S. Savikhin et al., Kinetics of charge separation and A(0)(-)-> A(1) electron transfer in photosystem reaction centers, BIOCHEM, 40(31), 2001, pp. 9282-9290
The charge separation P700*A(0) --> P700(+)A(0)(-) and the subsequent elect
ron transfer from the primary to secondary electron acceptor have been stud
ied by subtracting absorption difference profiles for cyanobacterial photos
ystem I (PS I) complexes with open and closed reaction centers. Samples wer
e excited at 660 run, which lies toward the blue edge of the core antenna a
bsorption spectrum. The resulting PS I kinetics were analyzed in terms of t
he relevant P700, P700(+), A(0), and A(0)(-) absorption spectra. In our kin
etic model, the radical pair P700+A(0)(-) forms with 1.3 ps rise kinetics a
fter creation of electronically excited P700*. The formation of A(1)(-) via
electron transfer from A(0) requires similar to 13 ps. The kinetics of the
latter step are appreciably faster than previously estimated by other grou
ps (20-50 ps).