Insight into the interaction between amino acids and SO₂: Detailed bonding modes

Area of Science:

• Computational Chemistry
• Materials Science
• Environmental Chemistry

Background:

• Amino acids are recognized as effective and eco-friendly adsorbents for sulfur dioxide (SO2).
• A detailed molecular-level understanding of amino acid-SO2 binding modes is currently lacking.
• This research addresses the need for comprehensive studies on the interaction mechanisms between amino acids and SO2.

Purpose of the Study:

• To comprehensively investigate the molecular-level binding modes between three representative amino acids (Aspartic acid, Lysine, Valine) and SO2.
• To elucidate the role of functional groups and types of interactions (chalcogen bonds, hydrogen bonds) in SO2 adsorption.
• To quantify binding energies and analyze the nature of interactions using advanced computational methods.

Main Methods:

• Quantum chemical calculations were employed to study the binding modes of amino acids with SO2.
• Semi-empirical molecular dynamics (MD) using Molclus and xtb at the GFN2 level were performed.
• Density-functional theory (DFT) calculations (B3LYP/6-311G*) and coupled-cluster calculations (DLPNO-CCSD(T)) were used for optimization, frequency, and single-point energy calculations.
• Further analyses included electrostatic potential (ESP), atoms in molecules (AIM), interpenetrating மேற்பரப்பு (IGMH), and symmetry-adapted ശങ്കer-bond dissociation energy (sob-EDA).

Main Results:

• Multiple binding modes were identified for each amino acid: 22 for Aspartic acid, 49 for Lysine, and 10 for Valine.
• Amino and carboxyl groups, including those in side chains, act as binding sites for chalcogen bonds.
• Binding energies varied significantly, ranging from -6.42 to -1.06 kcal/mol for Asp, -12.43 to -1.63 kcal/mol for Lys, and -7.42 to -0.60 kcal/mol for Val.
• Chalcogen and hydrogen bonds were found to be crucial for stronger binding modes, with the strongest chalcogen bond observed with an amino group.
• Energy decomposition analysis revealed that electrostatic attraction is the primary interaction, with orbital and dispersive contributions varying by binding mode.

Conclusions:

• Amino acids exhibit diverse binding modes with SO2, facilitated by functional groups capable of forming chalcogen and hydrogen bonds.
• The strength of SO2 adsorption is influenced by the specific amino acid structure and the nature of the dominant intermolecular forces.
• Computational chemistry provides valuable insights into the molecular mechanisms of SO2 adsorption by amino acids, relevant for developing novel adsorbents.