Application of 15N2-Diazirines as a Versatile Platform for Hyperpolarization of Biological Molecules by d-DNP

15N2-Diazirines represent an attractive class of imaging tags for hyperpolarized magnetic resonance imaging (HP-MRI), offering desirable biocompatibility, ease of incorporation into a variety of molecules, and ability to deliver long-lasting polarization. We have recently established hyperpolarization of 15N2-diazirines in organic solvents using SABRE-Shield Enables Alignment Transfer to Heteronuclei (SABRE-SHEATH). Yet, the current challenge of SABRE-SHEATH in water, specifically poor polarization efficiency, presents a barrier in examining practical use of 15N2-diazirines for HP-MRI. Herein, we show that efficient polarization of diverse 15N2-diazirine-labeled molecules in water can be readily achieved by dissolution dynamic nuclear polarization (d-DNP), a hyperpo-larization technique used in clinical practice. Hyperpolarization by d-DNP also demonstrates greater enhancement for long-lasting 15N signals, in comparison with SABRE-SHEATH. Various biologically important molecules are studied in this work, ...