芳香氨基酸及其肽光电离、SO*-4氧化与光敏化过程的比较研究

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SO· - 4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SO· - 4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SO· - 4单电子氧化体系没有观察到这种转变

Comparison of Chemical Processes of Aromatic Amino Acids and a Dipeptide Induced by UV Light and SO*-4

The chemical processes of aromatic amino acids and a dipeptide(Trp-Tyr),which induced by UV radiation and one-electron oxidation of SO*-4,were investigated in aqueous solution by KrF(248 nm)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 SO*-4 radical yields predominantly the corresponding one-electron oxidized radicals.However,with tryptophan(Trp),it is proposed that the SO*-4 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 248 nm light,but there was no observation in one-electron oxidation of Trp-Tyr by SO*-4.