31P NMR detection of mobile dog brain phospholipids

The in vivo dog brain 31P NMR spectrum has a large peak in the phosphodiester region accounting for more than 35% of the total observable phosphorus metabolites. It is possible to reduce the intensity of this peak by off-resonance saturation. To characterize the nature of this peak, extracts of dog brain frozen in situ were analyzed by high resolution 31P NMR. ATP, phosphocreatine, inorganic phosphate, and phosphomonoesters were recovered in appropriate amounts in the methanol:HCl extract. However, acid soluble phosphodiesters accounted for only 8% of the observable phosphorus. More NMR observable phosphodiesters were selectively recovered following CHCl3:methanol extraction of phospholipids. These results suggest that the in vivo phosphodiester resonance has substantial contributions from a fraction of mobile brain phospholipids.