Abstract:

Using B3LYP methods of density functional theory and the MP2 methods of perturbation theory, we studied conformational transition mechanism of threonine molecules and catalytic action of water molecules and hydroxyl radicals in the hydrogen transfer reaction. The results show that there are four channels in the conformational transition reaction of S-Thr to R-alloThr. There is one channel in the conformational transitions of R-allo-Thr to R-Thr and S-Thrto S-alloThr. The highest energy barriers  for the conformational transition of S-Thr to R-alloThr, R-alloThr to R-Thr and  S-Thr to S-allo Thr are 250.2,335.0,359.6 kJ/mol. Besides, the chain composed of two water molecules and the chain composed of hydroxyl radical and water molecules
have a better catalytic effect in proton migration reaction, and the highenergy barriers are reduced to 128.3,108.6 kJ/mol for the conformational transition of S-Thr to R-alloThr respectively.

Key words: chirality, threonine, density functional theory, transition state, perturbation theory