A heterobifunctional cross-linking reagent incorporating an extended spacer with amine and sulfhydryl reactivity. Typically, coupled initially to molecules containing primary amines by amide bonds buffered at pH 7.5 (6.5-8.5) The second coupling is specific for molecules containing free sulfhydryl by thioether linkage buffered at pH 6.8 (6.5-7.0). Useful for preparation of enzyme immunoconjμgates and hapten carrier molecule conjμgates. Contains 9 atom linker. An extended aliphatic spacer stabilizes the maleimide prior to coupling compared to aromatic spacers.A heterobifunctional cross-linking reagent with amine and sulfhydryl reactivity A heterobifunctional cross-linking reagent incorporating an extended spacer with amine and sulfhydryl reactivity. Typically, coupled initially to molecules containing primary amines by amide bonds buffered at pH 7.5 (6.5-8.5) The second coupling is specific for molecules containing free sulfhydryl by thioether linkage buffered at pH 6.8 (6.5-7.0). Useful for preparation of enzyme immunoconjugates and hapten carrier molecule conjugates. Contains 9 atom linker. An extended aliphatic spacer stabilizes the maleimide prior to coupling compared to aromatic spacers. A heterobifunctional cross-linking reagent with amine and sulfhydryl reactivity