Probing protein-protein interactions in real time

We have used a prototype small cantilever atomic force microscope to observ e, in real time, the interactions between individual protein molecules. In particular, we have observed individual molecules of the chaperonin protein GroES binding to and then dissociating from individual GroEL proteins, whi ch were immobilized on a mica support. This work suggests that the small ca ntilever atomic force microscope is a useful tool for studying protein dyna mics at the single molecule level.