were from Cayman Chemical Company.
[1-13C]-Palmitic acid, high performance liquid chromatography
(HPLC) grade methanol, and HPLC grade acetonitrile were from Sigma–Aldrich. D. melanogaster (Oregon R) and 4–24 Instant Medium were from Carolina Biological. Silica was from Suppelco. All other reagents were of the highest quality available from commercial sources.