Properties of Components Obtained by Treatment of Semliki Forest Virus with Tween 80 and Tri(n-butyl)phosphate

Purified Semliki Forest virus was analysed by analytical sedimentation, rate zonal sedimentation, isopycnic sedimentation, polyaerylamide g l electrophoresis and electron microscopy. It was found that the spherical virus particles had a sedimentation coefficient of 241 S (249 S determined by rate zonal sedimentation), and a buoyant density in sucrose of I.I 90 g/ml; one protein and one glycoprotein were present in the virus; after fixation and negative staining with phosphotungstic acid the diameter of the particles was measured to be 50 to 56 nm. Treatment of Semliki Forest virus with o.I ~ Tween 80 and t ~ tri(n-butyl)phosphate (TNBP) for I h at 4 °C destroyed infectivity and resulted in the appearance ofthe following haemagglutinating and immunizing virus components. (~) A spherical 2II S (217 S) component, 69 to 75 nm in diameter, consisting of an envelope and a core; one protein and one glycoprotein were present; he [nH]-uridine: [~4C)-protein ratio was 2.8-fold higher than that of double-labelled untreated virus. (2) A spherical component, 7 ° to 73 nm in diameter, consisting of the virus envelope lacking intact cores; s20, ~ = I40 S (153 S); one glycoprotein was detected; the [aH]-uridine: [14C]-protein ratio was about I/3 of untreated virus. (3) A 135 S component. (4) Structures assumed to represent envelope fragments; much of them had a sedimentation coefficient of 49 S. It was concluded from experiments with [aH]-uridine-[14C]-amino acids double-labelled and [~4C]-stearic a id-labelled virus that Tween 8o-TNBP dissociates lipids and some protein components from the virus