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A Structure-Based Model of Energy Transfer Reveals the Principles of Light Harvesting in Photosystem II Supercomplexes
journal contribution
posted on 2013-06-19, 00:00 authored by Doran
I. G. Bennett, Kapil Amarnath, Graham R. FlemingPhotosystem II (PSII) initiates photosynthesis
in plants through
the absorption of light and subsequent conversion of excitation energy
to chemical energy via charge separation. The pigment binding proteins
associated with PSII assemble in the grana membrane into PSII supercomplexes
and surrounding light harvesting complex II trimers. To understand
the high efficiency of light harvesting in PSII requires quantitative
insight into energy transfer and charge separation in PSII supercomplexes.
We have constructed the first structure-based model of energy transfer
in PSII supercomplexes. This model shows that the kinetics of light
harvesting cannot be simplified to a single rate limiting step. Instead,
substantial contributions arise from both excitation diffusion through
the antenna pigments and transfer from the antenna to the reaction
center (RC), where charge separation occurs. Because of the lack of
a rate-limiting step, fitting kinetic models to fluorescence lifetime
data cannot be used to derive mechanistic insight on light harvesting
in PSII. This model will clarify the interpretation of chlorophyll
fluorescence data from PSII supercomplexes, grana membranes, and leaves.