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

Trewby, W; Faraudo, J; Voïtchovsky, K

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.

Citation

Trewby, W., Faraudo, J., & Voïtchovsky, K. (2019). Long-lived ionic nano-domains can modulate the stiffness of soft interfaces. Nanoscale, 11(10), 4376-4384. https://doi.org/10.1039/c8nr06339g

• Journal Article Type: Article
• Acceptance Date: Feb 12, 2019
• Online Publication Date: Feb 25, 2019
• Publication Date: Mar 14, 2019
• Deposit Date: Feb 20, 2019
• Publicly Available Date: Feb 26, 2019
• Journal: Nanoscale
• Print ISSN: 2040-3364
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 11
• Issue: 10
• Pages: 4376-4384
• DOI: https://doi.org/10.1039/c8nr06339g