Development of a simple method for protein conjugation by copper-free click reaction and its application to antibody-free Western blot analysis.

There are currently many methods available for labeling proteins in order to study their structure and function. However, the utility of these methods is hampered by low efficiency, slow reaction rates, nonbiocompatible reaction conditions, large-sized labeling groups, and the requirement of specific side chains such as cysteine or lysine. In this study, a simple and efficient method for protein labeling was developed, in which an azide-containing amino acid was introduced into a protein and conjugated to a labeling reagent by strain-promoted azide-alkyne cycloaddition (SPAAC).