LANGMUIR-BLODGETT STUDIES AND ATOMIC FORCE MICROSCOPE IMAGES OF NICOTINIC ACETYLCHOLINE-RECEPTOR FILMS

Lipid membrane composition, subphase ionic strength, and pH affect the functionality of transmembrane proteins in reconstituted systems. We present the surface pressure-area and surface potential-area curves for nicotinic acetylcholine receptor (nAChR) films and nAChR-lipid films with various lipid compositions and subphase preparations. Addition of unsaturated lipid and cholesterol caused the protein-lipid films to exhibit a more fluid phase under compression than the nAchR film itself. The choice of buffer, as well as pH, also affected film isotherms. Lipid-protein films were transferred onto silicon substrates and atomic force microscope (AFM) images were obtained. Images of the transferred protein and lipid films show the presence of protein aggregates and regular structure in the lipid layer. The sizes of the observed features are consistent with the molecular dimensions of the lipids and nAChR.