⁶⁰Co γ-radiolysis of oxygenated aqueous solutions of cysteine at pH 7

Abstract

In the radiolysis of oxygenated aqueous solutions of cysteine (RSH) at p H 7, short chain reactions occur yielding cystine (RSSR) and hydrogen peroxide. Two competing reaction paths involving reaction of the thiyl radical (RS.) with oxygen or thiol anion (RS-) are postulated to explain the results.

Assessment of Damage of Glutathione by Glow Discharge Plasma at the Gas–Solution Interface through Raman Spectroscopy

“…[49] Several products are formed from radiolysis of sulfhydryl-containing chemicals, and usually, formation of disulfide bond is one of the main results. [50] Many factors including oxygen concentration, pH, and so on can affect the yield of different products. For example, G(-RSH), G(RSSR), and G(H 2 S) (yields per 100 eV) are 36.3, 15.5, and 2.35, respectively, for g-radiolysis of 3.0 Â 10 À3 M cysteine solution in the presence of 9.75 Â 10 À5 M oxygen at pH 7.0; whereas they changed to 37.1, 17.7, and 2.0, respectively, when the oxygen concentration increased to 2.2 Â 10 À4 M. [50] In another report, it was detected that almost all damaged cysteine by g-irradiation were converted to cystine at pH 3.0 in the presence of oxygen.…”

“…[50] Many factors including oxygen concentration, pH, and so on can affect the yield of different products. For example, G(-RSH), G(RSSR), and G(H 2 S) (yields per 100 eV) are 36.3, 15.5, and 2.35, respectively, for g-radiolysis of 3.0 Â 10 À3 M cysteine solution in the presence of 9.75 Â 10 À5 M oxygen at pH 7.0; whereas they changed to 37.1, 17.7, and 2.0, respectively, when the oxygen concentration increased to 2.2 Â 10 À4 M. [50] In another report, it was detected that almost all damaged cysteine by g-irradiation were converted to cystine at pH 3.0 in the presence of oxygen. [49] Similarly, the sulfhydryl group in cysteine is also susceptible to the reactive species produced by discharge plasma, as previously reported by us.…”

Protection of Post-irradiated Mice by Superoxide Dismutase

“…This post-irradiation phenomenon has been seen with membranes (Petkau and Chelack 1976), haematopoietic stem cells (Petkau, Kelly, Chelack, Pleskach, Barefoot and Meeker 1975 b) and mycoplasma (Petkau and Chelack 1974) . The effect is ostensibly due to the action of the enzyme against superoxide anions, 02 , generated from secondary sources related to chemical oxidation (Packer andWinchester 1970, Bielski andChan 1973) and metabolic reactions (Bors, Saran, Lengfelder, Spottl and Michel 1974) . These observations prompted the present study in which the enzyme was given to mice after as well as before whole-body irradiation .…”

Radiation Effects with a Model Lipid Membrane

“…Notable in this regard is the change in the erythrocyte membrane, affecting monovalent cation permeability, following the alteration of sulfhydryl groups (31). A short chain reaction has been described to account for the high rate of disappearance of sulfhydryl groups in oxygenated aqueous solutions at neutral p H (12). The fact that both 0,-and 0, are used up in the proposed reaction scheme is of additional interest because it suggests a basis for the oxygen depletion effect on survival of irradiated bacteria (32).…”

“…known to react with sulfhydryl groups, namely Ha, *OH, the hydrated electron (e,,-), and 0,- (12), only the latter two might conceivably be influenced in this manner. Since the potential of the interface nearest the bulk aqueous phase is positive (13) these radical anions may be accelerated toward the membrane, thus overcoming a limitation of diffusion-controlled reactions.…”