SCANNING FORCE MICROSCOPY AT -25-DEGREES-C

Scanning force microscopy (SFM) images of lipid membranes at -25-degre es-C are compared with those at room temperature both in air and in gl ycerol/buffer solution. The results show that at low temperatures memb rane samples can be imaged with less damage, presumably because they b ecome more rigid. Apparent resolution also improves. In glycerol buffe r solution there are pronounced effects on force curves due to viscous drag on the cantilever. Drag coefficients are measured as a function of temperature, and are found to closely follow changes in solution vi scosity. Finally, simple ''freeze fracture'' experiments were performe d on buffer solutions which were frozen between glass coverslips, and then split apart. The images show that at -25-degrees-C the pressure b eneath the SFM tip is sufficient to melt the ice, making detailed imag ing impossible.