Vibration-enhanced energy transfer in living molecules

TL;DR

This paper introduces a simple spin-boson quantum model demonstrating how vibrational modes can enhance energy transfer efficiency in photosynthetic molecules, aligning with observed near-perfect transfer in biological systems.

Contribution

It presents a novel, minimalistic quantum model that explains high energy transfer efficiency via vibrational resonance, applicable to complex biological systems like FMO.

Findings

Vibrational modes can bring donor-acceptor systems into resonance.

High transfer efficiency is achievable in a seven-exciton system.

The model makes testable predictions about vibrationally enhanced energy transfer.

Abstract

The conversion of an absorbed photon from the exciton energy into the reaction centre in the photosynthetic complex has a near unit efficiency. It is becoming clear that any classical model, where the exciton hopping is modeled by a classical stochastic diffusion equation, cannot explain such a high degree of efficiency. A number of different quantum models have been proposed, ranging from a purely unitary model with long range exciton interactions to a noise-aided stochastic resonance models. Here we propose a very simple spin-boson model that captures all the features of the efficient part of energy transfer. We show how this model describes a scenario where a donor-acceptor system can be brought into resonance by a narrow band of vibrational modes so that the excitation transfer between the two can be made arbitrarily high. This is then extended to a seven exciton system such as the widely-studied FMO photosynthetic complex to show that a high efficiency is also achievable therein. Our model encodes a number of readily testable predictions and we discuss its generalisations to include the localisation in the reaction centre.