Ultrafast Energy Transfer from Chlorophyll <i>c</i>₂ to Chlorophyll <i>a</i> in Fucoxanthin–Chlorophyll Protein Complex

Abstract

Light-harvesting in fucoxanthin-chlorophyll protein (FCP) of diatoms is performed by a cluster of chromophores: chlorophylls a (Chl a), chlorophylls c2 (Chl c2), and carotenoids fucoxanthins. It is well-known that energy captured by fucoxanthin is transferred to Chl a on a subpicosecond time scale. However, the energy flow channel connecting Chl c2 and Chl a remained elusive. In this study, the energy transfer between Chl c2 and Chl a molecules in the FCP complex from the diatom algae C. meneghiniana at room temperature is investigated using pump–probe and coherent two-dimensional electronic spectroscopy. Measured dynamics of the absorption band associated with the Qy transition of the Chl c2 reveals an ultrafast energy transfer pathway to Chl a. This conclusion is supported by the theoretical simulations based on the effective oscillator model.