Nucleosome core particle structure and structural changes in solution.

The radius of gyration, Rg, of chicken erythrocyte nucleosome core particles, was found to be 4.56 (+/- 0.07) nm by small-angle X-ray scattering, independent of particle concentration and of NaCl concentration between 0.1 M and 0.6 M-NaCl. The large, positive, second virial coefficient, A2, from particle concentration dependence (but independent of NaCl concentration) in small-angle X-ray scattering may indicate non-electrostatic repulsive ordering over large distances. Density contrast variation in equilibrium sedimentation with a small probe (sucrose) and a larger probe (gamma-cyclodextrin) yields good results for core particle hydration in the first instance, and for an estimate of the total particle volume in the second instance.