EMCH (N-(epsilon-maleimidocaproic acid) hydrazide, trifluoroacetic acid salt)

3,3′-N-[ε-Maleimidocaproic acid] hydrazide, trifluoroacetic acid salt (EMCH) is a water-soluble, heterobifunctional, membrane permeable crosslinker. It contains a sulfhydryl reactive maleimide group and carbonyl reactive hydrazide group at each end of a 6-carbon spacer arm. Maleimides react with sulfhydryls at pH 6.5-7.5 to form stable thiol ether bonds, along with release of the maleimide leaving group. Proteins with cysteine residues not involved in disulfide bond formation are targets for maleimide reactive groups. Carbonyl groups, whilst not found naturally on proteins can be formed by ring sugar reduction to form aldehydes which react with hydrazides at pH5.5-7.5.