Preferential Hydration Research Articles

Modulation of Biomolecular Liquid-Liquid Phase Separation by Preferential Hydration and Interaction of Small Osmolytes with Proteins.

We examined the effects of trimethylamine N-oxide (TMAO) and urea (known osmolytes) on the liquid-liquid phase separation (LLPS) of fused in sarcoma (FUS) and three FUS-LLPS states: LLPS states at atmospheric pressure with low- and high-salt concentrations and a re-entrant LLPS state above 2 kbar. Temperature- and pressure-scan turbidity measurements revealed that TMAO and urea contributed to stabilizing and destabilizing LLPS, respectively. These results can be attributed to the excluded volume effect of TMAO (preferential hydration) and preferential interaction of urea with proteins. Additionally, TMAO counteracted the effects of equimolar urea on LLPS, a phenomenon not previously reported. The concept of the m-value for osmolyte-induced protein folding and unfolding can be applied to the osmolyte's effects on LLPS. In conclusion, biomolecular LLPS can be modulated by preferential hydration and the interaction of small osmolytes with proteins, thereby facilitating LLPS formation, even in extreme environments characterized by high-salt, high-urea, and high-pressure conditions.

The Salt-Induced Diffusiophoresis of Nonionic Micelles-Does the Salt-Induced Growth of Micelles Influence Diffusiophoresis?

Salt-induced diffusiophoresis is the migration of a colloidal particle in water due to a directional salt concentration gradient. An important example of colloidal particles is represented by micelles, generated by surfactant self-assembly in water. For non-ionic surfactants containing polyethylene glycol (PEG) groups, PEG preferential hydration at the micelle-water interface is expected to drive micelle diffusiophoresis from high to low salt concentration. However, micelles are reversible supramolecular assemblies, with salts being able to promote a significant change in micelle size. This phenomenon complicates the description of diffusiophoresis. Specifically, it is not clear to what extent the salt-induced growth of micelles affects micelle diffusiophoresis. In this paper, a multiple-equilibrium model is developed for assessing the contribution of the micelle growth and preferential hydration mechanisms to the diffusiophoresis of non-ionic micelles. The available experimental data characterizing the effect of NaCl on Triton X-100 aggregation number are combined with data on diffusiophoresis and the preferential hydration of PEG chains to show that the contribution of the micelle growth mechanism to overall diffusiophoresis is small compared to that of preferential hydration.

Comparison of Different Extraction and Purification Methods of Lime Peel Pectin and Evaluation of Physiochemical, Rheological, and Textural Properties

Background:: Pectin production has recently attracted considerable research interest due to its various applications arising from its unique characteristics. Lime peel, as a by-product of juice factories, has a promising potential for pectin extraction. Methods:: Lime peel pectin samples were extracted by three extraction processes: a) 90°C of heating for 120 min, b) 90°C of heating for 90 min and then 32 min of sonication, and c) 80°C of heating for 60 min and then 22 min of sonication. Then, they were purified either by ethanol or sodium caseinate (SC) and characterized. Results:: SC purification did not enhance the pectin yield; rather, it diminished the level of nonpectin components and resulted in purer pectin (i.e., lower sugar content). The samples purified with SC showed much lower viscosity in solution and storage modulus than the samples purified with ethanol, which could be attributed to their lower sugar content and higher pH (~ 4.6 vs. 2). However, pectin samples purified with SC had a relatively high sugar gel consistency, maybe due to protein retention in their structure as well as the preferential hydration effect of added sucrose. Conclusion:: The compact and extended conformations of the pectin sample, which was extracted by “(c) extraction method” and purified with ethanol, resulted in its high viscosity and storage modulus in solution and the highest gel consistency (16.91 Kg.s) compared to the other samples. Regardless of the conditions of extraction procedures, the purification method had a considerable impact on the pectin samples’ characteristics and potential applications.

Thermal properties of glycinin in crowded environments

Crowded environments, commonly found in the food system, are utilized to enhance the properties of soybean proteins. Despite their widespread application, little information exists regarding the impact of crowded environments on the denaturation behaviors of soybean proteins. In this study, we investigated how crowding agents with varying molecular weights, functional groups, and topology affect the denaturation behavior of glycinin under crowded conditions. The results reveal that thermal stability in PEG crowded environments is mainly influenced by both preferential hydration and binding. The stabilization is primarily enthalpy-driven, with aggregation contributing additional entropic stabilization. Specifically, ethylene glycol and diethylene glycol exhibit temperature-dependent, bilateral effects on glycinin stability. At the denaturation temperature, hydrophobic interactions play a predominant role, decreasing glycinin's thermal stability. However, at a molecular weight of 200 g/mol, there is a delicate balance between destabilizing and stabilizing effects, leading to no significant change in thermal stability. With the addition of PEG 400, 1000, and 2000, besides preferential hydration, additional hard-core repulsions between glycinin molecules enhance thermal stability. Methylation modification experiments demonstrated that 2-methoxyethyl ether exerted a more pronounced denaturing effect. Additionally, the cyclization of PEG 1000 decreased its stabilizing effect.

Human Serum Albumin in the Presence of Small Platinum Nanoparticles

Noble metal materials, especially platinum nanoparticles (Pt NPs), have immense potential in nanomedicine as therapeutic agents on account of their high electron density and their high surface area. Intravenous injection is proposed as the best mode to deliver the product to patients. However, our understanding of the reaction of nanoparticles with blood components, especially proteins, is far behind the explosive development of these agents. Using synchrotron radiation circular dichroism (SRCD), we investigated the structural and stability changes of human serum albumin (HSA) upon interaction with PEG-OH coated Pt NPs at nanomolar concentrations, conditions potentially encountered for intravenous injection. There is no strong complexation found between HSA and Pt NPs. However, for the highest molar ratio of NP:HSA of 1:1, an increase of 18 °C in the thermal unfolding of HSA was observed, which is attributed to increased thermal stability of HSA generated by preferential hydration. This work proposes a new and fast method to probe the potential toxicity of nanoparticles intended for clinical use with intravenous injection.

Protein Preferential Solvation in (Sucralose + Water) Mixtures.

Addition of sugars such as sucrose to aqueous protein solutions generally stabilizes proteins against thermal denaturation by preferential exclusion of sugars from proteins (preferential hydration of proteins). In this study, we investigated the effect of sucralose, a chlorinated sucrose derivative, on protein stability and preferential solvation. Circular dichroism and small-angle X-ray scattering measurements showed that sucrose increased the denaturation temperature of myoglobin and was preferentially excluded from the protein, whereas sucralose decreased the denaturation temperature of myoglobin and was preferentially adsorbed to the protein. No clear evidence was obtained for the indirect effects of sucralose on protein destabilization via the structure and properties of solvent water from the physicochemical properties (mass density, sound velocity, viscosity, and osmolality) of aqueous sucralose solutions; therefore, we concluded that a direct protein-sucralose interaction induced protein destabilization.

Influence of ion and hydration atmospheres on RNA structure and dynamics: insights from advanced theoretical and computational methods.

RNA, a highly charged biopolymer composed of negatively charged phosphate groups, defies electrostatic repulsion to adopt well-defined, compact structures. Hence, the presence of positively charged metal ions is crucial not only for RNA's charge neutralization, but they also coherently decorate the ion atmosphere of RNA to stabilize its compact fold. This feature article elucidates various modes of close RNA-ion interactions, with a special emphasis on Mg2+ as an outer-sphere and inner-sphere ion. Through examples, we highlight how inner-sphere chelated Mg2+ stabilizes RNA pseudoknots, while outer-sphere ions can also exert long-range electrostatic interactions, inducing groove narrowing, coaxial helical stacking, and RNA ring formation. In addition to investigating the RNA's ion environment, we note that the RNA's hydration environment is relatively underexplored. Our study delves into its profound interplay with the structural dynamics of RNA, employing state-of-the-art atomistic simulation techniques. Through examples, we illustrate how specific ions and water molecules are associated with RNA functions, leveraging atomistic simulations to identify preferential ion binding and hydration sites. However, understanding their impact(s) on the RNA structure remains challenging due to the involvement of large length and long time scales associated with RNA's dynamic nature. Nevertheless, our contributions and recent advances in coarse-grained simulation techniques offer insights into large-scale structural changes dynamically linked to the RNA ion atmosphere. In this connection, we also review how different cutting-edge computational simulation methods provide a microscopic lens into the influence of ions and hydration on RNA structure and dynamics, elucidating distinct ion atmospheric components and specific hydration layers and their individual and collective impacts.

Protein stability in a natural deep eutectic solvent: Preferential hydration or solvent slaving?

Deep eutectic solvents (DESs) emerged as potential alternative solvent media in multiple areas, including biomolecular (cryo)preservation. Herein, we studied the stability of a small protein (ubiquitin) in water and a betaine-glycerol-water (B:G:W) (1:2:ζ; ζ = 0, 1, 2, 5, 10) DES, through molecular dynamics. An AMBER-based model that accurately describes the density and shear viscosity of the DES is proposed. We find that water molecules are largely trapped in the solvent, precluding the formation of a full hydration layer, seemingly opposite to osmolytes’ preferential exclusion/preferential hydration mechanism. Although the protein is stable in the DES, structural fluctuations are largely suppressed and only recovered upon sufficient hydration. This is explained by a solvent-slaving mechanism where β-fluctuations are key, with the non-monotonic hydration of some amino acids with the water content providing an explanation to the non-monotonic folding of some proteins in aqueous DESs. A major thermal stability enhancement in the DES is also observed, caused by a similar slowdown of the backbone torsional dynamics. Our results support a kinetic stabilization of the protein in the DES, whereas a possible thermodynamic stabilization does not follow a preferential hydration or water entrapment mechanism.

Effect of Ligand Binding on Polymer Diffusiophoresis

Diffusiophoresis is the migration of a macromolecule in response to a concentration gradient of a cosolute in liquids. Diffusiophoresis of polyethylene glycol (PEG) in water occurs from high to low concentration of trimethylamine-N-oxide (TMAO). This is consistent with the preferential hydration of PEG observed in the presence of TMAO. In other words, PEG migrates in the direction in which it lowers its chemical potential. On the other hand, although PEG is found to preferentially bind urea in water, PEG diffusiophoresis still occurs from high to low urea concentration. Thus, PEG migrates in the direction that increases its chemical potential in the urea case. Here, a ligand-binding model for polymer diffusiophoresis in the presence of a cosolute that preferentially binds to polymer is developed. It includes both actual polymer–ligand binding and the effect of the polymer on cosolute thermodynamic activity. This model shows that polymer–cosolute binding has a marginal effect on polymer diffusiophoresis and indicates that weak repulsive interactions, such as hard-core exclusion forces, are the main factor responsible for the observed PEG diffusiophoresis from high to low urea concentration. This work contributes to a better understanding of diffusiophoresis of macromolecules in response to gradients of nonelectrolytes.

Role of preferential hydration on diffusiophoresis of globular proteins

Diffusiophoresis is the migration of a colloidal particle through a fluid, caused by a cosolute concentration gradient. Preferential hydration is a thermodynamic phenomenon responsible for particle diffusiophoresis from high to low cosolute concentration in water. Here, steady-state Navier-Stokes equation for incompressible fluids, with particle modeled as an inpenetrable rigid sphere, is employed for deriving a mathematical expression of the diffusiophoresis coefficient. Mean-force potentials with arbitrary interaction range but with interaction energies small or comparable with thermal energy are employed to describe water-mediated particle-cosolute interactions. This choice of potential is movitated by previous work showing that only fluid particles weakly interacting with the colloildal particle can cause diffusiophoresis. Preferential hydration has been extensively investigated for proteins. Thus, the proposed model is applied to available experimental diffusiophoresis coefficients of lysozyme in aqueous NaCl and KCl at pH 4.5 and 25 °C. This analysis also includes data on salt osmotic diffusion, describing salt diffusion caused by protein concentration gradients. The preferential-hydration contribution of experimental lysozyme diffusiophoresis is obtained after removing electrophoretic diffusiophoresis. Examination of these experimental data shows that the mean-force potential describing preferential hydration is indeed weak, with an interaction range that is an appreciable fraction of particle size.

Determinants for macromolecular crowding-induced thermodynamic stabilization of acid-denatured cytochrome c to molten globules

The macromolecular crowding effect transforms the acid-denatured ferricytochrome c (cyt cIII) (UA-state) to molten-globule (MGMC-state) at pH 1.85. Crowding-induced stabilization free energy (ΔΔG) and preferential hydration ΔΓW were estimated for the UA → MGMC transition. The magnitudes of ΔΔG and ΔΓW were found to be decreased as dextran 70 (D70) > dextran 40 (D40) > ficoll 70 (F70), which demonstrates that ΔΔG and ΔΓW track the molecular size and shape of the crowder towards refolding and stabilization of UA-state to MGMC-state. Analysis of effects of crowders (D40, D70, F70) on thermal and chemical-denaturations of acid-denatured cyt cIII provided several important information, (i) macromolecular crowding increased the thermodynamic stability of acid-denatured cyt cIII, (ii) concentration, size and shape of crowder control the crowding-induced thermodynamic stabilization of MGMC-state, (iii) crowding effect increased the thermal-denaturation midpoint (Tm) with a slight change in enthalpy (ΔHm), suggesting that the steric-excluded volume effect contributes to the crowding-induced increased thermal stability of the acid-denatured protein. Analysis of entropy − enthalpy plots for D40, D70, and F70 reveals that in addition to the steric-excluded volume effect, the enthalpic contribution is also added to the macromolecular crowding-induced stabilization of acid-denatured cyt cIII. The dilute-medium, compound-crowder, purely entropic-crowder and purely enthalpic-crowder curves were obtained for acid-denatured cyt cIII for D70, D40 and F70. The crossover temperature, Tx was calculated from the dilute and compound-crowder curves. The Tx values measured for D40, D70, and F70 were found to be ∼ 250.15 K, 272.15 K, and 275.15 K, respectively, which suggests that the Tx value depends on the size and shape of the crowder. Furthermore, the observation of a lower value of Tx and a minor enthalpic component for D40, D70, and F70 is likely due to the formation of weaker soft interactions of acid-denatured cyt cIII with D40, D70, and F70.

Molecular details of ovalbumin solvation by an aqueous solution of xylitol in different pH environment:Ultrasonic and molecular simulation studies

Artificial sweetener-protein interactions are playing a major role in enhancing the functional properties of protein-based food and pharmaceutical products. This article discusses the molecular details of ovalbumin (OA) solvation in an aqueous solution of xylitol (XY) in different pH environments. This task can be accomplished by both Ultrasonic and Molecular Simulation studies. In ultrasonic studies, density, ultrasound velocity, viscosity, and surface tension have been measured for OA in various pH of phosphate buffer with and without XY. Further, some of the calculated parameters such as adiabatic compressibility, intermolecular free length, free volume, etc have been worked out. From ultrasonic results, pH dependent preferential hydration of OA was noticed in the presence of XY in an aqueous environment. In Molecular Dynamics Simulation (MDS) studies, water and XY accumulation to OA surface for different pH models were analyzed. The different states of protonation of the OA surface promote two distinct effects on the solvent and cosolvent orientation.

Osmolytes: Wonder molecules to combat protein misfolding against stress conditions

The proper functioning of any protein depends on its three dimensional conformation which is achieved by the accurate folding mechanism. Keeping away from the exposed stress conditions leads to cooperative unfolding and sometimes partial folding, forming the structures like protofibrils, fibrils, aggregates, oligomers, etc. leading to several neurodegenerative diseases like Parkinson's disease, Alzheimer's, Cystic fibrosis, Huntington, Marfan syndrome, and also cancers in some cases, too. Hydration of proteins is necessary, which may be achieved by the presence of organic solutes called osmolytes within the cell. Osmolytes belong to different classes in different organisms and play their role by preferential exclusion of osmolytes and preferential hydration of water molecules and achieves the osmotic balance in the cell otherwise it may cause problems like cellular infection, cell shrinkage leading to apoptosis and cell swelling which is also the major injury to the cell. Osmolyte interacts with protein, nucleic acids, intrinsically disordered proteins by non-covalent forces. Stabilizing osmolytes increases the Gibbs free energy of the unfolded protein and decreases that of folded protein and vice versa with denaturants (urea and guanidinium hydrochloride). The efficacy of each osmolyte with the protein is determined by the calculation of m value which reflects its efficiency with protein. Hence osmolytes can be therapeutically considered and used in drugs.

Mechanisms of polyphosphate-induced amyloid fibril formation triggered by breakdown of supersaturation.

Much effort has been devoted to elucidate mechanisms of amyloid fibril formation using various kinds of additives, such as salts, metals, detergents, and biopolymers. Here, we review the effects of additives with a focus on polyphosphate (polyP) on amyloid fibril formation of β2-microglobulin (β2m) and α-synuclein (αSyn). PolyP, consisting of up to 1,000 phosphoanhydride bond-linked phosphate monomers, is one of the most ancient, enigmatic, and negatively charged molecules in biology. Amyloid fibril formation of both β2m and αSyn could be accelerated by counter anion-binding and preferential hydration at relatively lower and higher concentrations of polyP, respectively, depending on the chain length of polyP. These bimodal concentration-dependent effects were also observed in salt- and heparin-induced amyloid fibril formation, indicating the generality of bimodal effects. We also address the effects of detergents, alcohols, and isoelectric point precipitation on amyloid fibril formation, in comparison with the effects of salts. Because polyP is present all around us, from cellular components to food additives, clarifying its effects and consequent biological roles will be important to further advance our understanding of amyloid fibrils. This review article is an extended version of the Japanese article, Linking Protein Folding to Amyloid Formation, published in SEIBUTSU BUTSURI Vol. 61, p. 358-365 (2021).

Prevention of insulin fibrillation by biocompatible choline-amino acid based ionic liquids: Biophysical insights

We have synthesized biocompatible ionic liquids (ILs) with choline as cation and amino acids as anions to explore their potential towards prevention of fibrillation in insulin and the obtain corresponding mechanistic insights. This has been achieved by examining the effect of these ILs on insulin at the nucleation, elongation and maturation stages of the fibrillation process. A combination of high sensitivity isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) have been employed along with spectroscopy and microscopy to evaluate interaction of the ILs at each stage of fibrillation quantitatively. Choline glycinate is observed to provide maximum stabilization to insulin compared to that provided by choline prolinate, choline leucinate, and choline valinate. This increased thermal stabilization has direct correlation with the extent of reduction in the fibrillation of insulin by ILs determined using Thioflavin T and 8-anilinonaphthalene sulfonate based fluorescence assays. ITC has permitted understanding nature of interaction of the ILs with the protein at different fibrillation stages in terms of standard molar enthalpy of interaction whereas DSC has enabled understanding the extent of reduction in thermal stability of the protein at these stages. These ILs are able to completely inhibit formation of insulin aggregates at a concentration of 50 mM. Stabilization of proteins by ILs could be explained based on involvement of preferential hydration process. The work provides biocompatible IL based approach in achieving stability and prevention of fibrillation in insulin.

Diffusiophoresis of a Nonionic Micelle in Salt Gradients; Roles of Preferential Hydration and Salt-Induced Surfactant Aggregation.

Diffusiophoresis is the migration of a colloidal particle in water driven by concentration gradients of cosolutes such as salts. We have experimentally characterized the diffusiophoresis of tyloxapol micelles in the presence of MgSO4, a strong salting-out agent. Specifically, we determined the multicomponent-diffusion coefficients using Rayleigh interferometry, cloud points, and dynamic-light-scattering diffusion coefficients on the ternary tyloxapol-MgSO4-water system at 25 °C. Our experimental results show that micelle diffusiophoresis occurs from a high to a low salt concentration (positive diffusiophoresis). Moreover, our data were used to characterize the effect of salt concentration on micelle size and salt osmotic diffusion, which occurs from a high to a low surfactant concentration. Although micelle diffusiophoresis can be attributed to the preferential hydration of the polyethylene glycol surface groups, salting-out salts also promote an increase in the size of micellar aggregates, ultimately leading to phase separation at high salt concentration. This complicates diffusiophoresis description, as it is not clear how salt-induced surfactant aggregation contributes to micelle diffusiophoresis. We, therefore, developed a two-state aggregation model that successfully describes the observed effect of salt concentration on the size of tyloxapol micelles, in the case of MgSO4 and the previously reported case of Na2SO4. Our model was then used to theoretically evaluate the contribution of salt-induced aggregation to diffusiophoresis. Our analysis indicates that salt-induced aggregation promotes micelle diffusiophoresis from a low to a high salt concentration (negative diffusiophoresis). However, we also determined that this mechanism marginally contributes to overall diffusiophoresis, implying that preferential hydration is the main mechanism causing micelle diffusiophoresis. Our results suggest that sulfate salts may be exploited to induce the diffusiophoresis of PEG-functionalized particles such as micelles, with potential applications to microfluidics, enhanced oil recovery, and controlled-release technologies.

Influence of amino acids on alkaline pH induced partially folded molten globule like intermediate of bovine serum albumin: Conformational and thermodynamic insights

Partially folded states of proteins can misfold or aggregate leading to various neurodegenerative diseases or disorders. Therefore stabilization of the partially folded states of proteins towards native conformation is important. Here, we investigate the effects of glycine, l-alanine, DL- α – aminobutyric acid, l-lysine, l-leucine and l-valine on the stability of molten globule like partially folded state of bovine serum albumin (BSA) at pH 11.2. We report the changes in the Trp microenvironment of the BSA at pH 11.2 by these amino acids. Except for l-leucine and l-valine, the other four amino acids impart thermal stabilization to partially folded MG like intermediate of BSA at pH 11.2. CD spectroscopy is employed to analyse tertiary conformation of BSA. We perform the ITC to study the interaction of BSA with these amino acids at pH 11.2. The spectroscopic in combination with calorimetric observations have enabled monitoring amino acid-induced conformational changes in BSA at pH 11.2 suggesting their osmolyte behavior. The results suggest significance of preferential hydration of partially folded proteins and the stability offered by the amino acids.

Salt-induced diffusiophoresis of a nonionic micelle: Roles of salting out and proximity to surfactant cloud point

• Salt-induced diffusiophoresis is the migration of a colloidal particle in water caused by a salt concentration gradient. • Tyloxapol micelle was identified as model particle with surface properties governed by polyethylene glycol (PEG) chains. • Na 2 SO 4 was chosen because it is a common salt and a strong salting-out agent according to Hofmeister series. • Gradient of Na 2 SO 4 drives micelle diffusiophoresis from high to low salt concentration due to PEG preferential hydration. • Near surfactant cloud point, diffusiophoresis becomes dominant mechanism responsible for micelle transport. Salt-induced diffusiophoresis is the migration of colloidal particles in water caused by salt concentration gradients. A widespread example of colloidal particles is represented by those with interfacial properties governed by polyethylene glycol (PEG) functionalities. Since salting-out salts strongly affect PEG-water interactions, their gradients are expected to generate diffusiophoresis of PEG-based particles. In this work, diffusiophoresis of nonionic micelles of tyloxapol, a polyoxyethylene surfactant, was characterized in the presence of Na 2 SO 4 . Specifically, multicomponent-diffusion coefficients were measured at 25 °C for the ternary tyloxapol-Na 2 SO 4 -water system using Rayleigh interferometry. These transport data, together with measurements of cloud points and dynamic-light-scattering diffusion coefficients, were used to determine the effect of salt concentration on micelle mobility, salt-induced micelle diffusiophoresis and salt osmotic diffusion induced by micelle gradients. It was found that gradients of Na 2 SO 4 induce micelle diffusiophoresis from high to low salt concentration. Moreover, diffusiophoresis becomes the dominant mechanism responsible for micelle transport near surfactant cloud point due to increase in both micelle size and osmotic compressibility with salt concentration. A hydration model was employed to theoretically describe salt salting-out effect on micelle diffusiophoresis and salt osmotic diffusion. This work is the first report showing salt-induced diffusiophoresis of a neutral PEG-based colloidal particle and characterizing its magnitude near miscibility gaps.

Ionic liquid solvation of proteins in native and denatured states

Ionic liquids (ILs) are utilized as enzymatic reaction solvents and as protein structure protectants or denaturants in biotechnological applications. They can develop a wide spectrum of interactions with macromolecules due to their chemical complexity. Understanding how ILs interact with protein conformations is crucial to fine-tuning their action. Here, we investigate the solvation of different ubiquitin folding states in aqueous solutions of four ionic liquids formed by the combination of the cations 1-Ethyl-3-methylimidazolium (EMIM), and 1-Butyl-3-methylimidazolium (BMIM), and the anions Tetrafluoroborate (BF4), and Dicyanamide (DCA). The structure and thermodynamics of the interactions between the protein in various denaturation states and the ILs were evaluated using minimum-distance distribution functions (MDDFs) and the Kirkwood-Buff (KB) theory of solutions. Under most circumstances, the ILs preferentially solvate the protein structures, and are thus considered denaturants. However, even when preferential hydration is obtained for the native structure, denaturation is favored because of strong IL preferential binding to the denatured states. As the protein undergoes denaturation, its surface area increases, and residues with decreased polarity are exposed. The ILs interact favorably with these residues, excluding water, cooperatively stabilizing the exposure of the protein core. Strong specific DCA-protein interactions, which jointly draw cations to the protein surface due to electrostatic correlations, render ILs containing the anion DCA stronger denaturants than those containing BF4.

Effects of surface wettability on (001)-WO[formula omitted] and (100)-WSe[formula omitted]: A spin-polarized DFT-MD study

An extensive understanding of WO3 and WSe2 bulk crystalline structures and explicit solvent effects on (001)-WO3 and (100)-WSe2 facets are essential for design of efficient (photo) electrocatalysts. The atomistic level understanding of both WO3 and WSe2 bulk solids and how water solvation processes occur on WO3 and WSe2 facets are nowadays characterized by a noticeable lack of knowledge.Herein, forefront Density Functional Theory-based molecular dynamics have been conducted for assessing the role of an explicit water environment in the characterization of solid surfaces. Water at the interface and H-bonds environment, as well as WO3 and WSe2 surface activity, will be described in terms of surface wettability and interfacial water dynamics, revealing the relevance of treating explicitly liquid water and its dynamics in assessing catalytic features. We provide pieces of evidence of the hydrophobic character shown by (001)-WO3 and (100)-WSe2 facets. A preferential in-plane hydration structure of the first water layer has been detected at both (001)-WO3 and (100)-WSe2 water interface, in which the electric dipole moment of water molecules is re-oriented in a sort of 2-dimensional H-bond network. Bulk property calculations of WO3 and WSe2 are also provided.