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  • 251.
    Badea, Silviu-Laurentiu
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mustafa, Majid
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Leachability and desorption of PCBs from soil and their dependency on pH and dissolved organic matter2014In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 499, p. 220-227Article in journal (Refereed)
    Abstract [en]

    pH affects both soil–water partitioning coefficient (Kd) of polychlorinated biphenyls (PCBs) and dissolved organic matter (DOM), thereby influencing PCBs' leachability from contaminated soils. To explore these incompletely understood interactions, the leachability of 11 selected PCBs in a naturally aged soil was investigated in pH static leaching tests spanning a wide pH range (2 to 9). The Kd was calculated for each of the PCBs, based on their observed concentrations in the soil and leachates obtained from each test. The concentration and composition of DOM in each leachate were also determined, the latter using FTIR spectroscopy. Correlations between the DOM's FTIR spectra and Kd values were investigated by orthogonal projections to latent structures. The log Kd-values varied among the PCB congeners and were most variable at low pH, but the values for all studied congeners decreased with increasing pH, by up to 3 log units (for PCB 187). In the pH 5–7 interval, an abrupt decrease in log Kd values with increases in pH was observed, although the total organic carbon content remained relatively stable. The FTIR data indicate that fulvic and humic acids in DOM partially deprotonate as the pH rises from 5 to 7.

  • 252.
    Badea, Silviu-Laurentiu
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mustafa, Majid
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Leachability of PCBs in soil and its pH and dissolved organic matter (DOM) dependencyManuscript (preprint) (Other academic)
    Abstract [en]

    The leachability of eleven selected PCBs from naturally aged soil (Västervik, Sweden) was investigated in relation to the composition and concentration of dissolved organic matter at different pH (2 to 9), using a pH static test with initial acid/base addition. The batch leaching tests were performed on 50 g aliquots of a PCBs contaminated soil at a liquid to solid ratio (L/S) of 10 L/Kg. The PCBs were analyzed by gas chromatography coupled with high resolution mass spectrometry (GC-HRMS). The composition and of dissolved organic matter (DOM) at different pH values was explored by FTIR spectroscopy. The correlation between the FTIR data obtained for DOM and the log Kd values of PCBs was explored by orthogonal projections to latent structures (OPLS).  The log Kd-values of all target PCBs decreased with increased pH values and the log Kd-values were highly correlated with the concentration of total organic carbon (TOC) in the leachates. For the lower chlorinated congener, PCB 28, this correlation was weaker. The variation of fractions of concentrations of mono-ortho to di-ortho PCBs (PCB 66 to PCB 52 and PCB 105 to PCB 101) indicated an influence of the ortho-chlorine atoms through pH effects on their leachability. The FTIR analysis of DOM showed that the least chlorinated and hydrophobic PCB congeners (i.e. PCB 28) might be associated with the hydrophilic fraction (i.e. carboxylic groups) of the DOM.

  • 253.
    Badea, Silviu‐Laurentiu
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Vogt, Carsten
    Gehre, Matthias
    Fischer, Anko
    Danet, Andrei‐Florin
    Richnow, Hans‐Hermann
    Development of an enantiomer-specific stable carbon isotope analysis (ESIA) method for assessing the fate of α‐hexachlorocyclohexane in the environment2011In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 25, no 10, p. 1363-1372Article in journal (Refereed)
    Abstract [en]

    α‐Hexachlorocyclohexane (α‐HCH) is the only chiral isomer of the eight 1,2,3,4,5,6‐HCHs and we have developed an enantiomer‐specific stable carbon isotope analysis (ESIA) method for the evaluation of its fate in the environment.The carbon isotope ratios of the α‐HCH enantiomers were determined for a commercially available α‐HCH sample using a gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS) system equipped with a chiral column. The GC‐C‐IRMS measurements revealed δ‐values of −32.5 ± 0.8‰ and −32.3 ± 0.5‰ for (−) α‐HCH and (+) α‐HCH, respectively. The isotope ratio of bulk α‐HCH was estimated to be −32.4 ± 0.6‰ which was in accordance with the δ‐values obtained by GC‐C‐IRMS (−32.7 ± 0.2‰) and elemental analyzer‐isotope ratio mass spectrometry (EA‐IRMS) of the bulk α‐HCH (−32.1 ± 0.1‰). The similarity of the isotope ratio measurements of bulk α‐HCH by EA‐IRMS and GC‐C‐IRMS indicates the accuracy of the chiral GC‐C‐IRMS method. The linearity of theα‐HCH ESIA method shows that carbon isotope ratios can be obtained for a signal size above 100mV. The ESIA measurements exhibited standard deviations (2σ) that were mostly < ± 0.5‰. In order to test the chiral GC‐C‐IRMS method, the isotope compositions of individual enantiomers in biodegradation experiments of α‐HCH withClostridium pasteurianum and samples from a contaminated field site were determined. The isotopic compositions of theα‐HCHenantiomers show a range of enantiomeric and isotope patterns, suggesting that enantiomeric and isotopefractionation can serve as an indicator for biodegradation and source characterization of α‐HCH in the environment.

  • 254.
    Badea, Silviu-Laurentiu
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Vogt, Carsten
    Weber, Stefanie
    Danet, Andrei-Florin
    Richnow, Hans-Hermann
    Stable isotope fractionation of γ-Hexachlorocyclohexane (Lindane) during reductive dechlorination by two strains of sulfate-reducing bacteria2009In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, no 9, p. 3155-3161Article in journal (Refereed)
    Abstract [en]

    Carbon isotope fractionation factors were determined with the dichloro elimination of γ-hexachlorocyclohexane (γ-HCH) by the sulfate-reducing bacteria Desulfococcus multivorans DSM 2059 and Desulfovibrio gigas DSM 1382. Both strains are known for cometabolic HCH dechlorination. Degradation experiments with γ-HCH in concentrations of 22−25 μM were carried out using benzoate (for D. multivorans) and lactate (for D. gigas) as electron donors, respectively. γ-HCH was dechlorinated by both bacterial strains within four weeks, and the metabolites γ-3,4,5,6-tetrachlorocyclohexene (γ-TCCH), chlorobenzene (CB), and benzene were formed. The carbon isotope fractionation of γ-HCH dechlorination was quantified by the Rayleigh model, using a bulk enrichment factor (εC) of −3.9 ± 0.6 for D. gigas and −3.4 ± 0.5 for D. multivorans, which correspond to apparent kinetic isotope effect (AKIEC) values of 1.023 ± 0.004 or 1.02 ± 0.003 for stepwise Cl−C bond cleavage. The extent and range of isotope fractionation suggest that γ-HCH dechlorination can be monitored in anoxic environments by compound-specific isotope analysis (CSIA).

  • 255.
    Bagdasarian, Arine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Cancer Therapy: - The mitochondrial Bcl-2 protein familyas drug targets for inducing cell death2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 256.
    Bailey, Leslie
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Gylfe, Åsa
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Sundin, Charlotta
    Muschiol, Sandra
    Elofsson, Mikael
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Nordström, Peter
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Henriques-Normark, Birgitta
    Lugert, Raimond
    Waldenström, Anders
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Wolf-Watz, Hans
    Bergström, Sven
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Small molecule inhibitors of type III secretion in Yersinia block the Chlamydia pneumoniae infection cycle2007In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 581, no 4, p. 587-595Article in journal (Refereed)
    Abstract [en]

    Intracellular parasitism by Chlamydiales is a complex process involving transmission of metabolically inactive particles that differentiate, replicate, and re-differentiate within the host cell. A type three secretion system (T3SS) has been implicated in this process. We have here identified small molecules of a chemical class of acylated hydrazones of salicylaldehydes that specifically blocks the T3SS of Chlamydia. These compounds also affect the developmental cycle showing that the T3SS has a pivotal role in the pathogenesis of Chlamydia. Our results suggest a previously unexplored avenue for development of novel anti-chlamydial drugs.

  • 257.
    Bakken Andersen, Randi Kari
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bruk av sovemedisin blant eldre på institusjon: En intervjustudie utført i tre kommuner i Hallingdal, Norge2012Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 258. Balmer, Marianne E
    et al.
    Poiger, Thomas
    Droz, Christian
    Romanin, Kathrin
    Bergqvist, Per-Anders
    Umeå University, Faculty of Science and Technology, Chemistry.
    Müller, Markus D
    Buser, Hans-Rudolf
    Occurrence of Methyl Triclosan, a Transformation Product of the Bactericide Triclosan, in Fish from Various Lakes in Switzerland2004In: Environmental Science & Technology, Vol. 38, no 2, p. 390-5Article in journal (Refereed)
    Abstract [en]

    The bactericide triclosan and methyl triclosan, an environmental transformation product thereof, have been previously detected in lakes and a river in Switzerland. Both compounds are emitted via wastewater treatment plants (WWTPs), with methyl triclosan probably being formed by biological methylation. Passive sampling with semipermeable membrane devices (SPMDs) showed the presence of methyl triclosan in some lakes, suggesting some potential for bioaccumulation of the compound. In this study, we report the presence of methyl triclosan in fish (white fish, coregonus sp.; roach, rutilus rutilus) from various lakes in Switzerland receiving inputs from WWTPs. Identification of the compound was based on mass spectral (MS) evidence including MS/MS data. The concentrations of methyl triclosan in the fish were up to 35 ng g-1 on a wet weight basis and up to 365 ng g-1 on a lipid basis with concentrations in a relatively narrow range for fish from the same lake (Thunersee, 4-6 ng g-1; Zürichsee, 32-62 ng g-1; Pfäffikersee, 43-56 ng g-1; Greifensee, 165-365 ng g-1, lipid basis). No methyl triclosan (<1 ng g-1, lipid basis) was detected in fish (lake trout, salmo trutta) from a remote lake in Sweden (Häbberstjärnen) and in fish (roach) from a small lake in Switzerland with no input from WWTPs (Hüttnersee, <2-<5 ng g-1, lipid basis). The concentrations of methyl triclosan in fish correlated (r2 = 0.85) with the ratio of population in the watershed to water throughflow of the lakes (P/Q ratio), which is considered to be a measure for the domestic burden from WWTPs to a lake. Passive sampling with SPMDs confirmed the presence of methyl triclosan in lakes and a river (Zürichsee and Greifensee; Limmat) but not in a remote mountain lake (Jörisee) and in Hüttnersee. The bioconcentration factor (BCF) of methyl triclosan estimated from the fish data and SPMD-derived water concentrations was in the order of 1-2.6 × 105 (lipid basis) and thus in the range of other persistent organic pollutants. SPMDs were found to be reliable for monitoring low concentrations of methyl triclosan in surface water. Methyl triclosan appears to be a suitable marker for WWTP-derived lipophilic contaminants in the aquatic environment and fish.

  • 259.
    Bang, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Acetylkolinesterashämmare vid Alzheimer´s sjukdom: Skillnad i effekt och biverkningsprofil2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 260. Bao, Xiaofeng
    et al.
    Gylfe, Åsa
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    Sturdevant, Gail L.
    Gong, Zheng
    Xu, Shuang
    Caldwell, Harlan D.
    Elofsson, Mikael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fan, Huizhou
    Benzylidene acylhydrazides inhibit chlamydial growth in a type III secretion- and iron chelation-independent manner2014In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 196, no 16, p. 2989-3001Article in journal (Refereed)
    Abstract [en]

    Chlamydiae are widespread Gram-negative pathogens of humans and animals. Salicylidene acylhydrazides, developed as inhibitors of type III secretion system (T3SS) in Yersinia spp., have an inhibitory effect on chlamydial infection. However, these inhibitors also have the capacity to chelate iron, and it is possible that their antichlamydial effects are caused by iron starvation. Therefore, we have explored the modification of salicylidene acylhydrazides with the goal to uncouple the antichlamydial effect from iron starvation. We discovered that benzylidene acylhydrazides, which cannot chelate iron, inhibit chlamydial growth. Biochemical and genetic analyses suggest that the derivative compounds inhibit chlamydiae through a T3SS-independent mechanism. Four single nucleotide polymorphisms were identified in a Chlamydia muridarum variant resistant to benzylidene acylhydrazides, but it may be necessary to segregate the mutations to differentiate their roles in the resistance phenotype. Benzylidene acylhydrazides are well tolerated by host cells and probiotic vaginal Lactobacillus species and are therefore of potential therapeutic value.

  • 261.
    Barange, Deepak Kumar
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Johnson, Magnus T.
    Cairns, Andrew G.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olsson, Roger
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Regio- and Stereoselective Alkylation of Pyridine-N-oxides: Synthesis of Substituted Piperidines and Pyridines2016In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 18, no 24, p. 6228-6231Article in journal (Refereed)
    Abstract [en]

    Regio- and stereoselective addition of alkyl Grignard reagents to pyridine-N-oxides gave C2-alkylated N-hydroxy-1,2,5,6-tetrahydropyridines and trans-2,3-disubstituted N-hydroxy-1,2,5,6-tetrahydropyridines in good to excellent yields. These intermediates were aromatized or alternatively reduced in one-pot methodologies for efficient syntheses of alkylpyridines or piperidines, respectively. These reactions have a broad substrate scope and short reaction times.

  • 262.
    Barbero, David
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Yu, Junchun
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Carbon nanotube networks: nano-engineering of SWNT networks for enhanced charge transport at ultralow nanotube loading2014In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 19, p. 3164-Article in journal (Refereed)
    Abstract [en]

    Arrays of nano-engineered carbon nanotube networks embedded in nanoscale polymer structures enable highly efficient charge transport as demonstrated by D. R. Barbero and co-workers on page 3111. An increase in charge transport by several orders of magnitude is recorded at low nanotube loading compared to traditional random networks in either insulating (polystyrene) or semiconducting (polythiophene) polymers. These novel networks are expected to enhance the performance of next generation hybrid and carbon based photovoltaic devices.

  • 263.
    Barbero, David
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Yu, Junchun
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nano-engineering of SWNT networks for enhanced charge transport at ultralow nanotube loading2014In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 19, p. 3111-3117Article in journal (Refereed)
    Abstract [en]

    We demonstrate a simple and controllable method to form periodic arrays of highly conductive nano-engineered single wall carbon nanotube networks from solution. These networks increase the conductivity of a polymer composite by as much as eight orders of magnitude compared to a traditional random network. These nano-engineered networks are demonstrated in both polystyrene and polythiophene polymers.

  • 264.
    Barbero, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ultralow Percolation Threshold in Nanoconfined Domains2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 10, p. 9906-9913Article in journal (Refereed)
    Abstract [en]

    Self-assembled percolated networks play an important role in many advanced electronic materials and devices. In nanocarbon composites, decreasing the percolation threshold phi(c) is of paramount importance to reduce nanotube bundling, minimize material resources and costs, and enhance charge transport. Here we demonstrate that three-dimensional nanoconfinement in single-wall carbon nanotube/polymer nanocomposites produces a strong reduction in phi(c) reaching the lowest value ever reported in this system of phi(c) approximate to 1.8 X 10(-5) wt % and 4-5 orders of magnitude lower than the theoretical statistical percolation threshold oh phi(stat) Moreover, a change in network resistivity and electrical conduction was observed with increased confinement, and a simple resistive model is used to accurately estimate the difference in is in the confined networks. These results are explained in terms of networks' size, confinement, and tube orientation as determined by atomic force microscopy, electrical conductivity measurements, and polarized Raman spectroscopy. Our findings provide important insight into nanoscale percolated networks and should find application in electronic nanocomposites and devices.

  • 265.
    Barbero, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Stranks, Samuel D.
    Functional single-walled carbon nanotubes and nanoengineered networks for organic- and Perovskite-solar-cell applications2016In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 28, no 44, p. 9668-9685Article in journal (Refereed)
    Abstract [en]

    Carbon nanotubes have a variety of remarkable electronic and mechanical properties that, in principle, lend them to promising optoelectronic applications. However, the field has been plagued by heterogeneity in the distributions of synthesized tubes and uncontrolled bundling, both of which have prevented nanotubes from reaching their full potential. Here, a variety of recently demonstrated solution-processing avenues is presented, which may combat these challenges through manipulation of nanoscale structures. Recent advances in polymer-wrapping of single-walled carbon nanotubes (SWNTs) are shown, along with how the resulting nanostructures can selectively disperse tubes while also exploiting the favorable properties of the polymer, such as light-harvesting ability. New methods to controllably form nanoengineered SWNT networks with controlled nanotube placement are discussed. These nanoengineered networks decrease bundling, lower the percolation threshold, and enable a strong enhancement in charge conductivity compared to random networks, making them potentially attractive for optoelectronic applications. Finally, SWNT applications, to date, in organic and perovskite photovoltaics are reviewed, and insights as to how the aforementioned recent advancements can lead to improved device performance provided.

  • 266.
    Barzegar, Hamid R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nitze, Florian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sharifi, Tiva
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tai, Cheuk W.
    Malolepszy, Artur
    Stobinski, Leszek
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Simple Dip-Coating Process for the Synthesis of Small Diameter Single-Walled Carbon Nanotubes-Effect of Catalyst Composition and Catalyst Particle Size on Chirality and Diameter2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 22, p. 12232-12239Article in journal (Refereed)
    Abstract [en]

    We report on a dip-coating method to prepare catalyst particles (mixture of iron and cobalt) with a controlled diameter distribution on silicon wafer substrates by changing the solution's concentration and withdrawal velocity. The size and distribution of the prepared catalyst particles were analyzed by atomic force microscopy. Carbon nanotubes were grown by chemical vapor deposition on the substrates with the prepared catalyst particles. By decreasing the catalyst particle size to below 10 nm, the growth of carbon nanotubes can be tuned from few-walled carbon nanotubes, with homogeneous diameter, to highly pure single-walled carbon nanotubes. Analysis of the Raman radial breathing modes, using three different Raman excitation wavelengths (488, 633, and 785 nm), showed a relatively broad diameter distribution (0.8-1.4 nm) of single-walled carbon nanotubes with different chiralities. However, by changing the composition of the catalyst particles while maintaining the growth parameters, the chiralities of single-walled carbon nanotubes were reduced to mainly four different types, (12, 1), (12, 0), (8, 5), and (7, 5), accounting for about 70% of all nanotubes.

  • 267.
    Barzegar, Hamid Reza
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA.
    Gracia Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics. Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    C60/Collapsed Carbon Nanotube Hybrids: A Variant of Peapods2015In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, no 2, p. 829-834Article in journal (Refereed)
    Abstract [en]

    We examine a variant of so-called carbon nanotube peapods by packing C60 molecules inside the open edge ducts of collapsed carbon nanotubes. C60 insertion is accomplished through a facile single-step solution-based process. Theoretical modeling is used to evaluate favorable low-energy structural configurations. Overfilling of the collapsed tubes allows infiltration of C60 over the full cross-section of the tubes and consequent partial or complete reinflation, yielding few-wall, large diameter cylindrical nanotubes packed with crystalline C60 solid cores.

  • 268.
    Barzegar, Hamid Reza
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics. Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sharifi, Tiva
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nitze, Florian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nitrogen Doping Mechanism in Small Diameter Single-Walled Carbon Nanotubes: Impact on Electronic Properties and Growth Selectivity2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 48, p. 25805-25816Article in journal (Refereed)
    Abstract [en]

    Nitrogen doping in carbon nanostructures has attracted interest for more than a decade, and recent implementation of such structures in energy conversion systems has boosted the interest even more. Despite numerous studies, the structural conformation and stability of nitrogen functionalities in small diameter single-walled carbon nanotubes (SWNTs), and the impact of these functionalities on the electronic and mechanical properties of the SWNTs, are incomplete. Here we report a detailed study on nitrogen doping in SWNTs with diameters in the range of 0.8?1.0 nm, with well-defined chirality. We show that the introduction of nitrogen in the carbon framework significantly alters the stability of certain tubes, opening for the possibility to selectively grow nitrogen-doped SWNTs with certain chirality and diameter. At low nitrogen concentration, pyridinic functionalities are readily incorporated and the tubular structure is well pertained. At higher concentrations, pyrrolic functionalities are formed, which leads to significant structural deformation of the nanotubes and hence a stop in growth of crystalline SWNTs. Raman spectroscopy is an important tool to understand guest atom doping and electronic charge transfer in SWNTs. By correlating the influence of defined nitrogen functionalities on the electronic properties of SWNTs with different chirality, we make precise interpretation of experimental Raman data. We show that the previous interpretation of the double-resonance G?-peak in many aspects is wrong and instead can be well-correlated to the type of nitrogen doping of SWNTs originating from the p- or n-doping nature of the nitrogen incorporation. Our results are supported by experimental and theoretical data.

  • 269.
    Bastos, Patricia Moreira
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The use of comprehensive two-dimensional gas chromatography and structure-activity modeling for screening and preliminary risk assessment of organic contaminants in soil, sediment, and surface water2012In: Journal of Soils and Sediments, ISSN 1439-0108, E-ISSN 1614-7480, Vol. 12, no 7, p. 1079-1088Article in journal (Refereed)
    Abstract [en]

    This article aims to investigate the use and benefits of using comprehensive two-dimensional gas chromatography (GC x GC) and structure-activity relationship modeling for screening and prioritization of organic contaminants in complex matrices. The benefit of applying comprehensive screening techniques to samples with high organic contaminant content is primarily that compounds with diverse physicochemical properties can be analyzed simultaneously. Here, a heavily contaminated industrial area was surveyed for organic pollutants by analyzing soil, sediment, and surface water samples. The hazard of the pollutants were ranked using SARs. The water samples were liquid-liquid extracted using dichloromethane and directly analyzed by GC x GC-time-of-flight mass spectrometry (GC x GC-TofMS). Soil and sediment samples were extracted with dichloromethane in an ultrasonic bath and subjected to gel permeation chromatography to eliminate lipids and humic matter. The low molecular weight fraction was then analyzed with GC x GC-TofMS. More than 10,000 components were found in each sample, of which ca. 300 individual compounds were unambiguously identified using the National Institute of Standards and Technology mass spectra library and authentic reference standards. Alkanes, polycyclic aromatic hydrocarbons, and phthalates were generally the most abundant and were found in all matrices. In contrast, chlorinated compounds such as chlorophenols, biphenyls, and chlorinated pesticides were only detected in samples from a few hotspot regions. The toxicities of the most frequently detected compounds and of the compounds detected at the highest concentrations in samples from hotspot regions were estimated by ecological structure-activity relationships. The ratio of the measured concentration to the predicted toxicity level was then calculated for each compound and used for an initial risk assessment in order to prioritize compounds for further transport and fate modeling, complementary measurements, and more advanced risk assessments. The advantage of using of GC x GC-TofMS for preliminary screenings of contaminated areas was evaluated at a polluted area in northern Sweden. The area was found to carry organic pollutants such as polyaromatic hydrocarbons, aliphatic hydrocarbons, polychlorinated biphenyls, phthalic compounds, and many chlorinated pesticides. Preliminary risk assessments indicate which compounds to use for subsequent remediation experiments based on their availability on the site or toxicity.

  • 270.
    Basu, Basudeb
    et al.
    Department of Chemistry, University of North Bengal, Darjeeling 734013, India.
    Das, Sajal
    Department of Chemistry, University of North Bengal, Darjeeling 734013, India.
    Das, Pralay
    Department of Chemistry, University of North Bengal, Darjeeling 734013, India.
    Mandal, Bablee
    Department of Chemistry, University of North Bengal, Darjeeling 734013, India.
    Banerjee, Dipanjan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Palladium supported on a Polyionic Resin as an efficient, ligand-free, and recyclable catalyst for Heck, Suzuki-Miyaura, and Sonogashira reactions2009In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, no 7, p. 1137-1146Article in journal (Refereed)
    Abstract [en]

    Polyionic Amberlite resin formate (ARF), derived from commercially available Amberlite resin chloride by simple rinsing with aqueous formic acid, could be soaked with palladium(0) from palladium salts, the formate counteranion being the reducing source. The resulting Amberlite resin formate supported with palladium(0), ARF-Pd, showed excellent catalytic activity in Heck, Suzuki­-Miyaura, and Sonogashira couplings with a range of substrates. The catalyst may be recovered easily and quantitatively without leaching and recycled; it was tested for five runs without any significant loss of activity.

  • 271. Basu, Basudeb
    et al.
    Paul, Susmita
    Kundu, Samir
    Byström, Emil
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Organic Polymeric Resins Embedded with Pd NPs: Newly Designed, Efficient and Chemoselective Catalyst for Reduction of Nitrobenzenes2017In: Current Organocatalysis, ISSN 2213-3372, Vol. 4, no 1, p. 48-61Article in journal (Refereed)
    Abstract [en]

    Background: Organic polymer supported palladium nanoparticles (NPs) are important for use as heterogeneous catalyst in various organic reactions. This works describes Pd Nps immobilized on to polystyrene-based ion-exchange resin surface for use as catalyst in the reduction of nitrobenzenes. The heterogeneous catalyst was found useful for hydrogenation of nitro group under both catalytic transfer hydrogenation (CTH) as well as by using molecular hydrogen (H2).

    Methods: The catalyst was prepared from Amberlite IRA 900 Cl after rinsing with formic acid (10%) and subsequent treatment with Na2PdCl4 in DMF. The resulting Pd Nps immobilized resins was designated as VersaCat Pd and used for CTH of nitrobenzenes in the presence of H-donors (sodium formate, formic acid, hydrazine hydrate) and also for hydrogenation with H2 gas. The catalyst was characterized by FT-IR, MAS-NMR, SEM, TEM and XPS and surface morphologies were studied before and after the reaction.

    Results: Hydrogenations of nitrobenzenes under CTH using different H-source and direct use of H2 gas were achieved successfully with good to excellent yields. Reactions were performed under mild conditions and high degree of chemoselectivity was also observed. The catalyst was recyclable, used for six consecutive runs with appreciable conversions and showed higher activity (> 3 times) in terms of metalcontent than commercially available Pd/C (10%) in the hydrogenation of nitrobenzenes using H2 gas. The TEM images showed that Pd Nps are evenly distributed with size 50-200 mm on polymeric matrices and there was no significant changes observed after the first catalytic run. However, considerable rupture of the polymeric surface occurred after six runs, as seen from SEM studies.

    Conclusion: The present study establishes high catalytic efficiency and chemoselectivity of the newly developed organic polystyrene-based resin-soaked Pd NPs (VersaCat Pd) in the reduction of nitrobenzenes. Both CTH and hydrogenation using H2 gas were successfully done. Interestingly, hydrazine hydrate offered excellent control over chemoselectivity under CTH conditions and allowed clean conversion from nitro to amine, while keeping a chloro substitutent unaffected. Hydrogenation using molecular H2 gave maximum TOF. Easy preparation, high efficacy, TOF, chemoselectivity, and versatile applications are notable features for this heterogeneous palladium catalyst (VersaCat Pd). These features are often required in chemical industries.

  • 272.
    Baumgärtner, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Influence of Iron Heavy-Ion Radiation on Biomarker Detectability: Determined by Raman-Spectroscopy of Cyanobacterial Carotenoids2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 273. Bavel, Bert van
    et al.
    Näf, C.
    Bergqvist, P. -A.
    Broman, D.
    Lundgren, Kjell
    Umeå University, Faculty of Science and Technology, Chemistry.
    Papakosta, O.
    Rolff, C.
    Strandberg, B.
    Zebühr, Y.
    Zook, D.
    Levels of PCBs in the aquatic environment of the Gulf of Bothnia: Benthic species and sediments1996In: Marine Pollution Bulletin, Vol. 32, p. 210-218Article in journal (Refereed)
  • 274. Bawuaha, Prince
    et al.
    Silfsten, Pertti
    Sarkar, Anjana
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kordas, Kristian
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Peiponen, Kai-Erik
    On the complex refractive index of N-doped TiO2 nanospheres and nanowires in the terahertz spectral region2013In: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 68, p. 241-245Article in journal (Refereed)
    Abstract [en]

    In this paper, the terahertz (THz) transmission measurement technique was applied to characterize titanium dioxide (TiO2) nanospheres and nanowires subjected to thermal treatments under various conditions. Differences in the spectral features of the nanospheres and nanowires were observed due to treatment and annealing of the samples in different gas atmospheres. The observations made can be explained based on the formation of new phonon bands and/or widening of the phonon bands due to polymorphism. A singly subtractive Kramers Kronig dispersion relation was utilized to estimate the frequency-dependent real refractive index of the various samples, having a priori unknown sample thickness, from the absorbance data.

  • 275.
    Baytekin, Mehmet
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Monoliths from Step-GrowthPolymerization Reactions2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 276.
    Becarevic, Vanja
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Generiskt utbyte på apotek iSverigeProblem och möjligheter med generisk substitution2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 277. Beck, Carole
    et al.
    Rodriguez-Vargas, José Manuel
    Boehler, Christian
    Robert, Isabelle
    Heyer, Vincent
    Hanini, Najat
    Gauthier, Laurent R.
    Tissier, Agnès
    Schreiber, Valérie
    Elofsson, Mikael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    San Martin, Bernardo Reina
    Dantzer, Françoise
    PARP3, a new therapeutic target to alter Rictor/mTORC2 signaling and tumor progression in BRCA1-associated cancers2019In: Cell Death and Differentiation, ISSN 1350-9047, E-ISSN 1476-5403, Vol. 26, no 9, p. 1615-1630Article in journal (Refereed)
    Abstract [en]

    PARP3 has been shown to be a key driver of TGF beta-induced epithelial-to-mesenchymal transition (EMT) and sternness in breast cancer cells, emerging as an attractive therapeutic target. Nevertheless, the therapeutic value of PARP3 inhibition has not yet been assessed. Here we investigated the impact of the absence of PARP3 or its inhibition on the tumorigenicity of BRCA1-proficient versus BRCA1-deficient breast cancer cell lines, focusing on the triple-negative breast cancer subtype (TNBC). We show that PARP3 knockdown exacerbates centrosome amplification and genome instability and reduces survival of BRCA1-deficient TNBC cells. Furthermore, we engineered PARP3(-/- )BRCA1-deficient or BRCA1-proficient TNBC cell lines using the CRISPR/nCas9(D10A) gene editing technology and demonstrate that the absence of PARP3 selectively suppresses the growth, survival and in vivo tumorigenicity of BRCA1-deficient TNBC cells, mechanistically via effects associated with an altered Rictor/mTORC2 signaling complex resulting from enhanced ubiquitination of Rictor. Accordingly, PARP3 interacts with and ADP-ribosylates GSK3 beta, a positive regulator of Rictor ubiquitination and degradation. Importantly, these phenotypes were rescued by re-expression of a wild-type PARP3 but not by a catalytic mutant, demonstrating the importance of PARP3's catalytic activity. Accordingly, reduced survival and compromised Rictor/mTORC2 signaling were also observed using a cell-permeable PARP3-specific inhibitor. We conclude that PARP3 and BRCA1 are synthetic lethal and that targeting PARP3's catalytic activity is a promising therapeutic strategy for BRCA1-associated cancers via the Rictor/mTORC2 signaling pathway.

  • 278.
    Beckmann, Katrin
    et al.
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Badger, Murray Ronald
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    Wydrzynski, Tom
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    Hillier, Warwick
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    On-line mass spectrometry: membrane inlet sampling2009In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 102, no 2-3, p. 511-522Article in journal (Refereed)
    Abstract [en]

    Significant insights into plant photosynthesis and respiration have been achieved using membrane inlet mass spectrometry (MIMS) for the analysis of stable isotope distribution of gases. The MIMS approach is based on using a gas permeable membrane to enable the entry of gas molecules into the mass spectrometer source. This is a simple yet durable approach for the analysis of volatile gases, particularly atmospheric gases. The MIMS technique strongly lends itself to the study of reaction flux where isotopic labeling is employed to differentiate two competing processes; i.e., O2 evolution versus O2 uptake reactions from PSII or terminal oxidase/rubisco reactions. Such investigations have been used for in vitro studies of whole leaves and isolated cells. The MIMS approach is also able to follow rates of isotopic exchange, which is useful for obtaining chemical exchange rates. These types of measurements have been employed for oxygen ligand exchange in PSII and to discern reaction rates of the carbonic anhydrase reactions. Recent developments have also engaged MIMS for online isotopic fractionation and for the study of reactions in inorganic systems that are capable of water splitting or H2 generation. The simplicity of the sampling approach coupled to the high sensitivity of modern instrumentation is a reason for the growing applicability of this technique for a range of problems in plant photosynthesis and respiration. This review offers some insights into the sampling approaches and the experiments that have been conducted with MIMS.

  • 279. Beckmann, Katrin
    et al.
    Uchtenhagen, Hannes
    Berggren, Gustav
    Anderlund, Magnus F
    Thapper, Anders
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Chemistry.
    Styring Stenbjörn,,
    Kurz Philipp,
    Formation of stoichiometrically 18O-labelled oxygen from the oxidation of 18O-enriched water mediated by a dinuclear manganese complex-a mass spectrometry and EPR study2008In: Energy & Environmental Science, Vol. 1, p. 668-76Article in journal (Refereed)
    Abstract [en]

    Oxygen formation was detected for the oxidations of various multinuclear manganese complexes by oxone (HSO5-) in aqueous solution. To determine to what extent water was the source of the evolved O2, H218O isotope-labelling experiments coupled with membrane inlet mass spectrometry (MIMS) were carried out. We discovered that during the reaction of oxone with [Mn2(OAc)2(bpmp)]+ (1), stoichiometrically labelled oxygen (18O2) was formed. This is the first example of a homogeneous reaction mediated by a synthetic manganese complex where the addition of a strong chemical oxidant yields 18O2 with labelling percentages matching the theoretically expected values for the case of both O-atoms originating from water. Experiments using lead acetate as an alternative oxidant supported this finding. A detailed investigation of the reaction by EPR spectroscopy, MIMS and Clark-type oxygen detection enabled us to propose potential reaction pathways.

  • 280. Beckwith-Hall, BM
    et al.
    Brindle, JT
    Barton, RH
    Coen, M
    Holmes, E
    Nicholson, JK
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Chemistry.
    Application of orthogonal signal correction to minimise the effects of physical and biological variation in high resolution 1H NMR spectra of biofluids2002In: Analyst, Vol. 127, no 10, p. 1283-8Article in journal (Refereed)
    Abstract [en]

    1H nuclear magnetic resonance (NMR)-based metabonomics is a well-established technique used to analyse and interpret complex multiparametric metabolic data, and has a wide number of applications in the development of pharmaceuticals. However, interpretation of biological data can be confounded by extraneous variation in the data such as fluctuations in either experimental conditions or in physiological status. Here we have shown the novel application of a data filtering method, orthogonal signal correction (OSC), to biofluid NMR data to minimise the influence of inter- and intra-spectrometer variation during data acquisition, and also to minimise innate physiological variation. The removal of orthogonal variation exposed features of interest in the NMR data and facilitated interpretation of the derived multivariate models. Furthermore, analysis of the orthogonal variation provided an explanation of the systematic analytical/biological changes responsible for confounding the original NMR data.

  • 281. Behravesh, Erfan
    et al.
    Kumar, Narendra
    Balme, Quentin
    Roine, Jorma
    Salonen, Jarno
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Process Chemistry Centre, Åbo Akademi University, FI-20500 Turku/Åbo, Finland.
    Peurla, Markus
    Aho, Atte
    Eränen, Kari
    Murzin, Dmitry Yu.
    Salmi, Tapio
    Synthesis and characterization of Au nano particles supported catalysts for partial oxidation of ethanol: Influence of solution pH, Au nanoparticle size, support structure and acidity2017In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 353, p. 223-238Article in journal (Refereed)
    Abstract [en]

    Partial oxidation of ethanol to acetaldehyde was carried out over gold catalysts supported on various oxides and zeolites by deposition precipitation. The special focus of this work was on the influence of H-Y zeolite surface charge on Au cluster size and loading linking it to activity and selectivity in ethanol oxidation and comparing with other studied catalysts. The catalysts were characterized by nitrogen physisorption, transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDXA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and zeta potential measurements. pH of the solution governed the Au NPs size within the range of 5.8–13.2 nm with less negatively charged surfaces leading to formation of smaller clusters. Au loading on H-Y zeolite with silica to alumina ratio of 80 was increased by raising the pH. In fact, H-Y-12 and H-Beta-25 were selective towards diethyl ether while acetaldehyde was the prevalent product on less acidic H-Y-80. The results demonstrated strong dependency of the catalytic activity on the Au cluster size. Namely turn over frequency (TOF) decreased with an increase in metal size from 6.3 to 9.3 nm on H-Y-80. Selectivity towards acetaldehyde and ethyl acetate did not change significantly on H-Y-80 within 6.3–9.3 nm Au particle size range. On Al2O3 support, however, selectivity towards acetaldehyde increased considerably upon diminishing Au average particle size from 3.7 to 2.1 nm.

  • 282.
    Behren, Sandra
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Westerlind, Ulrika
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Glycopeptides and -Mimetics to Detect, Monitor and Inhibit Bacterial and Viral Infections: Recent Advances and Perspectives2019In: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 24, no 6, article id 1004Article, review/survey (Refereed)
    Abstract [en]

    The initial contact of pathogens with host cells is usually mediated by their adhesion to glycan structures present on the cell surface in order to enable infection. Furthermore, glycans play important roles in the modulation of the host immune responses to infection. Understanding the carbohydrate-pathogen interactions are of importance for the development of novel and efficient strategies to either prevent, or interfere with pathogenic infection. Synthetic glycopeptides and mimetics thereof are capable of imitating the multivalent display of carbohydrates at the cell surface, which have become an important objective of research over the last decade. Glycopeptide based constructs may function as vaccines or anti-adhesive agents that interfere with the ability of pathogens to adhere to the host cell glycans and thus possess the potential to improve or replace treatments that suffer from resistance. Additionally, synthetic glycopeptides are used as tools for epitope mapping of antibodies directed against structures present on various pathogens and have become important to improve serodiagnostic methods and to develop novel epitope-based vaccines. This review will provide an overview of the most recent advances in the synthesis and application of glycopeptides and glycopeptide mimetics exhibiting a peptide-like backbone in glycobiology.

  • 283. Beijer, Kristina
    et al.
    Bjorlenius, Berndt
    Shaik, Siraz
    Lindberg, Richard H.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Brunstrom, Bjorn
    Brandt, Ingvar
    Removal of pharmaceuticals and unspecified contaminants in sewage treatment effluents by activated carbon filtration and ozonation: Evaluation using biomarker responses and chemical analysis2017In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 176, p. 342-351Article in journal (Refereed)
    Abstract [en]

    Traces of active pharmaceutical ingredients (APIs) and other chemicals are demonstrated in effluents from sewage treatment plants (STPs) and they may affect quality of surface water and eventually drinking water. Treatment of effluents with granular activated carbon (GAC) or ozone to improve removal of APIs and other contaminants was evaluated at two Swedish STPs, Kappala and Uppsala (88 and 103 APIs analyzed). Biomarker responses in rainbow trout exposed to regular and additionally treated effluents were determined. GAC and ozone treatment removed 87-95% of the total concentrations of APIs detected. In Kappala, GAC removed 20 and ozonation (7 g O-3/m(3)) 21 of 24 APIs detected in regular effluent. In Uppsala, GAC removed 25 and ozonation (5.4 g O-3/m(3)) 15 of 25 APIs detected in effluent. GAC and ozonation also reduced biomarker responses caused by unidentified pollutants in STP effluent water. Elevated ethoxyresorufin-O-deethylase (EROD) activity in gills was observed in fish exposed to effluent in both STPs. Gene expression analysis carried out in Kappala showed increased concentrations of cytochrome P450 (CYP1A5 and CYP1C3) transcripts in gills and of CYP1As in liver of fish exposed to effluent. In fish exposed to GAC- or ozone-treated effluent water, gill EROD activity and expression of CYP1As and CYP1C3 in gills and liver were generally equal to or below levels in fish held in tap water. The joint application of chemical analysis and sensitive biomarkers proved useful for evaluating contaminant removal in STPs with new technologies.

  • 284. Belorizky, Elie
    et al.
    Fries, Pascal H
    Helm, Lothar
    Kowalewski, Jozef
    Kruk, Danuta
    Sharp, Robert R
    Westlund, Per-Olof
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Comparison of different methods for calculating the paramagnetic relaxation enhancement of nuclear spins as a function of the magnetic field2008In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 128, no 5, article id 052315Article in journal (Refereed)
    Abstract [en]

    The enhancement of the spin-lattice relaxation rate for nuclear spins in a ligand bound to a paramagnetic metal ion [known as the paramagnetic relaxation enhancement (PRE)] arises primarily through the dipole-dipole (DD) interaction between the nuclear spins and the electron spins. In solution, the DD interaction is modulated mostly by reorientation of the nuclear spin-electron spin axis and by electron spin relaxation. Calculations of the PRE are in general complicated, mainly because the electron spin interacts so strongly with the other degrees of freedom that its relaxation cannot be described by second-order perturbation theory or the Redfield theory. Three approaches to resolve this problem exist in the literature: The so-called slow-motion theory, originating from Swedish groups [Benetis et al., Mol. Phys. 48, 329 (1983); Kowalewski et al., Adv. Inorg. Chem. 57, (2005); Larsson et al., J. Chem. Phys. 101, 1116 (1994); T. Nilsson et al., J. Magn. Reson. 154, 269 (2002)] and two different methods based on simulations of the dynamics of electron spin in time domain, developed in Grenoble [Fries and Belorizky, J. Chem. Phys. 126, 204503 (2007); Rast et al., ibid. 115, 7554 (2001)] and Ann Arbor [Abernathy and Sharp, J. Chem. Phys. 106, 9032 (1997); Schaefle and Sharp, ibid. 121, 5387 (2004); Schaefle and Sharp, J. Magn. Reson. 176, 160 (2005)], respectively. In this paper, we report a numerical comparison of the three methods for a large variety of parameter sets, meant to correspond to large and small complexes of gadolinium(III) and of nickel(II). It is found that the agreement between the Swedish and the Grenoble approaches is very good for practically all parameter sets, while the predictions of the Ann Arbor model are similar in a number of the calculations but deviate significantly in others, reflecting in part differences in the treatment of electron spin relaxation. The origins of the discrepancies are discussed briefly.

  • 285.
    Benedict, Catherine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Geisler, Matt
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Huner, Norman
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Consensus by democracy. Using meta-analyses of microarray and genomic data to model the cold acclimation signaling pathway in Arabidopsis.2006In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 141, no 4, p. 1219-1232Article in journal (Refereed)
    Abstract [en]

    The whole-genome response of Arabidopsis (Arabidopsis thaliana) exposed to different types and durations of abiotic stress has now been described by a wealth of publicly available microarray data. When combined with studies of how gene expression is affected in mutant and transgenic Arabidopsis with altered ability to transduce the low temperature signal, these data can be used to test the interactions between various low temperature-associated transcription factors and their regulons. We quantized a collection of Affymetrix microarray data so that each gene in a particular regulon could vote on whether a cis-element found in its promoter conferred induction (+1), repression (–1), or no transcriptional change (0) during cold stress. By statistically comparing these election results with the voting behavior of all genes on the same gene chip, we verified the bioactivity of novel cis-elements and defined whether they were inductive or repressive. Using in silico mutagenesis we identified functional binding consensus variants for the transcription factors studied. Our results suggest that the previously identified ICEr1 (induction of CBF expression region 1) consensus does not correlate with cold gene induction, while the ICEr3/ICEr4 consensuses identified using our algorithms are present in regulons of genes that were induced coordinate with observed ICE1 transcript accumulation and temporally preceding genes containing the dehydration response element. Statistical analysis of overlap and cis-element enrichment in the ICE1, CBF2, ZAT12, HOS9, and PHYA regulons enabled us to construct a regulatory network supported by multiple lines of evidence that can be used for future hypothesis testing.

  • 286.
    Bengt-Harald Jonsson, Göran Aronsson
    Umeå University, Faculty of Science and Technology, Chemistry.
    Remarkably slow folding of a small protein1997In: FEBS Letters, Vol. 411, p. 359-364Article in journal (Refereed)
  • 287. Bengtsson, Anders A.
    et al.
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wuttge, Dirk M.
    Sturfelt, Gunnar
    Theander, Elke
    Donten, Magdalena
    Moritz, Thomas
    Sennbro, Carl-Johan
    Torell, Frida
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lood, Christian
    Surowiec, Izabella
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Rännar, Stefan
    Lundstedt, Torbjörn
    Metabolic Profiling of Systemic Lupus Erythematosus and Comparison with Primary Sjögren’s Syndrome and Systemic Sclerosis2016In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 7, article id e0159384Article in journal (Refereed)
    Abstract [en]

    Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease which can affect most organ systems including skin, joints and the kidney. Clinically, SLE is a heterogeneous disease and shares features of several other rheumatic diseases, in particular primary Sjögrens syndrome (pSS) and systemic sclerosis (SSc), why it is difficult to diag- nose The pathogenesis of SLE is not completely understood, partly due to the heterogeneity of the disease. This study demonstrates that metabolomics can be used as a tool for improved diagnosis of SLE compared to other similar autoimmune diseases. We observed differences in metabolic profiles with a classification specificity above 67% in the comparison of SLE with pSS, SSc and a matched group of healthy individuals. Selected metabolites were also significantly different between studied diseases. Biochemical pathway analysis was conducted to gain understanding of underlying pathways involved in the SLE pathogenesis. We found an increased oxidative activity in SLE, supported by increased xanthine oxidase activity and an increased turnover in the urea cycle. The most discriminatory metabolite observed was tryptophan, with decreased levels in SLE patients compared to control groups. Changes of tryptophan levels were related to changes in the activity of the aromatic amino acid decarboxylase (AADC) and/or to activation of the kynurenine pathway. 

  • 288.
    Bengtsson, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Synthesis of substituted Ring-Fused 2-Pyridones and applications in chemical biology2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Antibiotics have been extensively used to treat bacterial infections since Alexander Fleming’s discovery of penicillin 1928. Disease causing microbes that have become resistant to antibiotic drug therapy are an increasing public health problem. According to the world health organization (WHO) there are about 440 000 new cases of multidrug-resistant tuberculosis emerging annually, causing at least 150 000 deaths. Consequently there is an immense need to develop new types of compounds with new modes of action for the treatment of bacterial infections.

    Presented herein is a class of antibacterial ring-fused 2-pyridones, which exhibit inhibitory effects against both the pili assembly system in uropathogenic Escherichia coli (UPEC), named the chaperone usher pathway, as well as polymerization of the major curli subunit protein CsgA, into a functional amyloid fibre. A pilus is an organelle that is vital for the bacteria to adhere to and infect host cells, as well as establish biofilms. Inhibition of the chaperone usher pathway disables the pili assembly machinery, and consequently renders the bacteria avirulent.

    The focus of this work has been to develop synthetic strategies to more efficiently alter the substitution pattern of the aforementioned ring-fused 2-pyridones. In addition, asymmetric routes to enantiomerically enriched key compounds and routes to compounds containing BODIPY and coumarin fluorophores as tools to study bacterial virulence mechanisms have been developed. Several of the new compounds have successfully been evaluated as antibacterial agents. In parallel with this research, manipulations of the core structure to create new heterocycle based central fragments for applications in medicinal chemistry have also been performed.   

  • 289.
    Bengtsson, Christoffer
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    A Selective Intramolecular 5-exo-dig or 6-endo-dig Cyclization en Route to 2-Furanone or 2-Pyrone Containing Tricyclic Scaffolds2011In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 76, no 23, p. 9817-9825Article in journal (Refereed)
    Abstract [en]

    Ringfused bicyclic 2-pyridones exhibit interesting biological properties against pili assembly in uropathogenic E. coli1 as well as curli formation2. In the strive for new ring-fused central fragments highly selective synthetic routes to the 2-furanone or 2-pyrone containing tricyclic scaffolds 1 and 2 have been developed.

  • 290.
    Bengtsson, Christoffer
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Chemistry.
    Regioselective Halogenations and Subsequent Suzuki-Miyaura Coupling onto Bicyclic 2-Pyridones2010In: The Journal of organic chemistry, ISSN 1520-6904, Vol. 75, no 3, p. 972-5Article in journal (Refereed)
    Abstract [en]

    A selective synthesis of 6-bromo-8-iodo dihydro thiazolo ring-fused 2-pyridones is described. These halogenated 2-pyridones are selectively arylated by sequential Suzuki-Miyaura couplings. This approach can advantageously be used to synthesize focused libraries of substituted ring-fused 2-pyridones, a class of compounds with novel antibacterial properties.

  • 291.
    Bengtsson, Christoffer
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Synthesis of triazole functionalized bicyclic 2-pyridones2011In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 242, p. 247-ORGN-Article in journal (Refereed)
  • 292. Bengtsson, Christoffer
    et al.
    Chorell, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Krishnan, Syam
    Banchelin, Thomas Sainte-Luce
    Gustafson, Karl
    Das, Pralay
    Sinha, Arun K
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Synthesis of a bromomethyl substituted bicyclic 2-pyridone scaffold2013In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 245Article in journal (Refereed)
  • 293.
    Bengtsson, Christoffer
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindgren, Anders EG
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Uvell, Hanna
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Design, synthesis and evaluation of triazole functionalized Ring-fused 2-pyridones as antibacterial agents2012In: European Journal of Medicinal Chemistry, ISSN 0223-5234, E-ISSN 1768-3254, Vol. 54, p. 637-646Article in journal (Refereed)
    Abstract [en]

    Antibacterial resistance is today a worldwide problem and the demand for new classes of antibacterial agents with new mode of action is enormous. In the strive for new antibacterial agents that inhibit pilus assembly, an important virulence factor, routes to introduce triazoles in position 8 and 2 of ring-fused bicyclic 2-pyridones have been developed. This was made via Sonogashira couplings followed by Huisgen 1,3-dipolar cycloadditions. The method development made it possible to introduce a diverse series of substituted triazoles and their antibacterial properties were tested in a whole cell pili-dependent biofilm assay. Most of the twenty four candidates tested showed low to no activity but interestingly three compounds, one 8-substituted and two 2-substituted, showed promising activities with EC50’s between 9-50 μM.

  • 294.
    Bengtsson, Christoffer
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nelander, Hanna
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Asymmetric Synthesis of 2,4,5-Trisubstituted (2)-Thiazolines2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 30, p. 9916-9922Article in journal (Refereed)
    Abstract [en]

    (2)-Thiazolines are interesting heterocycles that display a wide variety of biological characteristics. They are also common in chiral ligands used for asymmetric syntheses and as synthetic intermediates. Herein, we present asymmetric routes to 2,4,5-trisubstituted (2)-thiazolines. These (2)-thiazolines were synthesized from readily accessible/commercially available ,-unsaturated methyl esters through a Sharpless asymmetric dihydroxylation and an ON acyl migration reaction as key steps. The final products were obtained in good yields with up to 97% enantiomeric excess.

  • 295.
    Bengtsson, Åsa
    Umeå University, Faculty of Science and Technology, Chemistry.
    Solubility and Surface Complexation Studies of Apatites2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Apatites are a diverse class of phosphate minerals that are important in a great variety of natural and industrial processes. They are, for example, used as raw material in fertiliser production and in the remediation of metal-contaminated soils. Hydroxyapatite Ca5(PO4)3OH, (HAP) and fluorapatite Ca5(PO4)3F, (FAP) are similar to the biological apatite that is the main constituent of mammalian bone and teeth, and they are therefore promising materials for artificial bone and tooth implants.

    This thesis is a summary of four papers with focus on dissolution and surface complexation reactions of HAP and FAP in the absence and presence of both organic ligands and the natural and commonly occurring iron oxide goethite (α-FeOOH).

    The dissolution and surface complexation of HAP and FAP was investigated with a combination of different techniques. Potentiometric acid/base titrations and batch experiments were combined with X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) Spectroscopy to generate dissolution and surface complexation models for both apatites. The results from these studies showed that both apatites form surface layers that are different from their bulk compositions when equilibrated in aqueous solutions. The modeling efforts predicted speciation of these surfaces as well as the concentration of the dissolution products in the solution.

    The interaction between organic ligands and the apatite surfaces was also investigated and the results from this study show that the organic ligands form outer-sphere complexes on the apatite surfaces over a large pH interval, and that this adsorption enhances the dissolution of apatites.

    The presence of goethite also enhances the dissolution of FAP as it acts as a sink for the phosphate released from FAP. Phase transformation in this system was detected using ATR-FTIR as the phosphate adsorbed to the goethite surface precipitates as FePO4 (s) after approximately 15 days of reaction time. This changes the speciation, and possibly also the bioavailability of phosphate in this two-mineral system.

  • 296.
    Bengtsson, Åsa
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Lindegren, Malin
    Umeå University, Faculty of Science and Technology, Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Chemistry.
    Dissolution, adsorption and phase transformation in the fluorapatite–goethite system2007In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 22, no 9, p. 2016-2028Article in journal (Refereed)
    Abstract [en]

    An aqueous system containing fluorapatite (Ca5(PO4)3F), (FAP) and varying amounts of goethite (α-FeOOH) has been investigated. Batch experiments and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were used to monitor the dissolution products of FAP, as well as the adsorption, and phase transformation of phosphate at the goethite surface over a period of 129 days. The results show that the presence of goethite increases dissolution of FAP, mainly due to the high affinity of phosphate for the goethite surface: Besides monitoring the pH changes associated with this reaction, the concentrations of Ca2+ and fluoride were determined. Furthermore, the amount of phosphate adsorbed was quantified from ATR-FTIR spectra. In addition to adsorbed phosphate, phase transformations of goethite into a Fe phosphate phase (FePO4(s)) are seen in the samples with relatively high phosphate to goethite ratios (excess phosphate to available surface sites) equilibrated for 15–129 days.

    An equilibrium model that takes into account (i) FAP dissolution, (ii) solution complexation, (iii) surface complexation of phosphate species onto goethite and (iv) possible phase transformation Ca5(PO4)3F–CaF2 and FeOOH–FePO4 was designed. This model was found to be in very good agreement with experimental observations and could thus be used to give qualitative and quantitative information about goethite promoted dissolution of FAP under other pH conditions than those studied in the present work.

  • 297.
    Bengtsson, Åsa
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Lövgren, Lars
    Umeå University, Faculty of Science and Technology, Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Chemistry.
    A comparative study of the dissolution of hydroxyapatite and fluorapatite in the absence and presence of organic ligands2005In: GEOCHIMICA ET COSMOCHIMICA ACTA 69 (10): A68-A68 Suppl. S, MAY 2005, ISSN 0016-7037, Vol. 69, no 10, p. A68-Article in journal (Other academic)
  • 298.
    Bengtsson, Åsa
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Chemistry.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Chemistry.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Chemistry.
    Lövgren, Lars
    Umeå University, Faculty of Science and Technology, Chemistry.
    A kinetic and spectroscopic study of fluorapatite dissolution2004Conference paper (Other academic)
  • 299.
    Bengtsson, Åsa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Phase Transformations, Ion-Exchange, Adsorption, and Dissolution Processes in Aquatic Fluorapatite Systems2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 4, p. 2355-2362Article in journal (Refereed)
    Abstract [en]

    A synthetic fluorapatite was prepared that undergoes a phase transformation generated during a dialysis step. A surface layer with the composition Ca9(HPO4)2(PO4)4F2 is formed, which is suggested to form as one calcium atom is replaced by two protons. A surface complexation model, based upon XPS measurements, potentiometric titration data, batch experiments, and zeta-potential measurements was presented. The CaOH and OPO3H2 sites were assumed to have similar protolytic properties as in a corresponding nonstoichiometric HAP (Ca8.4(HPO4)1.6(PO4)4.4(OH)0.4) system. Besides a determination of the solubility product of Ca9(HPO4)2(PO4)4F2, two additional surface complexation reactions were introduced; one that accounts for a F/OH ion exchange reaction, resulting in the release of quite high fluoride concentrations (∼1 mM) that turned out to be dependent on the surface area of the particles. Furthermore, to explain the lowering of pHiep from around 8 in nonstoichiometric HAP suspensions to about 5.7 in FAP suspensions, a reaction that lowers the surface charge due to the readsorption of fluoride ions to the positively charged Ca sites was introduced: ≡CaOH2+ + F− ⇋ ≡CaF + H2O. The resulting model also agrees with predictions based upon XPS and ATR-FTIR observations claiming the formation of CaF2(s) in the most acidic pH range.

  • 300.
    Bengtsson, Åsa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    A solubility and surface complexation study of a non-stoichiometric hydroxyapatite2009In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 73, no 2, p. 257-267Article in journal (Refereed)
    Abstract [en]

    The dissolution and surface complexation of a non-stoichiometric hydroxyapatite (Ca8.4(HPO4)1.6(PO4)4.4(OH)0.4), (HAP) was studied in the pH range 3.5 – 10.5, at 25 ºC in 0.1 M Na(Cl). The results from well-equilibrated batch experiments, potentiometric titrations, and zeta-potential measurements were combined with information provided by Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The information from the analyses was used to design an equilibration model that takes in to account dissolution, surface potential, solution and surface complexation, as well as possible phase transformations. The results from the XPS measurements clearly show that the surface of the mineral has a different composition than the bulk and that the Ca/P ratio of the surface layer is 1.4 ± 0.1. This ratio was also found in solution in the batches equilibrated at low pH where the dominating reaction is dissolution. In the batches equilibrated at near neutral pH values, however, the Ca/P ratio in solution attains values as high as 25, which is due to re-adsorption of phosphate ions to the HAP surface. The total concentration of protons as well as the total concentration of dissolved calcium and phosphate in solution were used to calculate a model for the dissolution and surface complexation of HAP. The constant capacitance model was applied in designing the following surface complexation model.

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