6533b832fe1ef96bd129a140

RESEARCH PRODUCT

Active site conformation in the αH87G mutant hemoglobin: An optical absorption and FTIR study

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We have studied the active site conformation in the carbonmonoxy derivative of the αH87G mutant hemoglobin by means of optical absorption and FTIR spectroscopies. A red shift (≈30 cm−1) of the Soret band peak frequency, together with a concomitant red shift (≈2 cm−1) of the bound CO stretching frequency has been observed for the mutant protein. This indicates an altered electrostatic environment of the heme group in the mutated subunits. In view of the FTIR data showing that the bound CO molecule experiences an increased positive electrostatic field, we attribute the observed effects to a closer interaction of the CO ligand with the partially positively charged imidazole side chain of the proximal histidine.