Vibrational energy relaxation (VER) of isotopically labeled amide I modes in cytochrome c: Theoretical investigation of VER rates and pathways

TL;DR

This theoretical study investigates vibrational energy relaxation of isotopically labeled amide I modes in cytochrome c, revealing detailed pathways, environmental sensitivities, and sub-picosecond relaxation times through perturbation theory.

Contribution

It provides a detailed theoretical analysis of VER pathways and rates in cytochrome c, highlighting environmental effects and spatial anisotropy of the relaxation process.

Findings

VER occurs on sub-picosecond timescales.

Relaxation pathways depend on the local environment.

Protein and water contributions to VER are quantitatively decomposed.

Abstract

Using a time-dependent perturbation theory, vibrational energy relaxation (VER) of isotopically labeled amide I modes in cytochrome c solvated with water is investigated. Contributions to the VER are decomposed into two contributions from the protein and water. The VER pathways are visualized using radial and angular excitation functions for resonant normal modes. Key differences of VER among different amide I modes are demonstrated, leading to a detailed picture of the spatial anisotropy of the VER. The results support the experimental observation that amide I modes in proteins relax with sub picosecond timescales, while the relaxation mechanism turns out to be sensitive to the environment of the amide I mode.