Spectroscopic characterization of mechanisms of oxidation of Phe by SO4- radical: A pulse radiolysis study |
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Authors: | Gaosheng Chu Shujuan Zhang Side Yao Zhenhui Han Zhiwen Du Zhicheng Zhang |
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Affiliation: | (1) Department of Applied Chemistry, University of Science and Technology of China, 230026 Hefei, China;(2) Laboratory of Radiation Chemistry, Shanghai Institute of Nuclear Research, Chinese Academy of Sciences, 201800 Shanghai, China |
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Abstract: | By using time-resolved kinetic spectrophotometry and pulse radiolysis technique, the oxidation of Phe by SO4 - radical has been investigated both in aqueous and water/acetonitrile mixed solutions. The results reveal that attack of the oxidizing SO4 - radical on Phe leads directly to the formation of Phe cation radical 3 with a strong absorption peak at 310 nm, then it proceeds in three competitive reactions via either hydroxylation, deprotonation or decarboxylation, which were found to be strongly dependent upon the ionization state of the substitutes —COOH and —NH2 and the nature of the solvents. Decarboxylation takes place only when the carboxyl group is deprotonated. At high pH deprotonation of Phe cation radical 3 is much easier to occur than that in neutral or acid solutions. Moreover, with addition of acetonitrile, deprotonation is more predominant than hydroxylation, whereas in aqueous solutions hydroxylation is much easier to occur. |
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Keywords: | Phe pulse radiolysis SO4 - radical oxidation mechanism |
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