title: Aggregation of hemoglobin S modified by bifunctional imidoesters.
abstract: Sickle hemoglobin (Hb S) was cross-linked by two types of bifunctional imidoesters, dimethyladipimidate (DMA) and dimethyl-3,3'-dithiobispropionimidate (DTBP). These modified hemoglobins were separated into monomer, dimer and polymer fractions by gel filtration. All of these modified hemoglobins showed extremely left-shifted oxygen equilibrium curves with no cooperativity. The stabilities of these hemoglobins were also decreased. The solubilities of these modified hemoglobins in high-phosphate buffers were lower than those of native Hb S. Studies on the kinetics of the aggregation of these modified hemoglobins showed that intracross-linked Hb S with DMA and DTBP (DMA- and DTBP-modified monomeric Hb S) still retained the capability of aggregation with a delay time, while intercross-linked Hb S with DMA and DTBP (DMA- and DTBP-modified oligomeric Hb S) aggregated without a delay time. When the kinetics of aggregation was measured for mixtures of modified and native deoxy-Hb S, DMA-modified monomeric deoxy-Hb S shortened the delay time prior to aggregation of native deoxy-Hb S. The other modified deoxy-Hb S did not affect the delay time, suggesting that these modified oligomeric hemoglobins neither participate in the formation of nuclei nor copolymerize with native deoxy-Hb S.
mesh_terms: D003432:Cross-Linking Reagents; D006441:Hemoglobin A; D006451:Hemoglobin, Sickle; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D010100:Oxygen / Q000097:blood; D011485:Protein Binding; D012995:Solubility
chemical_list: D003432:Cross-Linking Reagents; D006451:Hemoglobin, Sickle; D006441:Hemoglobin A; D010100:Oxygen