Protein Modification of Lysine with 2-(2-Styrylcyclopropyl)ethanal

A new lysine-reactive cyclopropropyl aldehyde for the covalent modification of proteins was developed. The reagent exploits a divinylcyclopropane-cycloheptadiene rearrangement to render the initial condensation irreversible. A labeling study on eGFP demonstrated excellent chemoselectivity for the modification of amine-nucleophiles with the possibility of subsequent modifications.