Various chemical modifications of hemoglobin (Hb) including PEGylation have been investigated to produce red blood cell substitutes. Some of those modifications are designed on the premise that the α₂β₂ tetrameric structure of Hb is fundamentally stable and that it rarely dissociates into two αβ dimers in a physiological condition. However, in the present work using the “clipping” method we detected and quantitatively analyzed the considerable degree of exchange reaction of αβ subunits between β93Cys-bis-PEGylated and native Hbs through dissociation into αβ dimers and restructuring to α₂β₂ tetramer in a physiological condition. The equilibrium constant (K_eq) of subunit exchange reactions increased from 0.82 to 2.86 with increasing molecular weight of PEG from 2 to 40 kDa, indicating that longer PEG chains enhanced such exchange reaction. The results suggest that the exchange might occur for other modified Hbs even at a practically high concentration for use as a red blood cell substitute.

中文翻译：

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聚乙二醇化和本地血红蛋白（α之间二聚体αβ亚基外汇分析₂ β ₂四聚体）在通过分子内的均衡状态ββ交联

已经研究了血红蛋白（Hb）的各种化学修饰，包括PEG化，以产生红细胞替代物。一些这些修改都为前提设计，即α ₂ β ₂血红蛋白四聚体结构基本上是稳定的，它很少发生解离成两个αβ二聚体中的生理状况。然而，在使用我们检测和定量的“限幅”的方法目前的工作分析的相当程度的β93Cys双PEG化的和本地HBS之间αβ亚单位的交换反应，通过离解成αβ二聚体和重组到α ₂ β ₂四聚体在一个生理状况。平衡常数（K _eq）的亚单位交换反应随着PEG的分子量从2 kDa增加到40 kDa而从0.82增加到2.86，表明更长的PEG链增强了这种交换反应。结果表明，即使以高浓度用作红细胞替代品，其他修饰的血红蛋白也可能发生交换。