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Anisotropic shock responses of nanoporous Al by molecular dynamics simulations.

ABSTRACT: Mechanical responses of nanoporous aluminum samples under shock in different crystallographic orientations (<100>, <111>, <110>, <112> and <130>) are investigated by molecular dynamics simulations. The shape evolution of void during collapse is found to have no relationship with the shock orientation. Void collapse rate and dislocation activities at the void surface are found to strongly dependent on the shock orientation. For a relatively weaker shock, void collapses fastest when shocked along the <100> orientation; while for a relatively stronger shock, void collapses fastest in the <110> orientation. The dislocation nucleation position is strongly depended on the impacting crystallographic orientation. A theory based on resolved shear stress is used to explain which slip planes the earliest-appearing dislocations prefer to nucleate on under different shock orientations.

SUBMITTER: Tian X

PROVIDER: S-EPMC7968703 | biostudies-literature | 2021

REPOSITORIES: biostudies-literature

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Anisotropic shock responses of nanoporous Al by molecular dynamics simulations.

Tian Xia X Ma Kaipeng K Ji Guangyu G Cui Junzhi J Liao Yi Y Xiang Meizhen M

PloS one 20210317 3

Mechanical responses of nanoporous aluminum samples under shock in different crystallographic orientations (<100>, <111>, <110>, <112> and <130>) are investigated by molecular dynamics simulations. The shape evolution of void during collapse is found to have no relationship with the shock orientation. Void collapse rate and dislocation activities at the void surface are found to strongly dependent on the shock orientation. For a relatively weaker shock, void collapses fastest when shocked along ...[more]

PMID: 33730074

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Project description:The small heat shock proteins (sHSPs) are a virtually ubiquitous and diverse group of molecular chaperones that can bind and protect unfolding proteins from irreversible aggregation. It has been suggested that intrinsic disorder of the N-terminal arm (NTA) of sHSPs is important for substrate recognition. To investigate conformations of the NTA that could recognize substrates we performed replica exchange molecular dynamics simulations. Behavior at normal and stress temperatures of the dimeric building blocks of dodecameric HSPs from wheat (Ta16.9) and pea (Ps18.1) were compared because they display high sequence similarity, but Ps18.1 is more efficient in binding specific substrates. In our simulations, the NTAs of the dimer are flexible and dynamic; however, rather than exhibiting highly extended conformations they retain considerable α-helical character and contacts with the conserved α-crystallin domain (ACD). Network analysis and clustering methods reveal that there are two major conformational forms designated either "open" or "closed" based on the relative position of the two NTAs and their hydrophobic solvent accessible surface area. The equilibrium constant for the closed to open transition is significantly different for Ta16.9 and Ps18.1, with the latter showing more open conformations at elevated temperature correlated with its more effective chaperone activity. In addition, the Ps18.1 NTAs have more hydrophobic solvent accessible surface than those of Ta16.9. NTA hydrophobic patches are comparable in size to the area buried in many protein-protein interactions, which would enable sHSPs to bind early unfolding intermediates. Reduced interactions of the Ps18.1 NTAs with each other and with the ACD contribute to the differences in dynamics and hydrophobic surface area of the two sHSPs. These data support a major role for the conformational equilibrium of the NTA in substrate binding and indicate features of the NTA that contribute to sHSP chaperone efficiency.

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Anisotropic shock responses of nanoporous Al by molecular dynamics simulations.

Publications

Anisotropic shock responses of nanoporous Al by molecular dynamics simulations.

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