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Formation and stability of lipid membrane nanotubes

September 2017. Lipid membrane nanotubes are abundant in living cells, even though tubules are energetically less stable than sheet-like structures. According to membrane elastic theory, the tubular endoplasmic reticulum (ER), with its high area-to-volume ratio, appears to be particularly unstable. Scientists at the Max Planck Institute of Biophysics in Frankfurt explored how tubular membrane structures can nevertheless be induced and why they persist.

In Monte Carlo simulations of a fluid–elastic membrane model subject to thermal fluctuations and without constraints on symmetry, the scientists found that a steady increase in the area-to-volume ratio readily induces tubular structures. In simulations mimicking the ER wrapped around the cell nucleus, tubules emerge naturally as the membrane area increases. Once formed, a high energy barrier separated tubules from the thermodynamically favored sheet-like membrane structures. Remarkably, this barrier persisted even at large area-to-volume ratios, protecting tubules against shape transformations despite enormous driving forces toward sheet-like structures. Molecular dynamics simulations of a molecular membrane model confirmed the metastability of tubular structures. Volume reduction by osmotic regulation and membrane area growth by lipid production and by fusion of small vesicles emerge as powerful factors in the induction and stabilization of tubular membrane structures.



Gerhard Hummer
Max Planck Institute of Biophysics
Frankfurt am Main


Bahrami AH, Hummer G (2017) Formation and stability of lipid membrane nanotubes. ACS Nano: published online 5 September 2017. http://dx.doi.org/10.1021/acsnano.7b05542



Cluster of Excellence Macromolecular Complexes