6-Maleimidohexanoic Acid N-Hydroxysuccinimide Ester (EMCS, CAS 55750-63-5) is a cornerstone reagent in modern chemical synthesis and biomolecular labeling, celebrated for its precise reactivity. Understanding its chemical properties is crucial for researchers and manufacturers aiming to leverage its potential in various applications, from pharmaceutical intermediates to advanced biological research.

The molecular structure of EMCS is designed for targeted conjugation. The maleimide moiety is a potent electrophile, readily undergoing a Michael addition reaction with nucleophilic sulfhydryl (-SH) groups, commonly found in cysteine residues of proteins. This reaction forms a stable thioether linkage. Concurrently, the N-hydroxysuccinimide (NHS) ester at the other end of the molecule is an activated ester that reacts efficiently with primary amine (-NH2) groups, typically found in lysine residues of proteins or at the N-terminus. This reaction yields a stable amide bond.

This dual reactivity allows EMCS to function as a versatile crosslinker. For instance, in protein labeling, researchers can first react the maleimide end with a thiol-containing molecule (like a fluorescent dye or a drug) and then use the NHS ester to attach this complex to an amine-bearing protein. Alternatively, the process can be reversed. This controlled approach is vital for creating antibody-drug conjugates (ADCs) where precise drug attachment to an antibody is critical for efficacy and safety. Pharmaceutical companies often buy EMCS from specialized manufacturers in China to ensure they have a reliable supply of this high-purity intermediate.

Beyond protein modification, EMCS serves as a valuable building block in complex chemical synthesis pathways. Its functional groups can be selectively manipulated to construct larger, more intricate molecules. For those in need of this reagent, seeking out suppliers who guarantee 99% purity and offer competitive pricing is a strategic move. Procuring EMCS from established manufacturers ensures that your chemical synthesis projects benefit from a product designed for optimal reactivity and stability.