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- Fuller, Franklin D, et al.
(författare)
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Drop-on-demand sample delivery for studying biocatalysts in action at X-ray free-electron lasers
- 2017
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Ingår i: Nature Methods. - : Macmillan Publishers Ltd.. - 1548-7091 .- 1548-7105. ; 14, s. 443-449
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Tidskriftsartikel (refereegranskat)abstract
- X-ray crystallography at X-ray free-electron laser sources is a powerful method for studying macromolecules at biologically relevant temperatures. Moreover, when combined with complementary techniques like X-ray emission spectroscopy, both global structures and chemical properties of metalloenzymes can be obtained concurrently, providing insights into the interplay between the protein structure and dynamics and the chemistry at an active site. The implementation of such a multimodal approach can be compromised by conflicting requirements to optimize each individual method. In particular, the method used for sample delivery greatly affects the data quality. We present here a robust way of delivering controlled sample amounts on demand using acoustic droplet ejection coupled with a conveyor belt drive that is optimized for crystallography and spectroscopy measurements of photochemical and chemical reactions over a wide range of time scales. Studies with photosystem II, the phytochrome photoreceptor, and ribonucleotide reductase R2 illustrate the power and versatility of this method.
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| 2. |
- Bishop, Kevin, et al.
(författare)
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The Effects of Forestry on Hg Bioaccumulation in Nemoral/Boreal Waters and Recommendations for Good Silvicultural Practice
- 2009
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Ingår i: Ambio. - : Royal Swedish Academy of Sciences. - 0044-7447 .- 1654-7209. ; 38:7, s. 373-380
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Tidskriftsartikel (refereegranskat)abstract
- Mercury (Hg) levels are alarmingly high in fish from lakes across Fennoscandia and northern North America. The few published studies on the ways in which silviculture practices influence this problem indicate that forest operations increase Hg in downstream aquatic ecosystems. From these studies, we estimate that between one-tenth and one-quarter of the Hg in the fish of high-latitude, managed forest landscapes can be attributed to harvesting. Forestry, however, did not create the elevated Hg levels in the soils, and waterborne Hg/MeHg concentrations downstream from harvested areas are similar to those from wetlands. Given the current understanding of the way in which silviculture impacts Hg cycling, most of the recommendations for good forest practice in Sweden appear to be appropriate for high-latitude regions, e.g., leaving riparian buffer zones, as well as reducing disturbance at stream crossings and in moist areas. The recommendation to restore wetlands and reduce drainage, however, will likely increase Hg/MeHg loadings to aquatic ecosystems
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| 3. |
- Futter, Martyn, et al.
(författare)
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Consequences of nitrate leaching following stem-only harvesting of Swedish forests are dependent on spatial scale
- 2010
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 158:12, s. 3552-3559
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Tidskriftsartikel (refereegranskat)abstract
- Short-term increases in soil solution nitrate (NO3-) concentration are often observed after forest harvest, even in N-limited systems. We model NO3- leaching below the rooting zone as a function of site productivity. Using national forest inventories and published estimates of N attenuation in rivers and the riparian zone, we estimate effects of stem-only harvesting on NO3- leaching to groundwater, surface waters and the marine environment. Stem-only harvesting is a minor contributor to NO3- pollution of Swedish waters. Effects in surface waters are rapidly diluted downstream, but can be locally important for shallow well-waters as well as for the total amount of N reaching the sea. Harvesting adds approximately 8 Gg NO3-N to soil waters in Sweden, with local concentrations up to 7 mg NO3-N 1(-1). Of that, similar to 3.3 Gg reaches the marine environment. This is similar to 3% of the overall Swedish N load to the Baltic. (C) 2010 Elsevier Ltd. All rights reserved.
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| 7. |
- Quist, E, et al.
(författare)
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Responses of a nitrogen-saturated forest to a sharp decrease in nitrogen input
- 1999
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Ingår i: Journal of Environmental Quality. - 0047-2425 .- 1537-2537. ; 28, s. 1970-1977
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Tidskriftsartikel (refereegranskat)abstract
- The reversibility of induced N saturation was investigated in a 46- yr-old pine (Pinus sylvestris L.) forest in northern Sweden Ammonium nitrate has been applied annually since 1971 to plots (30 by 30 m) at average dosages of 36 (N1), 72 (N2), and 108 (N3) kg N ha(-1) yr(-1): with or without P and K addition (background N deposition is <4 kg ha(-1) yr(-1)). In 1990, after two decades of treatment, the largest N application (N3) was suspended, while N1 and N2 still received ammonium nitrate applications. Seven gears after the last application in N3, the N availability measured as N concentration in plants spine roots and needles and in leaves of the grass Deschampsia flexuosa (L.) Trin.] and activity of the enzyme nitrate reductase in leaves of D. flexuosa, and N-15 uptake by excised pine roots, was at the same levels as in N1, although more than twice the amount of N has been applied in total to N3. The arginine concentrations in pine needles, concentrations of exchangeable mineral N in the organic layer and the uppermost 20 cm of the mineral soil were at the same levels as in the control plots. Thus, an experimentally induced N excess was, according to these measurements, to a high degree reversed 7 yr after the last N application. However, the composition of the understory vegetation still differed markedly from the untreated control 8 yr after the last N3 application.
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