The eukaryotic cell produces many different species of lipids with different characteristics, which have a variety of roles including tuning the properties of organelles. However, how the species are selectively trafficked across the membranes is not completely clear — in part owing to the limits of microscopy techniques. Now, Iglesias-Artola et al. have developed lipid probes that enabled them to track the lipid species using high resolution Fourier-transform mass spectrometry and fluorescence imaging, which they used to obtain kinetics data to map their distribution and sorting mechanisms.

The team of researchers developed minimally modified probes for the main classes of lipids — phosphatidylcholine, phosphatidic acid, phosphatidylethanolamine and sphingomyelin — by introducing both diazirine and alkyne functionalities within the alkyl chain. The probes were then loaded into the cells, photochemically crosslinked and fluorescently labeled to track their localization; alternatively, extraction followed by mass spectrometry enabled analysis of their metabolism. From the fluorescent imaging, Iglesias-Artola et al. were able to observe transport selectivity, which they attributed to the degree of unsaturation, and obtained interorganelle transport rate constants.