Proton-observed carbon-edited NMR spectroscopy in strongly coupled second-order spin systems.
Proton-observed carbon-edited (POCE) NMR spectroscopy is commonly used to measure 13C labeling with higher sensitivity compared to direct 13C NMR spectroscopy, at the expense of spectral resolution. For weakly coupled first-order spin systems, the multiplet signal at a specific proton chemical shift in POCE spectra directly reflects 13C enrichment of the carbon attached to this proton. The present study demonstrates that this is not necessarily the case for strongly coupled second-order spin systems. In such cases NMR signals can be detected in the POCE spectra even at chemical shifts corresponding to protons bound to 12C. This effect is demonstrated theoretically with density matrix calculations and simulations, and experimentally with measured POCE spectra of [3-13C]glutamate.
Henry
Pierre-Gilles
PG
Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA. henry@cmrr.umn.edu
Marjanska
Malgorzata
M
Walls
Jamie D
JD
Valette
Julien
J
Gruetter
Rolf
R
Ugurbil
Kâmil
K
D002247:Carbon Isotopes; D003198:Computer Simulation; D018698:Glutamic Acid / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011522:Protons; D012680:Sensitivity and Specificity
D002247:Carbon Isotopes; D011522:Protons; D018698:Glutamic Acid