Allen M J, Lee C, Lee J D, Pogany G C, Balooch M, Siekhaus W J, Balhorn R
Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, Livermore, CA 94550.
Chromosoma. 1993 Nov;102(9):623-30. doi: 10.1007/BF00352310.
We have used the atomic force microscope (AFM) to image the surfaces of intact bull, mouse and rat sperm chromatin and partially decondensed mouse sperm chromatin attached to coverglass. High resolution AFM imaging was performed in air and saline using uncoated, unfixed and unstained chromatin. Images of the surfaces of intact chromatin from all three species and of an AFM-dissected bull sperm nucleus have revealed that the DNA is organized into large nodular subunits, which vary in diameter between 50 and 100 nm. Other images of partially decondensed mouse sperm chromatin show that the nodules are arranged along thick fibers that loop out away from the nucleus upon decondensation. These fibers appear to stretch or unravel, generating narrow smooth fibers with thicknesses equivalent to a single DNA-protamine complex. High resolution AFM images of the nodular subunits suggest that they are discrete, ellipsoid-shaped DNA packaging units possibly only one level of packaging above the protamine-DNA complex.
我们使用原子力显微镜（AFM）对完整的公牛、小鼠和大鼠精子染色质以及附着在盖玻片上的部分解聚的小鼠精子染色质的表面进行成像。在空气中和盐溶液中，使用未涂层、未固定和未染色的染色质进行高分辨率AFM成像。来自所有三个物种的完整染色质表面的图像以及一个AFM解剖的公牛精子细胞核的图像显示，DNA被组织成直径在50至100纳米之间变化的大结节亚基。部分解聚的小鼠精子染色质的其他图像表明，这些结节沿着粗纤维排列，在解聚时从细胞核中向外呈环状延伸。这些纤维似乎会伸展或解开，产生厚度相当于单个DNA-鱼精蛋白复合物的狭窄光滑纤维。结节亚基的高分辨率AFM图像表明，它们是离散的、椭圆形的DNA包装单元，可能仅比鱼精蛋白-DNA复合物高一级包装水平。
