Properties of the Isolated Equine Encephalomyelitis Virus (Eastern Strain)

Abstract

Obtained after 3 cycles of alternate low- and high-speed ultra-centrifugation, the purified substance, dissolved in soln. of 0.1 [image] or greater salt conc., exhibits the homogeneity of a single molecular species in the analytical ultracentrifuge. The protein fraction remaining after lipoid extraction gave positive tests for pentoses and only a weakly positive Schiff test. From 57.5 mg. of the protein fraction, 5.5 mg. of material having the qualitative solubility and general properties of a ribose nucleic acid was obtained. Practically all the P was removed from the protein in this subfraction. It is evident that the behavior and constitution of this virus nucleic acid are similar to those of yeast nucleic acid. By pyknometer measurements on solns. of fully active virus the partial specific volume was 0.839, corresponding to a sp. gr. of 1.19. Molecular stability is at a maximum between pH 7 and 8.5. When the pH is reduced below about 6.5, the virus precipitates, and its infectivity is rapidly lost. At pH levels above about 10.5, the sedimentation constant of the residual large component is greatly diminished. Exposure of the virus to u.-v. light of 2537 A results in inactivation at a rate of the same order of magnitude as that reported for certain bacteria. The purified material studied is specific to the virus-diseased chick embryos. No trace of a similar or related component has been found in repeated studies of normal embryo tissue.