title: Electric field-induced changes in lipids investigated by modulated excitation FTIR spectroscopy.
abstract: The effect of electric fields on dry oriented multibilayers of dimyristoylphosphatidylcholine (DMPC) was investigated by transmission Fourier transform infrared electric field modulated excitation (E-ME) spectroscopy. A periodic rectangular electric potential (0-150 V, 1.25 Hz, 28.4 degrees C +/- 0.2 degrees C) was applied across the sample. To discriminate electric field-induced effects from possible temperature-induced effects resulting from a current flow (<1 pA) across the sample, corresponding temperature-modulated excitation (T-ME) measurements within the temperature uncertainty limits of +/-0.2 degrees C at 28.4 degrees C were performed. T-ME induced reversible gauche defects in the hydrocarbon chains, whereas E-ME resulted in reversible compression of dry DMPC bilayers. Periodic variation of the tilt angle of the hydrocarbon chains is suggested. The degree of absorbance modulation in the CH-stretching region was found to be in the order of 1:700, corresponding to a variation of the bilayer thickness of Deltaz = 0.0054 nm. Using a series connection of capacitors as equivalent circuit of the cell resulted in E = (1.2 +/- 0.7) x 10(7) V/m for the electric field in DMPC. Young's elasticity modulus of DMPC could be calculated to be E( perpendicular ) = 2.2 x 10(6) Pa +/- 1.8 x 10(6) Pa, which is in good agreement with published data obtained by electric field-dependent capacitance measurements.
authors.affiliation: Institute of Physical Chemistry, University of Vienna, A-1090 Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Schwarzott
authors.forename: Peter
authors.initials: P
authors.lastname: Lasch
authors.forename: Dieter
authors.initials: D
authors.lastname: Baurecht
authors.forename: Dieter
authors.initials: D
authors.lastname: Naumann
authors.forename: Urs Peter
authors.initials: UP
authors.lastname: Fringeli
mesh_terms: D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry* / Q000528:radiation effects*; D004563:Electrochemistry / Q000379:methods; D004574:Electromagnetic Fields; D018274:Electroporation / Q000379:methods; D008051:Lipid Bilayers / Q000737:chemistry* / Q000528:radiation effects*; D008560:Membrane Fluidity / Q000528:radiation effects; D008567:Membranes, Artificial; D008968:Molecular Conformation / Q000528:radiation effects; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D008567:Membranes, Artificial; D004134:Dimyristoylphosphatidylcholine