Synthesis and characterization of a polyoxyethylene derivative for the affinity labeling of human hemoglobin

The possibility of preparing a polyoxyethylene derivative containing only one active group per chain, and with a narrow distribution of molecular size, was investigated. The aim of this investigation was to obtain a polymeric derivative of benzenehexacarboxylate (BHC) capable of interacting specifically inside the polyphosphate binding site of human hemoglobin (Hb) and which, after covalent coupling with this protein, could lead to conjugates with well‐defined oxygen‐binding properties. Such conjugates could be of interest in the field of blood substitutes. To minimize the percentage of high‐molecular‐weight products resulting from the fact that, on one hand, commercial monomethoxypolyoxyethylene (MPOE 5000) contained a considerable amount of difunctional and high‐molecular‐weight species, and on the other hand that several reactions were likely to lead to cross‐linked products, fractionation steps and/or chromatographic steps were carried out. The final compound obtained under these conditions (83,5% of BHC‐mono substituted polyoxyethylene, 8,5% of BHC disubstituted and 8% MPOE) was found to interact with the polyphosphate binding site of Hb, as it was capable of lowering its affinity for oxygen. After covalent coupling with deoxy‐Hb under defined conditions, this effect was strengthened, which means that the binding was probably formed with an amine of the Hb polyphosphate binding site.