Theoretical Investigation Of Proton Transfer Mechanism In The Adenine-Thymine Anion Base Pair

Based on the principle of primacy of density functional theory (DFT), the method of B3LYP/DZP++and Gaussian03application program, we calculation the proton-transfer processes of the adenine-thymine (A-T) base pair anion (AT) in gas phase. we calculated two kinds of single-proton transfer pathway respectively:A single proton transfer (SPT1) from thymine to adenine direction was obtained. However, the transition states and structure of products were not received through calculation based on collaborative double proton transfer mechanism and step double proton transfer mechanism for double proton transfer. The solvent, does not change the stability trendendy of the proton transfer reaction. In the gas phase, the reactant is more stable than product,and keep the same tendency in solvent.Using the same calculation method of (AT) to calculate the influence of metal Cu2+on proton transfer of anionic AT base pair in gas phase. Studies suggest that Metal Cu2+complexation significantly impact the proton transfer process of AT anion base pair. In condition of Cu2+complexation in O24and O28of thymine, a single proton transfer process (SPT1) occured from thymine to adenine. While in N4and N13of thymine, double proton transfer (DPT) can occur between molecules. Solvent effect play an important role for reation energy barrier of double proton transfer, and it play less effect for reation energy barrier of single proton transfer.we discuss the influecne of one and two water molecules on the proton transfer of AT anion base. If implanting O24bit in one H2O molecular, we just get the single proton transfer in the direction of SPT1. Single-proton transfer and intermolecular proton transfer would occur in the direction of SPT1, while O28bit in one H2O molecular. Adding a H2O in the N4and N13bit of adenine respectively, the single proton transfer process can occur from SPT1and adenine to thymine direction the (SPT2). When two water molecules added to the O24, O28nearby, the calculating result shows two kinds of proton transfer pathways from SPT1and DPT; Undo changes and add two H2O in the N4, N13and O28, N13bits, single-proton transfer in both directions of SPT1, and SPT2obtained, but the intermolecular proton transfer did not occur; When added two H2O in O24and N4bits, just single-proton transfer in direction of SPT1obtained, while single proton transfer and intermolecular proton transfer (DPT) in direction of SPT2did not happen.Adding a molecule of water to the N4, N13sites of adenine as well as O24, O28sites of thymine in AT anion base, we discuss the influecne of four water molecules on the proton transfer of AT anion base, and compare with the proton-transfer processes of the (AT)" in solvent. We calculated that the influecne of four water molecules on the proton transfer of (AT) is the same with (AT) in solvent.