Rotational diffusion of cell surface components by time-resolved phosphorescence anisotropy.

The rotational diffusion of concanavalin A receptors of viable Friend erythroleukemia cells and the band 3 anion transport system of human erythrocytes has been measured via the time-dependent phosphorescence emission intensity and anisotropy of triplet probes excited by a 5-ns laser pulse. High-quality phosphorescence decay curves with a 10-microseconds time resolution were obtained at concentrations of the eosin probe down to 20 nM and in aqueous media at temperatures of 4-38 degrees C. A strong temperature dependence in the rotational behavior was observed for the band 3 anion transport protein, but the lectin receptors of the Friend erythroleukemia cells were found to be immobile on the time scale of 1-4000 microseconds at either 4 degrees C or 37 degrees C. The technique is applicable to other triplet probes and membrane components of living cells under conditions that do not destroy viability.