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pH Dependent Electrical Properties of the Inner- and Outer- Leaflets of Biomimetic Cell Membranes

Published

Author(s)

Vitalii I. Silin, David Hoogerheide

Abstract

Composition and asymmetry of lipid membranes provide a means for regulation of trans-membrane permeability of ions and small molecules. The pH dependence of these processes plays an important role in the functioning and survival of cells. In this work, we show the pH dependence of membrane electrical resistance (Rm) and capacitance (Cm) using electrochemical impedance spectroscopy (EIS), surface plasmon resonance (SPR) and neutron reflectometry (NR) data of biomimetic tethered bilayer lipid membranes (tBLMs). tBLMS were prepared with single-component phospholipid (PL) compositions, as well as mixtures of PLs (phosphatidyl choline (PC), phosphatidyl serine (PS), phosphatidyl ethanolamine (PE), sphingomyelin (SM) and cholesterol) that mimics inner- and outer- leaflets of plasma cell membranes. We find that all studied tBLMs have a resistance maximum at pHs near the pKas of the PLs. We postulate that these maximums are the result of protonation of the phosphate oxygen of the PLs and that hydronium ions play a major role in the conductance at pHs < pKas while sodium ions play the major role at pHs > pKas. An additional sharp resistance maximum of the PE tBLMs found at pH 5.9 and most likely represents the PE's isoelectric point (pI). Our data suggests that pH influences the structural changes of the membranes through the charge-charge interaction and formation of hydrogen bonding in the head groups of PLs. The data suggest that the phospholipid head groups and their interactions play a major role in determining the total membrane resistance by controlling the permeability of ions through both the hydrophilic and hydrophobic membrane regions. It was found that PL composition of tBLM models of inner- and outer- leaflets of the plasma membranes significantly differ in their electrical properties.
Citation
Journal of Colloid and Interface Science
Volume
594

Keywords

bilayer lipid membranes, electrochemical impedance spectroscopy, surface plasmon resonance, neutron reflectometry

Citation

Silin, V. and Hoogerheide, D. (2021), pH Dependent Electrical Properties of the Inner- and Outer- Leaflets of Biomimetic Cell Membranes, Journal of Colloid and Interface Science (Accessed May 26, 2024)

Issues

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Created July 14, 2021, Updated September 30, 2021