分支管状膜结构的稳定性
Stability of branched tubular membrane structures
AI总结：
本文通过三角网络模型模拟分支管状膜结构，发现120°角的Y型结点和四面体结点可被机械力稳定，并揭示了固定表面积下增加Y型分支能量代价为负等反直觉现象，为细胞分支网络稳定性提供启示。
摘要：
我们通过三角网络模型的计算机模拟，研究了分支管状膜结构的能量学与稳定性。我们发现，如果分支之间的角度为120°，则可以通过施加机械力来产生并稳定三重（Y型）结点。对于具有四面体角的四面体结点，情况同样如此。如果施加了错误的角度，分支会合并成线性结构，即纯管。释放机械力后，如果将封闭体积和平均曲率（面积差）约束为固定值，Y型分支结构仍保持亚稳态；然而四面体结点会分裂成两个Y型结点。有些反直觉的是，在表面积和管径固定的结构中，增加一个Y型分支的能量代价为负，即使计入额外分支端的正贡献也是如此。然而，对于固定的平均曲率，增加分支同时会迫使管变细，因此总曲率能量代价为正。我们讨论了这些结果对细胞中分支网络结构稳定性的可能意义。
英文摘要：
We study the energetics and stability of branched tubular membrane structures by computer simulations of a triangulated network model. We find that triple (Y-)junctions can be created and stabilized by applying mechanical forces, if the angle between branches is 120 o . The same holds for tetrahedral junctions with tetraeder angles. If the wrong angles are enforced, the branches coalesce to a linear structure, a pure tube. After releasing the mechanical force, Y-branched structures remain metastable if one constrains the enclosed volume and the average curvature (the area difference) to a fixed value; tetrahedral junctions however split up into two Y-junctions. Somewhat counterintuitively, the energy cost of adding a Y-branch is negative in structures with fixed surface area and tube diameter, even if one accounts for the positive contribution of the additional branch end. For fixed average curvature, however, adding a branch also enforces a thinning of tubes, therefore the overall curvature energy cost is positive. Possible implications for the stability of branched networks structures in cells are discussed.
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