Adhesion forces of mcfp-1 films on mica (A) and on TiO2 (B) as a function of contact time at pH 5.5. D is the distance between two bare surfaces. Open circle – approach, closed circle – separation. The measured force, F/R (normalized by the radius of the surface, R), is denoted in the left ordinate, whereas the corresponding interaction energy per unit area, E, between two flat surfaces, defined by E = F/1.5πR, is on the right. The hard wall corresponds to the thickness of compressed protein film and is indicated by the black arrows (top left corner).