Conjugating Hemoglobin and Albumin by Strain-Promoted Azide-Alkyne Cycloaddition.

A one-to-one conjugate of cross-linked human hemoglobin and human serum albumin results from a strain-promoted azide-alkyne cycloaddition (SPAAC) of the modified proteins. Additions of a strained alkyne-substituted maleimide to the Cys-34 thiol of human serum albumin and an azide-containing cross-link between the amino groups of each b-unit at Lys-82 of human hemoglobin provide sites for coupling by the SPAAC process. The coupled hemoglobin-albumin conjugate can be readily purified from the unreacted hemoglobin. The oxygen binding properties of this two-protein conjugate demonstrate an oxygen affinity and binding cooperativity suitable as an acellular oxygen carrier.