Preparation of O 2-evolving Photosystem-II subchloroplasts from spinach

Abstract

An O 2-evolving Photosystem II subchloroplast preparation was obtained from spinach chloroplasts, using low concentrations of digitonin and Triton X-100. The preparation showed an O 2 evolution activity equivalent to 20% of the uncoupled rate of fresh broken chloroplasts, but had no significant Photosystem-I-dependent O 2 uptake activity. The preparation showed a chlorophyll a b ratio of 1.9 and a P-700 chlorophyll ratio of 1 2400 . Absorption spectra at room temperature and fluorescence emission spectra of chlorophyll at 77 K suggested a significant decrease in Photosystem I antenna chlorophylls in the O 2-evolving Photosystem II preparation.