This compound is widely used in bioconjugation and chemical biology due to its reactive NHS ester group and tetrazine moiety. It enables efficient and selective labeling of biomolecules, such as proteins, peptides, and antibodies, through the NHS ester's reaction with primary amines. The tetrazine group allows for bioorthogonal click chemistry, particularly in inverse electron-demand Diels-Alder (IEDDA) reactions with trans-cyclooctenes (TCOs) or strained alkenes. This makes it valuable for applications like live-cell imaging, drug delivery, and the development of targeted therapeutics. Its PEG4 spacer enhances solubility and reduces steric hindrance, improving conjugation efficiency in complex biological systems.