Abstract:

Based on density functional theory, the α-alanine molecule chiral transition mechanism in water was investigated. Having found the structures of heterogeneous transition states and intermediates at peak energy values of α-alanine in water, we drew up the potential energy surface of chiral hydrogen transfer isomerization processes α-alanine molecule in water. Compared with the isolated chiral transition, those with single or two water molecules as hydrogen transfer bridges made the transfer process energy barrier for H from chiral C to carbonyl O reduced from 325.5 kJ/mol to 200.6,173.0 kJ/mol respectively, and the energy barrier for H from carbonyl O to the other side of chiral C reduced from 229.2 kJ/mol to 105.3,73.5 kJ/mol respectively. The results reveal water molecules catalyze the chiral enantiomer transformation process of α-alanine, illustrating a possible source of a very small amount of D-alanine in vivo, which is due to water participiting in L-alanine chiral transition.

Key words: chiral, α-alanine, density functional theory, transition state