[Structural heterogeneity of chromatin as revealed by electrophoretic methods].

Electrophoresis of endonuclease-split rat liver chromatin in polyacrylamide and agarose gels of a monotonous concentration revealed different separation patterns. The first pattern exhibited a spectrum of chromatin fragments of discrete sizes, while the second one -- two fractions, i. e. DNP and DNA. The polyacrylamide gel concentration gradient allowed to achieve the best resolution of individual classes of chromation fragments with individual subfractions in sub-, mono- and trinucleosomes. A comparison of micrococcal nuclease-split chromatin fragments of vertebrates revealed nucleosomes of varying sizes. The heterogeneity of the nucleosomes was also found during isotachophoresis and free flow electrophoresis. An analysis of individual subfractions of the mononucleosomes revealed differences in the composition and number of proteins as well as in the kinetics of basic and acidic titration. The chromatin fractions obtained by discontinuous endonucleolysis differed in their composition from the individual subfractions of histones.