Fusion of chromatophores from photosynthetic bacteria with a supported lipid layer: characterization of the electric units

Abstract

Direct electrometric measurements of membrane potential changes are a valuable tool for study of vectorial transfer of electrons, protons, and ions. Commonly model membrane systems are created by fusion of lipid/protein vesicles with lipid-coated thin films. We characterized the electric units resulting from this process using chromatophores from the purple bacterium Rhodobacter sphaeroides and either a Mylar film or a planar modified gold electrode as support. Investigation of the shunting activity of the ionophore gramicidin on the flashinduced potential change demonstrates fusion of individual chromatophores to form independent`blisters', which preserve an interior aqueous compartment. Under current^clamp conditions the photovoltage follows the change of the membrane potential of the individual blisters. ß