Abstract
We study the crucial role of membrane fluctuations in maintaining a narrow gap between a fluid membrane tube and an enclosed solid particle. Solvent flows can occur in this gap, hence giving rise to a finite particle mobility along the tube. While our study has relevance for how cells are able to transport large organelles or other cargo along connecting membrane tubes, known as tunneling nanotubes, our calculations are also framed so that they can be tested by a specific in vitro experiment: A tubular membrane tether can be pulled from a membrane reservoir, such as an aspirated Giant Unilamellar Vesicle (GUV), e.g. using a conjugated bead that binds to the membrane and is held in a laser trap. We compute the subsequent mobility of colloidal particles trapped in the tube, focusing on the case when the particle is large compared to the equilibrium tube radius. We predict that the particle mobility should scale as ∼ σ−2/3, with σ the membrane tension.
Highlights
There has been a great deal of interest over recent years in the structure and dynamics of fluid membrane tubes
It has been shown that cells exchange enclosed material between themselves via the formation of similar long, narrow fluid membrane tubes known as tunneling nanotubes (TNTs) [8,9,10]
Bulges are observed in the diameter of TNTs at the position of an enclosed organelle or other object with a size larger than the equilibrium diameter of the enclosing fluid membrane tube [12,13,14,15]
Summary
There has been a great deal of interest over recent years in the structure and dynamics of fluid membrane tubes. It has been shown that cells exchange enclosed material between themselves via the formation of similar long, narrow fluid membrane tubes known as tunneling nanotubes (TNTs) [8,9,10]. Bulges are observed in the diameter of TNTs at the position of an enclosed organelle or other object with a size larger than the equilibrium diameter of the enclosing fluid membrane tube [12,13,14,15]. Such ‘bulges’ are observed in the transport of silicon microparticles [16] between cells. Our work may be relevant to understanding the role of TNTs in disease and drug delivery
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