A striking shape was recently observed for the endoplasmic reticulum, a cellular organelle consisting of stacked sheets connected by helical ramps [Terasaki et al., Cell 154, 285 (2013)]. This shape is interesting both for its biological function, to synthesize proteins using an increased surface area for ribosome factories, and its geometric properties that may be insensitive to details of the microscopic interactions. In the present work, we find very similar shapes in our molecular dynamics simulations of the nuclear pasta phases of dense nuclear matter that are expected deep in the crust of neutron stars. There are dramatic differences between nuclear pasta and terrestrial cell biology. Nuclear pasta is 14 orders of magnitude denser than the aqueous environs of the cell nucleus and involves strong interactions between protons and neutrons, while cellular-scale biology is dominated by the entropy of water and complex assemblies of biomolecules. Nonetheless, the very similar geometry suggests both systems may have similar coarse-grained dynamics and that the shapes are indeed determined by geometrical considerations, independent of microscopic details. Many of our simulations self-assemble into flat sheets connected by helical ramps. These ramps may impact the thermal and electrical conductivities, viscosity, shear modulus, and breaking strain of neutron star crust. The interaction we use, with Coulomb frustration, may provide a simple model system that reproduces many biologically important shapes.
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机译：最近观察到内质网是一种醒目的形状，内质网是由通过螺旋坡道连接的堆叠的薄片组成的细胞器[Terasaki et al。，Cell 154，285（2013）]。这种形状很有趣，不仅因为其生物学功能，使用增加的核糖体工厂表面积来合成蛋白质，还因为其几何特性对微观相互作用的细节不敏感。在目前的工作中，我们在对中子星壳深处的致密核物质核面食相的分子动力学模拟中发现了非常相似的形状。核面食与陆地细胞生物学之间存在巨大差异。核面食的密度比细胞核的水性环境高14个数量级，并且涉及质子和中子之间的强相互作用，而细胞尺度的生物学则主要由水的熵和生物分子的复杂组装组成。但是，非常相似的几何形状表明两个系统可能具有相似的粗粒度动力学，并且形状确实是由几何考虑因素决定的，而与微观细节无关。我们的许多模拟会自动组装成由螺旋坡道连接的平板。这些斜坡可能会影响中子星外壳的热导率，电导率，粘度，剪切模量和断裂应变。我们使用的相互作用以及库仑的挫败感可能会提供一个简单的模型系统，该模型可以重现许多生物学上重要的形状。
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