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1. The SABRE project and the SABRE Proof-of-Principle

   https://doi.org/10.1140/epjc/s10052-019-6860-y  

   Antonello, M. ; Barberio, E. ; Baroncelli, T. ; Benziger, J. ; Bignell, L. J. ; Bolognino, I. ; Calaprice, F. ; Copello, S. ; D’Angelo, D. ; D’Imperio, G. ; et al ( April 2019 , The European Physical Journal C)
2. Rational ligand choice extends the SABRE substrate scope

   https://doi.org/10.1039/d0cc01330g  

   Colell, Johannes F. ; Logan, Angus W. ; Zhou, Zijian ; Lindale, Jacob R. ; Laasner, Raul ; Shchepin, Roman V. ; Chekmenev, Eduard Y. ; Blum, Volker ; Warren, Warren S. ; Malcolmson, Steven J. ; et al ( January 2020 , Chemical Communications)

   Here we report on chelating ligands for Signal Amplification By Reversible Exchange (SABRE) catalysts that permit hyperpolarisation on otherwise sterically hindered substrates. We demonstrate 1 H enhancements of ∼100-fold over 8.5 T thermal for 2-substituted pyridines, and smaller, yet significant enhancements for provitamin B 6 and caffeine. We also show 15 N-enhancements of ∼1000-fold and 19 F-enhancements of 30-fold. 

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3. Quantifying the effects of quadrupolar sinks via 15 N relaxation dynamics in metronidazoles hyperpolarized via SABRE-SHEATH

   https://doi.org/10.1039/D0CC03994B  

   Birchall, Jonathan R. ; Kabir, Mohammad S. ; Salnikov, Oleg G. ; Chukanov, Nikita V. ; Svyatova, Alexandra ; Kovtunov, Kirill V. ; Koptyug, Igor V. ; Gelovani, Juri G. ; Goodson, Boyd M. ; Pham, Wellington ; et al ( January 2020 , Chemical Communications)

   15 N spin–lattice relaxation dynamics in metronidazole- 15 N 3 and metronidazole- 15 N 2 isotopologues are studied for rational design of 15 N-enriched biomolecules for signal amplification by reversible exchange in microtesla fields. 15 N relaxation dynamics mapping reveals the deleterious effects of interactions with the polarization transfer catalyst and a quadrupolar 14 N nucleus within the spin-relayed 15 N– 15 N network. 

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4. SABRE enhancement with oscillating pulse sequences

   https://doi.org/10.1039/d2cp00899h  

   Li, Xiaoqing ; Lindale, Jacob R. ; Eriksson, Shannon L. ; Warren, Warren S. ( May 2022 , Physical Chemistry Chemical Physics)

   SABRE (Signal Amplification by Reversible Exchange) methods provide a simple, fast, and cost-effective method to hyperpolarize a wide variety of molecules in solution, and have been demonstrated with protons and, more recently, with heteronuclei (X-SABRE). Here, we present several oscillating pulse sequences that use magnetic fields far away from the resonance condition of continuous excitation and can commonly triple the polarization. An analysis with average Hamiltonian theory indicates that the oscillating pulse, in effect, adjusts the J-couplings between hydrides and target nuclei and that a much weaker coupling produces maximum polarization. This theoretical treatment, combined with simulations and experiment, shows substantial magnetization improvements relative to traditional X-SABRE methods. It also shows that, in contrast to most pulse sequence applications, waveforms with reduced time symmetry in the toggling frame make magnetization generation more robust to experimental imperfections. 

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5. Improving SABRE hyperpolarization with highly nonintuitive pulse sequences: Moving beyond avoided crossings to describe dynamics

   https://doi.org/10.1126/sciadv.abl3708  

   Eriksson, Shannon L. ; Lindale, Jacob R. ; Li, Xiaoqing ; Warren, Warren S. ( March 2022 , Science Advances)

   New pulse sequences yield improved polarization for SABRE experiments and reframe our theoretical understanding of the dynamics. 

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