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The role of surface histidyl residues in the alpha-chain to the Bohr effect of human normal adult hemoglobin was established. Proton nuclear magnetic resonance spectra of constructed recombinant mutant hemoglobins (rHb) and hemoglobin A revealed that heterotropic interactions depend on the arrangement and interactions of H+ binding sites in the Hb. The Bohr effect can be diminished or can be increased by the presence of histidyl residues.

A compensatory mutation in a naturally occurring abnormal human hemoglobin (Hb) mutant, Hb Kempsey (Asp-beta99 yield Asn) is generated using molecular dynamics simulations of Escherichia coli expression plasmid pHE2. O2 binding properties of the recombinant double mutant Hb, Hb(Asp-beta99 yield Asn and Tyr-alpha42 yield Asp) are determined. The functional defect of Hb Kempsey, resulting from (Asp-beta99 yield Asn) substitution, is compensated by the (Tyr-alpha42 yield Asp) replacement. These compensatory amino acid replacements restore the allosteric properties of Hbs.