Interactions study between the copper II ion and constitutive elements of chitosan structure by DFT calculation

Area of Science:

• Computational chemistry
• Biochemistry
• Molecular dynamics

Background:

• Understanding molecular interactions is crucial in various scientific fields.
• Glucosamine and its derivatives are important biomolecules with potential roles in biological systems.
• Copper ions play significant roles in biological processes and can interact with biomolecules.

Purpose of the Study:

• To investigate the interaction between a single copper ion (Cu2+) and glucosamine residues using molecular modeling.
• To determine the preferred coordination sites and binding energies of Cu2+ with glucosamine and N-acetylglucosamine.
• To explore the conformational landscape of glucosamine dimers and their interaction with Cu2+.

Main Methods:

• Density Functional Theory (DFT) methods were employed to compute geometries and interaction energies.
• Systematic conformational searches were performed by rotating dihedral angles of the glycosidic bond.
• Complexes were modeled with water and/or hydroxide ligands to achieve neutral charge.

Main Results:

• The most stable interaction of Cu2+ with glucosamine involved the free amino group in a "pending complex" formation.
• N-acetylglucosamine was found to be unable to coordinate with Cu2+.
• Glucosamine cannot act as a bidentate ligand for Cu2+.
• Cooperative binding of successive Cu2+ ions was observed on adjacent glucosamine residues in a dimer.

Conclusions:

• The amino group of glucosamine is the primary site for Cu2+ coordination.
• The N-acetyl group in N-acetylglucosamine hinders its ability to bind Cu2+.
• Understanding these interactions provides insights into the behavior of metal ions with carbohydrates.