Minina Elena, Arnold Axel
Institute for Computational Physics, University of Stuttgart, Allmandring 3, 70569 Stuttgart, Germany.
Soft Matter. 2014 Aug 21;10(31):5836-41. doi: 10.1039/c4sm00286e. Epub 2014 Jun 30.
In confinement, overlapping polymers experience entropic segregating forces that tend to demix them. This plays a role during cell replication, where it facilitates the segregation of daughter chromosomes. It has been argued that these forces are strong enough to explain chromosome segregation in elongated bacteria such as E. coli without the need for additional active mechanisms [S. Jun and B. Mulder, Proc. Natl. Acad. Sci. U. S. A., 2006, 103, 12388]. However, entropic segregation can only set in after the initial symmetry has been broken. We demonstrate that the timescale for this induction phase is exponentially growing in the chain length, while the actual segregation time scales only quadratically in the chain length. Thus the induction quickly becomes the dominating, slow process, and makes entropic segregation much less efficient than previously thought. The slow induction might also explain the long delay in chromosome segregation observed in experiments on E. coli.
在受限环境中，相互重叠的聚合物会经历熵驱动的分离力，这种力往往会使它们发生混合。这在细胞复制过程中发挥作用，促进子染色体的分离。有人认为，这些力足够强大，足以解释诸如大肠杆菌等细长细菌中的染色体分离，而无需额外的主动机制[S. Jun和B. Mulder，《美国国家科学院院刊》，2006年，第103卷，第12388页]。然而，熵驱动的分离只有在初始对称性被打破之后才会开始。我们证明，这个诱导阶段的时间尺度随链长呈指数增长，而实际的分离时间尺度仅随链长呈二次方增长。因此，诱导很快成为主导的、缓慢的过程，使得熵驱动的分离比之前认为的效率低得多。这种缓慢的诱导也可能解释了在大肠杆菌实验中观察到的染色体分离的长时间延迟。
