High‐resolution ¹H NMR spectroscopy in a live mouse subjected to 1.5 Hz magic angle spinning

Abstract

It is demonstrated that the resolution of the 1 H NMR metabolite spectrum in a live mouse can be significantly enhanced by an ultraslow magic angle spinning of the animal combined with a modified phase-corrected magic angle turning (PHORMAT) pulse sequence. Proton NMR spectra were measured of the torso and the top part of the belly of a female BALBc mouse in a 2 T field while spinning the animal at a speed of 1.5 Hz. It was found that even in this relatively low field, with PHORMAT an isotropic spectrum is obtained with line widths that are a factor of 4.6 smaller than those obtained in a stationary mouse. It is concluded that in vivo PHORMAT has the potential to significantly increase the utility of 1 H NMR spectroscopy for biochemical and biomedical animal research. Magn Reson Med 50: 1113-1119, 2003.

Localized intermolecular zero‐quantum coherence spectroscopy in vivo

“…However, in cases where field inhomogeneities cannot be avoided by either shimming or localization, alternative methods are required. These include for example introduction of a second spectral dimension to increase resonance line dispersion (6), magnetic susceptibility matching of sample and probe compartments (7), or magic angle spinning techniques (8). Nearly complete removal of inhomogeneous line broadening can be achieved along the indirect dimension in 2D experiments, which are designed to use relative frequency differences between nearby spins to create frequency dispersion.…”

“…Again because of experimental imperfections and relaxation a residual axial peak is observed. Equation [8] describes a faster signal build-up and doubled cross-peak intensity compared to Eq. [7].…”

“…Equation [9] (solid lines) is compared with the solution neglecting relaxation (dotted line, Eq. [8]) and the exponential signal decay in a conventional 1D experiment (dashed lines). The damped HOMOGENIZED signal reaches a dramatically lower maximum intensity after shorter evolution time.…”

New Methodology For Use in Rotating Field Nuclear MagneticResonance

“…On the other hand, slow spinning techniques are essential for a variety of experiments including rotating field NMR (Chapter 5), intact organ studies, and living animal studies. [46] Pulse se-quences such as 1D-Total Sideband Suppression(1D-TOSS) [47] and 2D-Phase Altered Sideband Suppression (2D-PASS) [48] have been used to study excised human tissue. [44] [49]…”

“…Other sequences like Magic Angle Hopping (MAH) [50],which uses three distinct stationary positions, and Magic Angle Turning (MAT) [51] [52] [53] have been used to take spectra of metabolites in tissue and organs for both excised tissues [54] and a living mouse. [46] Slow spinning speed is an arbitrary term, but generally implies that the sample rotates significantly more slowly than the time scale of the anisotropy. When spinning slower than the anisotropy, sidebands emerge at the rotor's spinning frequency.…”