| 1. |
- Combarro Palacios, Izaskun, et al.
(författare)
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Motions of water and solutes-Slaving versus plasticization phenomena
- 2019
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 150:12
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Tidskriftsartikel (refereegranskat)abstract
- It is well-accepted that hydration water is crucial for the structure, dynamics, and function of proteins. However, the exact role of water for the motions and functions of proteins is still debated. Experiments have shown that protein and water dynamics are strongly coupled but with water motions occurring on a considerably faster time scale (the so-called slaving behavior). On the other hand, water also reduces the conformational entropy of proteins and thereby acts as a plasticizer of them. In this work, we analyze the dynamics (using broadband dielectric spectroscopy) of some specific non-biological water solutions in a broad concentration range to elucidate the role of water in the dynamics of the solutes. Our results demonstrate that at low water concentrations (less than 5 wt. %), the plasticization phenomenon prevails for all the materials analyzed. However, at higher water concentrations, two different scenarios can be observed: the slaving phenomenon or plasticization, depending on the solute analyzed. These results generalize the slaving phenomenon to some, but not all, non-biological solutions and allow us to analyze the key factors for observing the slaving behavior in protein solutions as well as to reshaping the slaving concept.
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| 2. |
- Häbel, Henrike, 1987, et al.
(författare)
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From static micrographs to particle aggregation dynamics in three dimensions
- 2016
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Ingår i: Journal of Microscopy. - : Wiley. - 1365-2818 .- 0022-2720. ; 262:1, s. 102-111
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Tidskriftsartikel (refereegranskat)abstract
- Studies on colloidal aggregation have brought forth theories on stability of colloidal gels and models for aggregation dynamics. Still, a complete link between developed frameworks and obtained laboratory observations has to be found. In this work, aggregates of silica nanoparticles (20 nm) are studied using diffusion limited cluster aggregation (DLCA) and reaction limited cluster aggregation (RLCA) models. These processes are driven by the probability of particles to aggregate upon collision. This probability of aggregation is one in the DLCA and close to zero in the RLCA process. We show how to study the probability of aggregation from static micrographs on the example of a silica nanoparticle gel at 9 wt%. The analysis includes common summary functions from spatial statistics, namely the empty space function and Ripley's K-function, as well as two newly developed summary functions for cluster analysis based on graph theory. One of the new cluster analysis functions is related to the clustering coefficient in communication networks and the other to the size of a cluster. All four topological summary statistics are used to quantitatively compare in plots and in a least-square approach experimental data to cluster aggregation simulations with decreasing probabilities of aggregation. We study scanning transmission electron micrographs and utilize the intensity - mass thickness relation present in such images to create comparable micrographs from three-dimensional simulations. Finally, a characterization of colloidal silica aggregates and simulated structures is obtained, which allows for an evaluation of the cluster aggregation process for different aggregation scenarios. As a result, we find that the RLCA process fits the experimental data better than the DLCA process.
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| 3. |
- Nordin, Matias, 1981, et al.
(författare)
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Estimation of mass thickness response of embedded aggregated silica nanospheres from high angle annular dark-field scanning transmission electron micrographs
- 2014
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 253:2, s. 166-170
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigate the functional behaviour of the intensity in high-angle annular dark field scanning transmission electron micrograph images. The model material is a silica particle (20 nm) gel at 5 wt%. By assuming that the intensity response is monotonically increasing with increasing mass thickness of silica, an estimate of the functional form is calculated using a maximum likelihood approach. We conclude that a linear functional form of the intensity provides a fair estimate but that a power function is significantly better for estimating the amount of silica in the z-direction. The work adds to the development of quantifying material properties from electron micrographs, especially in the field of tomography methods and three-dimensional quantitative structural characterization from a scanning transmission electron micrograph. It also provides means for direct three-dimensional quantitative structural characterization from a scanning transmission electron micrograph.
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| 4. |
- Olsson, Christoffer, 1987
(författare)
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Interaction of trehalose with water and protein for the understanding of biological stabilization
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The understanding of biomolecular interactions with water and co-solutes opens up further understanding for the mechanism behind biomolecular stabilization. This is highly important for developing technologies aimed to preserve biological material. Such techniques include cryopreservation of for example pharmaceuticals or human organ transplants. For these purposes, the disaccharide trehalose has been shown to be an outstanding stabilizing agent during cryostorage or storage of desiccated materials. However, the stabilizing role of trehalose is still not fully understood; why does trehalose perform better than other molecules? To partly answer this question, this work investigated two important molecular systems. First, the structural properties of aqueous trehalose were studied using neutron diffraction combined with EPSR modeling. Secondly, ternary protein–trehalose–water systems were investigated using calorimetric experiments to obtain indirect evidence for different structural properties. The aqueous trehalose study provided a direct proof of strong trehalose–water interactions, and consequently a strong perturbation of the bulk-water structure. Furthermore, this study found that the trehalose molecules are highly unlikely to cluster to each other, which is hypothesized to be the reason for why trehalose is able to interact so strongly with water. The results from the calorimetric study gave support to the preferential hydration model. This study also showed that the protein stability is not necessarily coupled to the glass transition temperature of the trehalose–protein–water-matrix.
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| 5. |
- Olsson, Christoffer, 1987, et al.
(författare)
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Mechanism of Trehalose-Induced Protein Stabilization from Neutron Scattering and Modeling
- 2019
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 123:17, s. 3679-3687
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Tidskriftsartikel (refereegranskat)abstract
- The sugar molecule trehalose has been proven to be an excellent stabilizing cosolute for the preservation of biological materials. However, the stabilizing mechanism of trehalose has been much debated during the previous decades, and it is still not fully understood, partly because it has not been completely established how trehalose molecules structure around proteins. Here, we present a molecular model of a protein-water-trehalose system, based on neutron scattering results obtained from neutron diffraction, quasielastic neutron scattering, and different computer modeling techniques. The structural data clearly show how the proteins are preferentially hydrated, and analysis of the dynamical properties show that the protein residues are slowed down because of reduced dynamics of the protein hydration shell, rather than because of direct trehalose-protein interactions. These findings, thereby, strongly support previous models related to the preferential hydration model and contradict other models based on water replacement at the protein surface. Furthermore, the results are important for understanding the specific role of trehalose in biological stabilization and, more generally, for providing a likely mechanism of how cosolutes affect the dynamics of proteins.
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| 6. |
- Olsson, Christoffer, 1987, et al.
(författare)
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Stabilization of proteins embedded in sugars and water as studied by dielectric spectroscopy
- 2020
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 22:37, s. 21197-21207
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Tidskriftsartikel (refereegranskat)abstract
- In many products proteins have become an important component, and the long-term properties of these products are directly dependent on the stability of their proteins. To enhance this stability it has become common to add disaccharides in general, and trehalose in particular. However, the mechanisms by which disaccharides stabilize proteins and other biological materials are still not fully understood, and therefore we have here used broadband dielectric spectroscopy to investigate the stabilizing effect of the disaccharides trehalose and sucrose on myoglobin, with the aim to enhance this understanding in general and to obtain specific insights into why trehalose exhibits extraordinary stabilizing properties. The results show the existence of three or four clearly observed relaxation processes, where the three common relaxations are the local (β) water relaxation below the glass transition temperature (Tg), the structuralα-relaxation of the solvent, observed aboveTg, and an even slower protein relaxation due to large-scale conformational protein motions. For the trehalose containing samples with less than 50 wt% myoglobin a fourth relaxation process was observed due to a β-relaxation of trehalose belowTg. This latter process, which was assigned to intramolecular rotations of the monosaccharide rings in trehalose, could not be detected for high protein concentrations or for the sucrose containing samples. Since sucrose has previously been found to form more intramolecular hydrogen bonds at the present hydration levels, it is likely that this rotation becomes too slow to be observed in the case of sucrose. However, this sugar relaxation has probably less influence on the protein stability belowTg, where the better stabilizing effect of trehalose on proteins can be explained by our observation that trehalose slows down the water relaxation more than sucrose does. Finally, we show that the α-relaxation of the solvent and the large-scale protein motions exhibit similar temperature dependences, which suggests that these protein motions are slaved by the α-relaxation. Furthermore, the α-relaxation of the trehalose solution is slower than for the corresponding sucrose solution, and thereby also the protein motions become slower in the trehalose solution, which explains the more efficient stabilizing effect of trehalose on proteins aboveTg
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| 7. |
- Olsson, Christoffer, 1987, et al.
(författare)
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Structural Comparison between Sucrose and Trehalose in Aqueous Solution
- 2020
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 124:15, s. 3074-3082
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Tidskriftsartikel (refereegranskat)abstract
- The two sugar molecules sucrose and trehalose are both considered as stabilizing molecules for the purpose of preserving biological materials during, for example, lyophilization or cryo-preservation. Although these molecules share a similar molecular structure, there are several important differences in their properties when they interact with water, such as differences in solubility, viscosity, and glass transition temperature. In general, trehalose has been shown to be more efficient than other sugar molecules in preserving different biological molecules against stress, and thus by investigating how these two disaccharides differ in their water interaction, it is possible to further understand what makes trehalose special in its stabilizing properties. For this purpose, the structure of aqueous solutions of these disaccharides was studied by using neutron and X-ray diffraction in combination with empirical potential structure refinement (EPSR) modeling. The results show that there are surprisingly few differences in the overall structure of the solutions, although there are indications for that trehalose perturbs the water structure slightly more than sucrose.
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| 8. |
- Olsson, Christoffer, 1987, et al.
(författare)
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Structure of Aqueous Trehalose Solution by Neutron Diffraction and Structural Modeling
- 2016
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 120:49, s. 12669-12678
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Tidskriftsartikel (refereegranskat)abstract
- The molecular structure of an aqueous solution of the disaccharide trehalose (C12H22O11) has been studied by neutron diffraction and empirical potential structure refinement modeling. Six different isotope compositions with 33 wt % trehalose (corresponding to 38 water molecules per trehalose molecule) were measured to ensure that water water, trehalose water, and trehalose trehalose correlations were accurately determined. In fact, this is the first neutron diffraction study of an aqueous trehalose solution in which also the nonexchangeable hydrogen atoms in trehalose are deuterated. With this approach, it was possible to determine that (1) there is a substantial hydrogen bonding between trehalose and water (similar to 11 hydrogen bonds per trehalose molecule), which is in contrast to previous neutron diffraction studies, and (2) there is no tendency of clustering of trehalose, in contrast to what is generally observed by molecular dynamics simulations and experimentally found for other disaccharides. Thus, the results give the structural picture that trehalose prefers to interact with water and participate in a hydrogen-bonded network. This strong network character of the solution might be one of the key reasons for its extraordinary stabilization effect on biological materials.
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| 9. |
- Olsson, Christoffer, 1987, et al.
(författare)
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The role of disaccharides for protein–protein interactions – a SANS study
- 2019
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Ingår i: Molecular Physics. - : Informa UK Limited. - 1362-3028 .- 0026-8976. ; 117:22, s. 3408-3416
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Tidskriftsartikel (refereegranskat)abstract
- The disaccharide trehalose has shown outstanding anti-aggregation properties for proteins, which are highly important for the possibility to treat neurodegenerative diseases, such as Alzheimer's and Huntington's disease. However, the role and mechanism of trehalose for such stabilising effects are still largely unknown, partly because a direct structural picture of how trehalose organises around proteins in an aqueous system is missing. Here we compare small-angle neutron scattering (SANS) data on myoglobin in aqueous solutions of either sucrose or trehalose, in order to investigate their effect on protein-protein interactions. We find that both trehalose and sucrose induces a well-defined protein-protein distance, which could explain why these inhibit protein-protein interactions and associated protein aggregation. It does not however explain the superior anti-aggregation effect of trehalose and suggests that the local solvent structures are highly important for explaining the protein stabilisation mechanism. In a broader perspective, these findings are important for understanding the role of sugars in biological stabilisation, and could provide a structural explanation for why trehalose is a promising candidate for the treatment of neurodegenerative and other protein aggregation related diseases.
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| 10. |
- Olsson, Christoffer, 1987
(författare)
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The Role of Sugars for Protein Stabilization
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The understanding of biomolecular interactions with water and co-solutes can lead to greater knowledge regarding the mechanisms behind biomolecular stabilization. This is highly important for developing technologies aimed to preserve biological materials. Such techniques include cryopreservation of pharmaceuticals or human organ transplants, for example. For these purposes, the disaccharide trehalose has been shown to be an outstanding biomolecular stabilizing agent during cryostorage or storage of desiccated materials. In this thesis, the questions regarding the stabilizing role of trehalose is addressed from several different angles. Structural properties of trehalose in water are studied and are compared to those of a similar sugar molecule, namely sucrose. From these studies it was concluded that there were surprisingly small differences between the interactions of trehalose or sucrose with water. The thermodynamic properties of trehalose--water--protein systems were investigated using DSC, where it was indirectly found that the protein hydration shell was not substituted by trehalose, and that the protein stability did not necessarily couple to the glass transition temperature of the trehalose--protein--water-matrix. The structure and dynamics of such a ternary trehalose--water--protein system was also investigated using neutron diffraction combined with EPSR, and QENS combined with an MD simulation. In these studies, it was primarily found that the trehalose molecules were preferentially excluded from the protein surface, and that the local motions of the protein residues were slowed down via a reduction in the motion of the water molecules at the protein surface. Furthermore, the temperature dependences of relaxation dynamics in this system were measured using dielectric spectroscopy. This study showed that the presence of protein hinder certain local trehalose motions, and that the relatively slow dynamics of the trehalose solvent governs the conformational motions of the protein. The presented results elucidates some fundamental properties of how proteins and trehalose behave and interact, which may benefit the development of new biomolecular protective co-solutes.
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