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2018 ; 20
(6
): 4360-4372
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Robust light harvesting by a noisy antenna
#MMPMID29368769
Malư P
; Gardiner AT
; Cogdell RJ
; van Grondelle R
; Man?al T
Phys Chem Chem Phys
2018[Feb]; 20
(6
): 4360-4372
PMID29368769
show ga
Photosynthetic light harvesting can be very efficient in solar energy conversion
while taking place in a highly disordered and noisy physiological environment.
This efficiency is achieved by the ultrafast speed of the primary photosynthetic
processes, which is enabled by a delicate interplay of quantum effects,
thermodynamics and environmental noise. The primary processes take place in
light-harvesting antennas built from pigments bound to a fluctuating protein
scaffold. Here, we employ ultrafast single-molecule spectroscopy to follow
fluctuations of the femtosecond energy transfer times in individual LH2 antenna
complexes of purple bacteria. By combining single molecule results with ensemble
spectroscopy through a unified theoretical description of both, we show how the
protein fluctuations alter the excitation energy transfer dynamics. We find that
from the thirteen orders of magnitude of possible timescales from picoseconds to
minutes, the relevant fluctuations occur predominantly on a biological timescale
of seconds, i.e. in the domain of slow protein motion. The measured spectra and
dynamics can be explained by the protein modulating pigment excitation energies
only. Moreover, we find that the small spread of pigment mean energies allows for
excitation delocalization between the coupled pigments to survive. These unique
features provide fast energy transport even in the presence of disorder. We
conclude that this is the mechanism that enables LH2 to operate as a robust
light-harvester, in spite of its intrinsically noisy biological environment.
|Alphaproteobacteria/metabolism
[MESH]
|Energy Transfer
[MESH]
|Light-Harvesting Protein Complexes/*chemistry/metabolism
[MESH]
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