Laboratoire Matière et Systèmes Complexes (MSC), Université Paris Diderot, Paris 7 and UMR CNRS 7057, Paris, France.
J Phys Condens Matter. 2011 Jul 20;23(28):284102. doi: 10.1088/0953-8984/23/28/284102. Epub 2011 Jun 27.
We study a dynamical curvature instability caused by a local chemical modification of a phospholipid membrane. In our experiments, a basic solution is microinjected close to a giant unilamellar vesicle, which induces a local chemical modification of some lipids in the external monolayer of the membrane. This modification causes a local deformation of the vesicle, which then relaxes. We present a theoretical description of this instability, taking into account both the change of the equilibrium lipid density and the change of the spontaneous membrane curvature induced by the chemical modification. We show that these two types of changes of the membrane properties yield different dynamics. In contrast, it is impossible to distinguish them when studying the equilibrium shape of a vesicle subjected to a global modification. In our model, the longest relaxation timescale is related to the intermonolayer friction, which plays an important part when there is a change in the equilibrium density in one monolayer. We compare our experimental results to the predictions of our model by fitting the measured time evolution of the deformation height to the solution of our dynamical equations. We obtain good agreement between theory and experiments. Our fits enable us to estimate the intermonolayer friction coefficient, yielding values that are consistent with previous measurements.
我们研究了由磷脂膜局部化学修饰引起的动力学曲率不稳定性。在我们的实验中，碱性溶液被微注射到一个巨大的单层囊泡附近，这会导致膜外单层中的一些脂质发生局部化学修饰。这种修饰会导致囊泡局部变形，然后再松弛。我们提出了一种理论描述这种不稳定性，考虑了平衡脂质密度的变化和化学修饰引起的自发膜曲率的变化。我们表明，这两种类型的膜性质变化会产生不同的动力学。相比之下，当研究全局修饰下囊泡的平衡形状时，就不可能将它们区分开来。在我们的模型中，最长的弛豫时间尺度与层间摩擦有关，当一个单层的平衡密度发生变化时，层间摩擦起着重要的作用。我们通过将测量的变形高度的时间演化拟合到我们的动力学方程的解，将我们的实验结果与模型的预测进行比较。我们得到了理论和实验之间的良好一致性。我们的拟合使我们能够估计层间摩擦系数，得到的值与之前的测量值一致。
