Abstract
When the freeze-dried PSI particle is treated with the water-containing diethylether, most of the antenna chlorophylls, carotinoids and quinines are extracted, preserving the P700 activity. The enhanced charge-recombination due to the extraction of quinones results in the re-population of P700* and then appearance of a slow fluorescence component (delayed fluorescence; DL). By measuring the temperature dependence of the DL component, we can deduce the energy gap between P700+-A0- and P700*. Our picosecond-time-resolved fluorescence measurement of the ether-treated PSI sample in a 77-270 K temperature region revealed the following tendency. 1) Above 200 K, the relative intensity of DL decreases with decreasing temperature. 2) Below 200 K, it increases down to 150 K and again decreases with further decrease of temperature. We will discuss the energetics of the initial charge-separation process of PSI, considering the distribution of the energy gap at low temperature.
