Fundamental biological processes such as intercellular commu-

nication, molecular transport, signal transduction, and energy

conversion are performed by membrane proteins. These important

proteins are best studied in their native environment, the lipid

bilayer. The capability of the atomic force microscope (AFM) to

analyze samples that are in an aqueous state makes this device ideal

for use in determining the native surface structure, supramolecular

organization, conformational changes, and dynamics of membrane-

embedded proteins under near-physiological conditions. Equally

important is the fact that membrane proteins can be imaged

at nanometer resolution and at the single-molecule level with

AFM, as was explicitly explained with AFM studies of the subunit

organization of membrane receptors in chapter 11. This chapter

focuses on how AFM techniques have been utilized to study

membrane protein dynamics in solution with a view to gaining a

better understanding of the conformational changes of receptors

and ion pumps.