13C C16Sphingomyelin is an isotopically enriched form of C16sphingomyelin with carbon-13 occurring on the fatty acid portion. It is intended for use as an internal standard for the quantification of C16sphingomyelin by GC- or LC-MS. C16Sphingomyelin is a form of sphingomyelin containing palmitate (16:0) at the variable acylation position. It is the most common form of sphingomyelin found in eggs and is less abundant in the brain and in milk. C16Sphingomyelin interacts with cholesterol in ordered lipid domains (lipid rafts). Sphingomyelinases remove phosphorylcholine from C16sphingomyelin to produce C16 ceramide. While ceramides commonly induce apoptosis, ceramides with different fatty acid chain lengths might direct distinct functions and, in some cases, reduce apoptosis.