Phospholipids are a class of lipids which constitute a major component of cell membranes and play important roles in signal transduction. Most phospholipids contain one diglyceride, a phosphate group, and one choline. BioAssay Systems' method provides a simple, direct and high-throughput assay for measuring choline-containing phospholipids in biological samples. In this assay, phospholipids (such as lecithin, lysolecithin and sphingomyelin) are enzymatically hydrolyzed to choline which is determined using choline oxidase and a H2O2 specific dye. The optical density of the pink colored product at 570nm or fluorescence intensity (530/585 nm) is directly proportional to the phospholipid concentration in the sample. This product is for Research Use only and is not intended for diagnostic purposes.