The removal of "nucleic acid" from an antigen present in the livers of chickens with erythroblastosis.

The recovery of viral antigen in a pure form from tissue can be hindered by the small amount of antigen present relative to the remaining normal tissue constituents with which the antigen may form loose associations. An antigen from the livers of chickens with erythroblastosis had earlier seemed to be associated with nucleic acid. The present work suggests that this material, which reacts with reagents for DNA and RNA but is soluble in 0.2N HClO4, is only a contaminant and not an integral part required for complete activity of the antigen. Treatment with 0.2N HClO4, together with precipitation of the active protein by 60% saturation of aqueous solutions with ammonium sulphate, removes the nucleic acid without destroying antigenicity. The procedure results in a marked degree of purification of the antigen (732-fold with respect to original liver protein) but contaminants still remain. A contaminant absorbing at 260 nm resisting extraction with 0.2N HClO4, can be partly eliminated if the solution is treated with ether-alcohol to remove lipid.