Influence of Molecular Structure on O2-Binding Properties and Blood Circulation of Hemoglobin‒Albumin Clusters

A hemoglobin wrapped covalently by three human serum albumins, a Hb-HSA3 cluster, is an artificial O2-carrier with the potential to function as a red blood cell substitute. This paper describes the synthesis and O2-binding properties of new hemoglobin‒albumin clusters (i) bearing four HSA units at the periphery (Hb-HSA4, large-size variant) and (ii) containing an intramolecularly crosslinked Hb in the center (XLHb-HSA3, high O2-affinity variant). Dynamic light scattering measurements revealed that the Hb-HSA4 diameter is greater than that of either Hb-HSA3 or XLHb-HSA3. The XLHb-HSA3 showed moderately high O2-affinity compared to the others because of the chemical linkage between the Cys-93(β) residues in Hb. Furthermore, the blood circulation behavior of 125I-labeled clusters was investigated by assay of blood retention and tissue distribution after intravenous administration into anesthetized rats. The XLHb-HSA3 was metabolized faster than Hb-HSA3 and Hb-HSA4. Results suggest that the molecular structure of the protein cluster is a factor that can influence in vivo circulation behavior.由三分子人血清白蛋白（human serum albumin, HSA）共价包裹的血红蛋白（hemoglobin, Hb）所形成的Hb-HSA3簇，是一类人工氧载体，具备作为红细胞代用品的应用潜力。本文报道了两类新型血红蛋白-白蛋白簇的合成方法与氧结合特性：其一为外围带有四分子人血清白蛋白的大尺寸变体Hb-HSA4；其二为中心包含分子内交联血红蛋白的高氧亲和力变体XLHb-HSA3。动态光散射（dynamic light scattering, DLS）检测结果显示，Hb-HSA4的粒径大于Hb-HSA3与XLHb-HSA3。由于血红蛋白β亚基93位半胱氨酸（Cys-93(β)）残基间形成了化学交联，XLHb-HSA3相较于其余两种簇表现出适中偏高的氧亲和力。此外，本研究通过对麻醉大鼠静脉给药后检测血液滞留率与组织分布，探究了碘-125（125I）标记的上述蛋白簇的体内血液循环行为。结果表明，XLHb-HSA3的代谢速率快于Hb-HSA3与Hb-HSA4。研究结果提示，蛋白簇的分子结构是影响其体内循环行为的关键因素之一。