Click imaging of biochemical processes in living systems.

Understanding the function of biomolecules is crucially dependent on observing the dynamics of their biosynthesis, distribution, and metabolism in their native environment at the cellular and organismal levels rather than their behavior in the isolated samples. Small bioorthogonal functional groups that cause minimal, if any, perturbations of the native structure and function of the target molecule under physiological conditions and react selectively with an appropriately derivatized probe could function as chemical handles that allow selective visualization of the target molecule in the complex biological milieu. Small and generally unreactive, organic azides are ideally suited for this task: they can be carried unnoticed through multiple biosynthetic steps only to be revealed, when desired, by action of a suitably derivatized visualization label.