Optimal number of pigments in photosynthetic complexes

TL;DR

This study models excitation energy transfer in photosynthetic complexes to determine the optimal number of pigments for efficiency and robustness, aligning findings with natural structures.

Contribution

It introduces a simple Lindblad equation-based model to identify the optimal pigment number balancing efficiency and robustness in photosynthetic complexes.

Findings

Optimal pigment number maximizes transfer efficiency and robustness.

Many pigment configurations are efficient if the number is properly chosen.

Model results agree with natural pigment-protein complex structures.

Abstract

We study excitation energy transfer in a simple model of photosynthetic complex. The model, described by Lindblad equation, consists of pigments interacting via dipole-dipole interaction. Overlapping of pigments induces an on-site energy disorder, providing a mechanism for blocking the excitation transfer. Based on the average efficiency as well as robustness of random configurations of pigments, we calculate the optimal number of pigments that should be enclosed in a pigment-protein complex of a given size. The results suggest that a large fraction of pigment configurations are efficient as well as robust if the number of pigments is properly chosen. We compare optimal results of the model to the structure of pigment-protein complexes as found in nature, finding good agreement.