| 1. |
- Vautard, R., et al.
(författare)
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Skill and uncertainty of a regional air quality model ensemble
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 43:31, s. 4822-4832
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Tidskriftsartikel (refereegranskat)abstract
- Recently several regional air quality projects were carried out to support the negotiation under the Clean Air For Europe (CAFE) programme by predicting the impact of emission control policies with an ensemble of models. Within these projects, CITYDELTA and EURODELTA, the fate of air quality at the scale of European cities or that of the European continent was studied using several models. In this article we focus on the results of EURODELTA. The predictive skill of the ensemble of models is described for ozone, nitrogen dioxide and secondary inorganic compounds, and the uncertainty in air quality modelling is examined through the model ensemble spread of concentrations. For ozone daily maxima the ensemble spread origin differs from one region to another. In the neighbourhood of cities or in mountainous areas the spread of predicted values does not span the range of observed data, due to poorly resolved emissions or complex-terrain meteorology. By contrast in Atlantic and North Sea coastal areas the spread of predicted values is found to be larger than the observations. This is attributed to large differences in the boundary conditions used in the different models. For NO2 daily averages the ensemble spread is generally too small compared with observations. This is because models miss highest values occurring in stagnant meteorology in stable boundary layers near cities. For secondary particulate matter compounds the simulated concentration spread is more balanced, observations falling nearly equiprobably within the ensemble, and the spread originates both from meteorology and aerosol chemistry and thermodynamics. © 2008.
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| 2. |
- Groeneveld, Tom, et al.
(författare)
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Interactions of the extracellular matrix proteoglycans decorin and biglycan with C1q and collectins
- 2005
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Ingår i: Journal of Immunology. - 1550-6606. ; 175:7, s. 4715-4723
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Tidskriftsartikel (refereegranskat)abstract
- Decorin and biglycan are closely related abundant extracellular matrix proteoglycans that have been shown to bind to C1q. Given the overall structural similarities between C1q and mannose-binding lectin (MBL), the two key recognition molecules of the classical and the lectin complement pathways, respectively, we have examined functional consequences of the interaction of C1q and MBL with decorin and biglycan. Recombinant forms of human decorin and biglycan bound C1q via both collagen and globular domains and inhibited the classical pathway. Decorin also bound C1 without activating complement. Furthermore, decorin and biglycan bound efficiently to MBL, but only biglycan could inhibit activation of the lectin pathway. Other members of the collectin family, including human surfactant protein D, bovine collectin-43, and conglutinin also showed binding to decorin and biglycan. Decorin and biglycan strongly inhibited C1q binding to human endothelial cells and U937 cells, and biglycan suppressed C1q-induced MCP-1 and IL-8 production by human endothelial cells. In conclusion, decorin and biglycan act as inhibitors of activation of the complement cascade, cellular interactions, and proinflammatory cytokine production mediated by C1q. These two proteoglycans are likely to down-regulate proinflammatory effects mediated by C1q, and possibly also the collectins, at the tissue level.
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| 3. |
- Ivanov, Alexander G, et al.
(författare)
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Acclimation to temperature and irradiance modulates PSII charge recombination.
- 2006
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793. ; 580:11, s. 2797-802
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Tidskriftsartikel (refereegranskat)abstract
- Acclimation of wild type and the chlorina F2 mutant of barley to either high light or low temperature results in a 2- to 3-fold increase in non-photochemical quenching which occurred independently of either energy-dependent quenching (qE), xanthophyll cycle-mediated antenna quenching or state transitions. Results of in vivo thermoluminescence measurements used to address this conundrum indicated that excitation pressure regulates the temperature gap for Click to view the MathML source and Click to view the MathML source charge recombinations within photosystem II reaction centers. This is discussed in terms of photoprotection through non-radiative charge recombination.
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| 4. |
- Morgan-Kiss, R M, et al.
(författare)
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The Antarctic psychrophile, Chlamydomonas raudensis Ettl (UWO241) (Chlorophyceae, Chlorophyta), exhibits a limited capacity to photoacclimate to red light
- 2005
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 41:4, s. 791-800
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Tidskriftsartikel (refereegranskat)abstract
- The psychrophilic Antarctic alga, Chlamydomonas raudensis Ettl (UWO241), grows under an extreme environment of low temperature and low irradiance of a limited spectral quality (blue-green). We investigated the ability of C. raudensis to acclimate to long-term imbalances in excitation caused by light quality through adjustments in photosystem stoichiometry. Log-phase cultures of C. raudensis and C. reinhardtii grown under white light were shifted to either blue or red light for 12 h. Previously, we reported that C. raudensis lacks the ability to redistribute light energy via the short-term mechanism of state transitions. However, similar to the model of mesophilic alga, C. reinhardtii, the psychrophile retained the capacity for long-term adjustment in energy distribution between PSI and PSII by modulating the levels of PSI reaction center polypeptides, PsaA/PsaB, with minimal changes in the content of the PSII polypeptide, D1, in response to changes in light quality. The functional consequences of the modulation in PSI/PSII stoichiometry in the psychrophile were distinct from those observed in C. reinhardtii. Exposure of C. raudensis to red light caused 1) an inhibition of growth and photosynthetic rates, 2) an increased reduction state of the intersystem plastoquinone pool with concomitant increases in nonphotochemical quenching, 3) an uncoupling of the major light-harvesting complex from the PSII core, and 4) differential thylakoid protein phosphorylation profiles compared with C. reinhardtii. We conclude that the characteristic low levels of PSI relative to PSII set the limit in the capacity of C. raudensis to photoacclimate to an environment enriched in red light.
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| 5. |
- Rosso, Dominic, et al.
(författare)
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IMMUTANS does not act as a stress-induced safety valve in the protection of the photosynthetic apparatus of Arabidopsis during steady-state photosynthesis.
- 2006
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 142:2, s. 574-85
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Tidskriftsartikel (refereegranskat)abstract
- IMMUTANS (IM) encodes a thylakoid membrane protein that has been hypothesized to act as a terminal oxidase that couples the reduction of O2 to the oxidation of the plastoquinone (PQ) pool of the photosynthetic electron transport chain. Because IM shares sequence similarity to the stress-induced mitochondrial alternative oxidase (AOX), it has been suggested that the protein encoded by IM acts as a safety valve during the generation of excess photosynthetically generated electrons. We combined in vivo chlorophyll fluorescence quenching analyses with measurements of the redox state of P700 to assess the capacity of IM to compete with photosystem I for intersystem electrons during steady-state photosynthesis in Arabidopsis (Arabidopsis thaliana). Comparisons were made between wild-type plants, im mutant plants, as well as transgenics in which IM protein levels had been overexpressed six (OE-6x) and 16 (OE-16x) times. Immunoblots indicated that IM abundance was the only major variant that we could detect between these genotypes. Overexpression of IM did not result in increased capacity to keep the PQ pool oxidized compared to either the wild type or im grown under control conditions (25°C and photosynthetic photon flux density of 150 µmol photons m–2 s–1). Similar results were observed either after 3-d cold stress at 5°C or after full-leaf expansion at 5°C and photosynthetic photon flux density of 150 µmol photons m–2 s–1. Furthermore, IM abundance did not enhance protection of either photosystem II or photosystem I from photoinhibition at either 25°C or 5°C. Our in vivo data indicate that modulation of IM expression and polypeptide accumulation does not alter the flux of intersystem electrons to P700+ during steady-state photosynthesis and does not provide any significant photoprotection. In contrast to AOX1a, meta-analyses of published Arabidopsis microarray data indicated that IM expression exhibited minimal modulation in response to myriad abiotic stresses, which is consistent with our functional data. However, IM exhibited significant modulation in response to development in concert with changes in AOX1a expression. Thus, neither our functional analyses of the IM knockout and overexpression lines nor meta-analyses of gene expression support the model that IM acts as a safety valve to regulate the redox state of the PQ pool during stress and acclimation. Rather, IM appears to be strongly regulated by developmental stage of Arabidopsis.
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