The oxygen affinity of concentrated human hemoglobin solutions and human blood

The log P50 of normal human blood at 37 degrees C, PCO2 = 0, 21, 42, AND 57 MM Hg in the absence and in the presence of 2,3-DPG and ATP, has been determined in the pH range 7.0 to 7.6. Similar data have been obtained for human hemoglobin isotonic solutions at different protein concentrations in the presence of various amounts of each of the cofactors which are known to affect hemoglobin oxygen affinity in blood. It has been found that the addition of KC1, organic phosphates, magnesium ions, and CO2 confers to a 32% human hemoglobin solution the same oxygen affinity (over the entire physiological pH range) of whole blood. Thus there is no room for significant effects caused by some other unidentified molecules or ions.