Influence of nonuniform geometry on nanoindentation of viral capsids
Influence of nonuniform geometry on nanoindentation of viral capsids
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DOI：
10.1529/biophysj.108.136176
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发表时间：
2008-10-15
影响因子：
3.4
通讯作者：
Klug, William S.
中科院分区：
文献类型：
--
作者：
Gibbons, Melissa M.;Klug, William S.
最近在病毒蛋白质外壳（衣壳）上进行的一系列纳米压痕实验已经建立了原子力显微镜（AFM）作为探测大型蛋白质组装机制的有用框架。具体来说，这些实验为研究整体组装响应与局部构象变化的耦合提供了机会。豇豆褪绿斑驳病毒的AFM实验，已知经历ph控制的肿胀构象变化，揭示了ph依赖的机械反应。先前的理论研究表明，壳体几何形状的均匀变化可以在力学响应中发挥重要作用。本文发展了一种精确捕获病毒衣壳异质几何形状的方法，并利用非线性连续弹性模型探讨了其对机械响应的影响。根据x射线晶体结构生成了原生豇豆和肿胀豇豆绿斑病毒衣壳的模型，并用于沿二、三、五重二十面体对称方向的AFM压痕的有限元模拟。研究人员观察到，与具有等效弹性模量的天然衣壳相比，肿胀衣壳模型的力响应大约软了两倍，明显更加非线性，并且更加依赖于方向，这表明衣壳的几何非均质性可以对整体结构响应产生重大影响。
A series of recent nanoindentation experiments on the protein shells (capsids) of viruses has established atomic force microscopy (AFM) as a useful framework for probing the mechanics of large protein assemblies. Specifically these experiments provide an opportunity to study the coupling of the global assembly response to local conformational changes. AFM experiments on cowpea chlorotic mottle virus, known to undergo a pH-controlled swelling conformational change, have revealed a pH-dependent mechanical response. Previous theoretical studies have shown that homogeneous changes in shell geometry can play a significant role in the mechanical response. This article develops a method for accurately capturing the heterogeneous geometry of a viral capsid and explores its effect on mechanical response with a nonlinear continuum elasticity model. Models of both native and swollen cowpea chlorotic mottle virus capsids are generated from x-ray crystal structures, and are used in finite element simulations of AFM indentation along two-, three-, and fivefold icosahedral symmetry orientations. The force response of the swollen capsid model is observed to be softer by roughly a factor of two, significantly more nonlinear, and more orientation-dependent than that of a native capsid with equivalent elastic moduli, demonstrating that capsid geometric heterogeneity can have significant effects on the global structural response.