Measurements of the persistent singlet state of N2O in blood and other solvents - potential as a magnetic tracer

The development of hyperpolarized tracers has been limited by short nuclear polarization lifetimes. The dominant relaxation mechanism for many hyperpolarized agents in solution arises from intramolecular nuclear dipole–dipole coupling modulated by molecular motion. It has been previously demonstrated that nuclear spin relaxation due to this mechanism can be removed by storing the nuclear polarization in long-lived, singlet-like states. In the case of N2O, storing the polarization of the nitrogen nuclei has been shown to substantially increase the polarization lifetime. The feasibility of utilizing N2O as a tracer is investigated by measuring the singlet-state lifetime of the N2O when dissolved in a variety of solvents including whole blood. Comparison of the singlet lifetime to longitudinal relaxation and between protonated and deuterated solvents is consistent with the dominance of spin-rotation relaxation, except in the case of blood

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