Large Scale Membrane Movement Induced by a Cation Switch

22 March 2021, Version 2
This content is a preprint and has not undergone peer review at the time of posting.


A biomembrane sample system where millimolar changes of cations induce reversible large scale (≥ 200 Å) changes in the membrane-to-surface distance is described. The system composes of a free-floating bilayer (FFB), formed adjacent to a self-assembled monolayer (SAM). To examine the membrane movements, differently charged FFBs in the presence and absence of Ca2+ and Na+, respectively, were examined using neutron reflectivity (NR) and quartz crystal microbalance (QCM) measurements, alongside molecular dynamics (MD) simulations. In NR the variation of Ca2+ and Na+ concentration enabled precision manipulation of the FFB-to-surface distance. Simulations suggest that Ca2+ ions bridge between SAM and bilayer whereas the more diffuse binding of Na+, especially to bilayers, is unable to fully overcome the repulsion between anionic FFB and anionic SAM. Reproduced NR results with QCM demonstrate the potential of this easily producible sample system to become a standard analysis tool for e.g. investigating membrane binding effects, endocytosis and cell signalling.


Biological Membrane
Electrostatic interactions
cation binding
self-assembled monolayer surfaces
Molecular Dynamics Simulation Study
neutron reflectometry measurements
model membranes
biosensor technology

Supplementary materials



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