Abstract
Multichromophoric interactions control the initial events of energy capture and transfer in the light harvesting peridinin-chlorophyll a protein (PCP) from marine algae dinoflagellates. Due to the van der Waals association of the carotenoid peridinin (Per) with chlorophyll a in a unique 4:1 stoichiometric ratio, supramolecular quantum mechanical/molecular mechanical (QM/MM) calculations are essential to accurately describe structure, spectroscopy, and electronic coupling. We show that, by enabling inter-chromophore electronic coupling, substantial effects arise in the nature of the transition dipole moment and the absorption spectrum. We further hypothesize that inter-protein domain Per-Per interactions are not negligible, and are needed to explain the experimental reconstruction features of the spectrum in wild-type PCP.
Highlights
The capture, conversion, and transfer of solar energy by artificial means constitute some of the greatest research challenges at present [1,2]
While we have carried out such calculations on a single domain of peridinin-chlorophyll a protein (PCP), this approach becomes intractable when considering chromophore interactions between the two protein domains at the TD-density functional theory (DFT) level
We showed that the energy transfer (EET) methodology can be used to obtain quality excitation energies for cases where the inclusion of all PCP cofactors is intractable within quantum mechanical/molecular mechanical (QM/MM) at a time dependent DFT (TD-DFT) level
Summary
The capture, conversion, and transfer of solar energy by artificial means constitute some of the greatest research challenges at present [1,2]. Natural architectures that overcome these difficulties have been evolved by photosynthetic algae, bacteria, and plants, which collectively consume an estimated five times more power than is needed for all human activities [3]. Lessons learned from the mechanistic study of natural light harvesting complexes will inform and inspire the rational design of artificial photosynthetic devices capable of meeting growing energy demands for sustainable human development [1,4,5]. A notable example of a highly efficient light harvesting antenna is the water-soluble peridinin-chlorophyll a protein (PCP) from marine algae dinoflagellates [6]. Each cofactor cluster has a unique 4:1 stoichiometric ratio of the structurally distinctive carotenoid peridinin (Per) and chlorophyll a (Chl a), as seen, as well as a molecule of the lipid digalactosyldiacylglycerol. Per is a heptene-based chromophore that features a C37 , instead of the standard C40 carotenoid framework, as well as an unusual pairing of allenic and γ-butenolide moieties, as seen in Figure 1b, which significantly shapes the photophysical response of the polyene chain to the polarity, proticity, and polarizability of the local environment [6]
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