The radiolysis of cysteine in both deaerated and oxygenated solution at pH 7 has been studied. In deaerated solution the mechanism of the reaction appears to be the same as that at pH 5 - 6. The rate constant for the reaction •OH + RSH → RS• + H2O has been measured by competition with paranitrosodimethylaniline. A value of 9 x 109 was found, which though not absolutely accurate (for reasons described in the text) is sufficiently accurate to that the reaction is fast. The rate constant of the reaction eaq + RSH → R• + SH- been measured by competition with oxygen, and a value of (4.0±0.2) 4 x 109 was found. This compares well with values found by other methods. From the values of G(-RSH), G(RSSR), and G(H2O2) in oxygenated solution, and from the effects of the scavengers nitrous oxide and acetone or these values a mechanism has been proposed in which RS radicals produced by attack of primary species on cysteine propagate a chain, the rate of the propagation reaction depending on the cysteine concentration. The autoxidation of cysteine has been studied briefly, the rate being found proportional to oxygen concentration. The mechanism is believed to be the same as that for the radiolysis.
| Identifer | oai:union.ndltd.org:ADTP/247225 |
| Date | January 1968 |
| Creators | Winchester, Robert Victor |
| 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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