Fe-O2 bonding and oxyheme structure in myoglobin.

Area of Science:

• Biochemistry
• Biophysics
• Spectroscopy

Background:

• Oxymyoglobin structure and function are crucial in oxygen transport.
• Understanding the coordination geometry of the heme-O2 bond is key to protein function.

Purpose of the Study:

• To probe the orbital structure and coordination geometry of oxymyoglobin using polarized electronic absorption spectroscopy.
• To investigate differences in oxyheme structure between sperm whale and Aplysia myoglobin.

Main Methods:

• Polarized electronic absorption spectroscopy of oxymyoglobin in single crystals.
• Analysis of charge-transfer states involving iron and dioxygen ligand orbitals.

Main Results:

• Sperm whale oxymyoglobin exhibits a bent (formula: see text) oxheme coordination geometry.
• This geometry is associated with spin-paired electronic configurations of iron and the dioxygen ligand.
• Aplysia myoglobin shows a distinguishably different oxyheme structure.

Conclusions:

• The bent coordination geometry is characteristic of sperm whale oxymyoglobin.
• The protein environment can significantly alter the Fe-O2 bonding geometry in heme proteins.
• Electronic absorption spectroscopy is a powerful tool for determining oxyheme structure.