中文摘要：

单个 DNA 分子由的压缩净化嘘用磁性的镊子被学习。当时，压缩率很快增加 hist 一集中从 0.002 ～ 0.2 mmol/L 被增加，并且当集中在 0.2 mmol/L 以外时，浸透。压缩的时间功课是指数的在低嘘一集中。它在高集中成为 sigmoidal。在绑了在 DNA 的 hist 之间的 Cooperativity 被建议为转变负责。hist 在低集中随机被装载到 DNA 上。因为 DNA 的结构的扭转由界限导致了，他们趋于在高集中合作地绑 DNA 嘘变得重叠以便一个的绑定嘘一个人便于其它的绑定。在很大的力量下面，压缩 histone-DNA 建筑群能与一种步尺寸以一种分离方式被破坏类似于 60 nm。但是不能是的 hist 完全剥去 DNA，被 histone 固定的 DNA 的降低的 B-S 转变高原揭示。

英文摘要：

The compaction of single DNA molecules by purified histones is studied using magnetic tweezers. The compaction rate increases rapidly when the histone concentration is increased from 0.002 to 0.2 mmol/L, and saturates when the concentration is beyond 0.2 mmol/L. The time course of compaction is exponential at low histone concentrations. It becomes sigmoidal at high concentrations. Cooperativity between the histones bound to DNA is proposed to be responsible for the transition. The histones are loaded onto DNA randomly at low concentrations. They tend to bind DNA cooperatively at high con-centrations because the structural torsions of DNA induced by the bound histones become overlapping so that the binding of one histone facilitates the binding of others. Under very large forces, the com- pacted histone-DNA complex can be disrupted in a discrete manner with a step size of -60 nm. But the histones cannot be completely stripped off DNA, as is revealed by the lowered B-S transition plateau of the histone-bound DNA.