Abstract

The ultrafast dynamics of electron relays in the Photosystem I (PS I) reaction center (RC) is of particular interest because the amino acid sequences of the polypeptides show almost no homology to those of PS II-purple-bacterial type RC’s. Electron carriers and energy levels of PS I RC are also different from those of the latter type of RC’s. However, studies in Photosystem I have been scarce due to its large number of antenna chlorophylls (more than 100) per RC and to resultant spectral congestion. Even though the presence of the primary electron acceptor chlorophyll (A₀) has been suggested by a recent X-ray crystallographic work [1], spectroscopic detection of sequential reduction and reoxidation of A₀ has never been successful.

© 1994 Optical Society of America