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1. In Situ Quantification of Biological N ₂ Production Using Naturally Occurring ¹⁵ N ¹⁵ N

   https://doi.org/10.1021/acs.est.9b00812  

   Yeung, Laurence Y.; Haslun, Joshua A.; Ostrom, Nathaniel E.; Sun, Tao; Young, Edward D.; van Kessel, Maartje A. H. J.; Lücker, Sebastian; Jetten, Mike S. M. (April 2019, Environmental Science & Technology)
2. Solvent Effects in Hyperpolarization of ¹⁵ N Nuclei in [ ¹⁵ N ₃ ]Metronidazole and [ ¹⁵ N ₃ ]Nimorazole Antibiotics via SABRE‐SHEATH**

   https://doi.org/10.1002/anse.202400045  

   Yi, Anna_P; Salnikov, Oleg_G; Burueva, Dudari_B; Chukanov, Nikita_V; Chekmenev, Eduard_Y; Koptyug, Igor_V (August 2024, Analysis & Sensing)

   Abstract Metronidazole and nimorazole are antibiotics of a nitroimidazole group which also may be potentially utilized as hypoxia radiosensitizers for the treatment of cancerous tumors. Hyperpolarization of¹⁵N nuclei in these compounds using SABRE‐SHEATH (Signal Amplification By Reversible Exchange in SHield Enables Alignment Transfer to Heteronuclei) approach provides dramatic enhancement of detection sensitivity of these analytes using magnetic resonance spectroscopy and imaging. Methanol‐d₄is conventionally employed as a solvent in SABRE hyperpolarization process. Herein, we investigate SABRE‐SHEATH hyperpolarization of isotopically labeled [¹⁵N₃]metronidazole and [¹⁵N₃]nimorazole in nondeuterated methanol and ethanol solvents. Optimization of such hyperpolarization parameters as polarization transfer magnetic field, temperature, parahydrogen flow rate and pressure allowed us to obtain an average¹⁵N polarization of up to 7.2–7.4 % for both substrates. The highest¹⁵N polarizations were observed in methanol‐d₄for [¹⁵N₃]metronidazole and in ethanol for [¹⁵N₃]nimorazole. At a clinically relevant magnetic field of 1.4 T the¹⁵N nuclei of these substrates possess long characteristic hyperpolarization lifetimes (T₁) of ca. 1 to ca. 7 min. This study represents a major step toward SABRE in more biocompatible solvents, such as ethanol, and also paves the way for future utilization of these hyperpolarized nitroimidazoles as molecular contrast agents for MRI visualization of tumors. 

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3. Synthesis and ¹⁵ N NMR Signal Amplification by Reversible Exchange of [ ¹⁵ N]Dalfampridine at Microtesla Magnetic Fields

   https://doi.org/10.1002/cphc.202100109  

   Chukanov, Nikita_V; Salnikov, Oleg_G; Trofimov, Ivan_A; Kabir, Mohammad_S_H; Kovtunov, Kirill_V; Koptyug, Igor_V; Chekmenev, Eduard_Y (April 2021, ChemPhysChem)

   Abstract Signal Amplification by Reversible Exchange (SABRE) technique enables nuclear spin hyperpolarization of wide range of compounds using parahydrogen. Here we present the synthetic approach to prepare¹⁵N‐labeled [¹⁵N]dalfampridine (4‐amino[¹⁵N]pyridine) utilized as a drug to reduce the symptoms of multiple sclerosis. The synthesized compound was hyperpolarized using SABRE at microtesla magnetic fields (SABRE‐SHEATH technique) with up to 2.0 %¹⁵N polarization. The 7‐hour‐long activation of SABRE pre‐catalyst [Ir(IMes)(COD)Cl] in the presence of [¹⁵N]dalfampridine can be remedied by the use of pyridine co‐ligand for catalyst activation while retaining the¹⁵N polarization levels of [¹⁵N]dalfampridine. The effects of experimental conditions such as polarization transfer magnetic field, temperature, concentration, parahydrogen flow rate and pressure on¹⁵N polarization levels of free and equatorial catalyst‐bound [¹⁵N]dalfampridine were investigated. Moreover, we studied¹⁵N polarization build‐up and decay at magnetic field of less than 0.04 μT as well as¹⁵N polarization decay at the Earth's magnetic field and at 1.4 T. 

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4. ¹⁴ N to ¹⁵ N Isotopic Exchange of Nitrogen Heteroaromatics through Skeletal Editing

   https://doi.org/10.1021/jacs.3c11515  

   Bartholomew, G. Logan; Kraus, Samantha L.; Karas, Lucas J.; Carpaneto, Filippo; Bennett, Raffeal; Sigman, Matthew S.; Yeung, Charles S.; Sarpong, Richmond (January 2024, Journal of the American Chemical Society)
5. Detection of ¹⁵ N-labeled metabolites in microbial extracts using AI-designed broadband pulses for ¹ H, ¹⁵ N heteronuclear NMR spectroscopy

   https://doi.org/10.1039/d5an00074b  

   VS, Manu; Tonelli, Marco; Bell, Bailey; Sharma, Alok K; Bugni, Tim S; Veglia, Gianluigi (April 2025, The Analyst)

   New AI-designed RF pulses increase bandwidth and sensitivity for¹H-¹⁵N HSQC spectra of metabolites. 

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