A Combined Patch-Clamp and Electrorotation Study of the Voltage- and Frequency-Dependent Membrane Capacitance Caused by Structurally Dissimilar Lipophilic Anions |
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Authors: | D Zimmermann M Kiesel U Terpitz A Zhou R Reuss J Kraus W A Schenk E Bamberg V L Sukhorukov |
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Institution: | (1) Department of Biophysical Chemistry, Max-Planck Institute of Biophysics, Max-von-Laue Strasse 3, D-60438 Frankfurt am Main, Germany;(2) Department of Biophysical Chemistry, Chemistry and Pharmacy, Johann-Wolfgang-Goethe University, Max-von-Laue Strasse 4, D-60438 Frankfurt am Main, Germany;(3) Department of Biotechnology, University of Würzburg, Biozentrum, Am Hubland, D-97074 Würzburg, Germany;(4) Institute of Inorganic Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany |
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Abstract: | Interactions of structurally dissimilar anionic compounds with the plasma membrane of HEK293 cells were analyzed by patch
clamp and electrorotation. The combined approach provides complementary information on the lipophilicity, preferential affinity
of the anions to the inner/outer membrane leaflet, adsorption depth and transmembrane mobility. The anionic species studied
here included the well-known lipophilic anions dipicrylamine (DPA−), tetraphenylborate (TPB−) and W2(CO)10(S2CH)]−, the putative lipophilic anion
and three new heterocyclic W(CO)5 derivatives. All tested anions partitioned strongly into the cell membrane, as indicated by the capacitance increase in patch-clamped
cells. The capacitance increment exhibited a bell-shaped dependence on membrane voltage. The midpoint potentials of the maximum
capacitance increment were negative, indicating the exclusion of lipophilic anions from the outer membrane leaflet. The adsorption
depth of the large organic anions DPA−, TPB− and increased and that of W(CO)5 derivatives decreased with increasing concentration of mobile charges. In agreement with the patch-clamp data, electrorotation
of cells treated with DPA− and W(CO)5 derivatives revealed a large dispersion of membrane capacitance in the kilohertz to megahertz range due to the translocation
of mobile charges. In contrast, in the presence of TPB− and no mobile charges could be detected by electrorotation, despite their strong membrane adsorption. Our data suggest that the
presence of oxygen atoms in the outer molecular shell is an important factor for the fast translocation ability of lipophilic
anions. |
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Keywords: | Hydrophobic ion Tungsten pentacarbonyl HEK293 cell Jurkat cell Dipicrylamine Tetraphenylborate |
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