Inhibitors and Substrates-Acetylthiocholine iodide, 5,5′-dithiobis(2-nitrobenzoic acid) (Ellman's reagent), dithiothreitol, tacrine (9-amino-1,2,3,4-tetrahydroacridine hydrochloride hydrate), BW284c51, decamethonium, and edrophonium were purchased from Sigma. m-(N,N,N-trimethylammonio)trifluoromethylacetophenone (TFK+) and (−)huperzine A were purchased from Calbiochem. Acrylodan was obtained from Molecular Probes (Eugene, Oreg.). Fasciculin 2 (purified from the venom of Dendroaspis angusticeps) was a gift of Dr. Pascale Marchot (University of Marseille, France). Drs. Yacov Ashani and Bhupendra P. Doctor (Walter Reed Army Research Center, Washington, D.C.) kindly provided 7-((methylethoxy) phosphinyl)-oxyl)-1-methylquinolinium iodide (MEPQ) and procainamide-linked Sepharose CL-4B resin. m-tert-Butyl trifluoromethylacetophenone (TFK+) was synthesized as described (21) and kindly provided by Dr. Daniel Quinn, University of Iowa, Iowa City, Iowa. All other chemicals were of the highest grade commercially available.
