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- Ardlin, Berit I., et al.
(författare)
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Corrosion of dental nickel-aluminum bronze with a minor gold content-mechanism and biological impact
- 2009
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Ingår i: Journal of Biomedical Materials Research. Part B - Applied biomaterials. - Malden : Wiley-Blackwell. - 1552-4973 .- 1552-4981. ; 88B:2, s. 465-473
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: To study corrosion and to evaluate biological effects in vitro of corrosion products of a copper-aluminum-nickel alloy with 2% gold. Methods: The alloy NPGTM+2 with the nominal composition Cu:77.3; Al:7.8; Ni:4.3; Fe:3.0; Zn:2.7; Au:2.0; and Mn:1.7 was characterized. Static immersion in acidic saline, pH 2.2-2.4, was used to determine release of metallic elements in a milieu simulating the condition of plaque build-up in interproximal areas of the tooth. Corrosion and surface reactions in saline and artificial saliva were studied by electrochemical techniques including registration of open-circuit-potentials, polarization curves and impedance spectra. Extracts were made in cell culture media and acidic saline and used for MTT test for cytotoxicity and HET-CAM method for irritation. Results: The mean amount of elements released in the acidic saline were in g cm-2 : Cu:632; Al:210; Ni:144; Fe:122; Zn:48; Mn:52. No protective film was formed on the surface of the alloy, as extensive corrosion was observed in both saline and artificial saliva. The corrosion rate was higher in saline than in artificial saliva. Acidic extracts of the alloy diluted up to 64 times reduced cell viability with 80% or more. The extract induced coagulation of the blood vessels of the CAM and was rated as moderate irritant solution. Significance: The nickel-aluminum bronze showed high corrosion rate caused by an inability to create a protective surface layer. High levels of toxic elements were found after static immersion testing, and the corrosion products had a distinct adverse effect on the biological activity.
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| 4. |
- Kjellsson, A., et al.
(författare)
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Hydrogen exchange in a large 29 kD protein and characterization of molten globule aggregation by NMR
- 2003
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 42:2, s. 363-374
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Tidskriftsartikel (refereegranskat)abstract
- The nature of denatured ensembles of the enzyme human carbonic anhydrase (HCA) has been extensively studied by various methods in the past. The protein constitutes an interesting model for folding studies that does not unfold by a simple two-state transition, instead a molten globule intermediate is highly populated at 1.5 M GuHCl. In this work, NMR and H/D exchange studies have been conducted on one of the isozymes, HCA I. The H/D exchange studies, which were enabled by the previously obtained resonance assignment of HCA I, have been used to identify unfolded forms that are accessible from the native state. In addition, the GuHCl-induced unfolded states of HCA I have also been characterized by NMR at GuHCl concentrations in the 0-5 M range. The most important findings in this work are as follows: (1) Amide protons located in the center of the ß-sheet require global unfolding events for efficient H/D exchange. (2) The molten globule and the native state give similar protection against H/D exchange for all of the observable amide protons (i.e., water seems not to efficiently penetrate the interior of the molten globule). (3) At high protein concentrations, the molten globule can form large aggregates, which are not detectable by solution-state NMR methods. (4) The unfolded state (U), present at GuHCl concentrations above 2 M, is composed of an ensemble of conformations having residual structures with different stabilities.
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| 7. |
- Qian, H, et al.
(författare)
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Solution structure of phenol hydroxylase protein component P2 determined by NMR spectroscopy.
- 1997
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 36:3
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Tidskriftsartikel (refereegranskat)abstract
- Phenol hydroxylase from Pseudomonas sp. CF600 is a member of a family of binuclear iron-center-containing multicomponent oxygenases, which catalyzes the conversion of phenol and some of its methyl-substituted derivatives to catechol. In addition to a reductase component which transfers electrons from NADH, optimal turnover of the hydroxylase requires P2, a protein containing 90 amino acids which is readily resolved from the other components. The three-dimensional solution structure of P2 has been solved by 3D heteronuclear NMR spectroscopy. On the basis of 1206 experimental constraints, including 1060 distance constraints obtained from NOEs, 70 phi dihedral angle constraints, 42 psi dihedral angle constraints, and 34 hydrogen bond constraints, a total of 12 converged structures were obtained. The atomic root mean square deviation for the 12 converged structure with respect to the mean coordinates is 2.48 A for the backbone atoms and 3.85 A for all the heavy atoms. This relatively large uncertainty can be ascribed to conformational flexibility and exchange. The molecular structure of P2 is composed of three helices, six antiparallel beta-strands, one beta-hairpin, and some less ordered regions. This is the first structure among the known multicomponent oxygenases. On the basis of the three-dimensional structure of P2, sequence comparisons with similar proteins from other multicomponent oxygenases suggested that all of these proteins may have a conserved structure in the core regions.
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| 8. |
- Trogen, G B, et al.
(författare)
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The solution NMR structure of a blue-green algae hepatotoxin, microcystin-RR--a comparison with the structure of microcystin-LR.
- 1998
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Ingår i: European Journal of Biochemistry. - 0014-2956 .- 1432-1033. ; 258:2, s. 301-12
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Tidskriftsartikel (refereegranskat)abstract
- The microcystin-RR structures are compared with the structures of microcystin-LR in solution as well as in the crystal structure of the complex with protein phosphatase. The gross structures of the two peptides are similar, but with a more accentuated and compact saddle structure for microcystin-RR. The structural differences affect the hydrogen-bond pattern in the peptides and the location of the side chain of N-methyldehydroalanine, both of which are important for the ability of the peptide to form a tight complex with protein phosphatase. These structural differences may contribute to the observed differences in toxicity of microcystin-RR and microcystin-LR.
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