Investigation of the excitation energy transfer pathways of photosynthetic RC–LH1 supercomplexes

Abstract

Understanding excitation energy transfer (EET) in reaction center-light-harvesting 1 (RC–LH1) supercomplexes is critical for elucidating the principles of bacterial photosynthesis and informing the design of artificial light-harvesting systems. In this study, we combined generalized Förster (GF) theory with shortest-path network analysis to investigate EET pathways across seven structurally distinct RC–LH1 complexes from Rhodobacter sphaeroides, including wild-type and ΔpufX/ΔpufY mutants. The calculated EET times (approximately 40–46 ps) closely match experimental measurements, indicating stable transfer kinetics despite structural variations. Our results show that EET efficiency is primarily determined by electronic coupling (V²), which depends on both the distances between pigments and the alignment of their Q_y transition dipole moments. Correlation analysis confirms that V² plays a more significant role than site energy or distance alone. Network analysis further identifies a set of conserved high-centrality BChls that serve as key hubs within a redundant energy transfer network. Even with the sequential removal of central nodes, the system maintains connectivity through alternative routes. These findings highlight the structural resilience and functional stability of the bacterial photosynthetic apparatus. The analytical framework developed here may also apply to broader studies of energy transfer in natural and artificial systems.