Metabolic and covalent labeling of glycans for in vivo imaging of the glycome. Cells metabolize azido sugars such as N-azidoacetylmannosamine (ManNAz), which is converted into the corresponding azido sialic acid (SiaNAz) and incorporated into cellular glycans. The azides are selectively reacted with a fluorescent probe conjugated to a cyclooctyne reagent termed “DIFO.” The fluorescent dye-labeled glycans are then visualized. Using this two-step method, changes in the glycome can be probed within the physiologically authentic environment of a live organism.

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