Direct observation of NH2* reactions with oxygen, amino acids, and melanins |
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Authors: | Clarke K Edge R Johnson V Land E J Navaratnam S Truscott T G |
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Affiliation: | Chemistry Section, School of Physical and Geographical Sciences, Keele University, Staffs ST5 5BG, UK. |
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Abstract: | We report the direct observation of the quenching of the weakly absorbing transient due to the amino radical by oxygen and, hence determine, by a totally direct method, the corresponding rate constant (k = (1.1 +/- 0.1) x 10(9) dm3 mol(-1) s(-1)). We also report the rate constants for the reactions of the amino radical with several amino acids and models of black eumelanin and blond/red phaeomelanin. These reactions lead to a mechanism, based on free radicals, that can explain why ammonia is useful in commercial hair (melanin) bleaching, avoiding excessive amino acid (hair protein) damage. |
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