Excitation dynamics in photosynthetic light-harvesting complex B850: exact solution versus Redfield and Förster limits

Abstract

We model the excitation dynamics in bacterial B850 antenna using the standard Redfield, modified Redfield, and Förster approaches comparing them with the exact solution obtained with hierarchical equation of motion...

Excitation energy equilibration in a trimeric LHCII complex involves unusual pathways

“…In the site representation this looks like unrealistically fast energy transfer. 36,49 Breaking the exciton mixing between the weakly coupled compartments in the cmRgF picture allows us to eliminate a fast delocalization between them. This way we obtain more realistic transfer dynamics (i.e.…”

“…In the latter case we break some couplings in order to give more realistic kinetics under secular approximation. Although the omitted couplings are not so large, they are still sizable and can induce significant changes in reorganization shifts of the exciton states (that are proportional to the inverse delocalization degree, 29,49 so that even a small coherent admixture of neighbouring pigments can change significantly the shift value). For example, for a reorganization energy of 300 cm À1 (used in our modeling) a relatively small (10-20%) admixture of neighboring pigments will change a reorganizationinduced shift by 30-60 cm À1 .…”

“…Comparative studies of these methods (with their detailed description) have been done in ref. 36 and 49. As mentioned in the Introduction, the cmRgF theory is the most frequently used (and most successful) approach for modeling of the plant antenna complexes.…”

Simulation of the Pump–Probe Spectra and Excitation Energy Relaxation of the B850 Band of the LH2 Complex in Purple Bacteria

“…In the quest to unravel the complexities of photosynthetic energy transfer, the light harvesting complex 2 (LH2) in purple bacteria has served as an important model system for its well-characterized structure, distinctive photophysical properties, and its important role in funneling the excitation energy. Pump–probe spectroscopy has been extensively applied to investigate EET dynamics within LH2 complexes, ,,,,− and LH2-LH1 energy transfer. ,, …”

“…Perturbative methods such as the Redfield equation have been employed to simulate the EET dynamics and spectroscopic signals. But it has been realized later that, many problems in light harvesting complexes reside in the so-called intermediate coupling regime, making it necessary to go beyond second-order perturbations. , Recently, Novoderezhkin modeled the B850 population dynamics by using the HEOM and several perturbative methods, and demonstrated the limitations of the approximate methods in reproducing certain aspects of the correct dynamics.…”