Fritzsche W, Schaper A, Jovin T M
Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
Chromosoma. 1994 Jul;103(4):231-6. doi: 10.1007/BF00352247.
With the scanning force microscope (SFM), one can image the topography of biological material adsorbed at air-solid or liquid-solid interfaces with up to nanometer resolution. In principle, fixation, contrast enhancement, and labeling are not required. We have adapted specimen preparation techniques of conventional electron microscopy for visualizing chromatin ultrastructures in the SFM. A beaded substructure of the nucleoprotein filament was obtained after hypotonic lysis of chicken erythrocytes and air drying. The beads-on-a-string morphology of the basic nucleosomal assembly was well delineated. The nucleosomes appeared as round protrusions with an apparent height of 4-6 nm. The histogram of center-to-center distances between adjacent nucleosome cores along the filament axis had a peak at approximately 30 nm. Reversible changes in the three-dimensional structure were observed upon exposure of air-dried samples of metaphase chromosomes to solutions of different ionic strengths.
使用扫描力显微镜（SFM），可以对吸附在气-固或液-固界面的生物材料的形貌进行成像，分辨率可达纳米级。原则上，不需要固定、增强对比度和标记。我们采用了传统电子显微镜的标本制备技术来在SFM中观察染色质超微结构。鸡红细胞经低渗裂解和空气干燥后，获得了核蛋白丝的串珠状亚结构。基本核小体组装的串珠形态得到了很好的描绘。核小体表现为明显高度为4-6纳米的圆形突起。沿细丝轴相邻核小体核心之间的中心距直方图在约30纳米处有一个峰值。将中期染色体的空气干燥样品暴露于不同离子强度的溶液中时，观察到三维结构的可逆变化。
