Despite the central role of Na + and K + in physiological processes, it is still unclear whether they interact or alter 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 localised energy barrier for pore formation. These results provide evidence that ion specific interactions at the phospholipidwater interface can modulate physical properties of zwitterionic phospholipid bilayers. TOC

Calcium ions (Ca 2+ ) play a fundamental role in membrane-associated physiological processes. Ca 2+ can also significantly modulate the physicochemical properties of phospholipid bilayers, but whether this occurs at physiologically relevant concentrations is difficult to determine because of the uncertainty in the reported affinity of Ca 2+ for phospholipid bilayers. In this article, we determine the apparent affinity of Ca 2+ for zwitterionic phospholipid bilayers using tethered bilayer lipid membranes (tBLMs) used in conjunction with swept-frequency electrical impedance spectroscopy (EIS). We report that Ca 2+ binds to phospholipid bilayers at physiologically relevant concentrations and modulates membrane permeability. We present direct experimental evidence that this effect is governed by specific interactions with select lipid headgroup moieties, which is supported by data from molecular dynamics (MD) simulations. This is the first reported use of tBLM/EIS to estimate cation−membrane affinity. Combined with MD simulations, this technique provides a novel methodology to elucidate the molecular details of cation−membrane interactions at the water−phospholipid interface.

No abstract

evaluate its possible interaction with pulmonary surfactant. Nanoparticles were prepared by nanoprecipitation and the influence of different operational conditions on the characteristics of the obtained nanocarriers was evaluated. On the other hand, we have evaluated the possible interaction between pulmonary surfactant and PHA nanoparticles by characterizing the effect of surfactant proteins and lipids on the colloidal stability of the nanomaterial. in addition, we evaluated the effect of the nanomaterial on the structure and surface-active properties of lung surfactant membranes.