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Abstract
This paper describes the physico-chemical properties of Nodamura virus. The virus infects mice and high yields (107 LD50/mg) were obtained from the muscle tissue. To allow for greater ease and accuracy in analysing the RNA, the virus was labelled by inoculating mice with [32P]-phosphate during the incubation period. Purified virus was obtained from the muscle extracts by ammonium sulphate precipitation, differential ultracentrifuging and sedimentation of the SDS-disrupted virus pellet in a sucrose gradient. The virus particles were 29 nm in diam., sedimented at approximately 135S in sucrose gradients and contained two species of RNA which sedimented at 22S and 15S. These values correspond to mol. wt. of 1.0 and 0.5 × 106. Similar mol. wt. were obtained by polyacrylamide gel electrophoresis. The base ratios of the two RNA species were: 22S: A = 22.4, C = 27.0, G = 27.6, U = 23.0; 15S: A = 24.8, C = 28.2, G = 22.8, U = 24.2. Each RNA had low infectivity in mice but this was enhanced about 100-fold by mixing the two species. The RNAs may be present in two distinct particles since extraction of the 135S peak with phenol gave the 22S RNA alone, whereas phenol-SDS extraction liberated both the 22S and 15S species. Centrifuging in caesium chloride also fractionated the virus into components which contained either the 22S or 15S RNA. Preliminary evidence suggests that there is one major polypeptide, mol. wt. 35 × 103, and two minor polypeptides in the virus.
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