N-Succinimidyl acetate is an active ester used as a selective acetylating agent in organic synthesis. It is particularly valuable for introducing acetyl groups to primary amine functionalities, such as lysine residues or N-terminal amines in peptides, proteins, and other biomolecules, under mild aqueous conditions. This modification helps block reactive amines, enhance protein stability, reduce immunogenicity, or prepare acetylated derivatives for biochemical and pharmaceutical research. It is also employed in the synthesis of modified antibodies, therapeutic proteins, and in applications related to drug delivery and diagnostic development.