This product is a fluorescent analog of natural C6:0-phytosphingosine. The 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) fluorescent group has been shown to have only a small influence on lipid adsorption into cells and cellular membranes. This fluorescent analog of natural phytoceramide is comparable to C6:0-phytoceramide in many biological functions, such as lipid uptake and transport,1 but is not active in all systems. While human glucosylceramide synthase readily takes up and glycosilates C6:0-NBD-phytoceramide the fungal Cryptococcus neoformans does not.2 Phytosphingosine is a long-chain sphingoid base having important cellular functions such as signaling, cytoskeletal structure, celluar cycle, and heat stress response. Phytosphingosine can lead to apoptosis via two distinct pathways and has been investigated as a possible cancer therapeutic treatment.3 Phytoceramides (fatty acid acylated to Phytosphingosine) are distributed at the microvillous membrane of the epithelial cells of the small intestine. Crypt cells and the adjacent epithelial cells produce phytosphingoglycolipids in much greater quantities than more differentiated epithelial cells.4 The kidney and skin also contain phytosphingoglycolipids although in much lower concentrations than in the small intestine. Phytoceramides form part of the water barrier lipids of the skin.