融合能对膜间分离的依赖关系； 最优约束

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摘要翻译：
我们计算了平面双分子层间的特征融合能，它是从两个最接近的顺式叶片中的一个到另一个的疏水/亲水界面处测量的它们之间的距离。每个双层的两片叶子组成相等；0.6体积分数的片层形成的两亲性物，如二油酰基磷脂酰胆碱，和0.4体积分数的六方形成的两亲性物，如二油酰基磷脂酰乙醇胺。采用自洽场理论对模型进行求解。我们发现最大的障碍是产生亚稳柄。这种势垒最小，约为14.6$k_bt$，当双层层的距离比单叶厚度大20%左右时，这一距离相当于典型双层层的2-3纳米之间。将膜聚集在一起的蛋白质机械的大小可以阻止它们达到最佳分离。对于较大的分离，我们发现亚稳柄本身和产生亚稳柄的势垒的自由能随双层之间距离的增加呈线性速率。我们估计生物膜的这些速率分别为7.1$K_Bt$/nm和16.7$K_Bt$/nm。对这一速率的主要贡献来自与疏水尾巴相关的堆积能的增加。由此我们估计，对于血凝素的情况，亚稳柄本身的自由能为38 k_BT，而产生亚稳柄的屏障为73 k_BT。正如所观察到的那样，如此大的屏障需要不止一个血凝素分子参与融合过程。
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英文标题：
《Dependence of the energies of fusion on the intermembrane separation:
  optimal and constrained》
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作者：
J. Y. Lee and M. Schick
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最新提交年份：
2007
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分类信息：

一级分类：Physics        物理学
二级分类：Soft Condensed Matter        软凝聚态物质
分类描述：Membranes, polymers, liquid crystals, glasses, colloids, granular matter
膜，聚合物，液晶，玻璃，胶体，颗粒物质
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一级分类：Physics        物理学
二级分类：Statistical Mechanics        统计力学
分类描述：Phase transitions, thermodynamics, field theory, non-equilibrium phenomena, renormalization group and scaling, integrable models, turbulence
相变，热力学，场论，非平衡现象，重整化群和标度，可积模型，湍流
--

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英文摘要：
  We calculate the characteristic energies of fusion between planar bilayers as afunction of the distance between them, measured from the hydrophobic/hydrophilic interface of one of the two nearest, cis, leaves to the other. The two leaves of each bilayer are of equal composition; 0.6 volume fraction of a lamellar-forming amphiphile, such as dioleoylphosphatidylcholine, and 0.4 volume fraction of a hexagonal-forming amphiphile, such as dioleoylphosphatidylethanolamine. Self-consistent field theory is employed to solve the model. We find that the largest barrier to fusion is that to create the metastable stalk. This barrier is the smallest, about 14.6 $k_BT$, when the bilayers are at a distance about 20 percent greater than the thickness of a single leaf, a distance which would correspond to between two and three nanometers for typical bilayers. The very size of the protein machinery which brings the membranes together can prevent them from reaching this optimum separation. For even modestly larger separations, we find a linear rate of increase of the free energy with distance between bilayers for the metastable stalk itself and for the barrier to the creation of this stalk. We estimate these rates for biological membranes to be about 7.1 $k_BT$/nm and 16.7 $k_BT$/nm respectively. The major contribution to this rate comes from the increased packing energy associated with the hydrophobic tails. From this we estimate, for the case of hemagglutinin, a free energy of 38 k_BT for the metastable stalk itself, and a barrier to create it of 73 k_BT. Such a large barrier would require that more than a single hemagglutinin molecule be involved in the fusion process, as is observed.
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PDF链接：
https://arxiv.org/pdf/708.1336

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关键词：依赖关系 Contribution respectively Statistical Constrained 疏水 体积 增加 血凝素 距离