| 1. |
- Berkowicz, Sharon, et al.
(author)
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Exploring the validity of the Stokes-Einstein relation in supercooled water using nanomolecular probes
- 2021
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 23:45, s. 25490-25499
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Journal article (peer-reviewed)abstract
- The breakdown of Stokes–Einstein relation in liquid water is one of the many anomalies that take place upon cooling and indicates the decoupling of diffusion and viscosity. It is hypothesized that these anomalies manifest due to the appearance of nanometer-scale spatial fluctuations, which become increasingly pronounced in the supercooled regime. Here, we explore the validity of the Stokes–Einstein relation in supercooled water using nanomolecular probes. We capture the diffusive dynamics of the probes using dynamic light scattering and target dynamics at different length scales by varying the probe size, from ≈100 nm silica spheres to molecular-sized polyhydroxylated fullerenes (≈1 nm). We find that all the studied probes, independent of size, display similar diffusive dynamics with an Arrhenius activation energy of ≈23 kJ mol−1. Analysis of the diffusion coefficient further indicates that the probes, independent of their size, experience similar dynamic environment, which coincides with the macroscopic viscosity, while single water molecules effectively experience a comparatively lower viscosity. Finally, we conclude that our results indicate that the Stokes–Einstein relation is preserved for diffusion of probes in supercooled water T ≥ 260 K with size as small as ≈1 nm.
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| 2. |
- Berkowicz, Sharon, et al.
(author)
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Nanofocused x-ray photon correlation spectroscopy
- 2022
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In: Physical Review Research. - 2643-1564. ; 4:3
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Journal article (peer-reviewed)abstract
- Here, we demonstrate an experimental proof of concept for nanofocused x-ray photon correlation spectroscopy, a technique sensitive to nanoscale fluctuations present in a broad range of systems. The experiment, performed at the NanoMAX beamline at MAX IV, uses a novel event-based x-ray detector to capture nanoparticle structural dynamics with microsecond resolution. By varying the nanobeam size from σ=88 nm to σ=2.5μm, we quantify the effect of the nanofocus on the small-angle scattering lineshape and on the diffusion coefficients obtained from nano-XPCS. We observe that the use of nanobeams leads to a multifold increase in speckle contrast, which greatly improves the experimental signal-to-noise ratio, quantified from the two-time intensity correlation functions. We conclude that it is possible to account for influence of the high beam divergence on the lineshape and measured dynamics by including a convolution with the nanobeam profile in the model.
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| 3. |
- Berkowicz, Sharon, 1994-, et al.
(author)
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Resolving nanoscale dynamics during a liquid-liquid transition in supercooled glycerol-water solutions
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Other publication (other academic/artistic)abstract
- It is proposed that a liquid-liquid transition (LLT), related to the hypothesized transition between high- and low-density liquids (HDL, LDL) in pure water, also exists in supercooled aqueous mixtures. However, experimental observations of the LLT in the supercooled solution is often complicated by the overlap with freezing. Here, we conducted an experiment probing the hypothesized LLT in deeply supercooled 16.5 mol% glycerol-water solution, combining X-ray photon correlation spectroscopy (XPCS), ultra small-angle X-ray scattering (USAXS) and wide-angle X-ray scattering (WAXS). This approach allows us to capture simultaneous, discontinuous structural and dynamic changes within the supercooled liquid following quenching to cryogenic temperatures (172-182 K). We observe changes in the inter-atomic liquid structure (from WAXS) as well as in the nanoscale structure and dynamics (from USAXS/XPCS), resembling a first-order LLT between HDL-like to LDL-like liquid. Importantly, we find that the LLT precedes the onset of ice crystalliization, which we can distinguish based on the advent of ice bragg peaks in WAXS. In addition, analysis of the two-time correlation (TTC) function from XPCS enables us to follow the dynamics during the LLT, which indicates super-diffusive ballistic-like motion and a gradual slowdown towards an arrested state upon freezing, consistent with an LLT via spinodal decomposition. We conclude that these results indicate the existence of a first-order LLT in supercooled glycerol-water solutions at intermediate glycerol concentrations, similar to that hypothesized for pure water at elevated pressures.
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| 4. |
- Berkowicz, Sharon
(author)
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The Role of Molecular Heterogeneity in the Structural Dynamics of Aqueous Solutions
- 2022
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Licentiate thesis (other academic/artistic)abstract
- Aqueous solutions constitute the basis of life, yet their complex and anomalous nature is far from well-understood. Transient molecular ordering gives rise to microscopic spatial liquid heterogeneities and fluctuations which are believed to play a key role in biochemical processes as well as in pure water, the latter of which could fundamentally alter our view on water as life's solvent. In this thesis, we experimentally investigate the structural dynamics in aqueous solutions with the aim to understand the role of molecular heterogeneity in the complex solution dynamics. To extract dynamic information, we utilize coherent light- and X-ray scattering techniques, such as dynamic light scattering (DLS) and X-ray photon correlation spectroscopy (XPCS), which can resolve structural dynamics on a broad range of length and time scales. We explore the influence of hypothesized water fluctuations in the dynamics of simple model solutes, finding that their diffusive dynamic behaviour is effectively similar and independent of solute size down to molecular scale, whilst significantly different from that of single water molecules. Secondly, in a first proof-of-concept experiment, we successfully combine the spatial resolution of nanofocused coherent X-ray beams with dynamic measurements by XPCS, the results of which indicate that `nano-XPCS' could prove a valuable tool in the quest to resolve nanoscale fluctuations. Finally, an outlook is given where the next steps in these investigations are discussed, such as the use of aqueous-organic mixtures as model systems for spatially heterogeneous dynamics in biological solutions.
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| 5. |
- Berkowicz, Sharon, 1994-
(author)
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The Role of Molecular Heterogeneity in the Structural Dynamics of Aqueous Solutions
- 2023
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Doctoral thesis (other academic/artistic)abstract
- The liquid-liquid critical point hypothesis suggests that liquid water exists in two liquid states with different local structures, so-called high- and low-density liquid (HDL, LDL). At ambient pressure water locally fluctuates between these two states, with the fluctuations becoming more pronounced as the liquid is supercooled. In this thesis, we explore the role of molecular heterogeneity in the structural dynamics of aqueous solutions, specifically investigating the interplay of different solutes in water with the hypothesized HDL-LDL fluctuations. In our experimental approach, we utilize coherent light and X-ray scattering techniques, including small- and wide-angle X-ray scattering (SAXS, WAXS), as well as correlation methods, such as dynamic light scattering (DLS) and X-ray photon correlation spectroscopy (XPCS), that enable us to probe structural dynamics at a broad range of length and time scales. Using DLS, we measure the diffusive dynamic behaviour of differently sized nanomolecular probes in supercooled water, finding that it is effectively similar and independent of probe size down to molecular scales of ≈1 nm. In contrast to single water molecules, these probes experience a similar dynamic environment, which coincides with the bulk viscosity. These results could suggest that anomalous influence from the hypothesized water fluctuations becomes apparent first on sub-nm length scales. Furthermore, we explore how the presence of small polar-organic solutes modulates the water phase diagram, utilizing glycerol-water solutions as a model system. By outrunning freezing with the rapid evaporative cooling technique, combined with ultrafast X-ray scattering at X-ray free-electron lasers (XFELs), we are able to probe the liquid structure in deeply supercooled dilute glycerol-water solutions. Our findings indicate the existence of HDL- and LDL-like fluctuations upon supercooling, with a Widom line shifted to slightly lower temperatures compared to pure water. Further experiments on deeply supercooled glycerol-water solutions at intermediate glycerol concentrations, combining WAXS and SAXS/XPCS, provide additional insights. These results reveal a first-order-like liquid-liquid transition involving discontinuous changes in the inter-atomic liquid structure and nanoscale liquid dynamics, which precedes ice crystallization. Lastly, with the aim of developing powerful tools for resolving dynamics within spatially heterogeneous systems, including aqueous solutions, we combine the spatial resolution of nanofocused coherent X-ray beams with dynamic measurements by XPCS. Here, we successfully demonstrate a first proof-of-concept experiment of so-called nanofocused XPCS at MAX IV synchrotron radiation facility. In future experiments, we plan to go beyond standard XPCS at synchrotrons, towards accessing ultrafast atomic-scale liquid dynamics by X-ray speckle visibility spectroscopy (XSVS) at XFELs.
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| 6. |
- Berkowicz, Sharon, 1994-, et al.
(author)
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Unveiling the Structure and Thermodynamics of Deeply Supercooled Glycerol-Water Microdroplets with Ultrafast X-ray Scattering
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Other publication (other academic/artistic)abstract
- The liquid-liquid critical point (LLCP) hypothesis of water suggests that water exists in two structurally distinct liquid states, high- and low-density liquid (HDL, LDL), with an LLCP hidden in the supercooled regime at elevated pressures. However, its consequences for solvation and structural dynamics in aqueous solutions remain to be explored. Here, we probe the structure and thermodynamics of deeply supercooled microdroplets of prototypical aqueous solutions of glycerol. The combination of rapid evaporative cooling with ultrafast small- and wide-angle X-ray scatter-ing (SAXS, WAXS) allows us to outrun crystallization and gain access to the largely unexplored deeply supercooled dilute regime (3.2 mol% glycerol) down to T ≈ 229 K, which is not accessible by conventional cooling methods. The experimental results, and complementary molecular dynamics(MD) simulations, indicate an increase in the tetrahedral coordination and enhancement of HDL-and LDL-like density fluctuations upon supercooling. In addition, the extended temperature range of the MD simulations reveals a maximum in the isothermal compressibility at T ≈ 220 K, indicating the location of a Widom line shifted to slightly lower temperatures compared to that of pure water. We conclude that the apparent effect of the presence of glycerol molecules on the water hydrogen-bond structure resembles that of pressure. This opens the possibility to search for the existence of an LLCP in these aqueous solutions simply by varying the solute concentration.
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| 7. |
- Bin, Maddalena, et al.
(author)
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Coherent X-ray Scattering Reveals Nanoscale Fluctuations in Hydrated Proteins
- 2023
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 127:21, s. 4922-4930
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Journal article (peer-reviewed)abstract
- Hydrated proteins undergo a transition in the deeply supercooled regime, which is attributed to rapid changes in hydration water and protein structural dynamics. Here, we investigate the nanoscale stress-relaxation in hydrated lysozyme proteins stimulated and probed by X-ray Photon Correlation Spectroscopy (XPCS). This approach allows us to access the nanoscale dynamics in the deeply supercooled regime (T = 180 K), which is typically not accessible through equilibrium methods. The observed stimulated dynamic response is attributed to collective stress-relaxation as the system transitions from a jammed granular state to an elastically driven regime. The relaxation time constants exhibit Arrhenius temperature dependence upon cooling with a minimum in the Kohlrausch-Williams-Watts exponent at T = 227 K. The observed minimum is attributed to an increase in dynamical heterogeneity, which coincides with enhanced fluctuations observed in the two-time correlation functions and a maximum in the dynamic susceptibility quantified by the normalized variance χT. The amplification of fluctuations is consistent with previous studies of hydrated proteins, which indicate the key role of density and enthalpy fluctuations in hydration water. Our study provides new insights into X-ray stimulated stress-relaxation and the underlying mechanisms behind spatiotemporal fluctuations in biological granular materials.
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| 8. |
- Bin, Maddalena, et al.
(author)
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Wide-angle X-ray scattering and molecular dynamics simulations of supercooled protein hydration water
- 2021
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 23:34, s. 18308-18313
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Journal article (peer-reviewed)abstract
- Understanding the mechanism responsible for the protein low-temperature crossover observed at T approximate to 220 K can help us improve current cryopreservation technologies. This crossover is associated with changes in the dynamics of the system, such as in the mean-squared displacement, whereas experimental evidence of structural changes is sparse. Here we investigate hydrated lysozyme proteins by using a combination of wide-angle X-ray scattering and molecular dynamics (MD) simulations. Experimentally we suppress crystallization by accurate control of the protein hydration level, which allows access to temperatures down to T = 175 K. The experimental data indicate that the scattering intensity peak at Q = 1.54 angstrom(-1), attributed to interatomic distances, exhibits temperature-dependent changes upon cooling. In the MD simulations it is possible to decompose the water and protein contributions and we observe that, while the protein component is nearly temperature independent, the hydration water peak shifts in a fashion similar to that of bulk water. The observed trends are analysed by using the water-water and water-protein radial distribution functions, which indicate changes in the local probability density of hydration water.
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| 9. |
- Filianina, Mariia, 1992-, et al.
(author)
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Nanocrystallites Modulate Intermolecular Interactions in Cryoprotected Protein Solutions
- 2023
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In: Journal of Physical Chemistry B. - 1520-6106 .- 1520-5207. ; 127:27, s. 6197-6204
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Journal article (peer-reviewed)abstract
- Studying protein interactions at low temperatures hasimportantimplications for optimizing cryostorage processes of biological tissue,food, and protein-based drugs. One of the major issues is relatedto the formation of ice nanocrystals, which can occur even in thepresence of cryoprotectants and can lead to protein denaturation.The presence of ice nanocrystals in protein solutions poses severalchallenges since, contrary to microscopic ice crystals, they can bedifficult to resolve and can complicate the interpretation of experimentaldata. Here, using a combination of small- and wide-angle X-ray scattering(SAXS and WAXS), we investigate the structural evolution of concentratedlysozyme solutions in a cryoprotected glycerol-water mixturefrom room temperature (T = 300 K) down to cryogenictemperatures (T = 195 K). Upon cooling, we observea transition near the melting temperature of the solution (T & AP; 245 K), which manifests both in the temperaturedependence of the scattering intensity peak position reflecting protein-proteinlength scales (SAXS) and the interatomic distances within the solvent(WAXS). Upon thermal cycling, a hysteresis is observed in the scatteringintensity, which is attributed to the formation of nanocrystallitesin the order of 10 nm. The experimental data are well described bythe two-Yukawa model, which indicates temperature-dependent changesin the short-range attraction of the protein-protein interactionpotential. Our results demonstrate that the nanocrystal growth yieldseffectively stronger protein-protein attraction and influencesthe protein pair distribution function beyond the first coordinationshell.
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| 10. |
- Reiser, Mario, et al.
(author)
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Resolving molecular diffusion and aggregation of antibody proteins with megahertz X-ray free-electron laser pulses
- 2022
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13
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Journal article (peer-reviewed)abstract
- X-ray free-electron lasers (XFELs) with megahertz repetition rate can provide novel insights into structural dynamics of biological macromolecule solutions. However, very high dose rates can lead to beam-induced dynamics and structural changes due to radiation damage. Here, we probe the dynamics of dense antibody protein (Ig-PEG) solutions using megahertz X-ray photon correlation spectroscopy (MHz-XPCS) at the European XFEL. By varying the total dose and dose rate, we identify a regime for measuring the motion of proteins in their first coordination shell, quantify XFEL-induced effects such as driven motion, and map out the extent of agglomeration dynamics. The results indicate that for average dose rates below 1.06 kGy μs−1 in a time window up to 10 μs, it is possible to capture the protein dynamics before the onset of beam induced aggregation. We refer to this approach as correlation before aggregation and demonstrate that MHz-XPCS bridges an important spatio-temporal gap in measurement techniques for biological samples.
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