Influence of Molecular Structure on O(2)-Binding Properties and Blood Circulation of Hemoglobin‒Albumin Clusters

A hemoglobin wrapped covalently by three human serum albumins, a Hb-HSA(3) cluster, is an artificial O(2)-carrier with the potential to function as a red blood cell substitute. This paper describes the synthesis and O(2)-binding properties of new hemoglobin‒albumin clusters (i) bearing four HSA units at the periphery (Hb-HSA(4), large-size variant) and (ii) containing an intramolecularly crosslinked Hb in the center (XLHb-HSA(3), high O(2)-affinity variant). Dynamic light scattering measurements revealed that the Hb-HSA(4) diameter is greater than that of either Hb-HSA(3) or XLHb-HSA(3). The XLHb-HSA(3) showed moderately high O(2)-affinity compared to the others because of the chemical linkage between the Cys-93(β) residues in Hb. Furthermore, the blood circulation behavior of (125)I-labeled clusters was investigated by assay of blood retention and tissue distribution after intravenous administration into anesthetized rats. The XLHb-HSA(3) was metabolized faster than Hb-HSA(3) and Hb-HSA(4). Results suggest that the molecular structure of the protein cluster is a factor that can influence in vivo circulation behavior.