Stable Photosynthetic Complex of Rhodospirillum rubrum in Reverse Micelles

Abstract

Water plays a fundamental role in determining the reaction rates and the thermodynamics of biological systems. However, the way in which water influences catalysis, structure and organization are not completely understood. One approach to resolve this problem is through low water system (water-in-oil-microemulsions) (1,2). The activity of water soluble enzymes, and to a lesser extent membrane proteins, in reverse micelle solutions have been studied extensively (1,2). Reverse micelles allow the possibility of controlling the amount of water available to proteins, organelles and cells housed in their interior (1). Here we have shown how water influences the function and organization of photosynthetic complexes. Although the photosynthetic complexes of spinach thylakoid membranes, and green alga C. reinhardtii can be “solubilized” in various reverse micellar systems (3), only the bacterial photosynthetic complex (BPC) could be transferred either to HTS (Hexadecane-Tween-Span) or PLC (Phospolipid complex) reverse micelles in a stable functional form. Bacteriochlorophyll (BChl) fluorescence induction transients (0JIP) and photo-oxidation of the reaction center, P, measured as 820nm absorption changes (4), have been used to evaluate the photosynthetic capacity of the bacterial reaction center. Subsequently, we have studied the stability of BPC in PLC-liquid preparation and BPC in PLC after immobilizing them in resin. HTS-reverse micellar systems have been used to investigate the effect of water on the primary photosynthetic activity.