Relaxometry of insensitive nuclei: Optimizing dissolution dynamic nuclear polarization

Abstract

We report measurements of spin-lattice relaxation of carbon-13 as a function of the magnetic field ('relaxometry') in view of optimizing dissolution-DNP. The sample is temporarily lifted into the stray field above a high-resolution magnet using a simple and inexpensive 'shuttle'. The signals of arbitrary molecules can be observed at high field with high-resolution and sensitivity. During the dissolution process and subsequent 'voyage' from the polarizer to the NMR magnet, relaxation is accelerated by paramagnetic polarizing agents, but it can be quenched by using scavengers.

Fast Dissolution Dynamic Nuclear Polarization NMR of 13C-Enriched 89Y-DOTA Complex: Experimental and Theoretical Considerations

“…5). In practice, however, T 1 decay and the field gradients [18] experienced by the sample during the dissolution and transfer from the polarizer result in a decrease of nuclear polarization. The dissolution and transfer time in our commercial polarizer is about 8-10 s during which period a substantial amount of the 13 C polarization decays via T 1 (14 s) relaxation, but only a negligible loss of the 89 Y polarization occurs (T 1 = 480 s).…”

A magnetic tunnel to shelter hyperpolarized fluids

“…For DNP, we obviously need polarizing agents such as TEMPO, trityl, but their presence is no longer desirable after dissolution. With a custom-built shuttle relaxometer 11 operating in the stray field of an unshielded 300 MHz wide-bore Oxford Instruments magnet, we have studied the 1 H nuclear spin-lattice relaxation of bromothiophene carboxylate (BTC) (Sigma Aldrich) over a range 1 mT < B 0 < 7.05 T. The shuttle can lift the NMR sample with a stepper motor so that it reaches a field of 1 mT within ca. 1 s. Details about such measurements are given elsewhere.…”

“…1 s. Details about such measurements are given elsewhere. 11 Three samples were prepared, based on a 50 mM stock solution of bromothiophene carboxylate in non-degassed D 2 O. Sample 1 without any additions, sample 2 with the addition of 0.25 mM 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPOL) (Sigma Aldrich), and sample 3 with the addition of 50 mM sodium ascorbate (Sigma Aldrich) which acts as scavenger that quenches both TEMPOL and dissolved O 2 .…”

Cross Polarization for Dissolution Dynamic Nuclear Polarization Experiments at Readily Accessible Temperatures 1.2 < T < 4.2 K

“…Nuclear spins with high gyromagnetic ratios c I such as 1 H and 19 F tend to return rapidly to thermal equilibrium, so that, by the time the samples have arrived in the solution-state NMR or MRI system, the remaining enhancements are modest [6]. Moreover, it is often not feasible to follow a chemical reaction or a metabolic process on the short T 1 time scale of spins with high gyromagnetic ratios.…”