Synaptic membranes from Torpedo marmorata electric organ. 1. Separation and analysis of nicotinic acetylcholine receptor- and acetylcholinesterase-containing membrane vesicles using aqueous two-phase systems.

Two-phase systems consisting of water, dextran and poly(ethylene glycol) have been used for partition of membranes obtained from Torpedo marmorata electric organ. The partition behaviour of the membranes could be adjusted by using a polymer with covalently-bound charged groups. By using this method, the membranes were divided into several fractions which were analyzed for nicotinic acetylcholine receptor and acetylcholinesterase content. It was found that nicotinic receptor-enriched membranes were separated from those containing esterase in a single partition step. Receptor-enriched membranes obtained by gradient centrifugation could be further separated into two receptor fractions by the two-phase technique. The results also reveal at least two types of acetylcholinesterase-rich membranes.