| 11. |
- Jansson, Maria, et al.
(författare)
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Intercalation of cationic peptides within Laponite layered clay minerals in aqueous suspensions : The effect of stoichiometry and charge distance matching
- 2019
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797. ; 557, s. 767-776
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Tidskriftsartikel (refereegranskat)abstract
- Clays can be synthesised to have specific functional properties, which have been exploited in a range of industrial processes. A key characteristic of clay is the presence of a negatively charged surface, surrounded by an oppositely charged rim. Because of that, clays are able to sequester cationic compounds resulting in the formation of ordered layered structures, known as tactoids. Recent research has highlighted the possibility of utilising clay as a drug delivery compound for cationic peptides. Here, we investigate the process of intercalation by using the highly cationic peptide deca-arginine, and the synthetic clay Laponite, in aqueous suspensions with 2.5 wt% Laponite, and varying peptide concentrations. Small-angle X-ray scattering experiments show that tactoids are formed as a function of deca-arginine concentration in the dispersion, and for an excess of peptide, i.e. above a matched charge-ratio between the peptide and clay, the growth of the tactoids is limited, resulting in tactoidal dissolution. Zeta-potential measurements confirm that the observed dissolution is caused by overcharging of the platelets. By employing coarse-grained molecular dynamics simulations based on the continuum model, we are able to predict the tactoid formation, the growth, and the dissolution, in agreement with experimental results. We propose that the present simulation method can be a useful tool to tune peptide and clay characteristics to optimise and determine the extent of intercalation by cationic peptides of therapeutic interest.
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| 12. |
- Jansson, Maria, et al.
(författare)
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The effect of the relative permittivity on the tactoid formation in nanoplatelet systems. A combined computer simulation, SAXS, and osmotic pressure study
- 2018
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797. ; 513, s. 575-584
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Tidskriftsartikel (refereegranskat)abstract
- The structural properties, and the intracrystalline swelling of Na+-, and Ca2+-montmorillonite (Na-, and Ca-mmt) have been investigated as an effect of decreasing the relative permittivity of the solvent, i.e. from water to ethanol (EtOH), utilizing the experimental techniques; small angle X-ray scattering (SAXS) and osmotic pressure measurements. The experimental data were compared with the continuum model, utilizing coarse-grained molecular dynamics bulk simulations, Monte Carlo simulations of two infinite parallel surfaces corresponding to two clay platelets, and the strong coupling theory. It was found that it is possible to tune the electrostatic interactions to obtain a transition from a repulsive to an attractive system for the Na-mmt by increasing the EtOH concentration, i.e. the Bjerrum length increases, and hence, the attractive ion-ion correlation forces are enhanced. A qualitative agreement was observed between the simulations and the experimental results. Moreover, a non-monotonic behavior of the intracrystalline swelling of Ca-mmt as a function of EtOH concentration was captured experimentally, where an increase in the osmotic pressure, and hence, an increase in the d-spacing was found at low concentrations, indicating that repulsive short-ranged interactions dominate in the system. Theoretically, the non-monotonic behavior could not be captured with the continuum model, probably due to the limitation that the electrostatic interactions solely enters the Hamiltonian via the Bjerrum length.
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| 13. |
- Muneer, Faraz, et al.
(författare)
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Nanostructural Morphology of Plasticized Wheat Gluten and Modified Potato Starch Composites: Relationship to Mechanical and Barrier Properties
- 2015
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 16:3, s. 695-705
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, we were able to produce composites of wheat gluten (WG) protein and a novel genetically modified potato starch (MPS) with attractive mechanical and gas barrier properties using extrusion. Characterization of the MPS revealed an altered chain length distribution of the amylopectin fraction and slightly increased amylose content compared to wild type potato starch. WG and MPS of different ratios plasticized with either glycerol or glycerol and water were extruded at 110 and 130 °C. The nanomorphology of the composites showed the MPS having semicrystalline structure of a characteristic lamellar arrangement with an approximately 100 Å period observed by small-angle X-ray scattering and a B-type crystal structure observed by wide-angle X-ray scattering analysis. WG has a structure resembling the hexagonal macromolecular arrangement as reported previously in WG films. A larger amount of β-sheets was observed in the samples 70/30 and 30/70 WG-MPS processed at 130 °C with 45% glycerol. Highly polymerized WG protein was found in the samples processed at 130 °C versus 110 °C. Also, greater amounts of WG protein in the blend resulted in greater extensibility (110 °C) and a decrease in both E-modulus and maximum stress at 110 and 130 °C, respectively. Under ambient conditions the WG-MPS composite (70/30) with 45% glycerol showed excellent gas barrier properties to be further explored in multilayer film packaging applications.
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| 14. |
- Newson, William R., et al.
(författare)
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Commercial potato protein concentrate as a novel source for thermoformed bio-based plastic films with unusual polymerisation and tensile properties
- 2015
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Ingår i: RSC Advances. - 2046-2069. ; 5:41, s. 32217-32226
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Tidskriftsartikel (refereegranskat)abstract
- Commercial potato protein concentrate (PPC) was investigated as a source of thermoformed bio-based plastic film. Pressing temperatures of 100 to 190 degrees C with 15 to 25% glycerol were used to form PPC films. The shape of the tensile stress-strain curve in thermoformed PPC was controlled by glycerol level and was independent of processing temperature. Tensile testing revealed that elongation at break increased with processing temperature while Young's modulus was unaffected by processing temperature, both in contrast to previous results in protein based systems. Also in contrast to previous studies, Young's modulus was found to be only sensitive to glycerol level. Maximum tensile stress increased with increasing processing temperature for PPC films. Maximum stress and strain at break correlated with the extractable high molecular weight protein content of the processed films measured with size exclusion chromatography. Infrared absorption indicated that the content of beta-sheet structure increased from the commercial protein concentrate to that pressed at 100 degrees C, but did not further develop with increasing press temperature. Changes in structural arrangements were observed by small angle X-ray scattering indicating the development of different correlation distances with processing temperature but with no clear long range order at the supramolecular level. The novel Young's modulus behaviour appears to be due to constant secondary structure or the effect of aggregated protein structure formed during protein production. Unique strain at break behaviour with processing temperature was demonstrated, likely due to new connections formed between those aggregates.
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| 15. |
- Peruzzo, Pablo J., et al.
(författare)
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On the strategies for incorporating nanosilica aqueous dispersion inthe synthesis of waterborne polyurethane/silica nanocomposites:Effects on morphology and properties
- 2016
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Ingår i: Materials Today Communications. - : Elsevier BV. - 2352-4928. ; 6, s. 81-91
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Tidskriftsartikel (refereegranskat)abstract
- In this work the synthesis of waterborne polyurethane/nanosilica nanocomposites by using two differ-ent strategies is presented, starting from a vinyl terminated polyurethane prepolymer (PUP) based onisophorone diisocyanate and polypropylene glycol, and varying the nanosilica content. In one case, thePUP was dispersed in an aqueous solution containing glycerol-functionalized colloidal nanosilica parti-cles and the dispersion was further polymerized; in the other case, the PUP was dispersed in an aqueousmedia, then colloidal nanosilica was added to the dispersion and then polymerized. A physical mixturewas also prepared for comparative purpose. Films were prepared by casting of the aqueous dispersion.The morphology of the dispersions and films depended on the incorporation route of nanoparticles aswas observed by SAXS, SEM and TEM. While the blends had significantly less hydrogen bonding betweenthe hard segments of the PU and nanosilica particles, samples prepared by the two different methodsproposed in this work showed an strong interaction between both materials in agreement with FTIR andDSC results. Synthesis pathway plays an important role in order to obtain high performance waterbornepolyurethane/nanosilica composites, since final properties of the films also depended on the nanoparticleincorporation strategy.
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| 16. |
- Plivelic, Tomás S., et al.
(författare)
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X-ray tracing, design and construction of an optimized optics scheme for CoSAXS, the small angle x-ray scattering beamline at MAX IV laboratory
- 2019
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Ingår i: Proceedings of the 13th International Conference on Synchrotron Radiation Instrumentation, SRI 2018. - : Author(s). - 9780735417823 ; 2054
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Konferensbidrag (refereegranskat)abstract
- A novel optical design for a flexible SAXS beamline at a modern synchrotron has been implemented for the CoSAXS beamline at the 3GeV ring at the MAX TV Laboratory. The performance of the beamline has been simulated through combined ray tracing and wave propagation with the code xrt taking into account the low emittance and highly coherent beam of MAX TV and the short inter-optics distances of the beamline. The total photon flux is estimated to be 1012-1013 ph/s with the coherent flux portion up to 10 % at 7.1 keV. The inhomogeneities in the X-ray beam arising from use of real (non-idealised) mirror surfaces are also modelled using the measured slope profiles of the mirrors. Strategies to mitigate these inhomogeneities are discussed. The optical components for CoSAXS have been constructed and beamline commissioning will start in 2019.
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| 17. |
- Rasheed, Faiza, et al.
(författare)
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Macromolecular changes and nano-structural arrangements in gliadin and glutenin films upon chemical modification Relation to functionality
- 2015
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 79, s. 151-159
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Tidskriftsartikel (refereegranskat)abstract
- Protein macromolecules adopted for biological and bio-based material functions are known to develop a structured protein network upon chemical modification. In this study, we aimed to evaluate the impact of chemical additives such as, NaOH, NH4OH and salicylic acid (SA), on the secondary and nano-structural transitions of wheat proteins. Further, the effect of chemically induced modifications in protein macromolecular structure was anticipated in relation to functional properties. The gliadin-NH4OH-SA film showed a supramolecular protein organization into hexagonal structures with 65 angstrom lattice parameter, and other not previously observed structural entities having a characteristic distance of 50 angstrom. Proteins in gliadin-NH4OH-SA films were highly polymerized, with increased amount of disulfide crosslinks and beta-sheets, causing improved strength and stiffness. Glutenin and WG proteins with NH4OH-SA showed extensive aggregation and an increase in beta-sheet content together with irreversible crosslinks. Irreversible crosslinks hindered a high order structure formation in glutenins, and this resulted in films with only moderately improved stiffness. Thus, formation of nano-hierarchical structures based on beta-sheets and disulfide crosslinks are the major reasons of high strength and stiffness in wheat protein based films.
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| 18. |
- Rasheed, Faiza, et al.
(författare)
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Mild gluten separation - A non-destructive approach to fine tune structure and mechanical behavior of wheat gluten films
- 2015
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Ingår i: Industrial Crops and Products. - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 73, s. 90-98
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Tidskriftsartikel (refereegranskat)abstract
- Despite the increasing production of wheat gluten (WG) for industrial use, minor attention has been given to the impact of the separation procedure on the gluten quality. The purpose of the present study was to probe the effect of the separation treatments (harsh vs mild) on gluten structure, morphology, and performance in bio-based films. The harshly separated industrial WG showed aggregated and pre-cross linked structure in the starting material most likely due to shear forces during gluten separation from flour and heat effect during the drying procedures. Further, when the harshly separated WG was processed into films the pre-crosslinked starting material restricted new crosslinks formation and structural rearrangements at nano-scale. The mechanical integrity of the film was also affected resulting in films with low Young's modulus and strength. WG (from cultivars Diskette, Puntari, and Sleipner) recovered from mild separation showed relatively "native" non-destructed crosslinking pattern and not previously observed structural morphology at nano-scale. When processed into films the mildly separated WG showed well polymerized intimately crosslinked proteins both with disulfide and other covalent crosslinks. The nano-scale morphology showed lamellar and hexagonal arrangements, not reported so far in any study. The structural rearrangements among films from mildly separated WG resulted in materials with improved mechanical integrity as compared to films from harshly separated WG. The present study showed that the quality of WG is significantly affected by the separation procedure which also affects protein polymerization, nano-scale morphology, and tensile properties of films. (C) 2015 Elsevier B.V. All rights reserved.
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| 19. |
- Rasheed, Faiza, et al.
(författare)
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The use of plants as a “green factory” to produce high strength gluten-based materials
- 2016
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Ingår i: Green Chemistry. - 1463-9270. ; 18:9, s. 2782-2792
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to develop an understanding of how wheat plants can be used as a “green factory” by the modulation of genotype (G) and environmental (E) interactions to fine-tune the structure and increase the strength of gluten based materials. Two wheat genotypes (5 + 10 and 2 + 12) were grown under four nitrogen and two temperature regimes to obtain gluten of various characteristics. Protein microstructure morphology revealed by confocal laser scanning microscopy suggested a higher polymerisation of proteins in glycerol plasticized films from the 5 + 10 compared to the 2 + 12 genotype. Also, films with the highest Young’s modulus and maximum stress were obtained from the 5 + 10 genotype, which might be explained by the higher number of cysteine residues and consequently more disulphide crosslinks in this genotype compared to the 2 + 12 one. The presence of two nano-scaled morphologies, hexagonal and lamellar structures and their internal relations were found to be of relevance for formation of β-sheets and also to be related to performance (strength) of the material. Thus, plants could be used as a “green factory”, avoiding the use of chemicals, to tune the tensile properties of the materials. Structural properties such as relatively low protein aggregation, high β-sheet content and a high hexagonal to lamellar structural ratio at the nano-scale were found to yield films with high stiffness and strength.
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| 20. |
- Thuresson, Axel, et al.
(författare)
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Flocculated Laponite-PEG/PEO Dispersions with Multivalent Salt : A SAXS, Cryo-TEM, and Computer Simulation Study
- 2017
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:13, s. 7387-7396
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to scrutinize the mechanism behind aggregation, i.e., tactoid formation of nanostructures with the shape of a platelet. For that purpose, the clay minerals Laponite and montmorillonite have been used as model systems. More specifically, we are interested in the role of: the platelet size, the electrostatic interactions, and adsorbing polymers. Our hypothesis is that the presence of PEG is crucial for tactoid formation if the system is constituted by small nanometric platelets. For this purpose, SAXS, USAXS, Cryo-TEM, and coarse-grained molecular dynamics simulations have been used to study how the formation and the morphology of the tactoids are affected by the platelet size. The simulations indicate that ion-ion correlations are not enough to induce large tactoids solely if the platelets are small and the absolute charge is too low, i.e., in the size and charge range of Laponite. When a polymer is introduced into the system, the tactoid size grows, and the results can be explained by weak attractive electrostatic correlation forces and polymer bridging. It is shown that when the salt concentration increases the long-ranged electrostatic repulsion is screened, and a free energy minimum appears at short distances due to the ion-ion correlation effects. When a strongly adsorbing polymer is introduced into the system, a second free energy minimum appears at a slightly larger separation. The latter dominates if the polymer is relatively long and/or the polymer concentration is high enough. (Graph Presented).
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