Physical studies of nucleosome assembly

Biochemical, spectroscopic, and hydrodynamic studies were performed on the reconstituted complex of 140 base pair DNA and the arginine-rich histone tetramer (H3/H4)2. The histones bind to DNA in a 1:1 molar ration to form a stable particle which orients in an electric field with a rotational correlation time of 6.3 mus and a limitign reduced dichroism of --0.74. The complex was modeled hydrodynamically as a cylinder of dimensions 450 X 80 X 80 A containing approximately 1.5 superhelical turns. Addition of the lysinerich histones to this complex cause a condensation of the structure and results in physical properties nearly identical with those of a native nucleosomal particle.