Cysteine In Solution Research Articles

Tandem heterocyclization activity of the multidomain 230 kDa HMWP2 subunit of Yersinia pestis yersiniabactin synthetase: interaction of the 1-1382 and 1383-2035 fragments.

The six-domain, 2035-amino acid subunit high-molecular weight protein 2 (HMWP2) activates salicylate and two cysteines and loads them covalently on its three carrier protein domains during assembly of the iron-chelating virulence factor, yersiniabactin of the plague bacterium Yersinia pestis. The 1-1382 fragment of HMWP2 (ArCP-Cy1-A), overproduced in Escherichia coli, contains the first three domains: the aryl carrier protein (ArCP) domain, the cysteine specific adenylation domain (A), and the first condensation/cyclization domain (Cy1). The ArCP can be posttranslationally phosphopantetheinylated on Ser52 and then loaded with a salicyl group on the phosphopantetheine (Ppant) thiol by action of the YbtE, a salicyl-AMP ligase. The HMWP2 1-1382 fragment can activate L-cysteine as Cys-AMP. The HMWP2 1383-2035 fragment contains the remaining three domains: two peptidyl carrier proteins (PCP1 and PCP2) separated by a second condensation/cyclization domain (Cy2). Phosphopantetheinylation of the HMWP2 1383-2035 fragment at Ser1439 (PCP1) and Ser1977 (PCP2) facilitates cysteinylation of both thiols by HMWP2 1-1382. When the holo 1-1382 and bis-holo 1383-2035 protein fragments are mixed with ATP, salicylate, and cysteine, four products are slowly released [salicylcysteine (Sal-Cys), (hydroxyphenylthiazolinyl)cysteine (HPT-Cys), HPT-Cys-Cys, and the bisheterocyclic HPTT-Cys], reflecting thiolytic rerouting by cysteine in solution of elongating acyl-S-enzyme intermediates tethered at ArCP, PCP1, and PCP2 carrier protein domains, respectively. Conducting the in trans reconstitution with the S1439A mutant of HMWP2 1383-2035 releases only Sal-Cys, while the S1977A mutant leads to HPT-Cys formation but not HPT-Cys-Cys or HPTT-Cys. These results suggest localization of particular acyl-S-enzyme intermediates to each of the three carrier protein regions and also establish the sequential action of Cy1 and Cy2, with the latter producing the tandem 4,2-bisheterocyclic hydroxyphenylthiazolinylthiazolinyl (HPTT) moiety characteristic of this class of siderophores.

Application of Cysteine Monolayers for Electrochemical Determination of Sub-ppb Copper(II)

Electrodes with the functionality of amino acids can be easily prepared by taking advantage of strong sulfur−gold interactions and immersing gold electrodes into cysteine solutions. Such electrodes exhibit excellent sensitivity and selectivity toward copper(II) determination, because the bidentate chelation of amino acids toward copper(II) is effective and far superior than that toward any other metal ions. In this study, we demonstrate that at a preconcentration time of 5 min the cysteine-modified electrode has a dynamic range of 2 orders of magnitude (from 5.0 to 0.050 μg/L) and the detection limit is as low as 25 ng/L (0.39 nM). This method is applied to the determination of copper(II) in two reference materials, SLEW-2 (river water, 1.62 μg/L) and CASS-3 (seawater, 0.517 μg/L). The results agree satisfactorily with the certified values.

Analysis of Total Non-Volatile Non-Sulfide Reduced Sulfur in Potable and Untreated Surface and Groundwaters

An analytical method was developed to measure the total concentration of non-volatile non-sulfide reduced sulfur in treated and untreated surface and groundwater. The method was based on the alkaline reduction by Raney nickel (prepared in situ from Raney alloy) of organic and inorganic sulfur compounds (in oxidation states below +6) to sulfide. Sulfide was swept out of the reflux apparatus under nitrogen into a trap of zinc acetate and determined colorimetrically as ethylene blue. The recoveries obtained from solutions of elemental sulfur, sulfide, sulfite, thiosulfate, tetrathionate, cysteine, cystine, methionine, glutathione, allylthiourea, sulfanilamide and thiocyanate ranged from 84–102% with typical recoveries of approximately 90%. Sulfate was not detectable by the procedure. Chlorine present in potable water samples interfered in the procedure and was removed with sodium borohydride. The relative standard deviation of the method varied from 0.25 to 5.6% and averaged 3%. The detection limit based on a 500 mL sample was 3 mg m−3.

Novel findings on the copper catalysed oxidation of cysteine

The oxidation of cysteine (RSH) has been studied by using O2, ferricytochrome c (Cyt c) and nitro blue tetrazolium (NBT) as electron acceptors. The addition of 200μM CuII to a solution of 2mM cysteine, pH 7.4, produces an absorbance with a peak at 260 nm and a shoulder at 300 nm. Generation of a cuprous bis-cysteine complex (RS-CuI-SR) is responsible for this absorbance. In the absence of O2 the absorbance is stable for long time while in the presence of air it vanishes slowly only when the cysteine excess is consumed. The neocuproine assay and the EPR analysis show that the metal remains reduced in the course of the oxidation of cysteine returning to the oxidised form at the end of reaction when all RSH has been oxidised to RSSR. Addition of CuII enhances the reduction rate of Cyt c and of NBT by cysteine also under anaerobiosis indicating the occurrence of a direct reduction of the acceptor by the complex. It is concluded that the cuprous bis-cysteine complex (RS-CuI-SR) is the catalytic species involved in the oxidation of cysteine. The novel finding of the stability of the complex together with the metal remaining in the reduced form during the oxidation suggest sulfur as the electron donor in the place of the metal ion.

Iron Catalyzes both Decomposition and Synthesis ofS-Nitrosothiols: Optical and Electron Paramagnetic Resonance Studies

Formation ofS-nitrosothiols was demonstrated in 1–50 mmaqueous solutions of cysteine or glutathione (cys-NO or GS-NO, respectively) upon contact of thiols with gaseous nitric oxide under a pressure of 50–600 mm Hg and anaerobic conditions. The yield ofS-nitrosothiols was increased by mixing with NO plus air at a molar ratio [NO]/[O2from air] of no less than 40. In this instance, theS-nitrosothiol formation was optimum at a NO pressure of 100–150 mm Hg. The addition of 0.25 mmo-phenanthroline, a selective Fe2+chelator, to thiol solutions prior to the treatment with NO or NO + air completely blocked the formation ofS-nitrosothiols. On the other hand, this process was potentiated by the addition of Fe2+but not Cu2+ions. These data indicated a crucial influence of Fe2+on the process. The contact ofo-phenanthroline withS-nitrosothiols synthesized by a routine method (treatment of thiol solutions with the NO + NO2mixture at pH <1) did not induce their degradation at pH 3–10. Moreover,o-phenanthroline strikingly enhanced the cys-NO stability at neutral pH. Cysteine, glutathione, and desferal, a selective Fe3+chelator, exerted a similar effect on cys-NO. The stabilizing effect of thiols on cys-NO was accompanied by the formation of dinitrosyl–iron complexes with thiol-containing ligands containing admixed (intrinsic) iron (1–2 μm). The addition of Fe2+at a concentration higher than 10 μmabolished the stabilizing effect of thiols on cys-NO. Therefore iron can induce both degradation and synthesis ofS-nitrosothiols. According to the proposed mechanisms such opposite effects of iron onS-nitrosothiols are determined by the ratio betweenS-nitrosothiols, thiols, iron, and NO in the reaction system.

184 Pentafuside (T-20), a novel inhibitor of HIV-1 fusion: Pharmacokinetics in rodents, monkeys and man: T. Venetta, B. DiMassimo, M.R. Johnson, D.M. Lambert, M.A. Recny, S. Hopkins and M. Saag* Trimeris, Inc., P. O. Box 13963, Research Triangle Park, NC 27709 *AIDS Outpatient Clinic, University of Alabama at Birmingham, Birmingham, Alabama 35294

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.

Positron lifetime study of several chiral materials in aqueous solution

The most obvious symmetry breaking in Nature is the left-right asymmetry of living beings: sugars and amino acids are almost exclusively represented by one of their stereoisomers (D-isomer for sugars and L-isomer for amino acids) at the expense of other possible isomers. In our experiment we studied the aqueous solutions of tartaric acid, alanine, and cysteine in the function of temperature by positron lifetime spectroscopy. The results were compared with those obtained in pure water under similar conditions. We always observed a sharp minimum of the positron lifetime at around 41 °C in water and in the solutions of the natural stereo-isomers. On the other hand, the same minimum occurred at considerably lower temperatures in the solutions of the “unnatural” isomers.

Covalent HLA-B27/peptide complex induced by specific recognition of an aziridine mimic of arginine.

The class I major histocompatibility complex (MHC) glycoprotein HLA-B27 binds short peptides containing arginine at peptide position 2 (P2). The HLA-B27/peptide complex is recognized by T cells both as part of the development of the repertoire of T cells in the cellular immune system and during activation of cytotoxic T cells. Based on the three-dimensional structure of HLA-B27, we have synthesized a ligand with an aziridine-containing side chain designed to mimic arginine and to bind covalently in the arginine-specific P2 pocket of HLA-B27. Using tryptic digestion followed by mass spectrometry and amino acid sequencing, the aziridine-containing ligand is shown to alkylate specifically cysteine 67 of HLA-B27. Neither free cysteine in solution nor an exposed cysteine on a class II MHC molecule can be alkylated, showing that specific recognition between the anchor side-chain pocket of an MHC class I protein and the designed ligand (propinquity) is necessary to induce the selective covalent reaction with the MHC class I molecule.

Protection against heavy metal toxicity by mucus and scales in fish.

Fingerlings of three freshwater fish showed differences in susceptibility to lethality of 250 mg/L lead suspension or lead nitrate solution in water. Among these, the largemouth bass (Micropterus salmoides) was more tolerant than green sunfish (Lepomis cyanellus) and goldfish (Carassius auratus). The addition of mucus from largemouth bass, when added to jars containing lead, increased the LT-50 value (time to kill 50% of fingerling exposed to 250 mg/L lead) in green sunfish and goldfish. However, adding scales, especially if the scales were treated with an alkaline solution of cysteine and glycine, made all of these species tolerant to otherwise lethal concentrations of lead or mercury. The scales buffered the pH of lead nitrate solution as well as removed lead (and mercury) from water (by settling down at the bottom after sequestering lead). Scales of younger fingerlings of largemouth bass were more efficient in chelating heavy metals than those of older ones.

Measurement of the reactive and available solid-supported carboxylic, N-hydroxysuccinylated carboxylic, and aldehydo groups

We describe new colorimetric methods for the determination of the reactive and available solid-supported carboxylic,N-hydroxysuc cinylated carboxylic, and aldehydo groups under conditions usually applied for the coupling of biomolecules. The methods involve the reaction of the solid-supported functional groups with tyramine or cysteine, and the subsequent titration of the ligand coupled onto the solid supports using the commercially available bicinchoninic acid/copper protein assay reagent (BCA). The titration is based on the ability of these ligands to reduce Cu2+ to Cu+, which forms a chelate complex with bicinchoninic acid absorbing at 562 nm. The quantita tion is finally carried out through standard curves obtained using tyramine or cysteine solutions of known concentrations. The values obtained by the assays developed for several solid supports carrying carboxylic, NHS-ester, and aldehydo groups were well correlated with those obtained by other literature methods or provided by the manu facturers. All of the proposed methods are simple, more sensitive than other relevant literature methods, and require only commericially available reagents.

Evaluation of the Key Odorants in a Thermally Treated Solution of Ribose and Cysteine by Aroma Extract Dilution Techniques

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvaluation of the Key Odorants in a Thermally Treated Solution of Ribose and Cysteine by Aroma Extract Dilution TechniquesThomas Hofmann and Peter SchieberleCite this: J. Agric. Food Chem. 1995, 43, 8, 2187–2194Publication Date (Print):August 1, 1995Publication History Published online1 May 2002Published inissue 1 August 1995https://doi.org/10.1021/jf00056a042RIGHTS & PERMISSIONSArticle Views1415Altmetric-Citations130LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (975 KB) Get e-Alerts Get e-Alerts

Alleviation of browning in oak explants by chemical pretreatments

Meristems from 25–90-year-old oak (Quercus robur L. andQ. petraea Matt.) trees and seed embryos were pretreated with polyvinyl pyrrolidone, ascorbic acid, cysteine and citric acid solutions. Tissues were cultured mostly on a WPM medium supplemented with different combinations and concentrations of growth regulators. All the different pretreatments showed a positive effect against the otherwise very rapid and harmful browning of the explants but ascorbic acid (100 mg dm−3) proved to be the most effective. Shooting was induced from seed embryos and meristems originating from adult trees. Rooted plantlets were obtained from explants of seed embryos.

COMBINED EFFECTS IN PREVENTING ENZYMATIC BROWNING REACTIONS IN MINIMALLY PROCESSED FRUIT

ABSTRACTFresh sliced apples were dipped in ethanol or cysteine solutions and/or packaged in air or modified atmosphere in order to retard oxidative browning. Modified atmosphere packaging was effective in inhibiting darkening for at least nine days at refrigerated storage conditions. The combination ethanol dip/modified atmosphere packaging resulted as a suitable method in maintaining the original color in apple slices even after exposure to air.

Radiation induced oxidation of sulphydryl molecules in aqueous solutions. A comprehensive review

Radiation degradation studies of thiols in aqueous solutions under variety of conditions during the past more than three decades are reviewed. Radiolytic mechanism of γ-irradiated air free, air and N 2O-saturated solutions of cysteine, cysteamine, dithiothreitol, mercaptoethanol, glutathione and papain are high lighted. A large variety of thiols repair organic radicals by H atom transfer from SH group. The repair rate constants are found to be between 5 × 10 6M -1s -1 to 4.0 × 10 8M -1s -1. The data are tabulated. The rate constants of e - aq and ȮH radicals with variety of thiols evaluated by pulse radioanalysis and flash photolysis are found to be very high and are computed. Sulphur centered radicals e.g. RṠ;, RSSR ⨪ generated in the pulse radioanalysis of thiols are very important species. Their reactions with oxygen and other compounds are of relevance to radiation biology. The results, reaction mechanism, the repair rate constant, the rate constants of e - aq and ȮH radicals with thiols and the rate constants of sulphur centered radicals with oxygen and other compounds of biological interest can be of great use in the interpretation of the mechanism of the protection of cells, animals, DNA and other biological molecules and may well provide basic essential information for the understanding of radiation biology. The protection of biological target at chemical level is generally understood in terms of protecting compounds participating directly in the radiochemical event and reducing the damage to biological target. The damage to the biological target is repaired by the hydrogen transfer from the thiol. Biochemical and metabolic mechanisms are quite complex. There is no single mechanism which explains all the experimental observations on the metabolism of thiols. More work needs to be done in order to understand the metabolic aspect of the protection mechanism.

Colorimetric determination of reactive solid-supported primary and secondary amino groups

A simple and sensitive method for the quantitative determination of solid-supported primary and/or secondary amino groups using commercially available reagents is described. The solid supports are treated in an aqueous environment with either 2-iminothiolane (ITL) or sulpho-succinimidyl-3-(4-hydroxyphenyl) propionate (sulpho-SHPP), which introduce one sulphydryl or one hydroxyphenyl group per amino group reacted, respectively. These groups are capable of reducing Cu 2+ to Cu + in alkaline medium. Thus, after removal of the excess reagents through washing, subsequent incubation of the solids with 2,2′-bicinchoninic acid (BCA) copper protein reagent results in production of Cu + in the solution, which forms a chelate complex with BCA absorbing at 562 nm. The quantitation of the groups introduced on the surfaces, and therefore of the reacted amino groups, is carried out through standard curves of cysteine solutions for ITL, or tyrosine solutions for sulpho-SHPP-treated solids. Using ITL, only the primary amino groups are determined, whereas sulpho-SHPP provided the primary and secondary reactive amino groups. The method is versatile and can be used for the estimation of amino groups onto several biomedical solid matrices, and should provide useful information for the covalent immobilization of ligands (e.g. drugs, antibodies).

An Amplified Assay for Thiols Based on Reactivation of Papain

A sensitive spectrophotometric assay has been developed for thiol (sulfhydryl) groups using an inactive di-sulfide derivative of papain (papain-S-SCH3). The thiol-disulfide interchange reaction of a thiol with papain-S-SCH3 results in the stoichiometric formation of active papain (papain-SH). The reactivated papain catalyzes the hydrolysis of a chromogenic substrate, resulting in an amplified spectrophotometric signal proportional to the initial amount of thiol. A variety of thiols, e.g., cysteine, glutathione, penicillamine, cysteine methyl ester, and cysteamine, yield similar linear plots for the activity of papain vs the initial amount of thiol. An unknown concentration of a thiol is measured using a standard plot for the activity of papain vs the amount of thiol, obtained for the same thiol or for a similar thiol. Thiol groups on proteins and thiol groups of high values of pKa(2-mercaptoethanol, 3-mercaptopropanoic acid) can also be assayed using papain-S-SCH3 in the presence of excess cystamine. The assay is about 100-fold more sensitive than that using Ellman′s reagent [5,5′-dithiobis(2-nitrobenzoic acid)]. A 0.4 μM solution of cysteine produces an absorbance change of 0.55 at 410 nm after 30 mm in the assay, compared to a predicted change in absorbance of 0.0054 using Ellman′s assay.

Rapid determination of inorganic and methyl mercury in fish

A method has been developed that uses a mixed solution of NaOH, NaCl and cysteine to digest fish. Inorganic Hg and MgHg were determined by cold vapor atomic absorption (CVAAS) using a selective reduction step with SnCl2 and SnCL2-solutions. Ethyl alcohol was satisfactorily used to prevent excessive foaming. Two optimum digestion procedures were established: (1) using a dry block heater at 90 °C for 1 hr and (2) overnight digestion at 25 to 30 °C. Differences between both were not significant (95%) in the range of 30 to 500 ng g−1 Hg (II) and MeHg in fish. Reduction of the Hg signal due to matrix effects in different fish species was evaluated (95 to 60%). Oily fish, shrimp and lobsters gave the highest reduction. Internal calibration by addition of Hg standards are strongly recommended when exact determinations are needed. The detection limit obtained was near 10 ng g−1. Signals were linear in the concentration range studied (30 to 500 ng g−1). Accuracy of analyses was in the order of 5% or better, with a relative standard deviation of 5%. The method could be applied to other environmental matrices: hair, urine and blood, with some modifications.

Stability of aqueous cysteine solutions for TPN

Stability of aqueous cysteine solutions for TPN

Capillary electrophoresis of macromolecules in 'syrupy' solutions: facts and misfacts.

'Syrupy' solutions of liquid linear polyacrylamide (> or = 10%T, 0%C) appear to be excellent for fractionation of oligonucleotides and, potentially, for DNA sequencing. For such analyses, the silica wall must be coated by covalently bound strings of polyacrylamide; otherwise, the electroosmotic flow will slowly pump out the viscous electrolyte solution. Due to the enormous viscosity (100 Pa s for an 8% T solution) the polymer strings must be prepared in situ, by filling the capillary with the appropriate monomer solution. The reaction, however, cannot be driven to better than 80-85% conversion: in 10%T, the concentration of unreacted monomers will thus be 200-300 mM. This will give a substantial background absorbance (even at 254 nm) and leave a huge amount of potentially harmful reacting species in the background electrolyte. A chemical scavenging method is proposed here: after polymerization, a 100 mM solution of cysteine is driven in from the cathode and allowed to react for up to 10 h. At the end of the reaction period, the excess cysteine and its acrylamido adduct are driven out electrophoretically and the column is reconstituted with its normal background electrolyte. Columns thus preconditioned have been found to perform extremely well and to last as long as the inner coating (and the linear polymer filling) will last. No 'carry over' from run to run was experienced.

Role of Sulfhydryl-Containing Agents in the Healing of Erosive Gastritis and Chronic Gastric Ulceration in the Rat

One milliliter of 1, 2, or 5% DL-cysteine (cysteine) or DL-methionine methylsulfonium chloride (MMSC) was instilled into the rat stomach 1, 24, and 48 h after giving ethanol (1 mL of 40% solution) by gavage. One hour following the administration of ethanol, gastric mucosal injury was seen in all the animals (22.6 ± 1.1 mm2, mean ± SEM; n = 10). Twenty-four hours after giving the ethanol, all the rats treated with cysteine or MMSC still had the mucosal injury. Treatment with 2% cysteine or MMSC significantly (p < 0.01) reduced the extent of this injury (10.2 ± 0.6 and 10.1 ± 0.5 mm2, respectively, versus 20.7 ± 1.2 mm2, mean ± SEM; n = 10), an action that was similarly achieved by the 5% solutions (10.1 ±0.5 and 9.9 ± 0.3 mm2, respectively, versus 20.7 ± 1.2 mm2, mean ± SEM; n = 10). Forty-eight hours following the administration of ethanol, 30% of the animals given 1% cysteine or MMSC still had gastric mucosal injury, which was significantly (p < 0.001) less extensive than that seen with ethanol alone (3.8 ± 0.3 and 4.1 ± 0.3 mm2, respectively, versus 13.1 ± 0.8 mm2, mean ± SEM; n = 10). At this time period, however, none of the animals treated with 2 or 5% solutions of cysteine or MMSC still had any injury. Healing of the ethanol-induced injury was confirmed microscopically and was achieved by regeneration. Chronic gastric ulceration was produced in the rat by administering 5 mg/kg of reserpine ip every day for 5 days, then housing the animals for 2 weeks. Cysteine and MMSC (1 mL by gavage daily) demonstrated a dose-dependent and time-related power to stimulate the healing of this ulceration. After gavaging for 5 days, 80% of the rats given 1% cysteine and 70% of those given 1% MMSC had gastric ulceration, whereas only 20% of the animals given 10% solutions had the ulceration. After gavaging for 10 days, 20% of the rats given 1% cysteine and 30% of those given 1% MMSC had gastric ulceration, whereas none gavaged with 5 or 10% solutions of these agents still had any ulceration. At this stage, 70% of the animals gavaged with distilled water still had the ulceration. These cysteine and MMSC actions were independent of any effect on the gastric acid secretion. The results show that sulfhydryl-containing agents stimulate the healing of ethanol-induced acute gastric mucosal injury and chronic gastric ulceration in the rat.