Ar. Holzwarth et al., ULTRAFAST SPECTROSCOPY OF THE PRIMARY ELECTRON AND ENERGY-TRANSFER PROCESSES IN THE REACTION-CENTER OF PHOTOSYSTEM-II, Journal of luminescence, 60-1, 1994, pp. 497-502
The picosecond fluorescence kinetics of the D1-D2-cyt-b559 photosystem
II reaction center(RC)complex with 6 Chl/2 Pheo have been characteriz
ed upon preferential excitation of the special pair P680 at 685 nm. Th
e component with largest amplitude had a lifetime of 3 +/- 1 ps and is
attributed to the process of primary charge separation. In the short
time range two further lifetimes of 19 +/- 2 and 67 +/- 5 ps were reso
lved in addition. The 19 ps component is attributed mainly to energy t
ransfer from the antenna Chl(s) present in the preparation of RCs with
6 Chl/2 Pheo to the reaction center pigments. The 67 ps component may
have a mixed origin. Upon preferential excitation of the antenna Chls
at 650 nm also a slow energy transfer of about 22 ps is observed, tog
ether with a 5 ps component that shows negative amplitudes in its deca
y-associated spectrum (DAS). From femtosecond transient absorption dat
a,we infer an ultrafast anisotropy decay of about 0.5 ps which is assi
gned to energy transfer among the immediate pigments of the reaction c
enter (primary donor and accessory Chls and/or pheophytins).