Fractionation of chromatin fragments on columns of Biogel A50‐m at different salt concentrations

Nuclease fragmented chromatin was chromatographed on Biogel at various NaCl concentrations. The yield of eluted chromatin, and its H1/core histone ratio was minimal at 0.18 M NaCl where the ratio of H1 subtypes H1c/H1ab was maximal. Therefore, the eluted material was aggregation-resistant chromatin while aggregatable chromatin remained on the columns. Previous results were interpreted as H1 depletion of chromatin by ion-exchange properties of Biogel, but the primary phenomenon is now seen as a separation of classes of chromatin that differ in sensitivity to salt-induced aggregation. At very low salt concentrations, Biogel chromatography can be used without concern for H1 depletion.