WATER ADSORPTION AND DIELECTRIC PROPERTIES OF LYOPHILIZED HEMOGLOBIN

The adsorption of water on lyophilized horse hemoglobin and the dielectric properties have been investigated simultaneously up to a hydration degree of h = 0.352 g of H2O/g of protein. Critical hydration values of hc = 0.12 and 0.165 g of H2O/g of protein were found. The first BET monolayer was calculated to be complete at hm = 0.0576 g of H2O/g of protein. This quantity appears to be correlated to the hydration value h = 0.0695 g of H2O/g of protein of monomolecular adsorption on polar sites. From the ratio of these two quantities, the percentage of polar groups of the hemoglobin molecule available for hydration is estimated to be 0.83%. The dielectric dispersion of lyophilized hemoglobin is compared with that of dilute aqueous hemoglobin solution. Possible polarization mechanisms are discussed.