Fatty acid composition of isolated lipid droplets and young adult
nematodeswas determined by gas chromatography/mass spectrometry
(GC/MS) as previously described [30,31]. Separation of the TAG and
phospholipid fractions used a two-solvent TLC protocol. Lipids were extracted
by adding 5 ml of ice-cold chloroform:methanol (1:1) and incubating
overnight at 20 °C with occasional shaking. A solution of 0.2 M
H3PO4 and 1 M KCl was added to samples, which resulted in phase
separation of the organic and aqueous phase. The organic phase was
removed and dried under argon, then resuspended in chloroform.
Samples were loaded in triplicate, and TLC plates were developed two
thirds of the way up the plate in the first solvent system: chloroform:
methanol:water:acetic acid (65:43:3:2.5), dried, and then the second
solvent system hexane:diethylether:acetic acid (80:20:2) was developed
to the top of the plate. Lipids were visualized under UV light
after spraying the platewith 0.005% primuline, and spots corresponding
to TAG and themajor phospholipidswere scraped, spikedwith a known
standard (15:0), and transesterified for GC/MS analysis to determine
the fatty acid composition as well as to determine the relative levels of
TAG, phosphatidylethanolamine (PE), and phosphatidylcholine (PC)
fractions. At least three biological replicates were used for TLC analysis.
Significancewas determined by t-test calculation using GraphPad Prism
5 software.
2.5. Cholesterol assay
Cholesterol