Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT

ABSTRACT - Internet Electron. J. Mol. Des. May 2005, Volume 4, Number 5, 309-315

Hypothesis of Hemoprotein Sensor Confirmed by ab initio Quantum-Chemical Calculations Tatiana A. Romanova, Irina I. Morgulis, Pavel O. Krasnov, and Pavel V. Avramov Internet Electron. J. Mol. Des. 2005, 4, 309-315

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Abstract:
The nature of the chemical bond of iron(II) porphyrin and cobalt(II) porphyrin with ligands is studied by the quantum-chemical Hartree-Fock method using the 6-31G basis set. The addition of oxygen molecule to the MeP and Im-MeP complexes (Me = Fe, Co; Im = imidazole, P = porphyrin) is established to be more favorable than water addition. It has been found that the imidazole bound to Me increases the Me-O₂ and Me-H₂O binding energies for FeP, but decreases ones for CoP. The Co atom is bound with the porphyrin ring more strongly than the Fe atom due to the larger total overlap of the atomic orbitals. The ab initio calculations of the complexes have demonstrated the similar changes in the structures of the geometry of the deoxyform (FeP-H₂O) of iron(II) porphyrin and the oxyform (CoP-O₂) of cobalt(II) porphyrin. This is an argument in favor of the hypothesis of hemoprotein sensor of partial oxygen tension in tissues.

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