FIG. 4.

Isolation of IMV and wrapped viruses. RK13 cells were infected with the indicated viruses at a MOI of 10. Infected cells were labeled with 500 μCi of a mixture of [³⁵S]methionine and [³⁵S]cystein from 4 to 18 h after infection. Particles in the cell lysates and medium were concentrated by sedimentation through a sucrose cushion, applied to a CsCl density gradient, centrifuged, and fractionated. The amount of radioactivity in the fractions was determined by scintillation counting.