| 1. |
- Hersleth, Hans-Petter, et al.
(författare)
-
The crystal structure of peroxymyoglobin generated through cryoradiolytic reduction of myoglobin compound III during data collection
- 2008
-
Ingår i: Biochemical Journal. - 0264-6021. ; 412, s. 257-264
-
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.
|
|
| 2. |
- Hersleth, Hans-Petter, et al.
(författare)
-
The Influence of X-Rays on the Structural Studies of Peroxide-Derived Myoglobin Intermediates
- 2008
-
Ingår i: Chemistry and Biodiversity. - 1612-1872. ; 5:10, s. 2067-2089
-
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.
|
|
| 3. |
- Roggen, Heidi, et al.
(författare)
-
2-Substituted agelasine analogs : Synthesis and biological activity, and structure and reactivity of synthetic intermediates
- 2011
-
Ingår i: Pure and Applied Chemistry. - 0033-4545 .- 1365-3075. ; 83:3, s. 645-653
-
Tidskriftsartikel (refereegranskat)abstract
- 2-Substituted N-methoxy-9-methyl-9H-purin-6-amines were synthesized either from their corresponding 6-chloro-9-methyl-9H-purines or 2-chloro-N-methoxy-9-methyl-9H-purin-6-amine. Great diversity in the amino/imino tautomeric ratios was observed and calculated based on H-1 NMR. The tautomers were identified by 1D and 2D H-1, C-13, and N-15 NMR techniques, and showed significant variation both in C-13 and N-15 shift values. Comparison of the tautomeric ratios with Hammett F values revealed that as the field/inductive withdrawing abilities of the 2-substituent increased, the ratio of amino: imino tautomers was shifted toward the amino tautomer. Computational chemistry exposed the significance of hydrogen bonding between solvent and the compound in question to reach accurate predictions for tautomeric ratios. B3LYP/def2-TZVP density functional theory (DFT) calculations resulted in quantitatively more accurate predictions than when employing the less expensive BP86 functional. N-7-Alkylation of the 2-substituted N-methoxy-9-methyl-9H-purin-6-amines showed that when the field/inductive withdrawing ability of the 2-substituent reached a certain point the reactivity drastically dropped. This correlated with the atomic charges on N-7 calculated using a natural bond orbital (NBO) analysis. Biological screening of the final 2-substituted agelasine analogs indicated that the introduction of a methyl group in the 2-position is advantageous for antimycobacterial and antiprotozoal activity, and that an amino function may improve activity against several cancer cell lines.
|
|
