Institute of Physical Chemistry, Georg-August-University of Goettingen, Tammannstr. 6, 37077 Goettingen.
Langmuir. 2013 Aug 20;29(33):10463-74. doi: 10.1021/la401969t. Epub 2013 Aug 8.
The mechanical response of giant liposomes to compression between two parallel plates is investigated in the context of an artificial actin cortex adjacent to the inner leaflet of the bilayer. We found that nonlinear membrane theory neglecting the impact of bending sufficiently describes the mechanical response of liposomes consisting of fluid lipids to compression whereas the formation of an actin cortex or the use of gel-phase lipids generally leads to substantial stiffening of the shell. Giant vesicles are gently adsorbed on glassy surfaces and are compressed with tipless cantilevers using an atomic force microscope. Force-compression curves display a nonlinear response that allows us to determine the membrane tension σ0 and the area compressibility modulus K(A) by computing the contour of the vesicle as a function of the compression depth. The values for KA of fluid membranes correspond well to what is known from micropipet-suction experiments and computed from monitoring membrane undulations. The presence of a thick actin shell adjacent to the inner leaflet of the liposome membrane stiffens the system considerably, as mirrored in a significantly higher apparent area compressibility modulus.
我们研究了在双层膜的内叶与人工肌动蛋白皮层相邻的情况下，巨大脂质体在两个平行板之间受压时的机械响应。我们发现，忽略弯曲影响的非线性膜理论足以描述由流动脂质组成的脂质体的机械响应，而肌动蛋白皮层的形成或使用凝胶相脂质通常会导致壳的显著变硬。通过原子力显微镜，使用无尖端的悬臂梁将巨大囊泡轻轻吸附在玻璃表面上并进行压缩。力-压缩曲线显示出非线性响应，使我们能够通过计算囊泡的轮廓作为压缩深度的函数来确定膜张力 σ0 和面积压缩模量 K(A)。流体膜的 KA 值与微管抽吸实验中已知的值以及通过监测膜波动计算的值非常吻合。在脂质体膜的内叶附近存在一层厚的肌动蛋白壳，使系统显著变硬，这反映在明显更高的表观面积压缩模量上。
