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Browsing Artikler, rapporter og annet (kjemi) by Author
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Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)[+][-]
Abstract: Dedicated to the memory of Björn Roos (1937–2010), one of the fathers of modern multiconfigurational quantum chemistry, who also cared deeply about chemical applications, and a fun and inspiring friend to countless theoretically oriented chemists. URI: http://hdl.handle.net/10037/4086 File(s) in this item: 1
article.pdf (132.1Kb) -
Hansen, Geir Åsmund; Ahmad, Rafi; Hjerde, erik; Fenton, Christopher Graham; Willassen, Nils Peder; Haugen, Peik (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: Spot 42 was discovered in Escherichia coli nearly 40 years ago as an abundant, small and unstable RNA. Its biological role has remained obscure until recently, and is today implicated in having broader roles in the central and secondary metabolism. Spot 42 is encoded by the spf gene. The gene is ubiquitous in the Vibrionaceae family of gamma-proteobacteria. One member of this family, Aliivibrio salmonicida, causes cold-water vibriosis in farmed Atlantic salmon. Its genome encodes Spot 42 with 84% identity to E. coli Spot 42. We generated a A. salmonicida spf deletion mutant. We then used microarray and Northern blot analyses to monitor global effects on the transcriptome in order to provide insights into the biological roles of Spot 42 in this bacterium. In the presence of glucose, we found a surprisingly large number of ≥ 2X differentially expressed genes, and several major cellular processes were affected. A gene encoding a pirin-like protein showed an on/off expression pattern in the presence/absence of Spot 42, which suggests that Spot 42 plays a key regulatory role in the central metabolism by regulating the switch between fermentation and respiration. Interestingly, we discovered an sRNA named VSsrna24, which is encoded immediately downstream of spf. This new sRNA has an expression pattern opposite to that of Spot 42, and its expression is repressed by glucose. We hypothesize that Spot 42 plays a key role in the central metabolism, in part by regulating the pyruvat dehydrogenase enzyme complex via pirin. Description: The submitted manuscript version of this article is part of Geir Åsmund Hansen's doctoral thesis, which is available in Munin at http://hdl.handle.net/10037/3675 URI: http://hdl.handle.net/10037/4332 File(s) in this item: 1
article.pdf (2.491Mb) -
Hansen, Lars Kr; Perlovich, German; Bauer-Brandl, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2006)[+][-]
Abstract: [Erratum to document cited in CA140:010932] URI: http://hdl.handle.net/10037/3174 File(s) in this item: 1
article.pdf (133.1Kb) -
Hansen, Lars Kr; Perlovich, German; Bauer-Brandl, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)[+][-]
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Hansen, Lars Kr; Perlovich, German; Bauer-Brandl, Annette D (Journal article; Tidsskriftartikkel; Peer reviewed, 2006)[+][-]
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Schaper, KJ; Hansen, Lars Kr; Perlovich, German; Bauer-Brandl, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)[+][-]
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Hansen, Lars Kr; Tjosas, F; Tjosås, Freddy; Fiksdahl, A (Journal article; Tidsskriftartikkel; Peer reviewed, 2006)[+][-]
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Hansen, Lars Kr; Perlovich, German; Bauer-Brandl, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)[+][-]
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Hansen, Lars Kr; Stockmann, V; Fiksdahl, A (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)[+][-]
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Hansen, Lars Kr; Stockmann, V; Fiksdahl, A (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)[+][-]
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Hansen, Lars Kr; Perlovich, German; Bauer-Brandl, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)[+][-]
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Hansen, Lars Kr; Perlovich, German; Bauer-Brandl, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2006)[+][-]
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Kahlke, Tim; Thorvaldsen, Steinar (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: Cold-adaptation strategies have been studied in multiple psychrophilic organisms, especially for psychrophilic enzymes. Decreased enzyme activity caused by low temperatures as well as a higher viscosity of the aqueous environment require certain adaptations to the metabolic machinery of the cell. In addition to this, low temperature has deleterious effects on the lipid bilayer of bacterial membranes and therefore might also affect the embedded membrane proteins. Little is known about the adaptation of membrane proteins to stresses of the cold. In this study we investigate a set of 66 membrane proteins from the core genome of the bacterial family Vibrionaceae to identify general characteristics that discern psychrophilic and mesophilic membrane proteins. Bioinformatical and statistical methods were used to analyze the alignments of the three temperature groups mesophilic, intermediate and psychrophilic. Surprisingly, our results show little or no adaptation to low temperature for those parts of the proteins that are predicted to be inside the membrane. However, changes in amino acid composition and hydrophobicity are found for complete sequences and sequence parts outside the lipid bilayer. Among others, the results presented here indicate a preference for helix-breaking and destabilizing amino acids Ile, Asp and Thr and an avoidance of the helix-forming amino acid Ala in the amino acid composition of psychrophilic membrane proteins. Furthermore, we identified a lower overall hydrophobicity of psychrophilic membrane proteins in comparison to their mesophilic homologs. These results support the stability-flexibility hypothesis and link the cold-adaptation strategies of membrane proteins to those of loop regions of psychrophilic enzymes. URI: http://hdl.handle.net/10037/4922 File(s) in this item: 1
article.pdf (231.9Kb) -
Kahlke, Tim; Goesmann, Alexander; Hjerde, Erik; Willassen, Nils Peder; Haugen, Peik (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: The criteria for defining bacterial species and even the concept of bacterial species itself are under debate, and the discussion is apparently intensifying as more genome sequence data is becoming available. However, it is still unclear how the new advances in genomics should be used most efficiently to address this question. In this study we identify genes that are common to any group of genomes in our dataset, to determine whether genes specific to a particular taxon exist and to investigate their potential role in adaptation of bacteria to their specific niche. These genes were named unique core genes. Additionally, we investigate the existence and importance of unique core genes that are found in isolates of phylogenetically non-coherent groups. These groups of isolates, that share a genetic feature without sharing a closest common ancestor, are termed genophyletic groups. The bacterial family Vibrionaceae was used as the model, and we compiled and compared genome sequences of 64 different isolates. Using the software orthoMCL we determined clusters of homologous genes among the investigated genome sequences. We used multilocus sequence analysis to build a host phylogeny and mapped the numbers of unique core genes of all distinct groups of isolates onto the tree. The results show that unique core genes are more likely to be found in monophyletic groups of isolates. Genophyletic groups of isolates, in contrast, are less common especially for large groups of isolate. The subsequent annotation of unique core genes that are present in genophyletic groups indicate a high degree of horizontally transferred genes. Finally, the annotation of the unique core genes of Vibrio cholerae revealed genes involved in aerotaxis and biosynthesis of the iron-chelator vibriobactin. The presented work indicates that genes specific for any taxon inside the bacterial family Vibrionaceae exist. These unique core genes encode conserved metabolic functions that can shed light on the adaptation of a species to its ecological niche. Additionally, our study suggests that unique core genes can be used to aid classification of bacteria and contribute to a bacterial species definition on a genomic level. Furthermore, these genes may be of importance in clinical diagnostics and drug development. URI: http://hdl.handle.net/10037/4905 File(s) in this item: 1
article.pdf (709.4Kb) -
Kostenko, Nataliya; Gottfriedsen, Jochen; Hilfert, Liane; Edelmann, Frank T (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: A synthetic route to potentially biocidal silsesquioxanes functionalized by quaternary pyridinium functionalities has been developed. N-Alkylation reactions of the precursor compounds 4-(2-(trimethoxysilyl)ethyl)-pyridine (5) and 4-(2-trichloro-silylethyl)pyridine (6) with iodomethane, n-hexylbromide, and n-hexadecylbromide cleanly afforded the corresponding N-alkylpyridinium salts (7–10). The synthesis of a 4-(2-ethyl)pyridine POSS derivative (2) was achieved by capping of the silsesquioxane trisilanol Cy7Si7O9(OH)3 (1) via two different preparative routes. Attempts to use compound 2 as precursor for quaternary pyridinium salt-functionalized POSS derivatives were met with only partial success. Only the reaction with iodomethane cleanly afforded the new N-methylpyridinium salt 12 in high yield, whereas n-hexylbromide and n-hexadecylbromide failed to react with 2 even under forcing conditions. URI: http://hdl.handle.net/10037/4923 File(s) in this item: 1
article.pdf (919.7Kb) -
Langner, J.; Engardt, M.; Baklanov, A.; Christensen, J. H.; Gauss, Michael; Geels, Camila; Hedegaard, G.B.; Nuterman, R.; Simpson, D.; Soares, J; Sofiev, M; Wind, Peter; Zakey, A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: The impact of climate change on surface ozone over Europe was studied using four offline regional chemistry transport models (CTMs) and one online regional integrated climate-chemistry model (CCM), driven by the same global projection of future climate under the SRES A1B scenario. Anthropogenic emissions of ozone precursors from RCP4.5 for year 2000 were used for simulations of both present and future periods in order to isolate the impact of climate change and to assess the robustness of the results across the different models. The sensitivity of the simulated surface ozone to changes in climate between the periods 2000–2009 and 2040–2049 differs by a factor of two between the models, but the general pattern of change with an increase in southern Europe is similar across different models. Emissions of isoprene differ substantially between different CTMs ranging from 1.6 to 8.0 Tg yr−1 for the current climate, partly due to differences in horizontal resolution of meteorological input data. Also the simulated change in total isoprene emissions varies substantially across models explaining part of the different climate response on surface ozone. Ensemble mean changes in summer mean ozone and mean of daily maximum ozone are close to 1 ppb(v) in parts of the land area in southern Europe. Corresponding changes of 95-percentiles of hourly ozone are close to 2 ppb(v) in the same region. In northern Europe ensemble mean for mean and daily maximum show negative changes while there are no negative changes for the higher percentiles indicating that climate impacts on O3 could be especially important in connection with extreme summer events. URI: http://hdl.handle.net/10037/4913 File(s) in this item: 1
article.pdf (1.600Mb) -
Leiros, Hanna-Kirsti S. (Conference object; Konferansebidrag, 02-Sep-2010)[+][-]
Description: Innlegg på seminaret "Science - who cares?" ved NT-fak, Universitetet i Tromsø. URI: http://hdl.handle.net/10037/2697 File(s) in this item: 1
article.pdf (2.376Mb) -
Lejon, Tore; Gozhina, Olga Vladimirovna; Khrustalev, Victor N. (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: The molecule of the title compound, C16H21BO2, comprises a chiral fused tricyclic system containing five-membered (1,3,2-dioxaborolane), six-membered (cyclohexane) and four-membered (cyclobutane) rings. The 1,3,2-dioxaborolane ring is almost planar (r.m.s. deviation = 0.035 Å), and the syn H and Me substituents at this ring are in an eclipsed conformation. The cyclohexane and cyclobutane rings adopt sofa and butterfly conformations, respectively. The B atom has a trigonal-planar configuration (sum of the bond angles = 360.0°). The phenyl ring is practically coplanar with the 1,3,2-dioxaborolane ring [dihedral angle between the ring planes = 1.96 (8)°]. The absolute structure was determined from the known configuration of (+)-pinanediol which was used in the synthesis. In the crystal, weak C-H...[pi](Ph) interactions occur. URI: http://hdl.handle.net/10037/4635 File(s) in this item: 1
article.pdf (396.8Kb) -
Lejon, Tore; Gorovoy, Alexey Sergeevich; Khrustalev, Victor N. (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: The title compound, K+·C8H8BF3N3-, is a salt containing the chiral organic trifluoridoborate anion. The organic anions and potassium cations are tightly bound to each other by the coordination K-F [2.654 (3)-3.102 (3) Å] and K-N [2.951 (4)-3.338 (4) Å] interactions. Thus, the potassium cation adopts a nine-vertex coordination polyhedron, which can be described as a distorted monocapped tetragonal antiprism. In the crystal, the organic anions and potassium cations form layers parallel to (001). Weak C-H...[pi] interactions between neighbouring phenyl rings further stabilize the crystal. Description: This article is part of Alexey S. Gorovoy's doctoral thesis. Available in Munin at http://hdl.handle.net/10037/4653 URI: http://hdl.handle.net/10037/4734 File(s) in this item: 1
article.pdf (2.213Mb) -
Lejon, Tore Sigvard; Ingebrigtsen, Truls Erik; Hansen, Lars Kr (Journal article; Tidsskriftartikkel; Peer reviewed, 2006)[+][-]
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