Small angle X-ray scattering of intact and lysing cell nuclei

X-ray scattering at very low angles has been applied to the study of chromatin structure in intact and lying nuclei. From maxima and minima in the very low angle range, higher order or very large structures could be deduced, the existence of which has not been found in isolated chromatin; up to now, such structures could be demonstrated only be electron-micrographs of whole nuclei. A strong maximum at 0.12 nm^?1 or a shoulder at 0.08 nm^?1 is interpreted as a hollow or solid cylinder with diameter ～ 70 nm; however, another possible explanation, a side by side packing of 30 nm solenoids^1–4 with a distance of 52 nm, cannot be excluded. A shoulder at 0.033 nm^?1 leads to the conclusion that an even larger structure exist in interphase nuclei. A slight minimum at 0.2 nm^?1 is in the range where mildly isolated chromatin has its first order minimum. This accounts for a coil diameter ～ 30 nm. While in intact nuclei these characteristics of the scattering curve have only a low intensity (except the maximum at 0.12 nm^?1 lysing nuclei exhibit much more pronounced maxima.