Abstract
We made fluorescence, electron paramagnetic resonance (EPR), electrophoretic
mobility, and ionizing electrode measurements to study the effect
of the monovalent lipid phosphatidylinositol (PI) and the trivalent
lipid phosphatidylinositol 4,5-bisphosphate (PIP2) on the electrostatic
potential adjacent to bilayer membranes. When the membranes were
formed from mixtures of PI and the zwitterionic lipid phosphatidylcholine
(PC), the Gouy-Chapman-Stern (GCS) theory described adequately
the dependence of potential on distance (0, 1, 2 nm) from the membrane,
mole \% negative lipid, and KCI. Furthermore, all EPR and fluorescence
probes reported identical surface potentials with a PC/PI membrane.
With PC/PIP2 membranes, however, the anionic (coion) probes reported
less negative potentials than the cationic (counterion) probes; the
deviations from the GCS theory were greater for the coions than
the counterions. Discreteness-of-charge theories based on the Poisson-Boltzmann
equation incorrectly predict that deviations from the GCS theory
should be greater for counterions than for coions. We discuss a consistent
statistical mechanical theory that takes into account three effects
ignored in the GCS theory: the finite size of the ions in the double
layer, the electrical interaction between pairs of ions (correlation
effects), and the mobile discrete nature of the surface charges.
This theory correctly predicts that deviations from GCS theory
should be negligible for monovalent lipids, significant for trivalent
lipids, and greater for coions than for counterions.
Description
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Links and resources
Tags
- 2156577
- 4,5-Diphosphate,
- Bilayers,
- Biological,
- Electrochemistry,
- Electron
- Fluorescence,
- Gov't,
- Lipid
- Models,
- Non-P.H.S.,
- Non-U.S.
- P.H.S.,
- Phosphatidylinositol
- Phosphatidylinositols,
- Phospholipids,
- Properties,
- Research
- Resonance
- Spectrometry,
- Spectroscopy,
- Spin
- Support,
- Surface
- U.S.