Chromatin fibers within the interior of the nucleus of the cell make stable interactions with the nucleoskeleton, an ensemble of 'extra-chromatin' structures which help ensuring genome stability. Although the role of these interactions appears crucial to the correct behavior of the cell, their impact on chromatin structure and dynamics remains to be elucidated. In order to tackle this important issue, in this work we introduce a simple polymer model for chromatin fibers in interphase which takes into account the two generic properties of chain-versus-chain mutual uncrossability and the presence of stable binding interactions to an extra-chromatin nuclear matrix. To study how these constraints affect chromatin structure from small to large scales, we employ extensive molecular dynamics computer simulations and we monitor the motion of nanoprobes of different sizes embedded within the polymer medium. Our results demonstrate that nanoprobes show hampered motion whenever their linear size becomes larger than chromatin stiffness. This transition is also displaying features which usually belong to the realm of glassy systems, namely long-tail correlations in the distribution functions of nanoprobe spatial displacements and heterogeneous behavior accompanied by ergodicity breaking.

中文翻译：

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具有空间限制的相间染色体的微流变学：一项计算研究。

细胞核内部的染色质纤维与核骨架形成稳定的相互作用，核骨架是“染色质外”结构的集合，有助于确保基因组的稳定性。尽管这些相互作用的作用对于细胞的正确行为至关重要，但它们对染色质结构和动力学的影响仍有待阐明。为了解决这个重要问题，在这项工作中，我们引入了一个相间染色质纤维的简单聚合物模型，其中考虑了链对链相互不可交叉性的两个通用属性以及与染色质外染色质的稳定结合相互作用核基质。要研究这些限制因素如何从小到大影响染色质结构，我们采用广泛的分子动力学计算机模拟，并监测嵌入聚合物介质中的不同尺寸纳米探针的运动。我们的结果表明，只要纳米探针的线性尺寸大于染色质刚度，它们就会显示出受阻的运动。这种转变也显示出通常属于玻璃态系统领域的特征，即纳米探针空间位移的分布函数的长尾相关性以及伴随着遍历性破坏的异质行为。