| 1. |
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| 2. |
- Aguilar-Calvo, Patricia, et al.
(författare)
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Shortening heparan sulfate chains prolongs survival and reduces parenchymal plaques in prion disease caused by mobile, ADAM10-cleaved prions
- 2020
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Ingår i: Acta Neuropathologica. - : SPRINGER. - 0001-6322 .- 1432-0533. ; 139:3, s. 527-546
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Tidskriftsartikel (refereegranskat)abstract
- Cofactors are essential for driving recombinant prion protein into pathogenic conformers. Polyanions promote prion aggregation in vitro, yet the cofactors that modulate prion assembly in vivo remain largely unknown. Here we report that the endogenous glycosaminoglycan, heparan sulfate (HS), impacts prion propagation kinetics and deposition sites in the brain. Exostosin-1 haploinsufficient (Ext1(+/-)) mice, which produce short HS chains, show a prolonged survival and a redistribution of plaques from the parenchyma to vessels when infected with fibrillar prions, and a modest delay when infected with subfibrillar prions. Notably, the fibrillar, plaque-forming prions are composed of ADAM10-cleaved prion protein lacking a glycosylphosphatidylinositol anchor, indicating that these prions are mobile and assemble extracellularly. By analyzing the prion-bound HS using liquid chromatography-mass spectrometry (LC-MS), we identified the disaccharide signature of HS differentially bound to fibrillar compared to subfibrillar prions, and found approximately 20-fold more HS bound to the fibrils. Finally, LC-MS of prion-bound HS from human patients with familial and sporadic prion disease also showed distinct HS signatures and higher HS levels associated with fibrillar prions. This study provides the first in vivo evidence of an endogenous cofactor that accelerates prion disease progression and enhances parenchymal deposition of ADAM10-cleaved, mobile prions.
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| 3. |
- Sevillano, Alejandro M., et al.
(författare)
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Prion protein glycans reduce intracerebral fibril formation and spongiosis in prion disease
- 2020
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Ingår i: Journal of Clinical Investigation. - : AMER SOC CLINICAL INVESTIGATION INC. - 0021-9738 .- 1558-8238. ; 130:3, s. 1350-1362
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Tidskriftsartikel (refereegranskat)abstract
- Posttranslational modifications (PTMs) are common among proteins that aggregate in neurodegenerative disease, yet how PTMs impact the aggregate conformation and disease progression remains unclear. By engineering knockin mice expressing prion protein (PrP) lacking 2 N-linked glycans (Prnp(1)(80Q)(/196Q)), we provide evidence that glycans reduce spongiform degeneration and hinder plaque formation in prion disease.Prnp(1)(80Q)(/196Q )mice challenged with 2 subfibrillar, non-plaque-forming prion strains instead developed plaques highly enriched in ADAM10-cleaved PrP and heparan sulfate (HS). Intriguingly, a third strain composed of intact, glycophosphatidylinositol-anchored (GPI-anchored) PrP was relatively unchanged, forming diffuse, HS-deficient deposits in both the Prnp(1)(80Q/196Q) and WT mice, underscoring the pivotal role of the GPI-anchor in driving the aggregate conformation and disease phenotype. Finally, knockin mice expressing triglycosylated PrP (Prnp(187N)) challenged with a plaque-forming prion strain showed a phenotype reversal, with a striking disease acceleration and switch from plaques to predominantly diffuse, subfibrillar deposits. Our findings suggest that the dominance of subfibrillar aggregates in prion disease is due to the replication of GPI-anchored prions, with fibrillar plaques forming from poorly glycosylated, GPI-anchorless prions that interact with extracellular HS. These studies provide insight into how PTMs impact PrP interactions with polyanionic cofactors, and highlight PTMs as a major force driving the prion disease phenotype.
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| 4. |
- Alonso-Mori, Roberto, et al.
(författare)
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Energy-dispersive X-ray emission spectroscopy using an X-ray free-electron laser in a shot-by-shot mode
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:47, s. 19103-19107
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Tidskriftsartikel (refereegranskat)abstract
- The ultrabright femtosecond X-ray pulses provided by X-ray free-electron lasers open capabilities for studying the structure and dynamics of a wide variety of systems beyond what is possible with synchrotron sources. Recently, this probe-before-destroy approach has been demonstrated for atomic structure determination by serial X-ray diffraction of microcrystals. There has been the question whether a similar approach can be extended to probe the local electronic structure by X-ray spectroscopy. To address this, we have carried out femtosecond X-ray emission spectroscopy (XES) at the Linac Coherent Light Source using redox-active Mn complexes. XES probes the charge and spin states as well as the ligand environment, critical for understanding the functional role of redox-active metal sites. K beta(1,3) XES spectra of Mn-II and Mn-2(III,IV) complexes at room temperature were collected using a wavelength dispersive spectrometer and femtosecond X-ray pulses with an individual dose of up to > 100 MGy. The spectra were found in agreement with undamaged spectra collected at low dose using synchrotron radiation. Our results demonstrate that the intact electronic structure of redox active transition metal compounds in different oxidation states can be characterized with this shot-by-shot method. This opens the door for studying the chemical dynamics of metal catalytic sites by following reactions under functional conditions. The technique can be combined with X-ray diffraction to simultaneously obtain the geometric structure of the overall protein and the local chemistry of active metal sites and is expected to prove valuable for understanding the mechanism of important metalloproteins, such as photosystem II.
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| 5. |
- Bruns, F, et al.
(författare)
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Complementary and alternative medicine experience in radiation oncology patients : first results of a multi-center approach
- 2006
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Ingår i: Trace elements and electrolytes. - 0946-2104. ; 23:4, s. 318-325
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Tidskriftsartikel (refereegranskat)abstract
- In recent years the demand and use of complementary and alternative medicine (CAM) in malignant diseases has increased noticeably. Since the general knowledge about CAM use is scant and CAM could potentially interact with standard therapies the German Working group “Trace Elements and Electrolytes in Oncology” performed a multi-centric study to comprehensively evaluate the use of CAM therapies in cancer patients treated with radiotherapy. Methods: 1,013 patients receiving consecutively radiotherapy for malignant diseases were interviewed using a standardized questionnaire including clinical and pathological tumor parameters as well as the type of CAM and reasons for CAM use. A self-assessment of patients’ personal conditions was performed in order to evaluate the subjective impact of CAM on quality of life. Results: A total of 59% of patients reported using CAM therapies. CAM use was more common in female patients, generally higher in advanced stages of disease and most common in breast cancer patients. Most frequently reported CAM therapies were vitamins (18%), mistletoe extracts (15%), selenium (10%), and other trace element preparations (7%). Multivariate logistic regression showed age, gender, tumor type and stage, and smoking behavior to be significant predictors for CAM use. A subjective improvement in quality of life due to the use of CAM was accounted for in 30% of patients. Conclusions: More than half of patients undergoing RT for cancer are using CAM therapies. Therefore, radiation oncologists should be asking for respective obtaining information about CAM use in order to avoid harmful interactions with conventional therapies. The value and potential hazards of such combined treatments have yet to be tested in further clinical studies.
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| 6. |
- Hattne, Johan, et al.
(författare)
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Accurate macromolecular structures using minimal measurements from X-ray free-electron lasers
- 2014
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Ingår i: Nature Methods. - 1548-7091 .- 1548-7105. ; 11:5, s. 545-548
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Tidskriftsartikel (refereegranskat)abstract
- X-ray free-electron laser (XFEL) sources enable the use of crystallography to solve three-dimensional macromolecular structures under native conditions and without radiation damage. Results to date, however, have been limited by the challenge of deriving accurate Bragg intensities from a heterogeneous population of microcrystals, while at the same time modeling the X-ray spectrum and detector geometry. Here we present a computational approach designed to extract meaningful high-resolution signals from fewer diffraction measurements.
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| 7. |
- Hattne, Johan, et al.
(författare)
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Accurate macromolecular structures using minimal measurements from X-ray free-electron lasers
- 2014
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Ingår i: Nature Methods. - : Springer Science and Business Media LLC. - 1548-7091 .- 1548-7105. ; 11:5, s. 545-548
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Tidskriftsartikel (refereegranskat)abstract
- X-ray free-electron laser (XFEL) sources enable the use of crystallography to solve three-dimensional macromolecular structures under native conditions and without radiation damage. Results to date, however, have been limited by the challenge of deriving accurate Bragg intensities from a heterogeneous population of microcrystals, while at the same time modeling the X-ray spectrum and detector geometry. Here we present a computational approach designed to extract meaningful high-resolution signals from fewer diffraction measurements.
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| 8. |
- Kawde, Anurag Y., 1984-
(författare)
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Advanced silicon photoelectrodes for water splitting devices : design, preparation and functional characterization by photo-electrochemistry and high-energy X-ray spectroscopy
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For the last century, mankind has been hugely dependent on fossil fuels to meet its energy needs. Harnessing energy from fossil fuels led to the emission of greenhouse gases. Greenhouse gases such as CO2 are a major contributor to global warming. Since the last decade, the global annual average temperature has increased by almost 1 oC, while the annual average temperature of Europe has increased by almost 1.7 oC. It is high time to find an alternative source of energy. Such an energy source must be renewable, sustainable, robust and free of greenhouse gases. Our earth has a non-stop supply of solar energy and water in oceans, harvesting energies from such resources will not only be clean but also inexpensive. Solar fuels such as H2 generated from sunlight and seawater using earth-abundant materials are expected to be a crucial component of a next generation renewable energy mix.My PhD research was thus focused on the use of solar energy to split water into molecular hydrogen and oxygen, a process that is referred to as ‘artificial photosynthesis’. This can be achieved with the help of semiconductor photocatalysts. As most of the earth crust has a high abundance of silicon (Si), I prepared my semiconductor photoelectrodes using Si. However, Si tends to degrade in an aqueous environment. Thus, my PhD research comprises the synthesis of microstructured Si photoelectrodes and their protection with a TiO2 inter layer followed by functionalization with various earth abundant co-catalysts. The study on the synthesis, morphology and elemental characterization of the photoelectrodes was carried out under the supervision of Prof. Dr. Johannes Messinger at the Chemistry Department of Umeå University. Deep insight on the electronic and atomic structure of the functionalized Si photoelectrodes was obtained by careful experiments at the European Synchrotron Radiation Facility (ESRF) under the supervision of Dr. Pieter Glatzel. I investigated the electronic and geometric structural properties of my photocatalysts using inner shell electron spectroscopy, which is also referred to as ‘X-ray spectroscopy’. Thus, my PhD thesis falls under the broad title of “Artificial Photosynthesis and X-Ray Spectroscopy”. With the motivation of developing a bias free photoelectrochemical device for overall water splitting, I first developed cost effective earth abundant photocathodes. The experimental data and detailed analysis of the photocathodes are presented in Paper I. The best photocathode obtained in Paper I (p-Si/TiO2/NiOx) was then coupled with a well-studied FTO/α-Fe2O3 photoanode in parallel-illumination mode. The two most significant information obtained in Paper II were: 1) p-Si/TiO2/NiOx outcompetes Pt as a counter electrode and 2) a space charge region in the pristine hematite can be enhanced using p-Si/TiO2/NiOx as photocathode without bias or using any dopant. The proof of concept device studied in Paper II was further optimized in Paper III by replacing the FTO substrate with the n-Si MW to a obtain n-Si MW/TiO2/α-Fe2O3 photoanode. A record high photocurrent density of 5.6 mA/cm2 was achieved for the undoped hematite photoanode. I also found out that the TiO2 inter layer plays a crucial role in enhancing the overall device performance. The role of TiO2 was thus further studied using valence to core X-ray emission spectroscopy, which opened a new avenue for identifying and investigating the prime components in such devices. Paper I to III discuss the role of TiO2 and of the co-catalysts towards solar water splitting and thus the only material left to study was the Si substrate. For paper IV, a detailed analysis on Si substrate was performed. The electronic structural changes on Si LII, III edge was studied using X-ray Raman spectroscopy. The X-ray spectroscopic studies presented in papers I to III were performed at the ID-26 beamline at ESRF, while the X-ray Raman Spectroscopy presented in Paper IV was performed at the ID-20 beamline at ESRF. The data presented in Paper IV is preliminary and needs to be processed and analyzed further.
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| 9. |
- Kern, Jan, et al.
(författare)
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Room temperature femtosecond X-ray diffraction of photosystem II microcrystals
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:25, s. 9721-9726
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Tidskriftsartikel (refereegranskat)abstract
- Most of the dioxygen on earth is generated by the oxidation of water by photosystem II (PS II) using light from the sun. This lightdriven, four-photon reaction is catalyzed by the Mn4CaO5 cluster located at the lumenal side of PS II. Various X-ray studies have been carried out at cryogenic temperatures to understand the intermediate steps involved in the water oxidation mechanism. However, the necessity for collecting data at room temperature, especially for studying the transient steps during the O-O bond formation, requires the development of new methodologies. In this paper we report room temperature X-ray diffraction data of PS II microcrystals obtained using ultrashort (<50 fs) 9 keV X-ray pulses from a hard X-ray free electron laser, namely the Linac Coherent Light Source. The results presented here demonstrate that the probe before destroy approach using an X-ray free electron laser works even for the highly-sensitive Mn4CaO5 cluster in PS II at room temperature. We show that these data are comparable to those obtained in synchrotron radiation studies as seen by the similarities in the overall structure of the helices, the protein subunits and the location of the various cofactors. This work is, therefore, an important step toward future studies for resolving the structure of the Mn4CaO5 cluster without any damage at room temperature, and of the reaction intermediates of PS II during O-O bond formation.
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| 10. |
- Kern, Jan, et al.
(författare)
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Simultaneous Femtosecond X-ray Spectroscopy and Diffraction of Photosystem II at Room Temperature
- 2013
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 340:6131, s. 491-495
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Tidskriftsartikel (refereegranskat)abstract
- Intense femtosecond x-ray pulses produced at the Linac Coherent Light Source (LCLS) were used for simultaneous x-ray diffraction (XRD) and x-ray emission spectroscopy (XES) of microcrystals of photosystem II (PS II) at room temperature. This method probes the overall protein structure and the electronic structure of the Mn4CaO5 cluster in the oxygen-evolving complex of PS II. XRD data are presented from both the dark state (S-1) and the first illuminated state (S-2) of PS II. Our simultaneous XRD-XES study shows that the PS II crystals are intact during our measurements at the LCLS, not only with respect to the structure of PS II, but also with regard to the electronic structure of the highly radiation-sensitive Mn4CaO5 cluster, opening new directions for future dynamics studies.
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