核酸前体及其修饰结构的电子转移机理研究

Study on Electron Transfer Mechanism of Nucleic Acid Precursors and Their Modified Structure

应用荧光淬灭和激光光解瞬态吸收光谱技术研究了一系列核酸前体(核酸碱基、核苷及其结构修饰物)、小牛胸腺ctDNA与各种荧光探针及蛋白酶之间的瞬态、稳态电子转移作用机理.测定结果表明,它们的稳态、静态荧光淬灭作用很强,很好地符合Stern-Volmer线性方程,淬灭速率常数,kq(s)和kq(d),达1010@M-1S-,属于扩散控制,表明核酸前体的基态可作为电子受体或给体而分别与含色氨酸残基的蛋白酶、受电子型荧光探针之间发生具有电子转移性质的相互作用.对鸟嘌呤的结构修饰物进行了激光光解的瞬态吸收光谱研究,检测了几类活性中间体,论证了激发态的光致电子转移和能量转移机理.

The electron transfer mechanisms of a series of nucleic acid precursors (nucleobase, nucleotide and their modified structures) and ctDNA with protein enzymes and several fluorescence probes in both static and excited states were investigated using fluorescence quenching, transient absorption spectroscopic techniques and Rehm-Weller theory. The results indicate that their static and transient fluorescence quenching interactions are very strong. Both quenching rate constants k(q)(s) and k(q) (d) reach the magnitude of 10(10)(mol/L) (-1) . S-1, close to diffusion-controlled rate. This illustrates that the nucleic acid precursors in the ground states can behave as either electron donor or acceptor to undergo electron transfer interactions with electron-accepting fluorescence probes and tryptophan-containing scrum albumins (HAS, BSA). The transient absorption measurement by laser flash photolysis for the modified tricyclic derivatives of guanine base was carried out. Several transient intermediates were detected and the photoinduced ET and EnT mechanism was discussed.