Speaker
Description
Two-Dimensional Electronic Spectroscopy provides an excellent platform for studying the exciton and charge separation dynamics in photosynthetic systems. While applications to individual photosynthetic complexes does provide valuable insight, it has become increasingly clear that the interaction between individual complexes comprising the functional super-complexes affect the behaviour of the individual parts [1]. This calls for spectroscopic measurements of both full super complexes and carefully chosen sub-units. The resulting spectra are, however, challenging to interpret, and common simulation methods are limited to small systems. Here, we present a new efficient coarse grained spectral simulation protocol [2].
The new protocol uses a separation of chromophores into strongly coupled segments. The dynamics within segments may be coherent, while dynamics between segments must be incoherent. The dynamics in different segments is assumed to be uncorrelated. This allows the use of a kinetic model based on the time-dependent multi-chromophoric fluorescence resonant energy transfer method [3] to account for waiting time dynamics, while doorway-window picture response functions are applied to describe the coherence times. The resulting spectra are efficiently calculated with no additional cost for calculating spectra for numerous waiting times.
The developed method is demonstrated for the guinea pig photosynthetic system, LH2, of purple bacteria. Here, the strengths and weaknesses of the coarse-grained method are identified by comparison with other simulations and experiment. For example, an excellent description of the femto-to-picosecond anisotropy dynamics is demonstrated [2]. Finally, the application to the PSII photosynthetic super-complex of plants will be discussed. It will be demonstrated how the simulation technique can be used to aid experimental interpretation and reveal energy transfer pathways and exciton traps and sinks.
[1] Sci. Adv. 2024, 10, eadh0911
[2] J.Chem. Theory Comput. 2024, 20,6111−6124
[3] J.Chem. Theory Comput. 2025, 21,254−266
