Structure-Redox Response Correlation in a Few Select Heme Systems Using X-ray Absorption Spectroelectrochemistry.

Area of Science:

• Biochemistry and Biophysics
• Bioinorganic Chemistry
• Spectroscopy and Electrochemistry

Background:

• Heme biomolecules are essential for critical life functions, including oxygen and electron transport.
• The heme's active site, particularly the iron metal center, dictates biomolecule functionality.
• During oxygen binding/unbinding in hemoglobin, iron's oxidation state remains +II, while spin states change.

Purpose of the Study:

• To comprehensively study the redox response of heme biomolecules based on their active site's electronic structure.
• To identify electronic structural parameters correlating with redox reversibility in heme systems.
• To trace changes in the redox state of heme systems by monitoring these parameters.

Main Methods:

• In operando study of the local electronic structure of heme in selective molecular systems.
• Utilized synchrotron X-ray absorption spectroscopy (Fe K-edge) and cyclic voltammetry.
• Correlated electronic structural parameters with redox reversibility.

Main Results:

• Identified key electronic structural parameters influencing the redox response of heme biomolecules.
• Demonstrated that axial coordination and the spin state of the iron center are intimately linked to redox behavior.
• Showcased how evolution in these parameters can track overall redox state changes.

Conclusions:

• Axial coordination and iron spin state are critical determinants of heme redox response.
• These parameters provide valuable insights into the functional mechanisms of heme-based biomolecules.
• The study establishes a method to monitor redox state changes through electronic structure analysis.