Saturation transfer EPR studies of slow rotational motion in membranes

Saturation transfer spectroscopy is a nonlinear electron paramagnetic resonance method for detecting rotational diffusion of nitroxide spin labels on the microsecond timescale or slower. Various results on spin-labeled biological membranes are reviewed here. These studies include those on lipid motions in gel-phase phospholipid bilayers, on the dynamics of lipid-protein interactions, and on the rotational diffusion of spin-labeled transmembrane proteins. Certain methodological aspects are also discussed.