CAJ | 학술논문

采用ONIOM(M06-2X/6-31G*:PM3)方法研究了单个鸟嘌呤-胞嘧啶(GC)碱基对和含GC碱基对的四种排序的DNA三聚体(dATGCAT, dGCGCGC, dTAGCTA, dCGGCCG)的双质子转移反应.通过分析其双质子转移方式、质子转移过程中各结构的能量和氢键变化,总结出环境因素对GC碱基对双质子转移机理的影响.气相中, dCGGCCG三聚体中发生分步双质子转移,其它四种模型中均发生协同双质子转移.分析发现质子转移方式受上下相邻碱基对的静电相互作用和质子接受位的质子亲和势影响, dATGCAT 和dGCGCGC排序有助于质子H4a转移,而dTAGCTA和dCGGCCG排序有助于质子H1转移,胞嘧啶的N3位较高的质子亲和势有助于质子H1转移.水溶剂中,上下相邻碱基对的静电相互作用被减弱,水溶剂稳定了分步转移过程中的单质子转移产物,因此分步转移机理占据优势,五种模型中均出现分步双质子转移,在此过程中能量变化趋势相似.溶剂效应有利于单质子转移,却增加了双质子转移反应的反应能.
채용ONIOM(M06-2X/6-31G*:PM3)방법연구료단개조표령-포밀정(GC)감기대화함GC감기대적사충배서적DNA삼취체(dATGCAT, dGCGCGC, dTAGCTA, dCGGCCG)적쌍질자전이반응.통과분석기쌍질자전이방식、질자전이과정중각결구적능량화경건변화,총결출배경인소대GC감기대쌍질자전이궤리적영향.기상중, dCGGCCG삼취체중발생분보쌍질자전이,기타사충모형중균발생협동쌍질자전이.분석발현질자전이방식수상하상린감기대적정전상호작용화질자접수위적질자친화세영향, dATGCAT 화dGCGCGC배서유조우질자H4a전이,이dTAGCTA화dCGGCCG배서유조우질자H1전이,포밀정적N3위교고적질자친화세유조우질자H1전이.수용제중,상하상린감기대적정전상호작용피감약,수용제은정료분보전이과정중적단질자전이산물,인차분보전이궤리점거우세,오충모형중균출현분보쌍질자전이,재차과정중능량변화추세상사.용제효응유리우단질자전이,각증가료쌍질자전이반응적반응능.
@@@@The double-proton-transfer reaction of the isolated guanine-cytosine (GC) base pair and four DNA trimers with different nucleobase sequences (dATGCAT, dGCGCGC, dTAGCTA, and dCGGCCG) are studied by quantum mechanical calculations using ONIOM(M06-2X/6-31G*:PM3). Proton-transfer patterns, energy and structural properties are analyzed to gain insight into the double-proton-transfer mechanism with consideration to environmental factors. In the gas phase, a stepwise mechanism is found for the dCGGCCG trimer, and a concerted mechanism is found in the other four models. The computational results demonstrate that electrostatic interaction of the peripheral and middle base pairs have a pronounced effect on double-proton-transfer pattern of GC base pairs. The structures with dATGCAT and dGCGCGC sequences facilitate H4a proton transfer and those with dTAGCTA and dCGGCCG sequence facilitate H1 proton transfer. The high proton affinity of cytosine at N3 facilitates H1 proton transfer. In aqueous solution, electrostatic interactions are reduced and the products of single-proton-transfer in the stepwise mechanism are stabilized. This results in a stepwise transfer pattern becoming favorable. Solvent effects favor the single-proton-transfer reaction more than gas phase conditions, but increase the reaction energy of double-proton-transfer.