Qi Shi-Fei, Wang Xiao-Nan, Yang Zhong-Zhi, Xu Xiao-Hong
School of Chemistry and Materials Science, Shanxi Normal University, Linfen 041004, People's Republic of China.
J Phys Chem B. 2009 Apr 23;113(16):5645-52. doi: 10.1021/jp811262x.
A theoretical analysis of the reactions of four N7-protonated purine bases with phenylnitrenium and 4-biphenylylnitrenium ions, both in the gas phase and in aqueous solution, is studied to elucidate the effect of protonated purines on the formation of C8 adducts in a series of complicated carcinogenic reactions. Based on this analysis, four important conclusions are drawn. (i) The mechanism of C8 adduct formation by the addition of arylnitrenium ions directly to C8 sites of nucleotide bases in DNA is still supported. (ii) The N7 protonation of purine bases will lower the rate constants of these carcinogenic reactions, which agrees with observations and proves the experimental presumption. (iii) More complicated arylnitrenium ions have more of an effect on the reduction in the rate constants of these reactions involving N7-protonated purine bases. (iv) The rate constant of the C8 deprotonation process becomes larger when N7-protonated purine bases are involved in these carcinogenic reactions.
对四种N7-质子化嘌呤碱与苯基亚硝基正离子和4-联苯基亚硝基正离子在气相和水溶液中的反应进行了理论分析，以阐明质子化嘌呤在一系列复杂致癌反应中对C8加合物形成的影响。基于此分析，得出了四个重要结论。（i）通过芳基亚硝基正离子直接加成到DNA中核苷酸碱基的C8位点上形成C8加合物的机制仍然得到支持。（ii）嘌呤碱的N7质子化将降低这些致癌反应的速率常数，这与观察结果一致并证明了实验推测。（iii）更复杂的芳基亚硝基正离子对涉及N7-质子化嘌呤碱的这些反应的速率常数降低有更大影响。（iv）当N7-质子化嘌呤碱参与这些致癌反应时，C8去质子化过程的速率常数会变大。
