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Hemoglobin-oxygen equilibrium at different hemoglobin and 2,3-diphosphoglycerate concentrations
Physiological Chemistry and Physics
|January 1, 1977
Summary
High hemoglobin (Hb) concentrations and organic phosphates like 2,3-DPG alter Hb
Area of Science:
- Biochemistry
- Physiology
Background:
- Hemoglobin's oxygen binding affinity is crucial for oxygen transport.
- 2,3-Diphosphoglycerate (2,3-DPG) is a key allosteric effector of hemoglobin (Hb).
Purpose of the Study:
- To investigate the impact of varying hemoglobin concentrations and 2,3-DPG/Hb ratios on Hb-oxygen equilibrium.
- To explore the influence of intermolecular interactions on Hb-oxygen affinity.
Main Methods:
- Determination of hemoglobin-oxygen equilibrium curves under controlled conditions (pH, ionic strength, temperature).
- Experiments involved varying Hb concentrations, 2,3-DPG/Hb molar ratios, and using hemolysates.
- Analysis of half-saturation pressure (P1/2) as a measure of oxygen affinity.
Main Results:
- The shape of the Hb-oxygen equilibrium curve remained consistent across all conditions.
- P1/2 was independent of Hb concentration in 2,3-DPG-free solutions but increased linearly with Hb concentration when 2,3-DPG was present at a constant ratio.
- Increasing 2,3-DPG/Hb ratio significantly affected P1/2 at high Hb concentrations, unlike in diluted solutions.
Conclusions:
- Observed changes in Hb-oxygen affinity at high Hb concentrations with 2,3-DPG cannot be explained by current theories.
- Intermolecular interactions, potentially mediated by organic phosphates, are suggested as the cause of altered Hb affinity.