Abstract

In an earlier study of electronic excitation transport (EET) in native photosystem I particles (200 antenna Chi molecules per P700 reaction center), pump-probe spectroscopy was used to evaluate the dynamics of polarization-rotating EET steps responsible for photobleaching depolarization in the 665-681 nm antenna Chi a absorption region [1]. The measured room temperature depolarization lifetimes ranged from 5 ps at 675 nm to 13 ps at 665 nm. These kinetics are far more rapid than the PSI-200 Chi a antenna EET timescale of 200-400 ps inferred from spectral hole-burning experiments [2], which are limited to temperatures below 10 K due to thermal broadening of zero-phonon hole widths. The question therefore arises as to whether the monitored EET dynamics exhibit marked temperature dependence between 1.6 and 300 K, or whether the time- and frequency-domain spectroscopies view different aspects of photosystem I antenna function.

© 1990 Optical Society of America