Magnetic resonance of cobalt(II) and iron(III): A Schiff's base and heme proteins
Jiang, Fashun
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Permalink
https://hdl.handle.net/2142/22725
Description
Title
Magnetic resonance of cobalt(II) and iron(III): A Schiff's base and heme proteins
Author(s)
Jiang, Fashun
Issue Date
1991
Doctoral Committee Chair(s)
Belford, R. Linn
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Chemistry, Biochemistry
Chemistry, Inorganic
Chemistry, Physical
Biophysics, General
Language
eng
Abstract
This thesis is comprised of three parts. In the first, the Co-59 nuclear quadrupole coupling constants for cobalt-doped nickelbis(benzoylacetone)ethylenediimine were determined by EPR spectroscopy. The three rotation axes for the three single crystals were not exactly perpendicular to each other, but their exact orientations were known by X-ray diffraction analysis. The program IMOFT, developed for this study, was used to determine the elements of the g matrix, and, consequently, the principal g values and their orientations were found. The principal values of the hyperfine coupling constant A and quadrupole coupling constant P and their orientations were obtained by using the simulation program DXTAL to fit the experimental spectra of the single crystals. The quadrupole coupling constants are QD = $-$4.8 MHz and QE = 0.30 MHz, and they are interpreted by the ground electron configuration--$\rm (dx\sp2-y\sp2)\sp2(dz\sp2)(dxz)\sp2(dyz)\sp1.$
In the second part, proton Fermi contact coupling constants have been measured for low-spin cobalt(II)bis(benzoylacetone)ethylenediimine in $\rm CD\sb2Cl\sb2$ by using variable temperature NMR spectroscopy. The isotropic proton NMR shifts only arise from the Fermi contact interactions in the selected system. From comparison of the experimentally determined distribution of spin density in the compound with the theoretical calculation, it is concluded that the cobalt(II) complex has an electron ground state with the unpaired electron in the dyz orbital, consistent with the result from the first part.
In the third part, electron nuclear double resonancee (ENDOR) spectra have been obtained from iron-linked nitrogens and protons in frozen solution of cytochrome d. Cytochrome d is a high-spin ferric heme protein and exists in the cytochrome d complex located in the inner membrane of E. Coli. After comparing the spectra of cytochrome d with hemin and metmyoglobin, it was found that cytochrome d does not contain an axial nitrogen ligand. By use of computer program NANGSEL, the complete nitrogen hyperfine tensors and quadrupole tensors in the three heme compounds were determined. From average hyperfine coupling constants the unpaired electron densities in nitrogen 2s and 2p valence orbitals were calculated with standard ligand field techniques. The quadrupole constants were also related to electron populations on the nitrogen orbitals.
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