Homologous Cholinergic Fluorescent Probes. Synthesis and Fluorescence Properties

The advantages of using specifically designed fluorescent molecules to probe ligand binding sites on proteins, have been recognised [1]. Cholinesterases [2-4], acetylcholine receptor rich fragments from Torpedo marmorata[5,6] and an acetylcholine binding lipoprotein [7] have been studied using fluorescent trialkylammonium ligands. In these investigations, the probes incorporated an ethane [7] or propane bridge [3,5] between the fluorescent dansyl group and the trimethylammonium moiety. During the course of studies of cholinergic ligand binding to mammalian cell plasma membranes, we became aware of the need for developing cholinergie fluorescent probes with increased lipid solubility and higher binding affinities