超螺旋对DNA双螺旋扭转角的影响。
The effect of the superhelicity on the double helix twist angle in DNA.
作者信息
Belintsev B N, Gagua A V, Nedospasov S A
出版信息
Nucleic Acids Res. 1979 Mar;6(3):983-92. doi: 10.1093/nar/6.3.983.
An attempt to estimate the relative contributions of twisting and bending to the free energy of superhelix formation from the relaxed DNA is undertaken. The extent of teritiary ordering (number of DNA axis turns tau) and that of secondary ordering (duplex twist angle beta) have been taken as thermodynamical parameters, which characterize the state of the supercoild DNA at the fixed linking number (Lk) value. Such a thermodynamical approach implies the phenomenological parameters of rigidities of twisting and supercoiling (Gbeta, Gtau). Gtau/Gbeta ratio is estimated from the presented experimental data on the winding of the double helix upon increasing the ionic strength when twist alterations are followed by circular dichroism method. The adequacy of such interpretation of CD spectra changes are discussed. The values of Gtau and Gbeta are estimated to be of the same order of magnitude.
我们尝试从松弛的DNA中估算扭转和弯曲对超螺旋形成自由能的相对贡献。三级有序程度（DNA轴的圈数τ）和二级有序程度（双链扭转角β）被用作热力学参数，它们表征了在固定连接数（Lk）值下超螺旋DNA的状态。这种热力学方法涉及扭转和超螺旋刚性的唯象参数（Gβ、Gτ）。当通过圆二色性方法跟踪扭转变化时，根据增加离子强度时双螺旋缠绕的现有实验数据估算Gτ/Gβ比值。讨论了对圆二色光谱变化这种解释的充分性。估计Gτ和Gβ的值处于相同的数量级。
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