Photoactivatable Alkyne Tag for Photolabeling Biomolecules in Living Cells

Light-induced molecular imaging methods have attracted considerable attention owing to their potential for monitoring changes in the localization of intracellular molecules, which can provide valuable insights into the molecular mechanisms of living systems. In this article, a photoactivatable alkyne tag is developed by modifying an unstable intermediate of the alkyne-forming reaction with a photodegradable protecting group; the photodegradation triggers the conversion of the intermediate into a linear alkyne in an aqueous solution. The developed photoactivatable alkyne tag is incorporated into a cholesterol analog, introduced into living cells, and exposed to a biocompatible dose of 365 nm light. Subsequently, the cholesterol analog in light-irradiated cells is microscopically visualized through alkyne-specific biotinylation via copper-catalyzed azide-alkyne cycloaddition and biotin-specific labeling with fluorescence-labeled streptavidin. The obtained results indicate that the photoactivatable alkyne tag can be photoconverted into alkyne derivatives inside cells and applied to the light-induced intracellular imaging of biomolecules. This photoactivatable chemical tag can potentially expand the range of applications of light-induced molecular imaging of various biomolecules.