Variation and estimation of the differential absorption coefficient of P-700 in spinach photosystem I preparations

Treatment of spinach Photosystem I particles with detergents induced an apparent blue shift of chlorophyll α at 690 nm in the difference spectrum of P-700. As a consequence of the band shift, the differential absorption coefficient of P-700 was increased from 63 to 87 mM^-1 .cm^-1. A curve was presented, with which changes in the apparent differential absorption coefficient of P-700 can be estimated by measuring magnitudes of light-induced absorption decreases at 680 nm and 700 nm. The curve was compared with that for cyanobacterial preparations and the mechanism of the detergent-induced band shift was discussed.