The FCP complexes from brown algae Cladosiphon okamuranus TOKIDA contain the only one species of carbonyl carotenoid, fucoxanthin, which exhibits spectral characteristics attributed to an intramolecular charge-transfer (ICT) property that arises in polar environments due to the presence of the carbonyl group in its polyene backbone. We investigated the role of the ICT property of fucoxanthin in ultrafast energy transfer to chlorophyll-a/c in brown algal photosynthesis using femtosecond pump-probe spectroscopic measurements. The observed excited-state dynamics show that the ICT character of fucoxanthin in FCP extends its absorption band to longer wavelengths and enhances its electronic interaction with chlorophyll a molecules, leading to efficient energy transfer from fucoxanthin to chlorophyll-a. The observed excited state dynamics show that a large part of excitation energy captured by fucoxanthin is transferred to chlorophyll a via the coupled S1/ICT state. The excitation energy-dependent photo-induced absorption spectra and their kinetics exhibited that the ICT character of fucoxanthin in FCP extends its absorption band to longer wavelengths and enhances its electronic interaction with chlorophyll a molecules, leading to efficient energy transfer from fucoxanthin to chlorophyll a. The present results give insight for the basic ideas to construct the efficient light-harvester that is one of the essential elements for artificial photosynthesis.

Ultrafast fucoxanthin ? chlorophyll an energy transfer in brown algal light-harvesting antennas

247th National Meeting (2014)

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