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Updated: Mar 20, 2026

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Published on: May 27, 2021
Free Volume in Membranes: Viscosity or Tension?
1Department of Anesthesiology and Pain Management, UT Southwestern, Dallas, TX, USA.
Abstract:
Many papers have used fluorescent probe diffusion to infer membrane viscosity but the measurement is actually an assay of the free volume of the membrane. The free volume is also related to the membrane tension. Thus, changes in probe mobility refer equally well to changes in membrane tension. In complicated structures like cell membranes, it appears more intuitive to consider variations in free volume as referring to the effect of domains structures and interactions with the cytoskeleton than changes in viscosity since tension is a state variable and viscosity is not.
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