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1. Temperature Cycling Enables Efficient ¹³ C SABRE-SHEATH Hyperpolarization and Imaging of [1- ¹³ C]-Pyruvate

   https://doi.org/10.1021/jacs.1c09581  

   TomHon, Patrick; Abdulmojeed, Mustapha; Adelabu, Isaiah; Nantogma, Shiraz; Kabir, Mohammad Shah; Lehmkuhl, Sören; Chekmenev, Eduard Y.; Theis, Thomas (January 2022, Journal of the American Chemical Society)
2. Two-bond ¹³ C– ¹³ C spin-coupling constants in saccharides: dependencies on exocyclic hydroxyl group conformation

   https://doi.org/10.1039/d1cp03320d  

   Lin, Jieye; Meredith, Reagan J.; Oliver, Allen G.; Carmichael, Ian; Serianni, Anthony S. (October 2021, Physical Chemistry Chemical Physics)

   Seven doubly 13 C-labeled isotopomers of methyl β- d -glucopyranoside, methyl β- d -xylopyranoside, methyl β- d -galactopyranoside, methyl β- d -galactopyranosyl-(1→4)-β- d -glucopyranoside and methyl β- d -galactopyranosyl-(1→4)-β- d -xylopyranoside were prepared, crystallized, and studied by single-crystal X-ray crystallography and solid-state 13 C NMR spectroscopy to determine experimentally the dependence of 2 J C1,C3 values in aldopyranosyl rings on the C1–C2–O2–H torsion angle, θ 2 , involving the C2 carbon of the C1–C2–C3 coupling pathway. Using X-ray crystal structures to determine θ 2 in crystalline samples and by selecting compounds that exhibit a relatively wide range of θ 2 values in the crystalline state, 2 J C1,C3 values measured in crystalline samples were plotted against θ 2 and the resulting plot compared to that obtained from density functional theory (DFT) calculations. For θ 2 values ranging from ∼90° to ∼240°, very good agreement was observed between the experimental and theoretical plots, providing strong validation of DFT-calculated spin-coupling dependencies on exocyclic C–O bond conformation involving the central carbon of geminal C–C–C coupling pathways. These findings provide new experimental evidence supporting the use of 2 J CCC values as non-conventional spin-coupling constraints in MA′AT conformational modeling of saccharides in solution, and the use of NMR spin-couplings not involving coupled hydroxyl hydrogens as indirect probes of C–O bond conformation. Solvomorphism was observed in crystalline βGal-(1→4)-βGlcOCH 3 wherein the previously-reported methanol solvate form was found to spontaneously convert to a monohydrate upon air-drying, leading to small but discernible conformational changes in, and a new crystalline form of, this disaccharide. 

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3. “Direct” ¹³ C Hyperpolarization of ¹³ C‐Acetate by MicroTesla NMR Signal Amplification by Reversible Exchange (SABRE)

   https://doi.org/10.1002/anie.201910506  

   Gemeinhardt, Max E.; Limbach, Miranda N.; Gebhardt, Thomas R.; Eriksson, Clark W.; Eriksson, Shannon L.; Lindale, Jacob R.; Goodson, Elysia A.; Warren, Warren S.; Chekmenev, Eduard Y.; Goodson, Boyd M. (November 2019, Angewandte Chemie International Edition)

   Abstract Herein, we demonstrate “direct”¹³C hyperpolarization of¹³C‐acetate via signal amplification by reversible exchange (SABRE). The standard SABRE homogeneous catalyst [Ir‐IMes; [IrCl(COD)(IMes)], (IMes=1,3‐bis(2,4,6‐trimethylphenyl), imidazole‐2‐ylidene; COD=cyclooctadiene)] was first activated in the presence of an auxiliary substrate (pyridine) in alcohol. Following addition of sodium 1‐¹³C‐acetate, parahydrogen bubbling within a microtesla magnetic field (i.e. under conditions of SABRE in shield enables alignment transfer to heteronuclei, SABRE‐SHEATH) resulted in positive enhancements of up to ≈100‐fold in the¹³C NMR signal compared to thermal equilibrium at 9.4 T. The present results are consistent with a mechanism of “direct” transfer of spin order from parahydrogen to¹³C spins of acetate weakly bound to the catalyst, under conditions of fast exchange with respect to the¹³C acetate resonance, but we find that relaxation dynamics at microtesla fields alter the optimal matching from the traditional SABRE‐SHEATH picture. Further development of this approach could lead to new ways to rapidly, cheaply, and simply hyperpolarize a broad range of substrates (e.g. metabolites with carboxyl groups) for various applications, including biomedical NMR and MRI of cellular and in vivo metabolism. 

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4. Calibration of the carbon isotope composition (δ ¹³ C) of benthic foraminifera: Benthic δ ¹³ C Calibration

   https://doi.org/10.1002/2016PA003072  

   Schmittner, Andreas; Bostock, Helen C.; Cartapanis, Olivier; Curry, William B.; Filipsson, Helena L.; Galbraith, Eric D.; Gottschalk, Julia; Herguera, Juan Carlos; Hoogakker, Babette; Jaccard, Samuel L.; et al (June 2017, Paleoceanography)
5. Order‐Unity ¹³ C Nuclear Polarization of [1‐ ¹³ C]Pyruvate in Seconds and the Interplay of Water and SABRE Enhancement

   https://doi.org/10.1002/cphc.202100839  

   Adelabu, Isaiah; TomHon, Patrick; Kabir, Mohammad S. H.; Nantogma, Shiraz; Abdulmojeed, Mustapha; Mandzhieva, Iuliia; Ettedgui, Jessica; Swenson, Rolf E.; Krishna, Murali C.; Theis, Thomas; et al (December 2021, ChemPhysChem)

   Abstract Signal Amplification By Reversible Exchange in SHield Enabled Alignment Transfer (SABRE‐SHEATH) is investigated to achieve rapid hyperpolarization of¹³C₁spins of [1‐¹³C]pyruvate, using parahydrogen as the source of nuclear spin order. Pyruvate exchange with an iridium polarization transfer complex can be modulated via a sensitive interplay between temperature and co‐ligation of DMSO and H₂O. Order‐unity¹³C (>50 %) polarization of catalyst‐bound [1‐¹³C]pyruvate is achieved in less than 30 s by restricting the chemical exchange of [1‐¹³C]pyruvate at lower temperatures. On the catalyst bound pyruvate, 39 % polarization is measured using a 1.4 T NMR spectrometer, and extrapolated to >50 % at the end of build‐up in situ. The highest measured polarization of a 30‐mM pyruvate sample, including free and bound pyruvate is 13 % when using 20 mM DMSO and 0.5 M water in CD₃OD. Efficient¹³C polarization is also enabled by favorable relaxation dynamics in sub‐microtesla magnetic fields, as indicated by fast polarization buildup rates compared to theT₁spin‐relaxation rates (e. g., ∼0.2 s⁻¹versus ∼0.1 s⁻¹, respectively, for a 6 mM catalyst‐[1‐¹³C]pyruvate sample). Finally, the catalyst‐bound hyperpolarized [1‐¹³C]pyruvate can be released rapidly by cycling the temperature and/or by optimizing the amount of water, paving the way to future biomedical applications of hyperpolarized [1‐¹³C]pyruvate produced via comparatively fast and simple SABRE‐SHEATH‐based approaches. 

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