| 1. |
- Strakova, A., et al.
(författare)
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Recurrent horizontal transfer identifies mitochondrial positive selection in a transmissible cancer
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Autonomous replication and segregation of mitochondrial DNA (mtDNA) creates the potential for evolutionary conflict driven by emergence of haplotypes under positive selection for 'selfish' traits, such as replicative advantage. However, few cases of this phenomenon arising within natural populations have been described. Here, we survey the frequency of mtDNA horizontal transfer within the canine transmissible venereal tumour (CTVT), a contagious cancer clone that occasionally acquires mtDNA from its hosts. Remarkably, one canine mtDNA haplotype, A1d1a, has repeatedly and recently colonised CTVT cells, recurrently replacing incumbent CTVT haplotypes. An A1d1a control region polymorphism predicted to influence transcription is fixed in the products of an A1d1a recombination event and occurs somatically on other CTVT mtDNA backgrounds. We present a model whereby 'selfish' positive selection acting on a regulatory variant drives repeated fixation of A1d1a within CTVT cells.
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| 2. |
- Faatz, B., et al.
(författare)
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Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator
- 2016
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs-dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated in both FELs simultaneously. FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.
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| 3. |
- Afanaciev, K.G., et al.
(författare)
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Investigation of the radiation hardness of GaAs sensors in an electron beam
- 2012
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 7:11
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Tidskriftsartikel (refereegranskat)abstract
- A compact and finely grained sandwich calorimeter is designed to instrument the very forward region of a detector at a future e+e- collider. The calorimeter will be exposed to low energy e+e - pairs originating from beamstrahlung, resulting in absorbed doses of about one MGy per year. GaAs pad sensors interleaved with tungsten absorber plates are considered as an option for this calorimeter. Several Cr-doped GaAs sensor prototypes were produced and irradiated with 8.5-10 MeV electrons up to a dose of 1.5 MGy. The sensor performance was measured as a function of the absorbed dose.
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| 4. |
- Graafsma, Heinz, et al.
(författare)
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Detector developments for photon science at DESY
- 2023
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Ingår i: Frontiers in Physics. - : Frontiers Media SA. - 2296-424X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- The past, current and planned future developments of X-ray imagers in the Photon-Science Detector Group at DESY-Hamburg is presented. the X-ray imagers are custom developed and tailored to the different X-ray sources in Hamburg, including the storage ring PETRA III/IV; the VUV-soft X-ray free electron laser FLASH, and the European Free-Electron Laser. Each source puts different requirements on the X-ray detectors, which is described in detail, together with the technical solutions implemented.
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| 5. |
- Ignatenko, O. V., et al.
(författare)
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Electrochemistry of chemically trapped dimeric and monomeric recombinant horseradish peroxidase
- 2013
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Ingår i: Advances in Biosensors and Bioelectronics. - : Science and Engineering Publishing Company. - 2326-473X. ; 2:3, s. 25-34
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Tidskriftsartikel (refereegranskat)abstract
- Native horseradish peroxidase (nHRP) exists in the aggregated form in concentrated water solutions as shown by dynamic light scattering (DLS). This is in contrast to recombinant horseradish peroxidase (recHRP) which mainly exists as a dimer. The native enzyme aggregates could be broken into the particles of nm-size only under the conditions of high ionic strength (0.5-1 M NaCl). Chemical cross-linking of recHRP with glutaraldehyde in water solutions yields 40% of the dimer. The chemically trapped dimeric and monomeric forms of recHRP were separated by gel-filtration, their substrate specificity towards a number of organic substrates compared. Parameters of direct and mediated electron transfer on graphite electrodes catalyzed by both preparations were analyzed. The difference in behavior of the monomeric and dimeric enzyme forms observed in electrochemical experiments was interpreted as a result of a “double” coverage of the electrode surface with the molecules of cross-linked dimeric enzyme, in contrast to both modified monomeric and original, unmodified recHRP providing “monolayer” coverage. In addition to the stabilization effects achieved due to enzyme surface modification with glutaraldehyde, the “double” coverage doubles the enzyme activity per surface unit.
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| 6. |
- Ekeberg, Tomas, 1983-, et al.
(författare)
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Observation of a single protein by ultrafast X-ray diffraction
- 2024
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Ingår i: Light. - : Springer Nature. - 2095-5545 .- 2047-7538. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- The idea of using ultrashort X-ray pulses to obtain images of single proteins frozen in time has fascinated and inspired many. It was one of the arguments for building X-ray free-electron lasers. According to theory, the extremely intense pulses provide sufficient signal to dispense with using crystals as an amplifier, and the ultrashort pulse duration permits capturing the diffraction data before the sample inevitably explodes. This was first demonstrated on biological samples a decade ago on the giant mimivirus. Since then, a large collaboration has been pushing the limit of the smallest sample that can be imaged. The ability to capture snapshots on the timescale of atomic vibrations, while keeping the sample at room temperature, may allow probing the entire conformational phase space of macromolecules. Here we show the first observation of an X-ray diffraction pattern from a single protein, that of Escherichia coli GroEL which at 14 nm in diameter is the smallest biological sample ever imaged by X-rays, and demonstrate that the concept of diffraction before destruction extends to single proteins. From the pattern, it is possible to determine the approximate orientation of the protein. Our experiment demonstrates the feasibility of ultrafast imaging of single proteins, opening the way to single-molecule time-resolved studies on the femtosecond timescale.
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| 7. |
- Khubbutdinov, Ruslan, et al.
(författare)
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High spatial coherence and short pulse duration revealed by the Hanbury Brown and Twiss interferometry at the European XFEL
- 2021
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Ingår i: Structural Dynamics. - : American Institute of Physics (AIP). - 2329-7778. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- Second-order intensity interferometry was employed to study the spatial and temporal properties of the European X-ray Free-Electron Laser (EuXFEL). Measurements were performed at the soft x-ray Self-Amplified Spontaneous Emission (SASE3) undulator beamline at a photon energy of 1.2 keV in the Self-Amplified Spontaneous Emission (SASE) mode. Two high-power regimes of the SASE3 undulator settings, i.e., linear and quadratic undulator tapering at saturation, were studied in detail and compared with the linear gain regime. The statistical analysis showed an exceptionally high degree of spatial coherence up to 90% for the linear undulator tapering. Analysis of the measured data in spectral and spatial domains provided an average pulse duration of about 10 fs in our measurements. The obtained results will be valuable for the experiments requiring and exploiting short pulse duration and utilizing high coherence properties of the EuXFEL.
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