The radiation chemistry of cysteamine and of cysteamine-S- phosphoric acid in oxygen-free and oxygenated solution has been studied at acidic and near-neutral pH. In oxygen-free solution and in oxygenated solution above pH 5 the mechanism of cysteamine radiolysis appears similar to that of cysteine. From measurements of the dependence of G(-RSH), G(RSSR), and G(H2O2) upon pH and cysteamine concentration, suggestions regarding the stoichiometry of the chain reaction occurring at higher pH and the mechanistic implications have been made. The dependence of the rate of oxidation of cysteamine by hydrogen peroxide upon pH has been studied, second-order kinetics being observed over the pH range 6.5 to 10.9, and the rate has been found to depend in a simple manner upon ionisation of the thiol. The rate constant of the reaction of aquated electrons with cysteamine-S-phosphoric acid has been measured as about 5 x 109 M-1 sec-1 by competition with cysteamine at pH 4.2, and measurements have indicated the formation of orthophosphate, inorganic phosphorothioate, and an aldehyde as products of the reaction of hydroxyl radicals with cysteamine-S-phosphoric acid at pH 8.6.
| Identifer | oai:union.ndltd.org:ADTP/247177 |
| Date | January 1972 |
| Creators | Sims, Ritchie John |
| Publisher | ResearchSpace@Auckland |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated., http://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm, Copyright: The author |
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