Evidence for leaflet-dependent redistribution of charged molecules in fluid supported phospholipid bilayers.

Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Langmuir (Impact Factor: 4.38). 12/2008; 24(23):13250-3. DOI: 10.1021/la802909c
Source: PubMed

ABSTRACT The asymmetric distribution of charged molecules between the leaflets of solid-substrate-supported phospholipid bilayers is studied using imaging ellipsometry, fluorescence microscopy, and numerical solutions of the Poisson-Boltzmann equation. Experiments are facilitated by the use of patterned substrates that allow for side-by-side comparison of lipid monolayers and supported bilayers. On silica surfaces, negatively charged lipid components are shown to be enriched in the outer leaflet of a supported bilayer system at modest salt concentrations. The approaches developed provide a general means for determining asymmetries of charged components in supported lipid bilayers.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nowadays, there is much experimental evidence that the mechanical properties of biological membranes affect membraneprotein functions. A very convenient technique to study these properties on a spatial scale relevant to that of single proteins is represented by Atomic Force Spectroscopy (AFS). In this study we measured the force the AFM tip has to apply on a supported lipid bilayer to punch-through it as a function of different environmental parameters. We observed that this force is reduced when the lipid bilayer is in its phase transition region. We interpreted our results on the basis of thermodynamical considerations and we stressed their biological relevance. In particular, the reduced punch-through force in the phase transition region could be relevant for the function of membraneproteins which operates by conformational changes at the protein/lipid interface. We also suggest that the presence of a transmembrane voltage drop can affect the measured punch-through force.
    Soft Matter 07/2011; 7(15):7054-7064. · 4.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: While electrophoresis in lipid bilayers has been performed since the 1970s, the technique has until now been unable to accurately measure the charge on lipids and proteins within the membrane based on drift velocity measurements. Part of the problem is caused by the use of the Einstein-Smoluchowski equation to estimate the electrophoretic mobility of such species. The source of the error arises from the fact that a lipid headgroup is typically smaller than the Debye length of the adjacent aqueous solution in most electrophoresis experiments. Instead, the Henry equation can more accurately predict the electrophoretic mobility at sufficient ionic strength. This was done for three dye-labeled lipids with different sized head groups and a charge on each lipid of -1. Also, the charge was measured as a function of pH for two titratable lipids that were fluorescently labeled. Finally, it was shown that the Henry equation also has difficulties measuring the correct lipid charge at salt concentrations below 5 mM, where electroosmotic forces are more significant.
    Analytical Chemistry 11/2013; · 5.83 Impact Factor
  • Materials 12/2012; 5(12):2658-2680. · 1.88 Impact Factor

Full-text (2 Sources)

Available from
Feb 2, 2015