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Diphenylhexatriene and pyrene as tools for characterization of biological membranes.

The temperature behaviour of the fluorescent probes--1,6- diphenyl-1,3,5-hexatriene (DPH) and pyrene--in the outer and intracellular membranes differs markedly. Fluorescence polarization of DPH in microsomal preparations of duck salt gland and bovine brain enriched with Na,K-ATPase decreases nonmonotonously with an increase in temperature, the critical temperature being coincident with that for Na,K-ATPase. In preparations of sarcoplasmic reticulum intracellular membranes enriched with Ca-ATPase, the DPH fluorescence polarization changes linearly with temperature. Studies of the lipid composition of membrane preparations demonstrated that intracellular membranes are more fluid than outer plasma membranes. At the same time, these membranes reveal a critical temperature for another parameter that characterizes the changes in the hydrophobic volume of the bilayer, i.e., the degree of pyrene excimerization. The Arrhenius plots for this reaction coincide with that for Ca-ATPase in the same preparations.