Accurate Binding of Sodium and Calcium to a POPC Bilayer by Effective Inclusion of Electronic Polarization

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Melcr , J , Martinez-Seara , H , Nencini , R , Kolafa , J , Jungwirth , P & Ollila , O H S 2018 , ' Accurate Binding of Sodium and Calcium to a POPC Bilayer by Effective Inclusion of Electronic Polarization ' , Journal of Physical Chemistry B , vol. 122 , no. 16 , pp. 4546-4557 . https://doi.org/10.1021/acs.jpcb.7b12510

Title: Accurate Binding of Sodium and Calcium to a POPC Bilayer by Effective Inclusion of Electronic Polarization
Author: Melcr, Josef; Martinez-Seara, Hector; Nencini, Ricky; Kolafa, Jiri; Jungwirth, Pavel; Ollila, O. H. Samuli
Other contributor: University of Helsinki, Institute of Biotechnology

Date: 2018-04-26
Language: eng
Number of pages: 12
Belongs to series: Journal of Physical Chemistry B
ISSN: 1520-6106
DOI: https://doi.org/10.1021/acs.jpcb.7b12510
URI: http://hdl.handle.net/10138/324024
Abstract: Binding affinities and stoichiometries of Na+ and Ca2+ ions to phospholipid bilayers are of paramount significance in the properties and functionality of cellular membranes. Current estimates of binding affinities and stoichiometries of cations are, however, inconsistent due to limitations in the available experimental and computational methods. In this work, we improve the description of the binding details of Na+ and Ca2+ ions to a 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) bilayer by implicitly including electronic polarization as a mean field correction, known as the electronic continuum correction (ECC). This is applied by scaling the partial charges of a selected state-of-the-art POPC lipid model for molecular dynamics simulations. Our improved ECC-POPC model reproduces not only the experimentally measured structural parameters for the ion-free membrane, but also the response of lipid headgroup to a strongly bound cationic amphiphile, as well as the binding affinities of Na+ and Ca2+ ions. With our new model, we observe on the one side negligible binding of Na+ ions to POPC bilayer, while on the other side stronger interactions of Ca2+ primarily with phosphate oxygens, which is in agreement with the previous interpretations of the experimental spectroscopic data. The present model results in Ca2+ ions forming complexes with one to three POPC molecules with almost equal probabilities, suggesting more complex binding stoichiometries than those from simple models used to interpret the NMR data previously. The results of this work pave the way to quantitative molecular simulations with realistic electrostatic interactions of complex biochemical systems at cellular membranes.
Subject: MOLECULAR-DYNAMICS SIMULATIONS
CONCENTRATED AQUEOUS-SOLUTIONS
PHOSPHOLIPID HEAD GROUPS
LIPID-MEMBRANES
FORCE-FIELD
PHOSPHATIDYLCHOLINE BILAYERS
NEUTRON-SCATTERING
MAGNETIC-RESONANCE
ORDER PARAMETERS
IONIC LIQUIDS
1182 Biochemistry, cell and molecular biology
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