Sulfo-SMCC is a heterobifunctional amine to sulfhydryl crosslinking reagent.Sulfo-SMCC contains one sulfo-NHS ester group and a maleimide reactive group at each end of a cyclohexyl spacer.The NHS ester groups readily react towards primary amines at pH 7-9.The maleimide group reacts towards sulfhydryl (or thiol) groups at pH 6.5-7.5.The sulfo moieties provide excellent water solubility and allows Sulfo-SMCC to be used in acqueous buffer solutions without the need of organic solvents that may cause protein perturbation.