Peridinin

Peridinin is a xanthophyll carotenoid pigment found primarily in dinoflagellates, a diverse group of marine protists. It is a principal component of the light-harvesting antenna, particularly in the peridinin-chlorophyll protein (PCP) complex, which captures light energy and transfers it to chlorophyll a for photosynthesis.

Structure and properties: Peridinin has a long conjugated polyene chain and an unusual allenic (cumulated) functional group at one end, connected to a cyclic end group. This distinctive structure extends electronic conjugation and imparts unique photophysical behavior. It absorbs light mainly in the blue-green region, approximately 470–500 nm, a range well suited to aquatic light conditions. The excited-state dynamics, including an intramolecular charge-transfer state, facilitate efficient energy transfer to chlorophyll within PCP.

Role in photosynthesis: In PCP, peridinin acts as an antenna pigment, capturing photons across a broad portion of the visible spectrum and funneling the excitation energy toward chlorophyll a with high efficiency. This broadens the usable light spectrum for dinoflagellates and enhances photosynthetic performance under blue-green aquatic light.

Occurrence and significance: Peridinin is characteristic of dinoflagellates and is less common in other photosynthetic organisms. Its presence is linked to certain symbiotic relationships, such as those between dinoflagellates and reef-building corals, where it contributes to the efficiency of light capture in the symbiotic unit.

Research and applications: The PCP-pigment system, including peridinin, has been central to studies of fast energy transfer, pigment–protein interactions, and the photophysics of excited states in natural light-harvesting complexes.