Conformation, energies and complexation between alkali cations and aspartic acid

Abstract

This research work is separated into three parts employing density functional calculation. The first part, the gas phase conformations of various aspartic species including cationic (H3asp+), zwitterionic (H2asp), zwitteranionic (Hasp−) and dianionic (asp2−) were explored using potential energy surface (PES) method. Secondly, the complexations between alkali cations; lithium, sodium and potassium and species H2asp, Hasp− and asp2− of aspartic acid were investigated. The metal ion affinities in term of reaction enthalpy obtained by vibrational frequency calculation at 298.15 K for all complexes are reported. Finally, acid–dissociation constants, pKa of aspartic species in aqueous solution were determined using Polarize continuum model (PCM) as solvent–effect calculation.