Figure 3.

Metabolic labeling and biorthogonal chemistry. (a) Unnatural biomolecular precursors, included as cell media additives, can be taken up by cells and become incorporated into lipids, carbohydrates or proteins (blue), including those at the cell membrane. (b) Metabolic labeling can be used to present reactive groups that can bind a secondary species (yellow). This is usually mediated by orthogonal click chemistry, in this example, an alkynated secondary species is bound to a cell metabolically labeled with azide groups. (A color version of this figure is available in the online journal.)