Lasters I, Wyns L, Muyldermans S, Baldwin J P, Poland G A, Nave C
Eur J Biochem. 1985 Sep 2;151(2):283-9. doi: 10.1111/j.1432-1033.1985.tb09098.x.
Fragments of chromatin containing 23 +/- 2.5 nucleosomes have been fractionated after light nuclease treatment of chicken erythrocyte nuclei. Low-angle scattering measures the total z-average radius of gyration of the already well-defined particles and the shape of scatter curves can be compared with three-dimensional analysis as opposed to cross-section analysis of long chromatin fragments. The data show that the particles are not spherical, have no detectable hole in the center of the structure and are best represented by a solid rod-like shape such as that generated by a coil of nucleosomes with the centre perhaps filled with linker DNA and histone H1/H5. 23 nucleosome fragments, where the DNA is partially fragmented, have near-identical scatter curves to the above-defined intact particles, indicating the primary importance of histone proteins in maintaining the integrity of the chromatin higher-order structure. Neutron scattering shows the radii of gyration to be contrast-independent, which fits in with the model calculations for solenoids. Particles with fragmented DNA and the intact particles, therefore, behave as sections of a solenoidal higher-order structure and possibly are observed as "superbeads' only during the folding and unfolding pathways of nucleosome multimers.
在用微球菌核酸酶轻度处理鸡红细胞核后，已分离出含有23±2.5个核小体的染色质片段。小角散射测量已明确界定的颗粒的总z平均回转半径，并且散射曲线的形状可以与三维分析进行比较，这与长染色质片段的横截面分析不同。数据表明，这些颗粒不是球形的，在结构中心没有可检测到的空洞，并且最适合用实心棒状形状来表示，例如由核小体线圈产生的形状，其中心可能填充有连接DNA和组蛋白H1/H5。23个核小体片段（其中DNA部分断裂）具有与上述定义的完整颗粒几乎相同的散射曲线，表明组蛋白在维持染色质高阶结构完整性方面的首要重要性。中子散射表明回转半径与对比度无关，这与螺线管的模型计算相符。因此，具有断裂DNA的颗粒和完整颗粒表现为螺线管高阶结构的片段，并且可能仅在核小体多聚体的折叠和展开途径中被观察为“超级珠”。
