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

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Abstract
The rotational diffusion of concanavalin A receptors of viable Friend [virus-transformed mouse] erythroleukemia cells and the band 3 anion transport system of human erythrocytes was 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 1 .mu.s time resolution were obtained at concentrations of the eosin probe down to 20 nM and in aqueous media at temperatures of 4.degree.-38.degree. 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 immobile on the time scale of 1-4000 .mu.s at either 4.degree. or 37.degree. C. The technique is applicable to other triplet probes and membrane components of living cells under conditions that do not destroy viability.