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151.
Joachim Audet David Bastviken Mirco Bundschuh Ishi Buffam Alexander Feckler Leif Klemedtsson Hjalmar Laudon Stefan Lfgren Sivakiruthika Natchimuthu Mats
quist Mike Peacock Marcus B. Wallin 《Global Change Biology》2020,26(2):629-641
Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N2O). N2O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N2O emissions from forest streams although they constitute a major part of the total stream network globally. Here, we compiled N2O concentration data from low‐order streams (~1,000 observations from 172 stream sites) covering a large geographical gradient in Sweden from the temperate to the boreal zone and representing catchments with various degrees of agriculture and forest coverage. Our results showed that agricultural and forest streams had comparable N2O concentrations of 1.6 ± 2.1 and 1.3 ± 1.8 µg N/L, respectively (mean ± SD) despite higher total N (TN) concentrations in agricultural streams (1,520 ± 1,640 vs. 780 ± 600 µg N/L). Although clear patterns linking N2O concentrations and environmental variables were difficult to discern, the percent saturation of N2O in the streams was positively correlated with stream concentration of TN and negatively correlated with pH. We speculate that the apparent contradiction between lower TN concentration but similar N2O concentrations in forest streams than in agricultural streams is due to the low pH (<6) in forest soils and streams which affects denitrification and yields higher N2O emissions. An estimate of the N2O emission from low‐order streams at the national scale revealed that ~1.8 × 109 g N2O‐N are emitted annually in Sweden, with forest streams contributing about 80% of the total stream emission. Hence, our results provide evidence that forest streams can act as substantial N2O sources in the landscape with 800 × 109 g CO2‐eq emitted annually in Sweden, equivalent to 25% of the total N2O emissions from the Swedish agricultural sector. 相似文献
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Angerer H Zwicker K Wumaier Z Sokolova L Heide H Steger M Kaiser S Nübel E Brutschy B Radermacher M Brandt U Zickermann V 《The Biochemical journal》2011,437(2):279-288
Mitochondrial NADH:ubiquinone oxidoreductase (complex I) is a very large membrane protein complex with a central function in energy metabolism. Complex I from the aerobic yeast Yarrowia lipolytica comprises 14 central subunits that harbour the bioenergetic core functions and at least 28 accessory subunits. Despite progress in structure determination, the position of individual accessory subunits in the enzyme complex remains largely unknown. Proteomic analysis of subcomplex Iδ revealed that it lacked eleven subunits, including the central subunits ND1 and ND3 forming the interface between the peripheral and the membrane arm in bacterial complex I. This unexpected observation provided insight into the structural organization of the connection between the two major parts of mitochondrial complex I. Combining recent structural information, biochemical evidence on the assignment of individual subunits to the subdomains of complex I and sequence-based predictions for the targeting of subunits to different mitochondrial compartments, we derived a model for the arrangement of the subunits in the membrane arm of mitochondrial complex I. 相似文献
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Puppo F Griseri P Fanelli M Schena F Romeo G Pelicci P Ceccherini I Ravazzolo R Patrone G 《FEBS letters》2002,519(1-3):123-127
IscA homologs are known to be involved in iron-sulfur cluster formation in various organisms. Recombinant proteins of two IscA homologs from the cyanobacterium Synechocystis PCC 6803, designated SLR1417 and SLR1565, were purified. The absorption spectrum of purified SLR1565 was typical for [2Fe-2S] cluster-containing proteins, whereas that of SLR1417 predominantly showed the presence of the iron ion alone. In the cyanobacterial cell extracts, only SLR1565 was found to form a complex with a novel prokaryotic HEAT-repeats-containing protein, SLR1098. Thus, the two cyanobacterial IscA protein homologs exist in distinct molecular states, suggesting different cellular roles for these proteins. 相似文献
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Mirco Sorci Minghao Gu Caryn L. Heldt Elizabeth Grafeld Georges Belfort 《Biotechnology and bioengineering》2013,110(6):1704-1713
In an effort to increase selectivity among proteins with crossflow ultrafiltration, we offer and demonstrate a comprehensive approach to fractionate proteins of similar molecular weight and relatively close pI values. This multidimensional approach involves optimizing membrane charge type and density together with operating conditions such as precise control of pH, ionic strength, and transmembrane pressure for reduced membrane fouling. Each filtration experiment was performed in cross‐flow configuration for ~20 min, allowing fast screening for optimal separation as determined by maximum selectivity, Ψ, and purity, P. Using our comprehensive approach for fractionating mixtures RNase A–lysozyme and BSA–hemoglobin, we obtained values of Ψ = 9.1, P = 95.7%, and Ψ = 6.5, P = 62.1%, respectively. Biotechnol. Bioeng. 2013; 110: 1704–1713. © 2013 Wiley Periodicals, Inc. 相似文献
157.
Matthias Peichl Oliver Sonnentag Georg Wohlfahrt Lawrence B. Flanagan Dennis D. Baldocchi Gerard Kiely Marta Galvagno Damiano Gianelle Barbara Marcolla Casimiro Pio Mirco Migliavacca Michael B. Jones Matthew Saunders 《Ecology letters》2013,16(4):502-512
Metabolic theory and body size constraints on biomass production and decomposition suggest that differences in the intrinsic potential net ecosystem production (NEPPOT) should be small among contrasting C3 grasslands and therefore unable to explain the wide range in the annual apparent net ecosystem production (NEPAPP) reported by previous studies. We estimated NEPPOT for nine C3 grasslands under contrasting climate and management regimes using multiyear eddy covariance data. NEPPOT converged within a narrow range, suggesting little difference in the net carbon dioxide uptake capacity among C3 grasslands. Our results indicate a unique feature of C3 grasslands compared with other terrestrial ecosystems and suggest a state of stability in NEPPOT due to tightly coupled production and respiration processes. Consequently, the annual NEPAPP of C3 grasslands is primarily a function of seasonal and short‐term environmental and management constraints, and therefore especially susceptible to changes in future climate patterns and associated adaptation of management practices. 相似文献
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Jonas Jägermeyr Dieter Gerten Wolfgang Lucht Patrick Hostert Mirco Migliavacca Ramakrishna Nemani 《Global Change Biology》2014,20(4):1191-1210
A better understanding of the local variability in land‐atmosphere carbon fluxes is crucial to improving the accuracy of global carbon budgets. Operational satellite data backed by ground measurements at Fluxnet sites proved valuable in monitoring local variability of gross primary production at highly resolved spatio‐temporal resolutions. Yet, we lack similar operational estimates of ecosystem respiration (Re) to calculate net carbon fluxes. If successful, carbon fluxes from such a remote sensing approach would form an independent and sought after measure to complement widely used dynamic global vegetation models (DGVMs). Here, we establish an operational semi‐empirical Re model, based only on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) with a resolution of 1 km and 8 days. Fluxnet measurements between 2000 and 2009 from 100 sites across North America and Europe are used for parameterization and validation. Our analysis shows that Re is closely tied to temperature and plant productivity. By separating temporal and intersite variation, we find that MODIS land surface temperature (LST) and enhanced vegetation index (EVI) are sufficient to explain observed Re across most major biomes with a negligible bias [R² = 0.62, RMSE = 1.32 (g C m?2 d?1), MBE = 0.05 (g C m?2 d?1)]. A comparison of such satellite‐derived Re with those simulated by the DGVM LPJmL reveals similar spatial patterns. However, LPJmL shows higher temperature sensitivities and consistently simulates higher Re values, in high‐latitude and subtropical regions. These differences remain difficult to explain and they are likely associated either with LPJmL parameterization or with systematic errors in the Fluxnet sampling technique. While uncertainties remain with Re estimates, the model formulated in this study provides an operational, cross‐validated and unbiased approach to scale Fluxnet Re to the continental scale and advances knowledge of spatio‐temporal Re variability. 相似文献
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Investigation of maximum local specific absorption rate in 7 T magnetic resonance with respect to load size by use of electromagnetic simulations 下载免费PDF全文
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