Triazoles as T2-Exchange Magnetic Resonance Imaging Contrast Agents for the Detection of Nitrilase Activity

Jia Zhang, Zheng Han, Jiaqi Lu, Yuguo Li, Xuhe Liao, Peter C Van Zijl, Xing Yang, Guanshu Liu

Research output: Contribution to journalArticle


We characterized the T2-exchange (T2ex) magnetic resonance imaging (MRI) contrast of azole protons that have large chemical shifts from the water proton resonance as a function of pH, temperature, and chemical modification. Our results showed that 1,2,4-triazoles could be tuned into excellent diamagnetic T2ex contrast agents, with an optimal exchange-based relaxivity r2ex of 0.10 s−1 mm−1 at physiological pH and B0=9.4 T. A fit of r2ex data to the Swift–Connick equation indicated that imino proton exchange of triazoles is dominated by a base-catalyzed process at higher pH values and an acid-catalyzed process at lower pH. The magnitude of r2ex was also found to be heavily dependent on chemical modifications, that is, enhanced by electron-donating groups, such as amines and methyls, or by intramolecular hydrogen bonding between the imino proton and the carboxyl, and weakened by electron-withdrawing groups like bromo, cyano, and nitro. In light of these findings, we applied T2ex MRI to assess the activity of nitrilase, an enzyme catalyzing the hydrolysis of 1,2,4-triazole-3-carbonitrile to 1,2,4-triazole-3-carboxylic acid, resulting in the enhancement of R2ex. Our findings suggest that 1,2,4-triazoles have potential to provide sensitive and tunable diagnostic probes for MRI.

Original languageEnglish (US)
JournalChemistry - A European Journal
StateAccepted/In press - Jan 1 2018


  • nitrilase
  • swift–connick equation
  • T-exchange MRI
  • triazoles

ASJC Scopus subject areas

  • Chemistry(all)

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