSO), results in thermal sensitization. It was demonstrated that once thermotolerance has been induced, depletion of GSH has minimal effects on subsequent heating and thermotolerance. Heat shock protein (HSP) synthesis is lessened by treatment with buthionine sulfoximine; the extent of the decrease in HSP production correlates with the decrease in thermotolerance. A proposed mechanism of peroxide-induced cell damage is suggested by exogenous thiols, as well as an involvement of GSH in the initial aspects of thermotolerance induction

12

Thiol biochemistry of prokaryotes  

Science.gov (United States)

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

Fahey, Robert C.

1986-01-01

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Enzymatic basis of thiol-stimulated secretion of porphyrins by Escherichia coli.  

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1-Thioglycerol (TG) stimulates the synthesis of porphyrin in aerobically growing Escherichia coli. Here the levels of delta-aminolevulinate biosynthetic enzymes in untreated and TG-treated E. coli THU and PUC2 (a mutant of THU which overproduces porphyrins in the presence of thiols) cells were determined. TG treatment elevated the activity of glutamyl-tRNA reductase in both strains. The increased activity was not caused by activation of preexisting enzymes by thiols or by oxidizing agents but...

Javor, G. T.; Febre, E. F.

1992-01-01

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

Science.gov (United States)

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

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

2015-02-01

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Composite materials having thiol groups  

Energy Technology Data Exchange (ETDEWEB)

A composite material having thiol groups comprises a rigid support material. The composite material may comprise a deformable gel (eg agarose) having thiol groups retained within the pore structure of a porous rigid support material (e.g. Kieselghur). The particles of composite material are used to prepare a radioactive gold isotope from a mercury 'parent' isotope. (author).

Rosevear, A.

1985-07-24

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Composite materials having thiol groups  

International Nuclear Information System (INIS)

A composite material having thiol groups comprises a rigid support material. The composite material may comprise a deformable gel (eg agarose) having thiol groups retained within the pore structure of a porous rigid support material (e.g. Kieselghur). The particles of composite material are used to prepare a radioactive gold isotope from a mercury 'parent' isotope. (author)

17

Thiols and radiosensitivity  

International Nuclear Information System (INIS)

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

18

Thiol reactive probes and chemosensors.  

Science.gov (United States)

Thiols are important molecules in the environment and in biological processes. Cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H(2)S) 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 H(2)S 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. PMID:23202239

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

2012-01-01

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Thiol Reactive Probes and Chemosensors  

Directory of Open Access Journals (Sweden)

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

Binghe Wang

2012-11-01

20

Mammalian thioredoxin reductase 1: roles in redox homoeostasis and characterization of cellular targets  

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The classical Trx (thioredoxin) system, composed of TR (Trx reductase), Trx and NADPH, defines a major pathway of cellular thiol-based redox regulation. Three TRs have been identified in mammals: (i) cytosolic TR1, (ii) mitochondrial TR3 and (iii) testes-specific TGR (Trx-glutathione reductase). All three are selenocysteine-containing enzymes with broad substrate specificity in in vitro assays, but which protein substrates are targeted by TRs in vivo is not well understood. In the present stu...

Turanov, Anton A.; Kehr, Sebastian; Marino, Stefano M.; Yoo, Min-hyuk; Carlson, Bradley A.; Hatfield, Dolph L.; Gladyshev, Vadim N.

2010-01-01

 
 
 
 
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A crucial role for thiol antioxidants in estrogen-deficiency bone loss  

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The mechanisms through which estrogen prevents bone loss are uncertain. Elsewhere, estrogen exerts beneficial actions by suppression of reactive oxygen species (ROS). ROS stimulate osteoclasts, the cells that resorb bone. Thus, estrogen might prevent bone loss by enhancing oxidant defenses in bone. We found that glutathione and thioredoxin, the major thiol antioxidants, and glutathione and thioredoxin reductases, the enzymes responsible for maintaining them in a reduced state, fell substantia...

Lean, Jenny M.; Davies, Julie T.; Fuller, Karen; Jagger, Christopher J.; Kirstein, Barrie; Partington, Geoffrey A.; Urry, Zoe? L.; Chambers, Timothy J.

2003-01-01

22

Quantification of thiols and disulfides  

DEFF Research Database (Denmark)

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

Winther, Jakob R.; Thorpe, Colin

2014-01-01

23

Catalytic asymmetric synthesis of thiols.  

Science.gov (United States)

The synthesis of enantiopure thiols is of significant interest for industrial and academic applications. However, direct asymmetric approaches to free thiols have previously been unknown. Here we describe a novel organocascade that is catalyzed by a confined chiral phosphoric acid and furnishes O-protected ?-hydroxythiols with excellent enantioselectivities. The method relies on an asymmetric thiocarboxylysis of meso-epoxides, followed by an intramolecular trans-esterification reaction. By varying the reaction conditions, the intermediate thioesters can also be obtained chemoselectively and enantioselectively. PMID:25492723

Monaco, Mattia Riccardo; Prévost, Sébastien; List, Benjamin

2014-12-10

24

Thiol density dependent classical potential for methyl-thiol on a Au(111) surface  

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A new classical potential for methyl-thiol on a Au(111) surface has been developed using density functional theory electronic structure calculations. Energy surfaces between methyl-thiol and a gold surface were investigated in terms of symmetry sites and thiol density. Geometrical optimization was employed over all the configurations while minimum energy and thiol height were determined. Finally, a new interatomic potential has been generated as a function of thiol density, ...

Jeon, Byoungseon; Kress, Joel D.; Grønbech-jensen, Niels

2007-01-01

25

Structural and Mechanistic Insights into Unusual Thiol Disulfide Oxidoreductase  

Science.gov (United States)

Cytoplasmic desulfothioredoxin (Dtrx) from the anaerobe Desulfovibrio vulgaris Hildenborough has been identified as a new member of the thiol disulfide oxidoreductase family. The active site of Dtrx contains a particular consensus sequence, CPHC, never seen in the cytoplasmic thioredoxins and generally found in periplasmic oxidases. Unlike canonical thioredoxins (Trx), Dtrx does not present any disulfide reductase activity, but it presents instead an unusual disulfide isomerase activity. We have used NMR spectroscopy to gain insights into the structure and the catalytic mechanism of this unusual Dtrx. The redox potential of Dtrx (?181 mV) is significantly less reducing than that of canonical Trx. A pH dependence study allowed the determination of the pKa of all protonable residues, including the cysteine and histidine residues. Thus, the pKa values for the thiol group of Cys31 and Cys34 are 4.8 and 11.3, respectively. The His33 pKa value, experimentally determined for the first time, differs notably as a function of the redox states, 7.2 for the reduced state and 4.6 for the oxidized state. These data suggest an important role for His33 in the molecular mechanism of Dtrx catalysis that is confirmed by the properties of mutant DtrxH33G protein. The NMR structure of Dtrx shows a different charge repartition compared with canonical Trx. The results presented are likely indicative of the involvement of this protein in the catalysis of substrates specific of the anaerobe cytoplasm of DvH. The study of Dtrx is an important step toward revealing the molecular details of the thiol-disulfide oxidoreductase catalytic mechanism. PMID:22128175

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

2012-01-01

26

Protein thiol modifications visualized in vivo  

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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 sna...

Leichert Lars I; Jakob Ursula

2004-01-01

27

Investigations of thiol-modified phenol derivatives for the use in thiol–ene photopolymerizations  

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Thiol–ene photopolymerizations gain a growing interest in academic research. Coatings and dental restoratives are interesting applications for thiol–ene photopolymerizations due to their unique features. In most studies the relative flexible and hydrophilic ester derivative, namely pentaerythritoltetra(3-mercaptopropionate) (PETMP), is investigated as the thiol component. Thus, in the present study we are encouraged to investigate the performance of more hydrophobic ester-free thiol-modif...

Reinelt, Sebastian; Tabatabai, Monir; Fischer, Urs Karl; Moszner, Norbert; Utterodt, Andreas; Ritter, Helmut

2014-01-01

28

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

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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.

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

2010-01-01

29

Flow cytometry techniques for studying cellular thiols  

International Nuclear Information System (INIS)

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

30

Asymmetric synthesis of tertiary thiols and thioethers  

Directory of Open Access Journals (Sweden)

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

Paul MacLellan

2011-05-01

31

Inactivation of Penicillins by Thiol Broth  

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Thiol broth with sodium polyanetholesulfonate inactivated penicillin G, carbenicillin, nafcillin, oxacillin, and gentamicin, but had no effect on cephalothin, cefoxitin, clindamycin, chloramphenicol, erythromycin, and tetracycline. Only Thiol broth was capable of this inactivation, which was not influenced by the presence of blood.

Murray, Patrick R.; Niles, Ann C.

1982-01-01

32

Investigation of reactions postulated to occur during inhibition of ribonucleotide reductases by 2?-azido-2?-deoxynucleotides  

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Model 3?-azido-3?-deoxynucleosides with thiol or vicinal dithiol substituents at C2? or C5? were synthesized to study reactions postulated to occur during inhibition of ribonucleotide reductases by 2?-azido-2?-deoxynucleotides. Esterification of 5?-(tert-butyldiphenylsilyl)-3?-azido-3?-deoxyadenosine and 3?-azido-3?-deoxythymidine (AZT) with 2,3-S-isopropylidene-2,3-dimercaptopropanoic acid or N-Boc-S-trityl-L-cysteine and deprotection gave 3?-azido-3?-deoxy-2?-O-(...

Dang, Thao P.; Sobczak, Adam J.; Mebel, Alexander M.; Chatgilialoglu, Chryssostomos; Wnuk, Stanislaw F.

2012-01-01

33

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

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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...

Myers, Charles R.; Myers, Judith M.

2009-01-01

34

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

International Nuclear Information System (INIS)

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

35

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

Science.gov (United States)

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

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

1998-03-01

36

Identification of S-nitroso-CoA reductases that regulate protein S-nitrosylation.  

Science.gov (United States)

Coenzyme A (CoA) mediates thiol-based acyl-group transfer (acetylation and palmitoylation). However, a role for CoA in the thiol-based transfer of NO groups (S-nitrosylation) has not been considered. Here we describe protein S-nitrosylation in yeast (heretofore unknown) that is mediated by S-nitroso-CoA (SNO-CoA). We identify a specific SNO-CoA reductase encoded by the alcohol dehydrogenase 6 (ADH6) gene and show that deletion of ADH6 increases cellular S-nitrosylation and alters CoA metabolism. Further, we report that Adh6, acting as a selective SNO-CoA reductase, protects acetoacetyl-CoA thiolase from inhibitory S-nitrosylation and thereby affects sterol biosynthesis. Thus, Adh6-regulated, SNO-CoA-mediated protein S-nitrosylation provides a regulatory mechanism paralleling protein acetylation. We also find that SNO-CoA reductases are present from bacteria to mammals, and we identify aldo-keto reductase 1A1 as the mammalian functional analog of Adh6. Our studies reveal a novel functional class of enzymes that regulate protein S-nitrosylation from yeast to mammals and suggest that SNO-CoA-mediated S-nitrosylation may subserve metabolic regulation. PMID:25512491

Anand, Puneet; Hausladen, Alfred; Wang, Ya-Juan; Zhang, Guo-Fang; Stomberski, Colin; Brunengraber, Henri; Hess, Douglas T; Stamler, Jonathan S

2014-12-30

37

Evaluation and Control of Thiol-ene/Thiol-epoxy Hybrid Networks  

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The development of thiol-ene/thiol-epoxy hybrid networks offers the advantage of tailorable polymerization kinetics while producing a highly crosslinked, high Tg polymer that has significantly reduced shrinkage stress. Stoichiometric mixtures of pentaerythritol tetra(3-mercaptopropionate) (PETMP)/triallyl-1,3,5-triazine-2,4,6-trione (TATATO) (thiol-ene, mixture 1) and PETMP/bisphenol a diglycidyl ether (BADGE) (thiol-epoxy, mixture 2) were prepared and hybrid mixtures of 75/25, 50/50, 25/75, ...

Carioscia, Jacquelyn A.; Stansbury, Jeffrey W.; Bowman, Christopher N.

2007-01-01

38

Evolution of thiol protective systems in prokaryotes  

Science.gov (United States)

Biological thiols are essential elements in most aspects of cell function but undergo rapid oxidation to disulfides in the presence of oxygen. The evolution of systems to protect against such oxygen toxicity was essential to the emergence of aerobic life. The protection system used by eukaryotes is based upon glutathione (GSH) and GSH-dependent enzymes but many bacteria lack GSH and apparently use other mechanisms. The objective of this research is to elaborate the thiol protective mechanisms employed by prokaryotes of widely divergent evolutionary origin and to understand why GSH became the central thiol employed in essentially all higher organisms. Thiol-selective fluorescent labeling and HPLC analysis has been used to determine key monothiol components.

Fahey, R. C.; Newton, G. L.

1986-01-01

39

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

International Nuclear Information System (INIS)

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

40

Photopatterned Thiol Surfaces for Biomolecule Immobilization  

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The ability to pattern small molecules and proteins on artificial surfaces is of importance for the development of new tools including tissue engineering, cell-based drug screening, and cell-based sensors. We describe here a novel “caged” thiol-mediated strategy for the fabrication of planar substrates patterned with biomolecules using photolithography. A thiol-bearing phosphoramidite (3-(2’-nitrobenzyl)thiopropyl (NBTP) phosphoramidite) was synthesized and coupled to a hydroxyl-termina...

Chen, Siyuan; Smith, Lloyd M.

2009-01-01

 
 
 
 
41

Reaction Kinetics and Reduced Shrinkage Stress of Thiol-Yne-Methacrylate and Thiol-Yne-Acrylate Ternary Systems  

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Thiol-yne-methacrylate and thiol-yne-acrylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol-yne and (meth)acrylate systems. Both thiol-yne-methacrylate and thiol-yne-acrylate systems were demonstrated to reduce polymerization induced shrinkage stress while simultaneously achieving high glass transition temperatures (Tg) and modulius. Formulations with 70 wt% methacrylate increased the Tg from 51 ± 2 to 75 ± 1 ?...

Ye, Sheng; Cramer, Neil B.; Smith, Ian R.; Voigt, Katerina R.; Bowman, Christopher N.

2011-01-01

42

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

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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...

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

2010-01-01

43

Roles of thiols in cellular radiosensitivity  

Energy Technology Data Exchange (ETDEWEB)

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

Durand, R.E.

1984-08-01

44

Photopolymerized Thiol-Ene Systems as Shape Memory Polymers  

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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...

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

2010-01-01

45

Ketopantoyl lactone reductase is a conjugated polyketone reductase.  

Science.gov (United States)

Ketopantoyl lactone reductase (EC 1.1.1.168) of Saccharomyces cerevisiae was found to catalyze the reduction of a variety of natural and unnatural conjugated polyketone compounds and quinones, such as isatin, ninhydrin, camphorquinone and beta-naphthoquinone in the presence of NADPH. 5-Bromoisatin is the best substrate for the enzyme (Km = 3.1 mM; Vmax = 650 mumol/min/mg). The enzyme is inhibited by quercetin, and several polyketones. These results suggest that ketopantoyl lactone reductase is a carbonyl reductase which specifically catalyzes the reduction of conjugated polyketones. PMID:2656398

Hata, H; Shimizu, S; Hattori, S; Yamada, H

1989-03-01

46

Total Thiols: Biomedical Importance And Their Alteration In Various Disorders  

Directory of Open Access Journals (Sweden)

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.

Mungli Prakash

2009-09-01

47

Oligonucleotide cyclization: The thiol-maleimide reaction revisited  

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

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

2013-01-01

48

Synthesis of bisnaphthyl based thiol stabilized gold nanoparticles  

International Nuclear Information System (INIS)

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

49

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

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

Fomenko, Dmitri E.; Gladyshev, Vadim N.

2012-01-01

50

Investigation of novel thiol "click" reactions  

Science.gov (United States)

The research herein describes the nucleophile catalyzed thio-Michael addition to electron poor enes as a integral reaction in the canon of thiol-ene click reactions. This dissertation includes chapters of the kinetics and spectroscopic evaluation of the nucleophile catalyzed thio-Michael addition reaction and resulting products; the use of nucleophile catalyzed thio-Michael addition for the rapid synthesis of star polymers; and the physical and mechanical properties of networks prepared with a combination of the photo-cured and nucleophile cured reactions of multi-acrylates with multi-functional thiols. The first fundamental study discusses a proposed anionic chain mechanism for the nucleophile catalyzed thio-Michael addition to electron poor alkenes. Traditional base catalyzed mechanisms show the deprotonation of the thiol by a weak base such as triethyl amine. Results show that nucleophilic amines, such as hexyl amine, with similar pKa values as the weak bases have faster rates of reaction, indicating that base strength alone is not responsible for the apparent increase in rates. Results demonstrate that the effect of nucleophilicity has a greater role than basicity (pKa) in the rates of reaction. An anionic chain mechanism is proposed involving the initiation of the thio-Michael reaction by an initial attack of a nucleophile onto an electron poor double bond creating a super-strong enolate anion which carries out the subsequent base catalyzed thio-Michael addition. The second study reports the facile formation of star polymers using the nucleophile catalyzed thio-Michael addition reaction of polymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and a tri-acrylate monomer. The nucleophilic catalyst employed for the thio-Michael addition reaction has shown to have a dual purpose: to catalyze the Michael addition and to prevent the disulfide formation commonly seen in the reduction step of the RAFT end group. Acrylates are commonly used for the preparation of polymer networks due to their wide commercial availability, tunable mechanical properties, and sensitivity to photopolymerization. Photo-cured multi-acrylate systems produce films with inhomogeneous micro-structures leading to broad glass transition temperatures (Tg). Incorporation of thiols into these systems narrows the Tgs but quantitative addition (1 to 1) of thiol to acrylate does not occur due to the competitive acrylate homopolymerization. The nucleophile catalyzed thio-Michael addition reaction promotes the quantitative addition of thiols to acrylates resulting in very narrow Tgs. The third study discusses the use of sequential thio-Michael reaction followed by the photo-cured reaction. This process allows tunability of mechanical and physical properties of resulting films. In the fourth study, the nucleophile catalyzed thio-Michael addition reaction is used for preparation of multi-functional alkynes. Alkynes, like alkenes, react rapidly and quantitatively with thiols in a photocured system in a 1:2 ratio. A series of poly-functional branched materials was prepared by clicking two thiol groups to one terminal alkyne proceeded quantitatively, in the absence of solvent, rapidly and with no evidence of side products. The fifth study demonstrates the preparation of a series of multi-functional alkyne monomers (f=4,6,8) that were subsequently photopolymerized with a series of multifunctional thiols (f=2,3,4). Mechanical and physical properties showed an increasing correlation between gel point and functionality. Additionally, this study demonstrated the utility of tailoring the Tg values by increasing the functionality of starting monomers. High sulfur content materials have shown to have high refractive index values. In the final study, networks were prepared from commercially available dialkyne and dithiols, consisting only of sulfur and hydrocarbon. Sulfur content in some films reached nearly 50% and, as a result, refractive index values were determined to be greater than 1.65. Data from this study shows a linear relation

Chan, Justin William

51

Purification and characterization of a novel enoyl coenzyme A reductase from Streptomyces collinus.  

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A novel NADPH-dependent enoyl reductase, catalyzing the conversion of 1-cyclohexenylcarbonyl coenzyme A (1-cyclohexenylcarbonyl-CoA) to cyclohexylcarbonyl-CoA, was purified to homogeneity from Streptomyces collinus. This enzyme, a dimer with subunits of identical M(r) (36,000), exhibits a Km of 1.5 +/- 0.3 microM for NADPH and 25 +/- 3 microM for 1-cyclohexenylcarbonyl-CoA. It has a pH optimum of 7.5, is most active at 30 degrees C, and is inhibited by both divalent cations and thiol reagents...

Reynolds, K. A.; Wang, P.; Fox, K. M.; Speedie, M. K.; Lam, Y.; Floss, H. G.

1992-01-01

52

Functional and Structural Characterization of a Thiol Peroxidase from Mycobacterium tuberculosis  

Energy Technology Data Exchange (ETDEWEB)

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.

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

2006-01-01

53

Electrochemical detection of thiols in biological media.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The utilisation of catechol as an electrochemical indicator for the presence of sulphydryl thiols (RSH) has been investigated. The electrochemical oxidation of the catechol within tissue culture media was examined with the influence exerted on the redox chemistry by cysteine evaluated in terms of the development of an analytical protocol. The electro-generation of o-quinone was found to be followed by a 1,4-addition reaction with available cysteine such that an increase in the current, attrib...

Lawrence, Ns; Davis, J.; Compton, Rg

2001-01-01

54

Thiol-derivatized minihepcidins retain biological activity.  

Science.gov (United States)

Minihepcidins are small peptides that mimic biological activity of the iron-regulatory hormone hepcidin. Structurally, they contain thiol-free-cysteine residue in position 7 which is crucial for their bioactivity. Nonetheless, free sulfhydryl group is not desirable in pharmaceutical entities as it may lead to dermatological side effects. Moreover free thiol moiety is quite reactive and depending on conditions/reagents may be alkylated and/or oxidized giving various Cys-derivatives: S-alkyl cysteines, sulfoxides, sulfones, disulfides, cysteinesulfinic and cysteic acids. To limit such reactivity and maintain bioactivity of minihepcidin(s) we used thiol-protection strategy based on activated vinyl thioethers. Novel S-protected analogs of physiologically active minihepcidin PR73 were synthesized and tested in vitro showing activity comparable to parental molecule. The most active compound, PR73SH was also tested in vivo showing activity profile analogous to PR73. Collectively, our findings suggest that S-vinyl-derivatization of minihepcidin(s) may be a suitable approach in the development of physiologically active agonists of hepcidin. PMID:25599838

Fung, Eileen; Chua, Kristine; Ganz, Tomas; Nemeth, Elizabeta; Ruchala, Piotr

2015-02-15

55

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

International Nuclear Information System (INIS)

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

56

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

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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...

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

1993-01-01

57

Arginine 60 in the ArsC arsenate reductase of E. coli plasmid R773 determines the chemical nature of the bound As(III) product  

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Arsenic is a ubiquitous environmental toxic metal. Consequently, organisms detoxify arsenate by reduction to arsenite, which is then excreted or sequestered. The ArsC arsenate reductase from Escherichia coli plasmid R773, the best characterized arsenic-modifying enzyme, has a catalytic cysteine, Cys 12, in the active site, surrounded by an arginine triad composed of Arg 60, Arg 94, and Arg 107. During the reaction cycle, the native enzyme forms a unique monohydroxyl Cys 12-thiol-arsenite addu...

Demel, Srini; Shi, Jin; Martin, Philip; Rosen, Barry P.; Edwards, Brian F. P.

2004-01-01

58

Tunable degradation of maleimide-thiol adducts in reducing environments  

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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...

Baldwin, Aaron D.; Kiick, Kristi L.

2011-01-01

59

Thiol Modification By Pharmacologically Active Agents of the Diazeniumdiolate Class  

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Promising drug candidates of the diazeniumdiolate (NONOate) chemical family include several types of thiol modification among their mechanisms of action: 1) drugs designed to release nitric oxide (NO) on reaction with the thiol group of glutathione (GSH) arylate the GSH, a step that removes reducing equivalents from the cell; (2) a similar reaction of the drug with the thiol group of a protein changes its structure, leading to potentially impaired function and cell death; (3) the NO generated...

Maciag, Anna E.; Holland, Ryan J.; Saavedra, Joseph E.; Chakrapani, Harinath; Shami, Paul J.; Keefer, Larry K.

2012-01-01

60

Interaction Profile of Diphenyl Diselenide with Pharmacologically Significant Thiols  

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Diphenyl diselenide has shown interesting biological activities in various free-radical-induced damage models and can be considered as a potential candidate drug against oxidative stress. Apart from its anti-oxidant activity, this compound can oxidize various thiols. However there are no detailed studies in the literature about the thiol oxidase-like activity of this compound against biologically significant mono and di-thiols with respect to various pH conditions. Keeping in mind the scarcit...

Joao Batista Teixeira Rocha; Waseem Hassan

2012-01-01

 
 
 
 
61

Thiols and antioxidants in radiobiology: chemical and bioanalytical problems  

International Nuclear Information System (INIS)

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

62

Crystal-bound vs surface-bound thiols on nanocrystals.  

Science.gov (United States)

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

Turo, Michael J; Macdonald, Janet E

2014-10-28

63

Ferredoxin-NADP+ Reductase from Pseudomonas putida Functions as a Ferric Reductase?  

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Pseudomonas putida harbors two ferredoxin-NADP+ reductases (Fprs) on its chromosome, and their functions remain largely unknown. Ferric reductase is structurally contained within the Fpr superfamily. Interestingly, ferric reductase is not annotated on the chromosome of P. putida. In an effort to elucidate the function of the Fpr as a ferric reductase, we used a variety of biochemical and physiological methods using the wild-type and mutant strains. In both the ferric reductase and flavin redu...

Yeom, Jinki; Jeon, Che Ok; Madsen, Eugene L.; Park, Woojun

2008-01-01

64

Mutation and Mutagenesis of thiol peroxidase of Escherichia coli and a new type of thiol peroxidase family.  

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A novel thioredoxin-linked thiol peroxidase (Px) from Escherichia coli has been reported previously (M. K. Cha, H. K. Kim, and I. H. Kim, J. Biol. Chem. 270:28635-28641, 1995). In an attempt to perform physiological and biochemical characterizations of the thiol Px, a thiol Px null (tpx) mutant and a functional-residue mutant of thiol Px were produced. The tpx mutant was viable in aerobic culture but grew more slowly than the wild-type cells. The difference in growth rate became more pronounc...

Cha, M. K.; Kim, H. K.; Kim, I. H.

1996-01-01

65

Thiol groups of gizzard myosin heavy chains  

International Nuclear Information System (INIS)

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

66

Long-term stabilization of maleimide-thiol conjugates.  

Science.gov (United States)

Michael-addition of a thiol to a maleimide is commonly used for bioconjugation of drugs to macromolecules. Indeed, both current FDA-approved antibody-drug conjugates-Brentuximab vedotin and Trastuzumab emtansine-and one approved PEGylated conjugate-Cimzia-contain a thiol-maleimide adduct. However, the ultimate in vivo fate of such adducts is to undergo disruptive cleavage by thiol exchange or stabilizing ring opening. Therapeutic efficacy of a conjugate can be compromised by thiol exchange and the released drug may show toxicities. However, if the succinimide moiety of a maleimide-thiol conjugate is hydrolyzed, the ring-opened product is stabilized toward cleavage. We determined rates of ring-opening hydrolysis and thiol exchange of a series of N-substituted succinimide thioethers formed by maleimide-thiol conjugation. Ring-opening of conjugates prepared with commonly used maleimides were too slow to serve as prevention against thiol exchange. However, ring-opening rates are greatly accelerated by electron withdrawing N-substituents, and ring-opened products have half-lives of over two years. Thus, conjugates made with electron-withdrawing maleimides may be purposefully hydrolyzed to their ring-opened counterparts in vitro to ensure in vivo stability. PMID:25494821

Fontaine, Shaun D; Reid, Ralph; Robinson, Louise; Ashley, Gary W; Santi, Daniel V

2015-01-21

67

Organocatalytic enantioselective addition of thiols to ketimines derived from isatins.  

Science.gov (United States)

The first catalytic enantioselective addition of thiols to ketimines derived from isatins has been developed. Excellent yields and enantioselectivities were observed for the reaction of various ketimines and thiols using a cinchona alkaloid sulfonamide catalyst. Both enantiomers of products could be obtained by using pseudoenantiomeric chiral catalysts. PMID:25526427

Nakamura, Shuichi; Takahashi, Shun; Nakane, Daisuke; Masuda, Hideki

2015-01-01

68

Transition metal photoredox catalysis of radical thiol-ene reactions.  

Science.gov (United States)

We describe the anti-Markovnikov hydrothiolation of olefins using visible-light-absorbing transition metal photocatalysts. The key thiyl radical intermediates are generated upon quenching of photoexcited Ru*(bpz)3(2) with a variety of thiols. The adducts of a wide variety of olefins and thiols are formed in excellent yield (73-99%). PMID:23094660

Tyson, Elizabeth L; Ament, Michael S; Yoon, Tehshik P

2013-03-01

69

Quantifying thiol-gold interactions towards the efficient strength control  

Science.gov (United States)

The strength of the thiol-gold interactions provides the basis to fabricate robust self-assembled monolayers for diverse applications. Investigation on the stability of thiol-gold interactions has thus become a hot topic. Here we use atomic force microscopy to quantify the stability of individual thiol-gold contacts formed both by isolated single thiols and in self-assembled monolayers on gold surface. Our results show that the oxidized gold surface can enhance greatly the stability of gold-thiol contacts. In addition, the shift of binding modes from a coordinate bond to a covalent bond with the change in environmental pH and interaction time has been observed experimentally. Furthermore, isolated thiol-gold contact is found to be more stable than that in self-assembled monolayers. Our findings revealed mechanisms to control the strength of thiol-gold contacts and will help guide the design of thiol-gold contacts for a variety of practical applications.

Xue, Yurui; Li, Xun; Li, Hongbin; Zhang, Wenke

2014-07-01

70

Urinary Excretion of Thiol Compounds in Patients with Rheumatoid Arthritis  

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The objective of the present study was to assess the excretion of urinary thiol compounds in patients with active and inactive rheumatoid arthritis (RA). Urinary thiol compounds were measured by the method of Kokonov (M. T. Kokonov, Lab. Delo 5:273–276, 1965) in 51 outpatients with active and inactive RA. Those with active disease had significantly higher levels of urinary thioamine excretion.

Rojkovich, Bernadette; Nagy, Eszter; Pro?hle, Tama?s; Poo?r, Gyula; Gergely, Pe?ter

1999-01-01

71

Cellular thiols: Importance in misonidazole metabolism  

International Nuclear Information System (INIS)

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

72

Acetaminophen reactive intermediates target hepatic thioredoxin reductase.  

Science.gov (United States)

Acetaminophen (APAP) is metabolized in the liver to N-acetyl-p-benzoquinone imine (NAPQI), an electrophilic metabolite known to bind liver proteins resulting in hepatotoxicity. Mammalian thioredoxin reductase (TrxR) is a cellular antioxidant containing selenocysteine (Sec) in its C-terminal redox center, a highly accessible target for electrophilic modification. In the present study, we determined if NAPQI targets TrxR. Hepatotoxicity induced by APAP treatment of mice (300 mg/kg, i.p.) was associated with a marked inhibition of both cytosolic TrxR1 and mitochondrial TrxR2 activity. Maximal inhibition was detected at 1 and 6 h post-APAP for TrxR1 and TrxR2, respectively. In purified rat liver TrxR1, enzyme inactivation was correlated with the metabolic activation of APAP by cytochrome P450, indicating that enzyme inhibition was due to APAP-reactive metabolites. NAPQI was also found to inhibit TrxR1. NADPH-reduced TrxR1 was significantly more sensitive to NAPQI (IC50 = 0.023 ?M) than the oxidized enzyme (IC50 = 1.0 ?M) or a human TrxR1 Sec498Cys mutant enzyme (IC50 = 17 ?M), indicating that cysteine and selenocysteine residues in the redox motifs of TrxR are critical for enzyme inactivation. This is supported by our findings that alkylation of reduced TrxR with biotin-conjugated iodoacetamide, which selectively reacts with selenol or thiol groups on proteins, was inhibited by NAPQI. LC-MS/MS analysis confirmed that NAPQI modified cysteine 59, cysteine 497, and selenocysteine 498 residues in the redox centers of TrxR, resulting in enzyme inhibition. In addition to disulfide reduction, TrxR is also known to mediate chemical redox cycling. We found that menadione redox cycling by TrxR was markedly less sensitive to NAPQI than disulfide reduction, suggesting that TrxR mediates these reactions via distinct mechanisms. These data demonstrate that APAP-reactive metabolites target TrxR, suggesting an additional mechanism by which APAP induces oxidative stress and hepatotoxicity. PMID:24661219

Jan, Yi-Hua; Heck, Diane E; Dragomir, Ana-Cristina; Gardner, Carol R; Laskin, Debra L; Laskin, Jeffrey D

2014-05-19

73

Evidence for the participation of Cys558 and Cys559 at the active site of mercuric reductase  

International Nuclear Information System (INIS)

Mercuric reductase, with FAD and a reducible disulfide at the active site, catalyzes the two-electron reduction of Hg(II) by NADPH. Addition of reducing equivalents rapidly produces a spectrally distinct EH2 form of the enzyme containing oxidized FAD and reduced active site thiols. Formation of EH2 has previously been reported to require only 2 electrons for reduction of the active site disulfide. The authors present results of anaerobic titrations of mercuric reductase with NADPH and dithionite showing that the equilibrium conversion of oxidized enzyme to EH2 actually requires 2 equiv of reducing agent or 4 electrons. Kinetic studies conducted both at 4 degree C and at 25 degree C indicate that reduction of the active site occurs rapidly, as previously reported; this is followed by a slower reduction of another redox group via reaction with the active site. [14C]Iodoacetamide labeling experiments demonstrate that the C-terminal residues, Cys558 and Cys559, are involved in this disulfide. The fluorescence, but not the absorbance, of the enzyme-bound FAD was found to be highly dependent on the redox state of the C-terminal thiols. Thus, Eox with Cys558 and Cys559 as thiols exhibits less than 50% of the fluorescence of Eox where these residues are present as a disulfide, indicating that the thiols remain intimately associated with the active site. Initial velociiated with the active site. Initial velocity measurements show that the auxiliary disulfide must be reduced before catalytic Hg(II) reduction can occur, consistent with the report of a preactivation phenomenon with NADPH or cysteine. A modified minimal catalytic mechanism is proposed as well as several chemical mechanisms for the Hg(II) reduction step

74

Thioredoxin Reductase and its Inhibitors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thioredoxin plays a crucial role in a wide number of physiological processes, which span from reduction of nucleotides to deoxyriboucleotides to the detoxification from xenobiotics, oxidants and radicals. The redox function of Thioredoxin is critically dependent on the enzyme Thioredoxin NADPH Reductase (TrxR). In view of its indirect involvement in the above mentioned physio/pathological processes, inhibition of TrxR is an important clinical goal. As a general rule, the affinities and mechan...

Saccoccia, Fulvio; Angelucci, Francesco; Boumis, Giovanna; Carotti, Daniela; Desiato, Gianni; Miele, Adriana E.; Bellelli, Andrea

2014-01-01

75

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

Science.gov (United States)

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

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

1996-01-01

76

Glutathione Reductase and Thioredoxin Reductase: Novel Antioxidant Enzymes from Plasmodium berghei  

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Malaria parasites adapt to the oxidative stress during their erythrocytic stages with the help of vital thioredoxin redox system and glutathione redox system. Glutathione reductase and thioredoxin reductase are important enzymes of these redox systems that help parasites to maintain an adequate intracellular redox environment. In the present study, activities of glutathione reductase and thioredoxin reductase were investigated in normal and Plasmodium berghei-infected mice red blood cells and...

Kapoor, Gaurav; Banyal, Harjeet Singh

2009-01-01

77

Fatty acyl-CoA reductase  

Energy Technology Data Exchange (ETDEWEB)

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

Reiser, Steven E.; Somerville, Chris R.

1998-12-01

78

On radiation protection of cells in vitro with thiols  

International Nuclear Information System (INIS)

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

79

21 CFR 864.7375 - Glutathione reductase assay.  

Science.gov (United States)

...2010-04-01 2010-04-01 false Glutathione reductase assay. 864.7375 Section...Hematology Kits and Packages § 864.7375 Glutathione reductase assay. (a) Identification. A glutathione reductase assay is a device used...

2010-04-01

80

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

Directory of Open Access Journals (Sweden)

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

Stantchev Tzanko S

2012-12-01

 
 
 
 
81

Benzofurazan Sulfides for Thiol Imaging and Quantification in Live Cells through Fluorescence Microscopy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thiol groups play a significant role in various cellular functions. Cellular thiol concentrations can be affected by various physiological or pathological factors. A fluorescence imaging agent that can effectively and specifically image thiols in live cells through fluorescence microscopy is desirable for live cell thiol monitoring. Benzofurazan sulfides 1a–e were synthesized and found to be thiol specific fluorogenic agents except 1d. They are not fluorescent but form strong fluorescent th...

Li, Yinghong; Yang, Yang; Guan, Xiangming

2012-01-01

82

Glutation. The thiol in intracellular is a good radioprotector?  

International Nuclear Information System (INIS)

Since 1988 there is a changing opinion about the Glutation's role in intracellular radiation protection. We review the thiols mechanism of radiation protection with special attention to GSH; and present the new features about this topic. (Author) 125 ref

83

Facially amphiphilic thiol capped gold and silver nanoparticles  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.

Bhat, Shreedhar; Maitra, Uday

2008-01-01

84

Indispensable platforms for bioimmobilization: maleimide-based thiol reactive hydrogels.  

Science.gov (United States)

Poly(ethylene glycol)-based hydrogels containing thiol-reactive maleimide functional groups is prepared via a Diels-Alder/retro Diels-Alder reaction sequence using a masked maleimide monomer. Bulk and micropatterned hydrogels containing varying amounts of the thiol-reactive maleimide functional group are fabricated at ambient temperature. During the fabrication, the reactive maleimide functional group in the monomer is masked with a furan moiety and then unmasked to its reactive form via the retro-Diels-Alder reaction. The reactive maleimide groups embedded within the hydrogel are amenable to facile and efficient functionalization with thiol-containing molecules such as fluorescent dyes. Furthermore, these hydrogels are readily biotinylated using the nucleophilic thiol-ene conjugation to enable immobilization of streptavidin onto the hydrogel patterns to achieve facile bioimmobilization. Notably, the extent of functionalization of these hydrogels can be easily tailored by varying the amount of reactive handles incorporated during their fabrication. PMID:25250772

Park, Eun Ju; Gevrek, Tugce Nihal; Sanyal, Rana; Sanyal, Amitav

2014-11-19

85

Induction Curing of Thiol-acrylate and Thiolene Composite Systems  

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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...

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

2011-01-01

86

Synthetic Applications of Intramolecular Thiol-Ene “Click” Reactions  

Directory of Open Access Journals (Sweden)

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.

Eoin M. Scanlan

2014-11-01

87

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

Science.gov (United States)

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

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

2012-04-01

88

Protein Thiols as an Indication of Oxidative Stress  

Directory of Open Access Journals (Sweden)

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

Yousef Rezaei Chianeh

2014-06-01

89

Interaction Profile of Diphenyl Diselenide with Pharmacologically Significant Thiols  

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Full Text Available Diphenyl diselenide has shown interesting biological activities in various free-radical-induced damage models and can be considered as a potential candidate drug against oxidative stress. Apart from its anti-oxidant activity, this compound can oxidize various thiols. However there are no detailed studies in the literature about the thiol oxidase-like activity of this compound against biologically significant mono and di-thiols with respect to various pH conditions. Keeping in mind the scarcity of data in this area of organochalcogen chemistry, we report for the first time the kinetics of thiol oxidation by diphenyl diselenide, which was carried out in a commonly used phosphate buffer, not only at physiological pH, but also at a number of acidic values. The relative reactivities of the different thiols with diphenyl diselenide were independent of the pKa of the thiol group, such that at pH 7.4, cysteine and dithiothreitol were the most reactive, while 2,3-dimercapto-1-propanesulfonic acid and glutathione were weakly reactive and extremely low reactivity was observed with dimercaptosuccinic acid. Rate of oxidation was dependent on the pH of the incubation medium. The results obtained will help us in the design of rational strategies for the safe pharmacological use of diphenyl diselenide.

Joao Batista Teixeira Rocha

2012-10-01

90

Trichomonas vaginalis: metronidazole and other nitroimidazole drugs are reduced by the flavin enzyme thioredoxin reductase and disrupt the cellular redox system. Implications for nitroimidazole toxicity and resistance.  

Science.gov (United States)

Infections with the microaerophilic parasite Trichomonas vaginalis are treated with the 5-nitroimidazole drug metronidazole, which is also in use against Entamoeba histolytica, Giardia intestinalis and microaerophilic/anaerobic bacteria. Here we report that in T. vaginalis the flavin enzyme thioredoxin reductase displays nitroreductase activity with nitroimidazoles, including metronidazole, and with the nitrofuran drug furazolidone. Reactive metabolites of metronidazole and other nitroimidazoles form covalent adducts with several proteins that are known or assumed to be associated with thioredoxin-mediated redox regulation, including thioredoxin reductase itself, ribonucleotide reductase, thioredoxin peroxidase and cytosolic malate dehydrogenase. Disulphide reducing activity of thioredoxin reductase was greatly diminished in extracts of metronidazole-treated cells and intracellular non-protein thiol levels were sharply decreased. We generated a highly metronidazole-resistant cell line that displayed only minimal thioredoxin reductase activity, not due to diminished expression of the enzyme but due to the lack of its FAD cofactor. Reduction of free flavins, readily observed in metronidazole-susceptible cells, was also absent in the resistant cells. On the other hand, iron-depleted T. vaginalis cells, expressing only minimal amounts of PFOR and hydrogenosomal malate dehydrogenase, remained fully susceptible to metronidazole. Thus, taken together, our data suggest a flavin-based mechanism of metronidazole activation and thereby challenge the current model of hydrogenosomal activation of nitroimidazole drugs. PMID:19415801

Leitsch, David; Kolarich, Daniel; Binder, Marina; Stadlmann, Johannes; Altmann, Friedrich; Duchêne, Michael

2009-04-01

91

The thioredoxin-thioredoxin reductase system can function in vivo as an alternative system to reduce oxidized glutathione in Saccharomyces cerevisiae.  

Science.gov (United States)

Cellular mechanisms that maintain redox homeostasis are crucial, providing buffering against oxidative stress. Glutathione, the most abundant low molecular weight thiol, is considered the major cellular redox buffer in most cells. To better understand how cells maintain glutathione redox homeostasis, cells of Saccharomyces cerevisiae were treated with extracellular oxidized glutathione (GSSG), and the effect on intracellular reduced glutathione (GSH) and GSSG were monitored over time. Intriguingly cells lacking GLR1 encoding the GSSG reductase in S. cerevisiae accumulated increased levels of GSH via a mechanism independent of the GSH biosynthetic pathway. Furthermore, residual NADPH-dependent GSSG reductase activity was found in lysate derived from glr1 cell. The cytosolic thioredoxin-thioredoxin reductase system and not the glutaredoxins (Grx1p, Grx2p, Grx6p, and Grx7p) contributes to the reduction of GSSG. Overexpression of the thioredoxins TRX1 or TRX2 in glr1 cells reduced GSSG accumulation, increased GSH levels, and reduced cellular glutathione E(h)'. Conversely, deletion of TRX1 or TRX2 in the glr1 strain led to increased accumulation of GSSG, reduced GSH levels, and increased cellular E(h)'. Furthermore, it was found that purified thioredoxins can reduce GSSG to GSH in the presence of thioredoxin reductase and NADPH in a reconstituted in vitro system. Collectively, these data indicate that the thioredoxin-thioredoxin reductase system can function as an alternative system to reduce GSSG in S. cerevisiae in vivo. PMID:19951944

Tan, Shi-Xiong; Greetham, Darren; Raeth, Sebastian; Grant, Chris M; Dawes, Ian W; Perrone, Gabriel G

2010-02-26

92

Measurements of glutathione and other thiols in cells and tissues: a simplified procedure based on the HPLC separation of monobromobimane derivatives of thiols  

International Nuclear Information System (INIS)

Although there is intense interest in the role of thiols in controlling the efficiency of radiosensitizers, and in developing thiols (or pro-drugs liberating thiols) as radioprotectors, there is little information regarding the concentration of specific thiols in cells, tumors and normal tissues. Details are presented of a modified procedure using the thiol binding agent monobromobimane with separation using paired-ion reverse phase high performance liquid chromatography (HPLC). This method has been extended to include measurements of the radiosensitizer misonidazole and its desmethylated metabolite Ro 05-9963 in tissues

93

Role of histidine-86 in the catalytic mechanism of ferredoxin:thioredoxin reductase.  

Science.gov (United States)

Ferredoxin:thioredoxin reductase catalyzes the reduction of thioredoxins in plant chloroplasts using the [Fe2S2] ferredoxin as a one-electron donor and as such plays a central role in light regulation of oxygenic photosynthesis. The active-site comprises a [Fe4S4] cluster next to a redox-active disulfide that is cleaved in sequential one-electron steps and the combination of spectroscopic and crystallographic studies have revealed a catalytic mechanism involving novel site specific cluster chemistry in the oxidized, one-electron- and two-electron-reduced redox states. Histidine-86 has emerged as a potential proton donor/acceptor in the catalytic mechanism based on redox-related changes in the positioning of the imidazole ring during redox cycling and greatly decreased activity for the H86Y variant. Here we report on spectroscopic and redox characterization of the [Fe4S4] center in Synechocystis sp. PCC 6803 H86Y ferredoxin:thoredoxin reductase in the accessible redox states of both the as purified and N-ethylmaleimide-modified forms, using the combination of UV-visible absorption and variable-temperature magnetic circular dichroism, EPR, resonance Raman and Mössbauer spectroscopies. The results demonstrate that His86 is required for formation of the partially valence-localized [Fe4S4]2+ cluster that is the hallmark of two-electron-reduced intermediate. Taken together with the available structural data, the spectroscopic results indicate a functional role for His86 in protonation/deprotonation of the cluster-interacting thiol and anchoring the cluster interacting thiol in close proximity to the cluster in the two-electron-reduced intermediate. PMID:19132843

Walters, Elizabeth M; Garcia-Serres, Ricardo; Naik, Sunil G; Bourquin, Florence; Glauser, Dominique A; Schürmann, Peter; Huynh, Boi Hanh; Johnson, Michael K

2009-02-10

94

Relationship between thiol-induced repair and repair by enzymes  

International Nuclear Information System (INIS)

The radioprotective effect of the addition of thiols (cysteamine and dithiothreitol, DTT) on the survival of ?-irradiated E. coli strains with deficiencies in their enzymatic repair capacities have been measured in the presence and absence of oxygen. The oxygen enhancement ratios (OER) decrease with increasing DTT concentrations in the repair wildtype to the level of the repair-deficient strain. This is interpreted as being the result of OH scavenging and a competition between oxygen and thiols for DNA radicals. At the highest thiol concentration oxygen cannot compete with chemical repair by H donation and this leads to smaller OER values. The OER and the protection by the addition of thiol (the dose modification factors, DMF) are smaller for strains with deficiencies in the enzymatic repair capacities than for strains proficient in enzymatic repair. The reason is that DNA damage produced in the absence of oxygen or in the presence of oxygen at high thiol concentrations are enzymatically relatively better repaired than that produced in the presence of oxygen. 25 refs., 3 figs., 2 tabs

95

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

International Nuclear Information System (INIS)

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

96

Effect of ?-irradiation on thiol compounds in grapefruit  

International Nuclear Information System (INIS)

The effect of 60Co ?-irradiation on thiol compounds in grapefruit was investigated. Thiols were separated by HPLC and measured with a fluorescence detector. Reduced glutathione (GSH), cysteine (CySH), cysteinylglycine (CySGly), and a number of unknown peaks were observed in unirradiated grapefruit. GSH was the main thiol at an average concentration of 143.3 ?M. GSH content exponentially decreased with increased radiation doses, and after 100 krad only 80% of the original remained. The G value based on the result of 100 krad was 0.29. Authentic GSH in water or citrate buffer (pH 3) was converted mainly to its oxidized form (GSSG) with ?-irradiated grapefruits showed no equivalent increase, however

97

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

International Nuclear Information System (INIS)

Full text: The epithelial lining of the GI mucosal surface is traditionally viewed as a passive barrier serving a largely protective function. Recently, enterocytes have been seen to function as sensitive indicators of oxidative stress, with defined responses to shifts in the oxidative balance. Radiation damage, long recognized as the result of the generation of reactive oxygen species, would theoretically be modulated by the presence of radical scavenging anti-oxidants. Cultures of IEC-6 cells, a model for the gastrointestinal epithelium were found to have lower numbers of adherent cells in response either n-acetyl cysteine (NAC) or l-ascorbate in the medium. In both cases the response was dose dependent, with inhibition in response to l-ascorbate well established by 48 hours. However, in contrast to the thiol antioxidant NAC where a late recovery was observed at high dose, no statistically significant increase in adherent cell numbers were observed with high dose l-ascorbate, and adherent cell numbers actually fell off with time. Exposure to antioxidants potentiated the damage from x-ray irradiation further reducing cell numbers. While we have previously shown that this damage was not associated with mitotic delay or inhibition of proliferation, the mechanism of this response remains undefined. Non-adherent cells were found to increase with dose in the presence of antioxidants with those cells having morphology consistent with apoptotic cells including nuclear condeth 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

98

5?-reductase activity in rat adipose tissue  

International Nuclear Information System (INIS)

We measured the 5 ?-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 5?-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 5?-reductase activity. Aromatase activity was minimal, several orders of magnitude less than 5?-reductase activity in each tissue studied

99

Reversible inactivation of CO dehydrogenase with thiol compounds.  

Science.gov (United States)

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

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

2014-05-01

100

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

International Nuclear Information System (INIS)

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

 
 
 
 
101

A dissimilatory nitrite reductase in Paracoccus halodenitrificans  

Science.gov (United States)

Paracoccus halodenitrificans produced a membrane-associated nitrite reductase. Spectrophotometric analysis showed it to be associated with a cd-cytochrome and located on the inner side of the cytoplasmic membrane. When supplied with nitrite, membrane preparations produced nitrous oxide and nitric oxide in different ratios depending on the electron donor employed. The nitrite reductase was maximally active at relatively low concentrations of sodium chloride and remained attached to the membranes at 100 mM sodium chloride.

Grant, M. A.; Hochstein, L. I.

1984-01-01

102

5?-Reductase Isozymes in the Prostate  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Zhu, Yuan-shan; Sun, Guang-huan

2005-01-01

103

General and practical formation of thiocyanates from thiols.  

Science.gov (United States)

A new method for the cyanation of thiols and disulfides using cyanobenziodoxol(on)e hypervalent iodine reagents is described. Both aliphatic and aromatic thiocyanates can be accessed in good yields in a few minutes at room temperature starting from a broad range of thiols with high chemioselectivity. The complete conversion of disulfides to thiocyanates was also possible. Preliminary computational studies indicated a low energy concerted transition state for the cyanation of the thiolate anion or radical. The developed thiocyanate synthesis has broad potential for various applications in synthetic chemistry, chemical biology and materials science. PMID:25521497

Frei, Reto; Courant, Thibaut; Wodrich, Matthew D; Waser, Jerome

2015-02-01

104

Application of new fluorescent thiol reagent to diagnosis of homocystinuria.  

Science.gov (United States)

A new fluorescent thiol reagent, dansyl-aminophenylmercuric acetate (DAPMA), was applied to the diagnosis of homocystinuria, a disorder which can be associated with vascular disease at an early age. DAPMA was added to urine containing metabisulphite and the resulting fluorescent derivatives were extracted on a cyclohexyl silica column and separated by thin-layer chromatography. 102 coded samples were tested. The derivative of homocysteine was easily identified in samples from 4 children with homocystinuria but was absent from all samples from normal subjects and patients with unrelated disorders. Other thiols (cysteine, acetylcysteine, mercaptolactate, thiosulphate, and thiocyanate) were also identified in urine from healthy fasting subjects. PMID:1681358

Maddocks, J L; MacLachlan, J

1991-10-26

105

Gel Permeation Chromatography Characterization of the Chain Length Distributions in Thiol-Acrylate Photopolymer Networks  

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Crosslinked, degradable networks formed from the photopolymerization of thiol and acrylate monomers are explored as potential biomaterials. The degradation behavior and material properties of these networks are influenced by the molecular weight of the nondegradable thiol-polyacrylate backbone chains that form during photopolymerization. Here, gel permeation chromatography was used to characterize the thiol-polyacrylate backbone chain lengths in degraded thiol-acrylate networks. Increasing th...

Rydholm, Amber E.; Held, Nicole L.; Bowman, Christopher N.; Anseth, Kristi S.

2006-01-01

106

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

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

Cansa?„a?±z, A.; A?ƒa?‡etin, A.; Kopara?„a?±r, M.

2005-01-01

107

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

Directory of Open Access Journals (Sweden)

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

A. Cansız

2005-02-01

108

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

DEFF Research Database (Denmark)

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

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

2013-01-01

109

Kinetics of deuterium isotope exchange between 2-methylpropane-2-thiol and propane-2-thiol in aprotic solvents  

International Nuclear Information System (INIS)

The rate constants for bimolecular deuterium isotope exchange between 2-methylpropane-2-thiol and propane-2-thiol in C6D12, CCl4, (CD3)2CO, HCON(CH3)2, (CD2)4O, and (CH3)2SO solutions were determined by use of H n.m.r. analysis. The rate constants, k, and activation enthalpy, ?H decrease, and entropy, -?S, increases, with increase in ability of the solvents to form hydrogen bonds with alkanethiols. The rate constant of concerted hydrogen transfer inside the cyclic dimer of alkanethiols with two H-bonds, k3, increases with increasing dielectric constant of the solvent. (author)

110

Structure and interactions in ?-crystallin probed through thiol group reactivity  

Directory of Open Access Journals (Sweden)

Full Text Available a-Crystallin is the major structural protein of eye lens of vertebrates. In human lens, the ratio of aA-crystallin to aB-crystallin was found to be 3:1. aA-Crystallin contains two cysteine residues at positions 131 and 142, which are at the junction between the a-crystallin domain and the C-terminal tail. We used the accessibility of the thiol groups by Ellman’s reagent (DTNB as a tool to gain information about the various structural perturbations of hinge region of a-crystallin and during the binding with substrates. In the native condition, the cys-142 though reacted quite fast was not fully exposed. Several reagents were used to see the accessibility of cys-131. Rate constant for cys-131 was increased gradually with increase in the concentration of reagents. The bindings of substrates are affected by the accessibility of thiol indicating that the substrates bind to the hinge region of a-crystallin. By blocking of cys-142, it was observed that the accessibility of one thiol depends on the other thiol, and they are not independent. The hinge region of a-crystallin is very important as substrate binding site and from this study we have got various structural information about that region.

Sudipa Saha

2013-10-01

111

Oxygen-Mediated Enzymatic Polymerization of Thiol-Ene Hydrogels.  

Science.gov (United States)

Materials that solidify in response to an initiation stimulus are currently utilized in several biomedical and surgical applications; however, their clinical adoption would be more widespread with improved physical properties and biocompatibility. One chemistry that is particularly promising is based on the thiol-ene addition reaction, a radical-mediated step-growth polymerization that is resistant to oxygen inhibition and thus is an excellent candidate for materials that polymerize upon exposure to aerobic conditions. Here, thiol-ene-based hydrogels are polymerized by exposing aqueous solutions of multi-functional thiol and allyl ether PEG monomers, in combination with enzymatic radical initiating systems, to air. An initiating system based on glucose oxidase, glucose, and Fe(2+) is initially investigated where, in the presence of glucose, the glucose oxidase reduces oxygen to hydrogen peroxide which is then further reduced by Fe(2+) to yield hydroxyl radicals capable of initiating thiol-ene polymerization. While this system is shown to effectively initiate polymerization after exposure to oxygen, the polymerization rate does not monotonically increase with raised Fe(2+) concentration owing to inhibitory reactions that retard polymerization at higher Fe(2+) concentrations. Conversely, replacing the Fe(2+) with horseradish peroxidase affords an initiating system is that is not subject to the iron-mediated inhibitory reactions and enables increased polymerization rates to be attained. PMID:24995128

Zavada, S R; McHardy, N R; Scott, T F

2014-05-01

112

Tumor rejection in experimental animals treated with radioprotective thiols  

International Nuclear Information System (INIS)

In experimental animals, a systemic treatment with thiols of the mercaptoalkylamine type has affected all of five solid tumors so far investigated. There was either inhibition of growth or ''oncodieresis,'' i.e., a necrosis and sloughing of tumors conducive to full recovery and repair. Mercaptoalkylamines and derivatives of the type used in our experiments are known to bind to cellular sites by a two-point attachment involving both thiol and amino groups. One of these compounds, cysteamine, was active in its native, unsubstituted form, but did not bring about oncodieresis when either the amino or thiol group, or both, were alkylated. Mercaptopropylamine, the 3-carbon homolog of cysteamine, was less active. Cystamine, a disulfide dimer of cysteamine that has no free reactive sulfhydryl, did not induce any reaction. Thioglycerol, lacking a terminal amino group, had only negligible activity. Rejection was much more striking when treatment was started on the day of inoculation than when started 7 days later. Male mice rejected better than females. Results were inferior when two of the agents were given simultaneously or together with other radioprotectants, such as L-cysteine, glutathione, dimethyl sulfoxide, or reserpine. Tumor rejection was enhanced when the phosphorylated thiols, S- 2-(3-aminopropylamino)ethylphosphorothioic acid or S-(2-ethylguanidine)phosphorothioic acid, were given simultaneously with the radioprotective serotonin, but there was no synergy of serotootonin, but there was no synergy of serotonin with the nonphosphorylated compounds S-2-aminoethylisothiouronium bromide or cysteamine. Serotonin alone did not affect the tumors. (U.S.)

113

Transsulfuration Pathway Thiols and Methylated Arginines: The Hunter Community Study  

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

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

2013-01-01

114

Tritium isotope fractionation between hydrogen sulphide and methyl thiol  

International Nuclear Information System (INIS)

Tritium isotope effect in the gas phase exchange reaction between hydrogen sulphide and methyl thiol has been determined. The results obtained vary from 1.08 to 1.04 over the temperature range of 283-323 K. The calculations based upon the quantum statistical theory of the isotope effects agree well with the experimental results. (author)

115

From sulfur to homoglutathione: Thiol metabolism in soybean  

Science.gov (United States)

Sulfur is an essential plant nutrient and is metabolized into the sulfur-containing amino acids (cysteine and methionine) and into molecules that protect plants against oxidative and environmental stresses. Although studies of thiol metabolism in the model plant Arabidopsis thaliana (thale cress) h...

116

Characterization of multiple Chinese hamster carbonyl reductases.  

Science.gov (United States)

Carbonyl reductase (CR) is an enzyme which can catalyze the oxidoreduction of various carbonyl compounds in the presence of NAD(P)H. With the PCR method, using primers carrying the conserved nucleotide sequence among mammalian CRs, we isolated three different cDNAs (CHCR1, CHCR2 and CHCR3) which encode a unique carbonyl reductase from the Chinese hamster. The PCR products of CHCR1 and CHCR2 were clearly isolated with Bpu1102I, BspEI and XmaI restriction enzymes. The nucleotide-sequence of CHCR3 was completely different from those of CHCR1 and CHCR2. The predicted double-wound betaalphabetaalpha-structures of the CHCRs suggests the presence of a typical NADP(+)-binding motif and is similar to the corresponding region of 3alpha,20beta-hydroxysteroid dehydrogenase and mouse lung tetrameric carbonyl reductase. The deduced amino acid sequence of CHCR1 showed a high homology to CHCR2 (>96%) and the other mammalian CRs (>81%). However, CHCR3 showed a high homology to human CBR3 (>86%) and a relatively lower homology to the other CHCRs (4-nitrobenzaldehyde and pyridine 4-carboxyaldehyde. These three CRs showed not only 3-keto reductase of steroids, but also 20-keto reductase. However, these CRs did not show any activity of 17-keto reductase activity. Both CHCR1 and CHCR2 have prostaglandin 9-keto reductase and 15-hydroxyprostaglandin dehydrogenase activities towards PGE(2) and PGF(2alpha) from the analyses of enzymatic reaction products. The results of Western blotting and RT-PCR suggest these CHCRs have a tissue-dependent-distribution in the Chinese hamster. PMID:11306100

Terada, T; Sugihara, Y; Nakamura, K; Sato, R; Sakuma, S; Fujimoto, Y; Fujita, T; Inazu, N; Maeda, M

2001-01-30

117

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

International Nuclear Information System (INIS)

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

118

The kinetics of thiol-mediated decomposition of S-nitrosothiols  

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The reaction of sulfhydryl (SH)-containing molecules (thiols) with S-nitrosothiols (RSNO) has been shown to be of biological importance. Biologically or therapeutically relevant thiols generally have a pKa value ranging from 8 to 10 for the SH group. In addition, some, of these thiols contain a carboxyl group and are acidic, which should be considered in studying the reaction between RSNO and thiols. In the present study, the kinetics of thiol-mediated decomposition of RSNO was investigated i...

Hu, Teh-min; Chou, Ta-chuan

2006-01-01

119

Evaluation of Nitrate Reductase Activity in Rhizobium japonicum†  

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Nitrate reductase activity was evaluated by four approaches, using four strains of Rhizobium japonicum and 11 chlorate-resistant mutants of the four strains. It was concluded that in vitro assays with bacteria or bacteroids provide the most simple and reliable assessment of the presence or absence of nitrate reductase. Nitrite reductase activity with methyl viologen and dithionite was found, but the enzyme activity does not confound the assay of nitrate reductase.

Streeter, John G.; Devine, Paul J.

1983-01-01

120

Respiratory arsenate reductase as a bidirectional enzyme  

International Nuclear Information System (INIS)

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

 
 
 
 
121

Induction Curing of Thiol-acrylate and Thiolene Composite Systems.  

Science.gov (United States)

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

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

2011-06-28

122

Reductive activation of hexavalent chromium by human lung epithelial cells: generation of Cr(V) and Cr(V)-thiol species.  

Science.gov (United States)

Chromium(VI) compounds (e.g. chromates) are cytotoxic, mutagenic, and potentially carcinogenic. The reduction of Cr(VI) can yield reactive intermediates such as Cr(V) and reactive oxygen species. Bronchial epithelial cells are the primary site of pulmonary exposure to inhaled Cr(VI) and are the primary cells from which Cr(VI)-associated human cancers arise. BEAS-2B cells were used here as a model of normal human bronchial epithelium for studies on the reductive activation of Cr(VI). Cells incubated with Na(2)CrO(4) exhibited two Cr(V) ESR signals, g=1.979 and 1.985, which persisted for at least 1h. The g=1.979 signal is similar to that generated in vitro by human microsomes and by proteoliposomes containing P450 reductase and cytochrome b(5). Unlike many cells in culture, these cells continued to express P450 reductase and cytochrome b(5). Studies with the non-selective thiol oxidant diamide indicated that the g=1.985 signal was thiol-dependent whereas the g=1.979 signal was not. Pretreatment with phenazine methosulfate eliminated both Cr(V) signals suggesting that Cr(V) generation is largely NAD(P)H-dependent. ESR spectra indicated that a portion of the Cr(VI) was rapidly reduced to Cr(III). Cells incubated with an insoluble chromate, ZnCrO(4), also generated both Cr(V) signals, whereas Cr(V) was not detected with insoluble PbCrO(4). In clonogenic assays, the cells were very sensitive to Na(2)CrO(4) and ZnCrO(4), but considerably less sensitive to PbCrO(4). PMID:18279960

Borthiry, Griselda R; Antholine, William E; Myers, Judith M; Myers, Charles R

2008-07-01

123

Thiol-ene clickable hyaluronans: from macro-to nanogels.  

Science.gov (United States)

The fabrication of hyaluronic acid (HA) nanogels using a thiol-ene reaction has been demonstrated. HA was modified with pentenoate groups and then cross-linked with poly(ethylene glycol)-bis(thiol) by exposure to UV light. The cross-linking density and thereby the rigidity of the obtained gels were precisely controlled by the degree of substitution of pentenoate-modified HA. Their swelling properties also depended on cross-linking density. To produce hydrogels at the nanoscale, hyaluronic acid precursors were solely confined inside liposomes before cross-linking and purified after cross-linking. The size of the resulting nanogels followed their swelling properties and was also affected by their cross-linking density. Such bionanogels with tunable mechanical and swelling properties have potential in drug delivery. PMID:24491329

Hachet, Emilie; Sereni, Nicolas; Pignot-Paintrand, Isabelle; Ravaine, Valérie; Szarpak-Jankowska, Anna; Auzély-Velty, Rachel

2014-04-01

124

Functional Graphene by Thiol-ene Click Chemistry.  

Science.gov (United States)

Thiol-ene click reaction was successfully employed for chemical modification of graphene oxide (GO) by one-step synthesis. Herein, 2,2-azobis(2-methylpropionitrile) (AIBN) was used as thermal catalyst and cysteamine hydrochloride (HS?(CH2 )2 ?NH2 HCl) was used as thiol-containing compound, which is incorporated to GO surface upon reaction with the C?C bonds. The hydrochloride acts as protecting group for the amine, which is finally eliminated by adding sodium hydroxide. The modified GO contains both S- and N-containing groups (NS-GO). We found that NS-GO sheets form good dispersion in water, ethanol, and ethylene glycol. These graphene dispersions can be processed into functionalized graphene film. Besides, it was demonstrated that NS-GO was proved to be an excellent host matrix for platinum nanoparticles. The developed method paves a new way for graphene modification and its functional nanocomposites. PMID:25580698

Luong, Nguyen Dang; Sinh, Le Hoang; Johansson, Leena-Sisko; Campell, Joseph; Seppälä, Jukka

2015-02-16

125

Thiol Signalling Network with an Eye to Diabetes  

Directory of Open Access Journals (Sweden)

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

Elena Matteucci

2010-12-01

126

Metal ion extraction with a thiol hydrophilic resin  

International Nuclear Information System (INIS)

The application of 30% N,N'-methylenebis(acrylamide) cross-linked poly[N-((acryloylamino)methyl)mercaptoacetamide] resin for the concentration of metal ions from aqueous solutions has been investigated. A flow injection analysis method using a color forming reagent was developed, allowing fast cation assays. The pH dependence of the metal extraction for Na, Ca, Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Ag(I), Cd(II), Hg(II), Pb(II), and UO22+ was studied. Heavy metals and Cu(II) exhibit a high affinity toward the thiol functions of the resin (half extraction pH 2 or/and MLL' complexes involving thiol functions and anion ligands. The resin selectivity determined at pH 5.5 is, in increasing order, Zn(II), Cd(II), Pb(II), Cu(II), and Hg

127

In situ study of pentacene interaction with archetypal hybrid contacts: Fluorinated versus alkane thiols on gold  

Science.gov (United States)

One approach developed to improve the performance of bottom contact source/drain electrodes is to treat the contacts with thiols before deposition of the semiconductor. There is evidence indicating that improvement is due to both morphological effects and improved work function matching. Especially suggestive evidence shows that thiols that increase the effective work function of the contacts (e.g., fluorinated thiols) yield better device performance than work function decreasing thiols (e.g., alkane thiols). Here, we compare two technologically relevant thiol treatments, an alkane thiol (1-hexadecanethiol), and a fluorinated thiol (pentafluorobenzenethiol), in pentacene organic field effect transistors. Using in situ semiconductor deposition, x-ray photoemission, and x-ray absorption spectroscopy, we are able to directly observe the interaction between the semiconductor and the thiol-treated gold layers. Our spectroscopic analysis suggests that there is not a site-specific chemical reaction between the pentacene and the thiol molecules. A homogeneous standing-up pentacene orientation was observed in both treated substrates, consistent with the morphological improvement expected from thiol treatment in both samples. Our study shows that both the highest occupied molecular orbital-Fermi level offset and C1s binding energy are shifted in the two thiol systems, which can be explained by varied dipole direction within the two thiols, causing a change in surface potential. The additional improvement of the electrical performance in the pentafluorobenzenethiol case is originated by a reduced hole injection barrier that is also associated with an increase in the density of states in the lowest unoccupied molecular orbital.

Jia, Zhang; Lee, Vincent W.; Kymissis, Ioannis; Floreano, Luca; Verdini, Alberto; Cossaro, Albano; Morgante, Alberto

2010-09-01

128

Selenocysteine in Thiol/Disulfide-Like Exchange Reactions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Significance: Among trace elements used as cofactors in enzymes, selenium is unique in that it is incorporated into proteins co-translationally in the form of an amino acid, selenocysteine (Sec). Sec differs from cysteine (Cys) by only one atom (selenium versus sulfur), yet this switch dramatically influences important aspects of enzyme reactivity. Recent Advances: The main focus of this review is an updated and critical discussion on how Sec might be used to accelerate thiol/disulfide-like e...

Hondal, Robert J.; Marino, Stefano M.; Gladyshev, Vadim N.

2013-01-01

129

Odorant polyfunctional thiols issued from bottle beer fermentation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2011-01-01

130

Functional Conducting Polymers via Thiol-ene Chemistry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Martin, David C.; Feldman, Kathleen E.

2012-01-01

131

Investigation of thiol derivatized gold nanoparticle sensors for gas analysis  

Science.gov (United States)

Analysis of volatile organic compounds (VOCs) in air and exhaled breath by sensor array is a very useful testing technique. It can provide non-invasive, fast, inexpensive testing for many diseases. Breath analysis has been very successful in identifying cancer and other diseases by using a chemiresistor sensor or array with gold nanoparticles to detect biomarkers. Acetone is a biomarker for diabetes and having a portable testing device could help to monitor diabetic and therapeutic progress. An advantage to this testing method is it is conducted at room temperature instead of 200 degrees Celsius. 3. The objective of this research is to determine the effect of thiol derivatized gold nanoparticles based on sensor(s) detection of VOCs. The VOCs to be tested are acetone, ethanol, and a mixture of acetone and ethanol. Each chip is tested under all three VOCs and three concentration levels (0.1, 1, and 5.0 ppm). VOC samples are used to test the sensors' ability to detect and differentiate VOCs. Sensors (also referred to as a chip) are prepared using several types of thiol derivatized gold nanoparticles. The factors are: thiol compound and molar volume loading of the thiol in synthesis. The average resistance results are used to determine the VOC selectivity of the sensors tested. The results show a trend of increasing resistance as VOC concentration is increased relative to dry air; which is used as baseline for VOCs. Several sensors show a high selectivity to one or more VOCs. Overall the 57 micromoles of 4-methoxy-toluenethiol sensor shows the strongest selectivity for VOCs tested. 3. Gerfen, Kurt. 2012. Detection of Acetone in Air Using Silver Ion Exchanged ZSM-5 and Zinc Oxide Sensing Films. Master of Science thesis, University of Louisville.

Stephens, Jared S.

132

Contrasting bonding behavior of thiol molecules on carbon fullerene structures  

International Nuclear Information System (INIS)

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

133

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

International Nuclear Information System (INIS)

The mechanism by which the ferredoxin-thioredoxin system activates the target enzyme, NADP-malate dehydrogenase, was investigated by analyzing the sulfhydryl status of individual protein components with [14C]iodoacetate and monobromobimane. The data indicate that ferredoxin-thioredoxin reductase (FTR)--an iron-sulfur enzyme present in oxygenic photosynthetic organisms--is the first member of a thiol chain that links light to enzyme regulation. FTR possesses a catalytically active dithiol group localized on the 13 kDa (similar) subunit, that occurs in all species investigated and accepts reducing equivalents from photoreduced ferredoxin and transfers them stoichiometrically to the disulfide form of thioredoxin m. The reduced thioredoxin m, in turn, reduces NADP-malate dehydrogenase, thereby converting it from an inactive (S-S) to an active (SH) form. The means by which FTR is able to combine electrons (from photoreduced ferredoxin) with protons (from the medium) to reduce its active disulfide group remains to be determined

134

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

International Nuclear Information System (INIS)

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

135

Organized thiol functional groups in mesoporous core shell colloids  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-03-15

136

Carotenoids, tocopherols and thiols as biological singlet molecular oxygen quenchers.  

Science.gov (United States)

Singlet molecular oxygen (1O2) has been shown to be generated in biological systems and is capable of damaging proteins, lipids and DNA. The ability of some biological antioxidants to quench 1O2 was studied by using singlet oxygen generated by the thermodissociation of the endoperoxide of 3,3'-(1,4-naphthylidene) dipropionate (NDPO2). The carotenoid lycopene was the most efficient 1O2 quencher (kq + kr = 31 x 10(9) M-1 s-1). Tocopherols and thiols were less effective. The singlet oxygen quenching ability decreased in the following order: lycopene, gamma-carotene, astaxanthin, canthaxanthin, alpha-carotene, beta-carotene, bixin, zeaxanthin, lutein, bilirubin, biliverdin, tocopherols and thiols. However, the compounds with low quenching rate constants occur at higher levels in biological tissues. Thus, carotenoids and tocopherols may contribute almost equally to the protection of tissues against the deleterious effects of 1O2. The quenching abilities of carotenoids and tocopherols were mainly due to physical quenching. In case of some thiols chemical quenching also plays a significant role. Carotenoids and tocopherols have been reported to exert a protective action against some types of cancer. PMID:2088803

Di Mascio, P; Devasagayam, T P; Kaiser, S; Sies, H

1990-12-01

137

Tailored thiol-functional polyamides: synthesis and functionalization.  

Science.gov (United States)

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

Mommer, Stefan; Keul, Helmut; Möller, Martin

2014-12-01

138

Puzzling subunits of mitochondrial cytochrome reductase  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The ubiquinol-cytochrome c reductase complex, like the other proton-pumping respiratory complexes of mitochondria, is an assembly of many different subunits. However, only a few of these subunits participate directly in the electron transfer and proton translocation. The roles of the other subunits are largely unknown. We discuss here some intriguing features of two of these subunits.

Weiss, Hanns; Leonard, Kevin; Neupert, Walter

1990-01-01

139

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Stewart, V.; Berg, B. L.

1988-01-01

140

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

DEFF Research Database (Denmark)

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

Nielsen, Jonas W.; Jensen, Kristine Steen

2012-01-01

 
 
 
 
141

Novel pyridine containing ligands as models for the copper centres in nitrite reductase  

International Nuclear Information System (INIS)

This thesis is concerned with the synthesis of a series of novel pyridine containing ligands and their copper co-ordination chemistry. The aim was to design ligands which would produce copper complexes which model the active sites within certain copper-containing Nitrite Reductase enzymes. The first chapter reviews previous work in this area and details the promising nature of pyridine-containing ligands. The remainder of this thesis is concerned with the synthesis and characterisation of some novel pyridine-containing ligands and their copper chemistry. The synthetic routes developed during this work enabled tris(pyrid-2-yl)methylamine ligands to be produced and studied which were tripodal in form but which had a primary amine group at the cap which could be further elaborated. Additional substituents were also placed on the pyridine rings to investigate their impact on the chemistry of their copper complexes. These ligands showed a variety, counter ion dependent chemistry. The structures of number of the copper complexes formed during these studies have been determined by X-ray crystallography. These showed the ligand system to exhibit various modes of co-ordination. The exploitation of the synthetic approaches developed to these tripyridyl tripodal ligands has enabled the basic ligand to be elaborated to incorporate thiol, protected thiol and/or thioether groups. As part of this study the X-ray crystal structure of a copper complex from an N2S22S2 ligand was determined. The synthesis of more sophisticated ligand systems which have both N3 and N2S2 donor sets within the same molecule have also been investigated. (author)

142

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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(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 ...

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

2008-01-01

143

A preliminary study of protein thiols and serum cholinesterase in assisted reproduction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this study we sought to investigate the levels of serum protein thiols and cholinesterase levels before and after intrauterine insemination (IUI).We observed 68% patients showed a decrease in protein thiols and 63% showed a decrease in serum cholinesterase levels after insemination as compared to their respective pre procedure levels. The fall in thiols was statistically significant (p=0.021) indicating there is increased oxidative stress after the procedure. However, we could not comment ...

Prabhu, Krishnananda; Kumar, Pratap; Pai, Muralidhar; Sinha, Indrajit; Rao, Anjali

2008-01-01

144

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

DEFF Research Database (Denmark)

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

Sikanen, Tiina M; Lafleur, Josiane P.

2013-01-01

145

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1994-12-31

146

The kinetics of thiol-mediated decomposition of S-nitrosothiols.  

Science.gov (United States)

The reaction of sulfhydryl (SH)-containing molecules (thiols) with S-nitrosothiols (RSNO) has been shown to be of biological importance. Biologically or therapeutically relevant thiols generally have a pKa value ranging from 8 to 10 for the SH group. In addition, some of these thiols contain a carboxyl group and are acidic, which should be considered in studying the reaction between RSNO and thiols. In the present study, the kinetics of thiol-mediated decomposition of RSNO was investigated in a commonly used phosphate buffer, phosphate buffered saline (PBS; containing 6.9 mM phosphates; buffer capacity = 3.8 mM/pH). The thiols studied can be divided into 2 groups, depending on their pH perturbation capacity. The kinetics was studied using a wide range of thiol concentrations (ie, from 0.1 to 10 mM). A high-performance liquid chromatography (HPLC) method was used to determine RSNO concentrations. The results showed that the acidic thiols, including glutathione, captopril, N-acetylcysteine, and tiopronin, stimulated RSNO decomposition at low millimolar concentrations up to 2 mM. The stimulatory effect, however, became attenuated at concentrations higher than 2 mM in PBS. Increasing the concentration of acidic thiols caused a decrease in solution pH, which was attributable to the inhibitory effect at high thiol concentrations. The effect of thiols on the pH of reaction solution, and the resulting bell-shaped rate profiles, can be predicted by a quantitative analysis, from which a comparison of the intrinsic reactivity toward RSNO, among 8 thiols, was possible. The intrinsic reactivity in general followed the Brønsted relation. PMID:17025266

Hu, Teh-Min; Chou, Ta-Chuan

2006-01-01

147

Thiol redox status evaluation in red blood cells by capillary electrophoresis-laser induced fluorescence detection  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thiols and in particular glutathione (GSH) play a central role in human metabolism, including the detoxification of xenobiotics, cell homeostasis, radioprotection, and antioxidant defence. Here, a new method is provided for the measurement of reduced and total forms of thiols in red blood cells. In order to minimize oxidation of reduced thiols, a water erythrocyte lysis (15 min at 4°C) was performed followed by a protein precipitation step with acetonitrile. The supernatant was ra...

Zinellu, Angelo; Sotgia, Salvatore; Usai, Maria Franca; Chessa, Roberto; Deiana, Luca; Carru, Ciriaco

2005-01-01

148

Synthesis of Oligonucleotides Carrying Thiol Groups Using a Simple Reagent Derived from Threoninol  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Oligonucleotides carrying thiol groups are useful intermediates for a remarkable number of applications involving nucleic acids. In this study, DNA oligonucleotides carrying tert-butylsulfanyl (t-BuS) protected thiol groups have been prepared. A building block derived from threoninol has been developed to introduce a thiol group at any predetemined position of an oligonucleotide. The resulting thiolated oligonucleotides have been used for the preparat...

Ramon Eritja; Santiago Grijalvo; Rubén Ferreira; Sonia Pérez-Rentero

2012-01-01

149

Crystal Growth of Thiol-Stabilized Gold Nanoparticles by Heat-Induced Coalescence  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract A monolayer of dodecanethiol-stabilized gold nanoparticles changed into two-dimensional and three-dimensional self-organized structures by annealing at 323 K. Subsequent crystal growth of gold nanoparticles occurred. Thiol molecules, although chemisorbed, form relatively unstable bonds with the gold surface; a few thiols desorbed from the surface and oxidized to disulfides at 323 K, because the interaction energy between thiol macromolecules is larger than that between a th...

Moon SookYoung; Tanaka Shun-ichiro; Sekino Tohru

2010-01-01

150

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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, ...

Simons Janet; Xu Song; Moores Bradley; Leonenko Zoya

2011-01-01

151

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Fredriksen, Kim A.; Kristensen, Tor E.; Hansen, Tore

2012-01-01

152

Resolution of oxidative stress by thioredoxin reductase: Cysteine versus selenocysteine  

Directory of Open Access Journals (Sweden)

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

Brian Cunniff

2014-01-01

153

Synthesis of Oligonucleotides Carrying Thiol Groups Using a Simple Reagent Derived from Threoninol  

Directory of Open Access Journals (Sweden)

Full Text Available Oligonucleotides carrying thiol groups are useful intermediates for a remarkable number of applications involving nucleic acids. In this study, DNA oligonucleotides carrying tert-butylsulfanyl (t-BuS protected thiol groups have been prepared. A building block derived from threoninol has been developed to introduce a thiol group at any predetemined position of an oligonucleotide. The resulting thiolated oligonucleotides have been used for the preparation of oligonucleotide conjugates and for the functionalization of gold nanoparticles using the reactivity of the thiol groups.

Ramon Eritja

2012-08-01

154

The interactions of thiols with olefins and their effects on autoxidation during JFTOT testing  

Energy Technology Data Exchange (ETDEWEB)

This paper shows that low concentrations of thiols will act as radical traps to inhibit autoxidation. When added to a fuel, thiols accelerated the rate of oxygen reaction without a commensurate increase in peroxidation. Evidence for the oxidative addition of thiols to olefins has been found to occur by studying the addition of thiophenol to indene in a model fuel during stressing in the JFTOT apparatus. Two different thiolindene adducts were found in the effluent, with the product distribution being temperature dependent. This process could account, in part, for the differences in thiol influences on autoxidation observed in model systems and in fuels.

Morris, R.E. (Code 6180, Chemistry Div., Naval Research Lab., Washington, DC (US))

1991-01-01

155

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

Science.gov (United States)

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

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

2013-12-10

156

Molecular modeling, structural analysis and identification of ligand binding sites of trypanothione reductase from Leishmania mexicana  

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Full Text Available Background & objectives: Trypanothione reductase (TR is a member of FAD-dependent NADPH oxidoreductase protein family and it is a key enzyme which connects the NADPH and the thiol-based redox system. Inhibition studies indicate that TR is an essential enzyme for parasite survival. Therefore, it is an attractive target enzyme for novel drug candidates. There is no structural model for TR of Leishmania mexicana (LmTR in the protein databases. In this work, 3D structure of TR from L. mexicana was identified by template-based in silico homology modeling method, resultant model was validated, structurally analyzed and possible ligand binding pockets were identified. Methods: For computational molecular modeling study, firstly, template was identified by BLAST search against PDB database. Multiple alignments were achieved by ClustalW2. Molecular modeling of LmTR was done and possible drug targeting sites were identified. Refinement of the model was done by performing local energy minimization for backbone, hydrogen and side chains. Model was validated by web-based servers. Results: A reliable 3D model for TR from L. mexicana was modeled by using L. infantum trypanothione reductase (LiTR as a template. RMSD results according to C-alpha, visible atoms and backbone were 0.809 Å, 0.732 Å and 0.728 Å respectively. Ramachandran plot indicates that model shows an acceptable stereochemistry. Conclusion: Modeled structure of LmTR shows high similarity with LiTR based on overall structural features like domains and folding patterns. Predicted structure will provide a source for the further docking studies of various peptide-based inhibitors.

Ozal Mutlu

2013-01-01

157

Purification and characterization of Taenia crassiceps cysticerci thioredoxin: insight into thioredoxin-glutathione-reductase (TGR) substrate recognition.  

Science.gov (United States)

Thioredoxin (Trx) is an oxidoreductase central to redox homeostasis in cells and is involved in the regulation of protein activity through thiol/disulfide exchanges. Based on these facts, our goal was to purify and characterize cytosolic thioredoxin from Taenia crassiceps cysticerci, as well as to study its behavior as a substrate of thioredoxin-glutathione reductase (TGR). The enzyme was purified >133-fold with a total yield of 9.7%. A molecular mass of 11.7kDa and a pI of 4.84 were measured. Native electrophoresis was used to identify the oxidized and reduced forms of the monomer as well as the presence of a homodimer. In addition to the catalytic site cysteines, cysticerci thioredoxin contains Cys28 and Cys65 residues conserved in previously sequenced cestode thioredoxins. The following kinetic parameters were obtained for the substrate of TGR: a Km of 3.1?M, a kcat of 10s(-1) and a catalytic efficiency of 3.2×10(6)M(-1)s(-1). The negative patch around the ?3-helix of Trx is involved in the interaction with TGR and suggests variable specificity and catalytic efficiency of the reductase toward thioredoxins of different origins. PMID:25523293

Martínez-González, J J; Guevara-Flores, A; Rendón, J L; Sosa-Peinado, A; Del Arenal Mena, I P

2015-04-01

158

Electrochemical study of thiols and disulfides using modified electrodes  

Energy Technology Data Exchange (ETDEWEB)

The electrochemical oxidative behavior of cysteine and several disulfides, such as cysteine, lipoic acid and disulfiram, have been investigated using a carbon paste (EPC) and a modified carbon paste (EPCM) electrode. The study has permitted the differentiation of the oxidative behavior of the thiol and of the disulfides. Modification of the carbon paste, by incorporating cobalt(II) phthalocyanine, offers interesting properties due to the electrocatalytic capability of the electrode. Using these types of electrodes the different molecules have been quantitatively determined at concentrations as low as 2.10/sup -7/ M. 14 references, 2 figures, 1 table.

Linders, C.R.; Patriarche, G.J.; Kauffman, J.M.

1986-01-01

159

Suspended hybrid films assembled from thiol-capped gold nanoparticles  

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

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

2012-01-01

160

Communication: Vacuum ultraviolet photoabsorption of interstellar icy thiols  

Science.gov (United States)

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

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

2014-12-01

 
 
 
 
161

Tip-enhanced Raman spectroscopic imaging of patterned thiol monolayers  

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

Johannes Stadler; Thomas Schmid; Lothar Opilik; Phillip Kuhn; Dittrich, Petra S.; Renato Zenobi

2011-01-01

162

Tellurite-mediated thiol oxidation in Escherichia coli.  

Science.gov (United States)

The oxyanion of tellurium, tellurite (TeO3(2-)), is toxic to most micro-organisms, particularly gram-negative bacteria. The mechanism of tellurite toxicity is presently unknown. Many heavy metals and oxyanions, including tellurite, interact with reduced thiols (RSH). To determine if tellurite interaction with RSH groups is involved in the toxicity mechanism, the RSH content of Escherichia coli cultures was assayed. After exposure to tellurite, cells were harvested and lysed in the presence of the RSH-specific reagent 5,5'-dithiobis(2-nitrobenzoic acid). Upon exposure of tellurite-susceptible cells to TeO3(2-), the RSH content decreased markedly. Resistance to potassium tellurite (Te(r)) in gram-negative bacteria is encoded by plasmids of incompatibility groups IncFI, IncP alpha, IncHI2, IncHI3 and IncHII, as well as the tehAtehB operon from the E. coli chromosome. When cells harbouring a Te(r) determinant were exposed to TeO3(2-), only a small fraction of the RSH content became oxidized. In addition to tellurite-dependent thiol oxidation, the resistance of E. coli mutants affected in proteins involved in disulfide-bond formation (dsb) was investigated. Mutant strains of dsbA and dsbB were found to be hypersensitive to tellurite (MIC 0.008-0.015 microg K2TeO3 ml(-1) compared to wild-type E. coli with MICs of 1-2 microg K2TeO3 ml(-1)). In contrast, dsbC and dsbD mutants showed no hypersensitivity. The results suggest that hypersensitivity to tellurite is reliant on the presence of an isomerase activity and not the thiol oxidase activity of the Dsb proteins. The results establish that the Te(r) determinants play an important role in maintaining homeostasis of the intracellular reducing environment within gram-negative cells through specific reactions with either TeO3(2-) or thiol:tellurium products. PMID:10517608

Turner, R J; Weiner, J H; Taylor, D E

1999-09-01

163

Aldose reductase, oxidative stress and diabetic mellitus  

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Diabetes mellitus (DM) is a complex metabolic disorder arising from lack of insulin production or insulin resistance (Diagnosis and classification of diabetes mellitus, 2007). DM is a leading cause of morbidity and mortality in the developed world, particularly from vascular complications such as atherothrombosis in the coronary vessels. Aldose reductase (AR; ALR2; EC 1.1.1.21), a key enzyme in the polyol pathway, catalyzes nicotinamide adenosine dinucleotide phosphate-dependent reduction of ...

JohnHwa

2012-01-01

164

S-Nitrosoglutathione Reductase in Human Lung Cancer  

Science.gov (United States)

S-Nitrosoglutathione (GSNO) reductase regulates cell signaling pathways relevant to asthma and protects cells from nitrosative stress. Recent evidence suggests that this enzyme may prevent human hepatocellular carcinoma arising in the setting of chronic hepatitis. We hypothesized that GSNO reductase may also protect the lung against potentially carcinogenic reactions associated with nitrosative stress. We report that wild-type Ras is S-nitrosylated and activated by nitrosative stress and that it is denitrosylated by GSNO reductase. In human lung cancer, the activity and expression of GSNO reductase are decreased. Further, the distribution of the enzyme (including its colocalization with wild-type Ras) is abnormal. We conclude that decreased activity of GSNO reductase could leave the human lung vulnerable to the oncogenic effects of nitrosative stress, as is the case in the liver. This potential should be considered when developing therapies that inhibit pulmonary GSNO reductase to treat asthma and other conditions. PMID:21816964

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

2012-01-01

165

Mutagenesis of the redox-active disulfide in mercuric ion reductase: Catalysis by mutant enzymes restricted to flavin redox chemistry  

International Nuclear Information System (INIS)

Mercuric reductase, a flavoenzyme that possesses a redox-active cystine, Cys135Cys140, catalyzes the reduction of Hg(II) to Hg(0) by NADPH. As a probe of mechanism, the authors have constructed mutants lacking a redox-active disulfide by eliminating Cys135 (Ala135Cys140), Cys14 (Cys135Ala140), or both (Ala135Ala140). Additionally, they have made double mutants that lack Cys135 (Ala135Cys139Cys140) or Cys140 (Cys135Cys139Ala140) but introduce a new Cys in place of Gly139 with the aim of constructing dithiol pairs in the active site that do not form a redox-active disulfide. The resulting mutant enzymes all lack redox-active disulfides and are hence restricted to FAD/FADH2 redox chemistry. Each mutant enzyme possesses unique physical and spectroscopic properties that reflect subtle differences in the FAD microenvironment. Preliminary evidence for the Ala135Cys139Cys14 mutant enzyme suggests that this protein forms a disulfide between the two adjacent Cys residues. Hg(II) titration experiments that correlate the extent of charge-transfer quenching with Hg(II) binding indicate that the Ala135Cys140 protein binds Hg(II) with substantially less avidity than does the wild-type enzyme. All mutant mercuric the wild-type enzyme. All mutant mercuric reductases catalyze transhydrogenation and oxygen reduction reactions through obligatory reduced flavin intermediates at rates comparable to or greater than that of the wild-type enzyme. In multiple-turnover assays which monitored the production of Hg(0), two of the mutant enzymes were observed to proceed through at least 30 turnovers at rates ca. 1000-fold slower than that of wild-type mercuric reductase. They conclude that the Cys135 and Cys140 thiols serve as Hg(II) ligands that orient the Hg(II) for subsequent reduction by a reduced flavin intermediate

166

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

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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 ?...

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

2011-01-01

167

A novel nitrite reductase gene from the cyanobacterium Plectonema boryanum.  

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The gene (nirA) for nitrite reductase was cloned from the nonheterocystous, filamentous cyanobacterium Plectonema boryanum. The predicted protein consists of 654 amino acids and has a calculated molecular weight of 72,135. The deduced amino acid sequence from positions 1 to 511 is strongly similar to the entire sequence of the ferredoxin-dependent nitrite reductases from other phototrophs, while the remainder of the protein is unique to the Plectonema nitrite reductase. The C-terminal portion...

Suzuki, I.; Kikuchi, H.; Nakanishi, S.; Fujita, Y.; Sugiyama, T.; Omata, T.

1995-01-01

168

Enoate reductases of Clostridia. Cloning, sequencing, and expression.  

Science.gov (United States)

The enr genes specifying enoate reductases of Clostridium tyrobutyricum and Clostridium thermoaceticum were cloned and sequenced. Sequence comparison shows that enoate reductases are similar to a family of flavoproteins comprising 2,4-dienoyl-coenzyme A reductase from Escherichia coli and old yellow enzyme from yeast. The C. thermoaceticum enr gene product was expressed in recombinant Escherichia coli cells growing under anaerobic conditions. The recombinant enzyme was purified and characterized. PMID:11060310

Rohdich, F; Wiese, A; Feicht, R; Simon, H; Bacher, A

2001-02-23

169

Cloning and nitrate induction of nitrate reductase mRNA  

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

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

1986-01-01

170

Characterization of the Chlorate Reductase from Pseudomonas chloritidismutans  

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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...

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

2003-01-01

171

Ketopantoyl-lactone reductase from Candida parapsilosis: purification and characterization as a conjugated polyketone reductase.  

Science.gov (United States)

Ketopantoyl-lactone reductase (2-dehydropantoyl-lactone reductase, EC 1.1.1.168) was purified and crystallized from cells of Candida parapsilosis IFO 0708. The enzyme was found to be homogeneous on ultracentrifugation, high-performance gel-permeation liquid chromatography and SDS-polyacrylamide gel electrophoresis. The relative molecular mass of the native and SDS-treated enzyme is approximately 40,000. The isoelectric point of the enzyme is 6.3. The enzyme was found to catalyze specifically the reduction of a variety of natural and unnatural polyketones and quinones other than ketopantoyl lactone in the presence of NADPH. Isatin and 5-methylisatin are rapidly reduced by the enzyme, the Km and Vmax values for isatin being 14 microM and 306 mumol/min per mg protein, respectively. Ketopantoyl lactone is also a good substrate (Km = 333 microM and Vmax = 481 mumol/min per mg protein). Reverse reaction was not detected with pantoyl lactone and NADP+. The enzyme is inhibited by quercetin, several polyketones and SH-reagents. 3,4-Dihydroxy-3-cyclobutene-1,2-dione, cyclohexenediol-1,2,3,4-tetraone and parabanic acid are uncompetitive inhibitors for the enzyme, the Ki values being 1.4, 0.2 and 3140 microM, respectively, with isatin as substrate. Comparison of the enzyme with the conjugated polyketone reductase of Mucor ambiguus (S. Shimizu, H. Hattori, H. Hata and H. Yamada (1988) Eur. J. Biochem. 174, 37-44) and ketopantoyl-lactone reductase of Saccharomyces cerevisiae suggested that ketopantoyl-lactone reductase is a kind of conjugated polyketone reductase. PMID:2644973

Hata, H; Shimizu, S; Hattori, S; Yamada, H

1989-02-24

172

Comparison of three thiol probes for determination of apoptosis-related changes in cellular redox status.  

Science.gov (United States)

An early step in apoptosis is extrusion of reduced glutathione (GSH). Current assays for measuring apoptosis involve a number of incubation and washing steps, making them time consuming and laborious. Using two novel thiol reactive agents (VitaBright-43 and VitaBright-48) and a GSH specific probe; monochlorobimane, we investigated whether changes in the level of free thiols can be used as an apoptotic marker. Upon addition to cells the probes permeate the cell membrane and react with intracellular thiols, causing cellular fluorescence. Cytometric quantification of the cell fluorescence (without washing) can then be used to determine the population's cellular thiol level at the single cell level. Apoptotic traits such as phosphatidylserine externalisation, caspase activity and mitochondrial potential were investigated at different time points after induction of apoptosis and correlated to changes detected using the thiol probes. We found that though all three thiol probes could be used to detect changes in the level of free thiols correlating well with apoptotic markers, other properties such as detection of early versus late apoptosis and staining kinetics differed among the three probes. However, we suggest adding evaluation of the level of free thiols to the list of phenotypes which may be measured in order to detect apoptosis, as this provides a reliable and easy way of assaying apoptosis. PMID:24222540

Skindersoe, Mette E; Kjaerulff, Soeren

2014-02-01

173

The role of thiols in cellular response to radiation and drugs  

International Nuclear Information System (INIS)

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

174

Effect of opacification and pigmentation on human lens protein thiol/disulfide and solubility.  

Science.gov (United States)

In this study, we compared the thiol/disulfide status and the protein profiles for a group of normal lenses (over 60 years old) and a group of age matched cataractous lenses. In agreement with previous reports we found that the severity of the lens opacity and the color of the nucleus correlated well with the decrease of soluble proteins and increase of guanidine insoluble proteins. However, the decrease of nonprotein thiols and protein thiols was associated only with the pigmentation of the lenses. We discovered that protein-thiol mixed disulfide profiles provided new information on the lens biochemical changes. In the normal lens, we found nearly 10% of the total nonprotein thiols bound to the protein. There were two species of protein-thiol mixed disulfides, protein-GSH and protein-cysteine with the former 3-4 times higher than the latter. In the cataractous lens the mean value of some species was elevated two-fold whereas in the noncataractous pigmented lens both protein-thiol mixed disulfides were elevated but the protein-cysteine species showed more drastic increase (three-fold in one case and 13-fold in another case). It is therefore concluded that the formation of protein-thiol mixed disulfides may play a more critical role in cataractogenesis than does protein-protein disulfide formation. PMID:2791632

Lou, M F; Huang, Q L; Zigler, J S

1989-09-01

175

On-resin peptide macrocyclization using thiol-ene click chemistry  

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A versatile and rapid synthetic strategy has been developed for the on-resin cyclization of peptides using thiol-ene photochemistry. This unique method exploits the thiol group of natural cysteine amino acids and allows for various alkenes to be incorporated orthogonal to the peptide backbone.

Aimetti, Alex A.; Shoemaker, Richard K.; Lin, Chien-chi; Anseth, Kristi S.

2010-01-01

176

Thiol-ene” click chemistry: A facile and versatile route to functionalization of porous polymer monoliths  

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The preparation of porous polymer monoliths with dodecyl and zwitterionic functionalities via the “thiol-ene” click chemistry of thiol-containing monoliths with both hydrophobic and polar methacrylate “ene” monomers has been demonstrated. Selected separations confirmed the excellent potential of these monoliths in chromatography.

Lv, Yongqin; Lin, Zhixing; Svec, Frantisek

2012-01-01

177

Nitrate reductase of green algae is located in the pyrenoid.  

Science.gov (United States)

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

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

1985-12-01

178

Structural classification and properties of ketoacyl reductases, hydroxyacyl dehydratases and enoyl reductases.  

Science.gov (United States)

Ketoacyl reductases (KRs), hydroxyacyl dehydratases (HDs) and enoyl reductases (ERs) are part of the fatty acid and polyketide synthesis cycles. Their reverse reactions, catalyzed by acyl dehydrogenases (equivalent to ERs), enoyl hydratases (equivalent to HDs) and hydroxyacyl dehydrogenases (equivalent to KRs), are part of fatty acid degradation by ?-oxidation. These enzymes have been classified into families based on similarities in their primary and tertiary structures, and these families and their structures are included in the ThYme (Thioester-active enzYmes) database. Members of each family have strong sequence similarity and have essentially the same tertiary structure, mechanism and catalytic residues. PMID:22915596

Cantu, David C; Dai, Tingsong; Beversdorf, Zachary S; Reilly, Peter J

2012-12-01

179

Tandem mass spectrometric characterization of thiol peptides modified by the chemoselective cationic sulfhydryl reagent (4-iodobutyl)triphenylphosphonium: Effects of a cationic thiol derivatization on peptide fragmentation  

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Fixed charge chemical modifications on peptides and proteins can impact the fragmentation behaviors in tandem mass spectrometry (MS/MS). In this study, we employed a thiol-specific cationic alkylation reagent, (4-iodobutyl)triphenylphosphonium (IBTP), to selectively modify cysteine thiol groups in mitochondrial proteome samples. Tandem mass spectrometric characteristics of butyltriphenylphosphonium (BTP)-modified peptides were evaluated by comparison to their carbamidomethylated (CAM) analogu...

Wang, Jing; Zhang, Jie; Arbogast, Brian; Maier, Claudia S.

2011-01-01

180

Radical reactions in aqueous disulphide-thiol systems  

International Nuclear Information System (INIS)

Absolute rate constants have been measured for the reaction of (CH3SSCH3)cation radical and sulphur centred radical cations of lipoic acid, lip (SS)cation radical, with various thiols including penicillamine, cysteamine and cysteine. Under pulse radiolysis conditions no reaction was observed between the disulphide radical cations and the neutral thiols, RSH, i.e. k7 M-1 s-1. Rate constants in the order of 109 M-1 s-1, i.e. close to the diffusion controlled limit, were, however, found for the corresponding reactions with the thiolates, RS-. In systems containing lipoate and cysteamine the lip(SS)cation radical induced oxidation of CyaS- proceeds via CyaSradical, (CyaS...SCya)- and lip(S...S)- as intermediates, i.e. results in a cysteamine mediated conversion of an oxidizing lip(SS) radical cation to a reducing lip((S...S) radical anion along the reaction route. In other cases the reaction of disulphide radical cations with thiolate anions was found to proceed via an optically absorbing transient (lambdasub(max)approx.=380nm) which is suggested to be an adduct radical. The mechanism of the (RSSR)cation radical induced oxidation of thiolate appears to depend on the stability of the 3-electron bonded disulphide radical anion. (author)

 
 
 
 
181

Expression and distribution of thiol-regulating enzyme glutaredoxin 2 (GRX2) in porcine ocular tissues.  

Science.gov (United States)

Glutaredoxin2 (Grx2) is a mitochondrial isozyme of the cytosolic glutaredoxin1 (thioltransferase or TTase). Both belong to the large oxidoreductase family and play an important role in maintaining thiol/disulfide redox homeostasis in the cells. Grx2 is recently found in the lens where its activities of disulfide reductase and peroxidase, similar to TTase, can protect the lens against oxidative stress. Since other eye tissues are also highly sensitive to oxidative stress, and TTase's distribution in the eye is known, we focused on this study by investigating the Grx2 distribution in the ocular tissues in comparison to the lens. Fresh porcine eyes were dissected into cornea, iris, ciliary body, the lens, vitreous humor, retina, and optic nerve. Each tissue (pooled from three eyes) was homogenized and processed for mitochondrial isolation. The mitochondrial fraction was analyzed for Grx2 protein using Western blotting with anti-Grx2 antibody, and Grx2 activity using the published procedure. The eye tissues were also measured for Grx2 mRNA expression by RT-PCR with GAPDH as the control. Grx2-rich mouse liver and purified recombinant mouse Grx2 were used as positive controls for the above analyses. It was found that Grx2 was present in all the tested ocular tissues, except vitreous humor. In comparison with the mouse liver, the protein levels of Grx2 in porcine ciliary body and the lens were 27-fold and 0.75-fold, respectively. Comparing to the lens, Grx2 protein was highest in the ciliary body (13.5-fold), followed by retina (9.2-fold), iris and optic nerve (2-fold), and cornea (1.2-fold). Enzyme activity assays showed that the retina had the highest Grx2 specific activity (3.9 mU/mg protein), followed by ciliary body (3.1 mU/mg), the lens (0.58 mU/mg), and optic nerve (0.32 mU/mg). Grx2 gene expression in these ocular tissues was further confirmed by RT-PCR analysis. Grx2 mRNA expression showed the highest in ciliary body, followed by retina, optic nerve, cornea, iris, and the lens. No Grx2 mRNA, protein or enzyme activity could be found in the vitreous humor. The results indicate that Grx2 level was higher in eye tissues rich in vasculature and mitochondria (i.e. ciliary body and retina), corroborating with the levels of mRNA expression and Grx2 activity. The rich presence of Grx2 in these tissues is also consistent with their known sensitivity to oxidative stress. PMID:25479045

Upadhyaya, Bijaya; Tian, Xiaoli; Wu, Hongli; Lou, Marjorie F

2015-01-01

182

Novel Water-Soluble Diorganyl Tellurides with Thiol Peroxidase and Antioxidant Activity.  

Science.gov (United States)

Novel water-soluble diaryl tellurides, alkyl aryl tellurides, and dialkyl tellurides carrying sulfopropyl groups were prepared and found to possess potent peroxide decomposing and chain-breaking antioxidative capacity. The dilithium, disodium, dipotassium, and bis-tetramethylammonium salts of bis(4-hydroxyphenyl) telluride (4) were treated with 2.3 equiv of 1,3-propanesultone in aqueous tert-butyl alcohol to give the corresponding salts 5 of bis-O-sulfopropylated diaryl telluride. A variety of diaryl ditellurides were reduced with sodium borohydride in ethanol. Upon addition of propanesultone to the resulting sodium arenetellurolates, the corresponding 3-aryltellurenylpropanesulfonic acid sodium salts 8 were precipitated. Diphenyl diselenide and dibutyl ditelluride reacted similarly to afford the sodium salts of 3-benzeneselenenylpropanesulfonic acid (9) and 4-telluraoctanesulfonic acid (10), respectively. The glutathione peroxidase-like activity of the water-soluble compounds was assessed at pH = 7.4 by using the coupled GSSG reductase assay. Dialkyl telluride 10 turned out to be the most efficient catalyst. Several alkyl aryl tellurides 8 were also more efficient than any of the previously tested organotellurium compounds in this model. Bulky and electron-withdrawing aryl substituents seemed to reduce activity, whereas electron-donating groups enhanced it. Alkyl aryl selenide 9 was void of any catalytic activity. The novel compounds were also assessed by (1)H NMR spectroscopy for their capacity to catalyze the hydrogen peroxide oxidation of N-acetylcysteine in D(2)O under acidic conditions. In the presence of 0.01 mol % of the organotellurium catalyst, the thiol concentration was reduced to 50% within 12 min for the most active catalyst (compound 5b). Although many of the compounds showed high catalytic activity, it was not possible to rationalize their relative efficiency. The capacity of the novel organotellurium compounds to act as a scavengers of 1,1-diphenyl-2-picrylhydrazyl (DPPH) was also investigated. The organotelluriums seem to act primarily as electron donors in their reaction with DPPH. Compounds 8d, 10, and 8b were the most effective scavengers. Bulky or electron-withdrawing aryl substituents caused a reduction in activity, whereas electron-donating ones enhanced it. None of the compounds could match vitamin E in their scavanging capacity. PMID:11674732

Kanda, Takahiro; Engman, Lars; Cotgreave, Ian A.; Powis, Garth

1999-10-29

183

Thiol/Disulfide System Plays a Crucial Role in Redox Protection in the Acidophilic Iron-Oxidizing Bacterium Leptospirillum ferriphilum  

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Thiol/disulfide systems are involved in the maintenance of the redox status of proteins and other molecules that contain thiol/disulfide groups. Leptospirillum ferriphilum DSM14647, an acidophilic bacterium that uses Fe2+ as electron donor, and withstands very high concentrations of iron and other redox active metals, is a good model to study how acidophiles preserve the thiol/disulfide balance. We studied the composition of thiol/disulfide systems and their role in the oxidative stress respo...

Norambuena, Javiera; Flores, Rodrigo; Ca?rdenas, Juan P.; Quatrini, Raquel; Cha?vez, Renato; Levica?n, Gloria

2012-01-01

184

Influence of N,N-dimethylaniline on the association of phenobarbital-induced cytochrome P-450 and NADPH-cytochrome c(P-450) reductase in a reconstituted rabbit liver microsomal enzyme system.  

Science.gov (United States)

N,N-Dimethylaniline when added to reaction mixtures provokes deviation from Michaelis-Menten law of the interaction kinetics of NADPH-cytochrome c(P-450) reductase (NADPH:ferrihaemoprotein oxidoreductase, EC 1.6.2.4) with highly purified phenobarbital-induced rabbit liver microsomal cytochrome P-450 (P-450LM2). This phenomenon is not associated with the low-to-high spin transition in the iron-coordination sphere of the haemoprotein, as elicited by the arylamine. Substrate-triggered departure from linearity of the kinetics is abolished by inclusion into the assay media of p-chloromercuribenzoate, hinting at a vital role in the process of thiols. Similarly, the parabolic progress curve (nH = 1.7) is transformed to a straight line (nH = 1.01) when the N-terminal reductase-binding domain in the P-450LM2 molecule is selectively blocked through covalent attachment of fluorescein isothiocyanate (FITC); such a modification does not alter the affinity of the haemoprotein for the amine substrate. Steady-state fluorescence polarization measurements reveal that N,N-dimethylaniline perturbs the motional properties of the fluorophore-bearing reductase-binding region, suggesting the induction of a conformational change. Summarizing these results, the data possibly indicate N,N-dimethylaniline-induced cooperativity in the association of reductase with P-450LM2. PMID:3113486

Hlavica, P; Golly, I; Wolf, J

1987-09-01

185

Probing the thiol-gold planar interface by spin polarized tunneling  

Energy Technology Data Exchange (ETDEWEB)

Reports of induced magnetism at thiol-gold interface have generated considerable recent interest. In these studies, the sample magnetization was generally measured by superconducting quantum interference device magnetometry which has limitation in determining surface and interface magnetism. In this work, we have fabricated planar tunnel junctions incorporating a thiol-gold interface. An observed room temperature humidity effect together with low temperature inelastic electron tunneling spectroscopy confirmed the existence of a thiol-gold interface in the organic-inorganic hybrid heterostructure. Spin polarized tunneling measurements were performed to probe the spin polarization at the thiol-gold interface; however, the obtained spin polarized tunneling spectra indicate no measurable spin polarization at the thiol-gold interface.

Zhang, Xiaohang; McGill, Stephen A.; Xiong, Peng, E-mail: xiong@physics.fsu.edu [Department of Physics, Florida State University, Tallahassee, Florida 32306 (United States); Wang, Xiaolei; Zhao, Jianhua [State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

2014-04-14

186

Probing the thiol-gold planar interface by spin polarized tunneling  

International Nuclear Information System (INIS)

Reports of induced magnetism at thiol-gold interface have generated considerable recent interest. In these studies, the sample magnetization was generally measured by superconducting quantum interference device magnetometry which has limitation in determining surface and interface magnetism. In this work, we have fabricated planar tunnel junctions incorporating a thiol-gold interface. An observed room temperature humidity effect together with low temperature inelastic electron tunneling spectroscopy confirmed the existence of a thiol-gold interface in the organic-inorganic hybrid heterostructure. Spin polarized tunneling measurements were performed to probe the spin polarization at the thiol-gold interface; however, the obtained spin polarized tunneling spectra indicate no measurable spin polarization at the thiol-gold interface

187

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

DEFF Research Database (Denmark)

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

Lafleur, Josiane P.; Kwapiszewski, Radoslaw

2012-01-01

188

Combinatorial synthesis and screening of novel odorants such as polyfunctional thiols.  

Science.gov (United States)

Combinatorial chemistry was shown to be an efficient tool for the preparation of new aroma-impact compounds. In this case, polyfunctional thiols were synthesized quickly using halide reagents or Bunte salt intermediates. They were separated by gas chromatography and then characterized using low resolution EI and CI mass spectrometry. The individual sensorial properties of the thiol products (i.e. odor and perception threshold) were determined by GC-O (olfactometry) which uses the human nose as detector. The thiols were characterized based on their particular odors. 3-Methyl-2-buten-1-thiol, a relevant flavor naturally present in beer and coffee, emerged as the most powerful of the thiol library. PMID:17017878

Vermeulen, Catherine; Collin, Sonia

2006-09-01

189

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

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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.

Figueirêdo P.M.S.

2003-01-01

190

Investigation of reactions postulated to occur during inhibition of ribonucleotide reductases by 2?-azido-2?-deoxynucleotides  

Science.gov (United States)

Model 3?-azido-3?-deoxynucleosides with thiol or vicinal dithiol substituents at C2? or C5? were synthesized to study reactions postulated to occur during inhibition of ribonucleotide reductases by 2?-azido-2?-deoxynucleotides. Esterification of 5?-(tert-butyldiphenylsilyl)-3?-azido-3?-deoxyadenosine and 3?-azido-3?-deoxythymidine (AZT) with 2,3-S-isopropylidene-2,3-dimercaptopropanoic acid or N-Boc-S-trityl-L-cysteine and deprotection gave 3?-azido-3?-deoxy-2?-O-(2,3-dimercaptopropanoyl or cysteinyl)adenosine and the 3?-azido-3?-deoxy-5?-O-(2,3-dimercaptopropanoyl or cysteinyl)thymidine analogs. Density functional calculations predicted that intramolecular reactions between generated thiyl radicals and an azido group on such model compounds would be exothermic by 33.6-41.2 kcal/mol and have low energy barriers of 10.4-13.5 kcal/mol. Reduction of the azido group occurred to give 3?-amino-3?-deoxythymidine, which was postulated to occur with thiyl radicals generated by treatment of 3?-azido-3?-deoxy-5?-O-(2,3-dimercaptopropanoyl)thymidine with 2,2?-azobis-(2-methyl-2-propionamidine) dihydrochloride. Gamma radiolysis of N2O-saturated aqueous solutions of AZT and cysteine produced 3?-amino-3?-deoxythymidine and thymine most likely by both radical and ionic processes. PMID:22711937

Dang, Thao P.; Sobczak, Adam J.; Mebel, Alexander M.; Chatgilialoglu, Chryssostomos; Wnuk, Stanislaw F.

2012-01-01

191

Investigation of reactions postulated to occur during inhibition of ribonucleotide reductases by 2'-azido-2'-deoxynucleotides.  

Science.gov (United States)

Model 3'-azido-3'-deoxynucleosides with thiol or vicinal dithiol substituents at C2' or C5' were synthesized to study reactions postulated to occur during inhibition of ribonucleotide reductases by 2'-azido-2'-deoxynucleotides. Esterification of 5'-(tert-butyldiphenylsilyl)-3'-azido-3'-deoxyadenosine and 3'-azido-3'-deoxythymidine (AZT) with 2,3-S-isopropylidene-2,3-dimercaptopropanoic acid or N-Boc-S-trityl-L-cysteine and deprotection gave 3'-azido-3'-deoxy-2'-O-(2,3-dimercaptopropanoyl or cysteinyl)adenosine and the 3'-azido-3'-deoxy-5'-O-(2,3-dimercaptopropanoyl or cysteinyl)thymidine analogs. Density functional calculations predicted that intramolecular reactions between generated thiyl radicals and an azido group on such model compounds would be exothermic by 33.6-41.2 kcal/mol and have low energy barriers of 10.4-13.5 kcal/mol. Reduction of the azido group occurred to give 3'-amino-3'-deoxythymidine, which was postulated to occur with thiyl radicals generated by treatment of 3'-azido-3'-deoxy-5'-O-(2,3-dimercaptopropanoyl)thymidine with 2,2'-azobis-(2-methyl-2-propionamidine) dihydrochloride. Gamma radiolysis of N(2)O-saturated aqueous solutions of AZT and cysteine produced 3'-amino-3'-deoxythymidine and thymine most likely by both radical and ionic processes. PMID:22711937

Dang, Thao P; Sobczak, Adam J; Mebel, Alexander M; Chatgilialoglu, Chryssostomos; Wnuk, Stanislaw F

2012-07-01

192

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

International Nuclear Information System (INIS)

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

193

Cloning and expression of succinic semialdehyde reductase from human brain. Identity with aflatoxin B1 aldehyde reductase.  

Science.gov (United States)

The neuromodulator gamma-hydroxybutyrate is synthesized in vivo from gamma-aminobutyrate by transamination to succinic semialdehyde and subsequent reduction of the aldehyde group. In human brain, succinic semialdehyde reductase is thought to be responsible for the conversion of succinic semialdehyde to gamma-hydroxybutyrate. In the present work, we cloned the cDNA coding for succinic semialdehyde reductase and expressed it in Escherichia coli. A data bank search indicated that the enzyme is identical with aflatoxin B1-aldehyde reductase, an enzyme implicated in the detoxification of xenobiotic carbonyl compounds. Structurally, succinic semialdehyde reductase thus belongs to the aldo-keto reductase superfamily. The recombinant protein was indistinguishable from native human brain succinic semialdehyde reductase by SDS/PAGE. In addition to succinic semialdehyde, it readily catalyzed the reduction 9,10-phenanthrene quinone, phenylglyoxal and 4-nitrobenzaldehyde, typical substrates of aflatoxin B1 aldehyde reductase. The results suggest multiple functions of succinic semialdehyde reductase/aflatoxin B1 aldehyde reductase in the biosynthesis of gamma-hydroxybutyrate and the detoxification of xenobiotic carbonyl compounds, respectively. PMID:10518801

Schaller, M; Schaffhauser, M; Sans, N; Wermuth, B

1999-11-01

194

Genetic identification of a respiratory arsenate reductase  

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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...

Saltikov, Chad W.; Newman, Dianne K.

2003-01-01

195

Influence of growth conditions on glycine reductase of Clostridium sporogenes.  

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

Venugopalan, V.

1980-01-01

196

Membrane-associated chromate reductase activity from Enterobacter cloacae.  

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Washed cells of Enterobacter cloacae HO1 reduced hexavalent chromium (chromate: CrO4(2-) anaerobically. Chromate reductase activity was preferentially associated with the membrane fraction of the cells. Right-side-out membrane vesicles prepared from E. cloacae cells showed high chromate reductase activities when ascorbate-reduced phenazine methosulfate was added as an electron donor.

Wang, P. C.; Mori, T.; Toda, K.; Ohtake, H.

1990-01-01

197

Functional and phylogenetic divergence of fungal adenylate-forming reductases.  

Science.gov (United States)

A key step in fungal L-lysine biosynthesis is catalyzed by adenylate-forming L-?-aminoadipic acid reductases, organized in domains for adenylation, thiolation, and the reduction step. However, the genomes of numerous ascomycetes and basidiomycetes contain an unexpectedly large number of additional genes encoding similar but functionally distinct enzymes. Here, we describe the functional in vitro characterization of four reductases which were heterologously produced in Escherichia coli. The Ceriporiopsis subvermispora serine reductase Nps1 features a terminal ferredoxin-NADP+ reductase (FNR) domain and thus belongs to a hitherto undescribed class of fungal multidomain enzymes. The second major class is characterized by the canonical terminal short-chain dehydrogenase/reductase domain and represented by Ceriporiopsis subvermispora Nps3 as the first biochemically characterized L-?-aminoadipic acid reductase of basidiomycete origin. Aspergillus flavus l-tyrosine reductases LnaA and LnbA are members of a distinct phylogenetic clade. Phylogenetic analysis supports the view that fungal adenylate-forming reductases are more diverse than previously recognized and belong to four distinct classes. PMID:25085485

Kalb, Daniel; Lackner, Gerald; Hoffmeister, Dirk

2014-10-01

198

Structure of an integral membrane sterol reductase from Methylomicrobium alcaliphilum.  

Science.gov (United States)

Sterols are essential biological molecules in the majority of life forms. Sterol reductases including ?(14)-sterol reductase (C14SR, also known as TM7SF2), 7-dehydrocholesterol reductase (DHCR7) and 24-dehydrocholesterol reductase (DHCR24) reduce specific carbon-carbon double bonds of the sterol moiety using a reducing cofactor during sterol biosynthesis. Lamin B receptor (LBR), an integral inner nuclear membrane protein, also contains a functional C14SR domain. Here we report the crystal structure of a ?(14)-sterol reductase (MaSR1) from the methanotrophic bacterium Methylomicrobium alcaliphilum 20Z (a homologue of human C14SR, LBR and DHCR7) with the cofactor NADPH. The enzyme contains ten transmembrane segments (TM1-10). Its catalytic domain comprises the carboxy-terminal half (containing TM6-10) and envelops two interconnected pockets, one of which faces the cytoplasm and houses NADPH, while the other one is accessible from the lipid bilayer. Comparison with a soluble steroid 5?-reductase structure suggests that the reducing end of NADPH meets the sterol substrate at the juncture of the two pockets. A sterol reductase activity assay proves that MaSR1 can reduce the double bond of a cholesterol biosynthetic intermediate, demonstrating functional conservation to human C14SR. Therefore, our structure as a prototype of integral membrane sterol reductases provides molecular insight into mutations in DHCR7 and LBR for inborn human diseases. PMID:25307054

Li, Xiaochun; Roberti, Rita; Blobel, Günter

2015-01-01

199

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

Energy Technology Data Exchange (ETDEWEB)

Voltammetric and spectroelectrochemical properties and electrocatalytic activities of thiol-derivatized phthalocyanine complexes for hydrogen production have been investigated. Voltammetric and spectroelectrochemical measurements show that while cobalt phthalocyanine complexes (CoPc) present well defined metal-based and ring-based redox processes, all other complexes give only ring-based reduction and oxidation processes. The redox processes are generally diffusion-controlled, reversible and one-electron transferred processes. The complexes bearing tetra(acetoxyethylthio) substituents represents aggregation tendency in DCM solution. Cobalt and nickel phthalocyanines are easily electrodeposited on the GCE working electrode during the repeating cycles of positive potentials. Electrocatalytic activities of electrodeposited complexes indicated that CoPc catalyzed the proton reduction via the electro-reduced [Co{sup I}Pc{sup 2-}]{sup 1-} and/or [Co{sup I}Pc{sup 3-}]{sup 2-} species depending on the pH of the aqueous solution. (author)

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

2008-06-01

200

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

International Nuclear Information System (INIS)

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

 
 
 
 
201

Derivation of structural restraints using a thiol-reactive chelator.  

Science.gov (United States)

Recognition and identification of protein folds is a prerequisite for high-throughput structural genomics. Here we demonstrate a simple protocol for covalent attachment of a short and more rigid metal-chelating tag, thiol-reactive EDTA, by chemical modification of the single cysteine residue in barnase(H102C). Conjugation of the metal-chelating tag provides the advantage of allowing a greater range of paramagnetic metal substitutions. Substitution of Yb(3+), Mn(2+), and Co(2+) permitted measurement of metal-amide proton distances, dipolar shifts, and residual dipolar couplings. Paramagnetic-derived restraints are advantageous in the NMR structure elucidation of large protein complexes and are shown sufficient for validation of homology-based fold predictions. PMID:12297302

Dvoretsky, Alex; Gaponenko, Vadim; Rosevear, Paul R

2002-09-25

202

Oxidation of dissolved elemental mercury by thiol compounds under anoxic conditions  

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-01-01

203

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

Science.gov (United States)

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

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

2010-06-23

204

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

International Nuclear Information System (INIS)

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

205

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-05-15

206

Controlled formation of gold nanoparticle dimers using multivalent thiol ligands.  

Science.gov (United States)

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

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

2011-12-20

207

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

International Nuclear Information System (INIS)

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

208

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

Science.gov (United States)

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

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

2014-02-01

209

NADH:hydroxypyruvate reductase and NADPH:glyoxylate reductase in algae: partial purification and characterization from Chlamydomonas reinhardtii.  

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Hydroxypyruvate and glyoxylate reductase activities were measured in extracts from the unicellular green algae, Chlamydomonas reinhardtii, Chlorella vulgaris, Chlorella miniata, and Dunaliella tertiolecta. Only trace levels of these activities were detectable in the blue-green algae, Anabaena variabilis and Synechococcus leopoliensis. A NADH-dependent hydroxypyruvate reductase was purified 130-fold from Chlamydomonas to a specific activity of 18 mumol NADH oxidized X min-1 X mg protein-1. The pH optimum was 5.0 to 7.0 in the presence of phosphate and the Km(hydroxypyruvate) was 0.05 mM. Substrate inhibition by hydroxypyruvate could be partially relieved by phosphate. The molecular weight, estimated by gel filtration, was 96,000. NADH-dependent glyoxylate reductase activity copurified with the hydroxypyruvate reductase. The Km(glyoxylate) was 10 mM, and the pH optimum was 4.5 to 8.5. A specific NADPH:glyoxylate reductase was also partially purified which did not reduce hydroxypyruvate or pyruvate. The NADPH:glyoxylate reductase had a Km(glyoxylate) of 0.1 mM and a pH optimum of 5.0 to 9.5. These reductases were compared with the pyruvate reductase of Chlamydomonas which also catalyzes the reduction of both hydroxypyruvate and glyoxylate. PMID:3545081

Husic, D W; Tolbert, N E

1987-02-01

210

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

International Nuclear Information System (INIS)

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

211

Thiol and sulfenic acid oxidation of AhpE, the one-cysteine peroxiredoxin from Mycobacterium tuberculosis: kinetics, acidity constants, and conformational dynamics.  

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Drug resistance and virulence of Mycobacterium tuberculosis are partially related to the pathogen's antioxidant systems. Peroxide detoxification in this bacterium is achieved by the heme-containing catalase peroxidase and different two-cysteine peroxiredoxins. M. tuberculosis genome also codifies for a putative one-cysteine peroxiredoxin, alkyl hydroperoxide reductase E (MtAhpE). Its expression was previously demonstrated at a transcriptional level, and the crystallographic structure of the recombinant protein was resolved under reduced and oxidized states. Herein, we report that the conformation of MtAhpE changed depending on its single cysteine redox state, as reflected by different tryptophan fluorescence properties and changes in quaternary structure. Dynamics of fluorescence changes, complemented by competition kinetic assays, were used to perform protein functional studies. MtAhpE reduced peroxynitrite 2 orders of magnitude faster than hydrogen peroxide (1.9 x 10(7) M(-1) s(-1) vs 8.2 x 10(4) M(-1) s(-1) at pH 7.4 and 25 degrees C, respectively). The latter also caused cysteine overoxidation to sulfinic acid, but at much slower rate constant (40 M(-1) s(-1)). The pK(a) of the thiol in the reduced enzyme was 5.2, more than one unit lower than that of the sulfenic acid in the oxidized enzyme. The pH profile of hydrogen peroxide-mediated thiol and sulfenic acid oxidations indicated thiolate and sulfenate as the reacting species. The formation of sulfenic acid as well as the catalytic peroxidase activity of MtAhpE was demonstrated using the artificial reducing substrate thionitrobenzoate. Taken together, our results indicate that MtAhpE is a relevant component in the antioxidant repertoire of M. tuberculosis probably involved in peroxide and specially peroxynitrite detoxification. PMID:19737009

Hugo, Martín; Turell, Lucía; Manta, Bruno; Botti, Horacio; Monteiro, Gisele; Netto, Luis E S; Alvarez, Beatriz; Radi, Rafael; Trujillo, Madia

2009-10-13

212

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

International Nuclear Information System (INIS)

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

213

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

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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.

Naphtali A. O’Connor

2014-06-01

214

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

International Nuclear Information System (INIS)

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

215

The effect of the molecular structure of thiols on the mechanism of their radical scavenging  

International Nuclear Information System (INIS)

Experiments on H atom scavenging by alkanethiols in ?-irradiated aqueous solutions have confirmed that the reaction products depend on thiol structure. The percentage of H abstraction decreases with increasing branching at the carbon atom ? to sulfur while -SH abstraction simultaneously increases. Methyl and ethyl radicals appear to react only by H abstraction from the thiol group since the yields of methane and ethane are independent of thiol structure. There is no significant temperature dependent of the H2 and H2S yields over the range 0 to 500C for aqueous solutions of cysteine and penicillamine. (author)

216

Hydrogen atom transfer from SH group of thiols to uracil OH-adducts in radiolysis  

International Nuclear Information System (INIS)

Thiol radiation protection mechanism connected with hydrogen atom transfer from SH group to uracil OH-adducts in its ?-radiolysis is investigated. Yields of final products of 5-hydroxydihydrouracil (·U-50H) and 6-hydroxydihydrouracil (·U-60H) transfer reaction are measured. Cysteamine hydrochloride, cysteine and reduced glutathione are used as thiols. Under radiolysis conditions only C5-OH uracil adduct is shown to react with thiols forming 5-hydroxydihydrouracil, and cysteine and glutathione are more effective than cysteamine in respect with the hydrogen atom transfer reaction

217

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

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

Lee Gwang

2010-01-01

218

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

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Background Nonribosomal peptide synthetases (NRPSs) are multienzymatic, multidomain megasynthases involved in the biosynthesis of pharmaceutically important nonribosomal peptides. The peptaibol synthetase from Trichoderma virens (TPS) is an important member of the NRPS family that exhibits antifungal properties. The majority of the NRPSs terminate peptide synthesis with the thioesterase (TE) domain, which either hydrolyzes the thioester linkage, releasing the free peptic acid, or catalyzes the intramolecular macrocyclization to produce a macrolactone product. TPS is an important NRPS that does not encompass a TE domain, but rather a reductase domain (R domain) to release the mature peptide product reductively with the aid of a NADPH cofactor. However, the catalytic mechanism of the reductase domain has not yet been elucidated. Results We present here a three-dimensional (3D) model of the reductase domain based on the crystal structure of vestitone reductase (VR). VR belongs to the short-chain dehydrogenase/reductase (SDR) superfamily and is responsible for the nicotinamide dinucleotide phosphate (NADPH)-dependent reduction of the substrate into its corresponding secondary alcohol product. The binding sites of the probable linear substrates, alamethicin, trichotoxin, antiamoebin I, chrysopermin C and gramicidin, were identified within the modeled R domain using multiple docking approaches. The docking results of the ligand in the active site of the R domain showed that reductase side chains have a high affinity towards ligand binding, while the thioester oxygen of each substrate forms a hydrogen bond with the OH group of Tyr176 and the thiol group of the substrate is closer to the Glu220. The modeling and docking studies revealed the reaction mechanism of reduction of thioester into a primary alcohol. Conclusion Peptaibol biosynthesis incorporates a single R domain, which appears to catalyze the four-electron reduction reaction of a peptidyl carrier protein (PCP)-bound peptide to its corresponding primary alcohol. Analysis of R domains present in the non-redundant (nr) database of the NCBI showed that the R domain always resides in the last NRPS module and is involved in either a two or four-electron reduction reaction. PMID:20067617

2010-01-01

219

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

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

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

2012-09-15

220

The role of ferredoxin:thioredoxin reductase/thioredoxin m in seed germination and the connection between this system and copper ion toxicity.  

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Seed germination is highly sensitive to changes in the surrounding environment. This work examined the impact of imbibition with copper solution on the germination rate and behavior of some enzyme capacities involved in stress response. Chickpea (Cicer arietinum L.) seeds were germinated at 25°C in the dark for 7 days of imbibition with distilled water or an aqueous solution of chloride salt of 100 or 500?M CuCl2. The exposure of seeds to copper (Cu(2+)) induced changes in the antioxidant status. In Cu-treated seeds, the non-protein thiols (—SHNP) pool and ferredoxin:thioredoxin reductase (FTR) expression and activity increased. Cysteinyl sulfurs in the thioredoxin (Trx) function as ligands for metal ions. The accumulation of Cu(2+) inhibited seed germination and embryo growth. It appears that the FTR system mediates a novel form of redox signaling in plants under copper excess. PMID:25173453

Smiri, M; Missaoui, T

2014-11-01

 
 
 
 
221

Enhanced silver nanoparticle synthesis by optimization of nitrate reductase activity.  

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Nanostructure materials are attracting a great deal of attention because of their potential for achieving specific processes and selectivity, especially in biological and pharmaceutical applications. The generation of silver nanoparticles using optimized nitrate reductase for the reduction of Ag(+) with the retention of enzymatic activity in the complex is being reported. This report involves the optimization of enzyme activity to bring about enhanced nanoparticle synthesis. Response surface methodology and central composite rotary design (CCRD) were employed to optimize a fermentation medium for the production of nitrate reductase by Bacillus licheniformis at pH 8. The four variables involved in the study of nitrate reductase were Glucose, Peptone, Yeast extract and KNO(3). Glucose had a significant effect on nitrate reductase production. The optimized medium containing (%) Glucose: 1.5, Peptone: 1, Yeast extract: 0.35 and KNO(3): 0.35 resulted in a nitrate reductase activity of 452.206 U/ml which is same as that of the central level. The medium A (showing least nitrate reductase activity) and the medium B (showing maximum nitrate reductase activity) were compared for the synthesis. Spectrophotometric analysis revealed that the particles exhibited a peak at 431 nm and the A(431) for the medium B was 2-fold greater than that of the medium A. The particles were also characterized using TEM. The particles synthesized using the optimized enzyme activity ranged from 10 to 80 nm and therefore can be extended to various medicinal applications. PMID:19796922

Vaidyanathan, Ramanathan; Gopalram, Shubaash; Kalishwaralal, Kalimuthu; Deepak, Venkataraman; Pandian, Sureshbabu Ram Kumar; Gurunathan, Sangiliyandi

2010-01-01

222

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

International Nuclear Information System (INIS)

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

223

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

DEFF Research Database (Denmark)

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

Zhuang, Guisheng; Jensen, Thomas Glasdam

2011-01-01

224

Oxidative nucleophilic strategy for synthesis of thiocyanates and trifluoromethyl sulfides from thiols.  

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Thiocyanates and trifluoromethyl sulfides are important compounds and have classically been synthesized via multistep procedures together with the formation of significant amounts of byproducts. Herein, we demonstrate an oxidative nucleophilic strategy for the synthesis of thiocyanates and trifluoromethyl sulfides from thiol starting materials using nucleophilic reagents such as TMSCN and TMSCF3 (TMS = trimethylsilyl). In the presence of a 2 × 2 manganese oxide-based octahedral molecular sieve (OMS-2) and potassium fluoride (KF), various structurally diverse thiocyanates and trifluoromethyl sulfides could be synthesized in almost quantitative yields (typically >90%). The presented cyanation and trifluoromethylation reactions proceed through the OMS-2-catalyzed oxidative homocoupling of thiols to give disulfides followed by nucleophilic bond cleavage to produce the desired compounds and thiolate species (herein S-trimethylsilylated thiols). OMS-2 can catalyze oxidative homocoupling of the thiolate species, thus resulting formally in the quantitative production of thiocyanates and trifluoromethyl sulfides from thiols. PMID:25297894

Yamaguchi, Kazuya; Sakagami, Konomi; Miyamoto, Yumi; Jin, Xiongjie; Mizuno, Noritaka

2014-12-01

225

Novel pyrazoline-based fluorescent probe for detecting thiols and its application in cells  

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A new compound, N-(4-(1,5-diphenyl-4,5-dihydro-1H-pyrazol-3-yl)phenyl)-acrylamide (probe L), was designed and synthesized as a highly sensitive and selective fluorescent probe for recognizing and detecting thiol from other amino acids. On being mixed with thiol in buffered DMSO:HEPES = 1:1 solution at pH 7.4, the probe exhibited the blue emission at 474 nm. This probe is very sensitive and displayed a linear fluorescence off-on response to thiol. The fluorescence emission of the probe is pH independent in the physiological pH range. Living cell imaging of HeLa cells confirmed its cell permeability and its ability to selectively detect thiol in cells. The structure of the probe was characterized by IR, NMR and HRMS spectroscopy analysis.

Zhang, Rong-Rong; Zhang, Jin-Feng; Wang, Sheng-Qing; Cheng, Yan-Long; Miao, Jun-Ying; Zhao, Bao-Xiang

2015-02-01

226

Degradable thiol-acrylate hydrogels as tunable matrices for three-dimensional hepatic culture.  

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A degradable poly(ethylene glycol)-diacrylate (PEGDA) hydrogel system was developed using simple macromer formulations and visible light initiated thiol-acrylate photopolymerization. In addition to PEGDA, other components in this gelation system include eosin-Y as a photo-sensitizer, bi-functional thiol (dithiothreitol, DTT) as a dual-purpose co-initiator and cross-linker, and N-vinylpyrrolidone (NVP) as a co-monomer. Gelation was achieved through a mixed-mode step-chain growth polymerization mechanism under bright visible light exposure. Increasing photo-sensitizer or NVP concentrations accelerated photo-crosslinking and increased final gel stiffness. Increasing bi-functional thiol content in the prepolymer solution only increased gel stiffness to some degree. As the concentration of thiol surpassed certain range, thiol-mediated chain-transfer events caused thiol-acrylate gels to form with lower degree of cross-linking. Pendant peptide, such as integrin ligand RGDS, was more effectively immobilized in the network via a thiol-acrylate reaction (using thiol-bearing peptide Ac-CRGDS. Underline indicates cross-linkable motif) than through homo-polymerization of acrylated peptide (e.g., acryl-RGDS). The incorporation of pendant peptide comes with the expense of a lower degree of gel cross-linking, which was rectified by increasing co-monomer NVP content. Without the use of any readily degradable macromer, these visible light initiated mixed-mode cross-linked hydrogels degraded hydrolytically due to the formation of thiol-ether-ester bonds following thiol-acrylate reactions. An exponential growth relationship was identified between the hydrolytic degradation rate and bifunctional thiol content in the prepolymer solution. Finally, we evaluated the cytocompatibility of these mixed-mode cross-linked degradable hydrogels using in situ encapsulation of hepatocellular carcinoma Huh7 cells. Encapsulated Huh7 cells remained alive and proliferated as time to form cell clusters. The addition of NVP at a higher concentration (0.3%) did not affect Huh7 cell viability but resulted in reduction of cell metabolic activity, which was accompanied by an elevated urea secretion from the encapsulated cells. PMID:24288169

Hao, Yiting; Lin, Chien-Chi

2014-11-01

227

Different functions between human monomeric carbonyl reductase 3 and carbonyl reductase 1.  

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Monomeric carbonyl reductases (CBRs) are enzymes that catalyze the reduction of many endogenous and xenobiotic carbonyl compounds, including steroids and prostaglandins. There are two monomeric CBR genes in the human genome, cbr1 and cbr3, which exhibit high homology in their amino acid sequences. Human CBR1 (hCBR1) is known as prostaglandin 9-keto reductase and 15-hydroxy dehydrogenase, and regulates the metastasis of cancer cells through the regulation of prostaglandin metabolism. However, there is little information concerning the molecular and enzymatic characteristics of human CBR3 (hCBR3). The present study demonstrated the tissue and cellular localization, and catalytic activity of hCBR3. Semi-quantitative PCR revealed the ubiquitous but lower expression of hCBR3 compared with that of hCBR1. Bacterially expressed hCBR3 exhibited limited catalytic activity toward menadione, 4-benzoylpyridine, and 4-nitrobenzaldehyde. Similar results were obtained when the cell lysates of CBR-overexpressing HEK293 cells were examined. Additionally, neither the prostaglandin 9-keto reductase nor the 15-hydroxy dehydrogenase activities of hCBR3 were significant. Immunofluorescence staining revealed that ectopically expressed hCBR3 proteins were localized in the cytosol of HEK293 cells. These results suggested that hCBR3 and hCBR1 play distinct physiological roles. This study expands our understanding of the relationship between the two monomeric hCBRs and prostaglandin metabolism. PMID:18493841

Miura, Takeshi; Nishinaka, Toru; Terada, Tomoyuki

2008-08-01

228

Effects of buried charged groups on cysteine thiol ionization and reactivity in Escherichia coli thioredoxin: structural and functional characterization of mutants of Asp 26 and Lys 57.  

Science.gov (United States)

To investigate the role of Asp 26 and Lys 57, two conserved, buried residues, in the redox mechanism of Escherichia coli thioredoxin (Trx), three mutant proteins, Asp 26 --> Ala (D26A), Lys 57 --> Met (K57M), and the double mutant D26A/K57M, were prepared, replacing the charged amino acids with hydrophobic residues with similar sizes. Both the oxidized (Trx-S2) and reduced [Trx-(SH)2] forms of the mutant thioredoxins are fully folded and similar in overall structure to the wild-type protein (wt). The structure of the active site hydrophobic surface is unchanged by the mutation of Asp 26 and Lys 57, since DNA polymerase activity in the 1:1 complex of the T7 gene 5 protein and mutant Trx-(SH)2 shows similar Kd values (approximately 5 nM) for both mutants and wt. In contrast, redox reactions involving thioredoxin as a catalyst of the reduction of disulfides or oxidation of dithiols are strongly affected by the mutations. In the reaction of Trx-S2 with thioredoxin reductase at pH 8.0, the kcat/Km value for the D26A mutant is decreased by a factor of 10 from that of wt, while the value for the D26A/K57M mutant is reduced 40-fold. The activity of Trx-(SH)2 as a protein disulfide reductase was measured with insulin, using fluorescence to detect oxidation of thioredoxin. At 15 degrees C and pH 8.0, both the D26A and K57M mutants showed 5--10-fold decreases in rates of reaction compared to those of the wild type, and the pH-rate profiles for the mutants were shifted 1 (K57M) and 2 (D26A) units to higher pH compared with the wt curve. NMR measurements for the three mutant proteins indicate that the proteins have the same global fold as that of the wild type, although changes in the chemical shifts of a number of resonances indicate local structural changes in the active site region. The resonances of oxidized D26A and D26A/K57M are pH-independent between pH 6.0 and 10.0, confirming the identification of the active site group titrating with a pKa of 7.5 in wt Trx-S2 as Asp 26. A profound change in the pKa of Asp 26, from 7.5 in the wild type to 9.4 in the mutant, is observed for K57M Trx-S2. The pH-dependent behavior of the resonances is affected in all mutant Trx-(SH)2 proteins. A single pKa shifted to higher values is observed on both the Cys 32 and Cys 35 Cbeta resonances. Ultraviolet absorbance measurements (A240) as a function of pH for wt Trx-(SH)2 demonstrate that the cysteine thiols titrate with apparent pK(a)s of about 7.1 and 9.9. The mutant proteins each show a single transition in the A240 measurements, with a midpoint at pH 7.8-8.0, consistent with the NMR results. The change in absorbance at 240 nm with increasing pH indicates that the number of thiols titrating in each mutant is greater than one but less than two. It is clear that both thiol pK(a)s have been significantly shifted by the mutations. The Cys 32 pKa is moved from 7.1 in wt to 7.8-8.0 in the mutants. The value of the Cys 35 pKa either is indistinguishable from that of Cys 32, thus accounting for more than one thiol titrating in the UV absorbance measurements or else is shifted to much higher pHs (> 10) where its transition is masked in both UV and NMR measurements by the effects of ionization of the tyrosine residues and unfolding of the protein. Our results strongly suggest that the buried Asp 26 carboxyl and Lys 57 epsilon-amino groups significantly affect the pK(a)s of the active site thiols, particularly that of the exposed low-pKa thiol Cys 32, thereby enhancing the rates of thiol-disulfide reactions at physiological pH. PMID:9054569

Dyson, H J; Jeng, M F; Tennant, L L; Slaby, I; Lindell, M; Cui, D S; Kuprin, S; Holmgren, A

1997-03-01

229

Modulation of the ribonucleotide reductase M1-gemcitabine interaction in vivo by N-ethylmaleimide  

Energy Technology Data Exchange (ETDEWEB)

Highlights: {yields} Gemcitabine induces a RRM1 conformational change in tumor cell lines and xenografts. {yields} The 110 kDa RRM1 is unique to gemcitabine interaction among 12 cytotoxic agents. {yields} The 110 kDa RRM1 can be stabilized by the thiol alkylator N-ethylmaleimide. {yields} C218A, C429A, and E431A mutations in RRM1 abolished the conformational change. {yields} The 110 kDa RRM1 may be a specific biomarker of gemcitabine's therapeutic efficacy. -- Abstract: Ribonucleotide reductase M1 (RRM1) is the regulatory subunit of the holoenzyme that catalyzes the conversion of ribonucleotides to 2'-deoxyribonucleotides. Its function is indispensible in cell proliferation and DNA repair. It also serves as a biomarker of therapeutic efficacy of the antimetabolite drug gemcitabine (2',2'-difluoro-2'-deoxycytidine) in various malignancies. However, a mechanistic explanation remains to be determined. This study investigated how the alkylating agent N-ethylmaleimide (NEM) interacts with the inhibitory activity of gemcitabine on its target protein RRM1 in vivo. We found, when cells were treated with gemcitabine in the presence of NEM, a novel 110 kDa band, along with the 90 kDa native RRM1 band, appeared in immunoblots. This 110 kDa band was identified as RRM1 by mass spectrometry (LC-MS/MS) and represented a conformational change resulting from covalent labeling by gemcitabine. It is specific to gemcitabine/NEM, among 11 other chemotherapy drugs tested. It was also detectable in human tumor xenografts in mice treated with gemcitabine. Among mutations of seven residues essential for RRM1 function, C218A, C429A, and E431A abolished the conformational change, while N427A, C787A, and C790A diminished it. C444A was unique since it was able to alter the conformation even in absence of gemcitabine treatment. We conclude that the thiol alkylator NEM can stabilize the gemcitabine-induced conformational change of RRM1, and this stabilized RRM1 conformation has the potential to serve as a specific biomarker of gemcitabine's therapeutic efficacy.

Chen, Zhengming; Zhou, Jun; Zhang, Yingtao [Developmental Therapeutics Program, Karmanos Cancer Institute, Detroit, MI (United States); Bepler, Gerold, E-mail: beplerg@karmanos.org [Developmental Therapeutics Program, Karmanos Cancer Institute, Detroit, MI (United States)

2011-09-23

230

7-Dehydrocholesterol reductase - Wikipedia, the free encyclopedia [Gene Wiki  

Full Text Available 7-Dehydrocholesterol reductase - Wikipedia, the free encyclopediaa:lang(ar),a:lang(kk-arab),a:la ... .[1]Pathology[edit]A deficiency is associated with Smith -Lemli-Opitz syndrome.[4]Interactive pathway map[ed ... man sterol delta7-reductase gene at 11q12-13 cause Smith -Lemli-Opitz syndrome". Am. J. Hum. Genet. 63 (1): ... atel SB (November 2005). "Recent insights into the Smith -Lemli-Opitz syndrome". Clin. Genet. 68 (5): 383–91 ... etic aspects of 7-dehydrocholesterol reductase and Smith -Lemli-Opitz syndrome.". Biochim. Biophys. Acta 152 ...

231

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Lyumugabe Loshima, Franc?ois

2012-01-01

232

The synthesis of thiols, dithiols, isocyanides, diisocyanides, and isocyanothiols. Their use as molecular wires and interconnects  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A study investigating the use of thiols, dithiols, isocyanides, diisocyanides, and isocyano thiols. Several of these molecules have been synthesized and characterized by standard methods. They have then been used to form self-assembled monolayers on gold surfaces. These SAMs were characterized by reflectance absorbtion infrared spectroscopy, surface enhanced Raman spectroscopy, advancing water contact angle measurements, and ellipsometery. SAMs in the case of the rigid p-phenyl or phenyl ethy...

Henderson, Jason Ivan

1997-01-01

233

Stress Relaxation by Addition-Fragmentation Chain Transfer in Highly Crosslinked Thiol-Yne Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Radical mediated addition-fragmentation chain transfer of mid-chain allyl sulfide functional groups was utilized to reduce polymerization-induced shrinkage stress in thiol-yne step-growth photopolymerization reactions. In previous studies, the addition-fragmentation of allyl sulfide during the polymerization of a step-growth thiol-ene network demonstrated reduced polymerization stress; however, the glass transition temperature of the material was well below room temperature (~ ?20°C). Many...

Park, Hee Young; Kloxin, Christopher J.; Scott, Timothy F.; Bowman, Christopher N.

2010-01-01

234

Genetic Determinants of Volatile-Thiol Release by Saccharomyces cerevisiae during Wine Fermentation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Volatile thiols, particularly 4-mercapto-4-methylpentan-2-one (4MMP), make an important contribution to the aroma of wine. During wine fermentation, Saccharomyces cerevisiae mediates the cleavage of a nonvolatile cysteinylated precursor in grape juice (Cys-4MMP) to release the volatile thiol 4MMP. Carbon-sulfur lyases are anticipated to be involved in this reaction. To establish the mechanism of 4MMP release and to develop strains that modulate its release, the effect of deleting genes encodi...

Howell, Kate S.; Klein, Mathias; Swiegers, Jan H.; Hayasaka, Yoji; Elsey, Gordon M.; Fleet, Graham H.; Høj, Peter B.; Pretorius, Isak S.; Barros Lopes, Miguel A.

2005-01-01

235

Synthesis and Characterization of Thiol-Ene Functionalized Siloxanes and Evaluation of their Crosslinked Network Properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Three types of linear thiol-functionalized siloxane oligomers and three types of ene-functionalized oligomers were synthesized and subsequently photopolymerized. Within each type of thiol-functionalized oligomer, the ratio of mercaptan repeat units to non-reactive phenyl repeat units was varied to manipulate both the crosslink density and the degree of secondary interactions through pi-pi stacking. Similarly, the repeat units of the three ene-functionalized oligomers are composed of allyl-fun...

Cole, Megan A.; Bowman, Christopher N.

2012-01-01

236

Endoplasmic Reticulum Thiol Oxidase Deficiency Leads to Ascorbic Acid Depletion and Noncanonical Scurvy in Mice  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Endoplasmic reticulum (ER) thiol oxidases initiate a disulfide relay to oxidatively fold secreted proteins. We found that combined loss-of-function mutations in genes encoding the ER thiol oxidases ERO1?, ERO1?, and PRDX4 compromised the extracellular matrix in mice and interfered with the intracellular maturation of procollagen. These severe abnormalities were associated with an unexpectedly modest delay in disulfide bond formation in secreted proteins but a profound, 5-fold lower procolla...

Zito, Ester; Hansen, Henning gram; Yeo, Giles s H.; Fujii, Junichi; Ron, David

2012-01-01

237

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Claudio Larosa; Enrico Stura; Roberto Eggenhöffner; Claudio Nicolini

2009-01-01

238

Microwave assisted oxidative coupling of thiols to symmetrical disulfides with tripropylammonium fluorochromate(VI) (TPAFC)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Tripropylammonium fluorochromate(VI) (TPAFC) is an efficient and novel reagent, which can be prepared easily and oxidizes thiols to the corresponding disulfides, quickly. The reactions are performed cleanly and are controlled to stop at the disulfide stage, without over-oxidation or side products. Coupling of thiols to their corresponding disulfides, was studied in solution at room temperature and under conditions using a minimal amount of solvent under microwave irradiation. The easy procedu...

Shahriare Ghammamy; Mohammad Kazem Mohammadi

2012-01-01

239

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Bansal Amrit; Kaur Anand

2009-01-01

240

Kinetics and Thioredoxin Specificity of Thiol Modulation of the Chloroplast H+-ATPase  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The kinetics of thiol modulation of the chloroplast H+-ATPase (CF0CF1) in membrana were analyzed by employing thioredoxins that were kept reduced by 0.1 mM dithiothreitol. The kinetics of thiol modulation depend on the extent of the proton gradient. The process is an exponential function of the thioredoxin concentration and reaction time and can be described by an irreversible second order reaction. The results indicate that the formation of the complex...

Schwarz, Oliver; Schu?rmann, Peter; Strotmann, Heinrich

2007-01-01

 
 
 
 
241

Posttranslational glutathiolation of aldose reductase (AKR1B1); a possible mechanism of protein recovery from S-nitrosylation  

Science.gov (United States)

Nitric oxide (NO) is an important regulator of the catalytic activity of aldose reductase (AR). It reacts with the active site cysteines of AR and this reaction results in the formation of several kinetically distinct forms of the protein. The catalytic activity of AR is increased in the ischemic heart and this increase in activity is associated with NO-dependent modification of AR. During reperfusion, the enzyme reverts back to its un-activated form. Although, AR activation has been linked to thiol oxidation, the mechanisms of de-activation remain unclear. Here we report that treatment of recombinant human AR (AKR1B1) by a non-thiol based NO-donor (DEANO) results in activation and S-nitrosylation of the protein. The nitrosylated (ARSNO), but not the reduced (ARSH), protein reacted with reduced glutathione (GSH) and this reaction resulted in the formation of glutathiolated AR (ARSSG). The modification of AR by NO was site-specific at Cys-298 and was not affected by selective mutation of the neighboring residue, Cys303 to an alanine. Incubation of the glutathiolated AR (AR-SSG) with GSH resulted in the regeneration of the reduced form of the protein (ARSH). Treatment of nitrosylated AR (AR-SNO) with ascorbic acid also led to the conversion of the protein to its reduced form. These observations suggest that intracellular reductants such as GSH and ascorbate could convert the nitrosylated form of AR to its basal or reduced state. In general, such reductive reactions might represent a common mechanism for denitrosylating proteins or an “off” switch in NO-mediated signaling pathways involving protein S-nitrosylation reactions. PMID:19061876

Baba, Shahid Pervez; Wetzelberger, Karin; Hoetker, Joseph David; Bhatnagar, Aruni

2010-01-01

242

Conformational Analysis of Oxidized Peptide Fragments of the C-terminal Redox Center in Thioredoxin Reductases by NMR Spectroscopy†  

Science.gov (United States)

Vicinal disulfide rings (VDRs) occur when a disulfide bond forms between adjacent cysteine residues in a protein and results in a rare eight-membered ring structure. This eight-membered ring has been found to exist in four major conformations in solution, divided between cis and trans conformers. Some selenoenzymes use a special type of VDR in which selenium replaces sulfur, generating a vicinal selenosulfide ring (VSeSR). Here we provide evidence that this substitution reduces ring strain, resulting in a strong preference for the trans conformation relative to cis in a VSeSR (cis:trans – 9:91). This was determined by using the “?-gauche effect” which makes use of both 1H-NMR and two-dimensional (2D) NMR techniques for determining the amide bond conformeric ratio. The presence of selenium in a VSeSR also lowers the dihedral strain energy (DSE) of the selenosulfide bond relative to the disulfide bond of VDRs. While cis amide geometry decreases strain on the amide bond, it increases strain on the scissile disulfide bond of the VDR found in thioredoxin reductase from D. melanogaster (DmTR). We hypothesize that the cis conformation of the VDR is the catalytically competent conformer for thiol/disulfide exchange. This hypothesis was investigated by computing the DSE of VDR and VSeSR conformers, the structure of which was determined by 2D NMR spectroscopy and energy minimization. The computed values of the VDR from DmTR are 16.5 kJ/mol DSE and 14.3 kJ/mol for the C+ and T? conformers, respectively, supporting the hypothesis that the enzyme uses the C+ conformer for thiol/disulfide exchange. PMID:24599608

Ruggles, Erik L.; Deker, P. Bruce; Hondal, Robert J.

2014-01-01

243

Mercury Binding Sites in Thiol-Functionalized Mesostructured Silica  

International Nuclear Information System (INIS)

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 (Hgrcury 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.

244

“Turn-on” fluorescence probe integrated polymer nanoparticles for sensing biological thiol molecules  

Science.gov (United States)

A ``turn-on'' thiol-responsive fluorescence probe was synthesized and integrated into polymeric nanoparticles for sensing intracellular thiols. There is a photo-induced electron transfer process in the off state of the probe, and this process is terminated upon the reaction with thiol compounds. Configuration interaction singles (CIS) calculation was performed to confirm the mechanism of this process. A series of sensing studies were carried out, showing that the probe-integrated nanoparticles were highly selective towards biological thiol compounds over non-thiolated amino acids. Kinetic studies were also performed to investigate the relative reaction rate between the probe and the thiolated amino acids. Subsequently, the Gibbs free energy of the reactions was explored by means of the electrochemical method. Finally, the detection system was employed for sensing intracellular thiols in cancer cells, and the sensing selectivity could be further enhanced with the use of a cancer cell-targeting ligand in the nanoparticles. This development paves a path for the sensing and detection of biological thiols, serving as a potential diagnostic tool in the future.

Ang, Chung Yen; Tan, Si Yu; Lu, Yunpeng; Bai, Linyi; Li, Menghuan; Li, Peizhou; Zhang, Quan; Selvan, Subramanian Tamil; Zhao, Yanli

2014-11-01

245

Purification, Characterization, and Effect of Thiol Compounds on Activity of the Erwinia carotovora L-Asparaginase.  

Science.gov (United States)

L-asparaginase was extracted from Erwinia carotovora and purified by ammonium sulfate fractionation (60-70%), Sephadex G-100, CM cellulose, and DEAE sephadex chromatography. The apparent Mr of enzyme under nondenaturing and denaturing conditions was 150?kDa and 37 ± 0.5?kDa, respectively. L-asparaginase activity was studied in presence of thiols, namely, L-cystine (Cys), L-methionine (Met), N-acetyl cysteine (NAC), and reduced glutathione (GSH). Kinetic parameters in presence of thiols (10-400 ?M) showed an increase in V(max) values (2000, 2223, 2380, 2500, and control 1666.7??moles mg(-1)min(-1)) and a decrease in K(m) values (0.086, 0.076, 0.062, 0.055 and control 0.098?mM) indicating nonessential mode of activation. K(A) values displayed propensity to bind thiols. A decrease in V(max)/K(m) ratio in concentration plots showed inverse relationship between free thiol groups (NAC and GSH) and bound thiol group (Cys and Met). Enzyme activity was enhanced in presence of thiol protecting reagents like dithiothreitol (DTT), 2-mercaptoethanol (2-ME), and GSH, but inhibited by p-chloromercurybenzoate (PCMB) and iodoacetamide (IA). PMID:21048860

Warangkar, Suchita C; Khobragade, Chandrahas N

2010-01-01

246

The role of the thiol group in protein modification with methylglyoxal  

Directory of Open Access Journals (Sweden)

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

JELENA M. A?IMOVI?

2009-08-01

247

"Turn-on" fluorescence probe integrated polymer nanoparticles for sensing biological thiol molecules.  

Science.gov (United States)

A "turn-on" thiol-responsive fluorescence probe was synthesized and integrated into polymeric nanoparticles for sensing intracellular thiols. There is a photo-induced electron transfer process in the off state of the probe, and this process is terminated upon the reaction with thiol compounds. Configuration interaction singles (CIS) calculation was performed to confirm the mechanism of this process. A series of sensing studies were carried out, showing that the probe-integrated nanoparticles were highly selective towards biological thiol compounds over non-thiolated amino acids. Kinetic studies were also performed to investigate the relative reaction rate between the probe and the thiolated amino acids. Subsequently, the Gibbs free energy of the reactions was explored by means of the electrochemical method. Finally, the detection system was employed for sensing intracellular thiols in cancer cells, and the sensing selectivity could be further enhanced with the use of a cancer cell-targeting ligand in the nanoparticles. This development paves a path for the sensing and detection of biological thiols, serving as a potential diagnostic tool in the future. PMID:25394758

Ang, Chung Yen; Tan, Si Yu; Lu, Yunpeng; Bai, Linyi; Li, Menghuan; Li, Peizhou; Zhang, Quan; Selvan, Subramanian Tamil; Zhao, Yanli

2014-01-01

248

“Turn-on” fluorescence probe integrated polymer nanoparticles for sensing biological thiol molecules  

Science.gov (United States)

A “turn-on” thiol-responsive fluorescence probe was synthesized and integrated into polymeric nanoparticles for sensing intracellular thiols. There is a photo-induced electron transfer process in the off state of the probe, and this process is terminated upon the reaction with thiol compounds. Configuration interaction singles (CIS) calculation was performed to confirm the mechanism of this process. A series of sensing studies were carried out, showing that the probe-integrated nanoparticles were highly selective towards biological thiol compounds over non-thiolated amino acids. Kinetic studies were also performed to investigate the relative reaction rate between the probe and the thiolated amino acids. Subsequently, the Gibbs free energy of the reactions was explored by means of the electrochemical method. Finally, the detection system was employed for sensing intracellular thiols in cancer cells, and the sensing selectivity could be further enhanced with the use of a cancer cell-targeting ligand in the nanoparticles. This development paves a path for the sensing and detection of biological thiols, serving as a potential diagnostic tool in the future. PMID:25394758

Ang, Chung Yen; Tan, Si Yu; Lu, Yunpeng; Bai, Linyi; Li, Menghuan; Li, Peizhou; Zhang, Quan; Selvan, Subramanian Tamil; Zhao, Yanli

2014-01-01

249

Solubilization and Resolution of the Membrane-Bound Nitrite Reductase from Paracoccus Halodenitrificans into Nitrite and Nitric Oxide Reductases  

Science.gov (United States)

Membranes prepared from Paracoccus halodenitrificans reduced nitrite or nitric oxide to nitrous oxide. Extraction of these membranes with the detergent CHAPSO [3-(3-Chlolamidoporopyldimethylammonio)-1-(2- hydroxy-1-propanesulfonate)], followed by ammonium sulfate fractionation of the solubilized proteins, resulted in the separation of nitrite and nitric oxide reductase activities. The fraction containing nitrite reductase activity spectrally resembled a cd-type cytochrome. Several cytochromes were detected in the nitric oxide reductase fraction. Which, if any, of these cytochromes is associated with the reduction of nitric oxide is not clear at this time.

Grant, Michael A.; Cronin, Sonja E.; Hochstein, Lawrence I.

1984-01-01

250

(Processing and targeting of the thiol protease aleurain)  

Energy Technology Data Exchange (ETDEWEB)

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

Rogers, J.C.

1990-01-01

251

Adsorption kinetic process of thiol ligands on gold nanocrystals.  

Science.gov (United States)

Understanding the kinetic mechanism during ligand adsorption on gold nanocrystals is important for designing and fine-tuning their properties and implications. Here, we report a kinetic study on the adsorption process of dodecanethiol ligands on Au nanocrystals of 3.3 nm by an in situ time-resolved X-ray absorption fine structure technique. A two-step process of dodecanethiol adsorption on Au NC surfaces is proposed based on the obtained ligand coverage, which shows a quick increase from 0 to 0.40 within the first 20 min, followed by a much slower increase to the limiting value of 0.94. In-depth analysis suggests that the first stage involves the quick adsorption of dodecanethiol to the corner and edge sites of Au NCs surfaces, leading to remarkable surface Au-Au bond length relaxation (from 2.79 to 2.81 Å) and pronounced gold-to-ligand charge transfer. The second step that corresponds to the much slower adsorption process to the surface facets could be described by the Langmuir kinetics equation with an adsorption rate constant of 0.0132 min(-1) and an initial coverage of 0.41, in good agreement with the initially preferable adsorption of thiols to the most favorable sites. PMID:24122096

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

2013-12-01

252

Thiol passivation of MWIR type II superlattice photodetectors  

Science.gov (United States)

Poor passivation on photodetectors can result in catastrophic failure of the device. Abrupt termination of mesa side walls during pixel definition generates dangling bonds that lead to inversion layers and surface traps leading to surface leakage currents that short circuit diode action. Good passivation, therefore, is critical in the fabrication of high performance devices. Silicondioxide has been the main stay of passivation for commercial photodetectors, deposited at high temperatures and high RF powers using plasma deposition techniques. In photodetectors based on III-V compounds, sulphur passivation has been shown to replace oxygen and saturate the dangling bonds. Despite its effectiveness, it degrades over time. More effort is required to create passivation layers which eliminate surface leakage current. In this work, we propose the use of sulphur based octadecanethiol (ODT), CH3(CH2)17SH, as a passivation layer for the InAs/GaSb superlattice photodetectors that acts as a self assembled monolayer (SAM). ODT SAMs consist of a chain of 18 carbon atoms with a sulphur atom at its head. ODT Thiol coating is a simple process that consist of dipping the sample into the solution for a prescribed time. Excellent electrical performance of diodes tested confirm the effectiveness of the sulphur head stabilized by the intermolecular interaction due to van der Walls forces between the long chains of ODT SAM which results in highly stable ultrathin hydrocarbon layers without long term degradation.

Salihoglu, O.; Muti, A.; Aydinli, A.

2013-06-01

253

Thiols in Scenedesmus vacuolatus upon exposure to metals and metalloids.  

Science.gov (United States)

Phytochelatins are intracellular metal ligands produced by algae when exposed to elevated metal concentrations. In freshwater ecosystems, algae are exposed to a wide range of metals and metalloids. The aim of this study was thus to investigate phytochelatin induction in freshwater algae upon metal and metalloid exposure. To that purpose, the unicellular green alga Scenedesmus vacuolatus, was exposed to Cu, Zn, Ni, Pb and Ag, as well as to As(III), As(V), Sb(III) and Sb(V), and examined for its thiol content (gamma-glutamylcysteine, glutathione and phytochelatins). Glutathione content was found to decrease upon the exposure to Zn and to increase upon the exposure to Pb and Ag. Phytochelatins were only induced by Cu (at [Cu2+] = 8x10(-11) M) and Pb (at [Pb2+] = 8x10(-11) to 8x10(-10) M), where [Cu2+] and [Pb2+] are computed free metal ion concentrations. Glutathione content also decreased upon the exposure to Sb(V) whereas an increase was observed as a result as the exposure to As(III) and As(V). The metalloids As(III), As(V) and Sb(III) in the concentration range from 8x10(-6) to 2x10(-4) M (total concentrations of oxyanions) were inducing phytochelatins. Glutathione and phytochelatin content in S. vacuolatus do thus sensitively respond to exposure to a number of metals and metalloids. PMID:17123642

Le Faucheur, Séverine; Schildknecht, Fabian; Behra, Renata; Sigg, Laura

2006-12-30

254

Tip-enhanced Raman spectroscopic imaging of patterned thiol monolayers  

Directory of Open Access Journals (Sweden)

Full Text Available Full spectroscopic imaging by means of tip-enhanced Raman spectroscopy (TERS was used to measure the distribution of two isomeric thiols (2-mercaptopyridine (2-PySH and 4-mercaptopyridine (4-PySH in a self-assembled monolayer (SAM on a gold surface. From a patterned sample created by microcontact printing, an image with full spectral information in every pixel was acquired. The spectroscopic data is in good agreement with the expected molecular distribution on the sample surface due to the microcontact printing process. Using specific marker bands at 1000 cm?1 for 2-PySH and 1100 cm?1 for 4-PySH, both isomers could be localized on the surface and semi-quantitative information was deduced from the band intensities. Even though nanometer size resolution information was not required, the large signal enhancement of TERS was employed here to detect a monolayer coverage of weakly scattering analytes that were not detectable with normal Raman spectroscopy, emphasizing the usefulness of TERS.

Johannes Stadler

2011-08-01

255

Oligomerization of Indole Derivatives with Incorporation of Thiols  

Directory of Open Access Journals (Sweden)

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.

Jarl E.S. Wikberg

2008-08-01

256

Characterization of mitochondrial thioredoxin reductase from C. elegans  

International Nuclear Information System (INIS)

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

257

Fumarate reductase system of filarial parasite Setaria digitata.  

Science.gov (United States)

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

Unnikrishnan, L S; Raj, R K

1992-04-15

258

Homology modeling of Ferredoxin-nitrite reductase from Arabidopsis thaliana  

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Nitrogen is one of the major growth-limiting nutrients for plants: The main source of nitrogen in most of the higher plants is nitrate taken up through roots. Nitrate can be reduced both in the chloroplasts (photosynthetic tissues) and in proplastes (nonphotosynthetic tissues) such as roots. Ferredoxin-nitrite reductase (NiR) catalyses the reduction of nitrite to ammonium in the second step of the nitrate- assimilation pathway. Homology model of Ferredoxin-nitrite reductase has been ...

Kherraz, Karim; Kherraz, Khaled; Kameli, Abdelkrim

2011-01-01

259

Aldose reductase inhibitory activity and antioxidant capacity of pomegranate extracts  

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

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

2012-01-01

260

Rapid, photoinduced electron transfer-modulated, turn-on fluorescent probe for detection and cellular imaging of biologically significant thiols.  

Science.gov (United States)

There is a very limited number of existing probes whose fluorescence is turned on in the presence of the class of biological thiols made up of glutathione, cysteine, and homocysteine. The extant probes for this class of biological thiols commonly have poor aqueous solubility and long analyte response times, and they demand a very high probe/thiol ratio for decreased time of significant reporter signal generation; knowledge regarding their selectivity with respect to other sulfur-based analytes is unclear. Described here is a previously unreported photoinduced electron-transfer-quenched probe (HMBQ-Nap 1) that offers highly selective and rapid in vitro detection of this class of biologically important thiols at low concentrations and low probe/thiol ratio, and importantly, very rapid imaging of these biological thiols in human cells. PMID:25343216

Nawimanage, Rasika R; Prasai, Bijeta; Hettiarachchi, Suraj U; McCarley, Robin L

2014-12-16

 
 
 
 
261

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

Directory of Open Access Journals (Sweden)

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.

Patil Vijaya

2011-03-01

262

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

Science.gov (United States)

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

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

2014-03-01

263

Carbon-carbon double-bond reductases in nature.  

Science.gov (United States)

Reduction of C = C bonds by reductases, found in a variety of microorganisms (e.g. yeasts, bacteria, and lower fungi), animals, and plants has applications in the production of metabolites that include pharmacologically active drugs and other chemicals. Therefore, the reductase enzymes that mediate this transformation have become important therapeutic targets and biotechnological tools. These reductases are broad-spectrum, in that, they can act on isolation/conjugation C = C-bond compounds, ?,?-unsaturated carbonyl compounds, carboxylic acids, acid derivatives, and nitro compounds. In addition, several mutations in the reductase gene have been identified, some associated with diseases. Several of these reductases have been cloned and/or purified, and studies to further characterize them and determine their structure in order to identify potential industrial biocatalysts are still in progress. In this study, crucial reductases for bioreduction of C = C bonds have been reviewed with emphasis on their principal substrates and effective inhibitors, their distribution, genetic polymorphisms, and implications in human disease and treatment. PMID:24750117

Huang, Minmin; Hu, Haihong; Ma, Li; Zhou, Quan; Yu, Lushan; Zeng, Su

2014-08-01

264

Relative adrenal insufficiency in mice deficient in 5?-reductase 1.  

Science.gov (United States)

Patients with critical illness or hepatic failure exhibit impaired cortisol responses to ACTH, a phenomenon known as 'relative adrenal insufficiency'. A putative mechanism is that elevated bile acids inhibit inactivation of cortisol in liver by 5?-reductases type 1 and type 2 and 5?-reductase, resulting in compensatory downregulation of the hypothalamic-pituitary-adrenal axis and adrenocortical atrophy. To test the hypothesis that impaired glucocorticoid clearance can cause relative adrenal insufficiency, we investigated the consequences of 5?-reductase type 1 deficiency in mice. In adrenalectomised male mice with targeted disruption of 5?-reductase type 1, clearance of corticosterone was lower after acute or chronic (eightfold, P<0.05) administration, compared with WT control mice. In intact 5?-reductase-deficient male mice, although resting plasma corticosterone levels were maintained, corticosterone responses were impaired after ACTH administration (26% lower, P<0.05), handling stress (2.5-fold lower, P<0.05) and restraint stress (43% lower, P<0.05) compared with WT mice. mRNA levels of Nr3c1 (glucocorticoid receptor), Crh and Avp in pituitary or hypothalamus were altered, consistent with enhanced negative feedback. These findings confirm that impaired peripheral clearance of glucocorticoids can cause 'relative adrenal insufficiency' in mice, an observation with important implications for patients with critical illness or hepatic failure, and for patients receiving 5?-reductase inhibitors for prostatic disease. PMID:24872577

Livingstone, Dawn E W; Di Rollo, Emma M; Yang, Chenjing; Codrington, Lucy E; Mathews, John A; Kara, Madina; Hughes, Katherine A; Kenyon, Christopher J; Walker, Brian R; Andrew, Ruth

2014-08-01

265

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

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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 cal...

Demir, Firuz; Kirczenow, George

2012-01-01

266

Crosslinking and degradation of step-growth hydrogels formed by thiol-ene photo-click chemistry  

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Thiol-ene photo-click hydrogels have been used for a variety of tissue engineering and controlled release applications. In this step-growth photopolymerization scheme, multi-arm poly(ethylene glycol) norbornene (PEG4NB) was crosslinked with di-thiol containing crosslinkers to form chemically crosslinked hydrogels. While the mechanism of thiol-ene gelation was well described in the literature, its network ideality and degradation behaviors are not well-characterized. Here, we compared the netw...

Shih, Han; Lin, Chien-chi

2012-01-01

267

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

DEFF Research Database (Denmark)

A long-standing issue in protein film voltammetry (PFV), particularly electrocatalytic voltammetry of redox enzyme monolayers, is the variability of protein adsorption modes, reflected in distributions of catalytic activity of the adsorbed protein/enzyme molecules. Use of well-defined, atomically 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 positively charged and electrostatically neutral, hydrophobic and hydrophilic, aliphatic and aromatic, and variable-length micro-environments, as well as their combinations. Optimal conditions for enzyme function seems to be a combination of hydrophobic and hydrophilic surface linker properties, which can 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 molecules), and 3- and 4-aminothiophenol(hydrophilic, hydrophobic) offer the overall most efficient micro-environments. Subtle differences with even small structural linker differences, however, lead to widely different electrocatalytic properties, strikingly illuminated by the (omega-mercaptoamines. CuNiR thus shows highly efficient, close to ideal reversible electrocatalytic voltammetry on cysteamine-covered Au(111)-electrode surfaces, most likely due to two cysteamine orientations previously disclosed by in situ scanning tunnelling microscopy. Such a dual orientation exposes both a hydrophobic and a positively charged, hydrophilic surface feature. In contrast, the higher cysteamine homologues expose only the hydrophilic component with no electrocatalytic activity on these surfaces. These results offer a basis for rational surface design in forthcoming biological electrocatalysis useful both fundamentally and in novel biosensor technology.

Welinder, Anna C.; Zhang, Jingdong

2007-01-01

268

Structural basis for adenosylcobalamin activation in AdoCbl-dependent ribonucleotide reductases.  

Science.gov (United States)

Class II ribonucleotide reductases (RNR) catalyze the formation of an essential thiyl radical by homolytic cleavage of the Co-C bond in their adenosylcobalamin (AdoCbl) cofactor. Several mechanisms for the dramatic acceleration of Co-C bond cleavage in AdoCbl-dependent enzymes have been advanced, but no consensus yet exists. We present the structure of the class II RNR from Thermotoga maritima in three complexes: (i) with allosteric effector dTTP, substrate GDP, and AdoCbl; (ii) with dTTP and AdoCbl; (iii) with dTTP, GDP, and adenosine. Comparison of these structures gives the deepest structural insights so far into the mechanism of radical generation and transfer for AdoCbl-dependent RNR. AdoCbl binds to the active site pocket, shielding the substrate, transient 5'-deoxyadenosyl radical and nascent thiyl radical from solution. The e-propionamide side chain of AdoCbl forms hydrogen bonds directly to the ?-phosphate group of the substrate. This interaction appears to cause a "locking-in" of the cofactor, and it is the first observation of a direct cofactor-substrate interaction in an AdoCbl-dependent enzyme. The structures support an ordered sequential reaction mechanism with release or relaxation of AdoCbl on each catalytic cycle. A conformational change of the AdoCbl adenosyl ribose is required to allow hydrogen transfer to the catalytic thiol group. Previously proposed mechanisms for radical transfer in B12-dependent enzymes cannot fully explain the transfer in class II RNR, suggesting that it may form a separate class that differs from the well-characterized eliminases and mutases. PMID:20672854

Larsson, Karl-Magnus; Logan, Derek T; Nordlund, Pär

2010-10-15

269

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

Science.gov (United States)

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

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

2014-01-23

270

Electrochemistry behavior of endogenous thiols on fluorine doped tin oxide electrodes  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-10-01

271

Comparative evaluation of antioxidant capacities of thiol-based antioxidants measured by different in vitro methods.  

Science.gov (United States)

Thiol-type compounds are an important class of strong antioxidants and main determinants of total antioxidant capacity (TAC) of cellular homogenates. The TAC of thiol mixtures and the corresponding TEAC (trolox equivalent antioxidant capacity) values of individual thiols were determined by the CUPRAC (CUPric Reducing Antioxidant Capacity) method, and the results were compared with those found by reference assays for method validation. Synthetic mixtures of thiols were prepared, and the expected and found TAC values (in mM trolox (TR) equivalents) of these mixtures showed a good agreement. The technique of standard additions was performed for thiol mixtures and human serum, and the absorbance results confirmed that apparent chemical deviations from Beer's law were absent in the system. The CUPRAC results were compared with those of reference methods, namely 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)/persulphate and Ferric Reducing Antioxidant Power (FRAP). As being a most important thiol (-SH) peptide at in vivo conditions, glutathione (GSH) showed a TEAC value of 0.57 in the CUPRAC method, as opposed to the corresponding value (1.51) in the ABTS/persulphate method. The ABTS/persulphate result was not in accordance with the reversible 1-e oxidation of GSH to the corresponding disulfide that is expected to occur under physiological conditions. FRAP did not give consistent results, and even at relatively high concentrations of GSH, the TEAC(FRAP) value was only 0.07. The thiol-type antioxidant-bearing pharmaceuticals of Brunac eye drop, Trom and Mentopin effervescent tablets containing N-acetyl-L-cysteine (NAC) were assayed with HPLC for comparison, and the obtained results for NAC were in accordance with those found with CUPRAC. PMID:21238764

Güngör, Nilay; Ozyürek, Mustafa; Güçlü, Kubilay; Cekiç, Sema Demirci; Apak, Re?at

2011-02-15

272

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

Energy Technology Data Exchange (ETDEWEB)

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

Snyder, R.D.; Lachmann, P.J. (Merrell Dow Research Institute, Cincinnati, OH (USA))

1989-04-01

273

Electrochemistry behavior of endogenous thiols on fluorine doped tin oxide electrodes  

International Nuclear Information System (INIS)

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

274

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

DEFF Research Database (Denmark)

We demonstrate the use of functional surface groups inherently present on off-stoichiometric thiol?ene polymers, for site-specific immobilization of biomolecules and detection by evanescent wave-induced fluorescence. An optofluidic chip featuring an embedded thiol?ene waveguide was selectively 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 devices, the optical properties of thiol?ene was evaluated by determining the transparency and refractive index of the cured polymer.

Feidenhans'l, Nikolaj Agentoft; Jensen, Thomas Glasdam

2013-01-01

275

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Yamamoto, Yuji; Ritz, Dani; Planson, Anne-gae?lle; Jo?nsson, Thomas J.; Faulkner, Melinda J.; Boyd, Dana; Beckwith, Jon; Poole, Leslie B.

2008-01-01

276

Thiol-yne adsorbates for stable, low-density, self-assembled monolayers on gold.  

Science.gov (United States)

We present a novel approach toward carboxylate-terminated, low-density monolayers on gold, which provides exceptional adsorbate stability and conformational freedom of interfacial functional groups. Adsorbates are synthesized through the thiol-yne addition of two thiol-containing head groups to an alkyne-containing tail group. The resulting monolayers have two distinct phases: a highly crystalline head phase adjacent to the gold substrate, and a reduced density tail phase, which is in contact with the environment. The ellipsometric thickness of 27 Å is consistent with the proposed structure, where a densely packed decanedithiol monolayer is capped with an 11 carbon long, second layer at 50% lateral chain density. The Fourier transform infrared peak at 1710 cm(-1) supports the presence of the carbonyl group. Further, the peaks associated with asymmetric and symmetric methylene stretching are shifted toward higher wavenumbers compared to those of well-packed self-assembled monolayers (SAMs), which shows a lower average crystallinity of the thiol-yne monolayers compared to a typical monolayer. Contact angle measurements indicate an intermediate surface energy for the thiol-yne monolayer surface, owing to the contribution of exposed methylene functionality at the surface in addition to the carbonyl terminal group. The conformational freedom at the surface was demonstrated through remodeling the thiol-yne surface under an applied potential. Changes in the receding contact angle in response to an external potential support the capacity for reorientation of the surface presenting groups. Despite the low packing at the solution interface, thiol-yne monolayers are resistant to water and ion transport (R(f) ~ 10(5)), supporting the presence of a densely structured layer at the gold surface. Further, the electrochemical stability of the thiol-yne adsorbates exceeded that of well-packed SAMs, requiring a more reductive potential to desorb the thiol-yne monolayers from the gold surface. The thiol-yne monolayer approach is not limited to carboxylate functionality and is readily adapted for low-density monolayers of varied functionality. PMID:24512439

Stevens, Christopher A; Safazadeh, Leila; Berron, Brad J

2014-03-01

277

Methylenetetrahydrofolate Reductase Activity and Folate Metabolism  

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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.

Nursen Keser

2014-04-01

278

Ribonucleotide reductase inhibitors and future drug design.  

Science.gov (United States)

Ribonucleotide reductase (RR) is a multisubunit enzyme responsible for the reduction of ribonucleotides to their corresponding deoxyribonucleotides, which are building blocks for DNA replication and repair. The key role of RR in DNA synthesis and cell growth control has made it an important target for anticancer therapy. Increased RR activity has been associated with malignant transformation and tumor cell growth. Efforts for new RR inhibitors have been made in basic and translational research. In recent years, several RR inhibitors, including Triapine, Gemcitabine, and GTI-2040, have entered clinical trial or application. Furthermore, the discovery of p53R2, a p53-inducible form of the small subunit of RR, raises the interest to develop subunit-specific RR inhibitors for cancer treatment. This review compiles recent studies on (1) the structure, function, and regulation of two forms of RR; (2) the role in tumorigenesis of RR and the effect of RR inhibition in cancer treatment; (3) the classification, mechanisms of action, antitumor activity, and clinical trial and application of new RR inhibitors that have been used in clinical cancer chemotherapy or are being evaluated in clinical trials; (4) novel approaches for future RR inhibitor discovery. PMID:16918309

Shao, J; Zhou, B; Chu, Bernard; Yen, Y

2006-08-01

279

Binding of Fidarestat Stereoisomers with Aldose Reductase  

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

Dae-Sil Lee

2006-11-01

280

Aldose reductase, oxidative stress, and diabetic mellitus.  

Science.gov (United States)

Diabetes mellitus (DM) is a complex metabolic disorder arising from lack of insulin production or insulin resistance (Diagnosis and classification of diabetes mellitus, 2007). DM is a leading cause of morbidity and mortality in the developed world, particularly from vascular complications such as atherothrombosis in the coronary vessels. Aldose reductase (AR; ALR2; EC 1.1.1.21), a key enzyme in the polyol pathway, catalyzes nicotinamide adenosine dinucleotide phosphate-dependent reduction of glucose to sorbitol, leading to excessive accumulation of intracellular reactive oxygen species (ROS) in various tissues of DM including the heart, vasculature, neurons, eyes, and kidneys. As an example, hyperglycemia through such polyol pathway induced oxidative stress, may have dual heart actions, on coronary blood vessel (atherothrombosis) and myocardium (heart failure) leading to severe morbidity and mortality (reviewed in Heather and Clarke, 2011). In cells cultured under high glucose conditions, many studies have demonstrated similar AR-dependent increases in ROS production, confirming AR as an important factor for the pathogenesis of many diabetic complications. Moreover, recent studies have shown that AR inhibitors may be able to prevent or delay the onset of cardiovascular complications such as ischemia/reperfusion injury, atherosclerosis, and atherothrombosis. In this review, we will focus on describing pivotal roles of AR in the pathogenesis of cardiovascular diseases as well as other diabetic complications, and the potential use of AR inhibitors as an emerging therapeutic strategy in preventing DM complications. PMID:22582044

Tang, Wai Ho; Martin, Kathleen A; Hwa, John

2012-01-01

 
 
 
 
281

Aldose reductase inhibitory compounds from Xanthium strumarium.  

Science.gov (United States)

As part of our ongoing search for natural sources of therapeutic and preventive agents for diabetic complications, we evaluated the inhibitory effects of components of the fruit of Xanthium strumarium (X. strumarium) on aldose reductase (AR) and galactitol formation in rat lenses with high levels of glucose. To identify the bioactive components of X. strumarium, 7 caffeoylquinic acids and 3 phenolic compounds were isolated and their chemical structures were elucidated on the basis of spectroscopic evidence and comparison with published data. The abilities of 10 X. strumarium-derived components to counteract diabetic complications were investigated by means of inhibitory assays with rat lens AR (rAR) and recombinant human AR (rhAR). From the 10 isolated compounds, methyl-3,5-di-O-caffeoylquinate showed the most potent inhibition, with IC?? values of 0.30 and 0.67 ?M for rAR and rhAR, respectively. In the kinetic analyses using Lineweaver-Burk plots of 1/velocity and 1/substrate, methyl-3,5-di-O-caffeoylquinate showed competitive inhibition of rhAR. Furthermore, methyl-3,5-di-O-caffeoylquinate inhibited galactitol formation in the rat lens and in erythrocytes incubated with a high concentration of glucose, indicating that this compound may be effective in preventing diabetic complications. PMID:23604720

Yoon, Ha Na; Lee, Min Young; Kim, Jin-Kyu; Suh, Hong-Won; Lim, Soon Sung

2013-09-01

282

Aldose reductase, oxidative stress and diabetic mellitus  

Directory of Open Access Journals (Sweden)

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

JohnHwa

2012-05-01

283

Increased 5?-reductase activity in idiopathic hirsutism  

International Nuclear Information System (INIS)

In vitro, genital skin 5?-reductase activity (5?-RA) was measured in ten hirsute women with normal androgen levels (idiopathic hirsutism (IH)) and in ten hirsute women with elevated androgen levels (polycystic ovary syndrome (PCO)) in order to determine the influence of secreted androgens on 5?-RA. In vitro 5?-RA was assessed by incubations of skin with 14C-testosterone (T) for 2 hours, after which steroids were separated and the radioactivity of dihydrotestosterone (DHT) and 5?-androstane 3?-17?-estradiol (3?-diol) in specific eluates were determined. All androgens were normal in IH with the exception of higher levels of 3?-diol glucuronide which were similar to the levels of PCO. The conversion ratio (CR) of T to DHT in IH and PCO were similar, yet significantly greater than the CR of control subjects. The CR of T to 3?-diol in IH and PCO were similar, yet higher than in control subjects. Serum androgens showed no correlation with 5?-RA, while the CR of T to DHT showed a significant positive correlation with the Ferriman and Gallwey score. The increased 5?-RA in IH appears to be independent of serum androgen levels and is, therefore, an inherent abnormality. The term idiopathic is a misnomer, because hirsutism in these patients may be explained on the basis of increased skin 5?-RA

284

Fuel instability model studies: The liquid-phase cooxidation of thiols and indene by oxygen  

Energy Technology Data Exchange (ETDEWEB)

Instability problems in middle distillate fuels have been correlated with the presence of both active olefin species and heteroatomic compounds such as thiols. It has been demonstrated that the type of sulfur compound rather than the total sulfur concentration is the key to fuel instability reactions. Research has shown that low concentrations of thiols will act as radical traps to inhibit autoxidation. When added to a fuel, thiols accelerated the rate of oxygen reaction without a commensurate increase in peroxidation. Evidence for the oxidative addition of thiols to olefins has been found to occur by studying the addition of thiophenol to indene in a model fuel during stressing in both a model system at temperatures in the 100-120C range and in the JFTOT apparatus at temperatures up to 320C. Similarities and differences were found in the two systems, with the product distribution being temperature dependent. This could account, in part, for the differences in thiol influences on autoxidation observed in model systems and in fuels.

Morris, R.E.; Mushrush, G.W. (Naval Research Lab., Washington, DC (United States))

285

Thiol-disulfide exchange in peptides derived from human growth hormone.  

Science.gov (United States)

Disulfide bonds stabilize proteins by cross-linking distant regions into a compact three-dimensional structure. They can also participate in hydrolytic and oxidative pathways to form nonnative disulfide bonds and other reactive species. Such covalent modifications can contribute to protein aggregation. Here, we present experimental data for the mechanism of thiol-disulfide exchange in tryptic peptides derived from human growth hormone in aqueous solution. Reaction kinetics was monitored to investigate the effect of pH (6.0-10.0), temperature (4-50°C), oxidation suppressants [ethylenediaminetetraacetic acid (EDTA) and N2 sparging], and peptide secondary structure (amide cyclized vs. open form). The concentrations of free thiol containing peptides, scrambled disulfides, and native disulfide-linked peptides generated via thiol-disulfide exchange and oxidation reactions were determined using reverse-phase HPLC and liquid chromatography-mass spectrometry. Concentration versus time data were fitted to a mathematical model using nonlinear least squares regression analysis. At all pH values, the model was able to fit the data with R(2) ? 0.95. Excluding oxidation suppressants (EDTA and N2 sparging) resulted in an increase in the formation of scrambled disulfides via oxidative pathways but did not influence the intrinsic rate of thiol-disulfide exchange. In addition, peptide secondary structure was found to influence the rate of thiol-disulfide exchange. PMID:24549831

Chandrasekhar, Saradha; Epling, Daniel E; Sophocleous, Andreas M; Topp, Elizabeth M

2014-04-01

286

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

Science.gov (United States)

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

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

2008-08-13

287

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-05-26

288

Total Thiols and MDA Levels in Patients with Acute Myocardial Infarction Before and After Reperfusion Therapy  

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Full Text Available Background: Reactive oxygen species have been implicated in the pathogenesis of ischemic and reperfusion injury. In the current work we have measured malondialdehyde (MDA, total thiols, total CK, CK-MB and AST in ECG proven acute myocardial infarction (AMI patients immediately after admission and 24 hours after administration of thrombolytic agent streptokinase, and in healthy controls. Methods: Blood samples from 44 AMI patients and 25 age and sex matched healthy controls were obtained and analyzed for MDA, total thiols using spectrophotometric methods and cardiac enzymes CK, CK-MB and AST using automated analyzer. Results: We have found significant increase in MDA, CPK, CK-MB, AST (p< 0.001 and significant decrease in total thiols (p<0.001 in AMI patients after thrombolytic therapy compared to values at admission, and healthy controls. MDA correlated negatively with total thiols (r = - 0.333, p<0.05 and positively with CK-MB (r = 0.491, p<0.01 in AMI patients after thrombolytic therapy. Conclusions: Reperfusion following thrombolytic therapy increases reactive oxygen species with concomitant decrease in antioxidant total thiols

Suresh Babu

2010-10-01

289

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

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

Hemendra J. Vekaria

2010-11-01

290

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

International Nuclear Information System (INIS)

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

291

A microchip electrophoresis strategy with online labeling and chemiluminescence detection for simultaneous quantification of thiol drugs.  

Science.gov (United States)

An integrated microfluidic device with online labeling and chemiluminescence (CL) detection was developed for the simultaneous quantification of thiol drugs. In this device, the online labeling, electrophoresis separation and CL detection were compactly integrated onto a glass/poly(dimethylsiloxane) (PDMS) hybrid microfluidic chip. CL detection was based on the oxidation reaction of N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and o-phthalaldehyde (OPA) labeled thiol drugs with NaBrO. Four thiol drugs including 2-mercaptopropionylglycine (2-MPG), captopril (CP), 6-thioguanine (6-TG) and 6-mercaptopurine (6-MP) were employed as model compounds to examine the utility of the system. It was indicated that the separation and detection of four drugs can be completed within 90s. Detection limits (S/N=3) for the thiol drugs tested were in the range of 8.9×10(-9)-13.5×10(-9)M. The application of the present system was demonstrated by analyzing the thiol drugs in human plasma samples. PMID:21458189

Huang, Yong; Zhao, Shulin; Shi, Ming; Liang, Hong

2011-07-15

292

Modular Thiol-Ene Chemistry Approach towards Mesoporous Silica Monoliths with Organically Modified Pore Walls.  

Science.gov (United States)

The surface modification of mesoporous silica monoliths through thiol-ene chemistry is reported. First, mesoporous silica monoliths with vinyl, allyl, and thiol groups were synthesized through a sol-gel hydrolysis-polycondensation reaction from tetramethyl orthosilicate (TMOS) and vinyltriethoxysilane, allyltriethoxysilane, and (3-mercaptopropyl)trimethoxysilane, respectively. By variation of the molar ratio of the comonomers TMOS and functional silane, mesoporous silica objects containing different amounts of vinyl, allyl, and thiol groups were obtained. These intermediates can subsequently be derivatized through radical photoaddition reactions either with a thiol or an olefin, depending on the initial pore wall functionality, to yield silica monoliths with different pore-wall chemistries. Nitrogen sorption, small-angle X-ray scattering, solid-state NMR spectroscopy, elemental analysis, thermogravimetric analysis, and redox titration demonstrate that the synthetic pathway influences the morphology and pore characteristics of the resulting monoliths and also plays a significant role in the efficiency of functionalization. Moreover, the different reactivity of the vinyl and allyl groups on the pore wall affects the addition reaction, and hence, the degree of the pore-wall functionalization. This report demonstrates that thiol-ene photoaddition reactions are a versatile platform for the generation of a large variety of organically modified silica monoliths with different pore surfaces. PMID:25335454

Göbel, Ronald; Hesemann, Peter; Friedrich, Alwin; Rothe, Regina; Schlaad, Helmut; Taubert, Andreas

2014-12-22

293

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

Scientific Electronic Library Online (English)

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

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

2009-04-01

294

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-11-27

295

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

International Nuclear Information System (INIS)

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

296

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

Scientific Electronic Library Online (English)

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

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

1495-14-01

297

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

Science.gov (United States)

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.

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

2014-05-01

298

Fabrication of nano-pillar with sub-100nm resolution based on thiol-ene  

Science.gov (United States)

This paper demonstrates an approach to fabricate nano-pillar based on thiol-ene via soft-lithography. The template is anodic aluminum oxygen (AAO) with ordered nano-holes with the diameter of 90nm.The nano-pillar consists of rigid thiol-ene features on an elastic poly(dimethylsiloxane) (PDMS) support. It is capable of patterning both flat and curved substrate. The thiol-ene is a new green UV-curable polymer material, including a number of advantages such as rapid UV-curing in the natural environment, low-cost, high resolution, and regulative performance characteristic. Here, we fabricated a two-layer structure, which included rigid thiol-ene nano-pillar with sub-100nm resolution and soft PDMS substrate. The experiment results show that this approach can be used to fabricate high-resolution features and the thiol-ene is an excellent imprint material. The fabrication technique in this paper is simple, low-cost, high-resolution and easy to high throughput, which has broad application prospects in the preparation of nanostructures.

Zhang, Man; Deng, Qiling; Shi, Lifang; Pang, Hui; Cao, Axiu; Hu, Song

2014-11-01

299

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

Energy Technology Data Exchange (ETDEWEB)

The mechanism by which the ferredoxin-thioredoxin system activates the target enzyme, NADP-malate dehydrogenase, was investigated by analyzing the sulfhydryl status of individual protein components with (/sup 14/C)iodoacetate and monobromobimane. The data indicate that ferredoxin-thioredoxin reductase (FTR)--an iron-sulfur enzyme present in oxygenic photosynthetic organisms--is the first member of a thiol chain that links light to enzyme regulation. FTR possesses a catalytically active dithiol group localized on the 13 kDa (similar) subunit, that occurs in all species investigated and accepts reducing equivalents from photoreduced ferredoxin and transfers them stoichiometrically to the disulfide form of thioredoxin m. The reduced thioredoxin m, in turn, reduces NADP-malate dehydrogenase, thereby converting it from an inactive (S-S) to an active (SH) form. The means by which FTR is able to combine electrons (from photoreduced ferredoxin) with protons (from the medium) to reduce its active disulfide group remains to be determined.

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

1987-07-01

300

Reduction of benzoquinones to hydroquinones via spontaneous reaction with glutathione and enzymatic reaction by S-glutathionyl-hydroquinone reductases.  

Science.gov (United States)

S-Glutathionyl-hydroquinone reductases (GS-HQRs) are a new class of glutathione transferases, widely present in bacteria, halobacteria, fungi, and plants. They catalyze glutathione (GSH)-dependent reduction of GS-trichloro-p-hydroquinone to trichloro-p-hydroquinone. Since GS-trichloro-p-hydroquinone is uncommon in nature, the extensive presence of GS-HQRs suggests they use common GS-hydroquinones. Here we demonstrate that several benzoquinones spontaneously reacted with GSH to form GS-hydroquinones via Michael addition, and four GS-HQRs from yeast and bacteria reduced the GS-hydroquinones to the corresponding hydroquinones. The spontaneous and enzymatic reactions led to the reduction of benzoquinones to hydroquinones with the concomitant oxidation of GSH to oxidized glutathione (GS-SG). The enzymes did not use GS-benzoquinones or other thiol-hydroquinones, for example, S-cysteinyl-hydroquinone, as substrates. Apparent kinetic parameters showed the enzymes preferred hydrophobic, bulky substrates, such as GS-menadiol. The broad substrate range and their wide distribution suggest two potential physiological roles: channeling GS-hydroquinones back to hydroquinones and reducing benzoquinones via spontaneous formation of GS-hydroquinones and then enzymatic reduction to hydroquinones. The functions are likely important in metabolic pathways with quinone intermediates. PMID:22686328

Lam, L K Metthew; Zhang, Zhicheng; Board, Philip G; Xun, Luying

2012-06-26

 
 
 
 
301

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-10-10

302

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

International Nuclear Information System (INIS)

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 ?M). Levels of cadmium, cysteine, glutathione (GSH), ?-glutamylcysteine (?-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 ?-EC. This is the first report of induction of thiol peptides, presumably phytochelatins, by a trace metal in a sea grass species

303

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

304

Competitive reduction of perferrylmyoglobin radicals by protein thiols and plant phenols  

DEFF Research Database (Denmark)

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

Jongberg, Sisse; Lametsch, Marianne Lund

2014-01-01

305

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

International Nuclear Information System (INIS)

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

306

Influence of volatile thiols in the development of blackcurrant aroma in red wine.  

Science.gov (United States)

A strong blackcurrant aroma was recently perceived in some red wines originating from the same appellation. Varietal thiols such as 4-mercapto-4-methyl-2-pentanone (4MMP), 3-(mercapto)hexyl acetate (3MHA) and 3-mercapto-1-hexanol (3MH) are compounds potentially responsible for the development of this aroma. In order to demonstrate the correlation between thiols concentrations in red wines and blackcurrant aroma intensity, a multiple variable analysis was realised with thiols concentrations obtained by chemical analysis and blackcurrant aroma intensities obtained by descriptive sensory analysis. The 4MMP concentration was very well correlated to the blackcurrant aroma, and 3MHA and 3MH present at high concentrations act as enhancers of the perception of this aroma. This correlation was further supported after performing a sensory comparison by classification test. The different factors that could impact on the development of blackcurrant aroma in red wine were discussed. PMID:24001837

Rigou, Peggy; Triay, Aurélie; Razungles, Alain

2014-01-01

307

Study of radiation induced oxidation of thiol compounds in aqueous solutions  

International Nuclear Information System (INIS)

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

308

Thiolated pyrimidine nucleotides may interfere thiol groups concentrated at lipid rafts of HIV-1 infected cells.  

Science.gov (United States)

Upon HIV infection, cells become activated and cell surface thiols are present in increased number. Earlier we demonstrated in vitro anti-HIV effect of thiolated pyrimidine nucleotide UD29, which interferes thiol function. To further analyse the redox processes required for HIV-1 entry and infection, toxicity assays were performed using HIV-1 infected monolayer HeLaCD4-LTR/ ?-gal cells and suspension H9 T cells treated with several thiolated nucleotide derivatives of UD29. Selective cytotoxicity of thiolated pyrimidines on HIV-1 infected cells were observed. Results indicate that thiolated pyrimidine derivates may interfere with -SH (thiol) groups concentrated in lipid rafts of cell membrane and interacts HIV-1 infected (activated) cells resulting in a selective cytotoxicity of HIV-1 infected cells, and reducing HIV-1 entry. PMID:25496973

Kanizsai, Szilvia; Ongrádi, Joseph; Aradi, János; Nagy, Károly

2014-12-01

309

Thiyl- and thiyl-peroxyl radicals produced from the irradiation of antioxidant thiol compounds  

International Nuclear Information System (INIS)

The transients involved in the mechanism of protection by thiol compounds against oxidative damage have been characterized by pulse radiolysis technique. The oxidizing properties of both thiyl (RS.) and thiyl-peroxyl radical (RSOO.), with E lying in the range +0.9 to +1.0 V, are well emphasized from the rates for their interactions with nucleophilic agents, including naturally occurring antioxidants. By applying a plausible kinetic treatment to the decay pattern of RSOO., the rates for both the interaction of the radical with the parent thiol and the structural rearrangement to sulphonyl radical (RSO2.) were measured to be 1.4 x 106 mol-1dm3s-1 and 1.4 x 103s-1, respectively. The roles of thiol-derived radicals in oxidative damage in biological systems are discussed. (author)

310

The role of biliverdin reductase in colorectal cancer  

International Nuclear Information System (INIS)

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

311

Stretching of BDT-gold molecular junctions: thiol or thiolate termination?  

Science.gov (United States)

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.

Souza, Amaury De Melo; Rungger, Ivan; Pontes, Renato Borges; Rocha, Alexandre Reily; da Silva, Antônio José Roque; Schwingenschlöegl, Udo; Sanvito, Stefano

2014-11-01

312

Promoting thiol expression increases the durability of antitumor T-cell functions.  

Science.gov (United States)

Ex vivo-expanded CD8(+) T cells used for adoptive immunotherapy generally acquire an effector memory-like phenotype (TEM cells). With regard to therapeutic applications, two undesired features of this phenotype in vivo are limited persistence and reduced antitumor efficacy, relative to CD8(+) T cells with a central memory-like phenotype (TCM cells). Furthermore, there is incomplete knowledge about all the differences between TEM and TCM cells that may influence tumor treatment outcomes. Given that TCM cells survive relatively longer in oxidative tumor microenvironments, we investigated the hypothesis that TCM cells possess relatively greater antioxidative capacity than TEM cells. Here, we report that TCM cells exhibit a relative increase compared with TEM cells in the expression of cell surface thiols, a key target of cellular redox controls, along with other antioxidant molecules. Increased expression of redox regulators in TCM cells inversely correlated with the generation of reactive oxygen and nitrogen species, proliferative capacity, and glycolytic enzyme levels. Notably, T-cell receptor-transduced T cells pretreated with thiol donors, such as N-acetyl cysteine or rapamycin, upregulated thiol levels and antioxidant genes. A comparison of antitumor CD8(+) T-cell populations on the basis of surface thiol expression showed that thiol-high cells persisted longer in vivo and exerted superior tumor control. Our results suggest that higher levels of reduced cell surface thiols are a key characteristic of T cells that can control tumor growth and that profiling this biomarker may have benefits to adoptive T-cell immunotherapy protocols. PMID:25164014

Kesarwani, Pravin; Al-Khami, Amir A; Scurti, Gina; Thyagarajan, Krishnamurthy; Kaur, Navtej; Husain, Shahid; Fang, Quan; Naga, Osama S; Simms, Patricia; Beeson, Gyda; Voelkel-Johnson, Christina; Garrett-Mayer, Elizabeth; Beeson, Craig C; Nishimura, Michael I; Mehrotra, Shikhar

2014-11-01

313

Metabolic coupling of two small-molecule thiols programs the biosynthesis of lincomycin A.  

Science.gov (United States)

Low-molecular-mass thiols in organisms are well known for their redox-relevant role in protection against various endogenous and exogenous stresses. In eukaryotes and Gram-negative bacteria, the primary thiol is glutathione (GSH), a cysteinyl-containing tripeptide. In contrast, mycothiol (MSH), a cysteinyl pseudo-disaccharide, is dominant in Gram-positive actinobacteria, including antibiotic-producing actinomycetes and pathogenic mycobacteria. MSH is equivalent to GSH, either as a cofactor or as a substrate, in numerous biochemical processes, most of which have not been characterized, largely due to the dearth of information concerning MSH-dependent proteins. Actinomycetes are able to produce another thiol, ergothioneine (EGT), a histidine betaine derivative that is widely assimilated by plants and animals for variable physiological activities. The involvement of EGT in enzymatic reactions, however, lacks any precedent. Here we report that the unprecedented coupling of two bacterial thiols, MSH and EGT, has a constructive role in the biosynthesis of lincomycin A, a sulfur-containing lincosamide (C8 sugar) antibiotic that has been widely used for half a century to treat Gram-positive bacterial infections. EGT acts as a carrier to template the molecular assembly, and MSH is the sulfur donor for lincomycin maturation after thiol exchange. These thiols function through two unusual S-glycosylations that program lincosamide transfer, activation and modification, providing the first paradigm for EGT-associated biochemical processes and for the poorly understood MSH-dependent biotransformations, a newly described model that is potentially common in the incorporation of sulfur, an element essential for life and ubiquitous in living systems. PMID:25607359

Zhao, Qunfei; Wang, Min; Xu, Dongxiao; Zhang, Qinglin; Liu, Wen

2015-02-01

314

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2013-01-01

315

Volume holographic recording in photopolymerizable nanocomposite materials based on radical-mediated thiol-yne step-growth polymerizations  

Science.gov (United States)

We propose the use of radical-mediated thiol-yne step-growth photopolymerizations for volume holographic recording in NPC films to overcome the drawback of low crosslinking densities but retain the advantage of low shrinkage in the thiol-ene photopolymerizations. The thiol-yne photopolymerization mechanism is different from the thiol-ene photopolymeriztions in the sense that each alkyne functional group can react consecutively with two thiol functional groups. We show that thiol-yne based NPC films dispersed with silica nanoparticles give the saturated refractive index change as large as 0.008 and the material recording sensitivity as high as 2005 cm/J at a wavelength of 532 nm, larger than the minimum acceptable values of 0.005 and 500 cm/J, respectively, for holographic data storage. We also show that the shrinkage of a recorded hologram can be as low as that of thiol-ene based NPC films and that the thermal stability is improved better. In addition, we demonstrate digital data page recording in thiol-yne based NPC films, showing a low symbol error rate and a high signal-to-noise ratio to be 2.8×10-4 and 8, respectively.

Mitsube, Ken; Nishimura, Yuki; Takayama, Shingo; Nagaya, Kohta; Tomita, Yasuo

2013-05-01

316

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

Science.gov (United States)

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

Elduque, Xavier; Pedroso, Enrique; Grandas, Anna

2014-04-01

317

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

Science.gov (United States)

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

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

2014-05-01

318

Thiol-Disulfide Interchange in the Tocinoic Acid/Glutathione System During Freezing and Drying  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thiol-disulfide interchange (“disulfide scrambling”) is a common mechanism of covalent aggregation for protein drugs. Using tocinoic acid (cyclo-S-Cys-Tyr-Ile-Gln-Asn-Cys-(S); TA(ox)) and glutathione (?Glu-Cys-Gly; GSH), our previous work demonstrated that thiol/disulfide interchange is affected by lyophilization in a manner consistent with irreversible and regioselective loss of TA(ox) (Zhang et al., 2009, J Pharm Sci 98/9: 3312–3318). Here, we explore the contributions of stages of t...

Thing, Mette; Zhang, Jun; Laurence, Jennifer; Topp, Elizabeth M.

2010-01-01

319

Synthesis and characterization of a Gd(III) based contrast agent responsive to thiol containing compounds  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A novel Gd(III) complex with a modified DO3A-like chelating cage has been synthesized and characterized as a candidate contrast agent responsive to the concentration of free thiols in tissues ( essentially represented by reduced glutathione, GSH). The novel compound ( called Gd-DO3AS-Act) bears a flexible linker ending with a 2-pyridyl-dithio group, that can promptly react with free thiols ( XSH) to form mixed disulfides of the form Gd-DO3AS-SX. Compound Gd-DO3AS-Act is characterized by a mil...

Aime, Silvio; Consol, Simona; Longo, Dario Livio; Burgio, Daniela Francesca

2007-01-01

320

NMR study of 2-amino-cyclo-hexane thiols N-substituted  

International Nuclear Information System (INIS)

Considering that thiols and mainly ?-aminoacids are been successful in research aiming the discovering of new substances with protective actions against the radiation effects on living being, 2-amine-cyclo-hexane thiols N-alkyl-substituted were synthesized and submitted to to biological tests. The reactions were planned to favor the SN 2 mechanism, in order to obtain the respective trans isomers from each ?-aminothiol (nonpolar medium; solvent: benzene or hexane). This work presents the results obtained in the NMR study of four by products of this class

 
 
 
 
321

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Zagal, Jose? H.; Henriquez, Jaime J. H.

2000-01-01

322

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

International Nuclear Information System (INIS)

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

323

Microwave assisted oxidative coupling of thiols to symmetrical disulfides with tripropylammonium fluorochromate(VI (TPAFC  

Directory of Open Access Journals (Sweden)

Full Text Available Tripropylammonium fluorochromate(VI (TPAFC is an efficient and novel reagent, which can be prepared easily and oxidizes thiols to the corresponding disulfides, quickly. The reactions are performed cleanly and are controlled to stop at the disulfide stage, without over-oxidation or side products. Coupling of thiols to their corresponding disulfides, was studied in solution at room temperature and under conditions using a minimal amount of solvent under microwave irradiation. The easy procedure, simple work-up, short reaction times, and excellent yields are other advantages of this reagent.DOI: http://dx.doi.org/10.4314/bcse.v26i1.16

Shahriare Ghammamy

2012-12-01

324

Thiol-catalyzed formation of lactate and glycerate from glyceraldehyde. [significance in molecular evolution  

Science.gov (United States)

The rate of lactate formation from glyceraldehyde, catalyzed by N-acetyl-cysteine at ambient temperature in aqueous sodium phosphate (pH 7.0), is more rapid at higher sodium phosphate concentrations and remains essentially the same in the presence and absence of oxygen. The dramatic increase in the rate of glycerate formation that is brought about by this thiol, N-acetylcysteine, is accompanied by commensurate decreases in the rates of glycolate and formate production. It is suggested that the thiol-dependent formation of lactate and glycerate occurs by way of their respective thioesters. Attention is given to the significance of these reactions in the context of molecular evolution.

Weber, A. L.

1983-01-01

325

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

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

Amy, N. K.; Garrett, R. H.

1980-01-01

326

The inhibitory activity of aldose reductase in vitro by constituents of Garcinia mangostana Linn.  

Science.gov (United States)

We investigated aldose reductase inhibition of Garcinia mangostana Linn. from Indonesia. Dichloromethane extract of the root bark of this tree was found to demonstrate an IC50 value of 11.98 µg/ml for human aldose reductase in vitro. From the dichloromethane fraction, prenylated xanthones were isolated as potent human aldose reductase inhibitors. We discovered 3-isomangostin to be most potent against aldose reductase, with an IC50 of 3.48 µM. PMID:25636870

Fatmawati, Sri; Ersam, Taslim; Shimizu, Kuniyoshi

2015-01-15

327

Glutathione reductase activity with an oxidized methylated glutathione analog.  

Science.gov (United States)

The activity of glutathione reductase with an unnatural analog of oxidized glutathione was explored. The analog, L-?-glutamyl-2-methyl-L-cysteinyl-glycine disulfide, places an additional methyl group on the alpha position of each of the central cysteine residues, which significantly increases steric bulk near the disulfide bond. Glutathione reductase was completely unable to catalyze the sulfur-sulfur bond reduction of the analog. Additionally, enzyme kinetics experiments indicated that the analog acts as a competitive inhibitor of glutathione reductase. Computational studies confirm that the methylated analog fits within the active site of the enzyme but its disulphide bond geometry is altered, preventing reduction by the enzyme. The substitution of (R)-2-methylcysteine in place of natural (R)-cysteine in peptides constitutes a new strategy for stabilizing disulphide bonds from enzyme-catalyzed degradation. PMID:23808802

Kedrowski, Brant L; Gutow, Jonathan H; Stock, Gorman; Smith, Maureen; Jordan, Chondrea; Masterson, Douglas S

2014-08-01

328

B Cells Induce Tolerance by Presenting Endogenous Peptide-IgG on MHC Class II Molecules via an IFN-?-Inducible Lysosomal Thiol Reductase-Dependent Pathway1  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have previously demonstrated that splenic B cells, transduced with peptide-IgG fusion proteins, are efficient tolerogenic APCs in vivo. Specific hyporesponsiveness to epitopes encoded in the peptide-IgG fusion protein has been achieved to over one dozen Ags, and clinical efficacy has been established in animal models for several autoimmune diseases and hemophilia. Previous studies also demonstrated that tolerance in this system requires MHC class II expression by the transduced B cells. Ye...

Su, Yan; Carey, Gregory; Maric?, Maja; Scott, David W.

2008-01-01

329

Multiple turnovers of DNAzyme for amplified detection of ATP and reduced thiol in cell homogenates.  

Science.gov (United States)

A conveniently amplified DNAzyme-based fluorescence strategy was designed for highly sensitive detection of ATP or reduced thiol based on the introduction of an ATP aptamer or a disulfide bond in the bioconjugates of magnetic nanoparticles (MNP) and polystyrene microsphere-DNAzyme complexes (PSM-DNAzyme). PMID:25429374

Guo, Yingshu; Liu, Jia; Yang, Guangxu; Sun, Xiaofeng; Chen, Hong-Yuan; Xu, Jing-Juan

2015-01-18

330

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

Science.gov (United States)

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

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

2006-09-20

331

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

Science.gov (United States)

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

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

2014-11-01

332

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

International Nuclear Information System (INIS)

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

333

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

Energy Technology Data Exchange (ETDEWEB)

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

Wu, Kunlin; Bai, Meilin; Hou, Shimin, E-mail: smhou@pku.edu.cn [Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871 (China); Sanvito, Stefano [School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2 (Ireland)

2013-11-21

334

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

Science.gov (United States)

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

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

2013-08-01

335

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

International Nuclear Information System (INIS)

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

336

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

Directory of Open Access Journals (Sweden)

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

Mark R. Geier

2013-08-01

337

Do alkane thiols form stable monolayer films on the surfaces of high temperature superconductors (HTSCs)?  

Energy Technology Data Exchange (ETDEWEB)

Recently there has been significant interest in the chemical modification of HTSC surfaces with molecule-based reagents. We will describe a preliminary survey of the surface coordination chemistry of YBa{sub 2}Cu{sub 3}O{sub 7-{gamma}} and other HTSC materials. In this survey, we have used a series of redox-active ligands containing alkyl amine, aryl amine, thiol, phosphine, amide, and alcohol functionalities. Evidence supporting the strong adsorption of molecules with alkyl amine, aryl amine and thiol functionalities will be reported. Resistivity measurements for the HTSCs and modified HTSCs show that chemical modification does not significantly lower T{sub c} for the superconductor. This work presents the first example of the direct chemical modification of the surface of a high-T{sub c} superconductor with a monolayer of a molecular reagent. A surprising result is that alkyl thiols do form stable, robust monolayers on a variety of HTSCs. Others have reported that under similar conditions alkyl thiols do not stably chemisorb onto HTSCs. However, alkyl amines are the superior reagent for the chemical modification of the Cu-rich HTSCs.

Xu, F.; Chen, K.; Mirkin, C.A. [Northwestern Univ., Evanston, IL (United States)] [and others

1995-12-31

338

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

International Nuclear Information System (INIS)

The most commonly used collectors for sulfide minerals in the mining industry are the thiol collectors for the recovery of these minerals from their associated gangues by froth flotation. For this reason, a great deal of attention has been paid to understand the attachment mechanism of thiol collectors to metal sulfide surfaces. The density functional theory (DFT) calculations at the B3LYP/3-21G* and B3LYP/6-31++G** levels were employed to propose the flotation responses of these thiol collectors, namely, diethyl dithiocarbamate, ethyl dithiocarbamate, ethyl dithiocarbonate, ethyl trithiocarbonate and ethyl dithiophosphate ions, and to study the interaction energies of these collectors with Ag (+1) ion in connection to acanthite (Ag2S) mineral. The calculated interaction energies, ?E, were interpreted in terms of the highest occupied molecular orbital (HOMO) energies of the isolated collector ions. The results show that the HOMOs are strongly localized to the sulfur atoms and the HOMO energies can be used as a reactivity descriptor for the flotation ability of the thiol collectors. Using the HOMO and ?E energies, the reactivity order of the collectors is found to be (C2H5)2NCS2- > C2H5NHCS2- > C2H5OCS2- > C2H5SCS2- > (C2H5O)(OH)PS2-5O)(OH)PS2-. The theoretically obtained results are in good agreement with the experimental data reported

339

Comparison of diazonium salt derived and thiol derived nitrobenzene layers on gold.  

Science.gov (United States)

The reduction of diazonium salts to produce aryl films on surfaces has expanded in application from carbon electrodes to a variety of conducting materials. The increasing interest in this method for modifying gold surfaces has motivated us to directly compare the structure and stability of nitrobenzene films derived from diazonium salts with monolayers formed from the corresponding thiol. We employ spectroscopic and microscopic techniques to characterize the structure and thickness of the as-formed layers. As a means of assessing stability, the nitrobenzene films were subjected to rigorous sonication, refluxing solvents, and chemical displacement by octadecanethiol. Infrared reflection-absorption spectroscopy and electrochemical blocking were used to assess the stabilities of the films generated by the two methods. Sonication and refluxing both remove more material from the diazonium-derived film relative to the thiol monolayer. However, a significant amount of each layer remains bonded to the surface following these treatments. Immersion in octadecanethiol solution results in complete displacement of the thiol derived nitrobenzene monolayer. Importantly, a significant fraction of the diazonium derived films cannot be displaced by octadecanethiol. These findings show that under certain conditions aryl films formed from the reduction of diazonium salts are more strongly bonded to gold surfaces compared to the thiol analogue. PMID:19260685

Shewchuk, Dwayne M; McDermott, Mark T

2009-04-21

340

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

International Nuclear Information System (INIS)

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

 
 
 
 
341

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

International Nuclear Information System (INIS)

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

342

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

Science.gov (United States)

Reaction of (R,S)-?-terpineol with thioacetic acid in food-grade n-hexane resulted into two ?-terpineol thioacetate derivatives with the same molecular weight. After 5?h of reaction time, (R,S)-?-terpineol was completely transformed and the mixture analysed by different chromatographic techniques. The aroma character of the ?-terpineol thioacetates was described as exotic, sweet, blackcurrant, roasted and sulphury. Of eight lipases and two esterases assayed, only non-immobilized pig liver esterase (PLE) hydrolysed ?-terpineol thioacetates into the corresponding ?-terpineol thiols. When reactions were performed in 0.2?m phosphate buffer at pH?8.0 and 30?°C with non-immobilized PLE, ?-terpineol thiols were produced in an optimal yield of 88% after 24?h of reaction time. The aroma character of ?-terpineol thiols was described as green, exotic and fresh grapefruit. Flavouring powders were prepared by freeze-drying the ?-terpineol thioacetates and ?-terpineol thiols in the presence of maltodextrine. Preliminary applications showed that these flavouring preparations could be used to improve the flavour quality of lighter cooked notes and tropical fruit aromas. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25400090

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

2015-01-01

343

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

Directory of Open Access Journals (Sweden)

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.

Gareth J. Rowlands

2009-03-01

344

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

International Nuclear Information System (INIS)

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.

345

MERCURY(II) ADSORPTION FROM WASTEWATERS USING A THIOL FUNCTIONAL ADSORBENT  

Science.gov (United States)

The removal of mercury(II) from wastewaters (coal-fired utility plant scrubber solutions) using a thiol functional organoceramic composite (SOL-AD-IV) is investigated. A simulant is employed as a surrogate to demonstrate the removal of mercury from real waste solutions. Equilibri...

346

TOXICOLOGICAL HIGHLIGHT (REDOX REDUX: A CLOSER LOOK AT CONCEPTAL LOW MOLECULAR WEIGHT THIOLS)  

Science.gov (United States)

Glutathione (GSH) is present as the most abundant low molecular weight thiol (LMWT) in virtually all mitochondria-bearing eucaryotic cells, often at millimolar concentrations (Meister, 1988). Functions of GSH include roles in DNA and protein synthesis, maintenance of cell membra...

347

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

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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.

Rowlands, Gareth J.; Seacome, Richard J.

2009-01-01

348

Thiol-vinyl systems as shape memory polymers and novel two-stage reactive polymer systems  

Science.gov (United States)

The focus of this research was to formulate, characterize and tailor the reaction methodologies and material properties of thiol-vinyl systems to develop novel polymer platforms for a range of engineering applications. Thiol-ene photopolymers were demonstrated to exhibit several advantageous characteristics for shape memory polymer systems for a range of biomedical applications. The thiol-ene shape memory polymer systems were tough and flexible as compared to the acrylic control systems with glass transition temperatures between 30 and 40 °C; ideal for actuation at body temperature. The thiol-ene polymers also exhibited excellent shape fixity and a rapid and distinct shape memory actuation response along with free strain recoveries of greater than 96% and constrained stress recoveries of 100%. Additionally, two-stage reactive thiol-acrylate systems were engineered as a polymer platform technology enabling two independent sets of polymer processing and material properties. There are distinct advantages to designing polymer systems that afford two distinct sets of material properties -- an intermediate polymer that would enable optimum handling and processing of the material (stage 1), while maintaining the ability to tune in different, final properties that enable the optimal functioning of the polymeric material (stage 2). To demonstrate the range of applicability of the two-stage reactive systems, three specific applications were demonstrated; shape memory polymers, lithographic impression materials, and optical materials. The thiol-acrylate reactions exhibit a wide range of application versatility due to the range of available thiol and acrylate monomers as well as reaction mechanisms such as Michael Addition reactions and free radical polymerizations. By designing a series of non-stoichiometeric thiol-acrylate systems, a polymer network is initially formed via a base catalyzed 'click' Michael addition reaction. This self-limiting reaction results in a Stage 1 polymer with excess acrylic functional groups within the network. At a later point in time, the photoinitiated, free radical polymerization of the excess acrylic functional groups results in a highly crosslinked, robust material system. By varying the monomers within the system as well as the stoichiometery of thiol to acrylate functional groups, the ability of the two-stage reactive systems to encompass a wide range of properties at the end of both the stage 1 and stage 2 polymerizations was demonstrated. The thiol-acrylate networks exhibited intermediate Stage 1 rubbery moduli and glass transition temperatures that range from 0.5 MPa and -10 ºC to 22 MPa and 22 ºC respectively. The same polymer networks can then attain glass transition temperatures that range from 5 ºC to 195 ºC and rubbery moduli of up to 200 MPa after the subsequent photocure stage. Two-stage reactive polymer composite systems were also formulated and characterized for thermomechanical and mechanical properties. Thermomechanical analysis showed that the fillers resulted in a significant increase in the modulus at both stage 1 and stage 2 polymerizations without a significant change in the glass transition temperatures (Tg). The two-stage reactive matrix composite formed with a hexafunctional acrylate matrix and 20 volume % silica particles showed a 125% increase in stage 1 modulus and 101% increase in stage 2 modulus, when compared with the modulus of the neat matrix. Finally, the two-stage reactive polymeric devices were formulated and designed as orthopedic suture anchors for arthroscopic surgeries and mechanically characterized. The Stage 1 device was designed to exhibit properties ideal for arthroscopic delivery and device placement with glass transition temperatures 25 -- 30 °C and rubbery moduli ˜ 95 MPa. The subsequent photopolymerization generated Stage 2 polymers designed to match the local bone environment with moduli ranging up to 2 GPa. Additionally, pull-out strengths of 140 N were demonstrated and are equivalent to the pull-strengths achieved by other commercially availab

Nair, Devatha P.

2011-12-01

349

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

Directory of Open Access Journals (Sweden)

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

Bansal Amrit

2009-01-01

350

Thioredoxin and NADP-thioredoxin reductase from cultured carrot cells  

Science.gov (United States)

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.

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

1987-01-01

351

Clinical application of 5alpha-reductase inhibitors.  

Science.gov (United States)

The inhibitors of 5alpha-reductase isoenzymes (1 and 2) can be schematically divided in three groups according they substrate specificity: a) pure or preferential inhibitor of 5alpha-reductase 1; b) pure or preferential inhibitor of 5alpha-reductase 2; c) dual inhibitors. Despite the fact that several steroidal and non-steroidal inhibitors have been synthesized and experimented in pharmacological models, only finasteride has been extensively used for clinical purposes. The largest application of finasteride in man has been human benign prostative hyperplasia (BPH). In addition, finasteride has been recently used for treatment of male baldness with a 50% of objective response. In women, finasteride has been used in some control trials for treatment of hirsutism with an objective favorable response. In conclusion, finasteride appears be useful for BPH, baldness and hirsutism (with caution) treatment. On the basis of experimental observations on distribution of 1 and 2 isoenzymes in human skin, scalp and prostate, the dual inhibitors should be more indicated for treatment of BPH and baldness. Similarly, the dual inhibitors seem indicated in attempting to prevent prostatic cancer. The pure 5alpha-reductase 1 inhibitors seem the ideal drugs for treatment of acne and hirsutism. PMID:11314752

Cilotti, A; Danza, G; Serio, M

2001-03-01

352

ARSENICALS INHIBIT THIOREDOXIN REDUCTASE ACTIVITY IN CULTURED RAT HEPATOCYTES  

Science.gov (United States)

ARSENICALS INHIBIT THIOREDOXIN REDUCTASE ACTIVITY IN CULTURED RAT HEPATOCYTES. S. Lin1, L. M. Del Razo1, M. Styblo1, C. Wang2, W. R. Cullen2, and D.J. Thomas3. 1Univ. North Carolina, Chapel Hill, NC; 2Univ. British Columbia, Vancouver, BC, Canada; 3National Health and En...

353

5. cap alpha. -reductase activity in rat adipose tissue  

Energy Technology Data Exchange (ETDEWEB)

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

Zyirek, M.; Flood, C.; Longcope, C.

1987-11-01

354

Stereospecific electrophoretically mediated microanalysis assay for methionine sulfoxide reductase enzymes.  

Science.gov (United States)

An electrophoretically mediated microanalysis assay (EMMA) for the determination of the stereoselective reduction of L-methionine sulfoxide diastereomers by methionine sulfoxide reductase enzymes was developed using fluorenylmethyloxycarbonyl (Fmoc)-L-methionine sulfoxide as substrate. The separation of the diastereomers of Fmoc-L-methionine sulfoxide and the product Fmoc-L-methionine was achieved in a successive multiple ionic-polymer layer-coated capillary using a 50 mM Tris buffer, pH 8.0, containing 30 mM sodium dodecyl sulfate as background electrolyte and an applied voltage of 25 kV. 4-Aminobenzoic acid was employed as internal standard. An injection sequence of incubation buffer, enzyme, substrate, enzyme, and incubation buffer was selected. The assay was optimized with regard to mixing time and mixing voltage and subsequently applied for the analysis of stereoselective reduction of Fmoc-L-methionine-(S)-sulfoxide by human methionine sulfoxide reductase A and of the Fmoc-L-methionine-(R)-sulfoxide by human methionine sulfoxide reductase B. The Michaelis-Menten constant, K m, and the maximum velocity, v max, were determined. Essentially identical data were determined by the electrophoretically mediated microanalysis assay and the analysis of the samples by CE upon offline incubation. Furthermore, it was shown for the first time that Fmoc-methionine-(R)-sulfoxide is a substrate of human methionine sulfoxide reductase B. PMID:24424966

Zhu, Qingfu; El-Mergawy, Rabab G; Heinemann, Stefan H; Schönherr, Roland; Já?, Pavel; Scriba, Gerhard K E

2014-02-01

355

Aldose reductase inhibitory activity and antioxidant capacity of pomegranate extracts.  

Science.gov (United States)

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 commercial pomegranate hull extract exhibited similar aldose reductase inhibitory activity characterized by IC(50) values ranging from 3 to 33.3 ?g/ml. They were more effective than pomegranate ethanolic seed extract with IC(50) ranging from 33.3 to 333 ?g/ml. Antioxidant action of the novel compounds was documented in a DPPH test and in a liposomal membrane model, oxidatively stressed by peroxyl radicals. All the plant extracts showed considerable antioxidant potential in the DPPH assay. Pomegranate ethanolic hull extract and commercial pomegranate hull extract executed similar protective effects on peroxidatively damaged liposomal membranes characterized by 10ethanolic seed extract showed significantly lower antioxidant activity compared to both hull extracts studied. Pomegranate extracts are thus presented as bifunctional agents combining aldose reductase inhibitory action with antioxidant activity and with potential therapeutic use in prevention of diabetic complications. PMID:22783144

Karasu, Cimen; Cumao?lu, Ahmet; Gürpinar, Ali Rifat; Kartal, Murat; Kovacikova, Lucia; Milackova, Ivana; Stefek, Milan

2012-03-01

356

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

International Nuclear Information System (INIS)

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

357

Recombinant pinoresinol/lariciresinol reductase, recombinant dirigent protein, and methods of use  

Science.gov (United States)

Dirigent proteins and pinoresinol/lariciresinol reductases have been isolated, together with cDNAs encoding dirigent proteins and pinoresinol/lariciresinol reductases. Accordingly, isolated DNA sequences are provided which code for the expression of dirigent proteins and pinoresinol/lariciresinol reductases. In other aspects, replicable recombinant cloning vehicles are provided which code for dirigent proteins or pinoresinol/lariciresinol reductases or for a base sequence sufficiently complementary to at least a portion of dirigent protein or pinoresinol/lariciresinol reductase DNA or RNA to enable hybridization therewith. In yet other aspects, modified host cells are provided that have been transformed, transfected, infected and/or injected with a recombinant cloning vehicle and/or DNA sequence encoding dirigent protein or pinoresinol/lariciresinol reductase. Thus, systems and methods are provided for the recombinant expression of dirigent proteins and/or pinoresinol/lariciresinol reductases.

Lewis, Norman G. (Pullman, WA); Davin, Laurence B. (Pullman, WA); Dinkova-Kostova, Albena T. (Baltimore, MD); Fujita, Masayuki (Kagawa, JP); Gang, David R. (Ann Arbor, MI); Sarkanen, Simo (S. Minneapolis, MN); Ford, Joshua D. (Pullman, WA)

2001-04-03

358

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

DEFF Research Database (Denmark)

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

Lokanathan, Arcot R.

2011-01-01

359

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-08-31

360

Distinct redox behaviors of chloroplast thiol enzymes and their relationships with photosynthetic electron transport in Arabidopsis thaliana.  

Science.gov (United States)

The thiol/disulfide redox network mediated by the thioredoxin (Trx) system in chloroplasts ensures light-responsive control of diverse crucial functions. Despite the suggested importance of this system, the working dynamics against changing light environments remains largely unknown. Thus, we directly assessed the in vivo redox behavior of chloroplast Trx-targeted thiol enzymes in Arabidopsis thaliana. In a time-course analysis throughout a day period that was artificially mimicked to natural light conditions, thiol enzymes showed a light-dependent shift in redox state, but the patterns were distinct among thiol enzymes. Notably, the ATP synthase CF(1-?) subunit was rapidly reduced even under low-light conditions, whereas the stromal thiol enzymes fructose 1,6-bisphosphatase, sedoheptulose 1,7-bisphosphatase, and NADP-malate dehydrogenase were gradually reduced/re-oxidized along with the increase/decrease in light intensity. Photo-reduction of thiol enzymes was suppressed by the impairment of photosynthetic linear electron transport using DCMU and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, but sensitivity to the impairment was uneven between CF(1-?) and other stromal thiol enzymes. These different dependencies of photo-reduction on electron transport, rather than the redox state of Trx and the circadian clock, could readily explain the distinct diurnal redox behaviors of thiol enzymes. In addition, our results indicate that the cyclic electron transport around PSI is also involved in redox regulation of some thiol enzymes. Based on these findings, we propose an in vivo working model of the redox regulation system in chloroplasts. PMID:24850837

Yoshida, Keisuke; Matsuoka, Yuta; Hara, Satoshi; Konno, Hiroki; Hisabori, Toru

2014-08-01

 
 
 
 
361

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

International Nuclear Information System (INIS)

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

362

Reactions of thiols with individual DNA base radicals in DNA and DNA model systems: The effect of oxygen on radioprotection  

International Nuclear Information System (INIS)

Thiol radioprotection of DNA in the living cell has been suggested to be a result of hydrogen or electron donation to free radicals generated on DNA resulting in a repair of the original radical lesion. Thus far there are no reports of reactions of DNA anion radicals with thiols. Oxygen involvement in thiol free radical reactions has been implicated in oxygen radiosensitization of cells to the lethal effects of radiation. A biological oxygen enhancement effect and a chemical oxygen enhancement effect have both been recognized. One hypothesis is that thiyl radical reactions with oxygen are the source of the chemical oxygen enhancement effect

363

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2011-01-01

364

Pyridine Nucleotide Complexes with Bacillus anthracis Coenzyme A-Disulfide Reductase: A Structural Analysis of Dual NAD(P)H Specificity  

Energy Technology Data Exchange (ETDEWEB)

We have recently reported that CoASH is the major low-molecular weight thiol in Bacillus anthracis, and we have now characterized the kinetic and redox properties of the B. anthracis coenzyme A-disulfide reductase (CoADR, BACoADR) and determined the crystal structure at 2.30 Angstroms resolution. While the Staphylococcus aureus and Borrelia burgdorferi CoADRs exhibit strong preferences for NADPH and NADH, respectively, B. anthracis CoADR can use either pyridine nucleotide equally well. Sequence elements within the respective NAD(P)H-binding motifs correctly reflect the preferences for S. aureus and Bo. burgdorferi CoADRs, but leave questions as to how BACoADR can interact with both pyridine nucleotides. The structures of the NADH and NADPH complexes at ca. 2.3 Angstroms resolution reveal that a loop consisting of residues Glu180-Thr187 becomes ordered and changes conformation on NAD(P)H binding. NADH and NADPH interact with nearly identical conformations of this loop; the latter interaction, however, involves a novel binding mode in which the 2'-phosphate of NADPH points out toward solvent. In addition, the NAD(P)H-reduced BACoADR structures provide the first view of the reduced form (Cys42-SH/CoASH) of the Cys42-SSCoA redox center. The Cys42-SH side chain adopts a new conformation in which the conserved Tyr367'-OH and Tyr425'-OH interact with the nascent thiol(ate) on the flavin si-face. Kinetic data with Y367F, Y425F, and Y367, 425F BACoADR mutants indicate that Tyr425' is the primary proton donor in catalysis, with Tyr367' functioning as a cryptic alternate donor in the absence of Tyr425'.

Wallen,J.; Paige, C.; Mallett, T.; Karplus, P.; Claiborne, A.

2008-01-01

365

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

International Nuclear Information System (INIS)

In this paper, the multifaceted Cr(VI) toxicity over the freshwater green alga Monoraphidium convolutum was assessed by concomitantly monitoring thiol-dependent redox balances, photosynthesis activity and growth-survival scores. Control group showed exponential growth rate at (5.78 ± 0.29) division/day until 8th day with linear increasing chlorophyll a/protein ratios (CHLa/PROT) throughout the period. Cultures of M. convolutum were exposed for 5 days to Cr(VI) concentrations from 0 up to 100 mg/L showing that CHLa/PROT ratios were sensibly affected, in agreement to the calculated LC50,48h (5.38 ± 0.72) mg/L from the concentration-response curve of cell mortality after 48 h. Regarding photosynthesis effects, Cr(VI) concentrations >1.0 mg/L showed significant increases in short-term (after 2 h) electron transfer rates (ETR) and quantum yields of photosystem II (?PSII), followed by subsequent decline of both parameters after 48 and 72 h. Biochemical analyses showed that maximal GSH concentrations in algal cultures were observed upon 1 mg Cr(VI)/L and higher dichromate concentrations dramatically increased the activity of antioxidant GSH-dependent enzymes ascorbate peroxidase and glutathione reductase. However, no variation was observed in the cellular GSH levels, whereas GSSG and lipid peroxidation indexes abruptly increased upon 10 mg Cr(VI)/L exposure. Altogether, plant physiology, photosynthesis and biochemical data suggest that the GSH-dependemical 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.

366

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

International Nuclear Information System (INIS)

Inhalation is a common form of exposure to acrolein, a toxic reactive volatile aldehyde that is a ubiquitous environmental pollutant. Bronchial epithelial cells would be directly exposed to inhaled acrolein. The thioredoxin (Trx) system is essential for the maintenance of cellular thiol redox balance, and is critical for cell survival. Normally, thioredoxin reductase (TrxR) maintains the cytosolic (Trx1) and mitochondrial (Trx2) thioredoxins in the reduced state, and the thioredoxins keep the peroxiredoxins (Prx) reduced, thereby supporting their peroxidase function. The effects of acrolein on TrxR, Trx and Prx in human bronchial epithelial (BEAS-2B) cells were determined. A 30-min exposure to 5 ?M acrolein oxidized both Trx1 and Trx2, although significant effects were noted for Trx1 at even lower acrolein concentrations. The effects on Trx1 and Trx2 could not be reversed by treatment with disulfide reductants. TrxR activity was inhibited 60% and >85% by 2.5 and 5 ?M acrolein, respectively. The endogenous electron donor for TrxR, NADPH, could not restore its activity, and activity did not recover in cells during a 4-h acrolein-free period in complete medium. The effects of acrolein on TrxR and Trx therefore extend beyond the duration of exposure. While there was a strong correlation between TrxR inhibition and Trx1 oxidation, the irreversible effects on Trx1 suggest direct effects of acrolein rather than loss of reducing equivalents from TrxR. Trx2 did not become oxalents 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

367

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

Directory of Open Access Journals (Sweden)

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.

Ku Maurice SB

2009-08-01

368

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Sugiyama, Toru; Michel, Thomas

2009-01-01

369

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

International Nuclear Information System (INIS)

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

370

Synthesis and characterization of pH-sensitive thiol-containing chitosan beads for controlled drug delivery applications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this study was to develop chitosan-based materials in drug delivery systems possessing covalent attachment of thiol moieties. Thiol-containing chitosan (TCS), found to be soluble in water, was synthesized by graft copolymerization technique. The TCS beads were prepared by using tripolyphoshate, at pH 4.0. The morphology of TCS beads was examined by scanning electron microscopy. The in vitro drug release behavior was studied in phosphate buffer solution at vario...

Jayakumar, R.; Reis, R. L.; Mano, J. F.

2007-01-01

371

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

Directory of Open Access Journals (Sweden)

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

Anita M. Raut

2013-04-01

372

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

DEFF Research Database (Denmark)

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

Berthold, Anton; Sagar, Kaushal Shashikant

2011-01-01

373

Reactive Superhydrophobic Surface and Its Photoinduced Disulfide-ene and Thiol-ene (Bio)functionalization.  

Science.gov (United States)

Reactive superhydrophobic surfaces are highly promising for biotechnological, analytical, sensor, or diagnostic applications but are difficult to realize due to their chemical inertness. In this communication, we report on a photoactive, inscribable, nonwettable, and transparent surface (PAINTS), prepared by polycondensation of trichlorovinylsilane to form thin transparent reactive porous nanofilament on a solid substrate. The PAINTS shows superhydrophobicity and can be conveniently functionalized with the photoclick thiol-ene reaction. In addition, we show for the first time that the PAINTS bearing vinyl groups can be easily modified with disulfides under UV irradiation. The effect of superhydrophobicity of PAINTS on the formation of high-resolution surface patterns has been investigated. The developed reactive superhydrophobic coating can find applications for surface biofunctionalization using abundant thiol or disulfide bearing biomolecules, such as peptides, proteins, or antibodies. PMID:25486338

Li, Junsheng; Li, Linxian; Du, Xin; Feng, Wenqian; Welle, Alexander; Trapp, Oliver; Grunze, Michael; Hirtz, Michael; Levkin, Pavel A

2015-01-14

374

Modification of porous silicon rugate filters through thiol-yne photochemistry  

Energy Technology Data Exchange (ETDEWEB)

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)

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

375

Eucalyptus tolerance mechanisms to lanthanum and cerium: subcellular distribution, antioxidant system and thiol pools.  

Science.gov (United States)

Guanglin 9 (Eucalyptus grandis × Eucalyptus urophlla) and Eucalyptus grandis 5 are two eucalyptus species which have been found to grow normally in soils contaminated with lanthanum and cerium, but the tolerance mechanisms are not clear yet. In this study, a pot experiment was conducted to investigate the tolerance mechanisms of the eucalyptus to lanthanum and cerium. Cell walls stored 45.40-63.44% of the metals under lanthanum or cerium stress. Peroxidase and catalase activities enhanced with increasing soil La or Ce concentrations up to 200 mg kg(-1), while there were no obvious changes in glutathione and ascorbate concentrations. Non-protein thiols concentrations increased with increasing treatment levels up to 200 mg kg(-1), and then decreased. Phytochelatins concentrations continued to increase under La or Ce stress. Therefore, the two eucalyptus species are La and Ce tolerant plants, and the tolerance mechanisms include cell wall deposition, antioxidant system response, and thiol compound synthesis. PMID:25303462

Shen, Yichang; Zhang, Shirong; Li, Sen; Xu, Xiaoxun; Jia, Yongxia; Gong, Guoshu

2014-12-01

376

Synthesis of novel perphenylcarbamated ?-cyclodextrin based chiral stationary phases via thiol-ene click chemistry.  

Science.gov (United States)

Novel cyclodextrin (CD) chiral stationary phases (CD-CSPs) with well-defined structure have been successfully synthesized by immobilization of mono/di(10-undecenoyl)-perphenylaminocarbonyl ?-CD on the 3-mercaptopropyl functionalized silica gel via thiol-ene click chemistry. The phenyl carbamate groups on the rims of CD extended the cavity of CD-CSPs, which facilitated the formation of inclusion complex with various types of racemic compounds under RP mode, and also improved the ?-? stacking interaction, dipole-dipole interaction, and hydrogen bonding interaction with racemic compounds under normal phase mode. Fifteen racemic compounds were successfully separated on this CD-CSP with HPLC, and the chromatographic results also demonstrated that thiol-ene click chemistry affords a facile approach for preparation of CSPs. PMID:25043417

Huang, Guang; Ou, Junjie; Zhang, Xiaodan; Ji, Yongsheng; Peng, Xiaojun; Zou, Hanfa

2014-10-01

377

Au particle deposition onto self-assembled monolayers of thiol and dithiol molecules  

Science.gov (United States)

Gold depositions on self-assembled monolayers (SAMs) of thiol (HS(CH 2) 7CH 3) and dithiol (HS(CH 2) nSH, n=6, 8, 10) molecules were investigated by a scanning tunneling microscope in air. In the case of thiols, evaporated gold atoms were found to penetrate and form monoatomic height islands under the SAMs. On the contrary, gold deposition onto the dithiols resulted in the formation of the gold particles on top of the SAMs. Each Au particle is estimated to have ˜200 atoms and this size is independent of Au coverage, at least below 1 ML. The electrical properties such as Coulomb blockade were also studied by scanning tunneling spectroscopy.

Ohgi, T.; Sheng, H.-Y.; Nejoh, H.

1998-06-01

378

Selectivity in bond cleavage in amines and thiols by dissociative electron attachment  

International Nuclear Information System (INIS)

A study on the dissociative electron attachment to amines and thiols is presented. The previous observations made for oxygen containing compounds, namely the use of methyl as a protective group, the dependence of the energy for the observed DEA band on which alkyl group is lost and the non-dissociative nature of the (2n, 3s2) Feshbach resonances with respect to the Y-C bond (Y=N or O), are extended to amines. Amendments to these trends are provided by the study of primary and secondary amines. For thiols the selectivity in bond cleavage is reflected in the fact that S-H bonds are broken in the 0-3 eV range by shape resonances, while Feshbach resonances lead to the preferential breaking of the S-C bonds in the 7-15 eV range.

379

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

International Nuclear Information System (INIS)

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

380

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

Science.gov (United States)

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

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

2013-12-01

 
 
 
 
381

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

International Nuclear Information System (INIS)

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

382

Modification of porous silicon rugate filters through thiol-yne photochemistry  

International Nuclear Information System (INIS)

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)

383

?4-Sulfido-bis­{(?-2-furyl­methane­thiol­ato)bis­[tricarbonyl­iron](Fe—Fe)}  

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The title compound, [Fe4(C5H5OS)2S(CO)12], was prepared by the direct reaction of Fe3(CO)12 and 2-furyl­methane­thiol in tetra­hydro­furan. Desulfurization took place readily to form an Fe4S3 cluster. The mol­ecule consists of two similar [(?-2-C4H3O—CH2S)Fe2(CO)6] moieties joined to a spiro-type four-coordinate ?4-S atom such that this bridging sulfur is tetra­hedrally coordinated to the four Fe atoms. In each diiron subcluster core, the 2-furyl­methane­thiol­ate ligand bridges ...

Han, Cong; Huang, Xiao-nan; Guo, Yan-ling; Liu, Wei

2010-01-01

384

Field effect on digestive ripening of thiol-capped gold nanoparticles  

International Nuclear Information System (INIS)

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

385

Field effect on digestive ripening of thiol-capped gold nanoparticles  

Science.gov (United States)

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.

Lin, Meng-Lin; Yang, Fuqian; Peng, J. S.; Lee, Sanboh

2014-02-01

386

Field effect on digestive ripening of thiol-capped gold nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

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.

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

387

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

Science.gov (United States)

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

Bhatia, Meenakshi; Ahuja, Munish

2013-01-01

388

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

Science.gov (United States)

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

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

2014-02-17

389

A fluorescent probe to detect thiol-containing amino acids in solid tumors.  

Science.gov (United States)

Early detecting of cancer is critical to provide proper treatment and to improve survival of patients. Here, we reported a highly sensitive ratiometric (yellow emission (550 nm) to blue emission (496 nm)) fluorescent probe 1 developed for detection of thiol-containing amino acids. This probe successfully eliminates interference from background autofluorescence, and discriminates between human carcinoma and normal cells by detecting intracellular thiol levels in living cells (P < 0.05). Furthermore, the ability of the probe to identify growing tumors by measuring GSH in the tissues as well as in the fresh blood of tumor xenograft mice. Additionally, the ratio of the emission intensity at two different wavelengths can provide quantitative analysis of glutathione (GSH) in the living systems. It suggests that it represents a promising prognostic and diagnostic marker, with extensive and simple potential clinical applications. PMID:24529899

Ren, Wen Xiu; Han, Jiyou; Pradhan, Tuhin; Lim, Ja-Yun; Lee, Jae Hong; Lee, Jaehun; Kim, Jong-Hoon; Kim, Jong Seung

2014-04-01

390

Tritium isotopic exchange between hydrogen sulfide and thiols in gas phase  

International Nuclear Information System (INIS)

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

391

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

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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.

J.S. Pamudji

2011-01-01

392

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

International Nuclear Information System (INIS)

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

393

Fabrication and electrochemistry study of multi-thiol coronary molecule monolayers  

International Nuclear Information System (INIS)

Single-component monolayer of novel multi-thiol coronary molecule and two-component mixed monolayer composed of coronary molecule and n-alkanethiol on gold substrates are described. The assembly of monolayers is characterized by ellipsometry, infrared spectroscopy and X-ray photoelectron spectroscope. The electrochemical properties of the single- and two-component monolayers are evaluated by cyclic voltammetry and electrochemical impedance spectroscopy experiments. Coronary molecule with multi-thiol groups has the ability to form stable monolayer via the interaction of mercapto groups and Au surface. Electrochemical impedance measurements indicate that 89.9% of the gold surface is blocked by the coronary molecule, which is attributed to the special spatial structure of the coronary molecule. The uncovered site on gold surface in coronary molecule monolayer could be occupied by the second suitable molecule. The mixed monolayer prepared by stepwise assembly of coronary molecule and n-alkanethiol has complete compact packing and few defects.

394

The preparation and evaluation of bifunctional latent thiol radioisotope chelators for attachment to antibodies and peptides  

International Nuclear Information System (INIS)

A number of radioisotope chelators which can be attached to antibodies, proteins, or peptides have been reported in the scientific literature. Unfortunately, many of these systems contain thiol functionalities that may lead to stability problems when they are conjugated to peptides that contain sensitive disulfide linkages. The authors now wish to report the preparation of a series of bifunctional compounds which possess a single linking group for attachment to proteins or peptides and multiple latent thiol substituents that form complexes with radioisotopes. These systems have been bound to whole antibody and peptide residues to provide conjugates that chelate with a variety of medically useful radioactive metals. A discussion of the syntheses of these compounds and the results of their radiolabeling studies are presented

395

Inhibition of both thioredoxin reductase and glutathione reductase may contribute to the anticancer mechanism of TH-302.  

Science.gov (United States)

Selenium-containing thioredoxin reductase (TrxR) is an important target of cancer therapy. Many useful anticancer agents including bis-alkylating agents, cisplatin, and arsenic trioxide are known to interact with the selenocysteine dipeptide in the carboxy terminal region of thioredoxin reductase and inactivate its ability to reduce thioredoxin. Some investigators have postulated that the inactivation of TrxR may add to the cytotoxic potential of these anticancer agents. TH-302 is a newly developed antineoplastic drug which represents a potential new class of tumor selective hypoxia-activated prodrugs (HAPs). TH-302 is an inactive prodrug created by the covalent conjugation of 2-nitroimidazole as an oxygen sensor to bromo-isophosphoramide (Br-IPM). In the presence of severe hypoxia and near anoxia, the two imidazole sensor moiety undergoes reduction and the Br-IPM is released in situ. Bromo-IPM is a more potential analog of Chloro-IPM, the active alkylating moiety that is derived by activation of ifosfamide (IFO). We previously demonstrated that IFO could inhibit tumor TrxR activity and chloro-IPM is known to bind covalently to the seleno-cysteine dipeptide in thioredoxin reductase. The present study assessed the ability of TH-302 to activate in the tumors of mice-bearing hepatoma 22 (H22) and inactivate the tumor TrxR. In mice-bearing hepatoma 22 (H22) solid tumors, intraperitoneal (i.p.) injection with TH-302 at the dose of 200 mg/kg administered twice, a regimen which was well tolerated by the mice, significantly inhibited tumor growth. Also in this mice model, i.p. TH-302 at the dose of 300 mg/kg, which would be the maximum single i.p. administration dose tolerated by mice, and which induced only 2% body weight loss, significantly inhibited both TrxR and glutathione reductase (GR) activities by 46% (P < 0.001) and 60% (P < 0.001) as compared with the controls, respectively, at 3 h after the injection. Since TrxR is a key player in thioredoxin system and GR is the major reductase for the reduction of oxidized glutathione in glutathione system, the present results imply the anticancer effect of TH-302 is associated concurrently with modulation of TrxR and GR. These findings suggest that the anticancer activity of TH-302 in this model system may associate with both DNA alkylation and the modulation of TrxR and GR. In addition, they suggest that, by inhibition of these two critical reductases, with less glutathione available to intercept the reactive intermediates involved in DNA alkylation, the antitumor effects of the chemotherapy would be enhanced. PMID:19838642

Li, Shengrong; Zhang, Jinsong; Li, Jun; Chen, Dongming; Matteucci, Mark; Curd, John; Duan, Jian-Xin

2010-09-01

396

Kinetics of substrate inhibition of periplasmic nitrate reductase.  

Science.gov (United States)

Periplasmic nitrate reductase catalyzes the reduction of nitrate into nitrite using a mononuclear molybdenum cofactor that has nearly the same structure in all enzymes of the DMSO reductase family. In previous electrochemical investigations, we found that the enzyme exists in several inactive states, some of which may have been previously isolated and mistaken for catalytic intermediates. In particular, the enzyme slowly and reversibly inactivates when exposed to high concentrations of nitrate. Here, we study the kinetics of substrate inhibition and its dependence on electrode potential and substrate concentration to learn about the properties of the active and inactive forms of the enzyme. We conclude that the substrate-inhibited enzyme never significantly accumulates in the EPR-active Mo(+V) state. This conclusion is relevant to spectroscopic investigations where attempts are made to trap a Mo(+V) catalytic intermediate using high concentrations of nitrate. PMID:24882638

Jacques, Julien G J; Burlat, Bénédicte; Arnoux, Pascal; Sabaty, Monique; Guigliarelli, Bruno; Léger, Christophe; Pignol, David; Fourmond, Vincent

2014-10-01

397

Acyloxy Nitroso Compounds as Nitroxyl (HNO) Donors: Kinetics, Reactions with Thiols and Vasodilation Properties  

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Acyloxy nitroso compounds hydrolyze to nitroxyl (HNO), a nitrogen monoxide with distinct chemistry and biology. Ultraviolet-visible spectroscopy and mass spectrometry show hydrolysis rate depends on pH and ester group structure with the observed rate being trifluoroacetate (3) > acetate (1) > pivalate (2). Under all conditions, 3 rapidly hydrolyzes to HNO. A combination of spectroscopic, kinetic and product studies show that addition of thiols increases the decomposition rate of 1 and 2 leadi...

Shoman, Mai E.; Dumond, Jenna F.; Isbell, T. S.; Crawford, J. H.; Brandon, Angela; Honovar, Jaideep; Vitturi, Dario A.; White, C. R.; Patel, R. P.; King, S. Bruce

2011-01-01

398

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

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Autism spectrum disorder (ASD) is a neurological disorder in which a significant number of the children experience a developmental regression characterized by a loss of previously acquired skills and abilities. Typically reported are losses of verbal, nonverbal, and social abilities. Several recent studies suggest that children diagnosed with an ASD have abnormal sulfation chemistry, limited thiol availability, and decreased glutathione (GSH) reserve capacity, resulting in a compromised oxida...

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

2013-01-01

399

Magnetometry and electron paramagnetic resonance studies of phosphine- and thiol-capped gold nanoparticles  

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In the last years, the number of studies performed by wholly independent research groups that confirm the permanent magnetism, first observed in our research lab, for thiol-capped Au nanoparticles (NPs) has rapidly increased. Throughout the years, the initial magnetometry studies have been completed with element-specific magnetization measurements based on, for example, the x-ray magnetic circular dichroism technique that have allowed the identification of gold as the magnetic moment carrier....

Guerrero, E.; Mun?oz-ma?rquez, Miguel A?ngel; Ferna?ndez-camacho, A.; Crespo, P.; Hernando, A.; Lucena, R.; Conesa, J. C.

2010-01-01

400

Requirement of Transmembrane Transport for S-Nitrosocysteine-dependent Modification of Intracellular Thiols*  

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S-Nitrosothiols have been implicated as intermediary transducers of nitric oxide bioactivity; however, the mechanisms by which these compounds affect cellular functions have not been fully established. In this study, we have examined the effect of S-nitrosothiol transport on intracellular thiol status and upon the activity of a target protein (caspase-3), in bovine aortic endothelial cells. We have previously demonstrated that the specific transport of amino acid-based S-nitrosothiols (S-nitr...

Broniowska, Katarzyna A.; Zhang, Yanhong; Hogg, Neil

2006-01-01

 
 
 
 
401

Molecular basis for the thiol sensitivity of insulin-degrading enzyme  

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Insulin-degrading enzyme (IDE) is a ubiquitous zinc-metalloprotease that hydrolyzes several pathophysiologically relevant peptides, including insulin and the amyloid ?-protein (A?). IDE is inhibited irreversibly by compounds that covalently modify cysteine residues, a mechanism that could be operative in the etiology of type 2 diabetes mellitus (DM2) or Alzheimer's disease (AD). However, despite prior investigation, the molecular basis underlying the sensitivity of IDE to thiol-alkylating a...

Neant-fery, Marie; Garcia-ordon?ez, Rube?n D.; Logan, Todd P.; Selkoe, Dennis J.; Li, Lilin; Reinstatler, Lael; Leissring, Malcolm A.

2008-01-01

402

Microdialysis sampling of the isothiazolone, PD-161374, and its thiol and disulfide metabolites  

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A method based on microdialysis sampling combined with high-performance liquid chromatography (HPLC) has been developed for monitoring the anti-HIV agent PD-161374 (isothiazolone) and its thiol and disulfide metabolites in blood. It was demonstrated that unlike blood withdraw and extraction, microdialysis sampling can preserve the distribution among the isothiazolone and its metabolites in blood. The use of a narrow-bore HPLC system, combined with the relatively high probe extraction efficien...

Ye, Meng; Rossi, David T.; Lunte, Craig E.

2000-01-01

403

A Central Role for Thiols in Plant Tolerance to Abiotic Stress  

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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,...

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

2013-01-01

404

Carbocysteine restores steroid sensitivity by targeting histone deacetylase 2 in a thiol/GSH-dependent manner.  

Science.gov (United States)

Steroid insensitivity is commonly observed in patients with chronic obstructive pulmonary disease. Here, we report the effects and mechanisms of carbocysteine (S-CMC), a mucolytic agent, in cellular and animal models of oxidative stress-mediated steroid insensitivity. The following results were obtained: oxidative stress induced higher levels of interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-?), which are insensitive to dexamethasone (DEX). The failure of DEX was improved by the addition of S-CMC by increasing histone deacetylase 2 (HDAC2) expression/activity. S-CMC also counteracted the oxidative stress-induced increase in reactive oxygen species (ROS) levels and decreases in glutathione (GSH) levels and superoxide dismutase (SOD) activity. Moreover, oxidative stress-induced events were decreased by the thiol-reducing agent dithiothreitol (DTT), enhanced by the thiol-oxidizing agent diamide, and the ability of DEX was strengthened by DTT. In addition, the oxidative stress-induced decrease in HDAC2 activity was counteracted by S-CMC by increasing thiol/GSH levels, which exhibited a direct interaction with HDAC2. S-CMC treatment increased HDAC2 recruitment and suppressed H4 acetylation of the IL-8 promoter, and this effect was further ablated by addition of buthionine sulfoximine, a specific inhibitor of GSH synthesis. Our results indicate that S-CMC restored steroid sensitivity by increasing HDAC2 expression/activity in a thiol/GSH-dependent manner and suggest that S-CMC may be useful in a combination therapy with glucocorticoids for treatment of steroid-insensitive pulmonary diseases. PMID:25500537

Song, Yun; Lu, Hao-Zhong; Xu, Jian-Rong; Wang, Xiao-Lin; Zhou, Wei; Hou, Li-Na; Zhu, Liang; Yu, Zhi-Hua; Chen, Hong-Zhuan; Cui, Yong-Yao

2015-01-01

405

Selective Hg(II) Detection in Aqueous Solution with Thiol Derivatized Fluoresceins  

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The syntheses and photophysical properties of MS2 and MS3, two asymmetrically derivatized fluorescein-based dyes designed for Hg(II) detection, are described. These sensors each contain a single pyridyl-amine-thiol metal-binding moiety, form 1:1 complexes with Hg(II), and exhibit selectivity for Hg(II) over other Group 12 metals, alkali and alkaline earth metals, and most divalent first-row transition metals. Both dyes display superior brightness (? × ?) and fluorescence enhancement follow...

Nolan, Elizabeth M.; Racine, Maryann E.; Lippard, Stephen J.

2006-01-01

406

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

Science.gov (United States)

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

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

2014-04-14

407

Protein Tyrosine Nitration and Thiol Oxidation by Peroxynitrite—Strategies to Prevent These Oxidative Modifications  

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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 sensi...

Thomas Münzel; Serge Bottari; Tadashi Tanabe; Masayuki Wada; Alexandra Megner; Patrick Schmidt; Sebastian Steven; Matthias Oelze; Stefan Schildknecht; Markus Bachschmid; Steffen Daub; Andreas Daiber; Volker Ullrich

2013-01-01

408

Reversible maleimide-thiol adducts yield glutathione-sensitive poly(ethylene glycol)-heparin hydrogels.  

Science.gov (United States)

We have recently reported that retro Michael-type addition reactions can be employed for producing labile chemical linkages with tunable sensitivity to physiologically relevant reducing potentials. We reasoned that such strategies would also be useful in the design of glutathione-sensitive hydrogels for a variety of targeted delivery and tissue engineering applications. In this report, we describe hydrogels in which maleimide-functionalized low molecular weight heparin (LMWH) is crosslinked with various thiol-functionalized poly(ethylene glycol) (PEG) multi-arm star polymers. Judicious selection of the chemical identity of the thiol permits tuning of degradation via previously unstudied, but versatile chemical methods. Thiol pKa and hydrophobicity affected both the gelation and degradation of these hydrogels. Maleimide-thiol crosslinking reactions and retro Michael-type addition reactions were verified with (1)H NMR during the crosslinking and degradation of hydrogels. PEGs esterified with phenylthiol derivatives, specifically 4-mercaptophenylpropionic acid or 2,2-dimethyl-3-(4-mercaptophenyl)propionic acid, induced sensitivity to glutathione as shown by a decrease in hydrogel degradation time of 4-fold and 5-fold respectively, measured via spectrophotometric quantification of LMWH. The degradation proceeded through the retro Michael-type addition of the succinimide thioether linkage, with apparent pseudo-first order reaction constants derived from oscillatory rheology experiments of 0.039 ± 0.006 h(-1) and 0.031 ± 0.003 h(-1). The pseudo-first order retro reaction constants were approximately an order of magnitude slower than the degradation rate constants for hydrogels crosslinked via disulfide linkages, indicating the potential use of these Michael-type addition products for reduction-mediated release and/or degradation, with increased blood stability and prolonged drug delivery timescales compared to disulfide moieties. PMID:23766781

Baldwin, Aaron D; Kiick, Kristi L

2013-01-01

409

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

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

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

1982-01-01

410

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

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

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

2008-01-01

411

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

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

Mathieu Lazerges; Hubert Perrot; Niriniony Rabehagasoa; Chantal Compère

2012-01-01

412

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

Directory of Open Access Journals (Sweden)

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

Mingzhong Cai

2009-09-01

413

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

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

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

2007-01-01

414

Optical Properties and Application of a Reactive and Bioreducible Thiol-Containing Tetramethylrhodamine Dimer  

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Thiolated dimeric tetramethylrhodamine (TAMRA) was synthesized in a straightforward procedure utilizing commercially available 5(6)-succinimidyl TAMRA and cystamine hydrochloride. The thiol-containing TAMRA dimer displayed distinct spectral properties in reduced and oxidized forms; covalent dimer formation produced greater effects on the spectral properties than previously reported for non-covalent TAMRA dimers or dimers formed with shorter carbon spacers. The resulting TAMRA disulfide dimer ...

Christie, R. James; Tadiello, Constantino J.; Chamberlain, Lisa M.; Grainger, David W.

2009-01-01

415

?-Thiolactones as prodrugs of thiol-based glutamate carboxypeptidase II (GCPII) inhibitors  

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?-Thiolactones derived from thiol-based glutamate carboxypeptidase II (GCPII) inhibitors were evaluated as prodrugs. In rat liver microsomes, 2-(3-mercaptopropyl)pentanedioic acid (2-MPPA, 1) was gradually produced from 3-(2-oxotetrahydro-thiopyran-3-yl)propionic acid (5), a thiolactone derived from 1. Compound 1 was detected in plasma at concentrations well above its IC50 value for GCPII following oral administration of 5 in rats. Consistent with the oral plasma pharmac...

Ferraris, Dana V.; Majer, Pavel; Ni, Chiyou; Slusher, C. Ethan; Rais, Rana; Wu, Ying; Wozniak, Krystyna M.; Alt, Jesse; Rojas, Camilo; Slusher, Barbara S.; Tsukamoto, Takashi

2013-01-01

416

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

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Cyclic peptides and peptoids were prepared using the thiolene Michael-type reaction. The linear precursors were provided with additional functional groups allowing for subsequent conjugation: an orthogonally protected thiol, a protected maleimide, or an alkyne. The functional group for conjugation was placed either within the cycle or in an external position. The click reactions employed for conjugation with suitably derivatized nucleoside or oligonucleotides were either cycloadditions (D...

Elduque Busquets, Xavier; Pedroso Muller, Enrique; Grandas Sagarra, Anna

2014-01-01