| 1. |
- Hersleth, Hans-Petter, et al.
(författare)
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The crystal structure of peroxymyoglobin generated through cryoradiolytic reduction of myoglobin compound III during data collection
- 2008
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Ingår i: Biochemical Journal. - 0264-6021. ; 412, s. 257-264
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Tidskriftsartikel (refereegranskat)abstract
- Myoglobin has the ability to react with hydrogen peroxide, generating high-valent complexes similar to peroxidases (compounds I and II), and in the presence of excess hydrogen peroxide a third intermediate, compound III, with an oxymyoglobin-type structure is generated from compound II. The compound III is, however, easily one-electron reduced to peroxymyoglobin by synchrotron radiation during crystallograpic data collection. We have generated and solved the 1.30 angstrom (1 angstrom= 0.1 nin) resolution crystal structure of the peroxymyoglobin intermediate, which is isoelectric to compound 0 and has a Fe-O distance of 1.8 angstrom and O-O bond of 1.3 angstrom in accordance with a Fe-II-O-O- (or Fe-III-O-O2-) structure. The generation of the peroxy intermediate through reduction of compound III by X-rays shows the importance of using single-crystal microspectrophotometry when doing crystallography on metal loproteins. After having collected crystallographic data on a peroxy-generated myoglobin crystal, we were able (by a short annealing) to break the O-O bond leading to formation of compound II. These results indicate that the cryoradiolytic-generated peroxymyoglobin is biologically relevant through its conversion into compound II upon heating. Additionally, we have observed that the Xe1 site is occupied by a water molecule, which might be the leaving group in the compound II to compound III reaction.
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| 2. |
- Hersleth, Hans-Petter, et al.
(författare)
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The Influence of X-Rays on the Structural Studies of Peroxide-Derived Myoglobin Intermediates
- 2008
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Ingår i: Chemistry and Biodiversity. - 1612-1872. ; 5:10, s. 2067-2089
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Forskningsöversikt (refereegranskat)abstract
- In recent years, the awareness of potential radiation damage of metal centers in protein crystals during crystallographic data collection has received increasing attention. The radiation damage can lead to radiation-induced changes and reduction of the metal sites. One of the research fields where these concerns have been comprehensively addressed is the study of the reaction intermediates of the heme peroxidase and oxygenase reaction cycles. For both the resting states and the high-valent intermediates, the X-rays used in the structure determination have given undesired side effects through radiation-induced changes to the trapped intermediates. However, X-rays have been used to generate and trap the peroxy/hydroperoxy state in crystals. In this review, the structural work and the influence of X-rays on these intermediates in myoglobin are summarized and viewed in light of analogous studies on similar intermediates in peroxidases and oxygenases.
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| 3. |
- Zoppellaro, Giorgio, et al.
(författare)
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Studies of Ferric Heme Proteins with Highly Anisotropic/Highly Axial Low Spin (S=1/2) Electron Paramagnetic Resonance Signals with bis-Histidine and Histidine-Methionine Axial Iron Coordination
- 2009
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Ingår i: Biopolymers. - : Wiley. - 0006-3525 .- 1097-0282. ; 91:12, s. 1064-1082
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Forskningsöversikt (refereegranskat)abstract
- Six-coordinated heme groups are involved in a large variety of electron transfer reactions because of their ability to exist in both the ferrous (Fe2+) andferric (Fe3+) state without any large differences in structure. Our studies on hemes coordinated by two histidines (bis-His) and hemes coordinated by histidine and methionine (His-Met) will be reviewed. In both of these coordination environments, the heme core can exhibit ferric low spin (electron paramagnetic resonance EPR) signals with large g(max) values (also called Type I, highly anisotropic low spin, or highly axial low spin, HALS species) as Well as rhombic EPR (Type II) signals. In bis-His coordinated hemes rhombic and HALS envelopes are related to the orientation of the His groups with respect to each other such that (i) parallel His planes results in a rhombic signal and (ii) perpendicular His planes results in a HALS signal. Correlation between the structure of the heme and its ligands for heme with His-Met axial ligation and ligand-field parameters, as derived from a large series of cytochrome c variants, show, however, that for such a combination of axial ligands there is no clear-cut difference between the large g(max) and the "small ganisotropy" cases as a result of the relative Met-His arrangements. Nonetheless, a new linear correlation links the average shift of the heme methyl groups with the g(max) values. (c) 2009 Wiley Periodicals, Inc. Biopolymers 91: 1064-1082, 2009.
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