Figure 6.

After depriving cho2opi3 cells of choline for 16 h, the acyl chain profile of newly synthesized PC (black columns) strongly resembles that of the remaining PC pool (white columns). D₁₃-choline was added to a concentration of 0.2 mM, to cho2opi3 cells cultured without choline for 16 h. After 10 min, cells were harvested, and total lipid extracts were prepared. The PC species profiles were analyzed by ESI-MS/MS in the parent ion scan mode at m/z 197 for newly synthesized D₁₃-PC and at m/z 184 for unlabeled PC. For comparison, cho2opi3 cells grown in the presence of 1 mM choline for 16 h were pulse labeled for 10 min with 0.2 mM D₁₃-choline after transfer to choline-free medium and analyzed for PC species profiles (bottom). The relative abundances of the four major PC species are shown as percentages of total PC, averaged from two independent experiments with the error bars representing the variation.