| 1. |
- Midtvedt, Daniel, et al.
(författare)
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Size and Refractive Index Determination of Subwavelength Particles and Air Bubbles by Holographic Nanoparticle Tracking Analysis
- 2020
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:2, s. 1908-1915
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Tidskriftsartikel (refereegranskat)abstract
- Determination of size and refractive index (RI) of dispersed unlabeled subwavelength particles is of growing interest in several fields, including biotechnology, wastewater monitoring, and nanobubble preparations. Conventionally, the size distribution of such samples is determined via the Brownian motion of the particles, but simultaneous determination of their R1 remains challenging. This work demonstrates nanoparticle tracking analysis (NTA) in an off-axis digital holographic microscope (DHM) enabling determination of both particle size and RI of individual subwavelength particles from the combined information about size and optical phase shift. The potential of the method to separate particle populations is demonstrated by analyzing a mixture of three types of dielectric particles within a narrow size range, where conventional NTA methods based on Brownian motion alone would fail. Using this approach, the phase shift allowed individual populations of dielectric beads overlapping in either size or RI to be clearly distinguished and quantified with respect to these properties. The method was furthermore applied for analysis of surfactant-stabilized micro- and nanobubbles, with RI lower than that of water. Since bubbles induce a phase shift of opposite sign to that of solid particles, they were easily distinguished from similarly sized solid particles made up of undissolved surfactant. Surprisingly, the dependence of the phase shift on bubble size indicates that only those with 0.15-0.20 mu m radius were individual bubbles, whereas larger bubbles were actually clusters of bubbles. This label-free means to quantify multiple parameters of suspended individual submicrometer particles offers a crucial complement to current characterization strategies, suggesting broad applicability for a wide range of nanoparticle systems.
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| 2. |
- Pipertzis, Achilleas, 1992, et al.
(författare)
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Ion transport, mechanical properties and relaxation dynamics in structural battery electrolytes consisting of an imidazolium protic ionic liquid confined into a methacrylate polymer
- 2023
-
Ingår i: Energy Materials: Materials Science and Engineering for Energy Systems. - 1748-9237. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- The effect of confining a liquid electrolyte into a polymer matrix was studied by means of Raman spectroscopy, differential scanning calorimetry, temperature-modulated differential scanning calorimetry, dielectric spectroscopy, and rheology. The polymer matrix was obtained from thermal curing ethoxylated bisphenol A dimethacrylate while the liquid electrolyte consisted of a protic ionic liquid based on the ethyl-imidazolium cation [C2HIm] and the bis(trifluoromethanesulfonyl)imide [TFSI] anion, doped with LiTFSI salt. We report that the confined liquid phase exhibits the following characteristics: (i) a distinctly reduced degree of crystallinity; (ii) a broader distribution of relaxation times; (iii) reduced dielectric strength; (iv) a reduced cooperativity length scale at the liquid-to-glass transition temperature (Tg); and (v) up-speeded local Tg-related ion dynamics. The latter is indicative of weak interfacial interactions between the two nanophases and a strong geometrical confinement effect, which dictates both the ion dynamics and the coupled structural relaxation, hence lowering Tg by about 4 K. We also find that at room temperature, the ionic conductivity of the structural electrolyte achieves a value of 0.13 mS/cm, one decade lower than the corresponding bulk electrolyte. Three mobile ions (Im+, TFSI-, and Li+) contribute to the measured ionic conductivity, implicitly reducing the Li+ transference number. In addition, we report that the investigated solid polymer electrolytes exhibit the shear modulus needed for transferring the mechanical load to the carbon fibers in a structural battery. Based on these findings, we conclude that optimized microphase-separated polymer electrolytes, including a protic ionic liquid, are promising for the development of novel multifunctional electrolytes for use in future structural batteries.
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| 3. |
- Ahlgren, Kajsa, 1996, et al.
(författare)
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New insights into the protein stabilizing effects of trehalose by comparing with sucrose
- 2023
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 25:32, s. 21215-21226
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Tidskriftsartikel (refereegranskat)abstract
- Disaccharides are well known to be efficient stabilizers of proteins, for example in the case of lyophilization or cryopreservation. However, although all disaccharides seem to exhibit bioprotective and stabilizing properties, it is clear that trehalose is generally superior compared to other disaccharides. The aim of this study was to understand this by comparing how the structural and dynamical properties of aqueous trehalose and sucrose solutions influence the protein myoglobin (Mb). The structural studies were based on neutron and X-ray diffraction in combination with empirical potential structure refinement (EPSR) modeling, whereas the dynamical studies were based on quasielastic neutron scattering (QENS) and molecular dynamics (MD) simulations. The results show that the overall differences in the structure and dynamics of the two systems are small, but nevertheless there are some important differences which may explain the superior stabilizing effects of trehalose. It was found that in both systems the protein is preferentially hydrated by water, but that this effect is more pronounced for trehalose, i.e. trehalose forms less hydrogen bonds to the protein surface than sucrose. Furthermore, the rotational motion around dihedrals between the two glucose rings of trehalose is slower than in the case of the dihedrals between the glucose and fructose rings of sucrose. This leads to a less perturbed protein structure in the case of trehalose. The observations indicate that an aqueous environment closest to the protein molecules is beneficial for an efficient bioprotective solution.
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| 4. |
- Ahlgren, Kajsa, 1996, et al.
(författare)
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The inhibition of fibril formation of lysozyme by sucrose and trehalose
- 2024
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Ingår i: RSC Advances. - 2046-2069. ; 14:17, s. 11921-11931
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Tidskriftsartikel (refereegranskat)abstract
- The two disaccharides, trehalose and sucrose, have been compared in many studies due to their structural similarity. Both possess the ability to stabilise and reduce aggregation of proteins. Trehalose has also been shown to inhibit the formation of highly structured protein aggregates called amyloid fibrils. This study aims to compare how the thermal stability of the protein lysozyme at low pH (2.0 and 3.5) is affected by the presence of the two disaccharides. We also address the anti-aggregating properties of the disaccharides and their inhibitory effects on fibril formation. Differential scanning calorimetry confirms that the thermal stability of lysozyme is increased by the presence of trehalose or sucrose. The effect is slightly larger for sucrose. The inhibiting effects on protein aggregation are investigated using small-angle X-ray scattering which shows that the two-component system consisting of lysozyme and water (Lys/H2O) at pH 2.0 contains larger aggregates than the corresponding system at pH 3.5 as well as the sugar containing systems. In addition, the results show that the particle-to-particle distance in the sugar containing systems (Lys/Tre/H2O and Lys/Suc/H2O) at pH 2.0 is longer than at pH 3.5, suggesting larger protein aggregates in the former. Finally, the characteristic distance separating β-strands in amyloid fibrils is observed for the Lys/H2O system at pH 2.0, using wide-angle X-ray scattering, while it is not clearly observed for the sugar containing systems. This study further shows that the two disaccharides stabilise the native fold of lysozyme by increasing the denaturation temperature. However, other factors, such as a weakening of hydrophobic interactions and hydrogen bonding between proteins, might also play a role in their inhibitory effect on amyloid fibril formation.
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| 5. |
- Berntsen, P., et al.
(författare)
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Complex modulus and compliance for airway smooth muscle cells
- 2020
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Ingår i: Physical Review E. - 2470-0045 .- 2470-0053. ; 101:3
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Tidskriftsartikel (refereegranskat)abstract
- A cell can be described as a complex viscoelastic material with structural relaxations that is modulated by thermal and chemically nonequilibrium processes. Tissue morphology and function rely upon cells' physical responses to mechanical force. We measured the frequency-dependent mechanical relaxation response of adherent human airway smooth muscle cells under adenosine triphosphate (ATP) depletion and normal ATP conditions. The frequency dependence of the complex compliance J* and modulus G* was measured over the frequencies 10(-1) < f < 10(3) Hz at selected temperatures between 4 < T < 54 degrees C. Our results show characteristic relaxation features which can be interpreted by the mode-coupling theory (MCT) of viscoelastic liquids. We analyze the shape of the spectra in terms of a so-called A(4) scenario with logarithmic scaling laws. Characteristic timescales tau(beta) and tau(alpha) appear with corresponding energy barriers E-beta approximate to (10-20)k(B) T and E-alpha approximate to (20-30)k(B)T. We demonstrate that cells are close to a glass transition. We find that the cell becomes softer around physiological temperatures, where its surface structure is more liquid-like with a plateau modulus around 0.1-0.8 kPa compared with the more solid-like interior cytoskeletal structures with a plateau modulus 1-15 kPa. Corresponding values for the viscosity are 10(2)-10(3) Pa s for the surface structures closer to the membrane and 10(4)-10(6) Pa s for the core cytoskeletal structures.
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| 6. |
- Blomgren, Fredrik, et al.
(författare)
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Two statins and cromolyn as possible drugs against the cytotoxicity of A beta(31-35) and A beta(25-35) peptides: a comparative study by advanced computer simulation methods
- 2022
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 12:21, s. 13352-13366
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Tidskriftsartikel (refereegranskat)abstract
- In this work, possible effective mechanisms of cromolyn, atorvastatin and lovastatin on the cytotoxicity of A beta(31-35) and A beta(25-35) peptides were investigated by classical molecular dynamics and well-tempered metadynamics simulations. The results demonstrate that all the drugs affect the behavior of the peptides, such as their ability to aggregate, and alter their secondary structures and their affinity to a particular drug. Our findings from the computed properties suggest that the best drug candidate is lovastatin. This medicine inhibits peptide aggregation, adsorbs the peptides on the surface of the drug clusters, changes the secondary structure and binds to MET35, which has been seen as the reason for the toxicity of the studied peptide sequences. Moreover, lovastatin is the drug which previously has demonstrated the strongest ability to penetrate the blood-brain barrier and makes lovastatin the most promising medicine among the three investigated drugs. Atorvastatin is also seen as a potential candidate if its penetration through the blood-brain barrier could be improved. Otherwise, its properties are even better than the ones demonstrated by lovastatin. Cromolyn appears to be less interesting as an anti-aggregant from the computational data, in comparison to the two statins.
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| 7. |
- Cerveny, Silvina, 1965, et al.
(författare)
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Dynamics of Water in Partially Crystallized Solutions of Glass Forming Materials and Polymers: Implications on the Behavior of Bulk Water
- 2020
-
Ingår i: Crystallization as Studied by Broadband Dielectric Spectroscopy. Advances in Dielectrics; Ezquerra T.A., Nogales A. (eds). - Cham : Springer International Publishing. - 9783030561857 ; , s. 169-194
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- There is no simpler compound than water. It is the most copious substance on Earth and the most important constituent for life, as we know. There is also a continuous scientific interest due to its exceptional and infrequent properties, such as a density maximum at 4 ℃ (at atmospheric pressure), a high specific heat capacity, and a low viscosity under high pressure, among other macroscopic properties. The origin of the unusual properties of water is evidenced at lower temperatures in the no man’s land temperature region (235–150 K), where bulk water cannot remain in an amorphous state. Instead, in this region, bulk water crystallizes in a complex phase diagram with more than 16 crystalline phases. Therefore, most of the work done so far on supercooled water focuses on the investigation of the dynamics when crystallization is suppressed using different types of confinements, such as nano-cavities or by mixing water with other solutes (polymers, proteins, or DNA). On the contrary, in this chapter, we will use broadband dielectric spectroscopy to analyze the dynamics of aqueous solutions and confined water when it is partially crystallized, i.e., when liquid water and ice coexist. With this technique, it is possible to obtain information about the molecular relaxations in both amorphous and crystalline phases. We have analyzed the results of this semi-crystalline water and compared them with the response of supercooled water in fully amorphous solutions. Finally, we discuss the implications of these results on the behavior of bulk water.
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| 8. |
- Chrobak, Wojciech, et al.
(författare)
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Component of cannabis, cannabidiol, as a possible drug against the cytotoxicity of Aβ(31-35) and Aβ(25-35) peptides: An investigation by molecular dynamics and well-tempered metadynamics simulations
- 2021
-
Ingår i: ACS Chemical Neuroscience. - : American Chemical Society (ACS). - 1948-7193. ; 12:4, s. 660-674
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Tidskriftsartikel (refereegranskat)abstract
- In this work cannabidiol (CBD) was investigated as a possible drug against the cytotoxicity of Aβ(31-35) and Aβ(25-35) peptides with the help of atomistic molecular dynamics (MD) and well-tempered metadynamics simulations. Four interrelated mechanisms of possible actions of CBD are proposed from our computations. This implies that one mechanism can be a cause or/and a consequence of another. CBD is able to decrease the aggregation of peptides at certain concentrations of compounds in water. This particular action is more prominent for Aβ(25-35), since originally Aβ(31-35) did not exhibit aggregation properties in aqueous solutions. Interactions of CBD with the peptides affect secondary structures of the latter ones. Clusters of CBD are seen as possible adsorbents of Aβ(31-35) and Aβ(25-35) since peptides are tending to aggregate around them. And last but not least, CBD exhibits binding to MET35. All four mechanisms of actions can possibly inhibit the Aβ-cytotoxicity as discussed in this paper. Moreover, the amount of water also played a role in peptide clustering: with a growing concentration of peptides in water without a drug, the aggregation of both Aβ(31-35) and Aβ(25-35) increased. The number of hydrogen bonds between peptides and water was significantly higher for simulations with Aβ(25-35) at the higher concentration of peptides, while for Aβ(31-35) that difference was rather insignificant. The presence of CBD did not substantially affect the number of hydrogen bonds in the simulated systems.
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| 9. |
- Eklund, Fredrik, 1972, et al.
(författare)
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Differentiating bulk nanobubbles from nanodroplets and nanoparticles
- 2021
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Ingår i: Current Opinion in Colloid and Interface Science. - : Elsevier BV. - 1359-0294 .- 1879-0399. ; 53
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Forskningsöversikt (refereegranskat)abstract
- History has shown that it is not as easy as one might think to differentiate between bulk nanobubbles and nanodroplets or nanoparticles. It is generally easy to detect colloids (i.e. something that looks different, e.g. scatters light differently than its surrounding solvent), but less easy to determine the nature of these colloids. This has led to misinterpretations in the literature, where nanodroplets or nanoparticles have mistakenly been assumed to be nanobubbles. In this paper, we review a multitude of experimental methods and approaches to prove the existence of bulk nanobubbles. We conclude that combinations of optical detection with physical perturbations such as pressure or ultrasound, or phase-sensitive holographic methods are the most promising and convenient approaches.
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| 10. |
- Ermilova, Inna, 1983, et al.
(författare)
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DOPC versus DOPE as a helper lipid for gene-therapies: molecular dynamics simulations with DLin-MC3-DMA
- 2020
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Ingår i: Physical Chemistry Chemical Physics. - 1463-9084 .- 1463-9076. ; 22:48, s. 28256-28268
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Tidskriftsartikel (refereegranskat)abstract
- Ionizable lipids are important compounds of modern therapeutic lipid nano-particles (LNPs). One of the most promising ionizable lipids (or amine lipids) is DLin-MC3-DMA. Depending on their pharmaceutical application these LNPs can also contain various helper lipids, such as phospho- and pegylated lipids, cholesterol and nucleic acids as a cargo. Due to their complex compositions the structures of these therapeutics have not been refined properly. Therefore, the role of each lipid in the pharmacological properties of LNPs has not been determined. In this work an atomistic model for the neutral form of DLin-MC3-DMA was derived and all-atom molecular dynamics (MD) simulations were carried out in order to investigate the effect of the phospholipid headgroup on the possible properties of the shell-membranes of LNPs. Bilayers containing either DOPC or DOPE lipids at two different ratios of DLin-MC3-DMA (5 mol% and 15 mol%) were constructed and simulated at neutral pH 7.4. The results from the analysis of MD trajectories revealed that DOPE lipid headgroups associated strongly with lipid tails and carbonyl oxygens of DLin-MC3-DMA, while for DOPC lipid headgroups no significant associations were observed. Furthermore, the strong associations between DOPE and DLin-MC3-DMA result in the positioning of DLin-MC3-DMA at the surface of the membrane. Such an interplay between the lipids slows down the lateral diffusion of all simulated bilayers, where a more dramatic decrease of the diffusion rate is observed in membranes with DOPE. This can explain the low water penetration of lipid bilayers with phosphatidylethanolamines and, probably, can relate to the bad transfection properties of LNPs with DOPE and DLin-MC3-DMA.
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| 11. |
- Ermilova, Inna, 1983, et al.
(författare)
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Ionizable lipids penetrate phospholipid bilayers with high phase transition temperatures: perspectives from free energy calculations
- 2023
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Ingår i: Chemistry and Physics of Lipids. - : Elsevier BV. - 0009-3084 .- 1873-2941. ; 253
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Tidskriftsartikel (refereegranskat)abstract
- The efficacies of modern gene-therapies strongly depend on their contents. At the same time the most potent formulations might not contain the best compounds. In this work we investigated the effect of phospholipids and their saturation on the binding ability of (6Z,9Z,28Z,31Z)-heptatriacont-6,9,28,31-tetraene-19-yl 4-(dimethylamino) butanoate (DLin-MC3-DMA) to model membranes at the neutral pH. We discovered that DLin-MC3-DMA has affinity to the most saturated monocomponent lipid bilayer 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and an aversion to the unsaturated one 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). The preference to a certain membrane was also well-correlated to the phase transition temperatures of phospholipid bilayers, and to their structural and dynamical properties. Additionally, in the case of the presence of DLin-MC3-DMA in the membrane with DOPC the ionizable lipid penetrated it, which indicates possible synergistic effects. Comparisons with other ionizable lipids were performed using a model lipid bilayer of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC). Particularly, the lipids heptadecan-9-yl 8-[2-hydroxyethyl-(6-oxo-6-undecoxyhexyl)amino]octanoate (SM-102) and [(4-hydroxybutyl) azanediyl] di(hexane-6,1-diyl) bis(2-hexyldecanoate) (ALC-0315) from modern mRNA-vaccines against COVID-19 were investigated and force fields parameters were derived for those new lipids. It was discovered that ALC-0315 binds strongest to the membrane, while DLin-MC3-DMA is not able to reside in the bilayer center. The ability to penetrate the membrane POPC by SM-102 and ALC-0315 can be related to their saturation, comparing to DLin-MC3-DMA.
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| 12. |
- Farmer, Thomas O., et al.
(författare)
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Dynamical Accuracy of Water Models on Supercooling
- 2020
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 11:18, s. 7469-7475
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics (MD) simulations are commonly used to explore the structural and dynamical properties of supercooled bulk water in the so-called "no man's land" (NML) (150-227 K), where crystallization occurs almost instantaneously. This approach has provided significant insight into experimentally inaccessible phenomena. In this paper, we compare the dynamics of simulations using one-, three-, and four-body water models to experimentally measured quasielastic neutron scattering spectra. We show that the agreement between simulated and experimental data becomes substantially worse with a decrease in temperature toward the deeply supercooled regime. It was found that it is mainly the nature of the local dynamics that is poorly reproduced, as opposed to the macroscopic properties such as the diffusion coefficient. This strongly implies that the molecular mechanism describing the water dynamics is poorly captured in the MD models, and simulated structural and dynamical properties of supercooled water in NML must be interpreted with care.
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| 13. |
- Gilbert, Jennifer, et al.
(författare)
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Effect of encapsulated protein on the dynamics of lipid sponge phase: a neutron spin echo and molecular dynamics simulation study
- 2022
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Lipid membranes are highly mobile systems with hierarchical, time and length scale dependent, collective motions including thickness fluctuations, undulations, and topological membrane changes, which play an important role in membrane interactions. In this work we have characterised the effect of encapsulating two industrially important enzymes, β-galactosidase and aspartic protease, in lipid sponge phase nanoparticles on the dynamics of the lipid membrane using neutron spin echo (NSE) spectroscopy and molecular dynamics (MD) simulations. From NSE, reduced membrane dynamics were observed upon enzyme encapsulation, which were dependent on the enzyme concentration and type. By fitting the intermediate scattering functions (ISFs) with a modified Zilman and Granek model including nanoparticle diffusion, an increase in membrane bending rigidity was observed, with a larger effect for β-galactosidase than aspartic protease at the same concentration. MD simulations for the system with and without aspartic protease showed that the lipids relax more slowly in the system with protein due to the replacement of the lipid carbonyl-water hydrogen bonds with lipid-protein hydrogen bonds. This indicates that the most likely cause of the increase in membrane rigidity observed in the NSE measurements was dehydration of the lipid head groups. The dynamics of the protein itself were also studied, which showed a stable secondary structure of protein over the simulation, indicating no unfolding events occurred.
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| 14. |
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| 15. |
- Gilbert, Jennifer, et al.
(författare)
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On the interactions between RNA and titrateable lipid layers: implications for RNA delivery with lipid nanoparticles
- 2023
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Ingår i: Nanoscale. - 2040-3372 .- 2040-3364. ; 16:2, s. 777-794
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Tidskriftsartikel (refereegranskat)abstract
- Characterising the interaction between cationic ionisable lipids (CIL) and nucleic acids (NAs) is key to understanding the process of RNA lipid nanoparticle (LNP) formation and release of NAs from LNPs. Here, we have used different surface techniques to reveal the effect of pH and NA type on the interaction with a model system of DOPC and the CIL DLin-MC3-DMA (MC3). At only 5% MC3, differences in the structure and dynamics of the lipid layer were observed. Both pH and %MC3 were shown to affect the absorption behaviour of erythropoietin mRNA, polyadenylic acid (polyA) and polyuridylic acid (polyU). The adsorbed amount of all studied NAs was found to increase with decreasing pH and increasing %MC3 but with different effects on the lipid layer, which could be linked to the NA secondary structure. For polyA at pH 6, adsorption to the surface of the layer was observed, whereas for other conditions and NAs, penetration of the NA into the layer resulted in the formation of a multilayer structure. By comparison to simulations excluding the secondary structure, differences in adsorption behaviours between polyA and polyU could be observed, indicating that the NA's secondary structure also affected the MC3-NA interactions.
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| 16. |
- Hammarin, Greger, 1981, et al.
(författare)
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No observable non-thermal effect of microwave radiation on the growth of microtubules
- 2024
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Ingår i: SCIENTIFIC REPORTS. - 2045-2322. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Despite widespread public interest in the health impact of exposure to microwave radiation, studies of the influence of microwave radiation on biological samples are often inconclusive or contradictory. Here we examine the influence of microwave radiation of frequencies 3.5 GHz, 20 GHz and 29 GHz on the growth of microtubules, which are biological nanotubes that perform diverse functions in eukaryotic cells. Since microtubules are highly polar and can extend several micrometres in length, they are predicted to be sensitive to non-ionizing radiation. Moreover, it has been speculated that tubulin dimers within microtubules might rapidly toggle between different conformations, potentially participating in computational or other cooperative processes. Our data show that exposure to microwave radiation yields a microtubule growth curve that is distorted relative to control studies utilizing a homogeneous temperature jump. However, this apparent effect of non-ionizing radiation is reproduced by control experiments using an infrared laser or hot air to heat the sample and thereby mimic the thermal history of samples exposed to microwaves. As such, no non-thermal effects of microwave radiation on microtubule growth can be assigned. Our results highlight the need for appropriate control experiments in biophysical studies that may impact on the sphere of public interest.
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| 17. |
- Huang, Liming, 1993, et al.
(författare)
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Distribution and dynamics of water in the blended pastes unraveled by thermoporometry and dielectric properties
- 2023
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Ingår i: Cement and Concrete Research. - 0008-8846. ; 174
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Tidskriftsartikel (refereegranskat)abstract
- Water distribution in hardened paste and its dynamics determine many properties related to durability. Moisture distribution was determined by thermoporometry combined with vacuum drying. Dynamics of confined water were measured by broadband dielectric spectroscopy. Water in pores <2.4 nm cannot form tetrahedral ice structure due to geometrical constraints. The volume of unfrozen water (in interlayer and gel pores) decreases after the drying at all relative humidity levels. An evident coarsening of gel pores occurs with drying between 75 % and 55 % RH. 35 % fly ash and slag have limited effects on relaxation processes of silanol hydroxyl groups and interlayer water. However, they slow down the dynamics of water in small gel pores, thereby enhancing interactions between water and the solid interface. This study clarifies the microstructural changes during the drying and reveals the sensitivity of water dynamics to the chemical environment in C-S-H of blended pastes.
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| 18. |
- Induchoodan, Govindan, 1990, et al.
(författare)
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Influence of Graphene Oxide on Asphaltene Nanoaggregates
- 2021
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 630
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Tidskriftsartikel (refereegranskat)abstract
- Asphaltenes are a group of exotic hydrocarbons found in bitumen and other forms of heavy crude oil derivatives. These hydrocarbons, with elusive chemistry, give crude oil derivatives (CODs), such as bitumen, its characteristic properties. In bitumen, they form stable aggregates by interacting with other molecules, called asphaltene aggregates. Attempts have been made to enhance bitumen with nanoparticles, like graphene derivatives. Such studies have been successful in displaying the enhanceability of bitumen, but no studies have been directly focused on how the structural stability of asphaltene aggregates present in bitumen is affected by the incorporation of nanoparticles. The phase stability of the asphaltene aggregates is a pertinent question, which is often ignored. In this study, we investigate the physical impact of incorporating graphitic nanoparticles on the structure of bitumen. For this, we utilise graphene oxide (GO). GO is a form of polyaromatic nanoparticle with a similar structure to asphaltenes, such that both have molecular defects induced by heteroatoms. We have experimentally investigated the structural stability of the asphaltenes, using XPS, XRD and SEM-EDX to elucidate the interaction between asphaltenes and GO, and its implications for the stability of bitumen used for e.g., the surface layer of roads. In roads, asphaltene aggregates exist as stable structures, until GO has been introduced. The experimental results show that the introduction of GO initiates destabilisation of the asphaltene aggregates, and we discuss the destabilisation mechanism in this paper. Thereby, we conclude that counter intuitively, the introduction of graphene or GO has a negative impact on the structure of bitumen, thus hindering any functional enhancements to bituminous roads.
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| 19. |
- Induchoodan, Govindan, 1990, et al.
(författare)
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The Critical Role of Asphaltene Nanoaggregates in Stabilizing Functionalized Graphene in Crude Oil Derivatives
- 2023
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 660
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Tidskriftsartikel (refereegranskat)abstract
- Graphene derivatives have been seen as an additive to improve the material properties of bitumen, such as thermal conductivity, viscoelasticity, and mechanical strength. However, in our previous work, a critical challenge was identified. When graphene derivatives are incorporated into bitumen, it leads to detrimental effects. This is due to the poor phase compatibility of graphene derivatives with asphaltene aggregates, the intrinsic aggregates that give bitumen its characteristic properties. In this work, we focus on tailoring the surface chemistry of graphene, thorough non-covalent functionalization, to achieve phase compatibility with asphaltene aggregates. In addition, the work also focuses on stabilizing this functionalized graphene in bitumen. To achieve this, the graphene was functionalized with -COOH tethers by the Molecular wedging method. Thereafter, the same molecules that form the asphaltene aggregates were used to stabilize the functionalized graphene by embedding the -COOH tethers in the asphaltene aggregates. As a result, graphene functionalized by this strategy was observed to be stable in bitumen and phase compatible with asphaltene aggregates. Thus, a successful environment-friendly strategy was developed to utilize the potential of graphene to improve the material properties of bitumen.
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| 20. |
- Jonsson, Olivia, 2001, et al.
(författare)
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Comparison of Sucrose and Trehalose for Protein Stabilization Using Differential Scanning Calorimetry
- 2024
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Ingår i: Journal of Physical Chemistry B. - 1520-5207 .- 1520-6106. ; 128:20, s. 4922-4930
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Tidskriftsartikel (refereegranskat)abstract
- The disaccharide trehalose is generally acknowledged as a superior stabilizer of proteins and other biomolecules in aqueous environments. Despite many theories aiming to explain this, the stabilization mechanism is still far from being fully understood. This study compares the stabilizing properties of trehalose with those of the structurally similar disaccharide sucrose. The stability has been evaluated for the two proteins, lysozyme and myoglobin, at both low and high temperatures by determining the glass transition temperature, Tg, and the denaturation temperature, Tden. The results show that the sucrose-containing samples exhibit higher Tden than the corresponding trehalose-containing samples, particularly at low water contents. The better stabilizing effect of sucrose at high temperatures may be explained by the fact that sucrose, to a greater extent, binds directly to the protein surface compared to trehalose. Both sugars show Tden elevation with an increasing sugar-to-protein ratio, which allows for a more complete sugar shell around the protein molecules. Finally, no synergistic effects were found by combining trehalose and sucrose. Conclusively, the exact mechanism of protein stabilization may vary with the temperature, as influenced by temperature-dependent interactions between the protein, sugar, and water. This variability can make trehalose to a superior stabilizer under some conditions and sucrose under others.
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| 21. |
- Melillo, Jorge H., et al.
(författare)
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Influence of ice formation on the dynamic and thermodynamic properties of aqueous solutions
- 2022
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Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322. ; 356
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Tidskriftsartikel (refereegranskat)abstract
- Water dynamics in solutions with biological or non-biological solutes has been intensely studied when both components (solvent and solute) are amorphous. Here, we apply broadband dielectric spectroscopy combined with calorimetric measurements to analyze the dynamics of the aqueous solutions tri-propylene glycol (3PG) and ε-poly (lysine) (ε-PLL), after their water becomes semi-crystalline. Various crystallization levels were explored by conducting experiments with different annealing times at temperatures above the glass transition temperature (Tg). We find that the amount of ice depends on both the time and temperature of the annealing, and that this, in turn, affects Tg and dynamics of the amorphous part of the samples. However, it should be noted that the observed differences are relatively small for the degrees of crystallinity we have studied (up to about 26 wt% of the water). This also implies that the dynamic crossover of the water relaxation from a high temperature non-Arrhenius behavior to a low temperature Arrhenius dependence is unaffected by the partial crystallization and still occurs as a single crossover at the calorimetric Tg. Thus, we cannot detect two different crossovers, as commonly observed for other types of two-component systems, such as two glass formers.
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| 22. |
- Nasedkin, Alexandr, 1987, et al.
(författare)
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Atomistic molecular dynamics simulations of tubulin heterodimers explain the motion of a microtubule
- 2021
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Ingår i: European Biophysics Journal. - : Springer Science and Business Media LLC. - 1432-1017 .- 0175-7571. ; 50:7, s. 927-940
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Tidskriftsartikel (refereegranskat)abstract
- Microtubules are essential parts of the cytoskeleton that are built by polymerization of tubulin heterodimers into a hollow tube. Regardless that their structures and functions have been comprehensively investigated in a modern soft matter, it is unclear how properties of tubulin heterodimer influence and promote the self-assembly. A detailed knowledge of such structural mechanisms would be helpful in drug design against neurodegenerative diseases, cancer, diabetes etc. In this work atomistic molecular dynamics simulations were used to investigate the fundamental dynamics of tubulin heterodimers in a sheet and a short microtubule utilizing well-equilibrated structures. The breathing motions of the tubulin heterodimers during assembly show that the movement at the lateral interface between heterodimers (wobbling) dominates in the lattice. The simulations of the protofilament curvature agrees well with recently published experimental data, showing curved protofilaments at polymerization of the microtubule plus end. The tubulin heterodimers exposed at the microtubule minus end were less curved and displayed altered interactions at the site of sheet closure around the outmost heterodimers, which may slow heterodimer binding and polymerization, providing a potential explanation for the limited dynamics observed at the minus end.
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| 23. |
- 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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| 24. |
- 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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| 25. |
- Paberit, Robert, 1987, et al.
(författare)
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Cycling stability of Poly(Ethylene Glycol) of six molecular weights: influence of thermal conditions for energy applications
- 2020
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 3:11, s. 10578-10589
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Tidskriftsartikel (refereegranskat)abstract
- Utilizing energy storage technologies is beneficial for bridging the gap between supply and demand of energy, and for increasing the share of renewable energy in the energy system. Phase change materials (PCM) offer higher energy density and compact storage design compared to conventional sensible heat storage materials. Over the past years, polyethylene glycol (PEG) gained attention in the PCM field, and several new composites of PEGs are developed for thermal energy storage purposes. PCMs are investigated at a given heating/cooling rate to evaluate their phase change temperature and enthalpy. In the case of PEG, some molecular weights show a melting behavior that depends on the thermal history, such as the crystallization conditions. This study investigates the relationship between the molecular weight of PEGs (400 to 6000 g/mol), cooling/heating rates, and the behavior during phase transitions. To evaluate the performance of PEGs as a PCM under various thermal conditions. Experiments were performed using differential scanning calorimeter (DSC) and the transient plane source method (TPS). All PEG molecular weights were subjected to the same cooling and heating conditions, cooling and heating rate and number of cycles, to decouple the thermal effects from molecular weight effects. The behavior of phase transition for different thermal conditions was thoroughly analyzed and discussed. It was found that the melting temperature range of PEGs with different molecular weight was between 5.8 °C and 62 °C (at 5 °C/min). Each PEG showed unique responses to the cooling and heating rates. Generally, the behavior of the crystallization is changing most between the thermal cycles, while the melting peak is stable regardless of the molecular weight. Finally, it is recommended that the characterization of PEGs and their composites should be conducted at a heating and cooling rate close to the thermal conditions of the intended thermal energy storage application.
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| 26. |
- Panich, Alexander M., et al.
(författare)
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Anisotropic relaxation of nuclear spins dipolar energy of water molecules in two-dimensional nanopores - A single crystal NMR study
- 2024
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Ingår i: Solid State Nuclear Magnetic Resonance. - 0926-2040 .- 1527-3326. ; 132
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Tidskriftsartikel (refereegranskat)abstract
- Energy transfer from Zeeman to dipolar order discovered by Jeener et al. is usually observed in solids with a strong dipole-dipole interaction of nuclear spins. It is not observed in liquids, where fast molecular motion completely averages this interaction. The intermediate case, when the dipole-dipole interaction of nuclear spins is only partially averaged, has been poorly studied. We report on the first measurement of an angular-dependent proton spin relaxation of a dipolar reservoir in mobile water molecules confined in the interlayer pores of a vermiculite single crystal. In this layered crystal, the intramolecular dipole-dipole interactions of nuclear spins are only partially averaged due to the restricted anisotropic molecular motion in nanopores. We show that this allows the formation of dipolar echo. We measured the spin-lattice relaxation times of the dipolar order T1D at different angles between the normal to the crystal surface and the applied magnetic field and obtained a distinct angular dependence of T1D. The minimum relaxation rate R1D was found around the magic angle of 54.74°.
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