The 31P magnetization transfer effects among nuclear magnetic resonances (NMRs) of phosphocreatine (PCr), γ-adenosine-5'-triphosphate (γ-ATP) and inorganic phosphate (Pi) have been attributed to the chemical exchange reactions among PCr, ATP and Pi catalyzed by creatine kinase (CK) and ATPase enzymes and, therefore, are commonly applied in situ to measure chemical exchange fluxes involving two chemically coupled CK and ATPase reactions (i.e., PCr↔ATP↔Pi) by selectively saturating γ-ATP resonance. Besides the expected reductions in the Pi and PCr NMR signals upon saturating γ-ATP resonance, one particularly interesting phenomenon showing decreases in α-ATP and β-ATP signals was also observed. The underlying mechanism was investigated and identified via saturating NMR of β-ATP in the present study. The unique relayed magnetization transfer effects through spin diffusion were observed in the rat brain using in vivo 31P magnetic resonance spectroscopy.
Bibliographical noteFunding Information:
The authors gratefully acknowledge Ms. Alissa Cooper for insightful discussion and manuscript editing. This work was partially supported by NIH grants NS41262 , EB00329 , EB00513 , P41 RR08079 , R21MH092704 and P30NS057091 ; the W.M. Keck Foundation ; and the MIND Institute .
- Chemical exchange
- In vivo P MRS
- Magnetization transfer
- Nuclear Overhauser effect (NOE)
- Spin diffusion