Low angle X-ray scattering studies of chromatin in different solvents; analysis by comparison with computer-simulated scattering curves

Low-angle X-ray scattering curves of isolated calf thymus chromatin, dissolved in 0.2 mm EDTA, 0.2 mm MgCl₂ or 0.5 m NaCl, have been analysed by comparison with simulated scattering curves of models from chromatin subunits and higher order structure. The results provided additional data based on established models. Assuming the protein core as a cylinder of 5.9–6.0 nm diameter and 5.9-2.0 nm height, the centre to centre distance of the cores in tightly packed chromatin was found to be 6.7 nm. Computer simulation of X-ray scattering of chromatin was fitted to experimentally derived data for estimating the ratios of quaternary and tertiary structure. Slight differences of the quaternary structures of 0.15 m NaCl adn in 0.2 mm MgCl₂ were observed.