Theoretical studies of infrared signatures of proton-bound amino acid dimers with homochiral and heterochiral moieties

Mathias Poline; Oleksii Rebrov; Mats Larsson; Vitali Zhaunerchyk

doi:10.1002/chir.23165

Theoretical studies of infrared signatures of proton-bound amino acid dimers with homochiral and heterochiral moieties

Chirality. 2020 Mar;32(3):359-369. doi: 10.1002/chir.23165. Epub 2020 Jan 14.

Authors

Mathias Poline¹, Oleksii Rebrov¹, Mats Larsson¹, Vitali Zhaunerchyk²

Affiliations

¹ Department of Physics, Stockholm University, Stockholm, Sweden.
² Department of Physics, University of Gothenburg, Gothenburg, Sweden.

PMID: 31943359
DOI: 10.1002/chir.23165

Abstract

Proton-bound homochiral and heterochiral dimers, X-H⁺ -X, of five amino acids (X = Ser, Ala, Thr, Phe, and Arg) are investigated theoretically using quantum chemical density functional theory (DFT) calculations and molecular dynamics simulations with the aim to unveil diastereomer-specific mid-infrared (mid-IR) absorption bands in the spectral range of 1000 to 1800 cm^-1 . The theoretical calculations performed in this work imply that all systems, except Ala₂ H⁺ , have distinct mid-IR absorption bands in homochiral and heterochiral configurations, which make them appropriate systems to be studied experimentally with mid-IR spectroscopy. We show that intermolecular interaction with the side chain, in the form of hydrogen bonding or cation-π interaction, is necessary for chiral effects to be present in the mid-IR spectra of proton-bound dimers of amino acids. We also report new conformers for Ala₂ H⁺ , Thr₂ H⁺ , Phe₂ H⁺ , and Arg₂ H⁺ , which were not found in earlier studies of these dimers.

Keywords: DFT; amino acid dimers; chiral recognition; gas phase; infrared spectroscopy.