NMR Spin-Lock Induced Crossing (SLIC) dispersion and long-lived spin states of gaseous propane at low magnetic field (0.05 T)

Abstract

When parahydrogen reacts with propylene in low magnetic fields (e.g., 0.05 T), the reaction product propane develops an overpopulation of pseudo-singlet nuclear spin states. We studied how the spin-lock induced crossing (SLIC) technique can be used to convert these pseudo-singlet spin states of hyperpolarized gaseous propane into observable magnetization and to detect 1H NMR signal directly at 0.05 T. The theoretical simulation and experimental study of the NMR signal dependence on B1 power (SLIC amplitude) exhibits a well-resolved dispersion, which is induced by the spin-spin couplings in the eight-proton spin system of propane. We also measured the exponential decay time constants (TLLSS or TS) of these pseudo-singlet long-lived spin states (LLSS) by varying the time between hyperpolarized propane production and SLIC detection. We have found that, on average, TS is approximately 3 times longer than the corresponding T1 value under the same conditions in the range of pressures studied (up to 7.6 atm). Moreover, TS may exceed 13 seconds at pressures above 7 atm in the gas phase. These results are in agreement with the previous reports, and they corroborate a great potential of long-lived hyperpolarized propane as an inhalable gaseous contrast agent for lung imaging and as a molecular tracer to study porous media using low-field NMR and MRI.

Ultrafast Single‐Scan 2D NMR Spectroscopic Detection of a PHIP‐Hyperpolarized Protease Inhibitor

“…To that end, it was necessary to convert the antiphase lines of the multiplet polarization into a net polarization. As shown previously, this can be achieved either by an adiabatic‐passage spin order conversion (APSOC), by spin‐lock induced crossing (SLIC) or by applying a so‐called “out‐of‐phase echo” . However, in the case of the five‐spin system, formed by the allyl‐tyrosine fragment, the latter method was found to be more efficient (Figures S2 and S10, Supporting Information).…”

“…However, due to the fact that in the standard batch‐type experiment the PHIP‐active molecule is consumed in the course of hydrogenation, its concentration constantly decreases, which limits the number of increments and, thus, the resolution in the indirect dimension. In principle, this problem can be circumvented by a continuous flow of hyperpolarized products, which however needs a large amount of substrate . A solution to all these limitations is the application of ultrafast (UF) NMR detection schemes, pioneered by the Frydman group in their seminal paper reported in 2002 .…”

High-resolution hyperpolarized in vivo metabolic 13C spectroscopy at low magnetic field (48.7 mT) following murine tail-vein injection

“…Heteronuclear NMR spectroscopic detection involving 13 C and 15 N on this system has been observed to approach ~1 Hz linewidths (determined as full width at half maximum or FWHM), when measuring NMR samples with μL volumes ( e.g ., samples in 5 mm NMR tubes). We note that this system is particularly well suited for the direct NMR measurement of J -couplings of hyperpolarized compounds given its low field strength and excellent field homogeneity [30]. While not utilized for shimming in the reported in vivo study, when used for MRI the XYZ planar gradient coil set is capable of reaching 20 mT/m in all axes with linearity within approximately ±6% across the full FOV of 40 cm.…”

Hyperpolarized NMR Spectroscopy: d‐DNP, PHIP, and SABRE Techniques

“…Another promising approach for increasing the lifetime of hyperpolarized propane is the use of higher pressures. For example, at 7.6 atm, the relaxation time of hyperpolarized propane is about 4.5 s at 9.4 T and about 13 s at 0.05 T …”