BMPA Modifier (N-ß-Maleimidopropionic acid) can be used as a protein crosslinker or sulfhydryl (-SH) to carboxylic acid (-COOH) modification reagent. As a protein modifier, BMPA is used to modify sulfhydryl groups at pH 6.5-7.5 to terminal carboxyl groups. BMPA protein modification makes -COOH groups for subsequent coupling via EDC crosslinking. As a protein crosslinker, BMPA can be used for the preparation of protein conjugates. The maleimide and carboxyl reactive groups of BMPA crosslinker are reactive toward sulfhydryls and hydrazides/amines, respectively.