DNA toroids: Stages in condensation
DNA toroids: Stages in condensation
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DOI：
10.1021/bi990901o
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发表时间：
1999-10-19
期刊：
影响因子：
2.9
通讯作者：
Hansma, HG
中科院分区：
文献类型：
--
作者：
Golan, R;Pietrasanta, LI;Hansma, HG
用原子力显微镜研究了多聚赖氨酸（PLL）和PLL-脱唾液酸类粘蛋白（AsOR）对DNA缩合的影响。观察到不同类型的浓缩DNA结构，其显示随着环状质粒DNA分子逐渐浓缩而发生的一系列构象变化。其结构范围从具有质粒DNA长度的环状分子到具有类似于未浓缩环状DNA的轮廓长度的1/6至1/8的小环和短杆。6800个碱基对（bp）的单个质粒分子浓缩成中心到中心测量的直径类似于110 nm的单个环形。结果与DNA凝聚模型一致，在该模型中，环状DNA分子多次折叠成逐渐变短的杆状物。环形和棒之间的中间结构表明，至少一些环形可以通过打开棒来形成，如Dunlap等人[（1997）Nucleic Acids Res.25，3095]所提出的。在赖氨酸：核苷酸比率为5：1和6：1时形成环状体和棒状体。这种高赖氨酸：核苷酸的比例进行了讨论，熵的考虑和大离子的过度充电。PLL-AsOR比单独的PLL更有效地浓缩DNA，因为几个PLL分子连接到单个AsOR分子上，导致阳离子密度增加。
The effects of polylysine (PLL) and PLL-asialoorosomucoid (AsOR) on DNA condensation have been analyzed by AFM. Different types of condensed DNA structures were observed, which show a sequence of conformational changes as circular plasmid DNA molecules condense progressively. The structures range from circular molecules with the length of the plasmid DNA to small toroids and short rods with similar to 1/6 to 1/8 the contour length of the uncondensed circular DNA. Single plasmid molecules of 6800 base pairs (bp) condense into single toroids of similar to 110 nm diameter, measured center-to-center. The results are consistent with a model for DNA condensation in which circular DNA molecules fold several times into progressively shorter rods. Structures intermediate between toroids and rods suggest that at least some toroids may form by the opening up of rods as proposed by Dunlap et al. [(1997) Nucleic Acids Res. 25, 3095]. Toroids and rods formed at lysine:nucleotide ratios of 5:1 and 6:1. This high lysine: nucleotide ratio is discussed in relation to entropic considerations and the overcharging of macroions. PLL-AsOR is much more effective than PLL alone for condensing DNA, because several PLL molecules are attached to a single AsOR molecule, resulting in an increased cation density.