北京大学学报（自然科学版）

芳香氨基酸及其肽光电离、SO4·-氧化与光敏化过程的比较研究

宋钦华1,徐业平2,俞书勤2,马兴孝2   

  1. 1中国科学技术大学化学系，合肥，230026；2中国科学技术大学化学物理系，合肥，230026
  • 收稿日期:2000-07-02 出版日期:2001-03-20 发布日期:2001-03-20

Comparison of Chemical Processes of Aromatic Amino Acids and a Dipeptide Induced by UV Light and SO4·-

SONG Qinhua1, XU Yeping2, YU Shuqing2, MA Xingxiao2   

  1. 1Department of Chemistry, University of Science and Technology of China, Hefei, 230026; 2Department of Chemical Physics, University of Science and Technology of China, Hefei, 230026
  • Received:2000-07-02 Online:2001-03-20 Published:2001-03-20

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摘要： 运用激光闪光光解瞬态吸收光谱研究了色氨酸(Trp)、酪氨酸(Tyr)，苯丙氨酸(Phe)和二肽(Trp-Tyr)光电离和被SO4·-单电子氧化的过程，表征了反应过程中生成的自由基，并与丙酮光敏化生成的自由基进行了比较。三者不同之处是，Trp和Tyr光电离分别生成氮中心的吲哚自由基和酚氧自由基；丙酮光敏化除生成上述自由基外，在敏化Trp光解体系还观察到Trp激发三重态，丙酮三重态与Phe没有作用；在SO·-4单电子氧化体系，分别在Trp的吲哚环、Tyr的苯环上加成生成加成产物，其中Trp尤为显著；Phe的光电离与SO4·-氧化体系结果一致。在二肽Trp-Tyr的光电离和光敏化体系中观察到自由基的转变过程，Trp/N·-Tyr→Trp-Tyr
/O·即分子内的电子转移过程；而SO4·-单电子氧化体系没有观察到这种转变。

关键词: 光电离, 单电子氧化, 光敏化, 自由基, 电子转移, 芳香氨基酸

Abstract: The chemical processes of aromatic amino acids and a dipeptide(Trp-Tyr), which induced by UV radiation and one-electron oxidation of SO4·-, were investigated in aqueous solution by KrF(248nm)laser flash photolysis. From optical studies, the photoionization of aromatic amino acids produced radicals and hydrated electron, and the interaction of tyrosine (Tyr) and phenylalanine(Phe)with SO4·- radical yields predominantly the corresponding one-electron oxidized radicals. However, with tryptophan(Trp), it is proposed that the SO4·- radical interacts predominantly via addition reaction with the indole moiety to produce the C(2)-yl sulphate radical adduct. A intramolecular electron transfer, Trp/N·-Tyr→Trp-Tyr/O·, was observed in the process of photoionization of Trp-Tyr by 248nm light, but there was no observation in one-electron oxidation of Trp-Tyr by SO4·-.

Key words: aromatic amino acid, photoionization, one-electron oxidation, photosensitization, radical, electron transfer

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