| 1. |
- Abraham, Elena T., et al.
(författare)
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Collagen's primary structure determines collagen:HSP47 complex stoichiometry
- 2021
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Ingår i: Journal of Biological Chemistry. - : Elsevier BV. - 0021-9258. ; 297:6
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Tidskriftsartikel (refereegranskat)abstract
- Collagens play important roles in development and homeostasis in most higher organisms. In order to function, collagens require the specific chaperone HSP47 for proper folding and secretion. HSP47 is known to bind to the collagen triple helix, but the exact positions and numbers of binding sites are not clear. Here, we employed a collagen II peptide library to characterize high-affinity binding sites for HSP47. We show that many previously predicted binding sites have very low affinities due to the presence of a negatively charged amino acid in the binding motif. In contrast, large hydrophobic amino acids such as phenylalanine at certain positions in the collagen sequence increase binding strength. For further characterization, we determined two crystal structures of HSP47 bound to peptides containing phenylalanine or leucine. These structures deviate significantly from previously published ones in which different collagen sequences were used. They reveal local conformational rearrangements of HSP47 at the binding site to accommodate the large hydrophobic side chain from the middle strand of the collagen triple helix and, most surprisingly, possess an altered binding stoichiometry in the form of a 1:1 complex. This altered stoichiometry is explained by steric collisions with the second HSP47 molecule present in all structures determined thus far caused by the newly introduced large hydrophobic residue placed on the trailing strand. This exemplifies the importance of considering all three sites of homotrimeric collagen as independent interaction surfaces and may provide insight into the formation of higher oligomeric complexes at promiscuous collagen-binding sites.
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| 2. |
- Koutsouflakis, Emmanouil, et al.
(författare)
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Metamagnetic transition and a loss of magnetic hysteresis caused by electron trapping in monolayers of single-molecule magnet Tb2@C79N
- 2022
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 14:27, s. 9877-9892
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Tidskriftsartikel (refereegranskat)abstract
- Realization of stable spin states in surface-supported magnetic molecules is crucial for their applications in molecular spintronics, memory storage or quantum information processing. In this work, we studied the surface magnetism of dimetallo-azafullerene Tb2@C79N, showing a broad magnetic hysteresis in a bulk form. Surprisingly, monolayers of Tb2@C79N exhibited a completely different behavior, with the prevalence of a ground state with antiferromagnetic coupling at low magnetic field and a metamagnetic transition in the magnetic field of 2.5-4 T. Monolayers of Tb2@C79N were deposited onto Cu(111) and Au(111) by evaporation in ultra-high vacuum conditions, and their topography and electronic structure were characterized by scanning tunneling microscopy and spectroscopy (STM/STS). X-ray photoelectron spectroscopy (XPS), in combination with DFT studies, revealed that the nitrogen atom of the azafullerene cage tends to avoid metallic surfaces. Magnetic properties of the (sub)monolayers were then studied by X-ray magnetic circular dichroism (XMCD) at the Tb-M4,5 absorption edge. While in bulk powder samples Tb2@C79N behaves as a single-molecule magnet with ferromagnetically coupled magnetic moments and blocking of magnetization at 28 K, its monolayers exhibited a different ground state with antiferromagnetic coupling of Tb magnetic moments. To understand if this unexpected behavior is caused by a strong hybridization of fullerenes with metallic substrates, XMCD measurements were also performed for Tb2@C79N adsorbed on h-BN|Rh(111) and MgO|Ag(100). The co-existence of two forms of Tb2@C79N was found on these substrates as well, but magnetization curves showed narrow magnetic hysteresis detectable up to 25 K. The non-magnetic state of Tb2@C79N in monolayers is assigned to anionic Tb2@C79N− species with doubly-occupied Tb-Tb bonding orbital and antiferromagnetic coupling of the Tb moments. A charge transfer from the substrate or trapping of secondary electrons are discussed as a plausible origin of these species.
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| 3. |
- Lotze, Heike K., et al.
(författare)
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Global ensemble projections reveal trophic amplification of ocean biomass declines with climate change
- 2019
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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. ; 116:26, s. 12907-12912
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Tidskriftsartikel (refereegranskat)abstract
- While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web. Without fishing, mean global animal biomass decreased by 5% (+/- 4% SD) under low emissions and 17% (+/- 11% SD) under high emissions by 2100, with an average 5% decline for every 1 degrees C of warming. Projected biomass declines were primarily driven by increasing temperature and decreasing primary production, and were more pronounced at higher trophic levels, a process known as trophic amplification. Fishing did not substantially alter the effects of climate change. Considerable regional variation featured strong biomass increases at high latitudes and decreases at middle to low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to variations in marine ecosystem and Earth system models were similar. Ensemble projections performed well compared with empirical data, emphasizing the benefits of multimodel inference to project future outcomes. Our results indicate that global ocean animal biomass consistently declines with climate change, and that these impacts are amplified at higher trophic levels. Next steps for model development include dynamic scenarios of fishing, cumulative human impacts, and the effects of management measures on future ocean biomass trends.
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| 4. |
- Rajaei, Hossein, et al.
(författare)
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Catalogue of the lepidoptera of Iran
- 2023
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Ingår i: Integrative Systematics. - : Stuttgart State Museum of Natural History. - 2628-2380. ; 6:SP1, s. 121-459
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Tidskriftsartikel (refereegranskat)
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| 5. |
- Schewe, Jacob, et al.
(författare)
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State-of-the-art global models underestimate impacts from climate extremes
- 2019
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Global impact models represent process-level understanding of how natural and human systems may be affected by climate change. Their projections are used in integrated assessments of climate change. Here we test, for the first time, systematically across many important systems, how well such impact models capture the impacts of extreme climate conditions. Using the 2003 European heat wave and drought as a historical analogue for comparable events in the future, we find that a majority of models underestimate the extremeness of impacts in important sectors such as agriculture, terrestrial ecosystems, and heat-related human mortality, while impacts on water resources and hydropower are overestimated in some river basins; and the spread across models is often large. This has important implications for economic assessments of climate change impacts that rely on these models. It also means that societal risks from future extreme events may be greater than previously thought.
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| 6. |
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The Seventeenth Data Release of the Sloan Digital Sky Surveys : Complete Release of MaNGA, MaStar, and APOGEE-2 Data
- 2022
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Ingår i: Astrophysical Journal Supplement Series. - : Institute of Physics (IOP). - 0067-0049 .- 1538-4365. ; 259:2
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Tidskriftsartikel (refereegranskat)abstract
- This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys.
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| 7. |
- Westerström, Rasmus, et al.
(författare)
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Surface Aligned Magnetic Moments and Hysteresis of an Endohedral Single-Molecule Magnet on a Metal
- 2015
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 114:8
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between the endohedral unit in the single-molecule magnet Dy2ScN@C-80 and a rhodium (111) substrate leads to alignment of the Dy 4f orbitals. The resulting orientation of the Dy2ScN plane parallel to the surface is inferred from comparison of the angular anisotropy of x-ray absorption spectra and multiplet calculations in the corresponding ligand field. The x-ray magnetic circular dichroism is also angle dependent and signals strong magnetocrystalline anisotropy. This directly relates geometric and magnetic structure. Element specific magnetization curves from different coverages exhibit hysteresis at a sample temperature of similar to 4 K. From the measured hysteresis curves, we estimate the zero field remanence lifetime during x-ray exposure of a submonolayer to be about 30 seconds.
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