Abstract
Extracts of rabies-infected suckling mouse brains purified by precipitation at pH 4.5, freed from smaller antigens by sedimentation at 161, 180g and digested with RNase, DNase and trypsin show in the ultracentrifuge a component of S20 16 to 18 which is lacking in extracts of normal suckling mouse brains similarly treated. The largest rabies soluble antigen (outer antigen: Mead, 1962b) has a sedimentation constant S20 16 estimated by the biological method of Polson & van Regenmortel (1961). The purified antigen appears to consist of rings or possibly single-turn helices about 100 Å in diameter containing about 0.57 µg. pentose (as ribose) per µg. total nitrogen. The antigen also appears to contain deoxypentose. It is resistant to pancreatic RNase, DNase, trypsin and chymotrypsin, has a density of about 1.34 g./cm3. in CsCl and an electrophoretic mobility about 7/8 that of rabbit serum albumin at pH 8.5.
Preparative density-gradient centrifugation in the analytical rotor of the Model E Spinco centrifuge is described. This allows the method to be applied to smaller particles than can be treated in the S.W. 39 rotor.