Photosensitized splitting of cis-syn 1,3-dimethyluracil dimer by tryptophan and its peptides

Photosensitized splitting of cis-syn 1,3-dimethyluracil dimer by tryptophan (Trp) and its peptides (Trp-Tyr and Trp-Phe) is studied by fluorescence quenching experiments and irradiation experiments.It reveals that 1,3-dimethyluracil dimer is mainly split by e?-?aq resulting from two-photon ionization of Trp and its peptides under irradiation with light (λ>290 nm).Moreover,the excited singlet state of Trp and its peptides can transfer an electron to the dimer,which splits and gives two pyrimidines.In addition,because of its lower oxidative potential,the excited triplet state of Trp-Tyr can also split the dimer via transfering an electron to the dimer.     

DNA光复活过程电子转移机理的脉冲辐解研究

采用脉冲辐解瞬态吸收光谱法研究了水溶液中水合电子引发cis-syn型1,3-二甲基尿嘧啶环丁烷型二聚体(DMUD)裂解,生成嘧啶单体和嘧啶阴离子自由基,以及在维生素K3存在下,嘧啶阴离子自由基和VK3之间的电子转移反应过程,测定了电子转移反应的速率常数.当没有VK3作为电子受体时, 嘧啶阴离子自由基能继续和DMUD进行链反应.     

Photoreactivation of UV damage in culturedDrosophila cells

Summary Cell survival and photoreactivation of 254 nm ultraviolet (UV) light damage in a wild typeDrosophila cell line was assayed by colony formation in liquid medium. F_o, F_q, and extrapolation number for the exponential portion of survival curves are 21 J/m², 3.6 J/m², and 1.5 for non-photoreactivated cells and 110 J/m², 11.2 J/m², and 1.3 for those exposed to photoreactivating light. Maximal photoreactivation occurs at the 100 J/m² region of the curve. At 10 and 50% survival, 75–80% of the UV damage was photoreactivable.