Force Spectroscopy of Bacteriorhodopsin Variants

Michael Schranz1, Frank Noll1, and Norbert Hampp1,2

1Faculty of Chemistry, University of Marburg, Hans-Meerwein-Straße, 35032 Marburg, Germany

2Material Science Center Marburg, D-35032 Marburg, Germany




Self-organization of membrane-embedded peptides and proteins cause the formation of lipid mesostructures in the membranes. One example is purple membranes (PM), which consist of lipids and bacteriorhodopsin (BR) as the only protein component. The BR-monomers oligomerize into trimers which form a two dimensional hexagonal crystalline lattice.
The atomic force microscope (AFM) combines a high lateral resolution with the possibility to manipulate single molecules. Single molecule force spectroscopy can be used to unfold single proteins and to obtain structural information by measuring the resulting forces. In this study we used the AFM tip to pull single BR molecules off the purple membrane. Several mutants and laser-modified BR were investigated by AFM-imaging and force spectroscopy.