Measuring the Effect of Tension on Lipid Membrane Viscosity
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The fluidity of the lipid membrane is essential for many biological functions, such as cellular cargo trafficking and cell signaling. The timescale of this fluidity is dictated by the two-dimensional (2D) viscosity of the membrane. Membrane viscosity is poorly measured, and the effect of certain parameters on 2D membrane viscosity has not been tested, and is therefore unknown. The purpose of this research is to explore the effect of one of those parameters: tension. Examples of cellular membranes under tension include the membranes of cells involved in cell crawling or the membranes of cells involved in the Notch signaling pathway. In order to study the effect of tension on lipid membranes, I examined cell-free, model lipid membranes. I built and used a micropipette aspiration system and observed diffusion in phase-separated Giant Unilamellar Vesicles (GUVs). Micropipette aspiration is a technique in which lipid vesicles are partially suctioned into pipettes of a few microns in diameter, stretching the membrane and inducing tension. The results of the experiment indicate that membrane viscosity decreases with increased tension. This provides the first measurement of tension-mediated viscosity changes, which opens the door to many future experiments.