RESUMO
AIM: To observe hemichrome formation in human haemoglobin A under various buffer conditions. METHOD: Hemichrome formation of human oxyhaemoglobin A (HbO2) was studied spectrophotometrically in 0.1 m buffer at various temperatures and pH values. RESULTS: Following autoxidation in ferrous HbO2, it was evident that formation of hemichrome, which tends to precipitate, occurred at various stages during the course of the autoxidation reaction namely at initial, intermediate or final stages, depending on temperature and pH of the solution. By varying temperature of the solution from 35 to 55 degrees C and pH from 4.5 to 10.5, it is shown here that HbO2 exhibits high susceptibility for hemichrome formation and its occurrence is a function of pH, temperature and progress of autoxidation of HbO2. Unlike HbO2 and its separated haemoglobin chains, monomeric bovine heart myoglobin (MbO2) did not easily form hemichrome. CONCLUSION: These findings provide a clue on the crucial role of haemoglobin molecule for senescent cell recognition or homeostasis in the blood circulation.