OPA-based bifunctional linker for protein labeling and profiling

Lysine residue has been considered as a routine conjugating site for protein chemical labeling and modification. The commercially available lysine labeling agents have several limitations in labeling efficiency, stability and cost. To pursue alternative protein lysine labeling strategies, herein, we report the development of ortho-phthalaldehyde (OPA)-based bifunctional linker suitable for protein chemi-cal labeling and profiling. Among three designed OPA-based bifunctional linkers, OPA-NH-alkyne 5 was proved to be optimal for protein labeling with minimal protein turbidity. We further demonstrated OPA-NH-alkyne 5 was applicable for immediate cap-ture of protein or proteome chemical labeling.