Monolayer and atomic force microscopy studies of nicotinic acetylcholine receptor films

The surface pressure-area and surface potential-area isotherms for the nicotinic acetylcholine receptor (nAChR) and several lipid-protein monolayers are reported. It was shown that buffer composition and pH affect the film isotherm; the addition of unsaturated lipid and cholesterol to the native protein film contributes to the fluid phase of the monolayer. Langmuir-Blodgett (LB) films of the lipid and lipid-protein monolayers transferred to silicon substrates were imaged using atomic force microscopy (AFM). The AFM images of lipid films show regular structure in the lipid layer and indicate protein aggregates in the AChR-lipid LB films, with feature sizes corresponding to the lipid and receptor molecular dimensions.