| 1. |
- Zhou Hagström, Nanna, 1993-, et al.
(författare)
-
Megahertz-rate ultrafast X-ray scattering and holographic imaging at the European XFEL
- 2022
-
Ingår i: Journal of Synchrotron Radiation. - : International Union of Crystallography (IUCr). - 0909-0495 .- 1600-5775. ; 29, s. 1454-1464
-
Tidskriftsartikel (refereegranskat)abstract
- The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, from chemistry to biology, giving researchers access to X-rays with unprecedented brightness, coherence and pulse duration. All XFEL facilities built until recently provided X-ray pulses at a relatively low repetition rate, with limited data statistics. Here, results from the first megahertz-repetition-rate X-ray scattering experiments at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL are presented. The experimental capabilities that the SCS instrument offers, resulting from the operation at megahertz repetition rates and the availability of the novel DSSC 2D imaging detector, are illustrated. Time-resolved magnetic X-ray scattering and holographic imaging experiments in solid state samples were chosen as representative, providing an ideal test-bed for operation at megahertz rates. Our results are relevant and applicable to any other non-destructive XFEL experiments in the soft X-ray range.
|
|
| 2. |
- Aprojanz, J., et al.
(författare)
-
High-Mobility Epitaxial Graphene on Ge/Si(100) Substrates
- 2020
-
Ingår i: ACS applied materials & interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:38, s. 43065-43072
-
Tidskriftsartikel (refereegranskat)abstract
- Graphene was shown to reveal intriguing properties of its relativistic two-dimensional electron gas; however, its implementation to microelectronic applications is missing to date. In this work, we present a comprehensive study of epitaxial graphene on technologically relevant and in a standard CMOS process achievable Ge(100) epilayers grown on Si(100) substrates. Crystalline graphene monolayer structures were grown by means of chemical vapor deposition (CVD). Using angle-resolved photoemission spectroscopy and in situ surface transport measurements, we demonstrate their metallic character both in momentum and real space. Despite numerous crystalline imperfections, e.g., grain boundaries and strong corrugation, as compared to epitaxial graphene on SiC(0001), charge carrier mobilities of 1 × 104 cm2/Vs were obtained at room temperature, which is a result of the quasi-charge neutrality within the graphene monolayers on germanium and not dependent on the presence of an interface oxide. The interface roughness due to the facet structure of the Ge(100) epilayer, formed during the CVD growth of graphene, can be reduced via subsequent in situ annealing up to 850 °C coming along with an increase in the mobility by 30%. The formation of a Ge(100)-(2 × 1) structure demonstrates the weak interaction and effective delamination of graphene from the Ge/Si(100) substrate.
|
|
| 3. |
- Chang, Yun Chien, et al.
(författare)
-
Decrypting lysine deacetylase inhibitor action and protein modifications by dose-resolved proteomics
- 2024
-
Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 43:6
-
Tidskriftsartikel (refereegranskat)abstract
- Lysine deacetylase inhibitors (KDACis) are approved drugs for cutaneous T cell lymphoma (CTCL), peripheral T cell lymphoma (PTCL), and multiple myeloma, but many aspects of their cellular mechanism of action (MoA) and substantial toxicity are not well understood. To shed more light on how KDACis elicit cellular responses, we systematically measured dose-dependent changes in acetylation, phosphorylation, and protein expression in response to 21 clinical and pre-clinical KDACis. The resulting 862,000 dose-response curves revealed, for instance, limited cellular specificity of histone deacetylase (HDAC) 1, 2, 3, and 6 inhibitors; strong cross-talk between acetylation and phosphorylation pathways; localization of most drug-responsive acetylation sites to intrinsically disordered regions (IDRs); an underappreciated role of acetylation in protein structure; and a shift in EP300 protein abundance between the cytoplasm and the nucleus. This comprehensive dataset serves as a resource for the investigation of the molecular mechanisms underlying KDACi action in cells and can be interactively explored online in ProteomicsDB.
|
|
| 4. |
- Ekeberg, Tomas, 1983-, et al.
(författare)
-
Observation of a single protein by ultrafast X-ray diffraction
- 2024
-
Ingår i: Light. - : Springer Nature. - 2095-5545 .- 2047-7538. ; 13:1
-
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.
|
|
| 5. |
- Galeski, S., et al.
(författare)
-
Origin of the quasi-quantized Hall effect in ZrTe 5
- 2021
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- The quantum Hall effect (QHE) is traditionally considered to be a purely two-dimensional (2D) phenomenon. Recently, however, a three-dimensional (3D) version of the QHE was reported in the Dirac semimetal ZrTe . It was proposed to arise from a magnetic-field-driven Fermi surface instability, transforming the original 3D electron system into a stack of 2D sheets. Here, we report thermodynamic, spectroscopic, thermoelectric and charge transport measurements on such ZrTe samples. The measured properties: magnetization, ultrasound propagation, scanning tunneling spectroscopy, and Raman spectroscopy, show no signatures of a Fermi surface instability, consistent with in-field single crystal X-ray diffraction. Instead, a direct comparison of the experimental data with linear response calculations based on an effective 3D Dirac Hamiltonian suggests that the quasi-quantization of the observed Hall response emerges from the interplay of the intrinsic properties of the ZrTe electronic structure and its Dirac-type semi-metallic character.
|
|
| 6. |
|
|
| 7. |
- Porro, M., et al.
(författare)
-
The MiniSDD-Based 1-Mpixel Camera of the DSSC Project for the European XFEL
- 2021
-
Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers Inc.. - 0018-9499 .- 1558-1578. ; 68:6, s. 1334-1350
-
Tidskriftsartikel (refereegranskat)abstract
- The first DSSC 1-Mpixel camera became available at the European XFEL (EuXFEL) in the Hamburg area in February 2019. It was successfully tested, installed, and commissioned at the Spectroscopy and Coherent Scattering Instrument. DSSC is a high-speed, large-area, 2-D imaging detector system optimized for photon science applications in the energy range between 0.25 and 6 keV. The camera is based on direct conversion Si sensors and is composed of 1024 × 1024 pixels of hexagonal shape with a side length of 136∼μm. The 256 application-specific integrated circuits (ASICs) provide full parallel readout, comprising analog filtering, digitization, and in-pixel data storage. In order to cope with the demanding X-ray pulse time structure of the EuXFEL, the DSSC provides a peak frame rate of 4.5 MHz. The first Mpixel camera is equipped with miniaturized silicon drift detector (MiniSDD) pixel arrays. The intrinsic response of the pixels and the linear readout limit the dynamic range but allow one to achieve noise values of about 60 electrons r.m.s. at the highest frame rate. The challenge of providing high-dynamic range (104 photons/pixel/pulse) and single-photon detection simultaneously requires a nonlinear system front end, which will be obtained with the DEPFET active pixel technology foreseen for the advanced version of the camera. This technology will provide lower noise and a nonlinear response at the sensor level. This article describes the architecture of the whole detector system together with the main experimental results achieved up to now. © 1963-2012 IEEE.
|
|
| 8. |
|
|
