| 1. |
- Abelev, Betty, et al.
(författare)
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Long-range angular correlations on the near and away side in p-Pb collisions at root S-NN=5.02 TeV
- 2013
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < P-T,P-assoc < P-T,P-trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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| 2. |
- Abelev, Betty, et al.
(författare)
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Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :11
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.
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| 3. |
- Abelev, Betty, et al.
(författare)
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Underlying Event measurements in pp collisions at root s=0.9 and 7 TeV with the ALICE experiment at the LHC
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :7
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.
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| 4. |
- Agardh, Emilie E., et al.
(författare)
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Disease Burden Attributed to Drug use in the Nordic Countries : a Systematic Analysis for the Global Burden of Diseases, Injuries, and Risk Factors Study 2019
- 2023
-
Ingår i: International Journal of Mental Health and Addiction. - 1557-1874 .- 1557-1882.
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Tidskriftsartikel (refereegranskat)abstract
- The Nordic countries share similarities in many social and welfare domains, but drug policies have varied over time and between countries. We wanted to compare differences in mortality and disease burden attributed to drug use over time. Using results from the Global Burden of Disease (GBD) study, we extracted age-standardized estimates of deaths, DALYs, YLLs and YLDs per 100 000 population for Denmark, Finland, Iceland, Norway, and Sweden during the years 1990 to 2019. Among males, DALY rates in 2019 were highest in Finland and lowest in Iceland. Among females, DALY rates in 2019 were highest in Iceland and lowest in Sweden. Sweden have had the highest increase in burden since 1990, from 252 DALYs to 694 among males, and from 111 to 193 among females. Norway had a peak with highest level of all countries in 2001-2004 and thereafter a strong decline. Denmark have had the most constant burden over time, 566-600 DALYs among males from 1990 to 2010 and 210-240 DALYs among females. Strict drug policies in Nordic countries have not prevented an increase in some countries, so policies need to be reviewed.
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| 5. |
- Aronsson, Christopher, et al.
(författare)
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Dynamic peptide-folding mediated biofunctionalization and modulation of hydrogels for 4D bioprinting
- 2020
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Ingår i: Biofabrication. - : Institute of Physics Publishing (IOPP). - 1758-5082 .- 1758-5090. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogels are used in a wide range of biomedical applications, including three-dimensional (3D) cell culture, cell therapy and bioprinting. To enable processing using advanced additive fabrication techniques and to mimic the dynamic nature of the extracellular matrix (ECM), the properties of the hydrogels must be possible to tailor and change over time with high precision. The design of hydrogels that are both structurally and functionally dynamic, while providing necessary mechanical support is challenging using conventional synthesis techniques. Here, we show a modular and 3D printable hydrogel system that combines a robust but tunable covalent bioorthogonal cross-linking strategy with specific peptide-folding mediated interactions for dynamic modulation of cross-linking and functionalization. The hyaluronan-based hydrogels were covalently cross-linked by strain-promoted alkyne-azide cycloaddition using multi-arm poly(ethylene glycol). In addition, a de novo designed helix-loop-helix peptide was conjugated to the hyaluronan backbone to enable specific peptide-folding modulation of cross-linking density and kinetics, and hydrogel functionality. An array of complementary peptides with different functionalities was developed and used as a toolbox for supramolecular tuning of cell-hydrogel interactions and for controlling enzyme-mediated biomineralization processes. The modular peptide system enabled dynamic modifications of the properties of 3D printed structures, demonstrating a novel route for design of more sophisticated bioinks for four-dimensional bioprinting. © 2020 The Author(s). Published by IOP Publishing Ltd.
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| 6. |
- Aronsson, Christopher, et al.
(författare)
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Self-sorting heterodimeric coiled coil peptides with defined and tuneable self-assembly properties
- 2015
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 5:14063
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Tidskriftsartikel (refereegranskat)abstract
- Coiled coils with defined assembly properties and dissociation constants are highly attractive components in synthetic biology and for fabrication of peptide-based hybrid nanomaterials and nanostructures. Complex assemblies based on multiple different peptides typically require orthogonal peptides obtained by negative design. Negative design does not necessarily exclude formation of undesired species and may eventually compromise the stability of the desired coiled coils. This work describe a set of four promiscuous 28-residue de novo designed peptides that heterodimerize and fold into parallel coiled coils. The peptides are non-orthogonal and can form four different heterodimers albeit with large differences in affinities. The peptides display dissociation constants for dimerization spanning from the micromolar to the picomolar range. The significant differences in affinities for dimerization make the peptides prone to thermodynamic social self-sorting as shown by thermal unfolding and fluorescence experiments, and confirmed by simulations. The peptides self-sort with high fidelity to form the two coiled coils with the highest and lowest affinities for heterodimerization. The possibility to exploit self-sorting of mutually complementary peptides could hence be a viable approach to guide the assembly of higher order architectures and a powerful strategy for fabrication of dynamic and tuneable nanostructured materials.
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| 7. |
- Aronsson, Christopher
(författare)
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Tunable and modular assembly of polypeptides and polypeptide-hybrid biomaterials
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biomaterials are materials that are specifically designed to be in contact with biological systems and have for a long time been used in medicine. Examples of biomaterials range from sophisticated prostheses used for replacing outworn body parts to ordinary contact lenses. Currently it is possible to create biomaterials that can e.g. specifically interact with cells or respond to certain stimuli. Peptides, the shorter version of proteins, are excellent molecules for fabrication of such biomaterials. By following and developing design rules it is possible to obtain peptides that can self-assemble into well-defined nanostructures and biomaterials.The aim of this thesis is to create ”smart” and tunable biomaterials by molecular self-assembly using dimerizing –helical polypeptides. Two different, but structurally related, polypeptide-systems have been used in this thesis. The EKIV-polypeptide system was developed in this thesis and consists of four 28-residue polypeptides that can be mixed-and-matched to self-assemble into four different coiled coil heterodimers. The dissociation constant of the different heterodimers range from μM to < nM. Due to the large difference in affinities, the polypeptides are prone to thermodynamic social self-sorting. The JR-polypeptide system, on the other hand, consists of several 42-residue de novo designed helix-loop-helix polypeptides that can dimerize into four-helix bundles. In this work, primarily the glutamic acid-rich polypeptide JR2E has been explored as a component in supramolecular materials. Dimerization was induced by exposing the polypeptide to either Zn2+, acidic conditions or the complementary polypeptide JR2K.By conjugating JR2E to hyaluronic acid and the EKIV-polypeptides to star-shaped poly(ethylene glycol), respectively, highly tunable hydrogels that can be self-assembled in a modular fashion have been created. In addition, self-assembly of spherical superstructures has been investigated and were obtained by linking two thiol-modified JR2E polypeptides via a disulfide bridge in the loop region. ŒThe thesis also demonstrates that the polypeptides and the polypeptide-hybrids can be used for encapsulation and release of molecules and nanoparticles. In addition, some of the hydrogels have been explored for 3D cell culture. By using supramolecular interactions combined with bio-orthogonal covalent crosslinking reactions, hydrogels were obtained that enabled facile encapsulation of cells that retained high viability.The results of the work presented in this thesis show that dimerizing α–helical polypeptides can be used to create modular biomaterials with properties that can be tuned by specific molecular interactions. The modularity and the tunable properties of these smart biomaterials are conceptually very interesting andmake them useful in many emerging biomedical applications, such as 3D cell culture, cell therapy, and drug delivery.
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| 8. |
- Aronsson, Christopher, et al.
(författare)
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Zinc-Triggered Hierarchical Self-Assembly of Fibrous Helix-Loop-Helix Peptide Superstructures for Controlled Encapsulation and Release
- 2016
-
Ingår i: Macromolecules. - : AMER CHEMICAL SOC. - 0024-9297 .- 1520-5835. ; 49:18, s. 6997-7003
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a novel route for hierarchical self-assembly of sub-micrometer-sized peptide superstructures that respond to subtle changes in Zn2+ concentration. The self-assembly process is triggered by a specific folding-dependent coordination of Zn2+ by a de novo designed nonlinear helix-loop-helix peptide, resulting in a propagating fiber formation and formation of spherical superstructures. The superstructures further form larger assemblies that can be completely disassembled upon removal of Zn2+ or degradation of the nonlinear peptide. This flexible and reversible assembly strategy of the superstructures enables facile encapsulation of nanoparticles and drugs that can be released by means of different stimuli.
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| 9. |
- Broekman, Maarten J. E., et al.
(författare)
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Evaluating expert-based habitat suitability information of terrestrial mammals with GPS-tracking data
- 2022
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 31:8, s. 1526-1541
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Macroecological studies that require habitat suitability data for many species often derive this information from expert opinion. However, expert-based information is inherently subjective and thus prone to errors. The increasing availability of GPS tracking data offers opportunities to evaluate and supplement expert-based information with detailed empirical evidence. Here, we compared expert-based habitat suitability information from the International Union for Conservation of Nature (IUCN) with habitat suitability information derived from GPS-tracking data of 1,498 individuals from 49 mammal species.Location: Worldwide.Time period: 1998-2021.Major taxa studied: Forty-nine terrestrial mammal species.Methods: Using GPS data, we estimated two measures of habitat suitability for each individual animal: proportional habitat use (proportion of GPS locations within a habitat type), and selection ratio (habitat use relative to its availability). For each individual we then evaluated whether the GPS-based habitat suitability measures were in agreement with the IUCN data. To that end, we calculated the probability that the ranking of empirical habitat suitability measures was in agreement with IUCN's classification into suitable, marginal and unsuitable habitat types.Results: IUCN habitat suitability data were in accordance with the GPS data (> 95% probability of agreement) for 33 out of 49 species based on proportional habitat use estimates and for 25 out of 49 species based on selection ratios. In addition, 37 and 34 species had a > 50% probability of agreement based on proportional habitat use and selection ratios, respectively.Main conclusions: We show how GPS-tracking data can be used to evaluate IUCN habitat suitability data. Our findings indicate that for the majority of species included in this study, it is appropriate to use IUCN habitat suitability data in macroecological studies. Furthermore, we show that GPS-tracking data can be used to identify and prioritize species and habitat types for re-evaluation of IUCN habitat suitability data.
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| 10. |
- Christoffersson, Jonas, 1986-, et al.
(författare)
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Fabrication of modular hyaluronan-PEG hydrogels to support 3D cultures of hepatocytes in a perfused liver-on-a-chip device
- 2019
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Ingår i: Biofabrication. - : Institute of Physics (IOP). - 1758-5082 .- 1758-5090. ; 11:1, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Liver cell culture models are attractive in both tissue engineering and for development of assays for drug toxicology research. To retain liver specific cell functions, the use of adequate cell types and culture conditions, such as a 3D orientation of the cells and a proper supply of nutrients and oxygen, are critical. In this article, we show how extracellular matrix mimetic hydrogels can support hepatocyte viability and functionality in a perfused liver-on-a-chip device. A modular hydrogel system based on hyaluronan and poly(ethylene glycol) (HA-PEG), modified with cyclooctyne moieties for bioorthogonal strain-promoted alkyne-azide 1, 3-dipolar cycloaddition (SPAAC), was developed, characterized, and compared for cell compatibility to hydrogels based on agarose and alginate. Hepatoma cells (HepG2) formed spheroids with viable cells in all hydrogels with the highest expression of albumin and urea in alginate hydrogels. By including an excess of cyclooctyne in the HA backbone, azide-modified cell adhesion motifs (linear and cyclic RGD peptides) could be introduced in order to enhance viability and functionality of human induced pluripotent stem cell derived hepatocytes (hiPS-HEPs). In the HA-PEG hydrogels modified with cyclic RGD peptides hiPS-HEPs migrated and grew in 3D and showed an increased viability and higher albumin production compared to when cultured in the other hydrogels. This flexible SPAAC crosslinked hydrogel system enabled fabrication of perfused 3D cell culture of hiPS-HEPs and is a promising material for further development and optimization of liver-on-a-chip devices.
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| 11. |
- Dånmark, Staffan, et al.
(författare)
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Tailoring Supramolecular Peptide-Poly(ethylene glycol) Hydrogels by Coiled Coil Self-Assembly and Self-Sorting
- 2016
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Ingår i: Biomacromolecules. - : AMER CHEMICAL SOC. - 1525-7797 .- 1526-4602. ; 17:6, s. 2260-2267
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Tidskriftsartikel (refereegranskat)abstract
- Physical hydrogels are extensively used in a wide range of biomedical applications. However, different applications require hydrogels with different mechanical and structural properties. Tailoring these properties demands exquisite control over the supramolecular peptides with different affinities for dimerization. Four different mechanical properties of hydrogels using de novo designed coiled coil interactions involved. Here we show that it is possible to control the nonorthogonal peptides, designed to fold into four different coiled coil heterodimers with dissociation constants spanning from mu M to pM, were conjugated to star-shaped 4-arm poly(ethylene glycol) (PEG). The different PEG-coiled coil conjugates self-assemble as a result of peptide heterodimerization. Different combinations of PEG peptide conjugates assemble into PEG peptide networks and hydrogels with distinctly different thermal stabilities, supramolecular, and rheological properties, reflecting the peptide dimer affinities. We also demonstrate that it is possible to rationally modulate the self-assembly process by means of thermodynamic self-sorting by sequential additions of nonpegylated peptides. The specific interactions involved in peptide dimerization thus provides means for programmable and reversible self-assembly of hydrogels with precise control over rheological properties, which can significantly facilitate optimization of their overall performance and adaption to different processing requirements and applications.
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| 12. |
- Eskilson, Olof, 1992-, et al.
(författare)
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Self-Assembly of Mechanoplasmonic Bacterial Cellulose-Metal Nanoparticle Composites
- 2020
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlagsgesellschaft. - 1616-301X .- 1616-3028. ; 30:40
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC-NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self-assembly strategy is described for fabrication of complex and well-defined BC-NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self-assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near-field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.
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| 13. |
- Fursatz, Marian, et al.
(författare)
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Functionalization of bacterial cellulose wound dressings with the antimicrobial peptide ε-poly-L-Lysine
- 2018
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Ingår i: Biomedical Materials. - : Institute of Physics Publishing (IOPP). - 1748-6041 .- 1748-605X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Wound dressings based on bacterial cellulose (BC) can form a soft and conformable protective layer that can stimulate wound healing while preventing bacteria from entering the wound. Bacteria already present in the wound can, however, thrive in the moist environment created by the BC dressing which can aggravate the healing process. Possibilities to render the BC antimicrobial without affecting the beneficial structural and mechanical properties of the material would hence be highly attractive. Here we present methods for functionalization of BC with ε-Poly-L-Lysine (ε-PLL), a non-toxic biopolymer with broad-spectrum antimicrobial activity. Low molecular weight ε-PLL was cross-linked in pristine BC membranes and to carboxymethyl cellulose (CMC) functionalized BC using carbodiimide chemistry. The functionalization of BC with ε-PLL inhibited growth of S. epidermidis on the membranes but did not affect the cytocompatibility to cultured human fibroblasts as compared to native BC. The functionalization had no significant effects on the nanofibrous structure and mechanical properties of the BC. The possibility to functionalize BC with ε-PLL is a promising, green and versatile approach to improve the performance of BC in wound care and other biomedical applications.
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| 14. |
- Haghighi, Mona, et al.
(författare)
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A Comparison of Rule-based Analysis with Regression Methods in Understanding the Risk Factors for Study Withdrawal in a Pediatric Study
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Regression models are extensively used in many epidemiological studies to understand the linkage between specific outcomes of interest and their risk factors. However, regression models in general examine the average effects of the risk factors and ignore subgroups with different risk profiles. As a result, interventions are often geared towards the average member of the population, without consideration of the special health needs of different subgroups within the population. This paper demonstrates the value of using rule-based analysis methods that can identify subgroups with heterogeneous risk profiles in a population without imposing assumptions on the subgroups or method. The rules define the risk pattern of subsets of individuals by not only considering the interactions between the risk factors but also their ranges. We compared the rule-based analysis results with the results from a logistic regression model in The Environmental Determinants of Diabetes in the Young (TEDDY) study. Both methods detected a similar suite of risk factors, but the rule-based analysis was superior at detecting multiple interactions between the risk factors that characterize the subgroups. A further investigation of the particular characteristics of each subgroup may detect the special health needs of the subgroup and lead to tailored interventions.
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| 15. |
- Lundgren, Markus, et al.
(författare)
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Analgesic antipyretic use among young children in the TEDDY study : No association with islet autoimmunity
- 2017
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Ingår i: BMC Pediatrics. - : Springer Science and Business Media LLC. - 1471-2431. ; 17:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: The use of analgesic antipyretics (ANAP) in children have long been a matter of controversy. Data on their practical use on an individual level has, however, been scarce. There are indications of possible effects on glucose homeostasis and immune function related to the use of ANAP. The aim of this study was to analyze patterns of analgesic antipyretic use across the clinical centers of The Environmental Determinants of Diabetes in the Young (TEDDY) prospective cohort study and test if ANAP use was a risk factor for islet autoimmunity. Methods: Data were collected for 8542 children in the first 2.5 years of life. Incidence was analyzed using logistic regression with country and first child status as independent variables. Holm's procedure was used to adjust for multiplicity of intercountry comparisons. Time to autoantibody seroconversion was analyzed using a Cox proportional hazards model with cumulative analgesic use as primary time dependent covariate of interest. For each categorization, a generalized estimating equation (GEE) approach was used. Results: Higher prevalence of ANAP use was found in the U.S. (95.7%) and Sweden (94.8%) compared to Finland (78.1%) and Germany (80.2%). First-born children were more commonly given acetaminophen (OR 1.26; 95% CI 1.07, 1.49; p = 0.007) but less commonly Non-Steroidal Anti-inflammatory Drugs (NSAID) (OR 0.86; 95% CI 0.78, 0.95; p = 0.002). Acetaminophen and NSAID use in the absence of fever and infection was more prevalent in the U.S. (40.4%; 26.3% of doses) compared to Sweden, Finland and Germany (p < 0.001). Acetaminophen or NSAID use before age 2.5 years did not predict development of islet autoimmunity by age 6 years (HR 1.02, 95% CI 0.99-1.09; p = 0.27). In a sub-analysis, acetaminophen use in children with fever weakly predicted development of islet autoimmunity by age 3 years (HR 1.05; 95% CI 1.01-1.09; p = 0.024). Conclusions: ANAP use in young children is not a risk factor for seroconversion by age 6 years. Use of ANAP is widespread in young children, and significantly higher in the U.S. compared to other study sites, where use is common also in absence of fever and infection.
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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. |
- Poeplau, Christopher, et al.
(författare)
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Effect of perennial ryegrass cover crop on soil organic carbon stocks in southern Sweden
- 2015
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Ingår i: Geoderma Regional. - : Elsevier BV. - 2352-0094. ; 4, s. 126-133
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Tidskriftsartikel (refereegranskat)abstract
- Soil organic carbon (SOC) is an important ecosystem property and a potential sink for atmospheric CO2. Many agricultural soils are depleted in SOC and thus have the need and potential to sequester carbon. Cover crops used to prevent nitrate leaching in agroecosystems might be an additional cost-effective and multi-beneficial carbon input, but little is known about their effect on SOC stocks. This study examined the effect of an ryegrass cover crop on SOC stocks in three Swedish long-term experiments (16–24years) and compared it with that at a North American site (Sultan, Washington). Growth was temperature- and light-limited in Sweden and thus the ryegrass was undersown, while it was sown after harvest of the main crop at the Sultan site. In total, seven pairs of cover crop/no cover crop treatments were investigated. The introductory carbon balance model (ICBM) was used to calculate humification coefficients for ryegrass at each site as a measure of carbon sequestration efficiency. Mean aboveground biomass of ryegrass ranged from 550–1050kgDMha−1yr−1in the Swedish experiments and was 4650kgDMha−1yr−1at the Sultan site. Yield of the main crop was not significantly affected by the cover crop. Cover crop incorporation increased SOC stocks, with a significant mean carbon sequestration rate (0.32±0.28MgCha−1yr−1) at the Sultan site and all Swedish sites except one. Mean humification coefficient of the ryegrass cover crop was 0.33±0.27, which is comparable to that of highly efficient organic amendments such as farmyard manure and sewage sludge. This was attributed to high belowground productivity of ryegrass, although that was the most uncertain model input variable. A ryegrass cover crop is thus an effective, multi-beneficial measure to increase SOC stocks, even when undersown at northerly latitudes (55–58°N).
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| 21. |
- Selegård, Robert, et al.
(författare)
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Folding driven self-assembly of a stimuli-responsive peptide-hyaluronan hybrid hydrogel
- 2017
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Protein-metal ion interactions are ubiquitous in nature and can be utilized for controlling the self-assembly of complex supramolecular architectures and materials. Here, a tunable supramolecular hydrogel is described, obtained by self-assembly of a Zn2+-responsive peptide-hyaluronic acid hybrid synthesized using strain promoted click chemistry. Addition of Zn2+ triggers folding of the peptides into a helix-loop-helix motif and dimerization into four-helix bundles, resulting in hydrogelation. Removal of the Zn2+ by chelators results in rapid hydrogel disassembly. Degradation of the hydrogels can also be time-programed by encapsulation of a hydrolyzing enzyme within the gel, offering multiple possibilities for modulating materials properties and release of encapsulated species. The hydrogel further shows potential antioxidant properties when evaluated using an in vitro model for reactive oxygen species.
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| 22. |
- Skyttner, Camilla, et al.
(författare)
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Sequence and length optimization of membrane active coiled coils for triggered liposome release
- 2019
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Ingår i: Biochimica et Biophysica Acta - Biomembranes. - : ELSEVIER SCIENCE BV. - 0005-2736 .- 1879-2642. ; 1862:2, s. 449-456
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Tidskriftsartikel (refereegranskat)abstract
- Defined and tunable peptide-lipid membrane interactions that trigger the release of liposome encapsulated drugs may offer a route to improving the efficiency and specificity of liposome-based drug delivery systems, but this require means to tailor the performance of the membrane active peptides. In this paper, the membrane activity of a de novo designed coiled coil peptide has been optimized with respect to sequence and size to improve release efficiency of liposome encapsulated cargo. The peptides were only membrane active when covalently conjugated to the liposomes. Two amino acid substitutions were made to enhance the amphipathic characteristics of the peptide, which increased the release by a factor of five at 1 mu M. Moreover, the effect of peptide length was investigated by varying the number of heptad repeats from 2 to 5, yielding the peptides KVC2-KVC5. The shortest peptide (KVC2) showed the least interaction with the membrane and proved less efficient than the longer peptides in releasing the liposomal cargo. The peptide with three heptads (KVC3) caused liposome aggregation whereas KVC4 proved to effectively release the liposomal cargo without causing aggregation. The longest peptide (KVC5) demonstrated the most defined a-helical secondary structure and the highest liposome surface concentration but showed slower release kinetics than KVC4. The four heptad peptide KVC4 consequently displayed optimal properties for triggering the release and is an interesting candidate for further development of bioresponsive and tunable liposomal drug delivery systems.
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| 23. |
- Skyttner, Camilla, et al.
(författare)
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Tuning Liposome Membrane Permeability by Competitive Coiled Coil Heterodimerization and Heterodimer Exchange
- 2018
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Ingår i: Langmuir. - : AMER CHEMICAL SOC. - 0743-7463 .- 1520-5827. ; 34:22, s. 6529-6537
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Tidskriftsartikel (refereegranskat)abstract
- Membrane-active peptides that enable the triggered release of liposomal cargo are of great interest for the development of liposome-based drug delivery systems but require peptide-lipid membrane interactions that are highly defined and tunable. To this end, we have explored the possibility to use the competing interactions between membrane partitioning and heterodimenzation and the folding of a set of four different de novo designed coiled coil peptides Covalent conjugation of the cationic peptides triggered rapid destabilization of membrane mtegrity and the release of encapsulated species. The release was inhibited when introducing complementary peptides as a result of heterodimenzation and folding into coiled mils The degree of inhibition was shown to be dictated by the coiled coil peptide heterodimer dissociation constants, and liposomal release could be reactivated by a heterodimer exchange to render the membrane bound peptide free and thus membrane-active. The possibility to tune the permeability of lipid membranes using highly specific peptide-folding-dependent interactions delineates a new possible approach for the further development of responsive liposome-based drug delivery systems.
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| 24. |
- Thomas, Rimon, et al.
(författare)
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Natural radioactivity in a former mining lake in Central Sweden
- 2016
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Ingår i: SweRays Workshop, Stockholm, Sweden, Aug 25-26.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Historically Sweden (the major metal mining country in the European Union), with more than 2700 mines, gathers around 30000 sites that have been minor mines and/or quarries (according to the database of Geological Survey of Sweden, SGU). This huge activity has implied enormous quantities of generated mining wastes, considered, in some cases NORM (Naturally Ocurring Radioactive Material). In this work, one former mine lake nearby Kolsva (in Västmanland) was radiometrically characterized. Water samples from the pit lake, sediment and soil/rock samples were measured via alpha (for 238U, 234U, 232Th and 230Th isotopes) and via gamma spectrometry (for radionuclides belonging to both 238U and 232Th natural series). Also measurement of elementary composition in water (via ICP-MS) and in sediments (via XRF) was carried out. Regarding 238U isotopes, for instance, 100 to 600 mBq/kg were found in water samples. Having into account that an average value of this isotope in non-affecting environmental waters is around 20-30 mBq/kg it is quite clear that this site has enhanced U levels in superficial waters. These moderated levels in natural radionuclides were also confirmed in some rocks from this site with values above 1Bq/g in natural radionuclides from 238U series. The found activity concentration values will contribute to increase the external doses received by people visiting these sites for recreation (swimming, fishing, diving) purposes. Keywords: Natural radionuclides, environmental samples, mining lakes
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