Photo-Current and TEM Imaging Characterization of Light-Gated Ion Pump Proteins in Lipid Membranes

Abstract

We report our study on TEM imaging, and photocurrent characterization of two photosynthetic proteins, Bacteriorhodopsin (BR), and Halorhodopsin (HR), which act as light-gated ion pumps. Bacteriorhodopsin acts as a proton (H+) pump, and Halorhodopsin as a chloride ion (Cl-) pump. Both proteins are reconstituted in nano-bilayer membranes supported by Teflon and silicon-based substrates. When a beam of green or blue light shines on the membranes, it induces ion (H+ or Cl-) transport, which is measurable as a photocurrent. We measure how the photocurrent generated by BR and HR changes as a function of their concentration in the membranes and cross-membrane potential. Furthermore, we take TEM images of the membranes with BR and HR reconstituted, to characterize the structure and the density of the proteins in the lipid membranes. The relationship between these structures and the generated photocurrent will also be discussed.