Electron microscopy of turnip yellow mosaic virus and the associated abnormal protein

Methods are described for the purification and separation of the virus nucleoprotein and of the associated abnormal protein found in plants infected with turnip yellow mosaic virus. The methods consist of the use of a butanolchloroform fractionation procedure for the isolation and concentration of the virus nucleoprotein and the use of density gradient centrifugation for the separation of the abnormal protein from the virus nucleoprotein of purified mixtures obtained by the use of either an ethanol-ammonium sulfate or an ethanol-differential centrifugation procedure. The virus nucleoprotein contained 34% ribonucleic acid and was infectious at a concentration of 4 × 10⁻⁶ mg per ml. The abnormal protein contained no nucleic acid and was not infectious at a concentration of 1 mg per ml.Electron micrographs of both preparations which were air dried from ammonium acetate revealed pronounced differences between the two components. Particles of the virus nucleoprotein remained rigid and were nearly spherical in shape with a diameter of 26 mμ while those of the abnormal protein were flattened and had diameters up to 36 mμ, or were clumped together and retained the 26 mμ diameter but were dimpled.