Recent advances in site-directed spin labeling of proteins.

Site-directed spin labeling of proteins is experiencing a phase of rapid technical evolution, application and evaluation. New strategies have been introduced for determining membrane protein topography, electrostatic potentials, the orientation of proteins at membrane surfaces and inter-residue distances. New applications include studies of beta strands, structure mapping using spin-spin interactions, domain motions in soluble proteins and extensive structural analysis of a number of membrane and soluble proteins.