Purification and Physical Properties of Mycophage PS 1

Mycophage PS 1, produced by the mould Penicillium stoloniferum, was concentrated and purified by zonal centrifugation or by a combination of isopropanol precipitation and zonal centrifugation. Continuous flow isopycnic banding was accomplished using the K-II zonal centrifuge. Isopropanol precipitates of fermentation broths were further concentrated by continuous flow isopycnic banding in the B-IX rotor followed by rate zonal separation and a second isopycnic banding in the B-XV rotor. Mycophage PS 1 was a potent inducer of interferon. Double-stranded RNA isolated from both the virus-like particle and from the rate zonal gradient also induced interferon. The characters of the double-stranded RNA from both sources were identical.