Hemoglobin-dialdehyde dextran conjugates: Improvement of their oxygen-binding properties with anionic groups |
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Authors: | Franç ois Bonneaux, Edith Dellacherie, Pierre Labrude Claude Vigneron |
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Affiliation: | (1) Faculté des Sciences, Pharmaceutiques et Biologiques, BP 403, 54001 Nancy Cedex, France;(2) Laboratoire de Chimie Physique Macromoléculaire, URA CNRS 494, ENSIC, BP 451, 54001 Nancy Cedex, France |
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Abstract: | We studied the conjugates formed between hemoglobin and sulfated or unsulfated oxidized dextran. It appears that the presence of sulfated groups favors imino bond formation between the protein and the polymer, as the average molecular size of the conjugates is larger in this case. Under neutral conditions, the oxygen-binding properties of the conjugates depend on the presence or absence of oxygen during the coupling reaction. With unsulfated dextran, oxyhemoglobin leads to conjugates with increased oxygen affinity (P50/P50 native hemoglobin 0.5) compared to that of free hemoglobin (P50=4 mm Hg), whereas deoxyhemoglobin leads to conjugates with decreased oxygen affinity (P50/P50 native hemoglobin 3). The use of sulfated dextran reinforces this lowering in oxygen affinity, which indicates that sulfated dextran acts as a permanent macromolecular effector of hemoglobin (P50/P50 native hemoglobin 4). Moreover, it can be assumed that some of the linkages involve the 2,3-diphosphoglycerate binding site, as the strong effector inositol hexaphosphate has only a slight effect on the oxygen-binding properties of the conjugate prepared in the deoxy state (P50/P50 native hemoglobin close to 4.4 and 6, respectively, for unsulfated and sulfated conjugates). Although dextran substituted with benzenehexacarboxylic acid (BHC) leads to a low-oxygen-affinity conjugate when linked to oxyhemoglobin through amide bonds (P50/P50 native hemoglobin 5), oxidized dextran modified with BHC leads, with oxyhemoglobin, to a conjugate whose oxygen affinity is close to that of free hemoglobin (P50/P50 native hemoglobin 1.2). |
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Keywords: | Dialdehyde dextran hemoglobin oxygen carrier sulfated dextran benzenehexacarboxylic acid |
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