Dynamics of bacteriorhodopsin in solid-supported purple membranes studied with tapping-mode atomic force microscopy

Area of Science:

• Biophysics
• Structural Biology
• Materials Science

Background:

• Purple membrane (PM) from Halobacterium salinarum is a model system for studying membrane protein structure and dynamics.
• Previous studies extensively analyzed bacteriorhodopsin (BR) dynamics using diffraction and spectroscopy, but nanoscale dynamical transitions within single PMs remain understudied.

Purpose of the Study:

• To investigate nanoscale dynamical transitions within solid-supported purple membranes.
• To assess the suitability of tapping-mode atomic force microscopy (TM-AFM) for studying these transitions.

Main Methods:

• Tapping-mode atomic force microscopy (TM-AFM) for time-dependent analysis of solid-supported PMs.
• Electrostatic force microscopy (EFM) to complement AFM experiments on PM supported on mica.

Main Results:

• TM-AFM successfully visualized nanoscale dynamical transitions in solid-supported PMs.
• Redistribution processes were observed between a crystalline core (approx. 5 nm height) and a mobile rim region (approx. 4 nm height).
• The influence of temperature and substrate on equilibrium dynamics was investigated.

Conclusions:

• TM-AFM is ideally suited for studying nanoscale dynamical transitions in solid-supported PMs.
• Understanding these dynamical transitions is critical for both fundamental research and applications involving solid-supported membrane assemblies.