Proton NMR of (15)N-choline metabolites enhanced by dynamic nuclear polarization.

Chemical shifts of protons can report on metabolic transformations such as the conversion of choline to phosphocholine. To follow such processes in vivo, magnetization can be enhanced by dynamic nuclear polarization (DNP). We have hyperpolarized in this manner nitrogen-15 spins in (15)N-labeled choline up to 3.3% by irradiating the 94 GHz electron spin resonance of admixed TEMPO nitroxide radicals in a magnetic field of 3.35 T during ca. 3 h at 1.2 K. The sample was subsequently transferred to a high-resolution magnet, and the enhanced polarization was converted from (15)N to methyl- and methylene protons, using the small (2,3)J((1)H,(15)N) couplings in choline. The room-temperature lifetime of nitrogen polarization in choline, T(1)((15)N) approximately 200 s, could be considerably increased by partial deuteration of the molecule. This procedure enables studies of choline metabolites in vitro and in vivo using DNP-enhanced proton NMR

Hyperpolarizing gases via dynamic nuclear polarization and sublimation.

A high throughput method was designed to produce hyperpolarized gases by combining low-temperature dynamic nuclear polarization with a sublimation procedure. It is illustrated by applications to 129Xe nuclear magnetic resonance in xenon gas, leading to a signal enhancement of 3 to 4 orders of magnitude compared to the room-temperature thermal equilibrium signal at 7.05 T

Investigation of the potential of the dissolution dynamic nuclear polarization method for general sensitivity enhancement in small-molecule NMR spectroscopy

We report results of applying a commercial implementation of the dissolution dynamic nuclear polarization (DNP) methodology developed by K. G. Golman et al. to a range of molecular species in the mass range of 100-400 Da. The molecules are typical of those that might be encountered in natural product chemistry or pharmaceutical analysis. Using an experimental protocol previously reported, in combination with the ERETIC method for generating a reference signal for estimation of concentrations, we determine the signal enhancement and high-field, liquid-state T-1 values for many of the carbon atoms in the six species studied. The results presented in this work suggest that the measured variation in nuclear magnetic resonance enhancements within a given molecule, arising from the dissolution DNP method, is accounted for principally by relaxation of C-13 atoms towards thermal polarization values in the liquid state. We conclude that dissolution DNP will be able to be employed for a wide range of chemical species, provided that the total time taken for dissolution and transfer of solutions is comparable to, or shorter than, the high-field, liquid-state T-1 values in the species being studied