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Published November 2016 | Published + Submitted
Journal Article Open

"Parking-garage" structures in nuclear astrophysics and cellular biophysics

Abstract

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.

Additional Information

© 2016 American Physical Society. Received 28 August 2015; revised manuscript received 6 July 2016; published 1 November 2016. We thank G. Ortiz and S. Setayeshgar for helpful comments. Part of this work was completed at the Aspen Center for Physics, which is supported by National Science Foundation Grant No. PHY-1066293. This research was supported in part by DOE Grants No. DE-FG02-87ER40365 (Indiana University) and No. DE-SC0008808 (NUCLEI SciDAC Collaboration), and NSF Grant No. PHY11-25915 (KITP, UCSB). Computer time was provided by the INCITE program. This research used resources of the Oak Ridge Leadership Computing Facility located at Oak Ridge National Laboratory, which was supported by the Office of Science of the Department of Energy under Contract No. DEAC05-00OR22725.

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Published - PhysRevC.94.055801.pdf

Submitted - 1509.00410v1.pdf

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