PEG and DBBF Modified Porcine Hemoglobin and Their Oxygen-carrying Capacity

HONG Min, CAI Jin¹, MENG Wen-Fang², LI Shi-Yun, YUAN Zhong-Yi^*
( Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, the Chinese Academy of Sciences, Shanghai 200031, China; ¹College of Material and Chemical Engineering,Zhejiang University, Hangzhou 310027, China; ²School of Medicine, Zhejiang University, Hangzhou 310016, China )

Abstract    Modifications of proteins with polyethylene glycol (PEG) have been proven to enlarge molecule size of proteins, to prolong their retention time in the circulation as well as blunt immune or allergic reactions. Hemoglobin cross-linked with small molecular modifiers turns out to be more stable and to have better oxygen carrying capacity. In the present study, four derivatives of PEG with different activation groups, and several PEGs with different molecular weights were covalently bound to porcine hemoglobin (pHb). PEG-pHbs exhibited a variety of differences in their properties depending on the molecular weights of the used PEGs, the amounts of bound PEGs and the presence or absence of allosteric cofactors. The optimal modification conditions for bis (3, 5-dibromosalicyl) fumarate (DBBF) as well as the physical features and oxygen carrying capacity of DBBF-modified pHb were evaluated. Furthermore, both PEG and DBBF were used simultaneously to modify pHb. The results indicate that the pHbs modified with PEG and DBBF have more stable tetrameric conformations with a molecular weight of 107 kD. Their oxygen half-saturation pressure (P₅₀) is around 3.33 kPa which approximates the physiological P₅₀ of human red blood cells.
Key words    porcine hemoglobin; PEG; DBBF; modification; blood substitute

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