Consecutive Alkylation, Click, and Clip Reactions for the Traceless Methionine-Based Conjugation and Release of Methionine-Containing Peptides

Click reactions have revolutionized research in many areas of science. However, a disadvantage of the high stability of the Click product is that identifying simple treatments for cleanly dissociating the latter under the same guiding principles, i.e., a Clip reaction, remains a challenge. This study demonstrates that electron-deficient alkynes, conveniently installed on methionine residues, can participate in well-known Click (nudeophilic thiol-allene addition) and subsequent Clip reactions (radical thiol-ene addition). To illustrate this concept, a variety of bioconjugates (peptide-peptide; peptide-fluorophore; peptide-polymer; and peptide-protein) were prepared. Interestingly, the Clip reaction of these bioconjugates releases the original peptides concurrent with regeneration of their unmodified methionine residue, in minutes. Moreover, the conjugates demonstrate substantial stability toward endogenous levels of reactive species in bacteria, illustrating the potential for this chemistry in the biosciences. The reaction conditions employed in the Click and Clip steps are compatible with the preservation of the integrity of biomolecules/fluorophores and involve readily accessible reagents and the natural functional groups on peptides/proteins.

Automated summary

Click and Clip reactions can be used to prepare bioconjugates, releasing original peptides and regenerating unmodified methionine residues in minutes. These reactions demonstrate substantial stability towards bacterial reactive species and are compatible with the preservation of biomolecules and fluorophores.