Lateral diffusion in binary mixtures of cholesterol and phosphatidylcholines.

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Abstract
The lateral diffusion of a fluorescent-labeled phospholipid, phosphatidyl-N-(4-nitrobenzo-2-oxa-1,3,-diazole)ethanolamine, was measured in binary mixtures of cholesterol and dimyristoyl phosphatidylcholine at temperatures above and below 23.8.degree. C, the chain-melting transition temperature of this phosphatidylcholine. There is a temperature-composition region of approximately temperatures less than 23.degree. C and mol fraction of cholesterol (X) less than 0.20, in which the lateral diffusion coefficient of the fluorescent probe is at least an order of magnitude smaller that it is at points outside this temperature-composition region. At temperatures above .apprxeq. 23.degree. C there is a significant increase in diffusion coefficient with increasing cholesterol concentration, for X > 0.2.