Oxidation of amino-containing disulfides by Br/sub 2//sup -/ and OH: a pulse-radiolysis study. [1. 5 MeV electrons]
The rate constant for reaction of Br/sub 2/ radicals with dithiodipropionic acid (approx. 4.2 x 10/sup 8/ mol/sup -1/dm/sup 3/s/sup -1/) was independent of pH in the range 6.6-11.0 and was approx. 4.5 times smaller than those for the neutral dimethyl and diethyl disulfides Br/sub 2//sup -/ only reacted with the disulfides of cysteamine, cysteine, and penicillamine with an appreciable rate (> 10/sup 8/mol/sup -1/dm/sup 3/s/sup -1/) when one or both of the amino groups were unprotonated. Homocystine was less sensitive to the degree of protonation. While the reaction of Br/sub 2/ radicals with dithiodipropionic acid yielded a transient (lambda/sub max/ approx. = 450 nm) which possessed the characteristics of a disulfide cation, the amino-containing disulfides cited above produced transients which adsorbed with a lambda/sub max/ near 380 nm. The latter transients decayed by second-order kinetics over the pH range studied, and they gave no evidence of reaction with OH/sup -/. These species have been tentatively identified as perthiyl (RSS.) radicals. Hydroxyl radicals produced composite spectra consisting of the 380-nm species and other transients which absorbed below 350 nm. Oxidized glutathione gave only weak absorptions on reaction with Br/sub 2/ and OH radicals. The yields of sulfydryl molecules have been measured for cystine and dithiodipropionic acid. The mechanisms of radiolysis are discussed in the light of present results and earlier studies.
- Research Organization:
- Univ. of Calgary, Alberta
- OSTI ID:
- 6603457
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 85:1; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400600* -- Radiation Chemistry
AMINO ACIDS
ANIONS
BEAMS
BROMINE
CARBOXYLIC ACIDS
CHARGED PARTICLES
CHELATING AGENTS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
COMPARATIVE EVALUATIONS
CYSTEINE
DECOMPOSITION
DICARBOXYLIC ACIDS
DISULFIDES
DRUGS
ELECTRON BEAMS
ELEMENTS
ENERGY RANGE
HALOGENS
HOMOCYSTEINE
HYDROXYL RADICALS
IONS
IRRADIATION
KINETICS
LEPTON BEAMS
MEV RANGE
MEV RANGE 01-10
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PARTICLE BEAMS
PENICILLAMINE
PH VALUE
PULSED IRRADIATION
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
RADIOPROTECTIVE SUBSTANCES
REACTION KINETICS
THIOLS