Theoretical Study Of Biological Small Molecule Multi-channel Proton Transfer

As one of the simplest and the most fundamental phenomena in the tautomeric equilibria and oxidation-reduction reactions, proton transfers paly an important role either in chemical or biochemical processes. Elements within and between proton transfer widespread elements in photosynthesis chain, respiratory chain, enzymatic catalysis response of the cell metabolism process, a driving force behind cell procedures and biological information to energy quantum coding and transmission model.Many studies have been performed on proton transfer reactions as its important role both in chemical and biological process. In this paper we study proton transfer reaction use the analysis of the vibrational model and the vibrational frequencies, and the theory of multi-channel reaction also be used in the study.In our study, we choose serinamide and cytosine as the model of peptide. The useful DFT methods are used in the study of multi-channel reaction of proton transfer. The effect of envirionment are discussed and some important results have been dbtained.In chapter three, we have studied the multi-channel reaction of serinamide. Ten stable conformer have been computed, which there are two pairs of mirror-image conformers. Each conformer has five channels to complete the proton transfers. When we validate the validity of these transition states by the IRC, one of them is proved to be not in existence. By comparing the activation energies, Gibbs free energy changes and the equilibrium constants we conclude which one is the main channel, and which one is the most unfavorable channel.As the model of tautomcric equilibria of pcptidc. the effect of water is can not be neglected. So we introduce a water molecule in different place in the proton transfer process of serinamide. We conclude that not all the water can facilitate the transfer process. Only when the water molecule serves as a bridge that connects the donor and acceptor sites, it can facilitate the reaction. The effect of the water molecule which only servers as H-bond acceptor or donor is not so obviously.The water molecule can surely affect the tautomeric equilibria of peptide, we have just discussed that in chapter four, and the effect of other peptide unit also can not be neglected. So in chaper five we choose cytosine peptide model and formamide as peptide unit mdel to study the effect of water molecule and peptide unit to the tautomeric equilibria process.