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Hyperpolarized long-lived nuclear spin states in monodeuterated methyl groups.

ABSTRACT: Monodeuterated methyl groups may support a long-lived nuclear spin state, with a relaxation time exceeding the conventional spin-lattice relaxation time T1. Dissolution-DNP (dynamic nuclear polarization) may be used to hyperpolarize such a long-lived spin state. This is demonstrated for the CH2D groups of a piperidine derivative. The polarized sample is manipulated in the ambient magnetic field of the laboratory, without destruction of the hyperpolarized singlet order. Strongly enhanced CH2D signals are observed more than one minute after dissolution, even in the presence of paramagnetic radicals, by which time the NMR signal from the hyperpolarized proton magnetization has completely disappeared.

SUBMITTER: Elliott SJ

PROVIDER: S-EPMC5933006 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Hyperpolarized long-lived nuclear spin states in monodeuterated methyl groups.

Elliott Stuart J SJ Meier Benno B Vuichoud Basile B Stevanato Gabriele G Brown Lynda J LJ Alonso-Valdesueiro Javier J Emsley Lyndon L Jannin Sami S Levitt Malcolm H MH

Physical chemistry chemical physics : PCCP 20180401 15

Monodeuterated methyl groups may support a long-lived nuclear spin state, with a relaxation time exceeding the conventional spin-lattice relaxation time T1. Dissolution-DNP (dynamic nuclear polarization) may be used to hyperpolarize such a long-lived spin state. This is demonstrated for the CH2D groups of a piperidine derivative. The polarized sample is manipulated in the ambient magnetic field of the laboratory, without destruction of the hyperpolarized singlet order. Strongly enhanced CH2D sig ...[more]

PMID: 29595200

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Project description:We report a systematic study of relaxation dynamics of hyperpolarized (HP) propane and HP propane-d6 prepared by heterogeneous pairwise parahydrogen addition to propylene and propylene-d6 respectively. Long-lived spin states (LLS) created for these molecules at the low magnetic field of 0.0475 T were employed for this study. The parahydrogen-induced overpopulation of a HP propane LLS decays exponentially with time constant (TLLS) approximately 3-fold greater than the corresponding T1 values. Both TLLS and T1 increase linearly with propane pressure in the range from 1 atm (the most biomedically relevant conditions for pulmonary MRI) to 5 atm. The TLLS value of HP propane gas at 1 atm is ~3 s. Deuteration of the substrate (propylene-d6) yields hyperpolarized propane-d6 gas with TLLS values approximately 20% shorter than those of hyperpolarized fully protonated propane gas, indicating that deuteration does not benefit the lifetime of the LLS HP state. The use of pH2 or Xe/N2 buffering gas during heterogeneous hydrogenation reaction (leading to production of 100% HP propane (no buffering gas) versus 43% HP propane gas (with 57% buffering gas) composition mixtures) results in (i) no significant changes in T1, (ii) decrease of TLLS values (by 35±7% and 8±7% respectively); and (iii) an increase of the polarization levels of HP propane gas with a propane concentration decrease (by 1.6±0.1-fold and 1.4±0.1-fold respectively despite the decrease in TLLS, which leads to disproportionately greater polarization losses during HP gas transport). Moreover, we demonstrate the feasibility of HP propane cryo-collection (which can be potentially useful for preparing larger amounts of concentrated HP propane, when buffering gas is employed), and TLLS of liquefied HP propane reaches 14.7 seconds, which is greater than the TLLS value of HP propane gas at any pressure studied. Finally, we have explored the utility of using a partial Spin-Lock Induced Crossing (SLIC) radio frequency (RF) pulse sequence for converting the overpopulated LLS into observable 1H nuclear magnetization at low magnetic field. We find that (i) the bulk of the overpopulated LLS is retained even when the optimal or near-optimal values of SLIC pulse duration are employed, and (ii) the overpopulated LLS of propane is also relatively immune to strong RF pulses-thereby, indicating that LLS is highly suitable as a spin-polarization reservoir in the context of NMR/MRI detection applications. The presented findings may be useful for improving the levels of polarization of HP propane produced by HET-PHIP via the use of an inert buffer gas; increasing the lifetime of the HP state during preparation and storage; and developing efficient approaches for ultrafast MR imaging of HP propane in the context of biomedical applications of HP propane gas, including its potential use as an inhalable contrast agent.

Dataset Information

Hyperpolarized long-lived nuclear spin states in monodeuterated methyl groups.

Publications

Hyperpolarized long-lived nuclear spin states in monodeuterated methyl groups.

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