Schiessel H, Gelbart W M, Bruinsma R
Departments of Physics, University of California, Los Angeles, California 90095, USA.
Biophys J. 2001 Apr;80(4):1940-56. doi: 10.1016/S0006-3495(01)76164-4.
We present a theoretical analysis of the structural and mechanical properties of the 30-nm chromatin fiber. Our study is based on the two-angle model introduced by Woodcock et al. (Woodcock, C. L., S. A. Grigoryev, R. A. Horowitz, and N. Whitaker. 1993. Proc. Natl. Acad. Sci. USA. 90:9021-9025) that describes the chromatin fiber geometry in terms of the entry-exit angle of the nucleosomal DNA and the rotational setting of the neighboring nucleosomes with respect to each other. We analytically explore the different structures that arise from this building principle, and demonstrate that the geometry with the highest density is close to the one found in native chromatin fibers under physiological conditions. On the basis of this model we calculate mechanical properties of the fiber under stretching. We obtain expressions for the stress-strain characteristics that show good agreement with the results of recent stretching experiments (Cui, Y., and C. Bustamante. 2000. Proc. Natl. Acad. Sci. USA. 97:127-132) and computer simulations (Katritch, V., C. Bustamante, and W. K. Olson. 2000. J. Mol. Biol. 295:29-40), and which provide simple physical insights into correlations between the structural and elastic properties of chromatin.
我们对30纳米染色质纤维的结构和力学性质进行了理论分析。我们的研究基于伍德科克等人提出的双角度模型（伍德科克，C.L.，S.A.格里戈里耶夫，R.A.霍洛维茨和N.惠特克。1993年。美国国家科学院院刊。90:9021 - 9025），该模型根据核小体DNA的进出角度以及相邻核小体彼此之间的旋转设置来描述染色质纤维的几何形状。我们通过分析探索了由这一构建原理产生的不同结构，并证明密度最高的几何形状接近在生理条件下天然染色质纤维中发现的形状。基于该模型，我们计算了纤维在拉伸时的力学性质。我们得到了应力 - 应变特性的表达式，这些表达式与最近的拉伸实验结果（崔，Y.，和C.布斯塔曼特。2000年。美国国家科学院院刊。97:127 - 132）以及计算机模拟结果（卡特里奇，V.，C.布斯塔曼特，和W.K.奥尔森。2000年。分子生物学杂志。295:29 - 40）吻合良好，并且为染色质的结构和弹性性质之间的相关性提供了简单的物理见解。
