An important component of the photosynthetic apparatus is a light-harvesting system that captures light energy and transfers it efficiently to the reaction center. Depending on environmental conditions, photosynthetic antennae have adopted various strategies for this function. Peridinin-chlorophyll-a protein (PCP) represents a unique situation because, unlike other antenna systems which have a preponderance of chlorophyll, it has the carotenoid, peridinin, as its major pigment. The key structural feature of peridinin is a conjugated carbonyl group. Owing to the presence of this group, an intramolecular charge-transfer excited state is formed in peridinin which exhibits different excited state spectra and dynamics depending on the polarity of the environment. The charge-transfer state also facilitates energy transfer between peridinin and chlorophyll-a in PCP. This review summarizes results of spectroscopic investigations of PCP in the past few years, emphasizing the specific light-harvesting strategy developed by marine photosynthetic organisms utilizing carbonyl-containing carotenoids in their antenna complexes.

Institute of Physical Biology University of South Bohemia Zamek 136 CZ 373 33 Nove Hrady Czech Republic

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Ultrafast spectroscopy tracks carotenoid configurations in the orange and red carotenoid proteins from cyanobacteria

Low-temperature time-resolved spectroscopic study of the major light-harvesting complex of Amphidinium carterae

Photoprotection in a purple phototrophic bacterium mediated by oxygen-dependent alteration of carotenoid excited-state properties

Molecular factors controlling photosynthetic light harvesting by carotenoids

Femtosecond carotenoid to retinal energy transfer in xanthorhodopsin

Energy transfer in the peridinin-chlorophyll protein complex reconstituted with mixed chlorophyll sites