Langmore J P, Schutt C
Nature. 1980 Dec 11;288(5791):620-2. doi: 10.1038/288620a0.
Recently eukaryotic chromosomes have been shown to consist of a repeating subunit, called the nucleosome. Although electron microscopy, neutron scattering and X-ray diffraction have been used to determine the low resolution structure of the nucleosome, these techniques have yielded little information about the disposition of nucleosomes within chromosomes. Electron microscopy has produced many models for chromosome structure based on uniform fibres of 150-500A diameter or on globular 'superbeads. Unfortunately the models are based on microscope images that fail to reveal the strong structural periodicities shown by X-ray scattering to be characteristic of isolated chromatin in solution. Moreover it has not been demonstrated that the chromosomes of living cells are composed of such fibres. We have used low-angle X-ray scattering to investigate the organization of chromosomes in vivo and to account for the previously observed inconsistencies in many X-ray and electron microscope observations. We report here that chicken erythrocytes have a 400 A periodicity due to a nuclear structure that is directly related to the 300 A side-by-side packing of chromosome fibres revealed by electron microscopy of embedded cells, and that this periodicity can be preserved in isolated nuclei provided that the proper buffers are used.
最近发现真核生物染色体由一种名为核小体的重复亚基组成。尽管电子显微镜、中子散射和X射线衍射已被用于确定核小体的低分辨率结构，但这些技术对于染色体内核小体的排列方式提供的信息很少。电子显微镜基于直径为150 - 500埃的均匀纤维或球状“超级珠”产生了许多染色体结构模型。不幸的是，这些模型是基于显微镜图像构建的，而这些图像未能揭示X射线散射所显示的、作为溶液中分离染色质特征的强烈结构周期性。此外，尚未证明活细胞的染色体是由这种纤维组成的。我们利用低角度X射线散射来研究体内染色体的组织，并解释先前在许多X射线和电子显微镜观察中发现的不一致之处。我们在此报告，鸡红细胞具有400埃的周期性，这是由于一种核结构，该结构与通过嵌入细胞的电子显微镜观察所揭示的染色体纤维300埃并排堆积直接相关，并且只要使用合适的缓冲液，这种周期性就能在分离的细胞核中得以保留。
