Conformational changes of DNA in chromatin and the nucleosome sub-unit

Abstract

Conformation of the DNA in a salt-soluble chromatin and in the nucleosome sub-unit was studied in a variety of ionic environments. Precipitation with Mg²⁺ was used as one kind of a probe to indicate the arrangement of the proteins in the complex. Parallel circular dichroic measurements were also made. Three types of DNA conformation have been described: (1) an extended configuration. (2) an intermediate type as observed in the high mol. wt, salt-soluble chromatin and (3) the type seen in the nucleosome sub-unit. Both the chromatin and the nueleosome are pictured as flexible complexes iheir structure being highly dependent on the ionic environment.