Labeling membranes with fluorescent cholesterols

Cholesterol, an essential component of most cellular membranes, is present in the plasma membrane and is enriched within lipid rafts. It is, however, virtually absent from the mitochondrial inner membrane, and there is little within the endoplasmic reticulum. Dehydroergosterol (DHE), a fluorescent cholesterol analog, has been found to effectively label membranes and has been used to monitor cholesterol distribution and trafficking within live cells. Other cholesterol-based probes, such as NBD (N-(7-nitrobenz-2-oxa-1,3-diazole-4-yl))-cholesterol, are commercially available (from Molecular Probes). However, cell labeling using the NBD-cholesterol analogs frequently does not show the same labeling pattern as for DHE and native cholesterol.