ATOMIC-FORCE MICROSCOPY OF A HYDROPHOBIN PROTEIN FROM THE EDIBLE MUSHROOM AGARICUS-BISPORUS

Atomic force microscopy (AFM) has been used to study the fungal hydrop hobin protein HYPA produced by the mushroom Agaricus bisporus. The pro tein was adsorbed from dilute solution onto highly oriented pyrolytic graphite (HOPG), a hydrophobic and atomically flat substrate, and the resulting self-assembled layers were imaged under n-butanol. The natur e of the self-assembled layer was found to be influenced by the protei n concentration in the solution. At relatively high protein concentrat ions (20 mu g mL(-1)) the monolayer formed contained randomly oriented protein molecules. However, at lower protein concentrations (2 mu g m L(-1)) a highly ordered monolayer was formed with a higher level of su rface coverage. The protein molecules appear to assemble end-to-end to form short rods with an average length of 80 nm, The thickness of the ordered monolayer is uniform and around 3.6 nm, Finally, the effect o f washing the adsorbed protein layers with solutions of sodium dodecyl sulphate, leading to partial removal of the HYPA monolayer and bilaye r formation, and of washing with trifluoroacetic acid which strongly d isrupts the adsorbed monolayer, were also examined. (C) 1998 Academic Press.