Song L, Schurr J M
Department of Chemistry, University of Washington, Seattle 98195.
Biopolymers. 1990;30(3-4):229-37. doi: 10.1002/bip.360300302.
Rapidly relaxing components in the decay of the transient electric dichroism of DNA restriction fragments were reported by Diekmann et al. [(1982) Biophys. Chem. 15, 263-270] and Pörschke et al. [(1987) Biopolymers 26, 1971-1974]. These are analyzed using a new normal mode theory for weakly bending rods and assigned to bending. The longest bending relaxation times for fragments with 95-250 base pairs coincide with the theoretical curve calculated for a dynamic bending rigidity corresponding to a dynamic persistence length Pd = 2100 A. Analysis of the relative amplitudes of fast and slow components following weak orienting pulses is also consistent with a rather large dynamic persistence length. The enhancement of the relative amplitude of the fast component in large electric fields is attributed to steady-state bending of initially perpendicular DNAs by the field. Several reasons are proposed why the dynamic bending rigidity is 4 times larger than the apparent static bending rigidity inferred from equilibrium persistence length measurements on the same fragments.
迪特曼等人[（1982年）《生物物理化学》15卷，263 - 270页]和波施克等人[（1987年）《生物聚合物》26卷，1971 - 1974页]报道了DNA限制片段瞬态电二色性衰减中的快速弛豫成分。利用一种针对弱弯曲杆的新的简正模式理论对这些成分进行了分析，并将其归因于弯曲。具有95 - 250个碱基对的片段的最长弯曲弛豫时间与根据对应于动态持久长度Pd = 2100 Å的动态弯曲刚度计算出的理论曲线相符。对弱取向脉冲后快、慢成分相对振幅的分析也与相当大的动态持久长度一致。大电场中快成分相对振幅的增强归因于电场对初始垂直DNA的稳态弯曲。文中提出了几个原因来解释为什么动态弯曲刚度比从对相同片段的平衡持久长度测量推断出的表观静态弯曲刚度大4倍。
