| 1. |
- Woitowich, N. C., et al.
(författare)
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Structural basis for light control of cell development revealed by crystal structures of a myxobacterial phytochrome
- 2018
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Ingår i: Iucrj. - : International Union of Crystallography (IUCr). - 2052-2525. ; 5:Part 5, s. 619-634
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Tidskriftsartikel (refereegranskat)abstract
- Phytochromes are red-light photoreceptors that were first characterized in plants, with homologs in photosynthetic and non-photosynthetic bacteria known as bacteriophytochromes (BphPs). Upon absorption of light, BphPs interconvert between two states denoted Pr and Pfr with distinct absorption spectra in the red and far-red. They have recently been engineered as enzymatic photoswitches for fluorescent-marker applications in non-invasive tissue imaging of mammals. This article presents cryo- and room-temperature crystal structures of the unusual phytochrome from the non-photosynthetic myxobacterium Stigmatella aurantiaca (SaBphP1) and reveals its role in the fruitingbody formation of this photomorphogenic bacterium. SaBphP1 lacks a conserved histidine (His) in the chromophore-binding domain that stabilizes the Pr state in the classical BphPs. Instead it contains a threonine (Thr), a feature that is restricted to several myxobacterial phytochromes and is not evolutionarily understood. SaBphP1 structures of the chromophore binding domain (CBD) and the complete photosensory core module (PCM) in wild-type and Thr-to-His mutant forms reveal details of the molecular mechanism of the Pr/Pfr transition associated with the physiological response of this myxobacterium to red light. Specifically, key structural differences in the CBD and PCM between the wild-type and the Thr-to-His mutant involve essential chromophore contacts with proximal amino acids, and point to how the photosignal is transduced through the rest of the protein, impacting the essential enzymatic activity in the photomorphogenic response of this myxobacterium.
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| 2. |
- Berg, S, et al.
(författare)
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Incidence and prognosis of meningitis due to Haemophilus influenzae, Streptococcus pneumoniae and Neisseria meningitidis in Sweden.
- 1996
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Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 28:3, s. 247-52
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Tidskriftsartikel (refereegranskat)abstract
- The incidence, concomitant conditions and case fatality rate of Haemophilus influenzae (Hi) and pneumococcal meningitis and of invasive meningococcal infections were studied retrospectively in Sweden (population 8.4 million) for the years 1987-89, the period before vaccination against Hi type b started. A total of 1,019 cases with culture-verified infection were found. The incidence rates per 100,000 per year were 1.8 for Hi meningitis, 1.2 for pneumococcal meningitis and 1.0 for invasive meningococcal infections. The age-specific incidence was highest in the 3-23 months age group for the 3 bacterial species. Pneumococcal meningitis was common in individuals > or = 60 years and meningococcal infections in the age-group 10-24 years. A serious concomitant condition was known in 57% of all patients with pneumococcal meningitis while this was uncommon for the other organisms. The case fatality rate was 2% for Hi meningitis, 24% for pneumococcal meningitis and 10% for meningococcal infections. All 81 pneumococcal isolates which had been serotyped belonged to serotypes in the 23-valent pneumococcal vaccine. Of the meningococcal isolates, 65% belonged to serogroup B. In conclusion, the high incidence of Hib meningitis justifies general Hib vaccination. Development of a vaccine against N. meningitidis group B should have high priority. Furthermore, improved pneumococcal vaccines are needed for patients with predisposing conditions. The currently available pneumococcal polysaccharide vaccine seems to be underused.
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| 3. |
- Edlund, Petra, et al.
(författare)
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The room temperature crystal structure of a bacterial phytochrome determined by serial femtosecond crystallography
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Phytochromes are a family of photoreceptors that control light responses of plants, fungi and bacteria. A sequence of structural changes, which is not yet fully understood, leads to activation of an output domain. Time-resolved serial femtosecond crystallography (SFX) can potentially shine light on these conformational changes. Here we report the room temperature crystal structure of the chromophore-binding domains of the Deinococcus radiodurans phytochrome at 2.1 angstrom resolution. The structure was obtained by serial femtosecond X-ray crystallography from microcrystals at an X-ray free electron laser. We find overall good agreement compared to a crystal structure at 1.35 angstrom resolution derived from conventional crystallography at cryogenic temperatures, which we also report here. The thioether linkage between chromophore and protein is subject to positional ambiguity at the synchrotron, but is fully resolved with SFX. The study paves the way for time-resolved structural investigations of the phytochrome photocycle with time-resolved SFX.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Ragunathrao, Vijay Avin Balaji, et al.
(författare)
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Sphingosine-1-Phosphate Receptor 1 Activity Promotes Tumor Growth by Amplifying VEGF-VEGFR2 Angiogenic Signaling
- 2019
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Ingår i: Cell Reports. - : CELL PRESS. - 2211-1247. ; 29:11, s. 3472-3487
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Tidskriftsartikel (refereegranskat)abstract
- The vascular endothelial growth factor-A (VEGF-A)-VEGFR2 pathway drives tumor vascularization by activating proangiogenic signaling in endothelial cells (ECs). Here, we show that EC-sphingosine-1-phosphate receptor 1 (S1PR1) amplifies VEGFR2-mediated angiogenic signaling to enhance tumor growth. We show that cancer cells induce S1 PR1 activity in ECs, and thereby, conditional deletion of Si PR1 in ECs (EC-Slpr1(-/-) mice) impairs tumor vascularization and growth. Mechanistically, we show that S1 PR1 engages the heterotrimeric G-protein Gi, which amplifies VEGF-VEGFR2 signaling due to an increase in the activity of the tyrosine kinase c-Abl1. c-Abl1, by phosphorylating VEGFR2 at tyrosine-951, prolongs VEGFR2 retention on the plasmalemma to sustain Rac1 activity and EC migration. Thus, S1 PR1 or VEGFR2 antagonists, alone or in combination, reverse the tumor growth in control mice to the level seen in EC-Slpr1(-/-) mice. Our findings suggest that blocking S1 PR1 activity in ECs has the potential to suppress tumor growth by preventing amplification of VEGF-VEGFR2 signaling.
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| 10. |
- Screaton, E., et al.
(författare)
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Interactions between deformation and fluids in the frontal thrust region of the NanTroSEIZE transect offshore the Kii Peninsula, Japan : Results from IODP Expedition 316 Sites C0006 and C0007
- 2009
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Ingår i: Geochemistry Geophysics Geosystems. - 1525-2027. ; 10, s. Q0AD01-
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Tidskriftsartikel (refereegranskat)abstract
- Integrated Ocean Drilling Program (IODP) Expedition 316 Sites C0006 and C0007 examined the deformation front of the Nankai accretionary prism offshore the Kii Peninsula, Japan. In the drilling area, the frontal thrust shows unusual behavior as compared to other regions of the Nankai Trough. Drilling results, integrated with observations from seismic reflection profiles, suggest that the frontal thrust has been active since similar to 0.78-0.436 Ma and accommodated similar to 13 to 34% of the estimated plate convergence during that time. The remainder has likely been distributed among out-of-sequence thrusts further landward and/or accommodated through diffuse shortening. Unlike results of previous drilling on the Nankai margin, porosity data provide no indication of undercompaction beneath thrust faults. Furthermore, pore water geochemistry data lack clear indicators of fluid flow from depth. These differences may be related to coarser material with higher permeability or more complex patterns of faulting that could potentially provide more avenues for fluid escape. In turn, fluid pressures may affect deformation. Well-drained, sand-rich material under the frontal thrust could have increased fault strength and helped to maintain a large taper angle near the toe. Recent resumption of normal frontal imbrication is inferred from seismic reflection data. Associated decollement propagation into weaker sediments at depth may help explain evidence for recent slope failures within the frontal thrust region. This evidence consists of seafloor bathymetry, normal faults documented in cores, and low porosities in near surface sediments that suggest removal of overlying material. Overall, results provide insight into the complex interactions between incoming materials, deformation, and fluids in the frontal thrust region.
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| 11. |
- Singh, S., et al.
(författare)
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2.0 Ga Granite of the Lower Package of the Higher Himalayan Crystallines, Maglad Khad, Sutlej Valley, Himachal Pradesh
- 2006
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Ingår i: Journal of the Geological Society of India. - 0016-7622 .- 0974-6889. ; 67:3, s. 295-300
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Tidskriftsartikel (refereegranskat)abstract
- Along the Sutlej valley, the lower package of the Higher Himalayan Crystallines (HHC) exposes a small concordant to discordant intrusive grey granite-The Maglad Khad Granite, within garnet mica schist/banded gneiss of the Jeori Formation. This body is fine grained and foliated along the margins, whereas the central part is relatively undeformed. This body along with aplites and pegmatites intrudes the country rock during early to syn-D-1 deformation. This is later affected by the most pervasive D-2-deformation producing gneissosity within the granite. U-Pb dating of zircons by conventional isotopic dilution technique yield an upper intercept age of 2068 +/- 5 Ma (2 sigma) from 6 zircon-fractions with MSWD=0.93, constraining the age of crystallization in the basal parts of the HHC during Early Proterozoic as well as the constraining pre-Himalayan fabric development.
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| 12. |
- Sofrata, Abier H, et al.
(författare)
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Strong antibacterial effect of miswak against oral microorganisms associated with periodontitis and caries.
- 2008
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Ingår i: Journal of periodontology. - : Wiley. - 0022-3492 .- 1943-3670. ; 79:8, s. 1474-9
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The chewing stick (miswak) is used for oral hygiene in many parts of the world. In addition to the mechanical removal of plaque, an antibacterial effect has been postulated; however, tests of miswak extract from Salvadora persica (Arak) disclosed only low to moderate antibacterial effects. This may be attributable to the extraction process. Our aim was to test in vitro the antibacterial effect of miswak pieces, without extraction, on bacteria implicated in the etiology of periodontitis and caries. METHODS: Miswak pieces were standardized by size and weight (0.07 and 0.14 g) and tested against Streptococcus mutans, Lactobacillus acidophilus, Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans), Porphyromonas gingivalis, and, as a reference, Haemophilus influenzae. The miswak pieces were tested in two ways: embedded in the agar plate or suspended above the agar plate. RESULTS: The inhibitory effect was most pronounced on P. gingivalis, A. actinomycetemcomitans, and H. influenzae, less on S. mutans, and least on L. acidophilus. Suspended miswak had comparable or stronger effects than miswak embedded in agar. The 0.14-g suspended miswak exhibited significantly greater inhibition on A. actinomycetemcomitans and H. influenzae than the 0.14-g miswak embedded in agar (P<0.01 and P<0.001, respectively). CONCLUSIONS: Miswak embedded in agar or suspended above the agar plate had strong antibacterial effects against all bacteria tested. The antibacterial effect of suspended miswak pieces suggests the presence of volatile active antibacterial compounds.
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| 13. |
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| 14. |
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| 15. |
- Bartenstein, J. E., et al.
(författare)
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Polymersomes at the solid-liquid interface : Dynamic morphological transformation and lubrication
- 2018
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Ingår i: Journal of Colloid and Interface Science. - : Academic Press. - 0021-9797 .- 1095-7103. ; 512, s. 260-271
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Tidskriftsartikel (refereegranskat)abstract
- Polymersomes are hollow spheres self-assembled from amphiphilic block copolymers of certain molecular architecture. Whilst they have been widely studied for biomedical applications, relatively few studies have reported their interfacial properties. In particular, lubrication by polymersomes has not been previously reported. Here, interfacial properties of polymersomes self-assembled from poly(butadiene)-poly(ethylene oxide) (PBD-PEO; molecular weight 10,400 g mol−1) have been studied at both hydrophilic and hydrophobic surfaces. Their morphology at silica and mica surfaces was imaged with quantitative nanomechanical property mapping atomic force microscopy (QNM AFM), and friction and surface forces they mediate under confinement between two surfaces were studied using colloidal probe AFM (CP-AFM). We find that the polymersomes remained intact but adopted flattened conformation once adsorbed to mica, with a relatively low coverage. However, on silica these polymersomes were unstable, rupturing to form donut shaped residues or patchy bilayers. On a silica surface hydrophobized with a 19 nm polystyrene (PS) film, the polymer vesicles formed a more stable layer with a higher surface coverage as compared to the hydrophilic surface, and the interfacial structure also evolved over time. Moreover, friction was greatly reduced on hydrophobized silica surfaces in the presence of polymersomes, suggesting their potential as effective aqueous lubricants.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Carlsson, Anna K, 1966, et al.
(författare)
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Observation of structure changes for Li/Cu(111) by photoemission from Li core and quantum-well states
- 1998
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 57:20, s. 13192 - 13198
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Tidskriftsartikel (refereegranskat)abstract
- Via photoemission from discrete quantum-well valence states and the Li 1s core level, three different types of atom rearrangements are observed for Cu(111)/Li. In the monolayer coverage range gradual energy shifts for the core-level as well as a quantum-well state reflect a gradual lateral compression of the Li overlayer as more atoms are adsorbed. The onset of Li substitution and formation of a (2×2) structure when, at RT, monolayer Li coverage is exceeded, is monitored via the disappearance and appearance of quantum-well states characteristic of the adsorbed full monolayer of Li and the part substitutional (2×2) structure, respectively. A splitting of the Li 1s emission peak into a doublet reflects the two different Li sites characteristic of the (2×2) phase. A small energy shift of the quantum-well state (25 meV) indicates that, if it is cooled (170 K), the substitutional structure is unstable with respect to Li adsorption.
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| 26. |
- Carlsson, Anna K, 1966, et al.
(författare)
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Oscillatory photoemission cross section for alkali monolayer quantum well states
- 1996
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 352-354, s. 656-659
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Tidskriftsartikel (refereegranskat)abstract
- A strong oscillatory photon energy dependence, observed in the photon energy range between 5 and 26 eV, for the intensity of photoemission peaks due to quantum well states in Na and Cs monolayers on Cu(111) is ascribed to interference between the contributions to the outgoing photoelectron wave from the two tails of the quantum well state.
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| 27. |
- Carlsson, Anna K, 1966, et al.
(författare)
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Oscillatory photoemission cross section for simple-metal quantum wells
- 1995
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 52:15, s. 11144 - 11146
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Tidskriftsartikel (refereegranskat)abstract
- A strong, oscillatory photon energy dependence is observed for the intensity of photoemission peaks due to quantum-well states in Na overlayers on Cu(111). The measurements are made at low photon energies (hν
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| 28. |
- Carlsson, Anna K, 1966, et al.
(författare)
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Structure changes for Cu(111)/Li observed via discrete quantum well states
- 1997
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Ingår i: Surface Review and Letters. - 0218-625X. ; 4:6, s. 1233-1237
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Tidskriftsartikel (refereegranskat)abstract
- Via photoemission in the near UV from discrete quantum well states, four different types of atom rearrangements are observed for Cu(111)/Li. In the monolayer range a gradual energy shift reflects a gradual compression of the Li layer as more atoms are adsorbed. The onset of Li substitution and formation of a (2×2) structure when, at RT, monolayer Li coverage is exceeded is monitored via the appearance of a quantum well state characteristic of the new phase. A small energy shift indicates that, if it is cooled (170 K), the new structure is unstable with respect to Li adsorption. Finally, an energy downshift with increasing coverage observed for a state characteristic of 2 ML Li is ascribed to an increasing area for one-atomic-layer-high islands formed by Li atoms on top of the first full layer.
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| 29. |
- Carlsson, Anna K, 1966, et al.
(författare)
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Valence-Electron Resonances in Alkali-Metal Overlayers Observed via Photoemission Line-Shape Changes
- 1996
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 77:2, s. 346 - 349
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Tidskriftsartikel (refereegranskat)abstract
- Valence-electron resonances for Na overlayers on Ag(111) and Cu(111) are observed by photoemission via line-shape changes for the substrate s,p-band emission in a narrow range of photon energies. The effect is ascribed to interfering contributions to the photoelectron wave from the substrate and the vacuum barrier.
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| 30. |
- Carlsson, Jan, et al.
(författare)
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Catalase inhibition by sulfide and hydrogen peroxide-induced mutagenicity in Salmonella typhimurium strain TA102
- 1988
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Ingår i: Mutation research. - : Elsevier. - 0027-5107 .- 1873-135X. ; 202:1, s. 59-64
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Tidskriftsartikel (refereegranskat)abstract
- The lethal and mutagenic effects of hydrogen peroxide were studied in exponentially growing cultures of Salmonella typhimurium strain TA102. Exposure of the cultures to non-lethal levels of sodium sulfide significantly increased the lethality and mutagenicity of hydrogen peroxide. The catalase activity was decreased in cells exposed to sodium sulfide, but there were no changes in the cellular levels of superoxide dismutase, glutathione reductase, or NADPH-dependent alkyl hydroperoxide reductase. Hydrogen peroxide-induced mutagenesis and killing of S. typhimurium strain TA102 in the presence of sulfide may in part be explained by an inactivation of catalase by sulfide.
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| 31. |
- Carrillo, M., et al.
(författare)
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High-resolution crystal structures of transient intermediates in the phytochrome photocycle
- 2021
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Ingår i: Structure. - : Elsevier BV. - 0969-2126. ; 29:7
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Tidskriftsartikel (refereegranskat)abstract
- Phytochromes are red/far-red light photoreceptors in bacteria to plants, which elicit a variety of important physiological responses. They display a reversible photocycle between the resting Pr state and the light-activated Pfr state. Light signals are transduced as structural change through the entire protein to modulate its activity. It is unknown how the Pr-to-Pfr interconversion occurs, as the structure of intermediates remains notoriously elusive. Here, we present short-lived crystal structures of the photosensory core modules of the bacteriophytochrome from myxobacterium Stigmatella aurantiaca captured by an X-ray free electron laser 5 ns and 33 ms after light illumination of the Pr state. We observe large structural displacements of the covalently bound bilin chromophore, which trigger a bifurcated signaling pathway that extends through the entire protein. The snapshots show with atomic precision how the signal progresses from the chromophore, explaining how plants, bacteria, and fungi sense red light.
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| 32. |
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| 33. |
- Cho, DL, et al.
(författare)
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Structure and surface properties of plasma polymerized acrylic acid layers
- 1990
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Ingår i: Journal of Applied Polymer Science. - 0021-8995 .- 1097-4628. ; 41, s. 1373-1390
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Tidskriftsartikel (refereegranskat)abstract
- Thin plasma polymerized layers of acrylic acid (PPAA) were deposited onto polyethylene and muscovite mica surfaces. Structure and surface properties of the deposited layer depend on the polymerization conditions. The content of carboxylic groups in the layer decreases, whereas the degree of crosslinking or branching increases, with increasing discharge power. A soft, sticky layer with a low contact angle against water is obtained when a low discharge power (5 W) is used. In contrast, a hard film with a rather high water contact angle is obtained when the discharge power is high (50 W). A surface force apparatus was employed to study some film properties including adhesion force, crack formation, and capillary condensation. The adhesion force between plasma polymerized acrylic acid layers prepared at a low discharge power is high in dry air. It decreases remarkably in humid air and no adhesion is observed in water. In dry air, the adhesion force between PPAA layers decreases as the discharge power increases.
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| 34. |
- Christenson, H. K., et al.
(författare)
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Direct measurements of the force between hydrophobic surfaces in water
- 2001
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Ingår i: Advances in Colloid and Interface Science. - 0001-8686 .- 1873-3727. ; 91:3, s. 391-436
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Forskningsöversikt (refereegranskat)abstract
- Direct measurements of the force between hydrophobic surfaces across aqueous solutions are reviewed. The results are presented according to the method of preparation of the hydrophobic surfaces. No single model appears to fit all published results, and an attempt is made to classify the measured interactions in three different categories. The large variation of the measured interaction, often within each class, depending on the type of hydrophobic surface is emphasized. (I) Stable hydrophobic surfaces show only a comparatively short-range interaction, although little quantitative data on this attraction have been published. (II) Many results showing very long-range attractive forces are most likely due to the presence of sub-microscopic bubbles on the hydrophobic surfaces. Such an interaction is typically measured between silica surfaces made hydrophobic by silylation. Between self-assembled thiol layers on gold surfaces very short-range attractive forces are possibly due to the presence or nucleation of bubbles. The reason for the apparent stability of these bubbles is not clear and warrants further investigation. (III) Results obtained with LB films of surfactants or lipids on mica appear to give rise to a different type of force that fits neither of these two categories. This force is an exponentially decaying attraction, often of considerable range. The force turns more attractive at smaller separations, and may at short range be similar to the interaction measured between stable hydrophobic surfaces. An apparently similar, exponential attraction is also found between mica surfaces bearing surfactants adsorbed from cyclohexane, between silylated, plasma-treated mica surfaces and between both mica and silica surfaces with surfactants adsorbed in situ. This type of force also occurs between some surfaces of relatively low hydrophobicity as well as between one such hydrophobic surface and a hydrophilic surface. No convincing model can explain this third type of interaction for all systems in which it has been observed. This review of work to date points to the importance of the morphology and structure of the hydrophobic surface, and how it may change during the interaction of two surfaces.
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| 35. |
- Claesson, Cecilia B., et al.
(författare)
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Drug use in Swedish nursing homes
- 1998
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Ingår i: Clinical drug investigation. - 1173-2563 .- 1179-1918. ; 16:6, s. 441-52
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Tidskriftsartikel (refereegranskat)
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| 36. |
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| 37. |
- Claesson, Elin, 1989, et al.
(författare)
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The primary structural photoresponse of phytochrome proteins captured by a femtosecond X-ray laser
- 2020
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Ingår i: eLife. - 2050-084X. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Phytochrome proteins control the growth, reproduction, and photosynthesis of plants, fungi, and bacteria. Light is detected by a bilin cofactor, but it remains elusive how this leads to activation of the protein through structural changes. We present serial femtosecond X-ray crystallographic data of the chromophore-binding domains of a bacterial phytochrome at delay times of 1 ps and 10 ps after photoexcitation. The data reveal a twist of the D-ring, which leads to partial detachment of the chromophore from the protein. Unexpectedly, the conserved so-called pyrrole water is photodissociated from the chromophore, concomitant with movement of the A-ring and a key signaling aspartate. The changes are wired together by ultrafast backbone and water movements around the chromophore, channeling them into signal transduction towards the output domains. We suggest that the observed collective changes are important for the phytochrome photoresponse, explaining the earliest steps of how plants, fungi and bacteria sense red light.
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| 38. |
- Claesson, Hans, et al.
(författare)
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Rheological behaviour during UV-curing of a star-branched polyester
- 2002
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Ingår i: Progress in organic coatings. - 0300-9440 .- 1873-331X. ; 44:1, s. 63-67
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Tidskriftsartikel (refereegranskat)abstract
- Using a rheometer coupled with an UV-light generator, the viscoelastic behaviour during the fast cure of star-branched polyester is investigated. The 32 arm star polymers consist of a hyperbranched polyester core, Boltorn(TM) and linear grafts of poly(E-caprolactone) (degree of polymerisation: 20-52) with methacrylate end groups. The resins are crystalline and the melting points range from 34 to 50degreesC; films can be formed and cured below 80degreesC. The crossover of G' and G was used as the gel point. The time to reach the gel point, a few seconds, increases linearly with molecular weight.
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| 39. |
- Claesson, Hans, et al.
(författare)
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Semi-crystalline thermoset resins : tailoring rheological properties in melt using comb structures with crystalline grafts
- 2004
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Ingår i: Progress in organic coatings. - : Elsevier BV. - 0300-9440 .- 1873-331X. ; 49:1, s. 13-22
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Tidskriftsartikel (refereegranskat)abstract
- Thermosetting resins with semi-crystalline grafts have been synthesized. An amorphous resin with epoxide groups was first functionalized with hydroxyl groups using 2,2-bis(methylol) propionic acid, bis-MPA in bulk at 155 degreesC. Functionalization with bis-MPA was monitored using FT-IR, FT-Raman and SEC. The reaction was complete in 30 min. Grafts of poly(epsilon-caprolactone) were then grown from the hydroxyl functional resin and end capped with methacrylate groups. The polymerization Of epsilon-caprolactone, performed in bulk at 110 degreesC using Sn(Oct)(2), was characterized using H-1 NMR and SEC. The obtained molecular weights agreed well with theoretical values. The final end capping was performed using methacrylic anhydride, and monitored with SEC and H-1 NMR, which indicated full substitution. Two combs were synthesized with different arm lengths, DP 10 and 20, and the obtained M-W were close to calculated values. The complex viscosity was measured from low to high temperature for the crystalline resins, the amorphous resin and blends thereof. Rheological data show a rapid decrease in viscosity within a temperature change of 10-15 degreesC for the crystalline resins while the amorphous resin exhibited a slow softening. The blends exhibited a behavior in-between that of the crystalline and the amorphous resin. Films were prepared from the pure resins and the blends. The films were cured using UV irradiation. The comb architecture of these resins has advantages such as crystallinity, high molecular weight and low viscosity, facilitating leveling and resulting in smooth films. The final film properties varied with the ratio of crystalline to amorphous resin, where increase in the amount of crystalline resin correlated with increased the flexibility.
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| 40. |
- Claesson, Hans, et al.
(författare)
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Synthesis and characterisation of star branched polyesters with dendritic cores and the effect of structural variations on zero shear rate viscosity
- 2002
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 43:12, s. 3511-3518
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Tidskriftsartikel (refereegranskat)abstract
- A series of branched polyesters consisting of poly(epsilon-caprolactone) (PCL) (degree of polymerisation: 5-200) initiated from hydroxy-functional cores and end-capped with methylmethacrylate have been prepared. The cores were third-generation hyperbranched polyester, Boltorn, with approximately 32 hydroxyl groups, a third-generation dendrimer with 24 hydroxyl groups and a third-generation dendron with eight hydroxyl groups. Finally, a linear PCL was synthesised as a reference material. All initiators were based on 2,2-bis(methylol) propionic acid (bis-MPA). C-13 NMR spectra of the polymers showed that those with shorter arms contained unreacted hydroxyl groups on the core. Rheological measurements of zero shear rate viscosity, eta(0), showed that the branched polyesters had a considerably lower eta(0) than linear polyester with similar molecular weight. The low melt viscosity and the crystallity produced a theological behaviour suitable for the film formation process for powder coatings. Measurements of mechanical properties of cured films showed that those with low arm molecular weight, M-a, were amorphous while those of high M-a were crystalline.
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| 41. |
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| 42. |
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| 43. |
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| 44. |
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| 45. |
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| 46. |
- Claesson, K, et al.
(författare)
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Role of endovascular intervention in patients with diabetic foot ulcer and concomitant peripheral arterial disease.
- 2011
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Ingår i: International Angiology. - 1827-1839. ; 30:4, s. 349-358
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Tidskriftsartikel (refereegranskat)abstract
- AIM: The aim of this study was to evaluate wound healing, major amputation and mortality in patients with diabetic foot ulcer and peripheral arterial disease (PAD), and to compare the group decided to have an endovascular intervention with groups referred to conservative treatment or to those judged as unreconstructable. METHODS: A retrospective two-year review of all patients with diabetic foot ulcers and PAD presented at an interdisciplinary diabetic foot round 2006-2007 at Malmö University Hospital, Sweden, was performed. Independent predictive factors of insufficient ulcer healing, amputation and mortality during follow-up were analysed according to treatment decisions at the diabetic foot round. RESULTS: A total of 135 limbs in 115 consecutive diabetic patients with foot ulcers were included. Median age was 73 years and 41% were women. During a median follow-up time of 17 months, 44% of the ulcers did not heal, 15% of the limbs underwent major amputation and 42% died. Ulcer depth with a Wagner grade ≥3 (hazard ratio [HR] 5.8; 95% confidence interval [CI] 2.6-12.9), CRP (HR 1.007; 95% CI 1.002-1.012, and impaired run-off (HR 3.0; 95% CI 1.03-8.9) were independent risk factors for incomplete wound healing. The three treatment decision groups: attempt for endovascular leg revascularization (N.=75), conservative (N.=42) and unreconstructable (N.=18) showed no significant difference in terms of wound healing, major amputation or death. CONCLUSION: Patients with diabetic foot ulcers and concomitant PAD are at high risk for limb loss and premature death. Ulcer depth, CRP and impaired run-off are independent risk factors for incomplete wound healing. There is an apparent need for prospective controlled studies to better define the role of endovascular therapy in this subset of diabetic foot ulcer patients.
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- Claesson, Maria, 1985, et al.
(författare)
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Meso-ordered soft hydrogels
- 2012
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 8:31, s. 8149-8156
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Tidskriftsartikel (refereegranskat)abstract
- Many factors such as cross-link density are known to dictate the properties of hydrogels; however, less is known about the microstructure and how it can be tailored to control the properties. Here we demonstrate a method of forming microstructured hydrogels using a soft template that allows us to control and modify the microstructure. Meso-ordered hydrogels were formed by chemically cross-linking poly(ethylene glycol)-diacrylate (PEG-DA) segments via photopolymerization in the presence of poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (EOxPOyEOx) block copolymers. The results showed that hydrogels with lamellar mesostructured regions were formed when high concentrations of PEG-DA segments (50%) were used in combination with block co-polymers having certain ratios of the hydrophilic and hydrophobic blocks (P123, EO20PO70EO20). Only lamellar mesostructures were observed, independent of the PEG molecular weight (1500 or 3400 g mol(-1)) or block co-polymer concentration (10-50%). This finding demonstrates that it is possible to form soft meso-ordered hydrogels using block co-polymers as templates, and they do not follow the same mesophase behavior as the purely self-assembled block co-polymers.
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