THE REACTIONS OF HEMOGLOBIN IN VARIOUS MEDIA.

Area of Science:

• Biochemistry and Biophysics
• Molecular Biology
• Physical Chemistry

Background:

• Hemoglobin's interaction with oxygen and carbon monoxide is crucial for its biological function.
• Previous studies on heme proteins suggest diffusion-controlled kinetics in viscous media.
• Understanding these reaction rates is key to elucidating hemoglobin's mechanism of action.

Purpose of the Study:

• To determine the rate constants for oxygen and carbon monoxide association with reduced hemoglobin.
• To measure the rate constant for oxygen dissociation from hemoglobin.
• To investigate the influence of medium properties on these reaction rates.

Main Methods:

• Kinetic studies were performed in various media to measure reaction rates.
• Rate constants were analyzed using established models, such as the Gibson and Roughton framework.
• The independence of rates from diffusion and dielectric constants was assessed.

Main Results:

• The association rates of oxygen and carbon monoxide with reduced hemoglobin were found to be largely independent of diffusion and dielectric constants.
• The dissociation rate of oxygen from hemoglobin also showed independence from these medium properties.
• These findings contrast with diffusion-controlled rates observed in other heme proteins.

Conclusions:

• The measured rates primarily reflect the rate constants for the initial molecular interaction.
• Hemoglobin's reactions with oxygen and carbon monoxide, under these conditions, are not diffusion-limited.
• Reactants can be treated as neutral molecules for the purpose of these specific reactions.