Sartori Blanc N, Senn A, Leforestier A, Livolant F, Dubochet J
Laboratoire d'Analyse ultrastructurale, Université de Lausanne, Bâtiment Biologie, Lausanne, CH-1015, Switzerland.
J Struct Biol. 2001 Apr;134(1):76-81. doi: 10.1006/jsbi.2001.4365.
In human and other mammal sperm nuclei, DNA is packed in a highly condensed state, the structure of which remains unsolved. Cryoelectron microscopy of vitrified sections provides a first direct view of the local arrangement of the nucleoprotamine filament. DNA aligns in parallel in layers and its orientation rotates along a single-twist direction as in a cholesteric liquid crystal. The structure contains numerous defects, which introduce locally double-twist configurations. Destruction of the SS bonds with dithiotrehitol relaxes the twist and favors the extension of the hexagonal close packing of the filaments, though keeping constant their interfilament distance.
在人类和其他哺乳动物的精子细胞核中，DNA以高度浓缩的状态存在，其结构仍未得到解决。玻璃化切片的冷冻电子显微镜提供了鱼精蛋白细丝局部排列的首个直接视图。DNA分层平行排列，其方向如同胆甾型液晶一样沿着单螺旋方向旋转。该结构包含大量缺陷，这些缺陷会引入局部双螺旋构型。用二硫苏糖醇破坏二硫键会使螺旋松弛，并有利于细丝六边形紧密堆积的延伸，尽管细丝间距离保持不变。
