Enhancement of fluorescence of pyrene-containing lipids by polar media, detergents and phospholipids

The fluorescence intensities of a medium-chain fatty acid and of several amphiphilic lipids, each containing pyrene in covalent linkage, were enhanced considerably by: 1) Dissolving in mixtures of a polar solvent (e.g. methanol, ethanol, tetrahydrofuran or dimethylsulfoxide) and water; for each individual compound, a certain ratio of solvent to water provided maximal fluorescence intensity. 2) Incorporating into micelles of reduced Triton X-100; an excess of detergent was used so that, statistically, only one molecule of lipid resided in one micelle of the Triton X-100. 3) Incorporating into liposomes of egg phosphatidylcholine; maximal fluorescence was observed using a large excess of phosphatidylcholine. When related to the fluorescence intensities in chloroform/methanol (2:1, by vol.) or water, the enhancement of fluorescence in the above three systems was about 2-6-fold or up to 60-fold, respectively.