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- Son, G.S., et al.
(författare)
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Binding Mode of Norfloxacin to Calf Thymus DNA
- 1998
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 120:26, s. 6451-6457
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Tidskriftsartikel (refereegranskat)abstract
- Norfloxacin, a quinolone antibacterial reagent, has been studied with respect to its binding to calf thymus DNA using fluorescence and linear dichroism techniques and unwinding of supercoiled DNA. The fluorescence of norfloxacin is strongly quenched in the presence of DNA and using this decrease in a fluorescence titration the equilibrium constant of the complex formation was established to be 2.8 x 10(3) M-1. The electric transition moments of the norfloxacin chromophore have been analyzed using fluorescence anisotropy, magnetic circular dichroism, and linear dichroism in stretched poly(vinyl alcohol) film and INDO/S calculations. These data are then used to interpret flow linear dichroism results for the norfloxacin-DNA complex. The transition moments for the long-wavelength transitions are found to be oriented at about 65.0-85.0 degrees with respect to the DNA helix axis. A near perpendicular orientation of the norfloxacin chromophore plane makes it possible to exclude classical groove or surface binding modes. The possibility of a classical intercalation binding mode also can be ruled out from unwinding experiments. However, it is shown that the molecular plane of norfloxacin is near perpendicular relative to the DNA helix axis with a possibility of a bending of the DNA helix at the binding site.
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- Aamaas, Borgar, et al.
(författare)
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Elemental carbon deposition to Svalbard snow from Norwegian settlements and long-range transport
- 2011
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Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 63:3, s. 340-351
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Tidskriftsartikel (refereegranskat)abstract
- The impact on snow pack albedo from local elemental carbon (EC) sources in Svalbard has been investigated for the winter of 2008. Highly elevated EC concentrations in the snow are observed around the settlements of Longyearbyen and Svea (locally > 1000 ng g(-1), about 200 times over the background level), while EC concentrations similar to the background level are seen around Ny-Alesund. Near Longyearbyen and Svea, darkened snow influenced by wind transported coal dust from open coal stockpiles is clearly visible from satellite images and by eye at the ground. As a first estimate, the reduction in snow albedo caused by local EC pollution from the Norwegian settlements has been compared to the estimated reduction caused by long-range transported EC for entire Svalbard. The effect of local EC from Longyearbyen, Svea and all Norwegian settlements are estimated to 2.1%, 7.9% and 10% of the total impact of EC, respectively. The EC particles tend to stay on the surface during melting, and elevated EC concentrations due to the spring melt was observed. This accumulation of EC enhances the positive albedo feedbacks. The EC concentrations were observed to be larger in metamorphosed snow than in fresh snow, and especially around ice lenses.
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- Bakhtiary-Davijany, Hamidreza, et al.
(författare)
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Analysis of External and Internal Mass Transfer at Low Reynolds Numbers in a Multiple-Slit Packed Bed Microstructured Reactor for Synthesis of Methanol from Syngas
- 2012
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 51:42, s. 13574-13579
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Tidskriftsartikel (refereegranskat)abstract
- The possibility of mass transfer limitations in an integrated micro packed bed reactor-heat exchanger (IMPBRHE) for methanol synthesis was experimentally investigated. Experiments were performed with three different particle size distributions (50-200 mu m) of a Cu-based catalyst at 80 bar and 215-270 degrees C. Negligible effects of pore diffusion limitations on the performance of the reactor under methanol synthesis conditions for catalyst particle diameters up to 125 mu m were found. Due to a very low Reynolds numbers (similar to 1) and dominance of molecular diffusion, variation of the total pressure was applied as a suitable technique to alter the diffusivities of reactants in the gas mixture by dilution, while keeping the reactant flow and partial pressure constant. No significant change in the CO conversion was observed in the temperature range 235-255 degrees C, pressure range 50-90 bar, and for reactant contact times of 105-308 ms.g/mL. The same procedure was applied to a laboratory. fixed bed reactor with similar results. Possible heat transfer effects associated with the dilution were shown to be negligible. We therefore conclude that both reactor systems operate in the absence of external mass transfer limitations.
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- Dork, T, et al.
(författare)
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Two truncating variants in FANCC and breast cancer risk
- 2019
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1, s. 12524-
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Tidskriftsartikel (refereegranskat)abstract
- Fanconi anemia (FA) is a genetically heterogeneous disorder with 22 disease-causing genes reported to date. In some FA genes, monoallelic mutations have been found to be associated with breast cancer risk, while the risk associations of others remain unknown. The gene for FA type C, FANCC, has been proposed as a breast cancer susceptibility gene based on epidemiological and sequencing studies. We used the Oncoarray project to genotype two truncating FANCC variants (p.R185X and p.R548X) in 64,760 breast cancer cases and 49,793 controls of European descent. FANCC mutations were observed in 25 cases (14 with p.R185X, 11 with p.R548X) and 26 controls (18 with p.R185X, 8 with p.R548X). There was no evidence of an association with the risk of breast cancer, neither overall (odds ratio 0.77, 95%CI 0.44–1.33, p = 0.4) nor by histology, hormone receptor status, age or family history. We conclude that the breast cancer risk association of these two FANCC variants, if any, is much smaller than for BRCA1, BRCA2 or PALB2 mutations. If this applies to all truncating variants in FANCC it would suggest there are differences between FA genes in their roles on breast cancer risk and demonstrates the merit of large consortia for clarifying risk associations of rare variants.
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- Eneroth, Kristina, et al.
(författare)
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Springtime depletion of tropospheric ozone, gaseous elemental mercury and non-methane hydrocarbons in the European Arctic, and its relation to atmospheric transport
- 2007
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 41:38, s. 8511-8526
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Tidskriftsartikel (refereegranskat)abstract
- Using a trajectory climatology for the period 1992-2001 we have examined how seasonal changes in transport cause changes in the concentrations of tropospheric ozone (O-3), gaseous elemental mercury (GEM) and non-methane hydrocarbons (NMHCs) observed at the Mt. Zeppelin station, Ny-angstrom lesund (78.9 degrees N, 11.9 degrees E). During April-June O-3 depletion events were frequently observed in connection with air transport across the Arctic Basin. The O-3 loss was most pronounced in air masses advected close to the surface. This result supports the idea that the O-3 depletion reactions take place in the lowermost part of the atmosphere in the central Arctic Basin. A strong positive correlation between springtime O-3 depletion events and the oxidation of GEM to divalent mercury was found. During air mass advection from Siberia, the Barents Sea and the Norwegian Sea the strongest correlation was observed during April-May, whereas air masses originating from the Canadian Arctic and the central Arctic areas showed the highest O-3-GEM correlation in May-June. We suggest that this 1-month lag could either be due to the position of the marginal ice zone or temperature differences between the northwestern and northeastern air masses. In connection with springtime O-3 depletion events low concentrations of some NMHCs, especially ethane and ethyne, were observed, indicating that both bromine (ethyne oxidant) and chlorine radicals (ethane oxidant) are present in the Arctic atmosphere during spring. In winter, negative correlations between O-3 and NMHCs were found in connection with air transport from Europe and Siberia, which we interpret as O-3 destruction taking place in industrially contaminated plumes.
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| 9. |
- Hodson, Andy, et al.
(författare)
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Glacier ecosystem response to episodic nitrogen enrichment in Svalbard, European High Arctic
- 2010
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 98:03-jan, s. 171-184
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Tidskriftsartikel (refereegranskat)abstract
- We describe the climatology, hydrology and biogeochemistry of an extreme nitrogen deposition event that occurred in the highly glacierised environment of the European High Arctic during June 1999. Meteorological analysis, three-dimensional air mass trajectories and a 3D transport model show that blocking high pressures over Scandinavia and the rapid advection of western European pollution toward Svalbard were sufficient to cause the most concentrated (1.15 ppm NO3-N and 1.20 ppm NH4-N), high magnitude (total 26 mm and up to 2.4 mm h(-1) at 30 m above sea level) nitrogen deposition event on record in this sensitive, high Arctic environment (78.91A degrees A N, 11.93A degrees A E). Since the event occurred when much of the catchment remained frozen or under snow cover, microbial utilisation of nitrogen within snowpacks and perennially unfrozen subglacial sediments, rather than soils, were mostly responsible for reducing N export. The rainfall event occurred long before the annual subglacial outburst flood and so prolonged (ca. 10 day) water storage at the glacier bed further enhanced the microbial assimilation. When the subglacial outburst eventually occurred, high runoff and concentrations of NO3 (-) (but not NH4 (+)) returned in the downstream rivers. Assimilation accounted for between 53 and 72% of the total inorganic nitrogen deposited during the event, but the annual NO3 (-) and NH4 (+) runoff yields were still enhanced by up to 5 and 40 times respectively. Episodic atmospheric inputs of reactive nitrogen can therefore directly influence the biogeochemical functioning of High Arctic catchments, even when microbial activity takes place beneath a glacier at a time when terrestrial soil ecosystems remain frozen and unresponsive.
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