Sedimentation properties of the scrapie agent.

The sedimentation behavior of the scrapie agent in homogenates of spleen from infected mice has been determined. Approximately 90% of the scrapie agent was sedimented at an omega2t value of 3 X 10(10) rad2/sec in a fixed-angle rotor. Sedimentation of the agent was not substantially affected by sonication or by treatment with the detergent sodium deoxycholate. The sedimentation profiles of the scrapie agent were similar to those observed for free polyribosomes, but differed from those exhibited by five other subcellular markers. Comparative studies showed that the sedimentation profiles of subcellular markers in spleen suspensions from mice infected with scrapie did not differ from uninoculated controls. These studies suggest that the scrapie agent is a discrete infectious particle which should be separable from cellular membranes.