Fluorescent labeling of membrane lipid rafts.

Lipid rafts are structures within the plasma membrane that have a different lipid composition than the bulk membrane, specifically being enriched in certain lipids. Lipid rafts are believed to have physiologically important functions. Commercially available kits have been developed (Invitrogen/Molecular Probes) for labeling lipid rafts using a cholera toxin subunit that has been fluorescently tagged with one of several Alexa Fluor dyes. As described in this protocol, cells are labeled while in suspension, after which they can be mounted for imaging.