EPR Spectra of Spin-labeled Fatty Acids in Detergent Solutions: “Immobilized Species” in the Absence of Protein

• Published in: Applied magnetic resonance Vol. 37; no. 1-4; pp. 455 - 461
• Main Authors: Kuntz, Stefan, Leinisch, Fabian, Hideg, Kálmán, Trommer, Wolfgang E.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 2010; Springer Nature B.V
• Subjects: Atoms and Molecules in Strong Fields; Detergents; Distilled water; Electron paramagnetic resonance; Ethanol; Fatty acids; Laser Matter Interaction; Lipids; Micelles; Molecular structure; Organic Chemistry; Palmitic acid; Phospholipids; Physical Chemistry; Physics; Physics and Astronomy; Propionic acid; Proteins; Solid State Physics; Solvents; Spectra; Spectroscopy/Spectrometry; Spectrum analysis; Stearic acid; New York; United States > US; Nitroxide; Electron Paramagnetic Resonance; Spin Label; Electron Paramagnetic Resonance Spectrum; Nitroxide Group
• ISSN: 0937-9347; 1613-7507
• DOI: 10.1007/s00723-009-0057-8

Electron paramagnetic resonance spectra of 5-doxyl-stearic acid, 3-(2-Dodecyl-1-oxyl-5,5-dimethylpyrrolidin-2-yl)propanoic acid radical (4-proxyl-palmitic acid) and of 3-(1-Oxyl-2,5-dimethyl-5-dodecylpyrrolidine-2-yl)propanoic acid radical (4-azetoxyl-stearic acid) in lipid micelles of nonaethyleneglycol-monododecyl ether (C 12 E 9 ) and pentaethyleneglycol-monooctyl ether (C 8 E 5 ) can reveal immobilized components typical of spin-labeled protein-bound fatty acids as well as phospholipids. The occurrence of such species depends on the detergent, the relative orientation of the nitroxide group with respect to the longitudinal axis and the molecular structure of the fatty acid as well as on polarity and ionic strength of the aqueous phase. Whereas 5-doxyl-stearic acid and 4-proxyl-palmitic acid exhibited these highly immobilized components in C 12 E 9 micelles but not in C 8 E 5 , only a single relatively mobile component was observed with 4-azetoxyl-stearic acid in both detergents. The immobilized component is lost by the addition of isopropanol but not as much by ethanol and also when distilled water is substituted for the buffer.