Exchange rates of creatine kinase metabolites: Feasibility of imaging creatine by chemical exchange saturation transfer MRI

Mohammad Haris, Ravi Prakash Reddy Nanga, Anup Singh, Kejia Cai, Feliks Kogan, Hari Hariharan, Ravinder Reddy

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Creatine (Cr), phosphocreatine (PCr) and adenosine-5-triphosphate (ATP) are major metabolites of the enzyme creatine kinase (CK). The exchange rate of amine protons of CK metabolites at physiological conditions has been limited. In the current study, the exchange rate and logarithmic dissociation constant (pKa) of amine protons of CK metabolites were calculated. Further, the chemical exchange saturation transfer effect (CEST) of amine protons of CK metabolites with bulk water was explored. At physiological temperature and pH, the exchange rate of amine protons in Cr was found to be 7-8 times higher than PCr and ATP. A higher exchange rate in Cr was associated with lower pKa value, suggesting faster dissociation of its amine protons compared to PCr and ATP. CEST MR imaging of these metabolites in vitro in phantoms displayed predominant CEST contrast from Cr and negligible contribution from PCr and ATP with the saturation pulse parameters used in the current study. These results provide a new method to perform high-resolution proton imaging of Cr without contamination from PCr. Potential applications of these finding are discussed.

Original languageEnglish
Pages (from-to)1305-1309
Number of pages5
JournalNMR in Biomedicine
Issue number11
Publication statusPublished - Nov 2012
Externally publishedYes



  • Acid dissociation constant
  • Adenosine-5-triphosphate
  • Chemical exchange saturation transfer
  • Chemical shift
  • Creatine
  • Exchange rate
  • Magnetic resonance imaging
  • Phosphocreatine

ASJC Scopus subject areas

  • Spectroscopy
  • Molecular Medicine
  • Radiology Nuclear Medicine and imaging

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