Chlorophylls attached to lipid and protein globules, absorption and fluorescence spectra, photo-oxidation

The precipitation of chlorophylls upon lipid and protein globules suspended in an aqueous buffer yields a partial model of photosynthetic membranes. The absorption and fluorescence spectra of the model are investigated as well as the photo‐oxidation of the chlorophylls (bleaching) by dissolved oxygen. It is shown that pigment –pigment interactions occur in such systems, by (a) the appearance of absorption bands characteristic of crystalline or highly ordered chlorophyll at high pigment concentrations, (b) the chlorophyll a‐type of fluorescence of systems containing chlorophyll a and chlorophyll b where the latter is selectively excited, and (c) the kinetics of photo‐oxidation which suggest that chlorophylls can only be bleached when they are dimerized.