Sulfur-centered reactive intermediates derived from the oxidation of sulfur compounds of biological interest

2001 ◽  
Vol 79 (2) ◽  
pp. 166-170 ◽  
Author(s):  
Z Abedinzadeh
Keyword(s):  
Pulse Radiolysis ◽  
Reactive Intermediates ◽  
Sulphur Compounds ◽  
Radical Species ◽  
Cation Radicals ◽  
Biological Interest ◽  
State Of Research ◽  
Oxidation Of Sulfur Compounds ◽  
Kinetics Of ◽  
Structure And Activity

Sulphur compounds play a central role in the structure and activity of many vital systems. In the living cell, sulfur constitutes an essential part of the defense against oxidative damage and is transformed into a variety of sulfur free radical species. Many studies of the chemistry of sulfur-centered radicals using pulse radiolysis and photolysis techniques to detect and measure the kinetics of these radicals have been published and reviewed. This paper discusses the present state of research on the formation and reactivity of certain sulfur-centered radicals [RS·, RSS·, RS·+, (RSSR)·+] and their implications for biological systems.Key words: sulfur-centered radicals, thiylradicals, sulfur-centered radical cation, cation radicals.

Kinetics of the Thermal Disappearance of Radicals Formed During the Radiolysis of Aspartic Acid

2009 ◽  
Vol 59 (12) ◽  
Author(s):  
Mihai Contineanu ◽  
iulia Contineanu ◽  
Ana Neacsu ◽  
Stefan Perisanu
Keyword(s):  
Thermal Resistance ◽  
Aspartic Acid ◽  
Room Temperature ◽  
Esr Spectra ◽  
Complex Mechanism ◽  
Radical Species ◽  
Mechanisms Of Formation ◽  
Kinetics Of

The radiolysis of the isomers L-, D- and DL- of the aspartic acid, in solid polycrystalline state, was investigated at room temperature. The analysis of their ESR spectra indicated the formation of at least two radicalic entities. The radical, identified as R3, resulting from the deamination of the acid, exhibits the highest concentration and thermal resistance. Possible mechanisms of formation of three radical species are suggested, based also on literature data. The kinetics of the disappearance of radical R3 indicated a complex mechanism. Three possible variants were suggested for this mechanism.

Primary products and processes in the γ-radiolysis of 2-methyltetrahydrofuran

1965 ◽  
Vol 285 (1402) ◽  
pp. 319-338 ◽  
Keyword(s):  
Glassy Phase ◽  
Kcal Mole ◽  
Radical Species ◽  
Molecule Reaction ◽  
Positive Ions ◽  
Primary Products ◽  
Diffusion Controlled ◽  
Thermal Bleaching ◽  
The Matrix ◽  
Kinetics Of

From a study of the u. v., visible, near i. r. and e. s. r. spectra induced by γ -irradiation at 77°K in glassy MTHF and in glassy MTHF containing various additives and from a study of controlled temperature increases on these spectra, the following conclusions are drawn. (1) The primary products of the radiolysis are electrons ( e - ) and positive ions ( MTHF + ) which undergo a rapid ion-molecule reaction to give O CH 3 radicals ( R ⋅). (2) e - can either be trapped in the glassy MTHF matrix or can be captured by either napththalene, ferric chloride, carbon tetrachloride, nitrous oxide or trans -stilbene if these substances are present. (3) The e - T are bleachable by light or heat and disappear independently of the radicals R⋅ without either augmentation of R⋅ or the production of any new radical species. (4) e - T and R⋅ disappear thermally and independently by second-order reactions, the rate constants being K e - + e - (M -1 S -1 ) = 10 12⋅4±1⋅1 exp ─ [0⋅85 ± 0⋅10 kcal/mole/ R ( T ─ 75)] and K R˙ + R˙ (M -1 S -1 ) = 10 13⋅3±1⋅4 exp ─ [1⋅20 ± 0⋅15 kcal/mole/ R ( T ─ 75)]. These rate expressions suggest that both reactions are diffusion controlled at low temperatures in the glassy phase. (5) The kinetics of the thermal bleaching of e - T indicate that the electrons migrate distances of about 150 Å from their parent positive ions before being trapped in the matrix. (6) The effect of FeCl 3 in reducing the formation of e - T at 77°K and its lack of effect on the thermal bleaching of e - T suggests that the reaction e - + FeCl 3 → FeCl 2 + Cl - only occurs before the electron is thermalized.

Pulse radiolysis of sulphur compounds. Part 3.—Repair by hydrogen transfer of a macromolecule irradiated in aqueous solution

1969 ◽  
Vol 65 (0) ◽  
pp. 732-742 ◽  
Author(s):  
G. E. Adams ◽  
R. C. Armstrong ◽  
A. Charlesby ◽  
B. D. Michael ◽  
R. L. Willson
Keyword(s):  
Aqueous Solution ◽  
Pulse Radiolysis ◽  
Hydrogen Transfer ◽  
Sulphur Compounds

scholarly journals Conversion of sulphur compounds into light gas oil: I. Kinetics of the conversion of model compounds

2002 ◽  
Vol 56 (2) ◽  
pp. 68-75
Author(s):  
Jasna Jankovic ◽  
Dejan Skala
Keyword(s):  
Chemical Industry ◽  
Heterocyclic Compounds ◽  
Published Data ◽  
Gas Oil ◽  
Model Compounds ◽  
Sulphur Compounds ◽  
Middle Fraction ◽  
Light Gas Oil ◽  
Reactor Calculation ◽  
Kinetics Of

The problem of sulfur compounds conversion, particularly heterocyclic compounds, from the middle fraction of crude oil (light gas oil) was analyzed and will be published in several articles in the Chemical Industry Journal. Published data in the literature, covering the conversion of tiophene, benzothiophene and dibenzothiophene are presented in the first paper of this series with the goal of comparing and critically analyzing their usage for reactor calculation.

Production de radicaux superoxydes par radiolyse pulsée de l'eau à transfert d'énergie linéique (TEL) élevé

2001 ◽  
Vol 79 (2) ◽  
pp. 180-183 ◽  
Author(s):  
G Baldacchino ◽  
V Trupin-Wasselin ◽  
S Bouffard ◽  
E Balanzat ◽  
M Gardès-Albert ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Heavy Ions ◽  
Pulse Radiolysis ◽  
Direct Methods ◽  
Superoxide Anions ◽  
Radical Species ◽  
High Let ◽  
High Linear Energy Transfer

The radiolysis of water with heavy ions of high linear energy transfer (LET) (-dE/dx) is characterized, in deaerated medium, by the production of superoxide anions, the radiolytic yields of which increase with the LET. Radiobiological interest in such radical species comes from the oxidative stress which may be generated by their dismutation in O2 and H2O2 in anoxic medium (radiotherapy with heavy ions). A brief review of the measurements of superoxide free radicals in aqueous solution by indirect or direct methods is presented. Moreover, some experimental results obtained by pulse radiolysis with Ar18+ ions (TEL = 290 keV·µm-1), are described. The interpretation of the kinetics takes into account the superoxide absorbance and that of hydrogen peroxide, which is present at the millisecond time scale.Key words: pulse radiolysis, heavy ions, superoxide radicals, high LET, kinetics.[Traduit par la Rédaction]

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