Modification of hemoglobin upon covalent coupling to dextran: enhanced stability against acid denaturation and reduced affinity for haptoglobin.

Alkylation of human hemoglobin by bromoacetylaminoethylamino-substituted dextran gave rise to a covalent dextran-hemoglobin complex with enhanced stability against acid denaturation, and reduced affinity for binding to haptoglobin, compared with free hemoglobin. These effects increased with increasing size of the dextran moiety and were not elicited by either free dextran or alkylation of hemoglobin by iodoacetamide. These observations are consistent with an inhibition by covalently attached dextran of the binding of beta-subunit of hemoglobin to haptoglobin.