文摘
<sup>15sup>N nuclear spins of imidazole-<sup>15sup>N<sub>2sub> were hyperpolarized using NMR signal amplification by reversible exchange in shield enables alignment transfer to heteronuclei (SABRE-SHEATH). A <sup>15sup>N NMR signal enhancement of ∼2000-fold at 9.4 T is reported using parahydrogen gas (∼50% para-) and ∼0.1 M imidazole-<sup>15sup>N<sub>2sub> in methanol:aqueous buffer (∼1:1). Proton binding to a <sup>15sup>N site of imidazole occurs at physiological pH (pK<sub>asub> ∼ 7.0), and the binding event changes the <sup>15sup>N isotropic chemical shift by ∼30 ppm. These properties are ideal for in vivo pH sensing. Additionally, imidazoles have low toxicity and are readily incorporated into a wide range of biomolecules. <sup>15sup>N-Imidazole SABRE-SHEATH hyperpolarization potentially enables pH sensing on scales ranging from peptide and protein molecules to living organisms.