Exciting out-of-equilibrium states in macromolecules through light pumping

TL;DR

This paper investigates how light energy absorbed by fluorophores attached to proteins can be transferred into vibrational modes, leading to coherent oscillations, and addresses the initial step of energy transfer from electronic excitation to phonons.

Contribution

It provides a theoretical analysis of the energy transfer process from electronic excitation to vibrational phonons in proteins under light pumping, filling a key gap in understanding.

Findings

Energy transfer from electronic to vibrational modes is feasible under specific conditions.

Light pumping can induce coherent vibrational oscillations in proteins.

Theoretical framework explains the initial energy transfer step.

Abstract

In the present paper we address the problem of the energy downconversion of the light absorbed by a protein into its internal vibrational modes. We consider the case in which the light receptors are fluorophores either naturally co-expressed with the protein or artificially covalently bound to some of its amino acids. In a recent work [Phys. Rev. X 8, 031061 (2018)], it has been experimentally found that by shining a laser light on the fluorophores attached to a protein the energy fed to it can be channeled into the normal mode of lowest frequency of vibration thus making the subunits of the protein coherently oscillate. Even if the phonon condensation phenomenon has been theoretically explained, the first step - the energy transfer from electronic excitation into phonon excitation - has been left open. The present work is aimed at filling this gap.