Neutron scattering from chromatin in relation to higher-order structure

Abstract

Chromatin fibres containing histone H1 as well as the DNA and histones H2A, H2B, H3 and H4 show the same off-meridional diffraction maxima at ~ 10 nm as reported by Carpenter, Baldwin, Bradbury & Ibel [Nucleic Acids Res.(1976), 3, 1739–1746] for chromatin fibres depleted of histone HI. It is shown that the intensity of the maximum (as a function of solvent scattering-length density and deuteration of histones and DNA) can be quantitatively explained in terms of a globular protein component to the chromatin subunits in a matrix of hydrated DNA. The off-meridional diffraction maximum suggests that the chromatin is in the form of a flat helix and clearly the relative amounts of protein and hydrated DNA vary along the length of the chromatin fibre.