Many-Body meets QM/MM: Application to indole in water solution

TL;DR

This paper introduces a novel method combining many-body perturbation theory with QM/MM to accurately compute optical spectra of biological molecules in water, accounting for environmental effects.

Contribution

The work develops a new approach integrating quasi-particle and excitonic effects into QM/MM for large-scale spectral property calculations, validated on indole in water.

Findings

Solvent causes a redshift in indole's spectral peak.

The method achieves quantitative agreement with experimental spectra.

Averaging over molecular dynamics configurations is crucial for accurate results.

Abstract

Spectral properties of chromophores are used to probe complex biological processes in vitro and in vivo, yet how the environment tunes their optical properties is far from being fully understood. Here we present a method to calculate such properties on large scale systems, like biologically relevant molecules in aqueous solution. Our approach is based on many body perturbation theory combined with quantum-mechanics/molecular-mechanics (QM/MM) approach. We show here how to include quasi-particle and excitonic effects for the calculation of optical absorption spectra in a QM/MM scheme. We apply this scheme, together with the well established TDDFT approach, to indole in water solution. Our calculations show that the solvent induces a redshift in the main spectral peak of indole, in quantitative agreement with the experiments and point to the importance of performing averages over molecular dynamics configurations for calculating optical properties.