Abstract
The light-harvesting and primary charge-separation processes in photosystem I (PS I) reaction center have not been revealed completely, because of 1) the large spectral overlap among many antenna chlorophyll(Chl)s, 2) very fast energy transfers among Chl, and 3) the overlap of the time range between the light harvesting and primary charge separation. At cryogenic temperature, the above difficulties 1) and 2) are expected to be overcome because the Chl spectra become very sharp and the energy transfer becomes drastically slower. We studied the ultrafast fluorescence dynamics of PS I at 15 K. The results showed that at 15 K the antenna Chl in PS I are divided into 3 groups; Chl that transfer the excitation energy to P700 with a 5-ps time constant, 300-ps time constant, and transfer the excitation energy to the red Chl with a 30-ps time constant. Stoichiometry of these Chl groups will be discussed.
