@article{nantogma_maissin_adelabu_abdurraheem_nelson_chukanov_salnikov_koptyug_lehmkuhl_schmidt_et al._2024, title={Carbon-13 Radiofrequency Amplification by Stimulated Emission of Radiation of the Hyperpolarized Ketone and Hemiketal Forms of Allyl [1-<SUP>13</SUP>C]Pyruvate}, volume={1}, ISSN={["2379-3694"]}, url={http://dx.doi.org/10.1021/acssensors.3c02075}, DOI={10.1021/acssensors.3c02075}, abstractNote={13C hyperpolarized pyruvate is an emerging MRI contrast agent for sensing molecular events in cancer and other diseases with aberrant metabolic pathways. This metabolic contrast agent can be produced via several hyperpolarization techniques. Despite remarkable success in research settings, widespread clinical adoption faces substantial roadblocks because the current sensing technology utilized to sense this contrast agent requires the excitation of 13C nuclear spins that also need to be synchronized with MRI field gradient pulses. Here, we demonstrate sensing of hyperpolarized allyl [1-13C]pyruvate via the stimulated emission of radiation that mitigates the requirements currently blocking broader adoption. Specifically, 13C Radiofrequency Amplification by Stimulated Emission of Radiation (13C RASER) was obtained after pairwise addition of parahydrogen to a pyruvate precursor, detected in a commercial inductive detector with a quality factor (Q) of 32 for sample concentrations as low as 0.125 M with 13C polarization of 4%. Moreover, parahydrogen-induced polarization allowed for the preparation of a mixture of ketone and hemiketal forms of hyperpolarized allyl [1-13C]pyruvate, which are separated by 10 ppm in 13C NMR spectra. This is a good model system to study the simultaneous 13C RASER signals of multiple 13C species. This system models the metabolic production of hyperpolarized [1-13C]lactate from hyperpolarized [1-13C]pyruvate, which has a similar chemical shift difference. Our results show that 13C RASER signals can be obtained from both species simultaneously when the emission threshold is exceeded for both species. On the other hand, when the emission threshold is exceeded only for one of the hyperpolarized species, 13C stimulated emission is confined to this species only, therefore enabling the background-free detection of individual hyperpolarized 13C signals. The reported results pave the way to novel sensing approaches of 13C hyperpolarized pyruvate, potentially unlocking hyperpolarized 13C MRI on virtually any MRI system─an attractive vision for the future molecular imaging and diagnostics.}, journal={ACS SENSORS}, author={Nantogma, Shiraz and Maissin, Henri and Adelabu, Isaiah and Abdurraheem, Abubakar and Nelson, Christopher and Chukanov, Nikita V. and Salnikov, Oleg G. and Koptyug, Igor V. and Lehmkuhl, Soren and Schmidt, Andreas B. and et al.}, year={2024}, month={Jan} }
 @article{schmidt_adelabu_nelson_nantogma_kiselev_zaitsev_abdurraheem_maissin_rosen_lehmkuhl_et al._2023, title={C-13 Radiofrequency Amplification by Stimulated Emission of Radiation Threshold Sensing of Chemical Reactions}, volume={145}, ISSN={["1520-5126"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85160017400&partnerID=MN8TOARS}, DOI={10.1021/jacs.3c00776}, abstractNote={Conventional nuclear magnetic resonance (NMR) enables detection of chemicals and their transformations by exciting nuclear spin ensembles with a radio-frequency pulse followed by detection of the precessing spins at their characteristic frequencies. The detected frequencies report on chemical reactions in real time and the signal amplitudes scale with concentrations of products and reactants. Here, we employ Radiofrequency Amplification by Stimulated Emission of Radiation (RASER), a quantum phenomenon producing coherent emission of 13C signals, to detect chemical transformations. The 13C signals are emitted by the negatively hyperpolarized biomolecules without external radio frequency pulses and without any background signal from other, nonhyperpolarized spins in the ensemble. Here, we studied the hydrolysis of hyperpolarized ethyl-[1-13C]acetate to hyperpolarized [1-13C]acetate, which was analyzed as a model system by conventional NMR and 13C RASER. The chemical transformation of 13C RASER-active species leads to complete and abrupt disappearance of reactant signals and delayed, abrupt reappearance of a frequency-shifted RASER signal without destroying 13C polarization. The experimentally observed "quantum" RASER threshold is supported by simulations.}, number={20}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Schmidt, Andreas B. and Adelabu, Isaiah and Nelson, Christopher and Nantogma, Shiraz and Kiselev, Valerij G. and Zaitsev, Maxim and Abdurraheem, Abubakar and Maissin, Henri and Rosen, Matthew S. and Lehmkuhl, Soren and et al.}, year={2023}, month={May}, pages={11121–11129} }
 @article{nelson_schmidt_adelabu_nantogma_kiselev_abdurraheem_maissin_lehmkuhl_appelt_theis_et al._2022, title={Parahydrogen-Induced Carbon-13 Radiofrequency Amplification by Stimulated Emission of Radiation}, volume={12}, ISSN={["1521-3773"]}, url={https://doi.org/10.1002/anie.202215678}, DOI={10.1002/anie.202215678}, abstractNote={Abstract}, number={5}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Nelson, Christopher and Schmidt, Andreas B. and Adelabu, Isaiah and Nantogma, Shiraz and Kiselev, Valerij G. and Abdurraheem, Abubakar and Maissin, Henri and Lehmkuhl, Soeren and Appelt, Stephan and Theis, Thomas and et al.}, year={2022}, month={Dec} }