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Issue 10, 2019
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Long-lived ionic nano-domains can modulate the stiffness of soft interfaces

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Abstract

Metal ions underpin countless processes at bio-interfaces, including maintaining electroneutrality, modifying mechanical properties and driving bioenergetic activity. These processes are typically described by ions behaving as independently diffusing point charges. Here we show that Na+ and K+ ions instead spontaneously form correlated nanoscale networks that evolve over seconds at the interface with an anionic bilayer in solution. Combining single-ion level atomic force microscopy and molecular dynamic simulations we investigate the configuration and dynamics of Na+, K+, and Rb+ at the lipid surface. We identify two distinct ionic states: the well-known direct electrostatic interaction with lipid headgroups and a water-mediated interaction that can drive the formation of remarkably long-lived ionic networks which evolve over many seconds. We show that this second state induces ionic network formation via correlative ion–ion interactions that generate an effective energy well of −0.4kBT/ion. These networks locally reduce the stiffness of the membrane, providing a spontaneous mechanism for tuning its mechanical properties with nanoscale precision. The ubiquity of water-mediated interactions suggest that our results have far-reaching implications for controlling the properties of soft interfaces.

Graphical abstract: Long-lived ionic nano-domains can modulate the stiffness of soft interfaces

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Publication details

The article was received on 06 Aug 2018, accepted on 12 Feb 2019 and first published on 25 Feb 2019


Article type: Paper
DOI: 10.1039/C8NR06339G
Nanoscale, 2019,11, 4376-4384
  • Open access: Creative Commons BY license
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    Long-lived ionic nano-domains can modulate the stiffness of soft interfaces

    W. Trewby, J. Faraudo and K. Voïtchovsky, Nanoscale, 2019, 11, 4376
    DOI: 10.1039/C8NR06339G

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