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The accurate determination of the post-dilution concentration of biological buffers is essential for retaining the necessary properties and effectiveness of the buffer to maintain stable cellular environments and optimal conditions for biochemical reactions. In this work, we introduce a silicon-based impedance chip, which offers a rapid and reagent-free approach for monitoring the buffer concentrations after dilution with deionized (DI) water. The impedance of the impedance chip is measured, and the impedance data are modeled using a multiparameter equivalent circuit model. We investigated six aqueous biological buffers with pH values above and below the physiological pH for most tissues (pH ~ 7.2-7.4) following dilution with DI water by factors of 2.0, 10.0, 20.0, 100.0, and 200.0. The impedance measurement is then performed for the frequency spectrum of 40 Hz to 1 MHz. From the interpretation of the impedance measurement using the multiparameter equivalent circuit model, we report a buffer-sensitive equivalent circuit parameter R Au/Si of the silicon-based impedance chip showing a linear trend on a logarithmic scale with the buffer concentration change after dilution. The parameter R Au/Si is independent of the buffer pH and the added volume. The results demonstrate the efficacy of the silicon-based impedance chip as a versatile tool for precise post-dilution concentration determination of diverse biologically relevant buffers. The presented impedance chip offers rapid, accurate, and reliable monitoring, making it highly suitable for integration into automated liquid-handling systems to enhance the efficiency and precision of biological and chemical processes.

Freezing is essential for the stability of biological drug substances and products, particularly in frozen solution formulations and during the primary drying of lyophilized preparations. However, the unfrozen segment within the frozen matrix can alter solute concentration, ionic strength, and stabilizer crystallization, posing risks of increased biophysical instability and faster chemical degradation. While quantifying the unfrozen water content is important for designing stable biopharmaceuticals, there is a lack of analytical techniques for in situ quantitative measurements. In this study, we introduce a 1 H magic angle spinning NMR technique to identify the freezing point (T ice ) and quantify mobile water content in frozen biologics, applying this method to analyze the freezing of a commercial high-concentration drug product, Dupixent®. Our results demonstrate that water freezing is influenced by buffer salt properties and formulation composition, including the presence of sugar cryoprotectants and protein concentration. Additionally, the 1 H chemical shift can probe pH in the unfrozen phase, potentially predicting the microenvironmental acidity in the frozen state. Our proposed methodology provides fresh insights into the analysis of freeze-concentrated solutions, enhancing our understanding of the stability of frozen and lyophilized biopharmaceuticals., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 American Pharmacists Association. All rights reserved.)

Steviol glycosides (SGs) are a natural sweetener widely used in the food and beverage industry, but the low solubility and stability of SG aqueous solutions greatly limit their application performance, especially in liquid formulations. In this work, we explore the solubility behavior of rebaudioside A (Reb A) in water, a major component of SGs, with the aim of clarifying the underlying mechanisms of the solubility and stability constraints of SGs, as well as the impact on their multifunctional properties. We demonstrate for the first time that Reb A exhibits hierarchical self-assembly in solutions, forming spherical micelles first when the concentration exceeds its critical micelle concentration (5.071 mg/mL), which then further assemble into large rod-like aggregates. The formation of such large Reb A aggregates is mainly dominated by hydrogen bonding and short-range Coulomb interaction energy, thus leading to the low solubility and precipitation of Reb A solutions. Surprisingly, aggregated Reb A structures display significantly improved organoleptic properties, revealing that self-aggregation can be developed as a simple, efficient, and green strategy for improving the taste profile of SGs. Additionally, the self-aggregation of Reb A at high concentrations impairs active encapsulation and also affects its interfacial and emulsifying properties.

Crystallization is a widely used purification technique in the manufacture of active pharmaceutical ingredients (APIs) and precursor molecules. However, when impurities and desired compounds have similar molecular structures, separation by crystallization may become challenging. In such cases, some impurities may form crystalline solid solutions with the desired product during recrystallization. Understanding the molecular structure of these recrystallized solid solutions is crucial to devise methods for effective purification. Unfortunately, there are limited analytical techniques that provide insights into the molecular structure or spatial distribution of impurities that are incorporated within recrystallized products. In this study, we investigated model solid solutions formed by recrystallizing salicylic acid (SA) in the presence of anthranilic acid (AA). These two molecules are known to form crystalline solid solutions due to their similar molecular structures. To overcome challenges associated with the long 1 H longitudinal relaxation times ( T 1 ( 1 H)) of SA and AA, we employed dynamic nuclear polarization (DNP) and 15 N isotope enrichment to enable solid-state NMR experiments. Results of solid-state NMR experiments and DFT calculations revealed that SA and AA are homogeneously alloyed as a solid solution. Heteronuclear correlation (HETCOR) experiments and plane-wave DFT structural models provide further evidence of the molecular-level interactions between SA and AA. This research provides valuable insights into the molecular structure of recrystallized solid solutions, contributing to the development of effective purification strategies and an understanding of the physicochemical properties of solid solutions.

In recent years, solution processes have gained considerable traction as a cost-effective and scalable method to produce high-performance thermoelectric materials. The process entails a series of critical steps: synthesis, purification, thermal treatments, and consolidation, each playing a pivotal role in determining performance, stability, and reproducibility. We have noticed a need for more comprehensive details for each of the described steps in most published works. Recognizing the significance of detailed synthetic protocols, we describe here the approach used to synthesize and characterize one of the highest-performing polycrystalline p-type SnSe. In particular, we report the synthesis of SnSe particles in water and the subsequent surface treatment with CdSe molecular complexes that yields CdSe-SnSe nanocomposites upon consolidation. Moreover, the surface treatment inhibits grain growth through Zenner pinning of secondary phase CdSe nanoparticles and enhances defect formation at different length scales. The enhanced complexity in the CdSe-SnSe nanocomposite microstructure with respect to SnSe promotes phonon scattering and thereby significantly reduces the thermal conductivity. Such surface engineering provides opportunities in solution processing for introducing and controlling defects, making it possible to optimize the transport properties and attain a high thermoelectric figure of merit.

Charges and their contribution to protein-protein interactions are essential for the key structural and dynamic properties of monoclonal antibody (mAb) solutions. In fact, they influence the apparent molecular weight, the static structure factor, the collective diffusion coefficient, or the relative viscosity, and their concentration dependence. Further, charges play an important role in the colloidal stability of mAbs. There exist standard experimental tools to characterize mAb net charges, such as the measurement of the electrophoretic mobility, the second virial coefficient, or the diffusion interaction parameter. However, the resulting values are difficult to directly relate to the actual overall net charge of the antibody and to theoretical predictions based on its known molecular structure. Here, we report the results of a systematic investigation of the solution properties of a charged IgG1 mAb as a function of concentration and ionic strength using a combination of electrophoretic measurements, static and dynamic light scattering, small-angle X-ray scattering, and tracer particle-based microrheology. We analyze and interpret the experimental results using established colloid theory and coarse-grained computer simulations. We discuss the potential and limits of colloidal models for the description of the interaction effects of charged mAbs, in particular pointing out the importance of incorporating shape and charge anisotropy when attempting to predict structural and dynamic solution properties at high concentrations.

Therapeutic proteins with a high concentration and low viscosity are highly desirable for subcutaneous and certain local injections. The shape of a protein is known to influence solution viscosity; however, the precise quantification of protein shape and its relative impact compared to other factors like charge-charge interactions remains unclear. In this study, we utilized seven model proteins of varying shapes and experimentally determined their shape factors ( v ) based on Einstein's viscosity theory, which correlate strongly with the ratios of the proteins' surface area to the 2/3 power of their respective volumes, based on protein crystal structures resolved experimentally or predicted by AlphaFold. This finding confirms the feasibility of computationally estimating protein shape factors from amino acid sequences alone. Furthermore, our results demonstrated that, in high-concentration electrolyte solutions, a more spherical protein shape increases the protein's critical concentration ( C *), the transition concentration beyond which protein viscosity increases exponentially relative to concentration increases. In summary, our work elucidates protein shape as a key determinant of solution viscosity through quantitative analysis and comparison with other contributing factors. This provides insights into molecular engineering strategies to optimize the molecular design of therapeutic proteins, thus optimizing their viscosity.

Hydrophobic bonding is a phenomenon wherein the adsorption of solutes from aqueous solutions is driven largely by the desire of solvent molecules to interact with each other, thus squeezing out solute molecules onto the adsorbent surface. A novel computational analysis of hydration shell water dynamics was used to study the driving force for the hydrophobic bonding of five small drug molecules to activated carbon. It was demonstrated that the solvation of these drug molecules produced hydration shells of lower density and molecular mobility than bulk water, up to 10.5-14 Å distance. Excellent correlations were found between the simulated water-water hydrogen bonding lifetimes in the hydration shell and the experimental capacity constants of hydrophobic bonding (K HB ) obtained from the Two-Mechanism Langmuir-Like Equation. K HB also correlated well with the solute-solvent vdW interaction energies in a manner that could allow future predictions of K HB values from simple simulations. Such correlations were not found with the capacity constant of the well-known enthalpy-driven adsorption. The driving force for hydrophobic bonding has entropic origins due to the elimination of water structuring in the hydration shells. However, unlike a typical entropy-driven process, hydrophobic bonding to activated carbon was also associated with a large exothermic enthalpy change when studied with isoperibol calorimetry., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 American Pharmacists Association. Published by Elsevier Inc. All rights reserved.)

The hydrophobicity of solutes measures the intensity of a solute's interaction with aqueous environment. The aqueous environment may change with its composition, leading to changes in its solvent properties largely characterized by polarity. As a result, the relative hydrophobicity of a solute is a function of the solute structure and the properties of the water-based solvent determined by the total composition of the aqueous phase. This aspect is commonly ignored by medicinal chemists even though it is essential for drug distribution between different biological tissues. Partitioning of solutes in aqueous two-phase systems provides the relative hydrophobicity estimates for any water-soluble compounds that can be used to improve predictions of the toxicity and other biological effects of these compounds., Competing Interests: Declaration of competing interest There are no conflicts of interest to declare., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The cellular environment is crowded with macromolecules of different shapes and sizes. The effect of this macromolecular crowding has been studied in a variety of synthetic crowding environments: two popular examples are the compact colloid-like Ficoll macromolecule and the globular protein bovine serum albumin (BSA). Recent studies have indicated that a significant component of bound or surface-associated water in these crowders reduces the available free volume. In this work, Brillouin light scattering experiments were performed on aqueous solutions of Ficoll 70 and Ficoll 400 with concentrations ranging from 1 to 35 wt % and BSA with concentrations of 1 to 27 wt %. From the dependence of spectral peak parameters on polymer concentration, we determined fundamental solution properties: hypersound velocity, adiabatic bulk modulus and compressibility, apparent viscosity, and hypersound attenuation. The existing theory that ignores intermolecular interactions can capture only the observed linear trends in the frequency shift up to a threshold concentration, beyond which a quadratic term accounting for intermolecular interactions is necessary. This likely indicates a transition from the dilute to semidilute regime. In the Ficoll solutions (but not BSA), we see evidence for a central mode, which is indicative of relaxation in the hydration shell of Ficoll.

Macromolecular crowding is the usual condition of cells. The implications of the crowded cellular environment for protein stability and folding, protein-protein interactions, and intracellular transport drive a growing interest in quantifying the effects of crowding. While the properties of crowded solutions have been extensively studied, less attention has been paid to the interaction of crowders with the cellular boundaries, i.e., membranes. However, membranes are key components of cells and most subcellular organelles, playing a central role in regulating protein channel and receptor functions by recruiting and binding charged and neutral solutes. While membrane interactions with charged solutes are dominated by electrostatic forces, here we show that significant charge-induced forces also exist between membranes and neutral solutes. Using neutron reflectometry measurements and molecular dynamics simulations of poly(ethylene glycol) (PEG) polymers of different molecular weights near charged and neutral membranes, we demonstrate the roles of surface dielectrophoresis and counterion pressure in repelling PEG from charged membrane surfaces. The resulting depletion zone is expected to have consequences for drug design and delivery, the activity of proteins near membrane surfaces, and the transport of small molecules along the membrane surface.

Background: One of the important formalisms of non-equilibrium thermodynamics is Peusner network thermodynamics. The description of the energy conversion in membrane processes, i.e., the conversion of the internal energy of the system into the dissipated energy and the free energy used for the work associated with the transport of solution components, allows us to describe the relationship between these energies and the thermodynamic forces acting in the membrane system., Objectives: The aim of this study was to develop a procedure to transform the Kedem-Katchalsky equations for the transport of binary electrolytic solutions across a membrane into the Kedem-Katchalsky-Peusner equations based on Peusner network thermodynamics. The conversion of electrochemical energy to free energy in the membrane system was also determined., Material and Methods: The nanobiocellulose biomembranes (Biofill) were the subject of the study with experimentally determined transport parameters for aqueous NaCl solutions. The research method is the Kedem-Katchalsky-Peusner formalism for binary electrolyte solutions with introduced Peusner coefficients., Results: The coefficients of the L version of the membrane transport equations and the Peusner coupling coefficients were derived as functions of NaCl concentration in the membrane. Based on these coefficients, the fluxes of internal energy of the system, energy dissipated to the surroundings and free energy related to the transport of electrolyte across the membrane were calculated and presented as functions of the osmotic and electric forces on the membrane., Conclusions: The Peusner coefficients obtained from the transformations of the coefficients of the Kedem-Katchalsky formalism for the transport of electrolyte solutions through the Biofill membrane were used to calculate the coupling coefficients of the membrane processes and the dissipative energy flux. The dissipative energy flux takes the form of a quadratic form due to the thermodynamic forces on the membrane - second degree curves are obtained. Moreover, the dissipative energy flux as a function of thermodynamic forces allowed us to examine the energy conversion in transport processes in the membrane system.

It is well established that deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) exhibit a reentrant condensation (RC) phase behavior in the presence of the trivalent hexamine cobalt(III) cations (Hac) which can be important for their packing and folding. A similar behavior can be observed for negatively charged globular proteins in the presence of trivalent metal cations, such as Y 3+ or La 3+ . This phase behavior is mainly driven by charge inversion upon an increasing salt concentration for a fixed protein concentration (c p ). However, as Hac exhibits structural differences compared to other multivalent metal cations, with six ammonia ligands (NH 3 ) covalently bonded to the central cobalt atom, it is not clear that Hac can induce a similar phase behavior for proteins. In this work, we systematically investigate whether negatively charged globular proteins β-lactoglobulin (BLG), bovine serum albumin (BSA), human serum albumin (HSA) and ovalbumin (OVA) feature Hac-induced RC. Effective protein-protein interactions were investigated by small-angle X-ray scattering. The reduced second virial coefficient (B 2 /B 2 HS ) was obtained as a function of salt concentration. The virial coefficient analysis performed confirms the reentrant interaction (RI) behavior for BLG without actually inducing RC, given the insufficient strengths of the interactions for the latter to occur. In contrast, the strength of attraction for BSA, HSA and OVA are too weak to show RC. Model free analysis of the inverse intensity [Formula: see text] also supports this finding. Looking at different q-range by employing static (SLS) and dynamic light scattering experiments, the presence of RI behavior can be confirmed. The results are further discussed in view of metal cation binding sites in nucleic acids (DNA and RNA), where Hac induced RC phase behavior., (© 2023. The Author(s).)

During the developability assessment of therapeutic monoclonal antibody (mAb) candidates, utilization of robust high-throughput predictive assays enables rapid selection of top candidates with low risks for late-stage development. Predicting the viscosities of highly concentrated mAbs using limited materials is an important aspect of developability assessment because high viscosity can complicate manufacturability, stability, and administration. Here, we report a high-throughput assay measuring protein-protein interactions to predict mAb viscosity. The diffusion interaction parameter ( k D ) measures colloidal self-association in dilute solutions and has been reported to be predictive of the mAb viscosity at high concentrations. However, k D of Amgen early stage IgG1 mAb candidates measured in 10 mM acetate at pH 5.2 containing sucrose and polysorbate (denoted A52SuT) shows only weak correlation to their viscosities at 140 mg/mL in A52SuT. We hypothesize that k D measured in A52SuT reflects primarily long-range electrostatic repulsions because most of these mAb candidates carry strong net positive charges in this low ionic strength formulation with pH (5.2) well below pI values of mAb candidates. However, the viscosities of high concentration mAbs depend heavily on short-range molecular interactions. We propose an improved k D method in which salt is added to suppress charge repulsions and to allow for detection of key short-range interactions in dilute solutions. Salt types and salt concentrations were screened, and an optimal salt condition was identified. This optimized method was further validated using two test mAb sets. Overall, the method improves the Pearson R 2 between k D and viscosity (6-230 cP) from 0.24 to 0.80 for a data set consisting of 37 mAbs.

In recent years, advancements in bioengineering and materials science have witnessed increasing interest in synthetic polymers capable of fulfilling various applications. Owing to their distinctive properties, Pluronics can be used as nano-drug carriers, to deliver poorly water-soluble drugs, and as model systems to study colloidal science by tuning amphiphilic properties. In this work, we investigated the effect of diclofenac sodium on the self-assembly and thermoresponsive crystallization of Pluronic F68 in water solutions, by employing experimental rheology and Nuclear Magnetic Resonance (NMR). We built a complete phase diagram as a function of temperature and concentration for 45 wt% Pluronic F68 with various amounts of diclofenac sodium in water. The morphological transitions were followed as a function of temperature via linear rheology. We extrapolated the transition temperatures - identifying distinct phases - as a function of the drug concentration and proposed an empirical model for their prediction. NMR analysis provided further information on the structural characteristics of the systems, shedding light on the interactions between F68 and diclofenac sodium. Although dealing with a pharmaceutical salt, the study is focused on a colloidal system and its interaction with a binding molecule, that is of general interest for colloidal science., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Studying protein interactions at low temperatures has important implications for optimizing cryostorage processes of biological tissue, food, and protein-based drugs. One of the major issues is related to the formation of ice nanocrystals, which can occur even in the presence of cryoprotectants and can lead to protein denaturation. The presence of ice nanocrystals in protein solutions poses several challenges since, contrary to microscopic ice crystals, they can be difficult to resolve and can complicate the interpretation of experimental data. Here, using a combination of small- and wide-angle X-ray scattering (SAXS and WAXS), we investigate the structural evolution of concentrated lysozyme solutions in a cryoprotected glycerol-water mixture from room temperature ( T = 300 K) down to cryogenic temperatures ( T = 195 K). Upon cooling, we observe a transition near the melting temperature of the solution ( T ≈ 245 K), which manifests both in the temperature dependence of the scattering intensity peak position reflecting protein-protein length scales (SAXS) and the interatomic distances within the solvent (WAXS). Upon thermal cycling, a hysteresis is observed in the scattering intensity, which is attributed to the formation of nanocrystallites in the order of 10 nm. The experimental data are well described by the two-Yukawa model, which indicates temperature-dependent changes in the short-range attraction of the protein-protein interaction potential. Our results demonstrate that the nanocrystal growth yields effectively stronger protein-protein attraction and influences the protein pair distribution function beyond the first coordination shell.

The degradation kinetics of the glycopeptide antibiotic dalbavancin in solution are systematically evaluated over the pH range 1-12 at 70°C. The decomposition rate of dalbavancin was measured as a function of pH, buffer composition, temperature, ionic strength, and drug concentration. A pH-rate profile was constructed using pseudo first-order kinetics at 70°C after correcting for buffer effects; the observed pH-rate profile could be fitted with standard pseudo first order rate laws. The degradation reactions of dalbavancin were found to be strongly dependent on pH and were catalyzed by protons or hydroxyl groups at extreme pH values. Dalbavancin shows maximum stability in the pH region 4-5. Based on the Arrhenius equation, dalbavancin solution at pH 4.5 is predicted to have a maximum stability of thirteen years under refrigerated conditions, eight months at room temperature and one month at 40°C. Mannosyl Aglycone (MAG), the major thermal and acid degradation product, and DB-R6, an additional acid degradation product, were formed in dalbavancin solutions at 70°C due to hydrolytic cleavage at the anomeric carbons of the sugars. Through deamination and hydrolytic cleavage of dalbavancin, a small amount of DB-Iso-DP2 (RRT-1.22) degradation product was also formed under thermal stress at 70°C. A greater amount of the base degradation product DB-R2 forms under basic conditions at 70°C due to epimerization of the alpha carbon of phenylglycine residue 3., Competing Interests: Declaration of Competing Interest The authors state no conflict of interest in preparation of this manuscript., (Copyright © 2023 American Pharmacists Association. Published by Elsevier Inc. All rights reserved.)

Proton transfer is one of the most fundamental events in aqueous-phase chemistry and an emblematic case of coupled ultrafast electronic and structural dynamics 1,2 . Disentangling electronic and nuclear dynamics on the femtosecond timescales remains a formidable challenge, especially in the liquid phase, the natural environment of biochemical processes. Here we exploit the unique features of table-top water-window X-ray absorption spectroscopy 3-6 to reveal femtosecond proton-transfer dynamics in ionized urea dimers in aqueous solution. Harnessing the element specificity and the site selectivity of X-ray absorption spectroscopy with the aid of ab initio quantum-mechanical and molecular-mechanics calculations, we show how, in addition to the proton transfer, the subsequent rearrangement of the urea dimer and the associated change of the electronic structure can be identified with site selectivity. These results establish the considerable potential of flat-jet, table-top X-ray absorption spectroscopy 7,8 in elucidating solution-phase ultrafast dynamics in biomolecular systems., (© 2023. The Author(s).)

This report is the first of 2-part study of the effect of gradients in column parameters on the column performance. If t, x and p are, respectively, time since sample introduction, distance from column inlet and some parameter of solute migration along the column then ∂p/∂t and ∂p/∂x are, respectively, the rate of changing p and the gradient of p. Unified approach to study of gradients and rates in different chromatographic techniques (LC, GC, etc.) has been developed. To facilitate a unified approach, the umbrella term mobilization (y) representing column temperature (T) in GC, solvent composition (ϕ) in LC, etc. is introduced. Differential equations for migration of a solute band (collection of solute molecules) under the following conditions are formulated and solved:The key solutions describe the time of migration of a solute band and the band width - both as functions of the distance traveled by the band. The solutions are used in Part 2 for the study of the effects of the negative gradients in y on column performance in several practically important cases. A reduction of the key general solutions to much simpler equations for gradient LC has been demonstrated herein as an example., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Natural astaxanthin has been widely used in the food, cosmetic, and medicine industries due to its exceptional biological activity. Shrimp shell is one of the primary natural biological sources of astaxanthin. However, after astaxanthin recovery, there is still a lot of chitin contained in the residues. In this study, the residue from shrimp ( Penaeus vannamei ) shells after astaxanthin extraction using ionic liquid (IL) 1-ethyl-3-methyl-imidazolium acetate ([Emim]Ac) was used as a bioadsorbent to remove fluoride from the aqueous solution. The results show the IL extraction conditions, including the solid/liquid ratio, temperature, time, and particle size, all played important roles in the removal of fluoride by the shrimp shell residue. The shrimp shells treated using [Emim]Ac at 100 °C for 2 h exhibited an obvious porous structure, and the porosity showed a positive linear correlation with defluorination ( D F , %). Moreover, the adsorption process of fluoride was nonspontaneous and endothermic, which fits well with both the pseudo-second-order and Langmuir models. The maximum adsorption capacity calculated according to the Langmuir model is 3.29 mg/g, which is better than most bioadsorbents. This study provides a low-cost and efficient method for the preparation of adsorbents from shrimp processing waste to remove fluoride from wastewater.

The demand to effectively treat medical wastewater has escalated with the much greater use of antiviral drugs since the COVID-19 pandemic. Forward osmosis (FO) has great potential in wastewater treatment only when appropriate draw solutes are available. Here, we synthesize a series of smart organic-inorganic polyoxomolybdates (POMs), namely, (NH 4 ) 6 [Mo 7 O 24 ], (PrNH 3 ) 6 [Mo 7 O 24 ], ( i PrNH 3 ) 6 [Mo 7 O 24 ], and (BuNH 3 ) 6 [Mo 7 O 24 ], for FO to treat antiviral-drug wastewater. Influential factors of separation performance have been systematically studied by tailoring the structure, organic characteristics, and cation chain length of POMs. POMs at 0.4 M produce water fluxes ranging from 14.0 to 16.4 LMH with negligible solute losses, at least 116% higher than those of NaCl, NH 4 HCO 3 , and other draw solutes. (NH 4 ) 6 [Mo 7 O 24 ] creates a water flux of 11.2 LMH, increased by more than 200% compared to that of NaCl and NH 4 HCO 3 in long-term antiviral-drug wastewater reclamation. Remarkably, the drugs treated with NH 4 HCO 3 and NaCl are either contaminated or denatured, while those with (NH 4 ) 6 [Mo 7 O 24 ] remain intact. Moreover, these POMs are recovered by sunlight-assisted acidification owing to their light and pH dual sensitivity and reusability for FO. POMs prove their suitability as draw solutes and demonstrate their superiority over the commonly studied draw solutes in wastewater treatment.

In this paper, the effects of the surface electrical property and solution chemistry on the fine wolframite flotation were investigated by zeta potential measurement and the modified concentration logarithm diagrams. Based on that results, the flotation effects of different monominerals, including wolframite, scheelite, fluorite, calcite and quartz, were studied using different single collector, including sodium oleate, salicylaldoxime, benzohydroxamic acid and fatty-acid collector GYR. However, the wolframite recovery was low, and thus the mixed collectors were used to improve the recovery using benzohydroxamic acid as main collector and other collector as additional collector, including sodium oleate, salicylaldoxime, benzohydroxamic acid, fatty-acid collector GYR and fatty-acid collector TAB-3. The results show that the maximum recovery of wolframite exceeded 86% using GYB and TAB-3 as mixed collectors, which was up 13% compared with single GYB. These results could be explained in terms of the modified concentration logarithm diagrams in conjunction with the IEP values of different monominerals mentioned in this work. The infrared spectrogram indicated that because of different structures and properties of GYB and TAB-3, GYB could be complementary with TAB-3. [ABSTRACT FROM AUTHOR]

Replica exchange with solute tempering (REST) is a highly effective variant of replica exchange for enhanced sampling in explicit solvent simulations of biomolecules. By scaling the Hamiltonian for a selected "solute" region of the system, REST effectively applies tempering only to the degrees of freedom of interest but not the rest of the system ("solvent"), allowing fewer replicas for covering the same temperature range. A key consideration of REST is how the solute-solvent interactions are scaled together with the solute-solute interactions. Here, we critically evaluate the performance of the latest REST2 protocol for sampling large-scale conformation fluctuations of intrinsically disordered proteins (IDPs). The results show that REST2 promotes artificial protein conformational collapse at high effective temperatures, which seems to be a designed feature originally to promote the sampling of reversible folding of small proteins. The collapse is particularly severe with larger IDPs, leading to replica segregation in the effective temperature space and hindering effective sampling of large-scale conformational changes. We propose that the scaling of the solute-solvent interactions can be treated as free parameters in REST, which can be tuned to control the solute conformational properties (e.g., chain expansion) at different effective temperatures and achieve more effective sampling. To this end, we derive a new REST3 protocol, where the strengths of the solute-solvent van der Waals interactions are recalibrated to reproduce the levels of protein chain expansion at high effective temperatures. The efficiency of REST3 is examined using two IDPs with nontrivial local and long-range structural features, including the p53 N-terminal domain and the kinase inducible transactivation domain of transcription factor CREB. The results suggest that REST3 leads to a much more efficient temperature random walk and improved sampling efficiency, which also further reduces the number of replicas required. Nonetheless, our analysis also reveals significant challenges of relying on tempering alone for sampling large-scale conformational fluctuations of disordered proteins. It is likely that more efficient sampling protocols will require incorporating more sophisticated Hamiltonian replica exchange schemes in addition to tempering.

Collagen triple helices are critical in the function of mannan-binding lectin (MBL), an oligomeric recognition molecule in complement activation. The MBL collagen regions form complexes with the serine proteases MASP-1 and MASP-2 in order to activate complement, and mutations lead to common immunodeficiencies. To evaluate their structure-function properties, we studied the solution structures of four MBL-like collagen peptides. The thermal stability of the MBL collagen region was much reduced by the presence of a GQG interruption in the typical (X-Y-Gly)n repeat compared to controls. Experimental solution structural data were collected using analytical ultracentrifugation and small angle X-ray and neutron scattering. As controls, we included two standard Pro-Hyp-Gly collagen peptides (POG) 10-13 , as well as three more peptides with diverse (X-Y-Gly)n sequences that represented other collagen features. These data were quantitatively compared with atomistic linear collagen models derived from crystal structures and 12,000 conformations obtained from molecular dynamics simulations. All four MBL peptides were bent to varying degrees up to 85 o in the best-fit molecular dynamics models. The best-fit benchmark peptides (POG) n were more linear but exhibited a degree of conformational flexibility. The remaining three peptides showed mostly linear solution structures. In conclusion, the collagen helix is not strictly linear, the degree of flexibility in the triple helix depends on its sequence, and the triple helix with the GQG interruption showed a pronounced bend. The bend in MBL GQG peptides resembles the bend in the collagen of complement C1q and may be key for lectin pathway activation., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Liquid-liquid phase separation (LLPS) of protein solutions is governed by highly complex protein-protein interactions. Nevertheless, it has been suggested that based on the extended law of corresponding states (ELCS), as proposed for colloids with short-range attractions, one can rationalize not only the thermodynamics, but also the structure and dynamics of such systems. This claim is systematically and comprehensively tested here by static and dynamic light scattering experiments. Spinodal lines, the isothermal osmotic compressibility κ T and the relaxation rate of concentration fluctuations Γ are determined for protein solutions in the vicinity of LLPS. All these quantities are found to exhibit a corresponding-states behavior. This means that, for different solution conditions, these quantities are essentially the same if considered at similar reduced temperature or second virial coefficient. For moderately concentrated solutions, the volume fraction ϕ dependence of κ T and Γ can be consistently described by Baxter's model of adhesive hard spheres. The off-critical, asymptotic T behavior of κ T and Γ close to LLPS is consistent with the scaling laws predicted by mean-field theory. Thus, the present work aims at a comprehensive experimental test of the applicability of the ELCS to structural and dynamical properties of concentrated protein solutions.

Raman spectroscopy combined with component analysis and molecular dynamics simulation were used to study chemical species and their transformation in aqueous sodium solutions. Study shows that the characteristic vibrational frequency of nitrate ions (ν 1 -NO 3 - ) blue-shifted from 1043.9 to 1046.9 cm -1 , and the full width at half maximum increased from 6.8 to 10.8 cm -1 as the concentration increasing. When water/salt molar ratio (WSR) > 30, the relative concentration (RC) of free hydrated ions and solvent shared ion pair accounts for the vast majority, and there is almost no contact ion pair in solution. When WSR less than 30, due to the continuous reduction of the number of water molecules, the hydrated water molecules around the sodium ions and nitrate ions begin to decrease, and solvent shared ion pair or contact ion pair gradually forms. Sodium ions and nitrate ions mainly exist in a monodentate coordination. When WSR > 160, both the relative concentration of contact ion pair and complex structure is close to 0. This work proves that a lower RC of complex structure in solution, a smaller supersaturation of the solution is achieved, meaning aqueous sodium nitrate solution is easier to nucleate crystals., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Raman spectra of ethylene glycol (EG) and 1,3-propylene glycol (1,3-PG) aqueous solutions with the diol content from 10 to 90 mol% were measured. The diol content weakly influences the EG and 1,3-PG Raman bands in the spectra of the solutions in the region 250-1800 cm -1 . This fact means that the conformational compositions of both the diols do not change significantly with dissolving in water. The intensity of the OH stretching band with respect to the diol bands intensities is the linear function of the ratio of the mole contents of water and the diol in the solutions. The spectral region 2800-3800 cm -1 can be used to evaluate the chemical composition of these binary solutions. DFT modeling of the Raman spectra of EG molecule in water shell confirms the prevalence of the gauche-conformation of EG in the aqueous solutions., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Selenium (Se), a semi-metallic element, has chemical properties similar to sulfur; however, it has comparatively low electronegativity as well as a large atomic radius than sulfur. These features bestow selenium-containing compounds with extraordinary reactivity, sensitivity, and potential for several applications like chemical alteration, protein engineering, chemical (semi)synthesis, etc. Organoselenium chemistry is emerging fastly, however, examples of effective incorporation of Se into the peptides are relatively scarce. Providentially, there has been a drastic interest in synthesizing and applying selenoproteins and selenium-containing peptides over the last few decades. In this minireview, the synthetic methodologies of selenium-containing peptides and a brief description of their chemistry and biological activities are summarized. These methodologies enable access to various natural and unnatural selenium-containing peptides that have been used in a range of applications, from modulating protein characteristics to structure-activity relationship (SAR) studies for applications in nutraceuticals and drug development. This review aims at the audience interested in learning about the synthesis as well as will open new dimensions for their future research by aiding in the design of biologically interesting selenium-containing peptides., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

l-lysine is an essential amino acid whose peculiar optical properties in aqueous solutions are still in search of a comprehensive explanation. In crystalline form l-lysine does not emit, but when in an aqueous solution, as the concentration increases, emits in the blue. The origin of such fluorescence is not yet clear. In the present article, we have combined quantum mechanics and classical simulations with experimental techniques to demonstrate that optical absorption and excitation-dependent fluorescence are directly correlated with the formation of aggregates, their dimensions and intermolecular interactions. The nature of the aggregates has been studied as a function of the pH and concentration of the amino acid. At low concentrations, fluorescence intensity increases linearly with molarity, while at high concentrations a new condition is established in which emitting and non-emitting molecular species coexist. The l-lysine aggregation and the formation of intermolecular H-bonding are at the ground of the emission in the blue range., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Hypothesis: Saponins are a class of plant derived surfactants which are widely used in food related foams and emulsions, aerated drinks, and in pharmaceuticals and cosmetics. As a potential biosourced and renewable ingredient in a wider range of surfactant based formulations their potential is intimately associated with their mixing with synthetic surfactants. As such the nature of the mixed saponin-surfactant self-assembly is an important characteristic to investigate and understand. The unconventional structure of the saponins compared to the conventional synthetic surfactants poses some interesting constraints on the structures of the mixed aggregates., Experiments: Small angle neutron scattering, SANS, is used to investigate the structure of the saponin, escin, mixed with a range of nonionic surfactants with different ethylene oxide groups, from triethylene glycol monododecyl ether, C 12 E 3 , to dodecaethylene glycol monododecyl ether, C 12 E 12 ., Findings: The scattering data reveal a complex evolution in the solution self-assembled structure with varying escin / nonionic composition and ethylene oxide chain length. The rich structural development comprises of the evolution from the elongated micelle structure of escin to the micelle structure of the nonionic surfactant. At the intermediate solution compositions the structure is predominantly planar, comprising mostly of planar / micellar mixed phases. The nature of the planar structures depend upon the ethylene oxide chain length and the solution composition, and include lamellar, bilamellar vesicle, multilamellar vesicle, and nanovesicle structures, in common with what is observed in other surfactant mixtures., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Some hard-sphere colloidal models have been criticized for inaccurately predicting the solution viscosity of complex biological molecules like proteins. Competing short-range attractions and long-range repulsions, also known as short-range attraction and long-range repulsion (SALR) interactions, have been thought to affect the microstructure of a protein solution at low to moderate ionic strength. However, such interactions have been implicated primarily in causing phase transition, protein gelation, or reversible cluster formation, and their effect on protein solution viscosity change is not fully understood. In this work, we show the application of a hard-sphere colloidal model with SALR interactions toward predicting the viscosity of dilute to semi-dilute protein solutions. The comparison is performed for a globular-shaped albumin and Y-shaped therapeutic monoclonal antibody that are not explained by previous colloidal models. The model predictions show that it is the coupling between attractions and repulsions that gives rise to the observed experimental trends in solution viscosity as a function of pH, concentration, and ionic strength. The parameters of the model are obtained from measurements of the second virial coefficient and net surface charge/zeta-potential, without additional fitting of the viscosity.

The 3D reference interaction site model (3DRISM) provides an efficient grid-based solvation model to compute the structural and thermodynamic properties of biomolecules in aqueous solutions. However, it remains challenging for existing 3DRISM methods to correctly predict water distributions around negatively charged solute molecules. In this paper, we first show that this challenge is mainly due to the orientation of water molecules in the first solvation shell of the negatively charged solute molecules. To properly consider this orientational preference, position-dependent two-body intramolecular correlations of solvent need to be included in the 3DRISM theory, but direct evaluations of these position-dependent two-body intramolecular correlations remain numerically intractable. To address this challenge, we introduce the Ion-Dipole Correction (IDC) to the 3DRISM theory, in which we incorporate the orientation preference of water molecules via an additional solute-solvent interaction term (i.e., the ion-dipole interaction) while keeping the formulism of the 3DRISM equation unchanged. We prove that this newly introduced IDC term is equivalent to an effective direct correlation function which can effectively consider the orientation effect that arises from position dependent two-body correlations. We first quantitatively validate our 3DRISM-IDC theory combined with the PSE3 closure on Cl - , [ClO] - (a two-site anion), and [NO 2 ] - (a three-site anion). For all three anions, we show that our 3DRISM-IDC theory significantly outperforms the 3DRISM theory in accurately predicting the solvation structures in comparison to MD simulations, including RDFs and 3D water distributions. Furthermore, we have also demonstrated that the 3DRISM-IDC can improve the accuracy of hydration free-energy calculation for Cl - . We further demonstrate that our 3DRISM-IDC theory yields significant improvements over the 3DRISM theory when applied to compute the solvation structures for various negatively charged solute molecules, including adenosine triphosphate (ATP), a short peptide containing 19 residues, a DNA hairpin containing 24 nucleotides, and a riboswitch RNA molecule with 77 nucleotides. We expect that our 3DRISM-IDC-PSE3 solvation model holds great promise to be widely applied to study solvation properties for nucleic acids and other biomolecules containing negatively charged functional groups.

There is strong renewed interest in ion-pair chromatography (IPC) because of its great importance for separating new-generation biosimilar pharmaceuticals such as oligonucleotides. Due to the complexity of the IPC process, its mathematical modeling is challenging, especially in preparative mode. In a recent study, Leśko et al. (2021) developed a mathematical model for predicting, with good accuracy, overloaded concentration profiles for sodium benzenesulfonate, describing how the overloaded solute concentration profiles change from Langmuirian to complicated U-shaped, and then back again to Langmuirian profiles, with increasing concentration of the ion-pair reagent in the mobile phase. This study identifies and explains the underlying mechanism generating these complex peak shapes and band-shape transformations; this was only possible by visualizing and modeling the underlying equilibrium perturbations that occur upon injection in preparative IPC. In the 2021 study, the model was derived based on the concentration profiles obtained using a conventional UV detector principle, so the concentration gradients and perturbation zones of the mobile-phase components were not visualized. In this study, the necessary mechanistic information was obtained via complementary experiments combining two detection principles, i.e., refractive index detection and UV detection, with modeling efforts. The models correctly described the invisible equilibrium perturbations and how these formed internal gradients of the mobile-phase components. The models also explained the complex overloaded solute-band deformations reported in the recent study. In addition, a rule of thumb was developed for predicting experimental conditions that could result in deformed solute elution profiles and/or for avoiding these deformations. The latter is crucial for the practical chromatographer, since such U-shaped solute-band profiles are undesirable in preparative separation due to the broader elution zones, resulting in lower productivity than that of normal band shapes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Trivalent metal ions (Cr 3+ , Al 3+ , and Fe 3+ ) constitute a major section of the environmental pollutants, and their excess accumulation has a detrimental effect on health, so their detection in trace quantity has been a hot topic of research. A highly scalable 3D porous Zn-based luminescent metal-organic framework (MOF) has been synthesized by exploiting the mixed ligand synthesis concept. The strategic selection of an aromatic π-conjugated organic linker and N-rich spacer containing the azine functionality as metal ion binding sites immobilized across the pore spaces, have made this MOF an ideal turn-on sensor for Al 3+ , Cr 3+ , and Fe 3+ ions with very high sensitivity, selectivity, and recyclability. An in-depth study revealed absorbance caused enhancement mechanism (ACE) responsible for such turn-on phenomena. In order to make the detection process straightforward, convenient, portable, and economically viable, we have fabricated MOF test paper strips (the MOF could be simply immobilized onto the paper strips) for naked eye visual detection under UV light, which, thus, manifests its potential as a real-time smart sensor for these trivalent ions.

Hydrophobic interactions are involved in and believed to be the fundamental driving force of many chemical and biological phenomena in aqueous environments. This review focuses on our current understanding on hydrophobic effects. As a solute is embedded into water, the interface appears between solute and water, which mainly affects the structure of interfacial water (the topmost water layer at the solute/water interface). From our recent structural studies on water and air-water interface, hydration free energy is derived and utilized to investigate the origin of hydrophobic interactions. It is found that hydration free energy depends on the size of solute. With increasing the solute size, it is reasonably divided into initial and hydrophobic solvation processes, and various dissolved behaviors of the solutes are expected in different solvation processes, such as dispersed and accumulated distributions in solutions. Regarding the origin of hydrophobic effects, it is ascribed to the structural competition between the hydrogen bondings of interfacial and bulk water. This can be applied to understand the characteristics of hydrophobic interactions, such as the dependence of hydrophobic interactions on solute size (or concentrations), the directional natures of hydrophobic interactions, and temperature effects on hydrophobic interactions.

Ultrafast molecular dynamics in fluids is of great importance in many biological and chemical systems. Although such dynamics in bulk liquids has been explored by various methods, experimental tools that unveil the dynamics of solvated solutes are limited. In this work, we have developed resonant optical Kerr effect spectroscopy (ROKE), which is an analogue of optical Kerr effect spectroscopy that measures the reorientational relaxation of a dilute solute in solution. By adjusting the pump and probe wavelengths at the resonant absorption band of a solute, the time response of the solute was distinguished easily from the negligible signal of the solvent. The heterodyne detection of ROKE enables the determination of reorientational relaxation time constants with an accuracy of 2.6%. The signal-to-noise ratio was high enough (average ∼26.7) to obtain an adequate signal from even a 10 μM solution. Thus, ROKE is a powerful tool to study solute dynamics with high sensitivity in a broad range of applications.

Water solubility enhancement is a long-standing challenge in a multitude of chemistry-related fields. Hydrotropy is a simple and efficient method to improve the solubility of hydrophobic molecules in aqueous media. However, the mechanism behind this phenomenon remains controversial. Herein the impact of salt doping on the hydrotropy phenomenon is determined experimentally using the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([C 4 mim]Cl) as a hydrotope and vanillin as a solute. Hydrophobic interactions were found to be central to the aggregation of the hydrotrope around the solute, and seem to drive hydrotropy. Furthermore, 1 H-NMR analysis indicates that hydrotrope-solute interactions present a degree of site-specificity. The addition of chloride salts in the presence of higher IL concentrations promotes a greater relative decrease of the vanillin solubility than in the corresponding system without the IL. This was assigned to the negative impact of increased hydrotrope pre-aggregation in the presence of inorganic salts. The results were rationalised using statistical thermodynamics through which hydrotrope aggregation prior to solute addition is shown to be detrimental to the hydrotropic effect, seemingly confirming solute-induced clustering of the hydrotrope to be the predominant mechanism of hydrotropy.

Poly- N -isopropylacrylamide (PNIPAM) is a thermo-responsive polymer that exhibits a reversible structural change from extended chains to aggregates in aqueous solution above its lower critical solution temperature (LCST). Using polarization-selective IR pump-probe spectroscopy, the water orientational dynamics in PNIPAM from below to above the LCST were examined and compared to those of its monomer solution, N -isopropylacrylamide (NIPAM), polyacrylamide, and an acrylamide monomer solution, which are not thermo-responsive. The OD stretch of dilute HOD in H 2 O is used as a vibrational probe of water orientational dynamics. Below the LCST of the polymer, NIPAM and PNIPAM solutions exhibited identical water dynamics that were significantly different from those of bulk water, containing both faster and slower components due to solute-water interactions. Therefore, there is no difference in the nature of water interactions with a single NIPAM moiety and a long polymer chain. For all systems, including PNIPAM below and above the LCST, the orientational dynamics were modeled with a bulk water component and a polymer/monomer-associated component based on previous experimental and computational findings. Above the LCST, PNIPAM showed fast water orientational relaxation but much slower long-time dynamics compared to those of NIPAM. The slow component in PNIPAM, which was too slow to be accurately measured due to the limited OD vibrational lifetime, is ascribed to water confined in small voids (<2 nm in diameter) of PNIPAM globules. These results highlight important details about thermo-responsive polymers and the dynamics of their solvation water as they undergo a significant structural change.

The Hofmeister series is frequently used to rank ions based on their behavior from chaotropes ("structure breakers"), which weaken the surrounding hydrogen-bond network, to kosmotropes ("structure makers"), which enhance it. Here, we use fluctuation theory to investigate the energetic and entropic driving forces underlying the Hofmeister series for aqueous alkali-halide solutions. Specifically, we exploit the OH stretch infrared (IR) spectrum in isotopically dilute HOD/D 2 O solutions as a probe of the effect of the salt on the water properties for different concentrations and choice of halide anion. Fluctuation theory is used to calculate the temperature derivative of these IR spectra, including decomposition of the derivative into different energetic contributions. These contributions are used to determine the thermodynamic driving forces in terms of effective internal energy and entropic contributions. This analysis implicates entropic contributions as the key factor in the Hofmeister series behavior of the OH stretch IR spectra, while the effective internal energy is nearly ion-independent.

Blind predictions of octanol/water partition coefficients and pKa at 298.15 K for 22 drug-like compounds were made for the SAMPL7 challenge. Octanol/water partition coefficients were predicted from solvation free energies computed using electronic structure calculations with the SM12, SM8 and SMD solvation models. Within these calculations we compared the use of gas- and solution-phase optimized geometries of the solute. Based on these calculations we found that in general the use of solution phase-optimized geometries increases the affinity of the solutes for water as compared to octanol, with the use of gas-phase optimized geometries resulting in the better agreement with experiment. The pKa is computed using the direct approach, scaled solvent-accessible surface model, and the inclusion of an explicit water molecule, where the latter two methods have previously been shown to offer improved predictions as compared to the direct approach. We find that the use of an explicit water molecule provides superior predictions, and that the predicted macroscopic pKa is sensitive to the employed microstates., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

In solution-phase chemistry, the solvent is often considered to be merely a medium that allows reacting solutes to encounter each other. In this work, however, we show that moderate locally specific solute-solvent interactions can affect not only the nature of the solute but also the types of reactive chemistry. We use quantum simulation methods to explore how solvent participation in solute chemical identity alters reactions involving the breaking of chemical bonds. In particular, we explore the photoexcitation dynamics of Na 2 + dissolved in liquid tetrahydrofuran. In the gas phase, excitation of Na 2 + directly leads to dissociation, but in solution, photoexcitation leads to an isomerization reaction involving rearrangement of the first-shell solvent molecules; this isomerization must go to completion before the solute can dissociate. Despite the complexity, the solution-phase reaction dynamics can be captured by a two-dimensional energy surface where one dimension involves only the isomerization of the first-shell solvent molecules.

Recently, thermo-responsive nonionic amphiphilic copolymers have shown a great potential as forward osmosis (FO) draw solutes for high-salinity water desalination and zero-liquid discharge (ZLD). However, the relationship between the copolymer structural properties and key characteristics as draw solutes, as well as copolymer's chemical stability after regeneration have not been much studied. In this work, we systematically investigated poly (ethylene oxide)-block-poly (propylene oxide)-block-poly (ethylene oxide) (PEO-PPO-PEO) copolymers as draw solute. The results showed that the PEO segments significantly influenced the viscosity, osmotic pressure and lowest phase separation temperature of the copolymer aqueous solutions. Among four commercial copolymers studied, Pluronic® L35 with moderate molecular weight (Mn 1,900 Da), 50% PEO, and relatively high hydrophilic-lipophilic balance (HLB) showed the best draw solution (DS) performance. It also showed great stability in physiochemical properties and draw capacity after more than ten cycles of regeneration. On the other hand, despite the fact that membrane fouling was observed due to the use of copolymer DS, the FO flux (∼1.2 L m ‒2 h ‒1 , as similar with the virgin membrane) was not affected when high-salinity feedwater such as seawater RO brine was applied. Overall, our study has provided a more comprehensive understanding on the characteristics of nonionic amphiphilic copolymer DS and showcased the promise of copolymer-driven FO process in high-salinity water desalination and ZLD., (Copyright © 2022. Published by Elsevier Ltd.)

Atomistic details about the hydration of ions in aqueous solutions are still debated due to the disordered and statistical nature of the hydration process. However, many processes from biology, physical chemistry to materials sciences rely on the complex interplay between solute and solvent. Oxygen K-edge X-ray excitation spectra provide a sensitive probe of the local atomic and electronic surrounding of the excited sites. We used ab initio molecular dynamics simulations together with extensive spectrum calculations to relate the features found in experimental oxygen K-edge spectra of a concentration series of aqueous NaCl with the induced structural changes upon solvation of the salt and distill the spectral fingerprints of the first hydration shells around the Na + - and Cl - -ions. By this combined experimental and theoretical approach, we find the strongest spectral changes to indeed result from the first hydration shells of both ions and relate the observed shift of spectral weight from the post- to the main-edge to the origin of the post-edge as a shape resonance.

In this review article, selected, latest theoretical, and experimental developments in the field of nucleation and crystal growth of inorganic materials from aqueous solution are highlighted, with a focus on literature after 2015 and on non-classical pathways. A key point is to emphasize the so far underappreciated role of water and solvent entropy in crystallization at all stages from solution speciation through to the final crystal. While drawing on examples from current inorganic materials where non-classical behavior has been proposed, the potential of these approaches to be adapted to a wide-range of systems is also discussed, while considering the broader implications of the current re-assessment of pathways for crystallization. Various techniques that are suitable for the exploration of crystallization pathways in aqueous solution, from nucleation to crystal growth are summarized, and a flow chart for the assignment of specific theories based on experimental observations is proposed., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

Background: The Textus Bioactiv Ag membrane is an active dressing for the treatment of chronic wounds such as venous stasis ulcers and burns., Objectives: Determination of the transport and internal energy conversion properties of the Textus Bioactiv Ag membrane using the Kedem-Katchalsky-Peusner model. This model introduces the coefficients Lij necessary to calculate the degree of coupling (lij, QL), energy conversion efficiency (eij), dissipated energy (S-energy), free energy (F-energy), and internal energy (U-energy)., Material and Methods: The research material was the Textus Bioactiv Ag membrane that is used as an active dressing in the treatment of difficult-to-heal wounds, and KCl aqueous solutions. The research methods employed Peusner's formalism of network thermodynamics and Kedem and Katchalsky's thermodynamics of membrane processes. To calculate the Lij coefficients, we used hydraulic conductivity (Lp), diffusion conductivity (ů) and reflection (ó) coefficients to perform experimental measurements in different conditions., Results: The Lp coefficient for the Textus Bioactiv Ag membrane is nonlinearly dependent on the average concentrations of the solutions. In turn, the ů and ó coefficients are nonlinearly dependent on the differences in osmotic pressures (Äđ). An increase in the Äđ causes the Textus Bioactiv Ag membrane to become more permeable and less selective for KCl solutions. The coefficients of Peusner (Lij), couplings (lij, QL), energy conversion efficiency (eij), S-energy, F-energy, and U-energy also depend nonlinearly on Äđ. Our results showed that for higher concentrations of KCl solutions transported through the Textus Bioactiv Ag membrane, the coupling and energy conversion coefficients were greater for larger Äđ up to their maximum values for large Äđ. Coupling of the membrane structure with the electrolyte flux through the membrane is observed for Äđ greater than 10 kPa., Conclusions: Textus Bioactiv Ag membrane dressings possess the properties of a solution component separator as well as an internal energy converter.

Intermolecular interactions in protein solutions, in general, contain many contributions. If short-range attractions dominate, the state diagram exhibits liquid-liquid phase separation (LLPS) that is metastable with respect to crystallization. In this case, the extended law of corresponding states (ELCS) suggests that thermodynamic properties are insensitive to details of the underlying interaction potential. Using lysozyme solutions, we investigate the applicability of the ELCS to the static structure factor and how far effective colloidal interaction models can help to rationalize the phase behavior and interactions of protein solutions in the vicinity of the LLPS binodal. The (effective) structure factor has been determined by small-angle x-ray scattering. It can be described by Baxter's adhesive hard-sphere model, which implies a single fit parameter from which the normalized second virial coefficient b 2 is inferred and found to quantitatively agree with previous results from static light scattering. The b 2 values are independent of protein concentration but systematically vary with temperature and solution composition, i.e., salt and additive content. If plotted as a function of temperature normalized by the critical temperature, the values of b 2 follow a universal behavior. These findings validate the applicability of the ELCS to globular protein solutions and indicate that the ELCS can also be reflected in the structure factor.

Water dynamics is essential to biochemical processes by mediating all such reactions, including biomolecular degeneration in solutions. To disentangle the molecular-scale distribution of water dynamics around a solute biomolecule, we investigated here the rotational dynamics of water around lysozyme by combining molecular dynamics (MD) simulations and broadband dielectric spectroscopy (BDS). A statistical analysis using the relaxation times and trajectories of every single water molecule was proposed, and the two-dimensional probability distribution of water at a distance from the lysozyme surface with a rotational relaxation time was given. For the observed lysozyme solutions of 34-284 mg/mL, we discovered that the dielectric relaxation time obtained from this distribution agrees well with the measured γ relaxation time, which suggests that rotational self-correlation of water molecules underlies the gigahertz domain of the dielectric spectra. Regardless of protein concentration, water rotational relaxation time versus the distance from the lysozyme surface revealed that the water rotation is severely retarded within 3 Å from the lysozyme surface and is nearly comparable to pure water when farther than 10 Å. The dimension of the first hydration layer was subsequently identified in terms of the relationship between the acceleration of water rotation and the distance from the protein surface.

Molecular tweezers feature the first class of artificial receptors to pique the interest of researchers and emerge as an effective therapeutic candidate. The exceptional structure and exquisite binding specificity of tweezers establish this overall class of receptors as a promising tool, with abundant applications. However, their inclination to self-aggregate by mutual π-π stacking interactions of their aromatic arms diminishes their efficacy as a therapeutic candidate. Therefore, following up on sporadic studies, since the discovery of the Hofmeister series, on the ability of ions to either solvate (salting-in) or induce aggregation (salting-out) of hydrophobic solutes, the notions of ion-specificity effects are utilized on tweezer moieties. The impacts of three different aluminum salts bearing anions Cl - , ClO 4 - and SCN - on the self-association propensity of Whitlock's caffeine-pincered molecular tweezers are investigated, with a specific emphasis placed on elucidating the varied behavior of the ions on the hydration ability of tweezers. The comparative investigation is conducted employing a series of all-atom molecular dynamics simulations of five tweezer molecules in pure water and three salt solutions, at two different concentrations each, maintaining a temperature of 300 K and a pressure of 1 atm, respectively. Radial distribution functions, coordination numbers, and SASA calculations display a steady reduction in the aggregation proclivity of the receptor molecules with an increase in salt concentration, as progressed along the Hofmeister series. Orientational preferences between the tweezer arms reveal a disruptive effect in the regular π-π stacking interactions, in the presence of high concentrations of ClO 4 - and SCN - ions, while preferential interactions and tetrahedral order parameters unveil the underlying mechanism, by which the anions alter the solubility of the hydrophobic molecules. Overall, it is observed that SCN - exhibits the highest salting-in effect, followed by ClO 4 - , with both anions inhibiting tweezer aggregation through different mechanisms. ClO 4 - ions impart an effect by moderately interacting with the solute molecules as well as modifying the water structure of the bulk solution promoting solvation, whereas, SCN - ions engage entirely in interaction with specific tweezer sites. Cl - being the most charge-dense of the three anionic species experiences stronger hydration and therefore, imparts a very negligible salting-in effect.

To gain quantitative insight into how the overall strength of the hydrophobic interaction varies with the molecular size, we calculate osmotic second virial coefficients B for hydrophobic spherical molecules of different diameters σ in water based on molecular simulation with corrections to the finite-size and finite-concentration effects. It is shown that B (<0) changes by two orders of magnitude greater as σ increases twofold and its solute-size dependence is best fit by a power law B ∝ σ α with the exponent α ≃ 6, which contrasts with the cubic power law that the second virial coefficients of gases obey. It is also found that values of B for the solutes in a nonpolar solvent are positive but they obey the same power law as in water. A thermodynamic identity for B derived earlier [K. Koga, V. Holten, and B. Widom, J. Phys. Chem. B 119, 13391 (2015)] indicates that if B is asymptotically proportional to a power of σ, the exponent α must be equal to or greater than 6.

Grid Inhomogeneous Solvation Theory (GIST) has proven useful to calculate localized thermodynamic properties of water around a solute. Numerous studies have leveraged this information to enhance structure-based binding predictions. We have recently extended GIST toward chloroform as a solvent to allow the prediction of passive membrane permeability. Here, we further generalize the GIST algorithm toward all solvents that can be modeled as rigid molecules. This restriction is inherent to the method and is already present in the inhomogeneous solvation theory. Here, we show that our approach can be applied to various solvent molecules by comparing the results of GIST simulations with thermodynamic integration (TI) calculations and experimental results. Additionally, we analyze and compare a matrix consisting of 100 entries of ten different solvent molecules solvated within each other. We find that the GIST results are highly correlated with TI calculations as well as experiments. For some solvents, we find Pearson correlations of up to 0.99 to the true entropy, while others are affected by the first-order approximation more strongly. The enthalpy-entropy splitting provided by GIST allows us to extend a recently published approach, which estimates higher order entropies by a linear scaling of the first-order entropy, to solvents other than water. Furthermore, we investigate the convergence of GIST in different solvents. We conclude that our extension to GIST reliably calculates localized thermodynamic properties for different solvents and thereby significantly extends the applicability of this widely used method.