Identification of the Terminal Energy Donor to the Reaction Center in the Pigment System of Green Plants by Time-Resolved Fluorescence Spectroscopy at - 196C

A specific antenna component in the photosynthetic pigment system,the direct energy donor to the reaction center (RC), was identifiedin PS I and II in green plants by time-resolved fluorescencespectroscopy at – 196C. The fluorescence components weredetected at 707 nm and 685 nm for PS I and II, respectively,and these antennae are hereafter referred to as the terminalenergy donors. In PS II, component that fluoresces at 695 nmalso functions as an energy pool; its rise time is slow (50ps), suggesting that it represents a side path in the flow ofenergy. The energy levels of these direct donors were lowerthan, or almost the same as that of the primary electron donorsin RC I (P700) and II (P680), respectively. The similaritiesand differences between these donors are discussed in relationto the structural and energetic properties of the antenna componentsin PS I and II core complexes. ¹This paper is dedicated to Prof. Y. Fujita on the occationof the 60th anniversary of his birth.