Removal of the Impurities, Nucleic Acid and Polysaccharide, from Twercijlin Protein* by Florence

By the methods most generally used in the past for the purification of the tuberculin protein nucleic acid and polysaccharide often have not been removed. While in most of the final fractions the nucleic acid content varied from 4 to 8 per cent, in a few cases it was as high as 30 to 40 per cent and in others as low as 0.8 per cent. Such a low figure as the latter, however, could not bc attained at will, and seemed to be dependent upon a low initial nucleic acid concentration in the source material. The polysaccharide content ranged from 3 to 40 per cent. However, the size of the tuberculin reaction produced in many series of tests in man or experimental animals by these preparations was independent of the quantities of nucleic acid and polysaccharide present. Therefore, both of these substances may be considered impurities and should be eliminated, if possible, in the purification of the protein, especially since the presence of the nucleic acid, in particular, modified many of the physicochemical properties of the protein, such as isoelectric point, electrophoretic mobilities, and solubilities.