From Transient to Metastable: Generation, Characterization, and Biomimetic Reactivity Studies of Well-Defined Heme...

Area of Science:

• Bioinorganic Chemistry
• Chemical Biology
• Spectroscopy

Background:

• Peroxynitrite (PN) plays a role in various diseases, but its reaction mechanisms involving heme proteins are poorly understood.
• Heme-PN adducts are transient and difficult to characterize, creating a knowledge gap in their biological relevance.

Purpose of the Study:

• To generate and characterize novel heme-PN adducts.
• To investigate the reactivity and decomposition pathways of these adducts.
• To provide insights into the biological roles of heme-PN chemistry.

Main Methods:

• Synthesis of tetraarylporphyrin-based heme-PN adducts using heme peroxo adducts and nitrosonium cations.
• Characterization using UV-vis, NMR, EPR, resonance Raman spectroscopy, DFT calculations, and mass spectrometry.
• Kinetic studies on heme-PN-mediated phenol nitration and reactivity with organic substrates.

Main Results:

• Three metastable heme-PN adducts were successfully generated and characterized.
• Spectroscopic and theoretical data confirmed O-O bond homolysis as the primary decay pathway, yielding ^•NO₂ radicals.
• Demonstrated reactivity of heme-PN with various organic substrates, paralleling proposed biological functions.

Conclusions:

• Stable heme-PN adducts can be generated and characterized, offering a window into their chemistry.
• The O-O bond homolysis mechanism provides a key insight into heme-PN reactivity.
• This study advances the understanding of heme-PN formation and reactivity in biological contexts.