Protein influence on the plasma membrane dielectric properties: In vivo study utilizing dielectric spectroscopy and fluorescence microscopy

We have investigated the origin of the dielectric response of the plasma membrane of living yeast cells ( Saccharomyces cerevisiae) by using radiofrequency dielectric spectroscopy. The cells were genetically engineered to overexpress in the membrane of yeast cells a G protein-coupled receptor – the...

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Bibliographic Details
Published in:Bioelectrochemistry (Amsterdam, Netherlands) Netherlands), 2007-05, Vol.70 (2), p.542-550
Main Authors: Stoneman, M., Chaturvedi, A., Jansma, D.B., Kosempa, M., Zeng, C., Raicu, V.
Format: Article
Language:English
Subjects:
Cell Membrane - metabolism
Cell suspension
Conductivity
Electric Impedance
Fluorescence
Membrane Proteins - metabolism
Permittivity
Plethysmography, Impedance - methods
Receptors, Mating Factor - metabolism
Saccharomyces cerevisiae
Saccharomyces cerevisiae - metabolism
Saccharomyces cerevisiae Proteins - metabolism
Spectrometry, Fluorescence - methods
Tag-free detection
Yeast
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Summary:We have investigated the origin of the dielectric response of the plasma membrane of living yeast cells ( Saccharomyces cerevisiae) by using radiofrequency dielectric spectroscopy. The cells were genetically engineered to overexpress in the membrane of yeast cells a G protein-coupled receptor – the Sterile2-α factor receptor protein (Ste2p) – fused to the green fluorescent protein (GFP). Presence of the Ste2-GFP proteins in the plasma membrane was confirmed by exciting the cells at 476 nm and observing with a confocal microscope the emission characteristic of the GFP from individual cells. The dielectric behavior of cells suspended in KCl solution was analyzed over the frequency range 40 Hz–110 MHz and compared to the behavior of control cells that lacked the ability to express Ste2p. A two-shell electrical cell model was used to fit the data starting from known structural parameters and adjustable electrical phase parameters. The best-fit value for the relative permittivity of the plasma membrane showed no significant difference between cells expressing Ste2p (1.63 ± 0.11) and the control cells (1.75 ± 0.16). This result confirmed earlier predictions that the dielectric properties of the plasma membrane in the radiofrequency range mostly reflect the properties of the hydrophobic layer of the membrane, which is populated by the hydrocarbon tails of the phospholipids and hydrophobic segments of integral membrane proteins. We discuss ways by which dielectric spectroscopy can be improved to be used for tag-free detection of proteins on the membrane.
ISSN:1567-5394
1878-562X
DOI:10.1016/j.bioelechem.2006.12.008