Journal of the American Chemical Society, Vol.138, No.26, 8080-8083, 2016
Over 20% N-15 Hyperpolarization in Under One Minute for Metronidazole, an Antibiotic and Hypoxia Probe
Direct NMR hyperpolarization of naturally abundant N-15 sites in metronidazole is demonstrated using SABRE-SHEATH (Signal Amplification by Reversible Exchange in SHield Enables Alignment Transfer to Heteronuclei). In only a few tens of seconds, nuclear spin polarization P-N(15) of up to similar to 24% is achieved using parahydrogen with 80% para fraction corresponding to P-N(15) 32% if similar to 100% parahydrogen were employed (which would translate to a signal enhancement of similar to 0.1-million fold at 9.4 T). In addition to this demonstration on the directly binding N-15 site (using J(H-)(N)(2)(15)), we also hyper polarized more distant 15N sites in metronidazole using longer-range spin-spin couplings (J(H)(4)-(N)(15) and J(H)(5)-(N)(15)). Taken together, these results significantly expand the range of molecular structures and sites amenable to hyper polarization via low-cost parahydrogen-based methods. In particular, hyperpolarized nitroimidazole and its derivatives have powerful potential applications such as direct in vivo imaging of mechanisms of action or hypoxia sensing.