PeridininChlorophyll

Peridinin–chlorophyll a–protein (PCP) is a light-harvesting pigment–protein complex found in dinoflagellates. It consists of chlorophyll a and the carotenoid peridinin bound to a small, highly organized protein scaffold. In dinoflagellate thylakoid membranes PCP forms oligomeric assemblies that capture light energy in the blue to green region of the spectrum and funnel it to chlorophyll a in the photosynthetic reaction centers.

Pigments in PCP include peridinin, a unique carotenoid with an allenic bond, which extends absorption into the blue–green region (approximately 480–520 nm). This broad absorption complements chlorophyll a, which primarily absorbs in the blue and red parts of the spectrum, enabling dinoflagellates to utilize light conditions common in aquatic environments.

Energy transfer within PCP occurs from peridinin to chlorophyll a via efficient Förster-type resonance energy transfer. The pigments are positioned by the protein scaffold to maximize overlap between peridinin emission and chlorophyll a absorption, facilitating rapid and directional energy flow while helping to protect chlorophyll from photodamage.

Functionally, PCP acts as an antenna complex, expanding the usable light spectrum for photosynthesis in environments where blue–green light dominates. The energy ultimately reaches chlorophyll a and is directed to the photosystems to drive photochemistry. PCP has been studied as a model system for understanding pigment–protein interactions and highly efficient light harvesting in dinoflagellates, contributing to broader insights into photosynthetic diversity.