Reactions Of Thiyl Radicals Research Articles

Rate Constant Determination for the Reaction of Hydroxyl and Glutathione Thiyl Radicals with Glutathione in Aqueous Solution

The techniques of pulse radiolysis, laser photolysis, and absorption spectroscopy have been used to investigate the glutathione disulfide radical anion formation over the pH range 7.0−13.0 in aqueous solution. Photolysis of the disulfide anion formed from the one-electron oxidation of reduced glutathione perturbs the disulfide anion/thiyl radical equilibrium, allowing the rate constant for thiyl radical reaction with glutathione to be uniquely determined from the transient absorption bleach and subsequent pseudo-first-order recovery. These pH-dependent values were combined with measured disulfide equilibrium constants to calculate glutathione radical anion dissociation rate constants. From computer modeling of established mechanisms of the observed disulfide radical anion growths, pH-dependent rate constants for the reaction of hydroxyl radicals with glutathione to produce the thiyl radical were obtained. Utilizing literature ionization constants, values for hydroxyl and thiyl radical reactions with indiv...

ChemInform Abstract: Fflash Photolysis Study for Reversible Addition Reactions of Thiyl Radicals with Olefins and Acetylenes

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Flash Photolysis Study on Reversible Addition Reactions of Thiyl Radicals

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Flash photolysis study on reversible addition reactions of thiyl radicals

Obtaining the rate constants in the absolute values affords many advantages compared with the relative rates. It had been believed that the absolute values obtained by the flash photolysis method were not precise enough to examine substituent effects such as the Hammett equation. In this review, however, one can recognize that we can examine substituent effects and solvent effects with the absolute rate constants obtained by the flash photolysis. Especially, comparison among the reactivities of different attacking radicals becomes possible with measurements of the absolute rate constants.

Radiation Chemistry Applied to Drug Design

Radiation chemistry can contribute to drug design by quantifying redox properties of drugs (useful parameters in quantitative structure-activity relationships), and where free radicals are suspected intermediates in drug action, radiation can be used to generate these putative species and help characterize relevant reactions. Steady radiolysis produces radicals at a readily-varied but quantified rate; pulse radiolysis with fast spectrophotometric and/or conductimetric detection enables the kinetic properties of radicals to be monitored directly. Using these methods, radical intermediates from drugs with specific cytotoxicity towards hypoxic cells have been shown to react rapidly with oxygen, a reaction probably responsible for the therapeutic differential. Radical oxidants from activated neutrophils include superoxide and hydroxyl radicals, and radiation-chemical methods have an important role to play in rational drug design to exploit such oxidative chemistry. Antioxidants can also be evaluated quantitatively by radiolysis methods; the conjugation reactions of thiyl radicals with thiolate and oxygen are now recognised to be major contributions of pulse radiolysis to thiol biochemistry.

Reactions of thiyl radicals with transition-metal complexes

Reactions of thiyl radicals (RS . ) were studied in aqueous solution by laser flash photolysis. Alkyl radicals, which were used to generate the thiyl radicals, were produced by the photohomolysis of the cobalt-carbon bond of RCo([14]aneN 4 )(H 2 O) 2+ complexes (R=CH 3 , C 2 H 5 ). These carbon-centered radicals abstract hydrogen atoms from thiols (C 2 H 5 SH, CysSH, or GSH), generating thiyl radicals. Thiyl radicals readily oxidize a variety of reduced transition-metal complexes

Kinetics of formation and reactions of thiyl radicals in aqueous solution

Very few kinetic data are available that describe reactions of sulfur-centered radicals, despite their importance in biological systems. Thiyl radicals may be produced by generating carbon-centered radicals using visible laser flash photolysis and taking advantage of the repair reaction. Thiyl radicals are difficult to detect directly and require the use of a kinetic probe such as ABTS{sup 2{minus}} or TMPD. Kinetic studies of these reactions as well as reactions of ethanethiyl radicals with hexaaqua complexes of chromium(II), vanadium(II), and iron(II) are described.

High Temperature Reactions of Thiyl Radicals

Abstract Some results of the examination of the reactivity of thiyl radicals in thermal processes, which allow the synthesis of organic compounds of sulfur other types of compounds, have been summarized for the first time.

ChemInform Abstract: Thermal Reactions of Thiyl Radicals

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Reaction of thiyl radicals with alcohols, ethers and polyunsaturated fatty acids: A possible role of thiyl free radicals in thiol mutagenesis?

Possible reactions of thiyl free radicals in biological environment are reviewed. In particular hydrogen transfer processes from model C-H compounds like alcohols and ethers as well as from polyunsaturated fatty acids to thiyl radicals are described to proceed with reasonably high rate constants (10(3)-10(4) and 10(6)-10(7) M-1 s-1, respectively). Thiyl radicals have thus to be considered as potentially hazardous species especially with respect to DNA damage and lipid peroxidation.

Reactions of thiyl radicals with phenothiazines and other antioxidants in aqueous solutions. A pulse radiolysis study

Reaction rate constants of thiyl radicals with phenothiazines, promethazine (PMZ), chlorpromazine (CPZ), prochlorperazine (PPZ), trimeperazine tarterate (TPZ), and other antioxidants, e.g., ascorbic acid and 2,2-azinobis(3-ethyl benzthiazoline-6 sulphonate) (ABTS) have been estimated using pulse radiolysis technique. In general they are quite high (108–109 M−1 s−1). The k values for cysteine, cysteamine, mercaptoethanol, and mercaptopropionic acid with similar structures and molecular weights are more or less similar for PMZ, CPZ, and PPZ.Rate constants are lower in value for [Formula: see text] radicals of phenothiazines showing that they are dependent upon the structure and the molecular weight of the compound.Rate constants are the same whether the thiyl radicals are generated from thiols or their corresponding disulphides. The k values for chlorine-containing phenothiazines, chlorpromazine, and prochlorperazine are higher than those of promothazine Keywords: pulse radiolysis, thiyl radicals, phenothiazines, ABTS, ascorbic acid.

The Formation and Structure of the Sulfoxyl Radicals RSO·, RSOO·, RSO2·, and RSO2OO· from the Reaction of Cysteine, Glutathione and Penicillamine Thiyl Radicals with Molecular Oxygen

This work reports an electron spin resonance study of the reactions of cysteine, glutathione and penicillamine thiyl radicals with molecular oxygen in frozen aqueous solutions at low temperatures. For all three thiols, the thiyl radical, RS., is found to react with oxygen to form the thiol peroxyl radical, RSOO(.). On the absorption of visible light, RSOO(.) photoisomerizes to the sulfonyl radical, RSO2(.), which subsequently reacts with molecular oxygen to form RSO2OO(.), the sulfonyl peroxyl radical. The identities of the sulfonyl and sulfonyl peroxyl radicals were confirmed by their production by a different route, from sulfinic acid. Sulfinyl radicals, RSO(.), are found as the final radical species in the reactions of thiyl radicals and oxygen. Parallel 17O hyperfine couplings (A parallel) are reported for each sulfoxyl radical and a correlation between the spin density on oxygen and the reactivity of the radical is suggested. As a result of this correlation sulfonyl peroxyl radicals are predicted to be far more reactive than thiol peroxyl radicals. We also report molecular orbital calculations on the nature of the spin density distribution and the molecular geometry of the model radicals CH3SO2(.) and CH3SO2OO(.).

Glutathione-dependent reduction of peroxides during ferryl- and met-myoglobin interconversion: A potential protective mechanism in muscle

Met-myoglobin is oxidized both by H 2O 2 and other hydroperoxides to a species with a higher iron valency state and the spectral characteristics of ferryl-myoglobin. Glutathione (GSH) reduces the latter species back to met-myoglobin with parallel oxidation to its disulfide (GSSG) but cannot reduce met-myoglobin to ferrous myoglobin. Under aerobic conditions, the GSH-mediated reduction of ferryl-myoglobin is associated with O 2 consumption and amounts of GSSG are formed far in excess over that of the peroxide added. Under anaerobic conditions, this ratio is close to unity. These results are interpreted in terms of a one-electron redox process involving the reduction of ferryl-myoglobin to met-myoglobin and the one-electron oxidation of GSH to its thiyl radical. Further reactions of thiyl radicals are influenced by the presence of oxygen which will be the determining factor in the ratio H 2O 2 added/GSSG formed. It is suggested that, when oxygen is limiting, myoglobin may serve as a protector of muscle cells against peroxides and other oxidants.

Reduction potentials and exchange reactions of thiyl radicals and disulfide anion radicals

Reduction potentials and exchange reactions of thiyl radicals and disulfide anion radicals

Sulfinyl radical formation from the reaction of cysteine and glutathione thiyl radicals with molecular oxygen

Using Electron Spin Resonance spectroscopy at low temperatures, we find that thiyl radicals resulting from irradiation of frozen aqueous solutions of a variety of thiols, including cysteine, glutathione, and penicillamine react with oxygen to form sulfinyl (RSO.) radicals. The identity of the cysteine sulfinyl radical has been confirmed by the use of molecular oxygen isotopically labeled with 17O. Previous workers have suggested the reaction of thiyl radicals and molecular oxygen resulted in the formation of the potentially damaging thiol peroxyl radical, RSOO.; our work shows no evidence for this species. The sulfinyl radicals are suggested to result from a direct reaction between thiyl radicals and molecular oxygen. This reaction results in the cleavage of the dioxygen bond.

ChemInform Abstract: ADDUCT FORMATION AND ABSOLUTE RATE CONSTANTS IN THE DISPLACEMENT REACTION OF THIYL RADICALS WITH DISULFIDES

Chemischer InformationsdienstVolume 16, Issue 16 Preparative Organic Chemistry ChemInform Abstract: ADDUCT FORMATION AND ABSOLUTE RATE CONSTANTS IN THE DISPLACEMENT REACTION OF THIYL RADICALS WITH DISULFIDES M. BONIFACIC, Search for more papers by this authorK.-D. ASMUS, Search for more papers by this author M. BONIFACIC, Search for more papers by this authorK.-D. ASMUS, Search for more papers by this author First published: April 23, 1985 https://doi.org/10.1002/chin.198516132Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume16, Issue16April 23, 1985 RelatedInformation

Adduct formation and absolute rate constants in the displacement reaction of thiyl radicals with disulfides

Adduct formation and absolute rate constants in the displacement reaction of thiyl radicals with disulfides

Stabilization and photochemical reactions of thiyl radicals in glassy matrices at 77 k

The possibility of stabilization of thiyl radicals formed during the photolysis of thiol solutions at a wavelength λ = 253.7 nm in glassy matrices at 77 K was shown by means of electron spin resonance and UV spectroscopy. The main alternative process is the formation of adducts RSS(H)R (R  CH 3, C 2H 5, i-C 3H 7, tert-C 4H 9) in thiol self-associate. Stabilized alkyl-thiyl radicals are able to enter into photochemical reactions leading to C—C or C—H bond rupture in the position β to the sulphur atom. The ability of stabilized thiyl radicals to enter into photochemical reactions is suggested as the reason for their low concentrations in dilute thiol solutions in alcohol and hydrocarbon matrices subjected to photolysis at λ = 253.7 nm at 77 K.

Kinetic study for spin-trapping reactions of thiyl radicals with nitroso compounds

Kinetic study for spin-trapping reactions of thiyl radicals with nitroso compounds

Flash photolysis study of solvent effects in addition reactions of thiyl radicals to styrene or .alpha.-methylstyrene. Interaction between p-chlorobenzenethiyl radical and methylbenzenes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFlash photolysis study of solvent effects in addition reactions of thiyl radicals to styrene or .alpha.-methylstyrene. Interaction between p-chlorobenzenethiyl radical and methylbenzenesOsamu Ito and Minoru MatsudaCite this: J. Phys. Chem. 1982, 86, 11, 2076–2078Publication Date (Print):May 1, 1982Publication History Published online1 May 2002Published inissue 1 May 1982https://doi.org/10.1021/j100208a034RIGHTS & PERMISSIONSArticle Views118Altmetric-Citations11LEARN 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 (369 KB) Get e-Alerts