Adsorption of metal cations onto a cellular membrane changes its properties, such as interactions with charged moieties or the propensity for membrane fusion. It is, however, unclear whether cells can regulate ion adsorption and the related functions via locally adjusting their membrane composition. We employed fluorescence techniques and computer simulations to determine how the presence of cholesterol-a key molecule inducing membrane heterogeneity-affects the adsorption of sodium and calcium onto zwitterionic phosphatidylcholine bilayers. We found that the transient adsorption of sodium is dependent on the number of phosphatidylcholine head groups, while the strong surface binding of calcium is determined by the available surface area of the membrane. Cholesterol thus does not affect sodium adsorption and only plays an indirect role in modulating the adsorption of calcium by increasing the total surface area of the membrane. These observations also indicate how lateral lipid heterogeneity can regulate various ion-induced processes including adsorption of peripheral proteins, nanoparticles, and other molecules onto membranes.

Institute of Organic Chemistry and Biochemistry Czech Academy of Sciences Flemingovo nam 2 166 10 Prague 6 Czech Republic and Faculty of Pharmacy University of Helsinki Viikinkaari 5E FI 00014 University of Helsinki Finland

Institute of Organic Chemistry and Biochemistry Czech Academy of Sciences Flemingovo nam 2 166 10 Prague 6 Czech Republic and Laboratory of Physics Tampere University of Technology P O Box 692 FI 33101 Tampere Finland

J Heyrovský Institute of Physical Chemistry Czech Academy of Sciences Dolejskova 3 182 23 Prague 8 Czech Republic

Laboratory of Physics Tampere University of Technology P O Box 692 FI 33101 Tampere Finland and Department of Physics University of Helsinki P O Box 64 FI 00014 University of Helsinki Finland

References provided by Crossref.org

Effective Inclusion of Electronic Polarization Improves the Description of Electrostatic Interactions: The prosECCo75 Biomolecular Force Field

Quantitative Comparison against Experiments Reveals Imperfections in Force Fields' Descriptions of POPC-Cholesterol Interactions

Curvature Matters: Modeling Calcium Binding to Neutral and Anionic Phospholipid Bilayers

Ionic Strength and Solution Composition Dictate the Adsorption of Cell-Penetrating Peptides onto Phosphatidylcholine Membranes