Sulfo EMCS

Sulfo EMCS ([N-(E-maleimidocaproyloxy)-sulfo succinimide ester), a water-soluble analog of EMCS is a heterobifunctional cross-linker, containing N-hydroxysuccinimide (NHS) ester and maleimide groups that allow covalent conjugation of amine- and sulfhydryl- containing molecules. NHS esters react with primary amines at pH 7-9 to form amide bonds, while maleimides react with sulfhydryl groups at pH 6.5-7.5 to form stable thioether bonds. In aqueous solutions, hydrolytic degradation of the NHS ester is a competing reaction whose rate increases with pH. The maleimide group is more stable than the NHS-ester group but will slowly hydrolyze and also lose its reaction specificity for sulfhydryls at pH values > 7.5. For these reasons, conjugation experiments involving these cross-linkers are usually performed at a pH range of 7.2-7.5, with the NHS-ester (amine-targeted) reaction being accomplished before or simultaneously with the maleimide (sulfhydryl-targeted) reaction.

Features and Benefits

• Reactive groups: sulfo-NHS ester and maleimide
• Reactive towards: amino and sulfhydryl groups
• Sulfo-NHS ester end couples with primary amines at pH 7-9 to form stable amide bonds
• Maleimide reacts with -SH groups at pH 6.5-7.5, forming stable thioether linkages
• Non-cleavable
• Water-soluble (compare to EMCS)
• Aliphatic spacer offers low potential for eliciting an immune response