A Fractionation of the Histones of Group F2a from Calf Thymus.

1. The calf-thymus histone group F2a has been separated into two subfractions by stepwise precipitation with acetone from acid solution. 2. Carboxymethyl-cellulose and dextran-gel column chromatography and a method involving dialysis against ethanol have also given the subfractions, but the acetone-hydrochloric acid method has proved to be the most practicable. 3. The two subfractions differ significantly in their amino acid composition and in the pattern of peptides obtained by tryptic digestion. Both fractions have a very low content of N-terminal amino acids and contain acetyl groups.