Preparation of a highly purified surface membrane fraction from rabbit polymorphonuclear leucocytes by high-voltage free-flow electrophoresis.

A surface membrane fraction of high purity and good yield has been prepared from homogenates of rabbit peritoneal polymorphonuclear leucocytes, using a preliminary sorbitol density gradient sedimentation followed by preparative high voltage electrophoresis in a thin flowing buffer film. Enrichment values for the plasma membrane marker enzyme 5'-nucleotidase and 125I-labelled Lens culinaris lectin, after the latter had been applied at the whole cell level, were 18-fold and 6-fold, respectively. Contamination of the surface membrane fraction by other organelles was negligible and approximately 1 mg of surface membrane protein can be obtained from 2 . 10(9) leucocytes. A triacylglycerol-rich, protein-poor fraction that lacks any definable structure in electron microscopy separates discretely from the surface membrane vesicles during electrophoresis. It is considered that this may be a contaminant not previously recognized as present in membrane fractions prepared by more conventional procedures.