Bioorthogonal site-specific chemical reaction to label biomolecules in vitro and in
living cells is one of the most powerful and convenient tools in chemical biology.
Reactive pairs frequently used for chemical conjugation are aldehydes/ketones with
hydrazines/hydrazides/hydroxylamines. Although the reaction is generally specific
for the two components, even in a cellular environment, the reaction is very slow
under physiological conditions. Addition of a phosphate group at the ortho position of an aromatic aldehyde increases the reaction rate by an order of magnitude
and enhances the aqueous solubility of the reagent and the product. We have synthesized
phosphate-substituted aldehyde synthetic models to study kinetics of their reactions
with hydrazines and hydrazides that contain a fluorophore. This rapid bioorthogonal
reaction should therefore be potentially a very useful reaction for routine site-specific
chemical ligations to study and image complex cellular processes in biological systems.
Key words
site-specific conjugation - kinetics - bioorthogonal reaction
