STRUCTURE OF HAEMOGLOBIN. AN X-RAY EXAMINATION OF REDUCED HORSE HAEMOGLOBIN

Dielectric dispersion in aqueous solutions of oxyhaemoglobin and carboxyhaemoglobin

The relative permittivity and conductivity of aqueous solutions of oxyhaemoglobin and carboxyhaemoglobin were measured over the frequency range 150kHz-100MHz. To minimize errors of measurement the investigations were carried out with three different samples of each type of haemoglobin, independent apparatus being used in two different laboratories. The dielectric increment and relaxation time were calculated at each of several temperatures from the results. These lead to a dipole moment of 400 Debyes and an activation enthalpy of 17.6+/-1.4kJ.mol(-1), both of which were found to be independent of temperature to within experimental error over the range 3-35 degrees C. The value of the dipole moment shows that the distribution of charge throughout the haemoglobin molecule is nearly symmetrical with respect to the centre of charge. The magnitude of the activation enthalpy is similar to that of the viscosity of water, in accord with the common observation that dielectric relaxation and viscosity are related phenomena. No significant differences are found between the dielectric parameters of oxyhaemoglobin and carboxyhaemoglobin. Combining the results with those obtained from X-ray diffraction of the solid a hydration value of 0.45g of water/g of protein is suggested, subject to the limitations of the model used. Finally, the results indicate the presence of a subsidiary dispersion, which could be attributed to the above quantity of bound water having a static permittivity of about 100 and a relaxation frequency in the region 100-200MHz.

Conformational changes in sperm-whale metmyoglobin due to combination with antibodies to apomyoglobin

1. No ferrihaem was detected in the precipitate formed by metmyoglobin with an antiserum to apomyoglobin and the extinction at 410mmu of metmyoglobin, due to ferrihaem, was decreased by the univalent fragments of apomyoglobin antibodies. It was concluded that the combination of apomyoglobin antibodies with metmyoglobin caused the release of ferrihaem. As the removal of ferrihaem from metmyoglobin is accompanied by a conformational change, it was concluded that the conformation of metmyoglobin was altered by the apomyoglobin antibodies. 2. Antisera to metmyoglobin were divided into two groups; antisera of the first group revealed differences between the immunological reactivities of metmyoglobin and apomyoglobin, whereas no differences were detected with antisera of the second group. 3. Metmyoglobin was only partially re-formed by adding haematin to the precipitate produced by apomyoglobin with an antiserum of the first group, whereas complete re-formation of metmyoglobin was achieved in the presence of antisera of the second group. No metmyoglobin was formed on the addition of haematin to the precipitates produced by either metmyoglobin or apomyoglobin with the anti-apomyoglobin serum. 4. Immune precipitates formed by antisera to metmyoglobin dissociated at pH1.8, whereas those formed by the anti-apomyoglobin serum did not dissociate. 5. These results suggest that apomyoglobin possessed different conformations when combined with metmyoglobin antibodies and apomyoglobin antibodies.