标题： 使用锚定冻结斑块模拟弯曲脂质膜 显示英文标题

标题： Simulating Curved Lipid Membranes Using Anchored Frozen Patches

摘要： 脂质双层由于自组装条件或某些生物过程常常形成高曲率构型。 然而，脂质膜的基于粒子的模拟主要针对平面脂质膜，因为平面膜在周期性边界条件下容易连接。 要模拟弯曲的脂质膜，可以模拟整个囊泡、圆柱体或双层盘状聚集体（bicelle）。 也可以使用人工方法来控制曲率，例如施加珠子的虚拟壁、径向谐波势或“将边缘粘合”。 由于曲率是通过特定方法施加的，这些现有方法存在局限性。 在此，我们提出了一种替代方法，通过用“冻结”的平衡膜片段锚定弯曲的脂质膜，从而引入任意曲率。 这里提出的方法适用于所有基于粒子的脂质模型，并且易于扩展到多种几何形状。 作为示例，我们使用由Martini3粗粒化模型参数化的DPPC、DOPC、DLPC和DOPE脂质模拟弯曲膜。 这种方法引入了有限的尺寸效应伪影，防止了膜边缘的脂质翻转，并允许自由膜中心的波动。 我们提供了在平面膜上对该方法的验证，并讨论了从弯曲膜中提取形状和单层量（厚度、有序参数）的方法。 曲率会导致脂质单层特性出现不对称变化。 最后，我们探讨了曲率和膜不对称性在数量和脂质类型上的耦合效应。 我们报告了使用该方法可获得的独特形态（诱导凝胶相、分面）和行为（厚度依赖于相邻单层类型）。 显示英文摘要

摘要： Lipid bilayers often form high-curvature configurations due to self-assembly conditions or certain biological processes. However, particle-based simulations of lipid membranes are predominantly of flat lipid membranes because planar membranes are easily connected over periodic boundary conditions. To simulate a curved lipid membrane, one can simulate an entire vesicle, a cylinder, or a bicelle (disk-like bilayer aggregate). One can also use artificial methods to control curvature, such as applying virtual walls of beads, radial harmonic potentials, or ``tape up the edges''. These existing methods have limitations due to the method by which curvature is imposed. Herein, we propose an alternative method of introducing arbitrary curvature by anchoring a curved lipid membrane with ``frozen'' equilibrated membrane patches. The method presented here is compatible with all particle-based lipid models and easily extended to many geometries. As an example, we simulate curved membranes with DPPC, DOPC, DLPC and DOPE lipids as parameterized by the Martini3 coarse-grained model. This method introduces limited finite-size artifacts, prevents lipid flip-flop at membrane edges, and allows fluctuations of the free membrane center. We provide verification of the method on flat membranes and discussion on extracting shape and per-leaflet quantities (thickness, order parameter) from curved membranes. Curvature produces asymmetric changes in lipid leaflet properties. Finally, we explore the coupled effect of curvature and membrane asymmetry in both number and lipid type. We report the resulting unique morphologies (inducing gel phase, faceting) and behaviors (thickness dependent on adjacent leaflet type) that are accessible with this method.