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Electrical Properties of Membranes

Electrical Properties of Membranes. Internal Dipole Potential –probably due to the oriented carbonyl of acyl chains Born Energy – Work to move charges into the bilayer Membrane Surface Potential –due to charges on the surface Local pH at Membrane Surfaces Metal Ion Binding

candice-bowers
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Electrical Properties of Membranes

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  1. Electrical Properties of Membranes • Internal Dipole Potential –probably due to the oriented carbonyl of acyl chains • Born Energy – Work to move charges into the bilayer • Membrane Surface Potential –due to charges on the surface • Local pH at Membrane Surfaces • Metal Ion Binding • Probe Binding/Hydrophobic Ions/Cell Penetrating Peptides • Transmembrane Potential – due to ion permeabilities leading to gradients on either side of the bilayer (can also be protein transport driven) • Ions and Protons • Energized Membranes • Permeability to Ions • Transmembrane Potential Diffusers

  2. Internal Dipole Potential ~ 240mV positive inside the bilayer Born model – work required to transfer a charged species from water to the bilayer Na+ Cl- WB = (81Z2/r) kcal/mol Dielectric constant for water ~ 80 Dielectric constant for membrane ~2

  3. Surface Potential and Gouy-Chapman Theory • Charges are smeared uniformly over the surface (not individual points) • Ions in solution are treated as point charges • Image effects and repulsions of mobile ions are neglected • Dielectric constants are considered constant in each phase • Stern modification takes into account the size of charges on the surface and maximum number that can bind

  4. Surface Potential and Gouy-Chapman Theory

  5. pH at charged surfaces Gouy-Chapman Theory

  6. Transmembrane Potentials

  7. Ionophores - increase membrane permeability to ions

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