Dynamics of Bacteriorhodopsin in Solid-Supported Purple Membranes Studied with Tapping-Mode Atomic Force Microscopy

作者：Schranz Michael; Baumann Roelf Peter; Rhinow Daniel; Hampp Norbert^*

来源：Journal of Physical Chemistry B, 2010, 114(27): 9047-9053.

DOI：10.1021/jp102377c

Purple membrane (PM) from Halobacterium solinarum, which comprises bacteriorhodopsin (BR) and lipids only, has been employed by many groups as a model system to study the structure and dynamics of membrane proteins. Although the conformational dynamics of BR within PM has been extensively analyzed with subnanometer resolution by means of diffraction experiments and spectroscopic methods, as well, structural studies of dynamical transitions within single PMs are rare. In this work, we show that tapping-mode atomic force microscopy (TM-AFM) is ideally suited to study dynamical transitions within solid-supported PMs at the nanoscale. Time-dependent AFM analysis of solid-supported PMs shows that redistribution processes take place between a crystalline core region, featuring a height of similar to 5 nm, and a highly mobile rim region (similar to 4 nm in height). Furthermore, we discuss the influence of temperature and substrate on the equilibrium. The experiments are complemented by electrostatic force microscopy (EFM) of PM on mica. Beyond their importance for many physiological processes, dynamical transitions in biological membranes, as observed in this work, are of critical importance for all methods that make use of solid-supported membrane assemblies, either analytical tools or applications.

• 出版日期2010-7-15