Photolysis mechanism of aqueous tryptophan
| Autor: | J. F. Baugher, L. I. Grossweiner |
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| Rok vydání: | 1977 |
| Předmět: | |
| Zdroj: | The Journal of Physical Chemistry. 81:1349-1354 |
| ISSN: | 1541-5740 0022-3654 |
| DOI: | 10.1021/j100529a002 |
| Popis: | Flash photolysis experiments indicate that monophotonic photoionization is the principal initial photolysis act in aqueous tryptophan under high intensity, 265-nm laser excitation, leading to the Trp/sup +/ radical cation (lambda/sub max/ 580 nm) with quantum yield 0.12 +- 0.01 and e/sub aq//sup -/ with quantum yield 0.10 +- 0.01 from pH 4 to 8. The neutral Trp radical (lambda/sub max/ 510 nm) is formed by deprotonation with rate constant 1.5 x 10/sup 6/ s/sup -1/. The disappearance of e/sub aq//sup -/ follows a complex decay inconsistent with homogeneous kinetics. The results are in agreement with a recombination model in which the electron diffuses through the medium as a quasi-free entity, during which period back reactions with the original radical, or electrons and radicals generated in nearby pairs, compete with scavenging by tryptophan or added solutes. The well-established result that Trp yield observed after electron decay is not enhanced by oxygen or other e/sub aq//sup -/ scavengers is attributed to the formation of an unstable intermediate product of the electron-radical back reaction which subsequently oxidizes additional tryptophan to Trp. |
| Databáze: | OpenAIRE |
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