Visscher K J, Spoelder H J, Loman H, Hummel A, Hom M L
Department of Biophysics, Vrije Universiteit, Amsterdam, The Netherlands.
Int J Radiat Biol. 1988 Nov;54(5):787-802. doi: 10.1080/09553008814552221.
The radical spectra of mixtures of thymidine 5'-monophosphate (TMP) or uridine 5'-monophosphate (UMP) with adenine 5'-monophosphate (AMP) after hydrated electron attack, measured from 5 to 3000 microsecond after pulse radiolysis, can only be described in terms of the radical spectra of the nucleotides if an electron transfer is taken into account from the purine radical anion to the pyrimidine, resulting in the formation of a pyrimidine radical anion. From analysis of the spectra of the dinucleoside phosphates ApU, dApT and dCpdA after eaq- attack it follows that the electron-donating species is the purine radical anion (A-.) rather than the protonated purine radical. The electron transfer competes with the fast protonation of the purine radical anion: A-. + py----A + py.- and A-. + H2O in equilibrium AH. respectively. The electron transfer is found to have a diffusion-controlled reaction rate constant of approximately 1.2 X 10(10) for TMP and 3.5 X 10(9) dm3 mol-1 s-1 for UMP.
在脉冲辐解后5至3000微秒测量的，水合电子攻击后胸苷5'-单磷酸（TMP）或尿苷5'-单磷酸（UMP）与腺嘌呤5'-单磷酸（AMP）混合物的自由基光谱，只有在考虑从嘌呤自由基阴离子到嘧啶的电子转移，从而导致嘧啶自由基阴离子形成的情况下，才能用核苷酸的自由基光谱来描述。通过对水合电子攻击后二核苷磷酸ApU、dApT和dCpdA光谱的分析可知，供电子物种是嘌呤自由基阴离子（A-·）而非质子化嘌呤自由基。电子转移与嘌呤自由基阴离子的快速质子化相互竞争：A-· + py ---- A + py-·和A-· + H₂O分别处于平衡状态AH。发现对于TMP，电子转移具有约1.2×10¹⁰的扩散控制反应速率常数，对于UMP则为3.5×10⁹ dm³ mol⁻¹ s⁻¹。
