Biointerphases

Journal for Biophysical Chemistry

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Open Access

Charging and structure of zwitterionic supported bilayer lipid membranes studied by streaming current measurements, fluorescence microscopy, and attenuated total reflection Fourier transform infrared spectroscopy

  • Ralf Zimmermann1,
  • David Küttner1,
  • Lars Renner1,
  • Martin Kaufmann1,
  • Jan Zitzmann1,
  • Martin Müller1 and
  • Carsten Werner1, 2
Biointerphases4:40100001

https://doi.org/10.1116/1.3082042

Received: 5 November 2008

Accepted: 26 January 2009

Abstract

The authors report on the characterization of the charge formation at supported bilayer lipid membranes (sBLMs) prepared from the zwitterionic lipid 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine on planar silicon dioxide substrates. The charging of the sBLMs was studied in KCl solutions of different ionic strengths between 0.1 and 10 mM by streaming current measurements. In addition, attenuated total reflection Fourier transform infrared spectroscopy and fluorescence microscopy were applied to determine the lipid concentration in the membrane and to study the influence of the harsh conditions (pH 9-2, shear forces) during the electrokinetic measurements on the membrane stability and the lipid diffusion coefficient. The sBLMs were found to be extremely stable. Isoelectric points of about 4 revealed that unsymmetrical adsorption of hydroxide and hydronium ions determined the charging of the outer leaflet of the membrane in the investigated pH range. The diffusion coefficients were found to be rather independent on the ionic strength at neutral and alkaline pH. However, significantly decreased lipid diffusion at pH<4 indicated a charge-induced transition of the fluidic bilayer into a gel/ordered-phase bilayer.