Electron transfer pathway analysis in bacterial photosynthetic reaction center

TL;DR

This paper introduces a computational method combining fragment molecular orbitals and electron tunneling analysis to efficiently study electron transfer pathways in large biomolecules, exemplified by bacterial photosynthetic reaction centers.

Contribution

It presents a novel first-principles scheme for analyzing ET pathways in large biomolecules, revealing detailed roles of metal ions and ligands in bacterial photosynthesis.

Findings

Identified key roles of Fe$^{2+}$ ion and histidine ligands in ET pathways.

Showed ET rate insensitivity to metal ion substitution and depletion.

Demonstrated the method's effectiveness on bacterial photosynthetic reaction centers.

Abstract

A new computational scheme to analyze electron transfer (ET) pathways in large biomolecules is presented with applications to ETs in bacterial photosynthetic reaction center. It consists of a linear combination of fragment molecular orbitals and an electron tunneling current analysis, which enables an efficient first-principles analysis of ET pathways in large biomolecules. The scheme has been applied to the ET from menaquinone to ubiquinone via nonheme iron complex in bacterial photosynthetic reaction center. It has revealed that not only the central Fe$^{2+}$ ion but also particular histidine ligands are involved in the ET pathways in such a way to mitigate perturbations that can be caused by metal ion substitution and depletion, which elucidates the experimentally observed insensitivity of the ET rate to these perturbations.