The Membrane Dipole Potential in a Total Membrane Potential Model. Applications to Hydrophobic Ion Interactions With Membranes

Biophys J. 1986 Feb;49(2):541-52. doi: 10.1016/S0006-3495(86)83664-5.

Abstract

The total potential energy profile for hydrophobic ion interactions with lipid bilayers can be written as the sum of four terms: the electrical Born, image and dipole contributions, and a neutral energy term. We introduce a specific model for the membrane dipole potential, treating it as a two-dimensional array of point dipoles located near each membrane-water interface. Together with specific theoretical models for the other energy terms, a total potential profile is developed that successfully describes the complete set of thermodynamic parameters for binding and translocation for the two hydrophobic ion structural analogues, tetraphenylphosphonium (TPP+) and tetraphenylboron (TPB-). A reasonable fit to the data is possible if the dipole potential energy has a magnitude of 5.5 + 0.5 kcal/mol (240 + 20 mV), positive inside, and if the neutral energy contribution for TPP+ and TPB- is -7.0 + 1.0 kcal/mol. These results may also have important implications for small ion interactions with membranes and the energetics of charged groups in membrane proteins.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Electric Conductivity
  • Lipid Bilayers*
  • Mathematics
  • Membrane Potentials
  • Models, Biological*
  • Molecular Conformation

Substances

  • Lipid Bilayers