[Models for rotating spin labels and probes in proteins and membranes]

A method of comparative analysis of ESR spectra has been proposed. It allows to distinguish between two models, slow reorientation of spin labels, and rapid rotation of the cone. Comparison of experimental data for a number of biological objects the theoretical predictions has shown that the rotation of nitroxyl fragment of spin labels can be described by the model of slow anisotropic rotation with correlation time 10(-6) less than or equal to tau less than or equal to 10(-8) s in conditions where the rotation of macromolecules is "frozen".