Chlorophyll–carotenoid complexes as a model for the reaction centre of photosystem I of photosynthesis

Abstract

Mixed monolayers of chlorophyll (chl) and zeaxanthin exhibit large, reversible bathochromic spectral shifts (from 688 to 733 nm) with increasing surface pressure (decreasing intermolecular distance). The absorption spectrum of the monolayer can be made to be similar to that of Photosystem I or II, by varying the mole ratio of chl to carotenoid, surface pressure and type of carotenoid used. There are only minor effects on the absorption spectrum upon compression of monomolecular films of pure chl a or its isomer chl a′, or mixed films of chl and carotenoids that do not contain dihydroxy groups.