| 1. |
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| 2. |
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| 3. |
- Bergman, Rikard, 1966, et al.
(author)
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Slow Debye-type peak observed in the dielectric response of polyalcohols
- 2010
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In: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 132:4
-
Journal article (peer-reviewed)abstract
- Dielectric relaxation spectroscopy of glass forming liquids normally exhibits a relaxation scenario that seems to be surprisingly general. However, the relaxation dynamics is more complicated for hydrogen bonded liquids. For instance, the dielectric response of monoalcohols is dominated by a mysterious Debye-like process at lower frequencies than the structural alpha-relaxation that is normally dominating the spectra of glass formers. For polyalcohols this process has been thought to be absent or possibly obscured by a strong contribution from conductivity and polarization effects at low frequencies. We here show that the Debye-like process, although much less prominent, is also present in the response of polyalcohols. It can be observed in the derivative of the real part of the susceptibility or directly in the imaginary part if the conductivity contribution is reduced by covering the upper electrode with a thin Teflon layer. We report on results from broadband dielectric spectroscopy studies of several polyalcohols: glycerol, xylitol, and sorbitol. The findings are discussed in relation to other experimental observations of ultraslow (i.e., slower than the viscosity related alpha-relaxation) dynamics in glass formers.
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| 4. |
- Berntsen, Peter, 1974, et al.
(author)
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Dielectric and calorimetric studies of hydrated purple membrane
- 2005
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In: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 89:5, s. 3111-3128
-
Journal article (peer-reviewed)abstract
- Purple membranes (PM) from halobacteria were hydrated to ∼0.4 and ∼0.2 g H 2 O/g of PM and studied by dielectric spectroscopy and differential scanning calorimetry between 120 and 300 K. The dielectric process, attributed to a local (β) relaxation of the confined supercooled water, shows an Arrhenius temperature behavior at low temperatures. In the case of the most hydrated PM a small deviation from the Arrhenius behavior occurs at 190-200 K together with a pronounced endothermic process and an increased activation energy. The observed crossover is accompanied by a reduction of the interlayer spacing due to the partial loss of the intermembrane water. All these effects at ∼200 K are consistent with a scenario where the local relaxation process merges with a nonobservable α-relaxation of the interlayer water, giving rise to a more liquid-like behavior of the interfacial water. For the less hydrated sample the effects are less pronounced and shift to a slightly higher temperature. © 2005 by the Biophysical Society.
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| 9. |
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Jansson, Helen, 1964, et al.
(author)
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Hidden Slow Dynamics in Water
- 2010
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 104:1
-
Journal article (peer-reviewed)abstract
- It is well known that the structural and dynamical properties of water are of central importance for life on our planet. However, despite this knowledge its structural and dynamical properties are still far from fully understood. In this Letter we show for the first time that water exhibits an anomalously slow relaxation process, which is about 4 orders of magnitude slower than the viscosity-related structural main relaxation. This slow Debye-like process has previously only been observed in monoalcohols and more recently also in polyalcohols, and due to its slowness it is generally believed to be caused by some kind of collective motion of hydrogen-bonded structures. The new finding has important structural and dynamical implications for water.
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| 14. |
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| 15. |
- Jansson, Helen, 1964, et al.
(author)
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Role of Solvent for the Dynamics and the Glass Transition of Proteins
- 2011
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 115:14, s. 4099-4109
-
Journal article (peer-reviewed)abstract
- For the first time, a systematic investigation of the glass transition and its related dynamics of myoglobin in water-glycerol solvent mixtures of different water contents is presented. By a combination of broadband dielectric spectroscopy and differential scanning calorimetry (DSC), we have studied the relation between the protein and solvent dynamics with the aim to better understand the calorimetric glass transition, T-g, of proteins and the role of solvent for protein dynamics. The results show that both the viscosity related alpha-relaxation in the solvent as well as several different protein relaxations are involved in the calorimetric glass transition, and that the broadness (Delta T-g) of the transition depends strongly on the total amount of solvent. The main reason for this seems to be that the protein relaxation processes become more separated in time with decreasing solvent level. The results are compared to that of hydrated myoglobin where the hydration water does not give any direct contribution to the calorimetric T-g. However, the large-scale a-like relaxation in the hydration water is still responsible for the protein dynamics that freeze-in at T-g. Finally, the dielectric data show clearly that the protein relaxation processes exhibit similar temperature dependences as the alpha-relaxation in the solvent, as suggested for solvent-slaved protein motions.
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| 16. |
- Jansson, Helen, 1964, et al.
(author)
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Slow dielectric response of Debye-type in water and other hydrogen bonded liquids
- 2010
-
In: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860. ; 972:1-3, s. 92-98
-
Journal article (peer-reviewed)abstract
- The slow dynamics of some hydrogen bonded glass-forming liquids has been investigated by broadband dielectric spectroscopy. We show that the polyalcohols glycerol, xylitol, and sorbitol, and mixtures of glycerol and water, and in fact, even pure water exhibit a process of Debye character at longer time-scales than the glass transition and viscosity related alpha-relaxation. Even if it is less pronounced, this process displays many similarities to the well-studied Debye-like process in monoalcohols. It can be observed in both the negative derivative of the real part of the permittivity or in the imaginary part of the permittivity, if the conductivity contribution is reduced. In the present study the conductivity contribution has been suppressed by use of a thin Teflon film placed between the sample and one of the electrodes. The new findings might have important implications for the structure and dynamics of hydrogen bonded liquids in general, and for water in particular. (c) 2010 Elsevier B.V. All rights reserved.
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| 17. |
- Midtvedt, Daniel, et al.
(author)
-
Size and Refractive Index Determination of Subwavelength Particles and Air Bubbles by Holographic Nanoparticle Tracking Analysis
- 2020
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:2, s. 1908-1915
-
Journal article (peer-reviewed)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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| 18. |
- Pipertzis, Achilleas, 1992, et al.
(author)
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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
-
In: Energy Materials: Materials Science and Engineering for Energy Systems. - 1748-9237. ; 3
-
Journal article (peer-reviewed)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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| 19. |
- Sjöström, Johan, 1978, et al.
(author)
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Dielectric secondary relaxation of water in aqueous binary glass-formers
- 2010
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In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 12:35, s. 10452-10456
-
Journal article (peer-reviewed)abstract
- Glassy aqueous binary mixtures generally exhibit a water induced dielectric relaxation. The characteristic time-scale of this relaxation follows an Arrhenius temperature dependence with a nearly universal activation energy. We here demonstrate for a series of model aqueous mixtures that the relaxation time also follows a remarkably general exponential dependence on the weight fraction of water. By comparison to literature data we show that this behaviour is shared by a wide range of molecular systems. Neither the detailed nature of the water molecules' glassy environment nor the details of the route of formation of the glassy state has a significant effect on the observed behaviour.
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| 20. |
- Sjöström, Johan, 1978, et al.
(author)
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Effects of Water Contamination on the Supercooled Dynamics of a Hydrogen-Bonded Model Glass Former
- 2011
-
In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 115:8, s. 1842-1847
-
Journal article (peer-reviewed)abstract
- Broad-band dielectric spectroscopy is a commonly used tool in the study of glass-forming liquids. The high sensitivity of the technique together with the wide range of probed time scales makes it a powerful method for investigating the relaxation spectra of liquids. One particularly important class of glass-forming liquids that is often studied using this technique consists of liquids dominated by hydrogen (H) bond interactions. When investigating such liquids, particular caution has to be taken during sample preparation due to their often highly hygroscopic nature. Water can easily be absorbed from the atmosphere, and dielectric spectroscopy is a very sensitive probe of such contamination due to the large dipole moment of water. Our knowledge concerning the effects of small quantities of water on the dielectric properties of these commonly investigated liquids is limited. We here demonstrate the effects due to the presence of small amounts of water on the dielectric response of a typical H-bonded model glass former, tripropylene glycol. We show how the relaxation processes present in the pure liquid are affected by addition of water, and we find that a characteristic water induced relaxation response is observed for water contents as low as 0.15 wt %. We stress the importance of careful purification of hygroscopic liquids before experiments and quantify what the effects are if such procedures are not undertaken.
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| 21. |
- Sjöström, Johan, 1978, et al.
(author)
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Hydrogen Bond Induced Nonmonotonic Composition Behavior of the Glass Transition in Aqueous Binary Mixtures
- 2011
-
In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 115:33, s. 10013-10017
-
Journal article (peer-reviewed)abstract
- The glass transition temperature, T(g), of a binary mixture commonly varies monotonically between the T(g)s of its two components. However, mixtures of strongly associating liquids can instead exhibit a nonmonotonic T(g) variation. The origins of such nonideal mixing behavior have often been correlated with composition dependent structural variations. For binary mixtures between a hydrogen- (H-) bonded liquid and water, however, such behavior is generally not well understood. The ubiquity and importance of aqueous mixtures both in nature and in man-made applications stresses the needed for a better understanding. We here demonstrate nonmonotonic T(g) variations in binary mixtures of n-propylene glycol monomethyl ethers (nPGMEs) and water, where the composition dependent T(g) show maxima within an intermediate composition range. We show that these T(g) maxima correspond to crossovers in the composition dependence of the step amplitude in the isobaric heat capacity at T(g). We further demonstrate that the observed effects are caused by H-bond interactions involving the nPGME hydroxyl group. We can account for our obervations using a simple model based on two effects due to the added water: (i) an H-bond induced formation of effective relaxing entities and (ii) a plasticizing effect at high water contents.
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| 22. |
- Sjöström, Johan, 1978, et al.
(author)
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Investigating hydration dependence of dynamics of confined water: Monolayer, hydration water and Maxwell-Wagner processes
- 2008
-
In: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 128:15, s. art. nr. 154503-
-
Journal article (peer-reviewed)abstract
- The dynamics of water confined in silica matrices MCM-41 C10 and C18, with pore diameter of 21 and 36 Å, respectively, is examined by broadband dielectric spectroscopy (10-2 - 109 Hz) and differential scanning calorimetry for a wide temperature interval (110-340 K). The dynamics from capillary condensed hydration water and surface monolayer of water are separated in the analysis. Contrary to previous reports, the rotational dynamics are shown to be virtually independent on the hydration level and pore size. Moreover, a third process, also reported for other systems, and exhibiting a saddlelike temperature dependence is investigated. We argue that this process is due to a Maxwell-Wagner process and not to strongly bound surface water as previously suggested in the literature. The dynamics of this process is strongly dependent on the amount of hydration water in the pores. The anomalous temperature dependence can then easily be explained by a loss of hydration water at high temperatures in contradiction to previous explanations. © 2008 American Institute of Physics.
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| 23. |
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| 24. |
- Swenson, Jan, 1966, et al.
(author)
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Anomalous behaviour of supercooled water and its implication for protein dymamics
- 2008
-
In: Lecture Notes in Physics; Aspects of Physical Biology: Biological water, Protein solutions,Transport and Replication. - Berlin : Springer-Verlag Berlin. - 9783540787648 ; , s. 23-42
-
Book chapter (other academic/artistic)abstract
- Water is the foundation of life, and without it life as we know it would not exist. An organism consists to a large extent of water and, apart from a few larger reservoirs, almost all water in a living organism is closely associated with surfaces of biomolecules of different kinds. This so-called biological water is known to affect the dynamics of biomaterials such as proteins, which. in turn is crucial for its functions. However, how and why the surrounding environment affects the dynamics of proteins and other biomolecules is still not fully understood. Recently, it was suggested [Fenimore et al. PNAS 2004, 101 14408] that local and more global protein motions are slaved (or driven) by the local beta-relaxation and the more large-scale cooperative a-relaxation in the surrounding solvent, respectively. In this chapter we present results from dielectric measurements on myoglobin in water-glycerol mixtures that support this slaving idea. Moreover, we show how confined supercooled water changes its dynamical behaviour from a low temperature Arrhenius behaviour to a high temperature non-Arrhenius behaviour at a certain temperature (around 200 K), and then we discuss likely explanations for the crossover and its consequence for protein dynamics.
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| 25. |
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| 26. |
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| 27. |
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| 28. |
- Abdurrokhman, Iqbaal, 1991, et al.
(author)
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Protic Ionic Liquids Based on the Alkyl-Imidazolium Cation: Effect of the Alkyl Chain Length on Structure and Dynamics
- 2019
-
In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 123:18, s. 4044-4054
-
Journal article (peer-reviewed)abstract
- Protic ionic liquids are known to form extended hydrogen-bonded networks that can lead to properties different from those encountered in the aprotic analogous liquids, in particular with respect to the structure and transport behavior. In this context, the present paper focuses on a wide series of 1-alkyl-imidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [HC n Im][TFSI], with the alkyl chain length (n) on the imidazolium cation varying from ethyl (n = 2) to dodecyl (n = 12). A combination of several methods, such as vibrational spectroscopy, wide-angle X-ray scattering (WAXS), broadband dielectric spectroscopy, and 1 H NMR spectroscopy, is used to understand the correlation between local cation-anion coordination, nature of nanosegregation, and transport properties. The results indicate the propensity of the -NH site on the cation to form stronger H-bonds with the anion as the alkyl chain length increases. In addition, the position and width of the scattering peak q 1 (or the pre-peak), resolved by WAXS and due to the nanosegregation of the polar from the nonpolar domains, are clearly dependent on the alkyl chain length. However, we find no evidence from pulsed-field gradient NMR of a proton motion decoupled from molecular diffusion, hypothesized to be facilitated by the longer N-H bonds localized in the segregated ionic domains. Finally, for all protic ionic liquids investigated, the ionic conductivity displays a Vogel-Fulcher-Tammann dependence on inverse temperature, with an activation energy E a that also depends on the alkyl chain length, although not strictly linearly.
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| 29. |
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| 30. |
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| 31. |
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| 32. |
- Ahlgren, Kajsa, 1996, et al.
(author)
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New insights into the protein stabilizing effects of trehalose by comparing with sucrose
- 2023
-
In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 25:32, s. 21215-21226
-
Journal article (peer-reviewed)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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| 33. |
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| 34. |
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| 35. |
- Berntsen, Peter, 1974, et al.
(author)
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Biomechanical effects of environmental and engineered particles on human airway smooth muscle cells
- 2010
-
In: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 7:Suppl 3
-
Journal article (peer-reviewed)abstract
- The past decade has seen significant increases in combustion-generated ambient particles, which contain a nanosized fraction (less than 100 nm), and even greater increases have occurred in engineered nanoparticles (NPs) propelled by the booming nanotechnology industry. Although inhalation of these particulates has become a public health concern, human health effects and mechanisms of action for NPs are not well understood. Focusing on the human airway smooth muscle cell, here we show that the cellular mechanical function is altered by particulate exposure in a manner that is dependent upon particle material, size and dose. We used Alamar Blue assay to measure cell viability and optical magnetic twisting cytometry to measure cell stiffness and agonist-induced contractility. The eight particle species fell into four categories, based on their respective effect on cell viability and on mechanical function. Cell viability was impaired and cell contractility was decreased by (i) zinc oxide (40-100 nm and less than 44 mu m) and copper(II) oxide (less than 50 nm); cell contractility was decreased by (ii) fluorescent polystyrene spheres (40 nm), increased by (iii) welding fumes and unchanged by (iv) diesel exhaust particles, titanium dioxide (25 nm) and copper(II) oxide (less than 5 mu m), although in none of these cases was cell viability impaired. Treatment with hydrogen peroxide up to 500 mu M did not alter viability or cell mechanics, suggesting that the particle effects are unlikely to be mediated by particle-generated reactive oxygen species. Our results highlight the susceptibility of cellular mechanical function to particulate exposures and suggest that direct exposure of the airway smooth muscle cells to particulates may initiate or aggravate respiratory diseases.
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| 36. |
- Berntsen, P., et al.
(author)
-
Complex modulus and compliance for airway smooth muscle cells
- 2020
-
In: Physical Review E. - 2470-0045 .- 2470-0053. ; 101:3
-
Journal article (peer-reviewed)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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| 37. |
- Berntsen, Peter, 1974, et al.
(author)
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Interplay between Hydration Water and Headgroup Dynamics in Lipid Bilayers
- 2011
-
In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 115:8, s. 1825-1832
-
Journal article (peer-reviewed)abstract
- In this study, the interplay between water and lipid dynamics has been investigated by broadband dielectric spectroscopy and modulated differential scanning calorimetry (MDSC). The rnultilamellar lipid bilayer system 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) has been studied over a broad temperature range at three different water contents: about 3, 6, and 9 water molecules per lipid molecule. The results from the dielectric relaxation measurements show that at temperatures
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| 38. |
- Blomgren, Fredrik, et al.
(author)
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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
-
In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 12:21, s. 13352-13366
-
Journal article (peer-reviewed)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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| 39. |
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| 40. |
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| 41. |
- Cerveny, S., et al.
(author)
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Confined Water as Model of Supercooled Water
- 2016
-
In: Chemical Reviews. - : American Chemical Society (ACS). - 0009-2665 .- 1520-6890. ; 116:13, s. 7608-7625
-
Research review (peer-reviewed)abstract
- Water in confined geometries has obvious relevance in biology, geology, and other areas where the material properties are strongly dependent on the amount and behavior of water in these types of materials. Another reason to restrict the size of water domains by different types of geometrical confinements has been the possibility to study the structural and dynamical behavior of water in the deeply supercooled regime (e.g., 150-230 K at ambient pressure), where bulk water immediately crystallizes to ice. In this paper we give a short review of studies with this particular goal. However, from these studies it is also clear that the interpretations of the experimental data are far from evident. Therefore, we present three main interpretations to explain the experimental data, and we discuss their advantages and disadvantages. Unfortunately, none of the proposed scenarios is able to predict all the observations for supercooled and glassy bulk water, indicating that either the structural and dynamical alterations of confined water are too severe to make predictions for bulk water or the differences in how the studied water has been prepared (applied cooling rate, resulting density of the water, etc.) are too large for direct and quantitative comparisons.
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| 42. |
- Cerveny, S., et al.
(author)
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Dynamics of supercooled water in a biological model system of the amino acid L-lysine
- 2014
-
In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 16:40, s. 22382-22390
-
Journal article (peer-reviewed)abstract
- The dynamics of supercooled water in aqueous solutions of the single amino acid L-lysine has been studied by broadband dielectric spectroscopy. The chosen biological system is unique in the sense that the water content is high enough to fully dissolve the amino acid, but low enough to avoid crystallisation to ice at any temperature. This is not possible to achieve for proteins or other larger biomolecules, where either hydrated samples without ice or solutions with large quantities of ice, or a cryoprotectant sugar, have to be studied at low temperatures. Thus, it is a key finding to be able to study water and biomolecular dynamics in a non-crystallized and biologically realistic solution at supercooled temperatures. Here, we focus on the water dynamics in this unique biological solution of L-lysine and water. We show that this unique system also gives rise to unique water dynamics, since, for the first time, a continuation of a cooperative (alpha-like) water relaxation is observed after a crossover to a more local beta-like water relaxation has occurred with decreasing temperature. This implies that the supercooled water in the biological solution shows a twofold relaxation behaviour, with one relaxation identical to the main relaxation of water in hard confinements and one relaxation almost identical to the main water relaxation in ordinary aqueous solutions.
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| 43. |
- Cerveny, Silvina, 1965, et al.
(author)
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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
-
In: Crystallization as Studied by Broadband Dielectric Spectroscopy. Advances in Dielectrics; Ezquerra T.A., Nogales A. (eds). - Cham : Springer International Publishing. - 9783030561857 ; , s. 169-194
-
Book chapter (other academic/artistic)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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| 44. |
- Cerveny, S., et al.
(author)
-
Evidence of Coupling between the Motions of Water and Peptides
- 2016
-
In: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 7:20, s. 4093-4098
-
Journal article (peer-reviewed)abstract
- Studies of protein dynamics at low temperatures are generally performed on hydrated powders and not in biologically realistic solutions of water because of water crystallization. However, here we avoid the problem of crystallization by reducing the size of the biomolecules. We have studied oligomers of the amino acid L-lysine, fully dissolved in water, and our dielectric relaxation data show that the glass transition-related dynamics of the oligomers is determined by the water dynamics, in a way similar to that previously observed for solvated proteins. This implies that the crucial role of water for protein dynamics can be extended to other types of macromolecular systems, where water is also able to determine their conformational fluctuations. Using the energy landscape picture of macromolecules, the thermodynamic criterion for such solvent-slaved macromolecular motions may be that the macromolecules need the entropy contribution from the solvent to overcome the enthalpy barriers between different conformational substates.
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| 45. |
- Cerveny, S., et al.
(author)
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Water dynamics in the hydration shells of biological and non-biological polymers
- 2019
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In: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 150:23
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Journal article (peer-reviewed)abstract
- The dynamics of water at supercooled temperatures in aqueous solutions of different types of solutes has been deeply analyzed in the literature. In these previous works and in most of the cases, a single relaxation of water molecules is observed. In this work, we analyze the dynamics of water in solutions for which a dual relaxation of water molecules is experimentally measured. We discuss the criteria for observing these two water relaxations in these specific solutions and their most likely origins. We also discuss how these two water relaxations relate to the relaxation behavior of bulk water and how the slower one is coupled to the solute dynamics and is essential for the dynamics and functional properties of proteins.
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| 46. |
- Chakraborty, S., et al.
(author)
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Mechanistic Insight into the Structure and Dynamics of Entangled and Hydrated lambda-Phage DNA
- 2012
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In: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 116:17, s. 4274-4284
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Journal article (peer-reviewed)abstract
- Intrinsic dynamics of DNA plays a crucial role in DNA protein interactions and has been emphasized as a possible key component for in vivo chromatin organization. We have prepared an entangled DNA microtube above the overlap concentration by exploiting the complementary cohesive ends of lambda-phage DNA, which is confirmed by atomic force microscopy and agarose gel electrophoresis. Photon correlation spectroscopy further confirmed that the entangled solutions are found to exhibit the classical hydrodynamics of a single chain segment on length scales smaller than the hydrodynamic length scale of single lambda-phage DNA molecule. We also observed that in 41.6% (gm water/gm DNA) hydrated state, lambda-phage DNA exhibits a dynamic transition temperature (T-dt) at 187 K and a crossover temperature (T-c) at 246 K. Computational insight reveals that the observed structure and dynamics of entangled lambda-phage DNA are distinctively different from the behavior of the corresponding unentangled DNA with open cohesive ends, which is reminiscent with our experimental observation.
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| 47. |
- Chen, Guo, 1969, et al.
(author)
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A Porosimetric Mapping of Breadcrumb Structures by Differential Scanning Calorimetry and Nuclear Magnetic Resonance
- 2013
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In: Food Biophysics. - : Springer Science and Business Media LLC. - 1557-1858 .- 1557-1866. ; 8:3, s. 209-215
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Journal article (peer-reviewed)abstract
- Ice crystals in frozen bread are substantially shaped by the complex pore structures of crumb. In this study we inspected the breadcrumb porosity of ice-filled pores from the profiles of ice crystals mapped by differential scanning calorimetry and nuclear magnetic resonance. Two types of wheat bread containing different amounts of dietary fiber and sugar were studied after frozen storage at -18 A degrees C for 3 weeks. Both pore sizes and pore size distributions were derived via comparing the measurements to those of water-saturated mesoporous silica (MCM-41 C18) with a well-defined pore size distribution. Good consistency was shown for the crumb pore structures obtained using the two techniques. Both bread types featured broad nanometer ranges of pore sizes characterized with largely bimodal size distributions. Besides, the frozen high-fiber bread displayed a higher proportion of large pores and a broader pore size distribution than the high-sugar bread. By comparing such pore size distributions with those obtained previously for the corresponding fresh bread, it can be concluded that structural differences between the two bread types were produced during the frozen storage, manifesting the disparate freezing performances of bread with different formulations.
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| 48. |
- Chen, Guo, 1969, et al.
(author)
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Formation and distribution of ice upon freezing of different formulations of wheat bread
- 2012
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In: Journal of Cereal Science. - : Elsevier BV. - 1095-9963 .- 0733-5210. ; 55:3, s. 279-284
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Journal article (peer-reviewed)abstract
- The formation and distribution of ice upon the freezing of fresh breadcrumb were investigated using differential scanning calorimetry. Three types of wheat bread containing different amounts of sugar and dietary fiber were measured. Various frozen states were produced through freezing with different cooling rates (0.5, 1, 2, 5, 10, 20 and 30 degrees C/min) to -30 degrees C; they were then analyzed and compared by thawing with the same heating rate (10 degrees C/min) to 20 degrees C. All DSC heating traces exhibited dual endotherms in the temperature range for the melting of ice: The major transition was attributed to the ice formed in the large crumb pores (gas cells) and the minor event, which preceded the major endotherm, was assigned primarily to the ice formed in the nanometer-sized pores within the gluten-starch matrix. The size of ice crystals in the two classes of pores was estimated using the modified Gibbs-Thompson relation. The distributions of ice in these pores depended on the bread compositions. It is concluded that the complex crumb porosity plays an essential role in shaping the activities of water and ice in the breadcrumb.
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| 49. |
- Chen, Guo, 1969, et al.
(author)
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Impact of long-term frozen storage on the dynamics of water and ice in wheat bread
- 2013
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In: Journal of Cereal Science. - : Elsevier BV. - 0733-5210 .- 1095-9963. ; 57:1, s. 120-124
-
Journal article (peer-reviewed)abstract
- Frozen storage of bread has a substantial impact on the dynamics of water and ice in the crumb and crust. In this study, the impact was characterized using wheat bread stored at -18 °C for a long term of ?4 months. The frozen bread incurred a considerable loss of the crumb water that migrated out and formed ice crystals on the bread surface. Such a moisture decrease underwent more rapidly for the bread stored without intact crust, suggesting the specific role of crust during frozen storage. Moisture also redistributed significantly within the frozen crumb, resulting in an elevated crumb heterogeneity of freezable water. This redistribution of freezable water was accompanied by a progressive recrystallization of the crumb-borne ice crystals, which were measured to grow into bulk sizes using a modified calorimetric procedure for analyzing the crumb samples at their as-frozen states.
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| 50. |
- Chen, G., et al.
(author)
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Protein fluctuations explored by inelastic neutron scattering and dielectric relaxation spectroscopy
- 2008
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 88:33-35, s. 3877-3883
-
Conference paper (peer-reviewed)abstract
- Glasses, supercooled liquids and proteins share common properties, in particular the existence of an energy landscape and the presence of two types of fluctuations, alpha and beta. While the effect of alpha fluctuations on proteins has been known for a few years, the effect of beta fluctuations has not been fully understood. By comparing neutron-scattering data on the protein myoglobin with beta fluctuations in the hydration shell measured by dielectric relaxation spectroscopy, we show that the internal protein motions are slaved to these fluctuations. We also show that there is no 'dynamical transition' in proteins near 200 K. The rapid increase in the mean-square displacement with temperature in many neutron-scattering experiments can be quantitatively predicted by beta fluctuations in the hydration shell.
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