Yang Z, Haijun Z, Zhong-Can O Y
Institute of Theoretical Physics, Academia Sinica, P.O. Box 2735, Beijing 100080, China.
Biophys J. 2000 Apr;78(4):1979-87. doi: 10.1016/S0006-3495(00)76745-2.
Metropolis Monte Carlo simulation is used to investigate the elasticity of torsionally stressed double-stranded DNA, in which twist and supercoiling are incorporated as a natural result of base-stacking interaction and backbone bending constrained by hydrogen bonds formed between DNA complementary nucleotide bases. Three evident regimes are found in extension versus torsion and force versus extension plots: a low-force regime in which over- and underwound molecules behave similarly under stretching; an intermediate-force regime in which chirality appears for negatively and positively supercoiled DNA and extension of underwound molecule is insensitive to the supercoiling degree of the polymer; and a large-force regime in which plectonemic DNA is fully converted to extended DNA and supercoiled DNA behaves quite like a torsionless molecule. The striking coincidence between theoretic calculations and recent experimental measurement of torsionally stretched DNA (Strick et al., Science. 271:1835, 1996; Biophys. J. 74:2016, 1998) strongly suggests that the interplay between base-stacking interaction and permanent hydrogen-bond constraint takes an important role in understanding the novel properties of elasticity of supercoiled DNA polymer.
metropolis蒙特卡罗模拟用于研究受扭应力的双链DNA的弹性，其中扭曲和超螺旋是碱基堆积相互作用以及由DNA互补核苷酸碱基之间形成的氢键所限制的主链弯曲的自然结果。在伸长与扭转以及力与伸长的关系图中发现了三种明显的状态：低力状态，其中过度缠绕和欠缠绕的分子在拉伸下表现相似；中等力状态，其中负超螺旋和正超螺旋DNA出现手性，欠缠绕分子的伸长对聚合物的超螺旋程度不敏感；高力状态，其中麻花状DNA完全转变为伸展DNA，超螺旋DNA的行为非常类似于无扭转分子。理论计算与最近对受扭拉伸DNA的实验测量结果（Strick等人，《科学》。271:1835, 1996；《生物物理杂志》。74:2016, 1998）之间的惊人巧合强烈表明，碱基堆积相互作用和永久性氢键限制之间的相互作用在理解超螺旋DNA聚合物弹性新特性方面起着重要作用。
