The carbon dioxide affinity of various human hemoglobins.

We have investigated the effect of molecular carbon dioxide, i.e., formation of carbamino compounds on (a) the partial pressure of oxygen at 50% saturation (&,,) of hemoglobin and (b) the Bohr effect when expressed as A log &o/ApH in the following human hemoglobins: Arr (a&), Frr (azrz), AI, (w&~'~), and FIacetY1 (czz-r2acety1).Some experiments of this kind were also carried out with hemoglobin Hope ((Y&~~ G1y+Asp) and the mixed state hemoglobins (o~irrCN/3")~ and (cr"P"'CN)z.Hemoglobin AI, and FIacetY1 have blocked NHt-termini of p and y subunits, respectively, whereas in hemoglobin Hope a salt bridge exists between /3iz6 *W 'O"-and the NHz-terminal a-amino group of the fl subunits.Consequently, only the a-amino groups of the a! subunits are free to react with COz in these three hemoglobins.