The relationship between the tyrosine residue 850-830 cm-1 Raman doublet intensity ratio and the aromatic side chain χ1 torsion angle

Belén Hernández; Yves-Marie Coïc; Sergei G Kruglik; Santiago Sanchez-Cortes; Mahmoud Ghomi

doi:10.1016/j.saa.2023.123681

The relationship between the tyrosine residue 850-830 cm^-1 Raman doublet intensity ratio and the aromatic side chain χ₁ torsion angle

Spectrochim Acta A Mol Biomol Spectrosc. 2024 Mar 5:308:123681. doi: 10.1016/j.saa.2023.123681. Epub 2023 Nov 25.

Authors

Belén Hernández¹, Yves-Marie Coïc², Sergei G Kruglik³, Santiago Sanchez-Cortes⁴, Mahmoud Ghomi⁵

Affiliations

¹ LVTS, INSERM U1148, 74 rue Marcel Cachin, 93017 Bobigny Cédex, France.
² Institut Pasteur, Université Paris Cité, CNRS UMR3523, Unité de Chimie des Biomolécules, F-75015 Paris, France.
³ Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Jean-Perrin, 4 Place Jussieu, 75005 Paris, France.
⁴ Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006 Madrid, Spain.
⁵ Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006 Madrid, Spain. Electronic address: mahmoud.ghomi@univ-paris13.fr.

PMID: 38039641
DOI: 10.1016/j.saa.2023.123681

Abstract

Tyrosine (Tyr) residue in a peptide chain is characterized by the presence of seven Raman markers, referred to as Y_i (i = 1, …, 7), distributed over the middle wavenumber spectral region. Particularly, the changes observed in the relative intensity of Y₅ and Y₆ markers, appearing as a side by side doublet at ca. 850-830 cm^-1, has received a great attention. Primarily assigned to a Fermi-resonance effect between phenol ring planar and nonplanar modes, former density functional theory calculations led us to affiliate the Y₅-Y₆ doublet to two distinct fundamental modes. Furthermore, despite the previous assumptions, it was evidenced that the reversal of the doublet intensity ratio cannot be solely explained by hydrogen bonding on the phenol hydroxyl group involved in Tyr. Herein, upon analyzing the observed and theoretical data collected from the cationic species of the tripeptide Gly-Tyr-Gly, the crucial effect of the aromatic side chain orientation, especially that of the χ₁ torsion angle defined around the C_αC_β bond, on the Tyr doublet intensity ratio has been evidenced.

Keywords: DFT calculations; Extended chain; Glycyltyrosylglycine; Helix; Peptide; Polyproline-II; Raman spectra; γ-turn.