An Approach Based on Organic Synthesis Toward Elucidating the Mechanism of Super Energy Transfer Efficiencies of Peridinin in Photosynthesis

Peridinin is known as a representative auxiliary light harvesting pigment for photosynthesis in the sea. In the peridinin-chlorophyll (Chl) a-protein (PCP) complex, exceptionally high (>95%) energy transfer efficiencies from peridinin to Chl a has been reported. This energy transfer efficiency is thought to be related to the unique structure of peridinin, which possesses allene and ylidenbutenolide functions and the unusual C37 carbon skeleton referred to as a ‘nor-carotenoid’. There are, however, no studies on the subjects of why peridinin possesses a unique allene group and an irregular C37 skeleton, and how these functions play a role in the exceptionally high energy transfer. We have established the highly efficient synthesis of natural peridinin and successfully synthesized its allene and conjugated polyene modified derivatives. Measurements of their ultrafast time resolved spectra and Stark spectra have strongly suggested that these structural feature of peridinin has essentially contributed to its super ability of energy transfer.