Fulmer A W, Bloomfield V A
Biochemistry. 1982 Mar 2;21(5):985-92. doi: 10.1021/bi00534a025.
Bulk chromatin fragments were excised from chicken erythrocyte nuclei by digestion with micrococcal nuclease. Fractionation into S chromatin (soluble at physiological ionic strengths) and I chromatin (insoluble at physiological ionic strengths) was achieved by dialysis against buffers containing 0.15 M NaCl. The effects of NaCl concentration on the molecular dimensions of S and I chromatins were determined by dynamic and static light scattering. Series of fragment lengths were obtained by gel filtration of S and I chromatins under ionic conditions which lead to maximal intramolecular compaction. Hydrodynamic radii and radii of gyration were determined for fragment lengths ranging from 8 to 53 nucleosomes. These data are in excellent agreement with calculations for extended helical structures. Close-packed solenoidal or superbead structures are not compatible with these data. Comparisons of molecular dimensions derived from light scattering and electron microscopy indicate that considerable shrinkage of chromatin fragments can occur when common methods of sample preparation are used for microscopy.
通过用微球菌核酸酶消化从鸡红细胞核中切下大量染色质片段。通过在含有0.15M NaCl的缓冲液中透析，将其分离为S染色质（在生理离子强度下可溶）和I染色质（在生理离子强度下不溶）。通过动态和静态光散射测定NaCl浓度对S和I染色质分子尺寸的影响。在导致最大分子内压缩的离子条件下，通过S和I染色质的凝胶过滤获得一系列片段长度。测定了长度范围为8至53个核小体的片段的流体动力学半径和回转半径。这些数据与扩展螺旋结构的计算结果非常吻合。紧密堆积的螺线管或超珠结构与这些数据不相符。来自光散射和电子显微镜的分子尺寸比较表明，当使用常规样品制备方法进行显微镜观察时，染色质片段可能会发生相当大的收缩。
