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Hypothesis Detergents used in everyday life for cleaning and washing are a source of water pollution and can have a negative effect on human health and the environment. To reduce their negative impact, a new trend of using only purified water for washing and cleaning applications is emerging. A scientific basis of this method needs to be established, as its mechanisms and the efficiency should be better understood. Experiments In this work, we investigate the effect of water purity on the removal of hydrophobic films from solid surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D) and gravimetric experiments. We compared the cleaning efficiency of TAP water, two grades of purified water, NaCl solution and SDS solution. Findings The QCM-D results show that both grades of purified water remove more than 90% of Vaseline deposited of the surface while tap water only 75%. SDS solution fully removes the deposited layer. Gravimetric experiments with removal of olive oil from hydrophilic and hydrophobic surfaces also indicate higher efficiency of purified water grades. Contact angle experiments show that pure water facilitates roll-up mechanism of cleaning. We suggest that due to lower ionic strength, purified water increases electrostatic repulsion and promotes the cleaning process.

The design of 3D printable bio-based hydrogels with enhanced mechanical properties and minimal chemical modification can open new opportunities in the field of biomedical applications. A facile and safe approach is proposed to prepare mechanically reinforced chitosan-based hydrogels via a phenolated polyelectrolyte complex (PHEC) and enzyme-mediated crosslinking. PHEC was formed between phenolated chitosan and alginate, leading to the formation of in situ phenol-functionalized microfibers that exhibited excellent 3D printability. The synergistic complexation enhanced the loss modulus (60 times), toughness, flexibility, and moldability of hydrogel as well as dynamic viscosity (20 times) of the hydrogel precursor compared to individual phenolated chitosan and alginate hydrogels. This complexation endowed the material with excellent printability without sacrificing the hydrogel's elasticity. This study proposes a strategy to design tough and 3D printable marine-based hydrogels based on the synergistic complexation of a phenolated polyelectrolyte complex and enzyme-mediated crosslinking.

In this work, the effects of pH and high acyl gellan gum concentration on the adsorption kinetics and interfacial dilatational rheology of sodium caseinate/high acyl gellan gum (CN/HG) complexes were investigated using a pendant drop tensiometer. In addition, stability related properties including interfacial protein concentration, droplet charge, size, microstructure and creaming index of emulsions were studied at different HG concentration (0–0.2 wt%) and pH values (4, 5.5 and 7). The results showed that HG adsorbed onto the CN mainly through electrostatic interactions which could lead to increase the interfacial pressure (π), rates of protein diffusion (kdiff), and molecular penetration (kp). The CN/HG complexes formed thick adsorption layers around the oil droplets which significantly increased the surface dilatational modulus with the increasing HG concentration. The CN/HG complexes appeared to form more elastic interfacial films after a long-term adsorption time compared with CN alone, which could reduce the droplet coalescence and thus prevented the growth of emulsion droplets. All four phosphorylated proteins of CN (αs1-, αs2-, β-, and κ-casein) were adsorbed at the oil-water (O/W) interface as confirmed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), and surface protein coverage increased progressively with increasing HG concentration at pH 5.5, but decreased at pH 7. The CN/HG stabilized emulsions at pH 5.5 revealed the higher net charges and smaller z-average diameters than those at pH 4 and pH 7. This study provides valuable information on the use of CN/HG complexes to improve the stability and texture of food emulsions., Graphical abstract Image 1, Highlights •Interactions between sodium caseinate (CN) and high acyl gellan gum (HG) studied. •At pH 5.5, CN/HG interaction was mainly driven by electrostatic attractions. •CN/HG complex improved the adsorption of CN at the oil-water interface. •CN/HG complex could form stronger interfacial films than protein alone. •Cooperative adsorption onto oil-water interface improved emulsion stability.

Electrostatics is an important part of virus life. Understanding the detailed distribution of charges over the surface of a virus is important to predict its interactions with host cells, antibodies, drugs, and different materials. Using a coarse-grained model of the entire viral envelope developed by D. Korkin and S.-J. Marrink’s scientific groups, we created an electrostatic map of the external surface of SARS-CoV-2 and found a highly heterogeneous distribution of the electrostatic potential field of the viral envelope. Numerous negative patches originate mainly from negatively charged lipid domains in the viral membrane and negatively charged areas on the “stalks” of the spike (S) proteins. Membrane (M) and envelope (E) proteins with the total positive charge tend to colocalize with the negatively charged lipids. In the E protein pentamer exposed to the outer surface, negatively charged glutamate residues and surrounding lipids form a negative electrostatic potential ring around the channel entrance. We simulated the interaction of the antiviral octacationic photosensitizer octakis(cholinyl)zinc phthalocyanine with the surface structures of the entire model virion using the Brownian dynamics computational method implemented in ProKSim software (version r661). All mentioned negatively charged envelope components attracted the photosensitizer molecules and are thus potential targets for reactive oxygen generated in photosensitized reactions.

Polyelectrolytes have been at the center of interdisciplinary research for many decades. In the field of polymer science and soft matter, they have provided the dimensions of electrostatic interactions, which opens a vast variety of opportunities for new physical properties and applications. In biological matter, polyelectrolytes are present in many forms, from extracellular polysaccharides to complex DNA molecules and proteins. This review discusses the recent research on polyelectrolytes covering the fundamental level of their conformations and nanostructures, their molecular interactions with materials that have close relevance to bioapplications and their applications in the biomedical field. This approach is motivated by the fact that the polyelectrolyte research is constantly active in all the aforementioned levels and continually affects many critical scientific areas.

The extensive use of synthetic materials in modern society presents a great challenge to environmental and water quality. As such, numerous studies were dedicated to the removal of emerging contaminants from water using novel materials as sorbents or catalysts. With large reserves and low material costs, Earth material has also attracted great attention for contaminant removal. Halloysite is a 1:1 layered clay mineral with moderate cation exchange capacity that can be used for the removal of cationic contaminants. On the other hand, as it may bear positive charges on the aluminum hydroxyl sheets, it could be used to remove anionic contaminants. In this study, the removal of a cationic dye, methylene blue (MB), and an anionic dye, alizarin red S (ARS), from the water was evaluated from single and mixed solutions. The results suggested that from single solutions, MB removal was via cation exchange while ARS removal could have originated from anion exchange. From mixed solutions, their removal was mutually increased, which may be due to a synergistic effect in the presence of a type of charged dyes serving as counterions to enhance the sorption of dyes of opposite charges. This finding suggests that halloysite may serve as a sorbent for the removal of organic contaminants of different charges at the same time, which is a new perspective that needs further evaluation and expansion.

Thermophilic proteins and enzymes are attractive for use in industrial applications due to their resistance against heat and denaturants. Here, we report on a thermophilic protein that is stable at high temperatures (Ttrs, hot 67 °C) but undergoes significant unfolding at room temperature due to cold denaturation. Little is known about the cold denaturation of thermophilic proteins, although it can significantly limit their applications. We investigated the cold denaturation of thermophilic multidomain protein translation initiation factor 2 (IF2) from Thermus thermophilus. IF2 is a GTPase that binds to ribosomal subunits and initiator fMet-tRNAfMet during the initiation of protein biosynthesis. In the presence of 9 M urea, measurements in the far-UV region by circular dichroism were used to capture details about the secondary structure of full-length IF2 protein and its domains during cold and hot denaturation. Cold denaturation can be suppressed by salt, depending on the type, due to the decreased heat capacity. Thermodynamic analysis and mathematical modeling of the denaturation process showed that salts reduce the cooperativity of denaturation of the IF2 domains, which might be associated with the high frustration between domains. This characteristic of high interdomain frustration may be the key to satisfying numerous diverse contacts with ribosomal subunits, translation factors, and tRNA.

Nitrites are metastable anions that are derived from the oxidation of ammonia by agricultural pollution, sewage, decaying protein, and other nitrogen sources. They are a recognized environmental issue due to their role in eutrophication, as well as in surface and groundwater contamination, being toxic to almost all living creatures. Recently, we reported on the high efficiency of two cationic resins (R1 and R2) forming hydrogels (R1HG and R2HG) by dispersion in water in removing anionic dyes from water by electrostatic binding. Here, aiming at developing adsorbent materials for nitrite remediation, R1, R2, R1HG, and R2HG were first tested in adsorption experiments in batches monitored by UV–Vis methods, using the Griess reagent system (GRS) in order to assess their removal efficiency by contact over time. Particularly, samples of water appositely contaminated with nitrites were analyzed by UV–Vis before and during treatment with the hydrogels. The initial concentration of nitrites was quantified (118 mg/L). Then, the removal of nitrites over time, the removal efficiency of R1HG (89.2%) and of R2HG (89.6%), their maximum adsorption (21.0 mg/g and 23.5 mg/g), as well as the adsorption kinetics and mechanisms were evaluated. Additionally, R1HG- and R2HG-based columns (h = 8–10 cm, ØE = 2 cm) mimicking mini-scale decontamination systems by filtration were used to rapidly filter samples of water polluted with nitrite that were under pressure. R1HG and R2GH were capable of totally removing nitrites (99.5% and 100%) from volumes of nitrite solutions that were 118 mg/L that is 10 times the volumes of resins used. Additionally, when extending filtration to increasing volumes of the same nitrite solution up to 60 times the volume of resins used, the removal efficiently of R1HG decreased, and that of R2HG remained stable at over 89%. Interestingly, both the worn-out hydrogels were regenerable by 1% HCl washing, without a significant reduction in their original efficiency. There is a lack of studies in the literature reporting on novel methods to remove nitrite from water. R1HG and especially R2HG represent low-cost, up-scalable, and regenerable column-packing materials with promise for applications in the treatment of drinking water contaminated by nitrites.

Supramolecular structures obtained from protein–polysaccharide association may be applied to encapsulate bioactive compounds or to improve the physical stability and texture properties of colloid–based products. In this study, the interaction of 0.1 wt% soybean trypsin inhibitor (STI) with different concentrations of chitosan (CS) in aqueous solutions was investigated under different pH by the analysis of state diagram, turbidity, zeta potential, spectroscopy, and microstructure; the protective effect of STI–CS complex coacervates on STI stability in simulated gastric juice was also discussed. The results suggested that interactions between STI and CS could form soluble/insoluble complexes mainly through hydrophobic interactions (pH 4.0) or electrostatic interactions (pH 6.0). The CD spectra showed that the secondary structure of STI did not change significantly when CS with the same charge was mixed with STI, and the secondary structure of STI was slightly changed when CS with the opposite charge was mixed with STI. Simulated gastric digestion experiments showed that the complex formed by non-covalent bonding had a protective effect on the active protein. This study provides information about the effect of different CS concentrations and pH values on the formation of complexes of CS and STI in an aqueous solution and provides theoretical references for the construction of supramolecular-structured carrier substances based on CS and STI.

Ionic interactions are crucial to biological functions of DNA, RNA, and proteins. Experimental research on how ions behave around biological macromolecules has lagged behind corresponding theoretical and computational research. In the 21st century, quantitative experimental approaches for investigating ionic interactions of biomolecules have become available and greatly facilitated examinations of theoretical electrostatic models. These approaches utilize anomalous small-angle X-ray scattering, atomic emission spectroscopy, mass spectrometry, or nuclear magnetic resonance (NMR) spectroscopy. We provide an overview on the experimental methodologies that can quantify and characterize ions within the ion atmospheres around nucleic acids, proteins, and their complexes.

The structural stability of DNA is important because of its biological activity. DNAs due to their inherent chemical properties are not stable in an aqueous solution, therefore, a long period of storage of DNA at the ambient condition in bioscience is of importance. Ionic liquids (ILs) as interesting alternatives compared to organic solvents and water due to their considerable properties can be used as new agents to increase the stability of DNA for a long period of storage. In this article, molecular dynamics (MD) simulations and quantum chemistry calculations were applied to investigate the effects of amino acid ionic liquids ([BMIM][Ala], [BMIM][Gly], [BMIM][Val], [BMIM][Pro] and [BMIM][Leu]) on the dynamical behavior and the structural stability of calf thymus DNA. Based on the obtained MD results ILs enter into the solvation shell of the DNA and push away the water molecules from the DNA surface. Structural analysis shows that [BMIM]+ cations can occupy the DNA minor groove without disturbing the double-helical structure of DNA. ILs due to strong electrostatic and van der Waals (vdW) interactions with the DNA structure contribute to the stability of the double-helical structure. Quantum chemistry calculations indicate that the interactions between the [BMIM]+ cation and DNA structure has an electrostatic character. Moreover, this cation forms a more stable complex with the CGCG region of the DNA in comparison with AATT base pairs. Overall, the results of this study can provide new insight into the application of ILs for maintaining DNA stability during long-term storage. Communicated by Ramaswamy H. Sarma Theoretical methods reveal that amino acid ionic liquids can be good candidates for increasing the stability of DNA in long-term storage.

openaire: EC/H2020/101002258/EU//ProCrystal Heparin is a commonly applied blood anticoagulant agent in clinical use. After treatment, excess heparin needs to be removed to circumvent side effects and recover the blood-clotting cascade. Most existing heparin antidotes rely on direct heparin binding and complexation, yet selective compartmentalization and sequestration of heparin would be beneficial for safety and efficiency. However, such systems have remained elusive. Herein, a semipermeable protein-based microcompartment (proteinosome) is loaded with a highly positively charged chitosan derivative, which can induce electrostatics-driven internalization of anionic guest molecules inside the compartment. Chitosan-loaded proteinosomes are subsequently employed to capture heparin, and an excellent heparin-scavenging performance is demonstrated under physiologically relevant conditions. Both the highly positive scavenger and the polyelectrolyte complex are confined and shielded by the protein compartment in a time-dependent manner. Moreover, selective heparin-scavenging behavior over serum albumin is realized through adjusting the localized scavenger or surrounding salt concentrations at application-relevant circumstances. In vitro studies reveal that the cytotoxicity of the cationic scavenger and the produced polyelectrolyte complex is reduced by protocell shielding. Therefore, the proteinosome-based systems may present a novel polyelectrolyte-scavenging method for biomedical applications.

Interactions between carbonyl groups are prevalent in protein structures. Earlier investigations identified dominant electrostatic dipolar interactions, while others implicated lone pair n→π* orbital delocalisation. Here these observations are reconciled. A combined experimental and computational approach confirmed the dominance of electrostatic interactions in a new series of synthetic molecular balances, while also highlighting the distance‐dependent observation of inductive polarisation manifested by n→π* orbital delocalisation. Computational fiSAPT energy decomposition and natural bonding orbital analyses correlated with experimental data to reveal the contexts in which short‐range inductive polarisation augment electrostatic dipolar interactions. Thus, we provide a framework for reconciling the context dependency of the dominance of electrostatic interactions and the occurrence of n→π* orbital delocalisation in C=O⋅⋅⋅C=O interactions., Carbonyls reconciled: Electrostatics and orbital interactions have both been implicated in governing carbonyl interactions. A combined experimental and computational approach reconciles these conflicting explanations of the physiochemical origin of the interaction, demonstrating that orbital delocalisation augments electrostatic control, but for very close carbonyl contacts.

Calcium (Ca) and magnesium (Mg) are the most abundant alkaline-earth metal ions in nature, and their interaction with ferrihydrite (Fh) affects the geochemical cycling of relevant ions, including phosphate (PO4). The interfacial interactions of Ca and Mg (M2+) with PO4 have not been analyzed yet for freshly precipitated Fh. Here, we studied experimentally this interaction in binary M2+-PO4 systems over a wide range of pH, M2+/PO4 ratios, and ion loadings. The primary adsorption data were scaled to the surface area of Fh using a recent ion-probing methodology that accounts for the size-dependent chemical composition of this nanomaterial (FeO1.4(OH)0.2·nH2O). The results have been interpreted with the charge distribution (CD) model, combined with a state-of-the-art structural surface model for Fh. The CD coefficients have been derived independently using MO/DFT/B3LYP/6-31+G** optimized geometries. M2+ and PO4 mutually enhance their adsorption to Fh. This synergy results from the combined effect of ternary surface complex formation and increased electrostatic interactions. The type of ternary complex formed (anion- vs cation-bridged) depends on the relative binding affinities of the co-adsorbing ions. For our Ca-PO4 systems, modeling suggests the formation of two anion-bridged ternary complexes, i.e., ≡(FeO)2PO2Ca and ≡FeOPO3Ca. The latter is most prominently present, leading to a relative increase in the fraction of monodentate PO4 complexes. In Mg-PO4 systems, only the formation of the ternary ≡FeOPO3Mg complex has been resolved. In the absence of Ca, the pH dependency of PO4 adsorption is stronger for Fh than for goethite, but this difference is largely, although not entirely, compensated in the presence of Ca. This study enables the use of Fh as a proxy for the natural oxide fraction, which will contribute to improved understanding of the mutual interactions of PO4 and M2+ in natural systems. Universidad de Costa Rica/[]/UCR/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro de Investigaciones Agronómicas (CIA)

The receptor-binding domain (RBD) of the SARS-CoV-2 spike protein mediates viral entry into host cells through binding to the cell-surface receptor angiotensin-converting enzyme 2 (ACE2). It has been shown that SARS-CoV-2 RBD (RBDCoV2) has a higher binding affinity to human ACE2 than its highly homologous SARS-CoV RBD (RBDCoV), for which the mechanistic reasons still remain to be elucidated. Here, we used the multiple-replica molecular dynamics (MD) simulations, molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) binding free energy calculations, and interface residue contact network (IRCN) analysis approach to explore the mechanistic origin of different ACE2 binding affinities of these two RBDs. The results demonstrate that, when compared to the RBDCoV2-ACE2 complex, the RBDCoV-ACE2 complex features the enhanced overall structural fluctuations and inter-protein positional movements and increased conformational entropy and diversity. The inter-protein electrostatic attractive interactions are a dominant force in determining the high ACE2 affinities of both RBDs, while the significantly strengthened electrostatic forces of attraction of ACE2 to RBDCoV2 determine the higher ACE2 binding affinity of RBDCoV2 than of RBDCoV. Comprehensive comparative analyses of the residue binding free energy components and IRCNs reveal that, although any RBD residue substitution involved in the charge change can significantly impact the inter-protein electrostatic interaction strength, it is the substitutions at the RBD interface that lead to the overall stronger electrostatic attractive force of RBDCoV2-ACE2, which in turn not only tightens the interface packing and suppresses the dynamics of RBDCoV2-ACE2, but also enhances the ACE2 binding affinity of RBDCoV2 compared to that of RBDCoV. Since the RBD residue substitutions involving gain/loss of the positively/negatively charged residues, in particular those near/at the binding interfaces with the potential to form hydrogen bonds and/or salt bridges with ACE2, can greatly enhance the ACE2 binding affinity, the SARS-CoV-2 variants carrying such mutations should be paid special attention to.

Made available in DSpace on 2022-05-01T13:41:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-05-05 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Judicious design strategies should be considered powerful tools to better control the properties of chitosan (CS) and tripolyphosphate (TPP) particles. This study focused on understanding the role of the charge properties of 5-fluorouracil (5-FU) on the formation and properties of CS-TPP nanoparticles. The effect of synthesis variables of CS-TPP nanoparticles (CS to TPP ratio and order of addition) under pH 4.5 and 5.5 was evaluated, where CS and TPP were charged, and 5-FU had two different charges (positive and negative), maximizing the interactions between them for the formation of nanoparticles. The order of addition and drug location resulted in changes in the interaction forces, influencing the particle size and size distribution. 5-FU addition into CS resulted in stronger interactions, favoring the formation of smaller particles. The pH of reactional medium and CS to TPP ratio affected the properties of particles, in terms of size and potential zeta, which led to greater 5-FU entrapment. These results demonstrated that the particle properties still depends of the synthesis factors, but the physicochemical properties of drug also influence the reactions/interactions involved in the formation of CS-TPP nanoparticles. São Paulo State University (UNESP) School of Pharmaceutical Sciences Nanomedicine and Nanotoxicology Group (GNANO) University of São Paulo (USP) São Paulo State University (UNESP) School of Pharmaceutical Sciences FAPESP: 2014/50928-2 FAPESP: 2016/01464-9 CNPq: 465687/2014-8

Funding Information: This work was supported by the Academy of Finland through its Centres of Excellence Programme (2022–2029, LIBER) under project no. 346111 (M.S.) , Business Finland Co-Innovation grant No. 3767/31/ 2019 (M.S.) , the National Science Centre, Poland (grant no. 2018/31/D/ ST5/01866 ) (P.B. and M.M.), and the U.S. National Science Foundation , grant No. 1905732 (J.L.). We are grateful for the support by FinnCERES Materials Bioeconomy Ecosystem. Computational resources by CSC IT Centre for Finland, PLGrid Infrastructure (Poland), and RAMI – RawMatters Finland Infrastructure are also gratefully acknowledged. Publisher Copyright: © 2023 The Authors Streaming potential and quartz crystal microbalance measurements, combined with all-atom molecular dynamics simulations, were used to study the pH dependency of the adsorption of two basic homopolypeptides, poly-L-lysine (PLL) and poly-L-arginine (PARG), on α-quartz surface. We report that the observed adsorption behavior rises from an interplay of i) the change in the number of possible peptide-surface ion pairs between the charged moieties and ii) repulsive electrostatic interactions between the polypeptide molecules. For low pH values, polypeptide adsorption was strongest and stable monolayers were formed. However, electrostatic repulsion between the polypeptides led to a relatively low maximum surface coverage. On the other hand, higher pH led to more weakly bound, but significantly denser, peptide films with limited stability. Simulations indicate that electrostatic interactions are the main driving force for adsorption, while hydrogen bonding and non-specific interactions also contribute. Additionally, the important role of the counterions of the negatively charged quartz surface that form a positively charged ion adlayer is highlighted. Ion release of the condensed sodium ions at the charged surface occurs via displacement by polypeptide adsorption. The mechanisms revealed by this work provide systematic guidelines to engineering active surfaces of charged peptides with controlled surface coverage and reversible binding.

We compute ionic free energy adsorption profiles at aqueous graphene interface by developing a self-consistent approach. To do so, we design a microscopic model for water and put the liquid on an equal footing with the graphene described by its electronic band structure. By evaluating progressively the electronic/dipolar coupled electrostatic interactions, we show that the coupling level including mutual graphene/water screening permits to recover remarkably the precision of extensive quantum simulations. We further derive the potential of mean force evolution of several alkali cations.

The structural stability and solubility of proteins in liquid therapeutic formulations is important, especially since new generations of therapeutics are designed for efficacy before consideration of stability. We introduce an electrostatic binding model to measure the net charge of proteins with bound ions in solution. The electrostatic potential on a protein surface is used to separately group together acidic and basic amino acids into patches, which are then iteratively bound with oppositely charged counterions. This model is aimed toward formulation chemists for initial screening of a range of conditions prior to lab-work. Computed results compare well with experimental zeta potential measurements from the literature covering a range of solution conditions. Importantly, the binding model reproduces the charge reversal phenomenon that is observed with polyvalent ion binding to proteins and its dependence on ion charge and concentration. Intriguingly, protein sequence can be used to give similarly good agreement with experiment as protein structure, interpreted as resulting from the close proximity of charged sidechains on a protein surface. Further, application of the model to human proteins suggests that polyanion binding and over-charging, including charge reversal for cationic proteins, is a general feature. These results add to evidence that addition of polyanions to protein formulations could be a general mechanism for modulating solution stability.

Cell–material interactions play an essential role in the development of scaffold-based tissue engineering strategies. Cell therapies are still limited in treating injuries when severe damage causes irreversible loss of muscle cells. Electroactive biomaterials and, in particular, piezoelectric materials offer new opportunities for skeletal muscle tissue engineering since these materials have demonstrated suitable electroactive microenvironments for tissue development. In this study, the influence of the surface charge of piezoelectric poly(vinylidene fluoride) (PVDF) on cell adhesion was investigated. The cytoskeletal organization of C2C12 myoblast cells grown on different PVDF samples was studied by immunofluorescence staining, and the interactions between single live cells and PVDF were analyzed using an atomic force microscopy (AFM) technique termed single-cell force spectroscopy. It was demonstrated that C2C12 myoblast cells seeded on samples with net surface charge present a more elongated morphology, this effect being dependent on the surface charge but independent of the poling direction (negative or positive surface charge). It was further shown that the cell deadhesion forces of individual C2C12 cells were higher on PVDF samples with an overall negative surface charge (8.92 ± 0.45 nN) compared to those on nonpoled substrates (zero overall surface charge) (4.06 ± 0.20 nN). These findings explicitly demonstrate that the polarization/surface charge is an important parameter to determine cell fate as it affects C2C12 cell adhesion, which in turn will influence cell behavior, namely, cell proliferation and differentiation, Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019, UID/BIA/04050/2013, UID/BIO/04469, project POCI-01-0145-FEDER-028237 and under BioTecNorte operation (NORTE-01-0145-FEDER-000004). The authors also thank the FCT for the SFRH/BD/111478/2015 (S.R.) and SFRH/BPD/90870/2012 (C.R.) grants. Funds provided by FCT in the framework of EuroNanoMed 2016 call, Project LungChek ENMed/0049/2016 are also gratefully acknowledged. The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry and Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06)

To explore the mechanistic origin that determines the binding affinity of SARS-CoV-2 spike receptor binding domain (RBD) to human angiotensin converting enzyme 2 (ACE2), we constructed the homology models of RBD-ACE2 complexes of four Omicron subvariants (BA.1, BA.2, BA.3 and BA.4/5), and compared them with wild type complex (RBDWT-ACE2) in terms of various structural dynamic properties by molecular dynamics (MD) simulations and binding free energy (BFE) calculations. The results of MD simulations suggest that the RBDs of all the Omicron subvariants (RBDOMIs) feature increased global structural fluctuations when compared with RBDWT. Detailed comparison of BFE components reveals that the enhanced electrostatic attractive interactions are the main determinant of the higher ACE2-binding affinity of RBDOMIs than RBDWT, while the weakened electrostatic attractive interactions determine RBD of BA.4/5 subvariant (RBDBA.4/5) lowest ACE2-binding affinity among all Omicron subvariants. The per-residue BFE decompositions and the hydrogen bond (HB) networks analyses indicate that the enhanced electrostatic attractive interactions are mainly through gain/loss of the positively/negatively charged residues, and the formation or destruction of the interfacial HBs and salt bridges can also largely affect the ACE2-binding affinity of RBD. It is worth pointing out that since Q493R plays the most important positive contribution in enhancing binding affinity, the absence of this mutation in RBDBA.4/5 results in a significantly weaker binding affinity to ACE2 than other Omicron subvariants. Our results provide insight into the role of electrostatic interactions in determining of the binding affinity of SARS-CoV-2 RBD to human ACE2.

International audience; A bimetallic metal complex involving a fluorene linker between two redox active bis(cyclopentadienyl)molybdenum dithiolene moieties has been synthesized and characterized by electrochemistry and spectroelectrochemistry. Cyclic voltammetry experiments show sequential oxidation of the two redox centers with small ΔE values between the first and the second redox processes and between the third and the fourth ones. Comparative electrochemical studies carried out using either [NBu4][PF6] or the poorly coordinating supporting electrolyte [Na][B(C6H4(CF3)2)4] in dichloromethane indicate strong electrostatic effects on consecutive electron transfers, especially for highly charged species. Spectroelectrochemical investigations together with DFT calculations evidence that the two molybdenocene dithiolene electrophores are weakly electronically coupled through the organic bridge. © 2022 Elsevier Ltd

The thermodynamic phase behavior of charged polymers is a crucial property underlying their role in biology and various industrial applications. A complete understanding of the phase behaviors of such polymer solutions remains challenging due to the multi-component nature of the system and the delicate interplay among various factors, including the translational entropy of each component, excluded volume interactions, chain connectivity, electrostatic interactions, and other specific interactions. In this work, the phase behavior of partially charged, ion-containing polymers in polar solvents is studied by further developing a liquid-state (LS) theory with local short-range interactions. This work is based on the LS theory developed for fully-charged polyelectrolyte solutions. Specific interactions between charged groups of the polymer and counterions, between neutral segments of the polymer, and between charged segments of the polymer are incorporated into the LS theory by an extra Helmholtz free energy from the perturbed-chain statistical associating fluid theory (PC-SAFT). The influence of the sequence structure of the partially charged polymer is modeled by the number of connections between bonded segments. The effects of chain length, charge fraction, counterion valency, and specific short-range interactions are explored. A computational App for salt-free polymer solutions is developed and presented, which allows easy computation of the binodal curve and critical point by specifying values for the relevant model parameters.

Gold (Au) and palladium (Pd) are platinum group metals (PGMs) that are considered critical in society because they are required in several industrial applications. Their shortage has caused the urgent need for their recovery from secondary resources. Therefore, there is a need to develop functional materials with high adsorption capacity and selectivity for recovery of PGMs from various secondary sources. In this study, a Zn-Al-layered double hydroxide@zeolitic imidazolate framework-8 (Zn–Al–LDH@ZIF–8) nanocomposite was used as an adsorbent for the recovery of Au and Pd from ore concentrates. The Zn–Al–LDH@ZIF–8 nanocomposite was characterised using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, zeta potential, and X-ray diffraction (XRD) spectroscopy. The recovery of Au(III) and Pd(II) was achieved using ultrasound-assisted dispersive µ-solid-phase extraction (UA-D-µ-SPE) and their quantification was attained using an inductively coupled plasma mass spectrometer (ICP-MS). The results showed that the surface of the adsorbent remained positively charged in a wide pH range, which endowed the nanocomposite with high adsorption affinity towards Au(III) and Pd(II). Under optimised conditions, the equilibrium studies revealed that the adsorption of Au(III) and Pd(II) ions followed the Langmuir isotherm model with maximum sorption capacities of 163 mg g−1 and 177 mg g−1 for Au(III) and Pd(II), respectively. The nanocomposite possessed relatively good regeneration, reusability, and stability characteristics, with its performance decreasing by only 10% after five adsorption–desorption cycles.

openaire: EC/H2020/788489/EU//BioELCell The need for a precise regulation of the properties of chiral nematic structures in response to external stimuli is addressed. Self-assembled iridescent coatings are produced under the effect of electrostatic interactions between cellulose nanocrystals and poly(acrylic acid), endowing a high anisotropic dissymmetry (>0.3) and sensitivity to environmental humidity (13.1 nm/1% at 68-75% relative humidity, RH). The phenomena associated with shifts in selective light reflection (green to orange) and polarization, facilitate tunable transmitted colors (blue to orange) at given rotation angles (RA). Such properties are conveniently integrated into a "RH-RA-color" ternary code that is introduced as an anticounterfeiting technology, taking advantage of multicolor patterns that conveniently track with changes in RH and RA. The proposed charge-driven assembly opens new opportunities for chiral nematic materials that enable precise optical sensing and information encryption.

Significance We show the enhancement of ion transport properties for charged block copolymers comprising nonstoichiometric ionic liquids by stabilizing the cubic Frank–Kasper A15 phases. The ionic liquid cations predominantly present near the micellar interfaces to increase stabilization energies of the A15 structures if they have strong attractive electrostatic interactions with the charged polymer chains. Unprecedented reentrant phase transitions between lamellar and A15 structures occur through the electrostatic control of interfaces, resulting in radical changes in the conductivity by an order of magnitude. This study is one of the rare demonstrations of a low symmetry morphology to establish a prospective avenue for advanced polymer electrolytes having tailor-made interfaces. Our findings will have implications for energy storage and transfer devices., Recently, the interest in charged polymers has been rapidly growing due to their uses in energy storage and transfer devices. Yet, polymer electrolyte-based devices are not on the immediate horizon because of the low ionic conductivity. In the present study, we developed a methodology to enhance the ionic conductivity of charged block copolymers comprising ionic liquids through the electrostatic control of the interfacial layers. Unprecedented reentrant phase transitions between lamellar and A15 structures were seen, which cannot be explained by well-established thermodynamic factors. X-ray scattering experiments and molecular dynamics simulations revealed the formation of fascinating, thin ionic shell layers composed of ionic complexes. The ionic liquid cations of these complexes predominantly presented near the micellar interfaces if they had strong binding affinity with the charged polymer chains. Therefore, the interfacial properties and concentration fluctuations of the A15 structures were crucially dependent on the type of tethered acid groups in the polymers. Overall, the stabilization energies of the A15 structures were greater when enriched, attractive electrostatic interactions were present at the micellar interfaces. Contrary to the conventional wisdom that block copolymer interfaces act as “dead zone” to significantly deteriorate ion transport, this study establishes a prospective avenue for advanced polymer electrolyte having tailor-made interfaces.

Orientador: Miriam Dupas Hubinger Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos Resumo: A palmeira juçara ("Euterpe edulis" Martius) é uma espécie nativa da Mata Atlântica Brasileira e utilizada para extração de palmito. Além do palmito, pode-se também obter o fruto da juçara, semelhante ao açaí. Esse fruto apresenta coloração roxa quando maduro e alto conteúdo de antocianinas e polifenóis. Nesse contexto, para melhor aproveitar as propriedades funcionais e aumentar a estabilidade e biodisponibilidade desses compostos, objetivou-se com este trabalho obter extratos a partir da polpa do fruto da palmeira juçara e produzir partículas por dois métodos com princípios diferentes de encapsulação, spray drying e gelificação iônica. A obtenção dos extratos foi feita através de extrações hidroalcoólicas em leito de agitação, seguido do processo de concentração em evaporador rotativo a vácuo para remoção do etanol e aumento do conteúdo de sólidos totais. Os extratos concentrados foram submetidos à secagem por spray drying com uma temperatura de ar de entrada de 160 °C, utilizando maltodextrina com diferentes valores de dextrose equivalente (10, 20 e 30 DE) e goma Arábica como agentes carreadores. Os pós foram caracterizados em relação ao conteúdo de umidade, atividade de água, higroscopicidade, temperatura de transição vítrea, distribuição de tamanho e diâmetro médio de partículas, cor, retenção de antocianinas e compostos fenólicos, identificação e quantificação das antocianinas individuais, capacidade antioxidante, microestrutura através da microscopia eletrônica de varredura e confocal de varredura a laser. O processo de secagem por spray drying permitiu a estabilização dos compostos presentes no extrato de juçara na forma de micropartículas, apresentando alta retenção de antocianinas (superior a 88%) e compostos fenólicos com destaque para a capacidade antioxidante. O processo de gelificação iônica foi realizado através do gotejamento do alginato de sódio em solução de cloreto de cálcio e a inclusão do extrato de juçara ocorreu por absorção, através da estrutura porosa das partículas de gel. As amostras foram submetidas ao processo de recobrimento com quitosana, concentrado proteico de soro de leite e gelatina e foram analisadas em relação ao conteúdo de umidade, diâmetro médio e distribuição de tamanho, compressão uniaxial, conteúdo de antocianinas e capacidade antioxidante, estabilidade, liberação em condições gástrica e intestinal simuladas e microestrutura através da microscopia ótica, confocal de varredura a laser e eletrônica de varredura. O processo de gelificação iônica permitiu a formação de partículas em gel carreadoras de antocianinas, possibilitando desta forma, a liberação dos compostos bioativos em meios de pH específicos, como meio intestinal. A inclusão de antocianinas extraídas da polpa de juçara em partículas produzidas por spray drying e gelificação iônica permitiu manter a estabilidade das antocianinas em diferentes matrizes poliméricas, na forma de pó ou em gel Abstract: Jussara palm ("Euterpe edulis" Martius) is a native species of the Brazilian Atlantic Forest that produces an edible palm heart. Apart from its palm heart, it also yields the jussara fruit, similar to the açaí fruit. Jussara fruit, when ripe, presents a purple pulp and a high content of anthocyanins and polyphenols. In order to take advantage of the functional properties and to increase the stability of these compounds, this study aimed to obtain extracts from jussara pulp and to produce particles by two different encapsulation methods, spray drying and ionic gelation. The jussara extracts were produced by hydroalcoholic extractions in an agitated bed and, later, in order to remove ethanol and to increase total solids content, they were concentrated in a rotary vacuum evaporator. The concentrated extracts were dried by spray drying process with an inlet air temperature of 160 °C, using maltodextrin with different dextrose equivalent values (10, 20 and 30 DE) and gum Arabic as carrier agents. Microparticles were characterized in relation to moisture content, water activity, hygroscopicity, glass transition temperature, particle size distribution, color, retention of anthocyanins and phenolic compounds, identification and quantification of individual anthocyanins, antioxidant capacity, microstructure by scanning electron microscope and confocal laser scanning microscope. The bioactive compounds from jussara extract were stabilized by spray drying process, in the form of microparticles, and showed high anthocyanins (above 88%) and phenolic retention values and high antioxidant capacity. The ionic gelation process consisted in dripping the sodium alginate in a calcium chloride solution with the inclusion of the jussara extract occurring by absorption through the porous structure of the alginate hydrogel beads. The beads were subjected to a coating process using chitosan, whey protein concentrate and gelatin and were analyzed in relation to moisture content, particle size distribution, uniaxial compression, anthocyanin content and antioxidant capacity, stability, release in simulated gastric and intestinal conditions and microstructure by scanning electron microscope and confocal laser scanning microscope. Ionic gelation process led to the formation of hydrogel beads containing anthocyanins from jussara extract, thus enabling the release profile of the compounds at specific pH conditions, as intestinal fluid. The inclusion of anthocyanins from jussara extract in particles produced by spray drying and ionic gelation maintained the stability of bioactive compounds in different polymer matrices, in the form of powder or hydrogel Doutorado Engenharia de Alimentos Doutora em Engenharia de Alimentos CNPQ 140280/2013-8 CAPES FAPESP

Flocculation could offer a low-cost and straightforward solution to harvest microalgae in an economic and energy-efficient way. Cationically modified cellulose nanocrystals (CNCs) have been propose...

The robustness of reverse osmosis (RO) against polar organic micropollutants (MPs) was investigated in pilot-scale drinking water treatment. Experiments were carried in hypoxic conditions to treat a raw anaerobic riverbank filtrate spiked with a mixture of thirty model compounds. The chemicals were selected from scientific literature data based on their relevance for the quality of freshwater systems, RO permeate and drinking water. MPs passage and the influence of permeate flux were evaluated with a typical low-pressure RO membrane and quantified by liquid chromatography coupled to high-resolution mass spectrometry. A strong inverse correlation between size and passage of neutral hydrophilic compounds was observed. This correlation was weaker for moderately hydrophobic MPs. Anionic MPs displayed nearly no passage due to electrostatic repulsion with the negatively charged membrane surface, whereas breakthrough of small cationic MPs could be observed. The passage figures observed for the investigated set of MPs ranged from less than 1%–25%. Statistical analysis was performed to evaluate the relationship between physicochemical properties and passage. The effects of permeate flux were more pronounced for small neutral MPs, which displayed a higher passage after a pressure drop.

Seeking adsorbents with high adsorption capacity and ease of regeneration is imperative for environmental remediation. Herein, strongly negatively charged two-dimensional (2D) ultrathin InVO4 nanoribbons (NRs) were synthesized. The material exhibited impressive selective adsorption capabilities towards cationic dyes, and the fitted Langmuir maximum adsorption capacity is 789.7 mg/g when using RhB as a model signal pollutant. The adsorption curve towards Rhodamine B (RhB) fits well with the pseudo-second-order (PSO) reaction. The corresponding adsorption isotherm is confirmed in accordance with the Freundlich model, indicating the adsorption is likely a multi-layer adsorption process. Through examining its adsorption activities with positively charged upconversion nanoparticles (UCNPs) and dyes with different surface charges, the strong electrostatic attraction is found to be the predominant adsorption mechanism. Furthermore, the new adsorbents showed remarkable resilience to even large pH variation (from 3 to 12), and could be rapidly and efficiently regenerated using a mixture of water and ethanol (volume ratio 1:1) in 30 min. These advantages are highly favorable for the application of efficient adsorbents for wastewater treatment and resource recovery. Nanyang Technological University This paper was supported by funding from NEWRI (04-OI-S-00140-N025 OOE01).

International audience; Adsorption behaviours of humic acid on three natural clays from Ivory Coast were studied. In order to investigate the adsorption mechanism, characterization of clays and the humic acid–clay complex was conducted by using various analytical methods (attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), specific surface area analysis (BET) and chemical composition). As a result, adsorption process showed that the maximum adsorption capacity of humic acid was achieved at pH = 3 and was found to be to 115 mg/g obtained for the best sample. For all clays, the adsorption was found to be strongly dependent on pH and well fitted by the Langmuir model. In addition, it was shown that the adsorption capacity was linked to the kaolinite content of each sample. The results showed that humic acid adsorption onto clay was made via electrostatic interactions, ligand exchange and hydrophobic interactions. This study showed that clays are valuable adsorbents for the removal of humic acid.

Intrinsically disordered proteins (IDPs) are an abundant class of proteins and protein regions which rapidly change between multiple structures without an equilibrium position. IDPs exist as a series of conformational ensembles of semi-stable conformations that can be adopted based on a hilly landscape of shallow free energy minima. Disordered sequences share characteristic features differentiating them from globular proteins, including low sequence complexity, low occurrence of hydrophobic residues, high polar and charged residue content, and high flexibility. IDPs are commonly involved in regulation in the cell, and frequently function as, or interact with, hub proteins in protein-protein interaction networks, making them an important class of macromolecules for understanding regulatory and other processes. Given their functional importance, these proteins are widely studied. Many analytical techniques are used, though rapid conformational sampling by IDPs makes it difficult to detect many states with NMR or other techniques. Computational approaches such as molecular dynamics are increasingly used to probe the binding and conformational sampling of these proteins, allowing for observation of factors that cannot be observed with traditional analytical methods such as NMR, such as differing conformational ensembles and the dipoles of individual residues. Here, we studied the role of electrostatic interactions in IDP protein-protein interaction using molecular dynamics simulations performed with the Drude-2019 force field (FF), a polarizable model that allows for more accurate representation of electrostatics, an important factor for highly charged systems like IDPs. For this project, a prototypical protein with disordered regions, p53, was simulated with two protein partners, the nuclear coactivator domain of the CREB binding protein (CBP), and the E3 ubiquitin-protein ligase mouse double minute 2 (MDM2). p53 is widely studied, and the p53 transactivation domain (TAD) is disordered and binds to many structurally diverse partners, making this protein domain a useful model for probing the role of electrostatic interactions formed by IDPs at protein-protein binding interfaces. We found that the Drude-2019 FF allows for simulation of the p53 TAD with Cα chemical shifts comparable to those observed with NMR, supporting that the Drude-2019 FF performs well in simulating IDPs. We observed large relative change in sidechain dipole moments when comparing the p53 TAD alone and when bound to either CBP or MDM2. We observed that aliphatic and aromatic amino acids experienced the largest relative change in sidechain dipole moments, and that there is sensitivity to binding shown in this dipole response. The largest percent changes in sidechain dipole moment were found to localize at and around the binding interface. Understanding the binding interactions of IDPs at a fundamental level, including the role of electrostatic interactions, may help with targeting IDPs or their partners for drug design. Master of Science in Life Sciences Many proteins adopt one main structure, and these proteins are called ordered proteins. Intrinsically disordered proteins (IDPs) are an abundant category of proteins which adopt multiple structures, and transition between these different structures is based on factors such as the environment around them, modifications, or interactions with other macromolecules. The flexible structures of IDPs allow them to bind to multiple different partners and to regulate processes in the cell. Since IDPs often regulate processes important to cell function, when these proteins are mutated, misfolded, or otherwise mis-regulated the resulting issues are associated with disease states. IDPs are widely studied with analytical techniques, but because IDPs frequently change shape it can be difficult to observe certain behaviors or certain factors with these techniques. Computational approaches, such as molecular dynamics (MD). MD is the study of molecular motion and interaction, and can allow observation of factors that would be difficult or impossible to observe otherwise, such as the varying structures of IDPs or the dipole moments of specific amino acids within the proteins. For this project we wanted to probe the role of dipole moments, which are charge-based interactions, in the binding of IDPs to protein partners, to better understand how IDPs bind to different partners. We used the p53 protein as an example of IDP binding and simulated it alone and bound to two other proteins, the CREB binding protein (CBP), and the E3 ubiquitin-protein ligase mouse double minute 2 (MDM2). We observed that our simulations were comparable to experiments done with nuclear magnetic resonance spectroscopy, which served to validate that our simulations were realistic. We observed that the dipole moments of the proteins change when simulating the proteins alone and in complex, and that the largest relative changes in dipole are observed for regions of the proteins involved in binding. Probing the role of charge-based interactions in protein-protein binding interactions for IDPs can help us to greater understand these interactions at a more fundamental level and could help with targeting IDPs or their partners for drug design or other problems.

Orientador: Cesar José Bonjuani Pagan Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação Resumo: Nesta dissertação propomos a análise de uma idealização estabelecida dentro da teoria eletromagnética. A partir de Um Tratado sobre Eletricidade e Magnetismo, James C. Maxwell expõe alguns conceitos físicos relativos ao aterramento elétrico em condutores. Assim, ele estima que a presença de um fio condutor que estabelece a conexão entre um corpo condutor e outro, ou mesmo ao terra elétrico, perturba as características do sistema envolvido (carga, potencial e campo elétrico). Desse modo, Maxwell preconiza que para sistemas teóricos ou idealizados, quão indefinidamente fino seja o fio, indefinidamente menor será a perturbação gerada. A contextualização de uma idealização física dentro do ensino da teoria eletromagnética, especialmente para um curso de engenharia, é necessária no intuito de enfatizar as diferenças entre modelos reais e teóricos, uma vez também que os estudantes destes cursos devem estar interessados no desenvolvimento prático dos conceitos apreendidos em sala de aula. Nesse sentido, quando tratamos do método das imagens, especificamente para o problema de uma carga na presença de um condutor esférico aterrado, temos a oportunidade de explorar os limites de um modelo teórico, delimitando quais nuances podem aproximá-lo de uma aplicação no mundo real. Em vista disso, notamos que a maioria dos livros didáticos usados no ensino do eletromagnetismo, quando lidam com o problema do aterramento da esfera, simplesmente negligenciam a questão suscitada por Maxwell, de modo a transformar o problema em um exercício puramente matemático, sem necessidade de explicar os fundamentos físicos que sustentam a solução do problema. Portanto, o intuito do presente trabalho é desenvolver um modelo cuja solução defina o comportamento físico para ambos os casos (levando em consideração ou não a existência da conexão da esfera com o terra elétrico), bem como verificar os limites deste modelo teórico Abstract: In this work, we propose the analysis about an idealized established within electromagnetic theory. From A Treatise on Electricity and Magnetism, James C. Maxwell presents some physical concepts related to electrical conductors grounded. In this direction, he estimates that the presence of a straight metallic wire which establishes the connection between a conducting body and another, or even to electrical ground, disturbs the properties of the system involved (charge, potential and electric field). Thus, Maxwell preconize for theoretical or idealized systems, how indefinitely thin is the wire, indefinitely lower is the disturbance created. The context of a physical idealization into the teaching of electromagnetic theory, especially for an engineering degree is required in order to emphasize the differences between real and theoretical models, since the students of these courses should be also interested in the practical development of the concepts learned in the classroom. In this sense, when we discussed the method of images, specifically to the problem of a charge point charge in the presence of a grounded conducting sphere, we have the opportunity to explore the limits of a theoretical model, outlining which nuances can approach it to a real world application. In view of this, we note that most of the textbooks used in teaching electromagnetism, when deals with the problem of grounded sphere, they simply neglect the issue raised by Maxwell. In order to transform the problem into a purely mathematical exercise, without to explain the physical foundations that support the solution of the problem. Therefore, the aim of this work is to develop a model whose solution defines the physical behavior for both cases (taking into account or not the existence of a connection of the sphere with the electrical ground), and to verify the limits of this theoretical model Mestrado Eletrônica, Microeletrônica e Optoeletrônica Mestre em Engenharia Elétrica

Orientadores: Rosiane Lopes da Cunha, Ângelo Luiz Fazani Cavallieri Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos Resumo: As proteínas do soro do leite (WPI) e lecitina de soja são amplamente utilizadas em alimentos devido às suas excelentes propriedades emulsificantes. Este trabalho visou avaliar as propriedades emulsificantes da mistura de WPI e lecitina em diferentes condições de pH e concentração dos ingredientes. A primeira etapa consistiu no estudo das interações entre os emulsificantes em meio aquoso em diferentes razões WPI:lecitina e condições de pH. Os resultados mostraram que na razão 1:1 e em pH abaixo do pI da proteína, no qual os emulsificantes encontravam-se opostamente carregados, foi favorecida a formação de complexos eletrostáticos. Na segunda etapa, emulsões O/A contendo proteínas do soro e/ou lecitina foram avaliadas através da estabilidade à cremeação, microestrutura, distribuição do tamanho de gota, densidade de carga superficial, reologia, eletroforese em gel de poliacrilamida e digestão in vitro, verificando-se a influência do pH e da pressão de homogeneização. As emulsões estabilizadas somente por proteínas apresentaram separação de fases e comportamento não-Newtoniano somente em pH próximo ao pI. As emulsões contendo somente lecitina não separaram de fases e apresentaram comportamento Newtoniano. Os sistemas em pH abaixo do pI, contendo a mistura de emulsificantes apresentaram elevada instabilidade cinética devido à forte interação eletrostática entre os componentes. No entanto, em pH próximo ao pI da prote, a interação foi favorável e levou ao aumento da estabilidade das emulsões e a menores tamanhos de gota, resultando em fluidos pouco viscosos. O aumento da pressão de homogeneização, em emulsões com pH próximo e acima do pI favoreceu a formação de agregados de alta massa molecular, o que não foi observado em pH mais ácido. Também não foi notada a formação de agregados na presença de lecitina em nenhuma das condições de pH. Os ensaios de eletroforese deram indícios de que a interação entre os emulsificantes levou a modificações na estrutura das proteínas e revelaram maior afinidade da lecitina com a ?-lactoalbumina (?-la). Finalmente, na etapa de simulação do processo de digestão as proteínas mostraram-se mais resistentes, uma vez que a presença de lecitina promoveu a liberação do óleo da emulsão logo no início da etapa gástrica. De maneira geral, a utilização das proteínas do soro juntamente com a lecitina como emulsificante levou a resultados satisfatórios pois permitiu o desenvolvimento de sistemas estáveis à cremeação em diferentes valores de pH, inclusive em pH próximo ao pI, e consideravelmente resistentes às condições adversas do trato gastrointestinal Abstract: Whey proteins (WPI) and soybean lecithin are widely used in food due to its excellent emulsifying properties. This study aimed to evaluate the emulsifying properties of the mixture of whey protein and lecithin at different conditions of pH and concentration of ingredients. Firstly, the interactions between emulsifiers in an aqueous medium at different ratios (WPI:lecithin) and pH conditions were studied. The results showed that at mixing ratio of 1:1 and at pH below the isoelectric point of the protein (pI) in which the emulsifiers were oppositely charged, was favored the formation of electrostatic complexes. Afterwards, O/W emulsions containing WPI and/or lecithin were prepared and the influence of pH and pressure homogenization were studied. Stability, microstructure, droplet size distribution, surface charge density, rheology, electrophoresis in polyacrylamide gel (SDS-PAGE) and digestion in vitro were evaluated. The emulsions stabilized by proteins showed phase separation and non-Newtonian behavior only in pH close to the pI. The emulsions containing only lecithin were stable and showed Newtonian behavior. Systems containing the mixture of emulsifiers at pH below the pI showed high kinetic instability due to the strong electrostatic interactions between the components. However, at pH close to the pI the interaction was favorable and led to an increase of the emulsion stability and to smaller droplet sizes, resulting in lower viscosities. When the pressure homogenization was increased, emulsions at a pH close to and above the pI favored the formation of high molecular weight protein aggregates which was not observed in emulsions at lower pH. In the presence of lecithin, protein aggregates were not formed in any of the pH conditions. The SDS-PAGE analysis showed that the interaction between emulsifiers led to modifications in the structure of proteins and indicated a higher affinity of lecithin to ?-lactalbumin (?-la). Finally, proteins were more resistant to digestion, since the presence of lecithin promoted release of oil emulsion at the beginning of gastric step. In general, the use of whey protein with lecithin as emulsifier led to satisfactory results because it allowed the development of stable emulsions to creaming at different pH values, even at pH close to the pI, and substantially resistant to the adverse conditions of the gastrointestinal tract Mestrado Engenharia de Alimentos Mestre em Engenharia de Alimentos

A range of isoxazole‐containing amino acids was synthesized that displaced acetyl‐lysine‐containing peptides from the BAZ2A, BRD4(1), and BRD9 bromodomains. Three of these amino acids were incorporated into a histone H4‐mimicking peptide and their affinity for BRD4(1) was assessed. Affinities of the isoxazole‐containing peptides are comparable to those of a hyperacetylated histone H4‐mimicking cognate peptide, and demonstrated a dependence on the position at which the unnatural residue was incorporated. An isoxazole‐based alkylating agent was developed to selectively alkylate cysteine residues in situ. Selective monoalkylation of a histone H4‐mimicking peptide, containing a lysine to cysteine residue substitution (K12C), resulted in acetyl‐lysine mimic incorporation, with high affinity for the BRD4 bromodomain. The same technology was used to alkylate a K18C mutant of histone H3.

In the last years, intense efforts have been made in order to obtain colloidal-based systems capable of pointing out the presence of melamine in food samples. In this work, we reported about the recognition of melamine in aqueous solution, using gold nanoparticles stabilized with 3-mercapto-1-propanesulfonate (AuNPs-3MPS), with the aim of deepening how the recognition process works. AuNPs were synthesized using a wet chemical reduction method. The synthesized AuNPs-3MPS probe was fully characterized, before and after the recognition process, by both physicochemical (UV–vis, FT-IR, 1H-NMR, DLS and ζ-potential) and morphostructural techniques (AFM, HR-TEM). The chemical and electronic structure was also investigated by SR-XPS. The sensing method is based on the melamine-induced aggregation of AuNPs; the presence of melamine was successfully detected in the range of 2.5−500 ppm. The results achieved also demonstrate that negatively charged AuNPs-3MPS are potentially useful for determining melamine contents in aqueous solution. SR-XPS measurements allowed to understand interaction mechanism between the probe and the analyte. The presence of sulfonate groups allows a mutual interaction mediated by electrostatic bonds between nanoparticles surface thiols and positively charged amino groups of melamine molecules.

Significance Living systems require ions in cellular fluids. These ions electrostatically interact with biological macromolecules and influence their functions. Some ions are attracted to charged protein surfaces, whereas other ions are excluded. Because ion–protein interactions are generally weak and ions dynamically change their locations with respect to proteins, investigations of ion–protein interactions are challenging. It is not well understood how ions behave around proteins and affect their properties. In this work, using unique spectroscopic approaches, we quantified and visualized the weak anion–protein interactions. New knowledge about weak ion–protein interactions may lead to new strategies for protein engineering and drug development., The molecular properties of proteins are influenced by various ions present in the same solution. While site-specific strong interactions between multivalent metal ions and proteins are well characterized, the behavior of other ions that are only weakly interacting with proteins remains elusive. In the current study, using NMR spectroscopy, we have investigated anion–protein interactions for three proteins that are similar in size but differ in overall charge. Using a unique NMR-based approach, we quantified anions accumulated around the proteins. The determined numbers of anions that are electrostatically attracted to the charged proteins were notably smaller than the overall charge valences and were consistent with predictions from the Poisson–Boltzmann theory. This NMR-based approach also allowed us to measure ionic diffusion and characterize the anions interacting with the positively charged proteins. Our data show that these anions rapidly diffuse while bound to the proteins. Using the same experimental approach, we observed the release of the anions from the protein surface upon the formation of the Antp homeodomain–DNA complex. Using paramagnetic relaxation enhancement (PRE), we visualized the spatial distribution of anions around the free proteins and the Antp homeodomain–DNA complex. The obtained PRE data revealed the localization of anions in the vicinity of the highly positively charged regions of the free Antp homeodomain and provided further evidence of the release of anions from the protein surface upon the protein–DNA association. This study sheds light on the dynamic behavior of anions that electrostatically interact with proteins.

This study examines the mechanisms of adsorption of anthocyanins from model aqueous solutions at pH values of 3, 6, and 9 by ion-exchange resins making the main component of heterogeneous ion-exchange membranes. This is the first report demonstrating that the pH of the internal solution of a KU-2-8 aromatic cation-exchange resin is 2-3 units lower than the pH of the external bathing anthocyanin-containing solution, and the pH of the internal solution of some anion-exchange resins with an aromatic (AV-17-8, AV-17-2P) or aliphatic (EDE-10P) matrix is 2&ndash, 4 units higher than the pH of the external solution. This pH shift is caused by the Donnan exclusion of hydroxyl ions (in the KU-2-8 resin) or protons (in the AV-17-8, AV-17-2P, and EDE-10P resins). The most significant pH shift is observed for the EDE-10P resin, which has the highest ion-exchange capacity causing the highest Donnan exclusion. Due to the pH shift, the electric charge of anthocyanin inside an ion-exchange resin differs from its charge in the external solution. At pH 6, the external solution contains uncharged anthocyanin molecules. However, in the AV-17-8 and AV-17-2P resins, the anthocyanins are present as singly charged anions, while in the EDE-10P resin, they are in the form of doubly charged anions. Due to the electrostatic interactions of these anions with the positively charged fixed groups of anion-exchange resins, the adsorption capacities of AV-17-8, AV-17-2P, and EDE-10P were higher than expected. It was established that the electrostatic interactions of anthocyanins with the charged fixed groups increase the adsorption capacity of the aromatic resin by a factor of 1.8&ndash, 2.5 compared to the adsorption caused by the &pi, &ndash, &pi, (stacking) interactions. These results provide new insights into the fouling mechanism of ion-exchange materials by polyphenols, they can help develop strategies for membrane cleaning and for extracting anthocyanins from juices and wine using ion-exchange resins and membranes.

The dielectric nature of polar liquids underpins much of their ability to act as useful solvents, but its description is complicated by the long-ranged nature of dipolar interactions. This is particularly pronounced under the periodic boundary conditions commonly used in molecular simulations. In this article, the dielectric properties of a water model whose intermolecular electrostatic interactions are entirely short-ranged are investigated. This is done within the framework of local molecular-field theory (LMFT), which provides a well-controlled mean-field treatment of long-ranged electrostatics. This short-ranged model gives a remarkably good performance on a number of counts, and its apparent shortcomings are readily accounted for. These results not only lend support to LMFT as an approach for understanding solvation behavior, but also are relevant to those developing interaction potentials based on local descriptions of liquid structure., Royal Commission for the Exhibition of 1851

We investigate the electrostatic interactions of zwitterionic membranes immersed in mixed electrolytes composed of mono- and multivalent ions. We show that the presence of monovalent salt is a necessary condition for the existence of a finite electrostatic force on the membrane. As a result, the mean-field membrane pressure originating from the surface dipoles exhibits a non-uniform salt dependence, characterized by an enhancement for dilute salt conditions and a decrease at intermediate salt concentrations. Upon addition of multivalent cations to the submolar salt solution, the separate interactions of these cations with the opposite charges of the surface dipoles makes the intermembrane pressure more repulsive at low membrane separation distances and strongly attractive at intermediate distances, resulting in a discontinuous like-charge binding transition followed by the membrane binding transition. By extending our formalism to account for correlation corrections associated with large salt concentrations, we show that membranes of high surface dipole density immersed in molar salt solutions may undergo a membrane binding transition even without the multivalent cations. Hence, the tuning of the surface polarization forces by membrane engineering can be an efficient way to adjust the equilibrium configuration of dipolar membranes in concentrated salt solutions.

Five new phosphinato derivatives, adducts and complexes have been synthesized and characterized by infrared and Mössbauer spectroscopies. Based on their spectroscopic data discrete or infinite chain structures are proposed, the phosphinate ion behaving as a bicoordinating bridging or a monocoordinating ligand, the environments around the tin (IV) centers being octahedral or trigonal bipyramidal. In Me4N(SnPh2)2(H2PO2)2Cl3 and Cl2Sn(H2PO2)2NMe4H2PO2, the cation is involved in electrostatic interactions with the anions.

Orientador: Rosiane Lopes da Cunha Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos Resumo: A formação de nanopartículas para sistemas de encapsulamento pode ser realizada por vários processos e, entre eles, pode-se citar os processos espontâneos, que são simples e produzidos com baixo consumo de energia. Dentre esses processos encontra-se a complexação eletrostática que ocorre entre pelo menos dois polímeros com cargas opostas que interagem através de forças intermoleculares. A quitosana é um polissacarídeo carregado positivamente que apresenta propriedades mucoadesivas, porém apresenta baixa solubilidade em água. Nesse sentido, a hidrólise enzimática deste composto surge como uma alternativa para garantir maior homogeneidade e solubilidade na formação dos complexos. A gelana é um polissacarídeo aniônico solúvel em água e resistente a baixos valores de pH, o que facilita sua utilização como material encapsulante. Nesse contexto, este estudo teve como objetivo avaliar a formação de nanopartículas através da produção de complexos eletrostáticos utilizando a gelana (G) em combinação com a quitosana (C) ou a quitosana hidrolisada (HC), obtida a partir de hidrólise enzimática. Dois diferentes métodos foram utilizados para a produção das nanopartículas e comparados, "bulk" e microfluídica, sendo estas partículas incorporadas de cafeína em diferentes condições de processo. As nanopartículas foram caracterizadas quanto às seguintes análises: potencial zeta, distribuição de tamanho, índice de polidispersão (PDI), MEV-T (microscopia eletrônica de varredura no modo de transmissão), cristalinidade, turbidez, FTIR (espectroscopia de infravermelho por transformada de Fourier) e eficiência de encapsulação da cafeína. De modo geral, a hidrólise da quitosana permitiu a formação de estruturas menores e mais solúveis, o que facilitou a formação dos complexos. Além disso, partículas com maior concentração de gelana (razões G:C ou G:HC de 7:3 e 8:2) foram as que mostraram menor potencial zeta, tamanho de partícula e polidispersão. Dentre os processos utilizados, a microfluídica permitiu obter complexos com menor polidispersão (PDI ~0.1) e tamanho médio (~200 nm). No entanto, ambos os métodos de formação dos complexos permitiram o encapsulamento da cafeína, porém a microfluídica foi mais eficaz mostrando eficiência de encapsulação de aproximadamente 70%. Sendo assim, os resultados obtidos permitem afirmar que a microfluídica é uma técnica mais eficiente para a formação de nanocomplexos incorporados de cafeína quando comparada a processos tradicionais Abstract: The formation of nanoparticles for encapsulating systems can be carried out by various processes and, among them, there are spontaneous processes which are simple and produced with low energy consumption. Among these processes is the electrostatic complexation that occurs between at least two oppositely charged polymers interacting by intermolecular forces. Chitosan is a positively charged polysaccharide that shows mucoadhesive properties, but has low water solubility. In this sense, the enzymatic hydrolysis of this compound emerges as an alternative to ensure greater homogeneity and solubility in the complex formation. Gellan is a water-soluble anionic polysaccharide resistant to low pH values, which facilitates its use as an encapsulating material. In this context, this study aimed to evaluate the formation of nanoparticles by the production of electrostatic complexes using gellan (G) in combination with chitosan (C) or hydrolyzed chitosan, obtained from enzymatic hydrolysis. Two different methods were used for the production of nanoparticles and compared, bulk and microfluidic, and different process conditions were used to incorporate caffein in these particles. The nanoparticles were characterized according to the following analyzes: zeta potential, size distribution, polydispersity index (PDI), STEM (scanning transmission electron microscopy), crystallinity, turbidity, Fourier transform infrared spectroscopy (FTIR) and encapsulation efficiency. In general, the hydrolysis of chitosan allowed the formation of smaller and more soluble structures, which facilitated the formation of complexes. In addition, the particles with a higher gellan concentration (ratios G: C or G:HC of 7: 3 and 8: 2) showed the lowest zeta potential, particle size and polydispersity. Among the processes used, microfluidics allowed to obtain complexes with less polydispersity (PDI ~ 0.1) and lower mean size (~ 200 nm). However, both methods of complex formation allowed caffeine encapsulation, but microfluidics showed higher encapsulation efficiency (~ 70%). Thus, our results showed that microfluidics is a more efficient technique for the formation of nanocomplexes incorporated with caffeine as compared to traditional processes Mestrado Engenharia de Alimentos Mestra em Engenharia de Alimentos CAPES 88882.329560/2019-01

International audience; Many key industrial processes, from electricity production, conversion, and storage to electrocatalysis or electrochemistry in general, rely on physical mechanisms occurring at the interface between a metallic electrode and an electrolyte solution, summarized by the concept of an electric double layer, with the accumulation/depletion of electrons on the metal side and of ions on the liquid side. While electrostatic interactions play an essential role in the structure, thermodynamics, dynamics, and reactivity of electrode-electrolyte interfaces, these properties also crucially depend on the nature of the ions and solvent, as well as that of the metal itself. Such interfaces pose many challenges for modeling because they are a place where quantum chemistry meets statistical physics. In the present review, we explore the recent advances in the description and understanding of electrode-electrolyte interfaces with classical molecular simulations, with a focus on planar interfaces and solvent-based liquids, from pure solvent to water-in-salt electrolytes.

Construction of colloidal nanoparticles (NPs) into advanced functional nanocomposites and hybrids with the predesigned hierarchical structure and high-performance is attractive, especially for natural biological nanomaterials, such as proteins and polysaccharides. Herein, a simple and sustainable approach called interfacial NP complexation (INC) was applied to construct diverse functional (conductive, drug-loaded, or antimicrobial) nanocomposite filaments from oppositely charged colloidal nanocelluloses. By incorporating different additives during the INC process, including multiwalled carbon nanotube, an antitumor drug (doxorubicin hydrochloride), and metal (silver) NPs (Ag NPs), high-performance functional continuous filaments were synthesized, and their potential applications in electronics, drug delivery, and antimicrobial materials were investigated, respectively. This novel INC method based on charged colloidal NPs opens new avenues for building various functional filaments for a diversity of end uses.

Demand for products containing natural compounds has grown in recent decades and synthetic emulsifiers probably will be replaced. Lecithin is a natural emulsifier, but it has low emulsifying capacity for stabilizing oil-in water emulsions and does not show antimicrobial property. Thus, we proposed the development of surfactant-polyelectrolyte complexes (SPECs) based on lecithin (Lip) and chitosan (Chi) in order to provide antimicrobial properties and to enhance the emulsifying properties of lecithin. The physicochemical properties of SPECs were depending on the mass ratios between compounds. SPECs showed sizes ranging from 1.5 to 5.5 microns and Zeta potential values ranging from −49.5 mV to +38.5 mV. All SPECs showed surfactant properties reducing superficial tension and interfacial tension with sunflower oil. SPECs with positive Zeta potentials values and at concentration of 2.5 mg/mL were able to inhibit the Escherichia coli growth. Through droplet size measurements, may be observed that emulsions prepared with SPECs showed coalescence decreasing when compared with those prepared only with lecithin or chitosan. These results showed that SPECs can be modulated in their physicochemical properties to be potential emulsifiers with antimicrobial properties.

International audience; The multi-configurational ansatz of valence-bond theory may serve as basis for calculating in-termolecular interaction energies in a non-orthogonal basis. We look in the present contribution at the possibility to obtain the 1st-order electrostatic interactions from breathing-orbital valence-bond densities, and the 2nd-order dispersion energy from dipole-dipole interactions. The discussion is based on numerical results for the interaction of two N 2 O molecules.

The effect of cationic (n-cetyltrimethylammonium bromide - CTAB) and non-ionic (n-octanol) surface-active substances (SAS) on the kinetics of rising bubble attachment to a quartz surface and flotation recovery of quartz particles was investigated. The measured time of the three-phase contact (TPC) formation (tTPC) and the advancing contact angle (sessile drop) values, in pure and mixed CTAB and n-octanol solutions, allowed to evaluate the importance of electrostatic interactions and solid surface hydrophobicity in stability and rupture of the wetting films formed between a quartz surface and a colliding bubble. It was shown that electrostatic interactions inside the wetting film as well as the quartz hydrophobicity was changing with the composition of the mixed solutions. The experiments revealed that, within the concentration range of the SAS used in this study, CTAB modified properties of liquid/gas and liquid/solid interfaces, while non-ionic n-octanol adsorbed primarily at liquid/gas interface hindering its fluidity and, as a result, decreased bubble bouncing time. The correlation between the times of bubble attachment and the flotation recovery of quartz particles was established. © 2017 Elsevier B.V., Firat University Scientific Research Projects Management Unit: BAP 2015-28, BAP 2015-70 Narodowym Centrum Nauki: 2013/09/D/ST4/03785 Politechnika Wroclawska University of South Australia National Research Centre, J. Z. thanks National Research Centre (NCN grant No. 2013/09/D/ST4/03785) for partial financial support. C. K. and O. S. express their gratitude to the Dumlupinar University Scientific Research Project's grants (BAP 2015-70 and BAP 2015-28). The authors thank P. B. Kowalczuk, D.Sc. (Wroclaw University of Technology) for providing quartz samples used in the single bubble experiments and Dr Marta Krasowska (University of South Australia) for proofreading and valuable comments.

International audience; We present the effect of thermal treatment of carbon felt by gas flow containing 1% of oxygen at high temperature on the direct electron transfer and electrocatalytic oxygen reduction currents by a bilirubin oxidase (BOD) film directly adsorbed in the presence of carbon nanotubes on to a porous carbon felt (PCF). The upgraded properties (surface area, pore volume and hydrophilicity) of the resulting porous carbon felt (PCF) in comparison to commercial carbon felt (raw CF), creates a suitable support for the entrapment of MWCNTs bearing negative charges at neutral pH and BOD enzymes, all the components being entrapped in chitosan layer reticulated with glutaraldehyde. Since functional MWCNTs are 2 usually used to facilitate DET, we introduce COOH@MWCNTs, bearing negative charges at neutral pH, in the enzyme layer to evaluate their impact on the electron transfer properties with BOD. The enzyme immobilization efficiency is examined by varying the amount of the components and the immobilization procedure. Linear sweep voltammetry (LSV) and chronoamperometry measurements are used to evaluate the electrochemical behavior of the enzymatic biocathodes. Based on the experimental results, we show that the optimized bioelectrode delivers a current density of 3.70 mA cm-2at 0.15 V vs Ag/AgCl and could retain above 55 % of its initial response after 4 months, proving its outstanding performance. This new bioelectrode allows for optimal DET-type bioelectrocatalytic activity toward O2 reduction and is a very promising candidate for the construction of 3-dimensional cathodes in (bio)-electrochemical devices needing high current output.

Despite remarkable developments in the nanoscience, relatively little is known about the physical (electrostatic) interactions of nanoparticles with bio macromolecules. These interactions can influence the properties of both nanoparticles and the bio-macromolecules. Understanding this bio-interface is a prerequisite to utilize both nanoparticles and biomolecules for bioengineering. In this study, luminescent, water soluble CdTe quantum dots (QDs) capped with mercaptopropionic acid (MPA) were synthesized by organometallic method and then interaction between nanoparticles (QDs) and three different types of proteins (BSA, Lysozyme and Hemoglobin) were investigated by fluorescence spectroscopy at pH= 7.4. Based on fluorescence quenching results, Stern-Volmer quenching constant (Ksv), binding constant (Kq) and binding sites (n) for proteins were calculated. The results show that protein structure (e.g.,globular, metalloprotein, etc.) has a significant role in Protein-Quantum dots interactions and each type of protein influence physicochemical properties of Quantum dots differently.