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Structural Effects of Cation Binding to DPPC Monolayers
preprintsubmitted on 30.08.2020, 19:51 and posted on 31.08.2020, 13:12 by Matti Javanainen, Wei Hua, Ondrej Tichacek, Pauline Delcroix, Lukasz Cwiklik, Heather Allen
Ions at the two sides of the plasma membrane maintain the transmembrane potential, participate in signaling, and affect the properties of the membrane itself. The extracellular leaflet is particularly enriched in phosphatidylcholine lipids an under the influence of Na+, Ca2+, and Cl− ions. In this work, we combined molecular dynamics simulations performed using state-of-the-art models with vibrational sum frequency generation (VSFG) spectroscopy to study the effects of these key ions on the structure of dipalmitoylphosphatidylcholine. We used lipid monolayers as a proxy for membranes, as this approach enabled a direct comparison between simulation and experiment. We find that the effects of Na+ are minor. Ca2+, on the other hand, strongly affects the lipid head group conformations and induces a tighter packing of lipids, thus promoting the liquid condensed phase. It does so by binding to both the phosphate and carbonyl oxygens via direct and water-mediated binding modes, the ratios of which depend on the monolayer packing. Clustering analysis performed on simulation data revealed that changes in area per lipid or CaCl2 concentration both affect the head group conformations, yet their effects are anti-correlated. Cations at the monolayer surface also attract Cl−, which at large CaCl2 concentrations penetrates deep to the monolayer. This phenomenon coincides with a radical change in the VSFG spectra of the phosphate group, thus indicating the emergence of a new binding mode.
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Czech Science Foundation, EXPRO grant 19-26854X
Emil Aaltonen Foundation
NSF, grant CHE-1111762
NSF Center for Aerosol Impacts on Chemistry on the Environment, grant CHE-1305427
Czech Science Foundation, grant 17-06792S
Email Address of Submitting Authormatti.firstname.lastname@example.org
InstitutionInstitute of Organic Chemistry and Biochemistry, Czech Academy of Sciences
ORCID For Submitting Author0000-0003-4858-364X
Declaration of Conflict of Interestno conflict of interest
Version NotesInitial submission
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