| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Ahlgren, Christina, et al.
(författare)
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Gender analysis of musculoskeletal disorders and emotional exhaustion : interactive effects from physical and psychosocial work exposures and engagement in domestic work
- 2012
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Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 55:2, s. 212-228
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to assess the relationships between physical and psychosocial work exposures, engagement in domestic work and work-home imbalance in relation to symptoms of musculoskeletal disorders and emotional exhaustion in white- and blue-collar men and women. Three thousand employees from 21 companies were asked to answer a questionnaire on family structure, household and child care tasks, work exposure, work-home imbalance and symptoms of neck/shoulder disorders, low back disorders and emotional exhaustion. Women reported more musculoskeletal disorders and engagement in domestic work. Adverse at-work exposures were highest in blue-collar women. High engagement in domestic work was not separately associated with symptoms but paid work exposure factors were associated. High engagement in domestic work interacted with adverse work exposure and increased risk estimates for low back disorders and emotional exhaustion. Reported work-home imbalance was associated with neck/shoulder disorders in women and with emotional exhaustion in both women and men. Practitioner Summary. The current article adds to earlier research by showing that high engagement in domestic work is not separately associated with increased symptoms, but interacts with psychosocial work exposure variables to produce emotional exhaustion in both women and men and low back disorders in women.
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| 3. |
- Ahlgren, Christina, et al.
(författare)
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The meanings given to gender in studies on multimodal rehabilitation for patients with chronic musculoskeletal pain : a literature review
- 2016
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Ingår i: Disability and Rehabilitation. - : Informa UK Limited. - 0963-8288 .- 1464-5165. ; 38:23, s. 2255-2270
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Forskningsöversikt (refereegranskat)abstract
- Purpose: The purpose of this study is to assess and describe the meanings given to "gender" in scientific publications that evaluate multidisciplinary, interdisciplinary or multimodal rehabilitation for patients with chronic musculoskeletal pain.Method: A systematic literature search for papers evaluating multimodal rehabilitation was conducted. The PubMed and EBSCO databases were searched from 1995 to 2015. Two or three researchers independently read each paper, performed a quality assessment and coded meanings of gender using qualitative content analysis.Results: Twenty-seven papers were included in the review. Gender was used very differently in the MMR studies investigated but primarily it referred to factual differences between men and women. Only one paper provided a definition of the concept of gender and how it had been used in that study. In the content analysis, the meaning of gender formed three categories: "Gender as a factual difference", "The man is the ideal" and "Gender as a result of social role expectations".Conclusions: The meaning of the concept of gender in multimodal rehabilitation is undefined and needs to be developed further. The way the concept is used should be defined in the design and evaluation of multimodal rehabilitation in future studies.Implications for rehabilitationHealthcare professionals should reflect on gender relations in encounters with patients, selection of patients into rehabilitation programs and design of programs. In rehabilitation for chronic pain the patients' social circumstances and cultural context should be given the same consideration as biological sex and pain symptoms.
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| 4. |
- Ahlgren, Eva Christina, et al.
(författare)
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Iron-induced oligomerization of human FXN81-210 and bacterial CyaY frataxin and the effect of iron chelators
- 2017
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- Patients suffering from the progressive neurodegenerative disease Friedreich’s ataxia have reduced expression levels of the protein frataxin. Three major isoforms of human frataxin have been identified, FXN42-210, FXN56-210 and FXN81-210, of which FXN81-210 is considered to be the mature form. Both long forms, FXN42-210 and FXN56-210, have been shown to spontaneously form oligomeric particles stabilized by the extended N-terminal sequence. The short variant FXN81-210, on other hand, has only been observed in the monomeric state. However, a highly homologous E. coli frataxin CyaY, which also lacks an N-terminal extension, has been shown to oligomerize in the presence of iron. To explore the mechanisms of stabilization of short variant frataxin oligomers we compare here the effect of iron on the oligomerization of CyaY and FXN81-210. Using dynamic light scattering, small-angle X-ray scattering, electron microscopy (EM) and cross linking mass spectrometry (MS), we show that at aerobic conditions in the presence of iron both FXN81-210 and CyaY form oligomers. However, while CyaY oligomers are stable over time, FXN81-210 oligomers are unstable and dissociate into monomers after about 24 h. EM and MS studies suggest that within the oligomers FXN81-210 and CyaY monomers are packed in a head-to-tail fashion in ring-shaped structures with potential iron-binding sites located at the interface between monomers. The higher stability of CyaY oligomers can be explained by a higher number of acidic residues at the interface between monomers, which may result in a more stable iron binding. We also show that CyaY oligomers may be dissociated by ferric iron chelators deferiprone and DFO, as well as by the ferrous iron chelator BIPY. Surprisingly, deferiprone and DFO stimulate FXN81-210 oligomerization, while BIPY does not show any effect on oligomerization in this case. The results suggest that FXN81-210 oligomerization is primarily driven by ferric iron, while both ferric and ferrous iron participate in CyaY oligomer stabilization. Analysis of the amino acid sequences of bacterial and eukaryotic frataxins suggests that variations in the position of the acidic residues in helix 1, β-strand 1 and the loop between them may control the mode of frataxin oligomerization.
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| 5. |
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| 6. |
- Ahlgren, Karin, et al.
(författare)
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De stora restaureringarna : Från Uppsala domkyrka till Skokloster
- 2004
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Rapport (populärvet., debatt m.m.)abstract
- De stora restaureringarna har varit årets tema. Genom att dokumentera och analysera teori och praktik i några av 1800- och 1900-talets största restaureringar - från genomgripande stilrestaureringar till ett mer återhållsamt och tekniskt skonsamt synsätt. Därmed får vi också ett bättre underlag även för dagens ställningstagande.Föremål för våra studier är Uppsala domkyrka, Gripsholms slott, Vreta klosterkyrka, Gustav 11I:s paviljong i Haga, Kungapalatset i Vadstena och Skoklosters slott. Vi hoppas att denna utställning skall bidra till en kritisk hållning och en ökad kunskap om restaureringskonsten, som kvalificerad yrkesuppgift, tidsspegel för historiesyn och som gestaltningsideal.
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| 7. |
- Fekry, Mostafa, et al.
(författare)
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SAXS and stability studies of iron-induced oligomers of bacterial frataxin CyaY
- 2017
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:9, s. 0184961-0184961
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Tidskriftsartikel (refereegranskat)abstract
- Frataxin is a highly conserved protein found in both prokaryotes and eukaryotes. It is involved in several central functions in cells, which include iron delivery to biochemical processes, such as heme synthesis, assembly of iron-sulfur clusters (ISC), storage of surplus iron in conditions of iron overload, and repair of ISC in aconitase. Frataxin from different organisms has been shown to undergo iron-dependent oligomerization. At least two different classes of oligomers, with different modes of oligomer packing and stabilization, have been identified. Here, we continue our efforts to explore the factors that control the oligomerization of frataxin from different organisms, and focus on E. coli frataxin CyaY. Using small-angle X-ray scattering (SAXS), we show that higher iron-to-protein ratios lead to larger oligomeric species, and that oligomerization proceeds in a linear fashion as a results of iron oxidation. Native mass spectrometry and online size-exclusion chromatography combined with SAXS show that a dimer is the most common form of CyaY in the presence of iron at atmospheric conditions. Modeling of the dimer using the SAXS data confirms the earlier proposed head-to-tail packing arrangement of monomers. This packing mode brings several conserved acidic residues into close proximity to each other, creating an environment for metal ion binding and possibly even mineralization. Together with negative-stain electron microscopy, the experiments also show that trimers, tetramers, pentamers, and presumably higher-order oligomers may exist in solution. Nano-differential scanning fluorimetry shows that the oligomers have limited stability and may easily dissociate at elevated temperatures. The factors affecting the possible oligomerization mode are discussed.
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| 8. |
- Gakh, Oleksandr, et al.
(författare)
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Architecture of the human mitochondrial iron-sulfur cluster assembly machinery
- 2016
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Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 291:40, s. 21296-21321
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Tidskriftsartikel (refereegranskat)abstract
- Fe-S clusters, essential cofactors needed for the activity of many different enzymes, are assembled by conserved protein machineries inside bacteria and mitochondria. As the architecture of the human machinery remains undefined, we co-expressed in Escherichia coli the following four proteins involved in the initial step of Fe-S cluster synthesis: FXN42-210 (iron donor); [NFS1]·[ISD11] (sulfur donor); and ISCU (scaffold upon which new clusters are assembled). We purified a stable, active complex consisting of all four proteins with 1:1:1:1 stoichiometry. Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional model of the complex with ∼14 Å resolution. Molecular dynamics flexible fitting of protein structures docked into the EM map of the model revealed a [FXN42-210]24·[NFS1]24·[ISD11]24·[ISCU]24 complex, consistent with the measured 1:1:1:1 stoichiometry of its four components. The complex structure fulfills distance constraints obtained from chemical cross-linking of the complex at multiple recurring interfaces, involving hydrogen bonds, salt bridges, or hydrophobic interactions between conserved residues. The complex consists of a central roughly cubic [FXN42-210]24·[ISCU]24 sub-complex with one symmetric ISCU trimer bound on top of one symmetric FXN42-210 trimer at each of its eight vertices. Binding of 12 [NFS1]2·[ISD11]2 sub-complexes to the surface results in a globular macromolecule with a diameter of ∼15 nm and creates 24 Fe-S cluster assembly centers. The organization of each center recapitulates a previously proposed conserved mechanism for sulfur donation from NFS1 to ISCU and reveals, for the first time, a path for iron donation from FXN42-210 to ISCU.
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| 9. |
- Söderberg, Christopher, et al.
(författare)
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The molecular basis of iron-induced oligomerization of frataxin and the role of the ferroxidation reaction in oligomerization.
- 2013
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 288:12, s. 8156-8167
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Tidskriftsartikel (refereegranskat)abstract
- The role of the mitochondrial protein frataxin in iron storage and detoxification, iron delivery to iron-sulfur cluster biosynthesis, heme biosynthesis and aconitase repair has been extensively studied during the last decade. However, still no general consensus exists on the details of the mechanism of frataxin function and oligomerization. Here, using small-angle X-ray scattering (SAXS) and X-ray crystallography, we describe the solution structure of the oligomers formed during the iron-dependent assembly of yeast (Yfh1) and E. coli (CyaY) frataxin. At an iron-to-protein ratio of 2, the initially monomeric Yfh1 is converted to a trimeric form in solution. The trimer in turn serves as the assembly unit for higher-order oligomers induced at higher iron-to-protein ratios. The X-ray crystallographic structure obtained from iron-soaked crystals demonstrates that iron binds at the trimer-trimer interaction sites, presumably contributing to oligomer stabilization. For the ferroxidation-deficient D79A;D82A variant of Yfh1, iron-dependent oligomerization may still take place, although more than 50% of the protein is found in the monomeric state at the highest iron-to-protein ratio used. This demonstrates that the ferroxidation reaction controls frataxin assembly and presumably the iron chaperone function of frataxin and its interactions with target proteins. For E. coli CyaY, the assembly unit of higher order oligomers is a tetramer, which could be an effect of the much shorter N-terminal region of this protein. The results show that understanding of the mechanistic features of frataxin function requires detailed knowledge of the interplay between the ferroxidation reaction, iron-induced oligomerization and the structure of oligomers formed during assembly.
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