The synthesis, characterization, and use of fluorescently labeled lipid probes to follow transport in living cells at a microscopic level have greatly expanded our knowledge of intracellular lipid trafficking. Although lipids containing a number of covalently attached fluorophores have been synthesized, most transport studies have used lipids labeled with 4-nitrobenzo-2-oxa-l,3-diazole (NBD).** Several lines of evidence suggest that NBD-labeled lipids faithfully mimic their native counterparts (seeref. 1 for review). For example:
