Reagents and methods are provided for crosslinking and immobilizing biomolecules, drugs and synthetic polymers. The reagents of forumula VII or VIII possess (i) a thiol or amino reactive group and (ii) a oxyamino moiety. Conjugates and immobilized biomolecules are also provided. €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒB-R-ONH 2 €¢HX€ƒ€ƒ€ƒ€ƒ€ƒVII or €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒB-R-ON=C(R 1 R 2 )€ƒ€ƒ€ƒ€ƒ€ƒVIII