Light harvesting complex II B850 excitation dynamics

Abstract

The dynamics of excitation energy transfer within the B850 ring of light harvesting complex 2 from Rhodobacter sphaeroides and between neighboring B850 rings is investigated by means of dissipative quantum mechanics. The assumption of Boltzmann populated donor states for the calculation of intercomplex excitation transfer rates by generalized Förster theory is shown to give accurate results since intracomplex exciton relaxation to near-Boltzmann population exciton states occurs within a few picoseconds. The primary channels of exciton transfer between B850 rings are found to be the five lowest-lying exciton states, with non-850 nm exciton states making significant contributions to the total transfer rate.

Energy transfer in structured and unstructured environments: Master equations beyond the Born-Markov approximations

“…Strong coupling between the system and its environment leads to the accumulation of significant system-environment correlations that may be present even a) Electronic mail: Jakeilessmith@gmail.com b) Electronic mail: ahsan.nazir@manchester.ac.uk within the steady-state. [16][17][18][19] In addition to the (often low frequency) continuum, the environmental spectral densities of pigment-protein complexes are generally structured; that is, there are specific underdamped vibrational modes of the environment that couple strongly to the excitonic degrees of freedom. There is now increasing evidence to suggest that these underdamped modes are an important contributing factor to the long-lived coherences observed in photosynthetic systems, [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] as well as links between the quantum mechanical nature of these vibrational modes and enhanced transfer rates.…”

Excited state dynamics in photosynthetic reaction center and light harvesting complex 1

“…Due to the complexity of systems like those seen in light-harvesting an effective Hamiltonian description is often used to characterize such systems. 42,43,48,[52][53][54] The effective Hamiltonian involves only the most relevant subset of states. In case of excitation dynamics of light harvesting systems, the low-light photon level in the habitat of the biological organisms permits one to confine the effective Hamiltonian to the manifold of single pigment excitations, yielding an effective Hamiltonian given by…”

“…There have been many efforts towards this goal, 26,[28][29][30][31][32][33][34][35][36][37][38][39] but only parts of the system were modeled at a time. In the present work we furnish an overall description of RC excitation dynamics employing a method that has become widely accepted, [40][41][42][43][44][45] namely the hierarchy equations of motion (HEOM) method. To apply the method we suggest an effective Hamiltonian and coupling to the environment.…”

Simulated two-dimensional electronic spectroscopy of the eight-bacteriochlorophyll FMO complex

“…To tackle this problem, a methodology referred to as hierarchical equation of motion (HEOM) has been developed by Tanimura and co-workers [19,20]; a high temperature approximation (HTA) of HEOM has also been developed by Ishizaki and co-workers to describe the EET dynamics in a model dimer [21,22]. The HEOM has already been implemented in calculating the excitonic transfer dynamics of photosynthetic proteinpigment complexes [23][24][25][26][27] and more recently it is also used within simulations of the linear and 2D electronic spectra of the above mentioned systems [28][29][30].…”