•External sulfate attack on alkali-activated binder (AAB) and CEM II was tested.•Strength Loss and Strength Gain Index are used to evaluate resistance of binders.•Both AAB based on fly ash-blast ...furnace slag and CEM II showed high resistance.•Leaching of Si and decrease of Si/Al atomic ratio of AAB matrix was identified.•Correlation between AAB microstructural and strength changes was established.
Reliable durability testing of alkali-activated binders, which might serve as a basis for the prediction of long-term field performance, is one of the main challenges towards broader commercial applications of AAB. This study investigated the influence of 5% Na2SO4 solution on mechanical and microstructural properties of alkali-activated binder based on fly ash and blast furnace slag (FA-BFS) composite. The influence of Na2SO4 solution was investigated during the period of 180days and estimated by comparison with the reference samples simultaneously cured in a humid chamber and with the benchmark material CEM II. Strength, leaching (ICP-OES), pH, XRD, ATR-FTIR, and SEM/EDS analyses were performed. The Strength Loss Index was higher than 1 throughout the whole period of testing indicating strength increase during the exposure to sulfate attack rather than the loss of strength. Slower compressive strength development of the samples exposed to the sulfate solution in comparison with the reference samples was also observed. The exposure of alkali-activated binder to the sulfate solution led to a decrease in the Si/Al atomic ratio of binder matrix due to the leaching of Si, causing slower compressive strength development at the same time.
The accelerated testing method used confirmed high resistance both of alkali-activated binder based on fly ash-blast furnace slag and CEM II to external sulfate attack and at the same time confirmed its ability to discriminate the resistance of different type of binders to sulfate aggressive environment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Surfactants have found a wide range of industrial and scientific applications. In particular, detergent micelles are used as lipid membrane mimics to solubilize membrane proteins for functional and ...structural characterization. However, an atomic‐level understanding of surfactants remains limited because many experiments provide only low‐resolution structural information on surfactant aggregates. In this work, small‐angle X‐ray scattering is combined with molecular dynamics simulations to derive fully atomic models of two maltoside micelles at temperatures between 10 °C and 70 °C. The micelles take the shape of general tri‐axial ellipsoids and decrease in size and aggregation number with increasing temperature. Density profiles of hydrophobic groups and water along the three principal axes reveal that the minor micelle axis closely mimics lipid membranes. The results suggest that coupling atomic simulations with low‐resolution data allows the structural characterization of surfactant aggregates.
A combination of small‐angle X‐ray scattering and molecular dynamics simulations is used to derive fully atomic models of two maltoside micelles at temperatures between 10 °C and 70 °C. The micelles take the shape of general tri‐axial ellipsoids and decrease in size and aggregation number with increasing temperature.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Small-angle X-ray scattering (SAXS) is a popular experimental technique used to obtain structural information on biomolecules in solution. SAXS is sensitive to the overall electron density contrast ...between the biomolecule and the buffer, including contrast contributions from the hydration layer and the ion cloud. This property may be used advantageously to probe the properties of the ion cloud around charged biomolecules. However, in turn, contributions from the hydration layer and ion cloud may complicate the interpretation of the data, because these contributions must be modelled during structure validation and refinement. In this work, we quantified the influence of the ion cloud on SAXS curves of two charged proteins, bovine serum albumin (BSA) and glucose isomerase (GI), solvated in five different alkali chloride buffers of 100 mM or 500 mM concentrations. We compared three computational methods of varying physical detail, for deriving the ion cloud effect on the radius of gyration R
of the proteins, namely (i) atomistic molecular dynamics simulations in conjunction with explicit-solvent SAXS calculations, (ii) non-linear Poisson-Boltzmann calculations, and (iii) a simple spherical model in conjunction with linearized Poisson-Boltzmann theory. The calculations for BSA are validated against experimental data. We find favorable agreement among the three computational methods and the experiment, suggesting that the influence of the ion cloud on R
, as detected by SAXS, may be predicted with nearly analytic calculations. Our analysis further suggests that the ion cloud effect on R
is dominated by the long-range distribution of the ions around the proteins, as described by Debye-Hückel theory, whereas the local salt structure near the protein surface plays a minor role.
Bentazone (BZ) is selective contact-past herbicide with suspected reproductive toxicity potential for human due to possible contamination of ground and surface waters. This work presents simple, ...rapid, sensitive and accurate determination of bentazone at unmodified boron-doped diamond electrode, using differential pulse voltammetry in Britton-Robinson buffer (pH4, oxidation peak at 1.0V). Under optimized DPV conditions linear calibration curve was obtained for range of 2 to 100μM, with a detection limit of 0.5μM. The effect of possible interfering agents is negligible, confirming good selectivity of the method. The method was successfully applied to determination of bentazone in spiked river water samples. This electrochemical determination of bentazone represents a favorable alternative to other used time-consuming and expensive analytical techniques and procedures.
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•Boron-doped diamond electrode was used for sensitive determination of bentazone.•Simple and fast analytical procedure with no electrochemical pretreatment and modification•Lower detection limit compared to unmodified and some modified electrodes•Applicable for the determination of this herbicide in surface water samples
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A cost-effective and simple hydrometallurgy procedure for recycling the diamond core drilling crowns by nitric acid leaching, followed by the sodium hydroxide leaching, has been developed. The effect ...of temperature, nitric acid/sodium hydroxide concentration, leaching time and stirring rate were studied. For the acid leaching process the optimal values for parameters were 60 °C, 1.0 M HNO3, 2.5 h, and 800 rpm. It has been noted that the key factors in the alkaline leaching process were temperature and NaOH concentration. For the alkaline leaching, the optimal parameters were 100 °C, 40% concentration of NaOH solution, and leaching time of 4 h. Identification and characterisation of products in all technological processes were performed by X-Ray Diffraction (XRD), scanning electron microscope using energy-dispersive X-ray spectroscopy (SEM-EDS), and laser desorption ionisation mass spectrometry (LDI-MS). The analysis of solutions in all phases was performed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The use of LDI-MS as a new approach to identify the products after phases in the recycling process was an important part of the study, and the results were consistent with the XRD analysis. The total tungsten recovery was over 95.6%, with a high purity of the obtained tungsten trioxide.
•A cost-effective hydrometallurgy route for recycling diamond core crowns with a cemented carbide blade has been developed.•The tungsten recovery rate of 95.6% was achieved.•Obtained tungsten carbide and diamonds have been applied in practice for further use for the sintering of new heads.•The main novelty was the use of LDI-MS to identify and characterise tungsten compounds in the recycling process.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Proteins and nucleic acids can phase-separate in the cell to form concentrated biomolecular condensates
. The functions of condensates span many length scales: they modulate interactions and chemical ...reactions at the molecular scale
, organize biochemical processes at the mesoscale
and compartmentalize cells
. Understanding the underlying mechanisms of these processes will require detailed knowledge of the rich dynamics across these scales
. The mesoscopic dynamics of biomolecular condensates have been extensively characterized
, but their behaviour at the molecular scale has remained more elusive. Here, as an example of biomolecular phase separation, we study complex coacervates of two highly and oppositely charged disordered human proteins
. Their dense phase is 1,000 times more concentrated than the dilute phase, and the resulting percolated interaction network
leads to a bulk viscosity 300 times greater than that of water. However, single-molecule spectroscopy optimized for measurements within individual droplets reveals that at the molecular scale, the disordered proteins remain exceedingly dynamic, with their chain configurations interconverting on submicrosecond timescales. Massive all-atom molecular dynamics simulations reproduce the experimental observations and explain this apparent discrepancy: the underlying interactions between individual charged side chains are short-lived and exchange on a pico- to nanosecond timescale. Our results indicate that, despite the high macroscopic viscosity of phase-separated systems, local biomolecular rearrangements required for efficient reactions at the molecular scale can remain rapid.
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
Small-angle X-ray scattering (SAXS) is a widely used experimental technique, providing structural and dynamic insight into soft-matter complexes and biomolecules under near-native conditions. ...However, interpreting the one-dimensional scattering profiles in terms of three-dimensional structures and ensembles remains challenging, partly because it is poorly understood how structural information is encoded along the measured scattering angle. We combined all-atom SAXS-restrained ensemble simulations, simplified continuum models, and SAXS experiments of a n-dodecyl-β-d-maltoside (DDM) micelle to decipher the effects of model asymmetry, shape fluctuations, atomic disorder, and atomic details on SAXS curves. Upon interpreting the small-angle regime, we find remarkable agreement between (i) a two-component triaxial ellipsoid model fitted against the data and (ii) a SAXS-refined all-atom ensemble. However, continuum models fail at wider angles, even if they account for shape fluctuations, disorder, and asymmetry of the micelle. We conclude that modeling atomic details is mandatory for explaining SAXS curves at wider angles.
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IJS, KILJ, NUK, PNG, UL, UM
Single-molecule Förster resonance energy transfer (FRET) is a versatile technique for probing the structure and dynamics of biomolecules even in heterogeneous ensembles. However, because of the ...limited fluorescence brightness per molecule and the relatively long fluorescence lifetimes, probing ultrafast structural dynamics in the nanosecond time scale has thus far been very challenging. Here, we demonstrate that nanophotonic fluorescence enhancement in zero-mode waveguides enables measurements of previously inaccessible low-nanosecond dynamics by dramatically improving time resolution and reduces data acquisition times by more than an order of magnitude. As a prototypical example, we use this approach to probe the dynamics of a short intrinsically disordered peptide that were previously inaccessible with single-molecule FRET measurements. We show that we are now able to detect the low-nanosecond correlations in this peptide, and we obtain a detailed interpretation of the underlying distance distributions and dynamics in conjunction with all-atom molecular dynamics simulations, which agree remarkably well with the experiments. We expect this combined approach to be widely applicable to the investigation of very rapid biomolecular dynamics.
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IJS, KILJ, NUK, PNG, UL, UM
Highly disordered complexes between oppositely charged intrinsically disordered proteins present a new paradigm of biomolecular interactions. Here, we investigate the driving forces of such ...interactions for the example of the highly positively charged linker histone H1 and its highly negatively charged chaperone, prothymosin α (ProTα). Temperature-dependent single-molecule Förster resonance energy transfer (FRET) experiments and isothermal titration calorimetry reveal ProTα-H1 binding to be enthalpically unfavorable, and salt-dependent affinity measurements suggest counterion release entropy to be an important thermodynamic driving force. Using single-molecule FRET, we also identify ternary complexes between ProTα and H1 in addition to the heterodimer at equilibrium and show how they contribute to the thermodynamics observed in ensemble experiments. Finally, we explain the observed thermodynamics quantitatively with a mean-field polyelectrolyte theory that treats counterion release explicitly. ProTα-H1 complex formation resembles the interactions between synthetic polyelectrolytes, and the underlying principles are likely to be of broad relevance for interactions between charged biomolecules in general.
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