纳米尺度膜系链的超面积尺度行为
Excess area dependent scaling behavior of nano-sized membrane tethers
摘要：
细胞膜中的热波动表现为过量面积（${\cal A}_{\rm ex}$），其在亚微米尺度上控制大量物理过程。我们提出了一个理论框架，在硅片上的系绳拉法的基础上，这可能是用来可靠地估计活细胞中的${\cal A}_{\rm ex}$。从我们的模拟估计系绳力比较以及与我们的实验测量从破裂的GUV和HeLa细胞提取的系绳。我们证明了我们的方法的意义和有效性，显示我们所有的计算以及实验系绳提取在15种不同的细胞类型崩溃到两个统一的比例关系映射系绳力，系绳半径，弯曲刚度$κ$，和膜张力$σ$。我们发现，$R_{\rm bead}$，润湿区域的大小，是一个重要的决定因素提取的系绳，这是等于$ξ=\sqrt{κ/2σ}$（膜的特征长度尺度）为$R_{\rm bead}<ξ$的半径，并等于$R_{\rm bead}$为$R_{\rm bead}>ξ$。我们还发现，估计的多余面积遵循线性缩放行为，仅取决于膜的${\cal A}_{\rm ex}$的真实值，基于此，我们提出了一种自洽的技术来估计细胞中多余膜面积的范围。
英文摘要：
Thermal fluctuations in cell membranes manifest as an excess area (${\cal A}_{\rm ex}$) which governs a multitude of physical process at the sub-micron scale. We present a theoretical framework, based on an in silico tether pulling method, which may be used to reliably estimate ${\cal A}_{\rm ex}$ in live cells. The tether forces estimated from our simulations compare well with our experimental measurements for tethers extracted from ruptured GUVs and HeLa cells. We demonstrate the significance and validity of our method by showing that all our calculations along with experiments of tether extraction in 15 different cell types collapse onto two unified scaling relationships mapping tether force, tether radius, bending stiffness $κ$, and membrane tension $σ$. We show that $R_{\rm bead}$, the size of the wetting region, is an important determinant of the radius of the extracted tether, which is equal to $ξ=\sqrt{κ/2σ}$ (a characteristic length scale of the membrane) for $R_{\rm bead}<ξ$, and is equal to $R_{\rm bead}$ for $R_{\rm bead}>ξ$. We also find that the estimated excess area follows a linear scaling behavior that only depends on the true value of ${\cal A}_{\rm ex}$ for the membrane, based on which we propose a self-consistent technique to estimate the range of excess membrane areas in a cell.
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