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Summary A particle weight of 8·50 × 106 for encephalomyocarditis virus was derived by combining results from (a), sedimentation velocity measurements on highly purified preparations of virus (0·1 to 5 mg./ml.) in 0·1 m-KCl + 0·02 m-phosphate buffer, pH 8·0, which gave an of 162·3 s, (b), differential sedimentation studies of virus in the same solvent but containing various ratios of D2O to H2O which gave a partial specific volume of 0·678 ml./g., with results from (c), analysis of boundary spreading during low speed centrifugation of dilute virus solutions which led to a diffusion coefficient D 20,w of 1·44 × 10 −7 cm.2/sec. Sedimentation equilibrium studies on similar virus preparations in the same solvent gave a particle weight of 8·52 × 106. This suggested a hydrated particle diameter for the virus of 29·8 nm. and a frictional ratio f/fo of 1·130 which was consistent with that of a hydrated sphere containing 0·29 g. water/g. dry virus.
Burness et al. (1970) studied this question.