3-Maleimidopropionic acid N-hydroxysuccinimide ester is a non-cleavable and membrane permeable crosslinker。 It contains an amine-reactive succinimidyl ester (SE) and a sulfhydryl-reactive maleimide group。 NHS esters react with primary amines at pH 7-9 to form stable amide bonds。 Maleimides react with sulfhydryl groups at pH 6。5-7。5 to form stable thioether bonds。 The SE group of 3-maleimidopropionic acid N-hydroxysuccinimide ester is reacted with lysine residues on the carrier protein, converting them to reactive maleimides。 3-Maleimidopropionic acid N-hydroxysuccinimide ester is a reagent that is widely used for generating stable maleimide-activated carrier proteins that can spontaneously react with sulfhydryls。 Alternatively these relatively stable maleimide-activated intermediates may be lyophilized and stored for later conjugation to a hapten。