| 1. |
- Hantke, Max F., et al.
(författare)
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High-throughput imaging of heterogeneous cell organelles with an X-ray laser
- 2014
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Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 8:12, s. 943-949
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Tidskriftsartikel (refereegranskat)abstract
- We overcome two of the most daunting challenges in single-particle diffractive imaging: collecting many high-quality diffraction patterns on a small amount of sample and separating components from mixed samples. We demonstrate this on carboxysomes, which are polyhedral cell organelles that vary in size and facilitate up to 40% of Earth's carbon fixation. A new aerosol sample-injector allowed us to record 70,000 low-noise diffraction patterns in 12 min with the Linac Coherent Light Source running at 120 Hz. We separate different structures directly from the diffraction data and show that the size distribution is preserved during sample delivery. We automate phase retrieval and avoid reconstruction artefacts caused by missing modes. We attain the highest-resolution reconstructions on the smallest single biological objects imaged with an X-ray laser to date. These advances lay the foundations for accurate, high-throughput structure determination by flash-diffractive imaging and offer a means to study structure and structural heterogeneity in biology and elsewhere.
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| 2. |
- Van Lun, Michiel, et al.
(författare)
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CO2 and O-2 Distribution in Rubisco Suggests the Small Subunit Functions as a CO2 Reservoir
- 2014
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 136:8, s. 3165-3171
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Tidskriftsartikel (refereegranskat)abstract
- Protein gas interactions are important in biology. The enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes two competing reactions involving CO2 and O-2 as substrates. Carboxylation of the common substrate ribulose-1,5-bisphosphate leads to photosynthetic carbon assimilation, while the oxygenation reaction competes with carboxylation and reduces photosynthetic productivity. The migration of the two gases in and around Rubisco was investigated using molecular dynamics simulations. The results indicate that at equal concentrations of the gases, Rubisco binds CO2 stronger than it does O-2. Amino acids with small hydrophobic side chains are the most proficient in attracting CO2, indicating a significant contribution of the hydrophobic effect in the interaction. On average, residues in the small subunit bind approximately twice as much CO2 as do residues in the large subunit. We did not detect any cavities that would provide a route to the active site for the gases. Instead, CO2 appears to be guided toward the active site through a CO2 binding region around the active site opening that extends to the closest neighboring small subunits. Taken together, these results suggest the small subunit may function as a "reservoir" for CO2 storage.
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| 3. |
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| 4. |
- Andersson, Inger S., et al.
(författare)
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Perceptions of nursing care quality, in acute hospital settings measured by the Karen instruments
- 2013
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Ingår i: Journal of Nursing Management. - : Blackwell Publishing. - 0966-0429 .- 1365-2834. ; 21:1, s. 87-93
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Tidskriftsartikel (refereegranskat)abstract
- Aims The objectives of this study were to measure the quality of nursing care from the perspectives of patients and personnel and to compare these perspectives. Background The perception of quality in nursing care is affected by patient needs and it is common that patients and personnel disagree on the nature of the quality. Thus, it is important to measure the quality from both perspectives. Method A total of 95 patients and 120 personnel from surgical and medical wards at a hospital in Sweden participated. The Karen instruments were used for data collection. A scale index was used for comparison of the perspectives. Results The patients and personnel were satisfied with the quality of care and there were no obvious differences in the total index. The different subscales indicated areas of lower care quality in need of improvement. Conclusion The quality of the care seemed to be satisfactory from the perspectives of both the patients and the personal. Further analysis from the subscale or a variable level is needed to define areas of lower care quality. Implications for Nursing Management Measurements have to be carried out continuously to guarantee care quality over time, as a result of organisational changes and financial cutbacks.
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| 5. |
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| 6. |
- Hasse, Dirk, et al.
(författare)
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Structure of the Homodimeric Glycine Decarboxylase P-protein from Synechocystis sp PCC 6803 Suggests a Mechanism for Redox Regulation
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:49, s. 35333-35345
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Tidskriftsartikel (refereegranskat)abstract
- Glycine decarboxylase, or P-protein, is a pyridoxal 5-phosphate (PLP)-dependent enzyme in one-carbon metabolism of all organisms, in the glycine and serine catabolism of vertebrates, and in the photorespiratory pathway of oxygenic phototrophs. P-protein from the cyanobacterium Synechocystis sp. PCC 6803 is an (2) homodimer with high homology to eukaryotic P-proteins. The crystal structure of the apoenzyme shows the C terminus locked in a closed conformation by a disulfide bond between Cys(972) in the C terminus and Cys(353) located in the active site. The presence of the disulfide bridge isolates the active site from solvent and hinders the binding of PLP and glycine in the active site. Variants produced by substitution of Cys(972) and Cys(353) by Ser using site-directed mutagenesis have distinctly lower specific activities, supporting the crucial role of these highly conserved redox-sensitive amino acid residues for P-protein activity. Reduction of the 353-972 disulfide releases the C terminus and allows access to the active site. PLP and the substrate glycine bind in the active site of this reduced enzyme and appear to cause further conformational changes involving a flexible surface loop. The observation of the disulfide bond that acts to stabilize the closed form suggests a molecular mechanism for the redox-dependent activation of glycine decarboxylase observed earlier.
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| 8. |
- Valegård, Karin, et al.
(författare)
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Structural and mechanistic studies of the orf12 gene product from the clavulanic acid biosynthesis pathway
- 2013
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Ingår i: Acta Crystallographica Section D. - 0907-4449 .- 1399-0047. ; 69, s. 1567-1579
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Tidskriftsartikel (refereegranskat)abstract
- Structural and biochemical studies of the orf12 gene product (ORF12) from the clavulanic acid (CA) biosynthesis gene cluster are described. Sequence and crystallographic analyses reveal two domains: a C-terminal penicillin-binding protein (PBP)/beta-lactamase-type fold with highest structural similarity to the class A beta-lactamases fused to an N-terminal domain with a fold similar to steroid isomerases and polyketide cyclases. The C-terminal domain of ORF12 did not show beta-lactamase or PBP activity for the substrates tested, but did show low-level esterase activity towards 3'-O-acetyl cephalosporins and a thioester substrate. Mutagenesis studies imply that Ser173, which is present in a conserved SXXK motif, acts as a nucleophile in catalysis, consistent with studies of related esterases, beta-lactamases and d-Ala carboxypeptidases. Structures of wild-type ORF12 and of catalytic residue variants were obtained in complex with and in the absence of clavulanic acid. The role of ORF12 in clavulanic acid biosynthesis is unknown, but it may be involved in the epimerization of (3S,5S)-clavaminic acid to (3R,5R)-clavulanic acid.
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| 9. |
- Hofsten, Anna, et al.
(författare)
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Case seminars open new doors to understanding : nursing students’ experiences of learning
- 2012
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Konferensbidrag (refereegranskat)abstract
- BackgroundThe Case Method is a teaching method in which cases from real life inspire students to actively seek knowledge that they discuss in seminars. During seminars, different solutions and ideas are written in a structured way on the white board. Hofsten (2010) described how case seminars in cardiology help nursing students share knowledge and identify possible ways of dealing with patients.Summary of workTo deepen the understanding of learning in case seminars, we asked students in a very different educational context, psychiatric care, about their experiences. Written narratives from 44 nursing students were analyzed using a content analysis.Summary of resultsThe students described the importance of different perspectives and of seeing a context and of learning in a climate that promotes discussions; they felt that the overview on the white board encouraged students to participate. Different categories and the preliminary themes To reflect on thoughts, To give and take, and To see what is said are shown in Figure 1. When we presented these results to the students, most reported recognizing our description of learning situation to a great or very great degree; see Figure 2.ConclusionsThe Case Method seems to involve students in a way that deepens their understanding and this effect seems to be independent of subject or teacher
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