| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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