Chirally Organized Macrodomains in Thylakoid Membranes. Possible Structural and Regulatory Roles

Abstract

In photosynthesis, the primary step in the conversion of light energy into chemical energy occurs in the reaction centers, which represents only a small fraction of the total pigment content of photosynthetic membranes. Direct excitation of the reaction centers is a very rare event even under strong sunlight. In all photosynthetic organisms the light energy is predominantly captured by antenna pigments. These pigments transfer the excitation energy to the reaction centers that convert the excited state energy to a “stable” charge separation. The reactions concurrent with the trapping of the excitation energy, e.g. fluorescence emission or dissipation of the excitation energy to heat, represent a loss in the photosynthetic utilization of light energy. In chloroplasts, on average for every reaction center, several hundred chlorophyll-a (Chl-a) and b and carotenoid molecules constitute the system of the antenna pigments.