Methyl-PEG12-NHS ester is widely used in bioconjugation and chemical modification processes. It serves as a linker molecule to attach polyethylene glycol (PEG) chains to proteins, peptides, or other biomolecules, enhancing their stability, solubility, and biocompatibility. This modification is particularly valuable in drug delivery systems, where PEGylation helps reduce immunogenicity and prolongs the circulation time of therapeutic agents in the bloodstream. Additionally, it is employed in the development of diagnostic tools and biosensors, where it improves the performance and functionality of biomolecules. Its reactive NHS ester group enables efficient coupling with primary amines, making it a versatile reagent in bioconjugation chemistry.