反应体系pH对聚乙二醇牛血红蛋白偶联物性质的影响OACSTPCD

Objective To explore the impact of pH value of the reaction system on the properties of bovine hemoglobin modified with aldehydeated polyethylene glycol(PEG-bHb).Methods PEG-bHb conjugates were synthesized under varying pH conditions(6.0,6.5,7.4 and 8.0)of the reaction system while consistent molar ratios,temperature,and reaction time were maintained.The structural and functional attributes of PEG-bHb were characterized.Results The proportion of methemoglobin decreased with an increase in pH.In a weakly acidic reaction environment,the PEG-bHb was found to be relatively highly modified.At pH 6.5,the average number of PEG chains attached to the bHb surface was 6.86±0.38.Selective PEG modification of the N-terminal α-NH2 groups was more pronounced under weakly acidic conditions.Specifically,at pH 6.5,the modification efficiency of the N-terminal α-NH2 groups of bHb by aldehyde-activated PEG reached 95.4％for the α-chains and 99.3％for the β-chains.The PEG modification influenced the heme region microenvi-ronment of bHb,with minimal structural impact observed at pH 6.5.After modification,the oxygen affinity of PEG-bHb was enhanced,the Hill coefficient was reduced,and there were significant increases in colloid osmotic pressure,viscosity,and particle size,all of which differed markedly from the unmodified bHb group(P＜0.001).Conclusion The synthesis of PEG-bHb under weakly acidic conditions can result in a high degree of selective modification of the N-terminal α-NH2 groups and an overall high degree of modification.