Department of Chemistry , Nara Medical University , 840 Shijo-cho , Kashihara , 634-8521 , Japan.
Biomacromolecules. 2018 Aug 13;19(8):3412-3420. doi: 10.1021/acs.biomac.8b00728. Epub 2018 Jul 12.
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 αβ 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 αβ tetramer in a physiological condition. The equilibrium constant ( K) 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.
已经研究了血红蛋白（Hb）的各种化学修饰，包括 PEG 化，以生产红细胞代用品。其中一些修饰是基于这样的前提设计的，即 Hb 的 αβ 四聚体结构从根本上是稳定的，并且在生理条件下很少解离成两个 αβ 二聚体。然而，在本工作中，我们使用“剪接”方法检测并定量分析了β93Cys-双-PEG 化和天然 Hbs 之间通过解离成 αβ 二聚体和在生理条件下重组为 αβ 四聚体的 αβ 亚基之间相当程度的交换反应。随着 PEG 分子量从 2 到 40 kDa 的增加，亚基交换反应的平衡常数（K）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，即使在用作红细胞代用品的实际高浓度下，其他修饰的 Hbs 也可能发生这种交换。
