甲醇和氨对腺嘌呤水解脱氨机理的影响(英文)

用密度泛函理论在B3LYP/6-311G(d,p)水平上研究了甲醇和氨辅助的腺嘌呤水解脱氨机理,结果表明该反应首先是在水的亲核进攻下形成一个四面体结构中间体,然后该中间体通过构象变化得到两个不同构象,从而找到两条不同反应路径.在路径a中,辅助分子参与了过渡态的形成,起到转移氢原子的作用;而在路径b中,辅助分子仅作为介质,没有参与过渡态的形成.在氨辅助的情况下,腺嘌呤在亲核反应前发生了胺-亚胺异构化,而在甲醇辅助机理中则未发生该异构化.能量结果表明甲醇辅助腺嘌呤脱氨反应具有与水辅助类似的势垒,而氨辅助反应的势垒则比水辅助的高.

Effects of CH3OH and NH3 on the Hydrolytic Deamination Mechanism of Adenine

The effects of CH3OH and NH3 on the hydrolytic deamination mechanism of adenine were studied by density functional theory at the B3LYP/6-31 IG(d,p) level. The results reveal that a tetrahedral intermediate is formed after a nucleophilic attack by a water molecule. Two intermediates are formed through conformational changes and different pathways are responsible. In pathway a, an assistant molecule takes part in the formation of the transition state and acts as a bridge to transfer a hydrogen atom, while in pathway b the assistant molecule is not involved in the creation of the transition state and acts only as a medium. The adenine takes place an amine-imine tautomerization before the nucleophilic attack under NH3, which is not the case for the methanol-assisted mechanism. Energy results indicate that the energy barrier of the methanol-assisted adenine deamination is similar to that of the water-assisted reaction while the ammonia-assisted reaction has a much higher energy barrier compared with the water-assisted reaction.