Premium
Selective suppression of lipid resonances by lipid‐soluble nitroxides in NMR spectroscopy
Author(s) -
Chen Kai,
Lutz Norbert W.,
Wehrle Janna P.,
Glickson Jerry D.,
Swartz Harold M.
Publication year - 1992
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910250112
Subject(s) - chemistry , nuclear magnetic resonance spectroscopy , choline , nitroxide mediated radical polymerization , nmr spectra database , stearate , proton nmr , nuclear magnetic resonance , spectroscopy , resonance (particle physics) , spectral line , organic chemistry , biochemistry , physics , radical polymerization , particle physics , polymer , quantum mechanics , astronomy , copolymer
Abstract The ability of lipid‐soluble nitroxides to suppress selectively the peaks of lipid resonances in 31 P, 1 H, and 13 C NMR spectra was investigated in serum as part ofstudies aimed at using these contrast agents for magnetic resonance imaging and magnetic resonance spectroscopy in vivo. Nitroxides are especially interesting potential contrast agents because they can reversibly be converted in cells to diamagnetic hydroxylamines, with conversion rates that are dependent on the redox potential and the intracellular concentration of oxygen; the characterization of nitroxide‐dependent changes in NMR spectra may therefore be a useful means to measureoxygen‐dependent redox metabolism in vivo. The fatty acid analogs, doxyl stearates, suppressed the methyl resonance of choline and the methyl and methylene peaks of lipids in the 1 H NMR spectra of serum samples. As a consequence, lactate peaks, which were not readily detected became clearly resolved and could be evaluated quantitatively. The 31 P resonance of phosphatidylcholine in the 31 P NMR spectrum was suppressed by 5doxyl stearate and 4‐(N,Ndimethyl‐Nhexadecyl)ammonium‐2,2,6,6‐tetramethylpiperidine‐I‐oxyl, iodide (Cat 16 ). In the 13 C NMR spectrum, the resonances of the methyl groups of choline and the lipids also were broadened significantly by addition of 5‐doxyl stearate. Differential suppression of lipid resonances can be employed to facilitate quantitation of lactate.