Solution 1 H NMR study of the electronic structure and magnetic properties of high-spin ferrous or deoxy myoglobins
Solution 1D and 2D NMR, together with limited isotope labeling, have led to the assignment of the heme, axial His, and numerous heme contact residues in sperm whale, horse, and human deoxy myoglobin. The paramagnetic relativity leads to increased line widths and shorter T1s with little compensation...
Published in: | Journal of the American Chemical Society |
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1998
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ftlouisianastuir:oai:digitalcommons.lsu.edu:chemistry_pubs-2702 2023-06-11T04:17:07+02:00 Solution 1 H NMR study of the electronic structure and magnetic properties of high-spin ferrous or deoxy myoglobins Bougault, Catherine M. Dou, Yi Ikeda-Saito, Masao Langry, Kevin C. Smith, Kevin M. La Mar, Gerd N. 1998-03-11T08:00:00Z https://digitalcommons.lsu.edu/chemistry_pubs/1701 https://doi.org/10.1021/ja973197c unknown LSU Digital Commons https://digitalcommons.lsu.edu/chemistry_pubs/1701 doi:10.1021/ja973197c Faculty Publications text 1998 ftlouisianastuir https://doi.org/10.1021/ja973197c 2023-05-28T18:15:16Z Solution 1D and 2D NMR, together with limited isotope labeling, have led to the assignment of the heme, axial His, and numerous heme contact residues in sperm whale, horse, and human deoxy myoglobin. The paramagnetic relativity leads to increased line widths and shorter T1s with little compensation in increased dispersion due to dipolar shifts. Hence only limited, but crucial F helix standard backbone sequence specific assignment could be made for home cavity residues. Numerous other residues with significant dipolar shifts could be assigned from the characteristic scalar connectivities and dipolar contacts to the home predicted by the crystal structure. It is concluded that the complete and unambiguous assignment of the heme pyrrole substituents signals is not attainable by 2D NMR alone without either partial deuterium labeling of the heme or parallel assignment of key residues in dipolar contact with the heme; hence the present study revises some earlier assignments. The resulting dipolar shifts for nonligated residues, together with the crystal coordinates of deoxy myoglobin, were used to determine the orientation relative to the heme and the anisotropy of the paramagnetic susceptibility tensor. The significant anisotropy, |Δχ| ~ 1 x 10-9 m3/mol, however, is shown to result in dipolar shift with reciprocal square, rather than just reciprocal, absolute temperature dependence, which is indicative of large zero field splitting rather than g-tensor anisotropy. The appropriate equation for a 5B2 ground state allows an estimate of the zero- field splitting, D ~-10 cm-1, which is in good agreement with earlier results. The present NMR data favor a spin-only magnetic moment with S = 2 and D ~-10 cm-1 over a ground state with S < 2 and significant orbital contribution (Hendrich and Debrunner, 1989). Text Sperm whale LSU Digital Commons (Louisiana State University) Journal of the American Chemical Society 120 9 2113 2123 |
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LSU Digital Commons (Louisiana State University) |
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Solution 1D and 2D NMR, together with limited isotope labeling, have led to the assignment of the heme, axial His, and numerous heme contact residues in sperm whale, horse, and human deoxy myoglobin. The paramagnetic relativity leads to increased line widths and shorter T1s with little compensation in increased dispersion due to dipolar shifts. Hence only limited, but crucial F helix standard backbone sequence specific assignment could be made for home cavity residues. Numerous other residues with significant dipolar shifts could be assigned from the characteristic scalar connectivities and dipolar contacts to the home predicted by the crystal structure. It is concluded that the complete and unambiguous assignment of the heme pyrrole substituents signals is not attainable by 2D NMR alone without either partial deuterium labeling of the heme or parallel assignment of key residues in dipolar contact with the heme; hence the present study revises some earlier assignments. The resulting dipolar shifts for nonligated residues, together with the crystal coordinates of deoxy myoglobin, were used to determine the orientation relative to the heme and the anisotropy of the paramagnetic susceptibility tensor. The significant anisotropy, |Δχ| ~ 1 x 10-9 m3/mol, however, is shown to result in dipolar shift with reciprocal square, rather than just reciprocal, absolute temperature dependence, which is indicative of large zero field splitting rather than g-tensor anisotropy. The appropriate equation for a 5B2 ground state allows an estimate of the zero- field splitting, D ~-10 cm-1, which is in good agreement with earlier results. The present NMR data favor a spin-only magnetic moment with S = 2 and D ~-10 cm-1 over a ground state with S < 2 and significant orbital contribution (Hendrich and Debrunner, 1989). |
format |
Text |
author |
Bougault, Catherine M. Dou, Yi Ikeda-Saito, Masao Langry, Kevin C. Smith, Kevin M. La Mar, Gerd N. |
spellingShingle |
Bougault, Catherine M. Dou, Yi Ikeda-Saito, Masao Langry, Kevin C. Smith, Kevin M. La Mar, Gerd N. Solution 1 H NMR study of the electronic structure and magnetic properties of high-spin ferrous or deoxy myoglobins |
author_facet |
Bougault, Catherine M. Dou, Yi Ikeda-Saito, Masao Langry, Kevin C. Smith, Kevin M. La Mar, Gerd N. |
author_sort |
Bougault, Catherine M. |
title |
Solution 1 H NMR study of the electronic structure and magnetic properties of high-spin ferrous or deoxy myoglobins |
title_short |
Solution 1 H NMR study of the electronic structure and magnetic properties of high-spin ferrous or deoxy myoglobins |
title_full |
Solution 1 H NMR study of the electronic structure and magnetic properties of high-spin ferrous or deoxy myoglobins |
title_fullStr |
Solution 1 H NMR study of the electronic structure and magnetic properties of high-spin ferrous or deoxy myoglobins |
title_full_unstemmed |
Solution 1 H NMR study of the electronic structure and magnetic properties of high-spin ferrous or deoxy myoglobins |
title_sort |
solution 1 h nmr study of the electronic structure and magnetic properties of high-spin ferrous or deoxy myoglobins |
publisher |
LSU Digital Commons |
publishDate |
1998 |
url |
https://digitalcommons.lsu.edu/chemistry_pubs/1701 https://doi.org/10.1021/ja973197c |
genre |
Sperm whale |
genre_facet |
Sperm whale |
op_source |
Faculty Publications |
op_relation |
https://digitalcommons.lsu.edu/chemistry_pubs/1701 doi:10.1021/ja973197c |
op_doi |
https://doi.org/10.1021/ja973197c |
container_title |
Journal of the American Chemical Society |
container_volume |
120 |
container_issue |
9 |
container_start_page |
2113 |
op_container_end_page |
2123 |
_version_ |
1768375970895495168 |