Analysis of phospholipid molecular species in brain by (31)P NMR spectroscopy

Techniques are described for the (31)P NMR analysis of glycerophospholipid (PL) headgroup and molecular species in brain. The (31)P NMR spectrum of PLs from human temporal cortex, solubilized in aqueous Na cholate, typically showed 3 major resonances, assigned to phosphatidylcholine (PC) molecular species containing 0, 1, or 2 fully saturated acyl chains. Less species resolution was obtained for the other PL headgroups under these conditions. Alkylacyl- and alkenylacyl-PC were readily discerned using the CHCl(3)-CH(3)OH-H(2)O solvent method. The chain-length, temperature, and species dependences of the (31)P NMR chemical shifts were explored in model PLs. Assignments of signals from phosphatidylethanolamine (PE) subclasses were confirmed in the sodium-cholate system by lipase-mediated selective hydrolysis of bovine-brain PE. The utility of (31)P NMR to monitor enzymatic PL oxidation was further demonstrated. Possible changes in PL composition with postmortem interval (PMI) in rat brain were examined. No significant changes were seen in PL headgroup or PC species composition with PMI at up to 18 hours. Where comparable, the Na-cholate-solubilization and solvent methods gave similar quantitative results for headgroup analysis on the same samples. The present work demonstrates the feasibility and utility of the dual system for analysis of PLs in brain. Magn Reson Med 44:215-223, 2000.