Complexation Dynamics of Calcium Ion in Chitosan Monomer: A Theoretical Assessment from the Gas-Phase to Microsolvation Environments

This study investigates the interaction between calcium ions and glucosamine molecules (GlcN) gas-phase and the interaction of calcium ion with GlcN in the microsolvation environments using Car Parrinello molecular dynamics and density functional theory. Our findings reveal stable complexation between GlcN and calcium ions at various molecular sites in gas-phase and in the microsolvation environments. Furthermore, the Quantum Theory of Atoms in Molecules (QTAIM) analyses indicate a predominantly ionic character for all interactions in both gas-phase and microsolvation systems. The Natural Bond Orbital analyses demonstrate that the calcium ion serves as an electron acceptor, receiving lone pairs of electrons from oxygen and nitrogen atoms for its vacant orbitals. A comprehensive understanding of GlcN-calcium-water interactions at the molecular level can contribute to new research directions and applications for chitosan and its monomer, glucosamine, in the pharmacological domain.