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Spin-label saturation-recovery EPR at W-band: applications to eye lens lipid membranes. J Magn Reson 2011 Sep;212(1):86-94

Date

07/13/2011

Pubmed ID

21745756

Pubmed Central ID

PMC3163743

DOI

10.1016/j.jmr.2011.06.014

Abstract

Saturation-recovery (SR) EPR at W-band (94 GHz) to obtain profiles of the membrane fluidity and profiles of the oxygen transport parameter is demonstrated for lens lipid membranes using phosphatidylcholine (n-PC), stearic acid (n-SASL), and cholesterol analog (ASL and CSL) spin labels, and compared with results obtained in parallel experiments at X-band (9.4 GHz). Membranes were derived from the total lipids extracted from 2-year-old porcine lens cortex and nucleus. Two findings are especially significant. First, measurements of the spin-lattice relaxation times T1 for n-PCs allowed T1 profiles across the membrane to be obtained. These profiles reflect local membrane properties differently than profiles of the order parameter. Profiles obtained at W-band are, however, shifted to longer T1 values compared to those obtained at X-band. Second, using cholesterol analog spin labels and relaxation agents (hydrophobic oxygen and water-soluble NiEDDA), the cholesterol bilayer domain was discriminated in membranes made from lipids of the lens nucleus. However, membranes made from cortical lipids show a single homogeneous environment. Profiles of the oxygen transport parameter obtained from W-band measurements are practically identical to those obtained from X-band measurements, and are very similar to those obtained earlier at X-band for membranes made of 2-year-old bovine cortical and nuclear lens lipids (M. Raguz, J. Widomska, J. Dillon, E.R. Gaillard, W.K. Subczynski, Biochim. Biophys. Acta 1788 (2009) 2380-2388). Results demonstrate that SR EPR at W-band has the potential to be a powerful tool for studying samples of small volume, ∼30 nL, compared with the sample volume of ∼3 μL at X-band.

Author List

Mainali L, Raguz M, Camenisch TG, Hyde JS, Subczynski WK

Author

Witold K. Subczynski PhD Professor in the Biophysics department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Animals
Biological Transport, Active
Cell Membrane
Cholesterol
Data Interpretation, Statistical
Electron Spin Resonance Spectroscopy
Indicators and Reagents
Lens, Crystalline
Lipid Bilayers
Membrane Fluidity
Membrane Lipids
Membranes
Oxygen Consumption
Phosphatidylcholines
Spin Labels
Stearic Acids
Swine