Preparation of purified myelin from ox intradural spinal roots by rate-isopycnic zonal centrifugation

1. 1. Ox peripheral nerve myelin membranes were isolated by rate-isopycnic zonal centrifugation. A method is described for the Beckman size 14 zonal rotor. The isolated membranes had the same isopycnic banding density as 15.2% sucrose (w/w). On the basis of studies with twelve marker enzymes and electron microscopy, at least 99% of the fraction consisted of myelin membranes. The electron micrographs showed the typical myelin lamellar rings and vesicles derived by peeling off from these lamellae. 2. 2. The enzyme, 2′,3′-cyclic nucleotide-3′-phosphohydrolase, reported to be closely associated with central nervous system myelin, was shown not to be associated with the peripheral nerve myelin. 3. 3. A membrane fraction which had the same isopycnic banding density as 17.6% sucrose (w/w) was shown to have high specific activity of 5′-nucleotidase and 2′,3′-cyclic nucleotide-3′-phosphohydrolase. A similar fraction was isolated from ox spinal cord. This fraction of the spinal cord membranes banding at 17.6% (w/w) contained no basic protein. 4. 4. The disc electrophoresis pattern of the peripheral nerve myelin proteins was different from that of the spinal cord myelin