The N-hydroxysuccinimide ester 15 resin is activated immunoaffinity supports that offer rapid, high efficiency coupling for all ligands with a primary amino group, including proteins throughout the entire range of pIs and low molecular weight compounds such as peptides. The resin supports are N-hydroxysuccinimide esters of a derivatized crosslinked agarose gel bead support, and both couple to ligands spontaneously in aqueous or non-aqueous solution.