氨基酸侧链与氧化鸟嘌呤碱基对体系的氢键作用

应用量子化学方法,分别在气相和水溶液中对氨基酸侧链与氧化鸟嘌呤碱基对(8-oxo-G∶C)形成的三体复合物的氢键键能、几何结构、电荷分布及二阶稳定化能进行了研究.结果表明,水溶液的存在削弱了复合物中的氢键强度,电荷分布变化明显,水溶液中形成氢键位点的电荷变化量约为气相中的10倍,而几何结构变化不明显、对于酶与DNA之间的相互作用的研究需在水溶液中进行.水溶液对带电三体复合物中8-oxo-G∶C与氨基酸侧链间的氢键有较大影响,键能平均减小了69.23 k J/mol,不带电复合物仅减小了3.60k J/mol.水溶液中三体复合物中8-oxo-G∶C间的氢键受侧链的影响不大,且与侧链带电与否无关,带电复合物和不带电复合物的氢键强度分别减小了24.57和30.05 k J/mol,且二阶稳定化能越大,其对应的氢键键长越短.

Investigation on the Hydrogen Bonding Interaction Between Amino Acid Side Chains and Base Pairs Containing Oxidized Guanine

The hydrogen bond energy, geometry, charge distribution and second order stabilization energy of complexes oxidized base pair(8-oxo-G∶C) and Amino acid side chains were investigated via quantum chemistry in gas phase and aqueous solution.The results show that the hydrogen bond strength has been weakened in aqueous solution, the charge has been obviously affected by aqueous solution, the charge variation of forming hydrogen bond sites under aqueous solution is about 10 times as much as under gas phase and the geometry has slight change.Therefore the interaction between enzyme and DNA must be studied in aqueous solution.The aqueous solution has a great influence on the hydrogen bond strength between 8-oxo-G∶C and amino acid side chains in charged complexes, which has been weakened by 69.23 kJ/mol in average.The hydrogen bond strength between 8-oxo-G∶C and amino acid side chains in uncharged complexes has only been weakened by 3.60 kJ/mol in average. The side chain with or without charge has little effect on the hydrogen bond strength between 8-oxo-G and C in complexes in aqueous solution and the hydrogen bond strengths of charged complexes and uncharged complexes have been weakened by 24.57 and 30.05 kJ/mol, respectively.The higher the second-order stabilization energy, the shorter the length of the corresponding hydrogen bonds.