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- Samuelsen, E.J., et al.
(author)
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The structure of polypyridine
- 2001
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In: Synthetic metals. - 0379-6779 .- 1879-3290. ; 124:2-3, s. 393-398
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Journal article (peer-reviewed)abstract
- X-ray diffraction on samples in the form of a deposited thin layer, a crushed powder and a flake were used to deduce models for the crystalline structure of polypyridine (-(C5H3N)n-), a conjugated polymer of great interest for applications. A monoclinic unit cell with lattice parameters a = 7.47 Å, b = 5.83 Å, c = 4.25 Å, ? = 108.7° containing two chains running along the c-axis and with the molecular plane normal to the a-axis gives a good fit with the observations. The interchain packing distance is about 3.6 Å, i.e. in the same range as intermolecular distances found in conductive charge transfer salts. The deposited layer is highly anisotropic, with the a-c-plane parallel to the substrate. © 2001 Elsevier Science B.V. All rights reserved.
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- Aasmundtveit, K.E., et al.
(author)
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Structural anisotropy of poly(alkylthiophene) films
- 2000
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 33:8, s. 3120-3127
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Journal article (peer-reviewed)abstract
- The structural anisotropy of various poly(alkylthiophene) films have been studied by X-ray diffraction, using both conventional methods and synchrotron radiation at grazing incidence. Solution-cast films orient with the side chains preferably normal to the film surface, whereas spin-cast films of nonstereoregular material orient with both the main and the side chains in the film plane. For thick (10-50 µm) solution-cast films, the degree of orientation depends strongly on the solvent used for casting, and on the stereoregularity of the polymer, films of stereoregular materials being more oriented than those of nonregular materials. The most oriented nonregular films are those cast from mixtures of chloroform and tetrahydrofuran. Thin (50-500 nm) solution-cast films are more oriented than the thicker ones, and the effects of different stereoregularity or different casting solvents are small. For spin-cast films, the degree of orientation is independent of substrate and solvent. Spin-cast films of stereoregular material have two different phases: One with the side chains normal to the substrate, and another where they are parallel to the substrate. The diffraction peaks of spin-cast poly(octylthiophene) narrow considerably upon heating.
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- Aasmundtveit, K.E., et al.
(author)
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Structural aspects of electrochemical doping and dedoping of poly(3,4-ethylenedioxythiophene)
- 2000
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In: Synthetic metals. - 0379-6779 .- 1879-3290. ; 113:1, s. 93-97
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Journal article (peer-reviewed)abstract
- Electrochemical dedoping and redoping of p-toluene sulfonate doped poly(3,4-ethylenedioxythiophene) (PEDOT) has been studied with in situ grazing incidence diffraction with water used as an electrolyte. The diffraction peak positions and integrated intensities do not change significantly during doping and dedoping, while the peak widths increase upon dedoping and decrease upon doping. This implies that the lattice parameters and the relative positions of the polymer chains and the p-toluene sulfonate ions remain unchanged, the redox processes being carried out by the motion of smaller ions between the polymer and the electrolyte, and that the structural order decreases upon dedoping and increases upon doping in a reversible manner.
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- Aasmundtveit, K.E., et al.
(author)
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Structural ordering in phenyl-substituted polythiophenes
- 2000
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 33:15, s. 5481-5489
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Journal article (peer-reviewed)abstract
- Various substituted poly(phenylthiophene)s have been studied by X-ray diffraction. They are semicrystalline, with very different degrees of crystallinity. Those with para-substituted phenyl groups have a low degree of crystallinity, whereas those with ortho-substituted phenyl groups are more crystalline. The most crystalline materials in this study have two equally long substituents on the phenyl ring, one at the ortho position and the other at the ortho or meta position on the opposite side of the phenyl ring. Poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) was most thoroughly studied, and a structural model is proposed. The structure of PDOPT is quite different from previously studied substituted polythiophenes in that the octyl side chains are directed normal to the thiophene planes. In this way, the conjugated polymer chains are kept separated from each other. Solution-cast and spin-cast PDOPT films are anisotropic, with the octyl side chains oriented normal to the film surface in both cases. This is contrary to the situation for poly(3-alkylthiophene)s, where solution-cast and spin-cast films orient in different ways.
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| 7. |
- Holvik, K, et al.
(author)
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Low serum concentrations of alpha-tocopherol are associated with increased risk of hip fracture : A NOREPOS study
- 2014
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In: Osteoporosis International. - : Springer Science and Business Media LLC. - 0937-941X .- 1433-2965. ; 25:11, s. 2545-2554
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Journal article (peer-reviewed)abstract
- We investigated the risk of hip fracture according to circulating alpha-tocopherol, a plant-derived substance with antioxidant properties, in community-dwelling older Norwegians. We found a linear increasing risk of hip fracture with lower serum alpha-tocopherol concentrations, with a 51 % higher risk in the lowest compared to the highest quartile.INTRODUCTION:Oxidative stress is a suggested contributing cause of osteoporosis and fractures. Vitamin E (α-tocopherol) has potent antioxidant properties in humans. The relationship between circulating α-tocopherol and fracture risk is not established. The aim of this study was to investigate the association between serum α-tocopherol concentrations and risk of hip fracture during up to 11 years of follow-up.METHODS:We performed a case-cohort analysis among 21,774 men and women aged 65-79 years who participated in four community-based health studies in Norway 1994-2001. Serum α-tocopherol concentrations at baseline were determined in 1,168 men and women who subsequently suffered hip fractures (median follow-up 8.2 years) and in a random sample (n = 1,434) from the same cohort. Cox proportional hazard regression adapted for gender-stratified case-cohort data was performed.RESULTS:Median (25, 75 percentile) serum α-tocopherol was 30.0 (22.6, 38.3) μmol/L, and it showed a linear inverse association with hip fracture: hazard ratio (HR) 1.11 (95 % confidence interval (CI) 1.04-1.20) per 10-μmol/L decrease in serum α-tocopherol, adjusted for gender and study center. The lowest compared to the highest quartile conferred an HR of 1.51 (95 % CI 1.17-1.95), adjusted for gender and study center. Adjustment for smoking, month of blood sample, BMI, education, physical inactivity, self-rated health, and serum 25-hydroxyvitamin D (25(OH)D) yielded similar results. Taking serum total cholesterol concentration into account attenuated the association somewhat: HR of hip fracture was 1.37 (95 % CI 1.05-1.77) in first versus fourth quartile of serum α-tocopherol/total cholesterol ratio.CONCLUSIONS:Low serum concentrations of α-tocopherol were associated with increased risk of hip fracture in older Norwegians.
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| 8. |
- Samuelsen, J. T., et al.
(author)
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The dental monomer HEMA causes proteome changes in human THP-1 monocytes
- 2019
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In: Journal of Biomedical Materials Research Part A. - : Wiley. - 1549-3296. ; 107:4, s. 851-859
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Journal article (peer-reviewed)abstract
- Resin-based biomaterials are widely used in medical and dental treatment, and both clinicians and patients are exposed to the materials. The knowledge of toxicity is mainly based on in vitro studies at exposure concentrations that induce cell death. However, severe cell damage and cell death signaling may overshadow essential cellular events caused by a possible toxicant. For dental resins, the knowledge of interaction with living cells at more clinical relevant exposure doses is sparse. 2-Hydroxyethylmethacrylate (HEMA) is a commonly used monomer in dental resins. Measuring cellular adaptation to HEMA at concentrations that did not reduce cell viability was the main focus of this study. Stable isotope labeling with amino acids in cell culture was used to measure proteome changes in cultured THP-1 cells exposed to HEMA. Western blotting verified the results. Cells exposed to HEMA increased their level of several cytoprotective proteins. The observed adaptation is compatible with increased oxidative burden caused by GSH depletion and the electrophilic characteristic of HEMA. The present approach to analyzing the toxic potential of HEMA yielded information on interactions with living cells is not previously reported. This detailed information is of great value to make better predictions of possible side effects in the clinic. (c) 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 851-859, 2019.
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| 14. |
- Roberts, E. M., et al.
(author)
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Water masses constrain the distribution of deep-sea sponges in the North Atlantic Ocean and Nordic Seas
- 2021
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In: Marine Ecology Progress Series. - : INTER-RESEARCH. - 0171-8630 .- 1616-1599. ; 659, s. 75-96
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Journal article (peer-reviewed)abstract
- Water masses are bodies of water with distinctive physical and biogeochemical properties. They impart vertical structure to the deep ocean, participate in circulation, and can be traced over great distances, potentially influencing the distributions of deep-sea fauna. The classic potential temperature-salinity (theta-s) diagram was used to investigate deep-sea sponge (demosponge genus Geodia) association with water masses over the North Atlantic Ocean and Nordic Seas. A novel analysis was conducted, based on sampling the curvature of climatological mean theta-s curves at sponge locations. Sponges were particularly associated with turning points in the theta-s curves, indicative of intermediate and deep water masses. Arctic geodiid species (G. hentscheli and G. parva) were associated with Arctic intermediate and deep waters in the Nordic Seas, and with dense overflows into the northern North Atlantic. Boreal species (G. atlantica, G. barretti, G. macandrewii, and G. phlegraei) were associated with upper and intermediate water masses in the Northeast Atlantic and with upper, Atlantic-derived waters in the Nordic Seas. Taken together with distributional patterns, a link with thermohaline currents was also inferred. We conclude that water masses and major current pathways structure the distribution of a key deep-sea benthic faunal group on an ocean basin scale. This is most likely because of a combination of the physical constraints they place on the dispersal of early life-history stages, ecophysiological adaptation (evolved tolerances) to specific water masses, and the benefits to filter-feeders of certain phenomena linked to water column structure (e.g. nepheloid layers, internal waves/ tides, density-driven currents).
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| 15. |
- Samuelsen, Orjan, et al.
(author)
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Molecular Epidemiology of Metallo-beta-Lactamase-Producing Pseudomonas aeruginosa Isolates from Norway and Sweden Shows Import of International Clones and Local Clonal Expansion
- 2010
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In: Antimicrobial Agents and Chemotherapy. - 1098-6596. ; 54:1, s. 346-352
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Journal article (peer-reviewed)abstract
- Scandinavia is considered a region with a low prevalence of antimicrobial resistance. However, the number dof multidrug-resistant (MDR) Gram-negative bacteria is increasing, including metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa. In this study MBL-producing P. aeruginosa isolates identified in Norway (n = 4) and Sweden (n = 9) from 1999 to 2007 were characterized. Two international clonal complexes (CC), CC111 (n = 8) and CC235 (n = 2), previously associated with MBL-producing isolates, were dominant. CC111 isolates (ST111/229; serotype O12; bla(VIM-2)) included clonally related isolates identified in Skane County, Sweden (n = 6), and two isolates associated with importation from Greece and Denmark. In all CC111 isolates, bla(VIM-2) was located in integron In59.2 or In59 variants. The two CC235 isolates (ST235/ST230; serotype O11; bla(VIM-4)) were imported from Greece and Cyprus, were possibly clonally related, and carried bla(VIM-4) in two different integron structures. Three isolates imported from Ghana (ST233; serotype O6; bla(VIM-2)), Tunisia (ST654; serotype O11; bla(VIM-2)), and Thailand (ST260; serotype O6; bla(IMP-14)) were clonally unrelated. ST233 was part of a new CC (CC233) that included other MBL-producing isolates, while ST654 could also be part of a new CC associated with MBL producers. In the isolates imported from Ghana and Tunisia, bla(VIM-2) was part of unusual integron structures lacking the 3' conserved segment and associated with transposons. The bla(VIM) gene was found to be located on the chromosome in all isolates. Known risk factors for acquisition of MBL were reported for all patients except one. The findings suggest that both import of successful international clones and local clonal expansion contribute to the emergence of MBL-producing P. aeruginosa in Scandinavia.
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| 16. |
- Spåhr, H, et al.
(author)
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Analysis of Schizosaccharomyces pombe mediator reveals a set of essential subunits conserved between yeast and metazoan cells.
- 2001
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 98:21, s. 11985-90
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Journal article (peer-reviewed)abstract
- With the identification of eight new polypeptides, we here complete the subunit characterization of the Schizosaccharomyces pombe RNA polymerase II holoenzyme. The complex contains homologs to all 10 essential gene products present in the Saccharomyces cerevisiae Mediator, but lacks clear homologs to any of the 10 S. cerevisiae components encoded by nonessential genes. S. pombe Mediator instead contains three unique components (Pmc2, -3, and -6), which lack homologs in other cell types. Presently, pmc2(+) and pmc3(+) have been shown to be nonessential genes. The data suggest that S. pombe and S. cerevisiae share an essential protein module, which associates with nonessential speciesspecific subunits. In support of this view, sequence analysis of the conserved yeast Mediator components Med4 and Med8 reveals sequence homology to the metazoan Mediator components Trap36 and Arc32. Therefore, 8 of 10 essential genes conserved between S. pombe and S. cerevisiae also have a metazoan homolog, indicating that an evolutionary conserved Mediator core is present in all eukaryotic cells. Our data suggest a closer functional relationship between yeast and metazoan Mediator than previously anticipated.
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