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

Abstract

Amino acids are a highly effective and enviromentally friendly adsorbent for SO₂. However, there has been no comprehensive study of the binding modes between amino acids and SO₂ at the molecular level. In this paper, the binding modes of three amino acids (Asp, Lys, and Val) with SO₂ are studied comprehensively and in detail using quantum mechanical semi-empirical molecular dynamics simulations as well as high-precision quantum chemical calculations. The results indicate that each amino acid has multiple binding modes: 22 for Asp, 49 for Lys, and 10 for Val. Both the amino and carboxyl groups in amino acids, as well as those in side chains, can serve as binding sites for chalcogen bonds. The binding energies range 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 play a crucial role in the stronger binding modes. The chalcogen bond is the strongest when interacting with an amino group, with an adiabatic force constant of 0.475 mDyn/Å. Energy decomposition analysis indicates that the interaction is primarily electrostatic attraction, with the orbital and dispersive interactions dependent on the binding modes. This work presents a dependable theoretical foundation for the adsorption of SO₂ by amino acids, which is valuable for the application of amino acids in the field of adsorbent materials.