Marion C, Roux B
Nucleic Acids Res. 1978 Nov;5(11):4431-49. doi: 10.1093/nar/5.11.4431.
The spatial arrangement of nucleosomes in rat liver chromatin has been examined using the electric birefringence technique. All chromatin subunits studied (up to 9 consecutive nucleosomes) contain their full complement of the five histone types associated with about 200 base pairs repeat length DNA. From the relaxation times and the orientation mechanisms, the nucleosome may be assimilated to an oblate ellipsoid of dimensions about 140 x 140 x 70 A, and the DNA superhelical axis is parallel to its shorter axis. The most important result is a sharp transition in the electro-optical properties of subunits when the number of nucleosomes in the chain is greater than 6 : the initial negative birefringence, as for DNA, becomes positive and the relaxation time is multiplied by ten. The hexanucleosome, which presents no birefringence, has an helical symmetrical structure without preferential orientation axis. This structure is approximatively spherical of about 250 A diameter and the chromatin appears as a periodic array of such a structure.
利用电双折射技术研究了大鼠肝脏染色质中核小体的空间排列。所有研究的染色质亚基(多达9个连续的核小体)都包含与约200个碱基对重复长度的DNA相关的五种组蛋白的完整互补物。根据弛豫时间和取向机制,核小体可被视为尺寸约为140×140×70埃的扁椭球体,DNA超螺旋轴与其短轴平行。最重要的结果是,当链中核小体的数量大于6时,亚基的电光性质会发生急剧转变:与DNA一样,最初的负双折射变为正双折射,弛豫时间乘以10。没有双折射的六核小体具有螺旋对称结构,没有优先取向轴。这种结构近似为直径约250埃的球形,染色质表现为这种结构的周期性阵列。