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| 2. |
- Tuomi, Maria W., et al.
(författare)
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The increase of an allelopathic and unpalatable plant undermines reindeer pasture quality and current management in the Norwegian tundra
- 2024
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Ingår i: Communications Earth & Environment. - : Springer Nature. - 2662-4435. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Ongoing Arctic greening can increase productivity and reindeer pasture quality in the tundra. However, greening may also entail proliferation of unpalatable species, with consequences for pastoral social-ecological systems. Here we show extensive greening across 20 reindeer districts in Norway between 2003 and 2020, which has reduced pasture diversity. The allelopathic, evergreen dwarf-shrub crowberry increased its biomass by 60%, with smaller increases of deciduous shrubs and no increase in forbs and graminoids, the most species rich growth forms. There was no evidence for higher reindeer densities promoting crowberry. The current management decision-making process aims at sustainable pasture management but does not explicitly account for pasture changes and reduced diversity. Large-scale shifts towards evergreening and increased allelopathy may thus undermine the resource base for this key Arctic herbivore and the pastoral social-ecological system. Management that is sensitive to changes in pasture diversity could avoid mismanagement of a social-ecological system in transition.
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| 4. |
- Arnby, Karl, 1974, et al.
(författare)
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The effect of platinum distribution in monolithic catalysts on the oxidation of CO and hydrocarbons
- 2005
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 233:1, s. 176-185
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Tidskriftsartikel (refereegranskat)abstract
- Monolithic Pt/gamma-Al2O3 catalysts were prepd. by depositing of the platinum phase, either homogeneously or heterogeneously (i.e., local high platinum concn.), in the washcoat. The influence of the platinum distribution on the ignition and extinction processes for oxidn. of CO, propene, and propane, resp., was investigated by both temp.-programmed and oxygen step-response flow-reactor expts. In addn., in situ XANES spectroscopy was used to follow changes in the chem. state of platinum during propane oxidn. For samples with heterogeneous platinum distribution, the results show an improved low-temp. activity for CO oxidn., whereas no clear improvement is obsd. for oxidn. of propene or propane. Comparison of the results for CO and hydrocarbon oxidn. shows that the improved activity cannot be explained by thermal effects. Moreover, calcns. indicate that the enhanced activity for CO oxidn. can be due to mass-transfer phenomena. This could not be confirmed by our expts., however. Instead, the improved activity for CO oxidn. can be due to varying platinum particle size between the samples. Furthermore, the oxidn. of propane is shown to be highly influenced by the oxygen concn., showing an activity max. for gas compositions close to the stoichiometric. High oxygen levels result most probably in a predominantly oxygen-covered surface, which inhibits the reaction and, as supported by the in situ XANES experiments, passivates the surface by forming platinum oxide.
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- Becker, Hans-Christian, 1971, et al.
(författare)
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DNA Binding Properties of 2,7-Diazapyrene and its N-methylated Cations Studied by Linear and Circular Dichroism Spectroscopy and Calorimetry
- 1997
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 119:25, s. 5798-5803
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Tidskriftsartikel (refereegranskat)abstract
- The binding of 2,7-diazapyrene (DAP), N-methyl-2,7-diazapyrenium monocation (MDAP), and N,N'-dimethyl-2,7-diazapyrenium dication (DMDAP) to calf thymus DNA has been studied with respect to molecular geometry and thermodynamics. It is concluded from flow linear dichroism (LD) and induced circular dichroism (CD) spectra that the three diazapyrenes bind by intercalation to alternating AT as well as GC polynucleotide duplexes, as indicated by strong interactions with the transitions of the nucleobases in conjunction with approximately perpendicular orientations of the in-plane symmetry axes relative to the DNA helix axis. The reduced LD (LDt = LD/A(iso)) of the DNA complexes is characterized by marked fine structure, decreasing in the order DAP > MDAP > DMDAP. This finding is interpreted in terms of a microscopic heterogeneity associated with rotational mobility of the ligand in a tilted intercalation pocket, with the dication DMDAP having less rotational freedom than the neutral DAP has. Other distinct differences between the three diazapyrenes are revealed in their thermodynamic parameters of binding. DAP binds with a negative Delta H degrees (-9 kcal/mol) and a negative Delta S degrees (-7 cal/(mol K)), whereas the binding of the dication DMDAP is entropically driven (+43 cay(mol K)) but enthalpically disfavored (+5.2 kcal/mol), the monocation MDAP having an intermediate position (Delta H degrees = -3 kcal/mol, Delta S degrees = +12 cal/(mol K)).
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| 6. |
- Lee, Hyun Ju, et al.
(författare)
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The heme-copper oxidase superfamily shares a Zn2+-binding motif at the entrance to a proton pathway
- 2013
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 587:6, s. 770-774
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Tidskriftsartikel (refereegranskat)abstract
- Heme-copper oxidases (HCuOs) catalyse the reduction of oxygen, using the liberated free energy to maintain a proton-motive force across the membrane. In the mitochondrial-like A-type HCuOs, binding of heavy metal ions at the surface of the protein inhibits proton transfer. In bacterial C-type oxidases, the entry point to the proton pathway is on an accessory subunit unrelated to any subunit in A-type HCuOs. Despite this, we show here that heavy metal ions such as Zn2+ inhibit O-2-reduction very similarly in C-type as in A-type HCuOs, and furthermore that the binding site shares the same Glu-His motif. (C) 2013 Federation of European Biochemical Societies.
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