Cysteine‐Specific Multifaceted Bioconjugation of Peptides and Proteins Using 5‐Substituted 1,2,3‐Triazines

Abstract Peptide and protein postmodification have gained significant attention due to their extensive impact on biomolecule engineering and drug discovery, of which cysteine‐specific modification strategies are prominent due to their inherent nucleophilicity and low abundance. Herein, the study introduces a novel approach utilizing multifunctional 5‐substituted 1,2,3‐triazine derivatives to achieve multifaceted bioconjugation targeting cysteine‐containing peptides and proteins. On the one hand, this represents an inaugural instance of employing 1,2,3‐triazine in biomolecular‐specific modification within a physiological solution. On the other hand, as a powerful combination of precision modification and biorthogonality, this strategy allows for the one‐pot dual‐orthogonal functionalization of biomolecules utilizing the aldehyde group generated simultaneously. 1,2,3‐Triazine derivatives with diverse functional groups allow conjugation to peptides or proteins, while bi‐triazines enable peptide cyclization and dimerization. The examination of the stability of bi‐triazines revealed their potential for reversible peptide modification. This work establishes a comprehensive platform for identifying cysteine‐selective modifications, providing new avenues for peptide‐based drug development, protein bioconjugation, and chemical biology research.