SEDL / STP / STP863-EB / STP32769S

Global and Nonglobal Rotations in Proteins Detected by Fluorescence Polarization

Chen, RF
Medical officer and biologist, National Heart, Lung, and Blood Institute, Bethesda, MD

Scott, CH
Medical officer and biologist, National Heart, Lung, and Blood Institute, Bethesda, MD

Pages: 14    Published: Jan 1985

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Abstract

Fluorescence polarization methods have been used to assess protein motion for about three decades. These methods are still evolving, but basically can be divided into three classes: (1) steady state methods, (2) time-resolved anisotropy measurement, and (3) differential polarized phase fluorometry. A brief overview of these methods is given, and data are presented on proteins that are unlabeled, or conjugated with dansyl (1-dimethylaminonaphthalene-5-sulfonyl) group. The experiments show that the dansyl label exhibits a fast thermally activated motion, which is viscosity independent, as well as a slower motion characteristic of the global rotation of the protein as a whole. Data on the intrinsic ultraviolet fluorescence of proteins show that the global rotation rate can be obtained from steady state data, which also can detect independent motion of the tryptophan residues. Time-resolved anisotropy data are presented showing directly the rapid rotation of the dansyl group. These data illustrate the ease with which polarization data detect global and nonglobal rotations in proteins.