Use of a filter-paper disk assay in the measurement of lipid biosynthesis.

The precipitation by trichloroacetic acid (TCA) of radioactive lipids on disks of filter-paper, followed by extraction with TCA and water to remove soluble radioactive precursors, provides the means for a convenient assay for lipid biosynthesis. Large numbers of disks can be washed in the same vessel, dried, and assayed for radioactivity with liquid scintillation counting equipment. Extraction of disks with lipid solvents provides a convenient control for the possible presence of TCA- and water-insoluble, nonlipid products. The application of the method to the assay of cyclopropane fatty acid synthetase is shown.