Concentration of Wound Tumor Virus Determined from Absorbance of the RNA of Virus Collected on Filters

Abstract

Counts of purified wound tumor virus (WTV) particles in an electron microscope were correlated with the UV absorbance of their extracted RNA. The regression equation for the correlation is C = (0.935 .+-. 0.0146) A + (0.012 .+-. 0.0049) where C = number of virions (.times. 10-12)/ml and A = absorbance at a wavelength of 258 nm. The purified virus, which has a diameter of .apprx. 70 nm, was collected from solution onto Millipore filters with an average pore diameter of 50 nm. The RNA was extracted by placing the filter with its virus deposit in 2 ml of 1 N HCl and maintaining the preparation at 24-30.degree. C for 20-24 h. Accurate WTV-RNA readings could be made on virus from 2-g samples of tumors [from sweet clover] when such filters were used to collect the virus, whereas with samples 7 times larger, less than half the WTV-RNA was recovered when virus was collected by centrifugation into a pellet.