Fluorescence studies of the binding of amphiphilic amines with phospholipids.

The binding characteristics of several amine drugs with dispersed phospholipids (phosphatidylcholine, phosphatidylserine, and phosphatidylglycerol) have been studied using the fluorometric method and 1-anilino-8-naphthalene sulfonate and 1,6 diphenyl-1,3,5-hexatriene as fluorescence probes. The results show that amphiphilic amines, such as chlorphentermine, interact with phospholipids via both ionic and hydrophobic forces. The ionic interaction, which occurs between the protonated amine group of the drug and the phosphate oxygen of the lipid, changes the amphiphilic characteristics of the lipid by reducing the number of negative charges on the lipid vesicles, and inhibits the Ca2+-dependent lipid hydrolysis by blocking the Ca2+ binding sites on the lipid vesicles. The hydrophobic interaction, which involves the nonpolar moieties of the drug and the lipid, is of primary importance to the overall drug-lipid binding stability. Drugs without a strong hydrophobic moiety, such as dopamine, do not interact with phospholipids.