Teardrop shapes minimize bending energy of fusion pores connecting planar bilayers.
Teardrop shapes minimize bending energy of fusion pores connecting planar bilayers.
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DOI：
10.1103/physreve.88.062701
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发表时间：
2013-12
期刊：
影响因子：
--
通讯作者：
Cohen FS
中科院分区：
文献类型：
--
作者：
Ryham RJ;Ward MA;Cohen FS
设计了一种数值梯度流动程序来表征连接两个平行平面双层膜的融合孔的最小能量形状。孔隙能量由张开、倾斜和拉伸组成，通过将每个双层膜建模为两个单层，并将双层膜的每个单层视为用平均脂质取向场描述的自由变形表面来获得。两个单分子层之间的空隙被一个空间惩罚配方所阻止。假设孔隙形状具有轴向对称性和反射对称性。对于固定的孔隙半径和双层分离，梯度流动程序应用于初始的环形孔隙形状。使用最初的椭圆孔隙形状得到了相同的最终形状。所得的最小孔隙形状和能量作为孔隙尺寸和脂质组成的函数进行了分析。以前的研究要么假设孔隙形状，要么限制孔隙形状，从而默认地提供不确定数量的能量来维持孔隙形状。在本研究中导出的形状是计算的输出，并没有提供外部提供的能量。因此，我们的方法产生的能量最小值明显低于先前研究报告。最小能孔的膜在孔腔附近向外弯曲，产生的孔长度超过了两个融合膜之间的距离。
A numerical gradient flow procedure was devised to characterize minimal energy shapes of fusion pores connecting two parallel planar bilayer membranes. Pore energy, composed of splay, tilt, and stretching, was obtained by modeling each bilayer as two monolayers and treating each monolayer of a bilayer membrane as a freely deformable surface described with a mean lipid orientation field. Voids between the two monolayers were prevented by a steric penalty formulation. Pore shapes were assumed to possess both axial and reflectional symmetry. For fixed pore radius and bilayer separation, the gradient flow procedure was applied to initially toroidal pore shapes. Using initially elliptical pore shapes yielded the same final shape. The resulting minimal pore shapes and energies were analyzed as a function of pore dimension and lipid composition. Previous studies either assumed or confined pore shapes, thereby tacitly supplying an unspecified amount of energy to maintain shape. The shapes derived in the present study were outputs of calculations and an externally provided energy was not supplied. Our procedure therefore yielded energy minima significantly lower than those reported in prior studies. The membrane of minimal energy pores bowed outward near the pore lumen, yielding a pore length that exceeded the distance between the two fusing membranes.