Interaction of hemoglobin with salts: Effects on the functional properties of human hemoglobin

Oxygen isotherms of human hemoglobin measured in distilled water and in solutions of different inorganic salts in the concentration range from below 10^?3 m to above 1·5 m at neutral pH indicate that the oxygen affinity decreases with increasing salt concentration in the lower range of ionic strength; above the physiological range, there is in most cases a further decrease in oxygen affinity, but this varies with the nature of the salt and, in some instances, the affinity goes through a maximum.The effect of cations, which is opposite to that of anions, operates primarily in the higher concentration range; i.e. above 0·1 m. This effect is especially large for Li⁺, Ca²⁺ and Mg²⁺.The alkaline Bohr effect depends strongly on anion concentration, being displaced towards higher pH values and being reduced in magnitude as chloride concentration is increased. On the other hand, the acid Bohr effect, observed below pH 6, appears to be independent of chloride concentration from 6 × 10^?2 m to 2 m.The overall heat of oxygenation has been determined for the isoionic protein as well as at different concentrations of chloride and phosphate. The average intrinsic heat of reaction of hemoglobin with oxygen in solution is found to be ?14·6 kcal/mol of O₂.