C-13 shieldings, O-18 isotope effects on C-13 shieldings, and Fe-57-C-13 spin couplings of the Fe-C-O unit in superstructured hemoprotein models: Comparison with hemoproteins, C-O vibrational frequencies, and X-ray structural data
| dc.contributor.author | Kalodimos, C. G. | en |
| dc.contributor.author | Gerothanassis, I. P. | en |
| dc.contributor.author | Troganis, A. | en |
| dc.contributor.author | Loock, B. | en |
| dc.contributor.author | Momenteau, M. | en |
| dc.date.accessioned | 2015-11-24T16:53:20Z | |
| dc.date.available | 2015-11-24T16:53:20Z | |
| dc.identifier.issn | 0925-2738 | - |
| dc.identifier.uri | https://olympias.lib.uoi.gr/jspui/handle/123456789/10003 | |
| dc.rights | Default Licence | - |
| dc.subject | c-13 shieldings | en |
| dc.subject | hemoproteins | en |
| dc.subject | isotope effects | en |
| dc.subject | model compounds | en |
| dc.subject | free-energy relationships | en |
| dc.subject | carbon-monoxide | en |
| dc.subject | heme-proteins | en |
| dc.subject | resonance raman | en |
| dc.subject | pocket porphyrins | en |
| dc.subject | capped porphyrin | en |
| dc.subject | binding | en |
| dc.subject | ligand | en |
| dc.subject | nmr | en |
| dc.subject | complex | en |
| dc.title | C-13 shieldings, O-18 isotope effects on C-13 shieldings, and Fe-57-C-13 spin couplings of the Fe-C-O unit in superstructured hemoprotein models: Comparison with hemoproteins, C-O vibrational frequencies, and X-ray structural data | en |
| heal.abstract | C-13 NMR spectra of several carbon monoxide (99.7% C-13 and 11.8% O-18 enriched) hemoprotein models with varying polar and steric effects of the distal organic superstructure and constraints of the proximal side are reported. This enables the Fe-57-C-13(O) coupling constants ((1)J(57Fe-13C)), C-13 shieldings (delta(C-13)), and O-18 isotope effects on C-13 shieldings ((1) Delta(13)C(O-18/O-16)) to be measured and hence comparisons with hemoproteins, C-O vibrational frequencies and X-ray structural data to be made. Negative polar interactions in the binding pocket and inhibition of Fe-->CO back-donation or positive distal polar interactions with amide NH groups appear to have little direct effect on (1)J(57Fe-13C) couplings. Similarly, the axial hindered base 1,2-dimethylimidazole has a minor effect on the (1)J(57Fe-13C) values despite higher rates of CO desorption being observed for such complexes. On the contrary, C-13 shieldings vary widely and an excellent correlation was found between the infrared C-O vibrational frequencies (nu(C-O)) and C-13 shieldings and a reasonable correlation with O-18 isotope effects on C-13 shieldings. This suggests that delta(C-13), nu(C-O) and (1) Delta(13)C(O-18/O-16) are accurate monitors of the multiple mechanisms by which steric and electronic interactions are released in superstructured heme model compounds. The C-13 shieldings of heme models cover a 4.0 ppm range which is extended to 7.0 ppm when several HbCO and MbCO species at different pH values are included. The latter were found to obey a similar linear delta(C-13) versus nu(C-O) relationship, which proves that both heme models and heme proteins are homogeneous from the structural and electronic viewpoint. Our results suggest that nu(C-O), delta(C-13) and (1) Delta(13)C(O-18/O-16) measurements reflect similar interaction which is primarily the modulation of pi back-bonding from the Fe d(x) to the CO pi* orbital by the distal pocket polar interactions. The lack of correlation between (1) Delta(13)C(O-18/O-16) and crystallographic CO bond lengths (r(C-O)) reflects significant uncertainties in the X-ray determination of the carbon and oxygen positions. | en |
| heal.access | campus | - |
| heal.fullTextAvailability | TRUE | - |
| heal.identifier.primary | Doi 10.1023/A:1008253901009 | - |
| heal.identifier.secondary | <Go to ISI>://000074811500006 | - |
| heal.identifier.secondary | http://download.springer.com/static/pdf/783/art%253A10.1023%252FA%253A1008253901009.pdf?auth66=1381649571_dae7fb51c5201bc0bb90a10ad4c8bda7&ext=.pdf | - |
| heal.journalName | J Biomol NMR | en |
| heal.journalType | peer reviewed | - |
| heal.language | en | - |
| heal.publicationDate | 1998 | - |
| heal.publisher | Springer Verlag (Germany) | en |
| heal.recordProvider | Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας | el |
| heal.type | journalArticle | - |
| heal.type.el | Άρθρο Περιοδικού | el |
| heal.type.en | Journal article | en |
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