Dynamics of the interaction between water and the amino acids alanine, arginine, asparagine and glutamine using LED, QTAIM, AIMD and core-valence bifurcation (CVB) index

Abstract

The interplay of solvents is important in biological systems. This study examines the interaction between the water molecule and the amino acids viz, alanine, arginine, asparagine, and glutamine. The primary cause of the interaction is the hydrogen bond that forms between the oxygen atom in the water molecule and the hydrogen of the amino acid’s –OH group of the –COOH. The DFT approach was used to analyse the non-covalent interaction in gas phase. The NBO analysis is used to investigate the electron delocalisation between the amino acid and the water molecule. Binding energy is calculated using the QTAIM analysis and found that the asparagine – water system has more binding energy compared to the other four amino acid under consideration. RDG plots and NCI plots were used to analyse the non-covalent interaction between the moieties. DLPNO-CCSD(T) energy is decomposed into various components using the local energy decomposition method and the binding strength is analysed. AIMD analysis further confirms the stability of the interaction of water at the –COOH group of the amino acid. The hydrogen bonding strength is determined from the CVB index and the strong hydrogen bonding among the four amino acid is found in the asparagine – water system.