Lipid Membrane Electrostatics
Living reference work entry
Ionizable polar residues of membrane forming lipids are chargeable in polar solvents, such as water. The resulting net charges’ density depends on the aggregated lipids as well as the dissolved protons concentration (see Table 1). Charged lipid headgroups interact with other ions, too, which then affect membrane properties. The right panel of Fig. 1 illustrates, for example, sodium chloride effects on some phase transitions in fully hydrated zwitterionic phosphatidylcholine bilayer membranes; its left panel reveals charge-driven accumulation of sodium cations near the corresponding anionic phosphatidylglycerol bilayers. Figure 2 shows rubidium counterion distribution perpendicular to lipid membranes with different charges’ density and distribution. Electro-osmotic phenomena involving living organism membranes are more complex but fundamentally similar.
Negative logarithm of the protonation constant, -log Ka = pKa (or its apparent value pKapp) for the main...
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