ABSTRACT
The rotational mobility of the membrane bound-acetylcholine receptor of the Torpedo electricus electric organ was investigated by phosphorescence depolarization of the erythrosin, the tetraiodo-fluorescein. Phosphorescence anisotropy decay measurement is preferred due to its very favorable life time parameters, having the same correlation time intervals as the molecular motions in most of the biological membranes. Rotational and lateral mobility of molecules has its energetic background in thermal energy. The brief flash of polarized light can create an anisotropic distribution of the unbleached fluorophores. The clustering of integral membrane proteins by physiological or artificial agents provides a greater potential for intercellular crosslinking. Analysis of the whole antibodies reveaied such differences in the rotational modes of the molecules that could be attributed to dimeric or oligomeric distribution of the receptors. The conclusion of the elegant work showed that polarized fluorescence recovery after photobleaching could be applied to study rotational mobility of membrane proteins, using fluorescence probes instead of phosphorescence ones.
