Effect of modification on physico-chemical and biological properties of haptoglobin. Reaction with N-bromusuccinimide and 2-hydroxy-5-nitrobenzyl bromide.

N-Bromosuccinimide and 2-hydroxy-5-nitrobenzyl bromide have been used for modification of tryptophan residues in human haptoglobin (Hp) type 2-1. Modification of three exposed tryptophan residues reduced considerably both the Hp-haemoglobin interaction and binding of the antibody against the native protein. Modification of the remaining 7-8 tryptophan residues resulted in a complete loss of those properties. Antisera directed against Hp with the modified tryptophan residues appeared to be highly specific in immunological reactions.