SABRE polarized low field rare-spin spectroscopy

The Journal of Chemical Physics, vol. 152, pp. 184202

Abstract

High-field nuclear magnetic resonance (NMR) spectroscopy is an indispensable technique for identification and characterization of chemicals and biomolecular structures. In the vast majority of NMR experiments, nuclear spin polarization arises from thermalization in multi-Tesla magnetic fields produced by superconducting magnets. In contrast, NMR instruments operating at low magnetic fields are emerging as a compact, inexpensive, and highly accessible alternative but suffer from low thermal polarization at a low field strength and consequently a low signal. However, certain hyperpolarization techniques create high polarization levels on target molecules independent of magnetic fields, giving low-field NMR a significant sensitivity boost. In this study, SABRE (Signal Amplification By Reversible Exchange) was combined with high homogeneity electromagnets operating at mT fields, enabling high resolution 1H, 13C, 15N, and 19F spectra to be detected with a single scan at magnetic fields between 1 mT and 10 mT. Chemical specificity is attained at mT magnetic fields with complex, highly resolved spectra. Most spectra are in the strong coupling regime where J-couplings are on the order of chemical shift differences. The spectra and the hyperpolarization spin dynamics are simulated with SPINACH. The simulations start from the parahydrogen singlet in the bound complex and include both chemical exchange and spin evolution at these mT fields. The simulations qualitatively match the experimental spectra and are used to identify the spin order terms formed during mT SABRE. The combination of low field NMR instruments with SABRE polarization results in sensitive measurements, even for rare spins with low gyromagnetic ratios at low magnetic fields.

Authors 8

1. Sören Lehmkuhl corresponding

   North Carolina State University

   Affiliation as printed

   Department of Chemistry, North Carolina State University 1 , 851 Main Campus Dr, Raleigh, North Carolina 27606, USA

2. Martin Suefke

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Energy and Climate Research (IEK-9), Forschungszentrum Jülich GmbH 2 , 52425 Jülich, Germany

3. Arne Kentner Aachen Institute of Technical and Macromolecular Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University 3 , Worringerweg 2, 52056 Aachen, Germany

4. Yi‐Fen Yen

   Massachusetts General Hospital · Athinoula A. Martinos Center for Biomedical Imaging

   Affiliation as printed

   Martinos Center for Biomedical Imaging, Massachusetts General Hospital 4 , Boston, Massachusetts 02129, USA

5. Bernhard Blümich Aachen Institute of Technical and Macromolecular Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University 3 , Worringerweg 2, 52056 Aachen, Germany

6. Matthew Scott Rosen

   Harvard University · Massachusetts General Hospital · Athinoula A. Martinos Center for Biomedical Imaging

   Affiliation as printed

   Department of Physics, Harvard University 5 , Cambridge, Massachusetts 02138, USA

   Martinos Center for Biomedical Imaging, Massachusetts General Hospital 4 , Boston, Massachusetts 02129, USA

7. Stephan Appelt Aachen Institute of Technical and Macromolecular Chemistry

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Central Institute for Engineering, Electronics and Analytics – Electronic Systems (ZEA-2), Forschungszentrum Jülich GmbH 6 , 52425 Jülich, Germany

   Institute of Energy and Climate Research (IEK-9), Forschungszentrum Jülich GmbH 2 , 52425 Jülich, Germany

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University 3 , Worringerweg 2, 52056 Aachen, Germany

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52056 Aachen, Germany

8. Thomas Theis corresponding

   University of North Carolina at Chapel Hill · North Carolina State University

   Affiliation as printed

   Department of Chemistry, North Carolina State University 1 , 851 Main Campus Dr, Raleigh, North Carolina 27606, USA

   Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University 7 , Raleigh, North Carolina 27695, USA