Viscosity is a key property of cell membranes that controls mobility of embedded proteins and membrane remodeling. Measuring it is challenging because existing approaches involve complex experimental designs and/or models, and the applicability of some is limited to specific systems and membrane compositions. As a result there is scarcity of data and the reported values for membrane viscosity vary by orders of magnitude for the same system. Here, we show how viscosity of bilayer membranes can be obtained from the transient deformation of giant unilamellar vesicles. The approach enables a non-invasive, probe-independent and high-throughput measurement of the viscosity of bilayers made of lipids or polymers with a wide range of compositions and phase state. Pure lipid and single-phase mixed bilayers are found to behave as Newtonian fluids with strain-rate independent viscosity, while phase-separated and diblock-copolymers systems exhibit shear-thinning in the explored range of strain rates 1-2000 s⁻¹. The results also reveal that electrically polarized bilayers can be significantly more viscous than charge-neutral bilayers. These findings suggest that biomembrane viscosity is a dynamic property that can be actively modulated not only by composition but also by membrane polarization, e.g., as in action potentials.

中文翻译：

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用于脂质和聚合物膜的高通量粘度测量的囊泡微流变仪

粘度是细胞膜的一个关键特性，它控制嵌入蛋白质的流动性和膜重塑。测量它具有挑战性，因为现有方法涉及复杂的实验设计和/或模型，并且某些方法的适用性仅限于特定系统和膜成分。因此，数据稀缺，对于同一系统，膜粘度的报告值存在数量级差异。在这里，我们展示了如何从巨大的单层囊泡的瞬态变形中获得双层膜的粘度。该方法能够对由具有广泛成分和相态的脂质或聚合物制成的双层的粘度进行非侵入性、探针独立和高通量测量。s ^-1。结果还表明，与电荷中性双层相比，电极化双层可以明显更粘稠。这些发现表明，生物膜粘度是一种动态特性，不仅可以通过成分进行调节，还可以通过膜极化（例如动作电位）进行主动调节。