title: [Laser photolysis study on photo-oxidation reactions of aromatic amino acids with triplet 2-methylanthraquinone].
abstract: The transient photo-sensitive oxidation between 2-methylanthraquinone (MAQ) and aromatic amino acids (namely tryptophan, tyrosine and phenylalanine) in acetonitrile/water (1 : 1, V/V) solution was investigated by laser photolysis techniques with the excitation wavelength of 355 nm. The triplet state absorption of 2-methylanthraquinone was attributed to 390, 450 and 590 nm and the anion radical absorption of MAQ was due to 390 and 490 nm identified by the electron transfer reactions from 4-diazabicyclo [2. 2. 2] octane (DABCO) or diphenylamine (DPA) to 3MAQ*. With the decay of 3 MAQ*, the MAQ*- at 490 nm appeared, which indicated that the electron transfer reactions between 3 MAQ* and amino acids occurred. Moreover, the rate constants were deduced to be 3.0 x 10(9), 1.1 x 10(9) and 1.8 x 10(8) L x mol(-1) x s(-1) for TrpH, TyrOH and PHE, respectively. On the other hand, the free energy changes (deltaG) of the reactions showed that the proposed electron transfer steps are thermodynamically feasible.
authors.affiliation: School of Chemistry and Chemical Engineering of Hunan University of Science and Technology, Xiangtan 411201, China. caoyanyan1987@126.com
authors.forename: Xi-Yan
authors.initials: XY
authors.lastname: Cao
authors.forename: Hai-Ying
authors.initials: HY
authors.lastname: Fu
authors.forename: Li
authors.initials: L
authors.lastname: Zhu
authors.forename: Guo-Zhong
authors.initials: GZ
authors.lastname: Wu
mesh_terms: D024322:Amino Acids, Aromatic / Q000737:chemistry*; D000880:Anthraquinones / Q000737:chemistry*; D004579:Electron Transport; D007834:Lasers; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000737:chemistry; D010782:Photolysis; D014364:Tryptophan / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
chemical_list: D024322:Amino Acids, Aromatic; D000880:Anthraquinones; D014443:Tyrosine; D010649:Phenylalanine; D014364:Tryptophan; C073955:2-methylanthraquinone