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Role of Ion–Phospholipid Interactions in Zwitterionic Phospholipid Bilayer Ion Permeation

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journal contribution
posted on 23.07.2020, 19:35 by Evelyne Deplazes, Beatriu Domingo Tafalla, Charles G. Cranfield, Alvaro Garcia
Despite the central role of Na+ and K+ in physiological processes, it is still unclear whether they interact or alter the physical properties of simple zwitterionic phospholipid bilayers at physiologically relevant concentrations. Here we report a difference in membrane permeability between Na+ and K+, as measured with electrical impedance spectroscopy and tethered bilayer lipid membranes. We reveal that the differences in membrane permeability originate from distinct ion coordination by carbonyl oxygens at the phospholipid–water interface, altering the propensity for bilayer pore formation. Molecular dynamics simulations showed differences in the coordination of Na+ and K+ at the phospholipid–water interface of zwitterionic phospholipid bilayers. The ability of Na+ to conscript more phospholipids with a greater number of coordinating interactions causes a higher localized energy barrier for pore formation. These results provide evidence that ion-specific interactions at the phospholipid–water interface can modulate the physical properties of zwitterionic phospholipid bilayers.