The Binding of Luxol Fast Blue Arn by Various Biological Lipids

Abstract

A determination of the selectivity and approximate stoichiometry of Luxol Fast Blue ARN by known chemical compounds showed that phosphatidyl ethanolamine, phosphatidyl serine, and phosphatidyl inositol bound the dye with an apparently stoichiometric ratio of 1 dye molecule to 2 molecules of lipid. Phosphatidyl choline, sphingomyelin, and palmitic acid showed a much weaker reaction. Of these, phosphatidyl choline bound the least amount of dye; about 1 dye molecule per 13-20 lipid molecules. Glycerides, methyl and cholesteryl esters of fatty acids, cholesterol, cerebrosides, and oleic acid gave negative results, as did a variety of low molecular weight substances, including ethanolamine, choline, inositol, and serine. Such negative results indicate that no isopropanol-insoluble complexes were formed with the dye. The behavior of the dye toward several phospholipids suggests that the phosphate groups are essential to the binding reaction and that the quaternary amine of phosphatidyl choline may interfere with it. The selectivity of the dye-binding reaction and the properties of the dye-phospholipid complexes suggest that this reaction will be useful for cytochemical studies of phospholipids, particularly those of the cell membrane