Giant Lipid Vesicles designed for Light Energy Transduction

The photosynthetic reaction center (RC) is a transmembrane pigment-protein complex that plays a major role in the photochemical conversion of light into chemical energy in plants, algae and photosynthetic bacteria. It couples light-induced electron transfer to the generation of a proton concentration gradient across a lipid membrane, via reactions involving a quinone molecule that binds two electrons and two protons at its active site. The so-obtained electrochemical gradient can be harnessed to synthesize ATP. In a previous work it has been shown that the reconstitution of functional, but randomly oriented, RC is possible in conventional (diameter 50-100 nm) lipid vesicles typically obtained by the detergent depletion method. In this contribution, we show that following a bottom-up approach and by using the droplet transfer method for giant lipid vesicles (1100 µm) preparation, synthetic protocells, embedding uniformly and physiologically oriented reaction centers, are capable of generating a photo-induced proton gradient across the membrane.