Search

Abstract: The partitioning behavior of the [Fe(CN)5(NO)]2− and [Fe(CN)6]3− anions were studied in aqueous two-phase systems (ATPS) formed by potassium phosphate and macromolecules—poly(ethylene oxide) (1500gmol−1) and triblock copolymers, PEO–PPO–PEO, where PEO and PPO are poly(ethylene oxide) and poly(propylene oxide), respectively. Two copolymers with different hydrophobicity were used, L35 (50% EO and 1900gmol−1) and F68 (80% EO and 8400gmol−1). The partition coefficient for the [Fe(CN)5(NO)]2− and [Fe(CN)6]3− anions in each ATPS were investigated as a function of the temperature, tie-line length and phases hydrophobicity. The relative order of the partition coefficient is L35

Abstract: This work developed a new and efficient method of extracting and separating Co(II), Ni(II) and Cd(II) in aqueous two-phase systems (ATPS) composed of triblock copolymer (L64)+Na2C4H4O6 +water and L64+Li2SO4 +water using the hydrophobic extractant 1-nitroso-2-naphtol, which complexes the metal ions and partitions in the triblock copolymer micelles in the ATPS top phase. Metal extraction from the salt-rich phase to the copolymer – rich phase is strongly affected by the fine-tuning of the following parameters: amount of added extractant, type of electrolyte, pH, and tie-line length. Excellent separation factors (S i,j) between the metals were obtained at pH = 3.00 (S Co,Cd = 1550 and S Ni,Cd = 16,700) and pH = 1.00 (S Co,Ni = 826). In the interference study, Co(II) was selectivity extracted in the top phase in the presence of Ni(II) and Cd(II) in a concentration of up to 20 times the cobalt level in the system. [Copyright &y& Elsevier]

Abstract: We have investigated the extraction behavior of the metallic ions Co(II), Fe(III) and Ni(II) as a function of the amount of potassium thiocyanate used as an extracting agent, using the following aqueous two-phase systems (ATPS): PEO+(NH4)2SO4 +H2O, PEO+Li2SO4 +H2O, L35+(NH4)2SO4 +H2O and L35+(Li)2SO4 +H2O. Metal extraction from the salt-rich phase to the polymer-rich phase is affected by the following parameters: amount of added extractant, pH, and the nature of the electrolyte and polymer that forms the ATPS. Maximal extraction percentages were obtained for Co(II) (99.8%), Fe(III) (12.7%) and Ni(II) (3.17%) when the ATPS was composed of PEO1500+(NH4)2SO4 +H2O containing 1.4mmol of KSCN at pH 4.0, providing separation factors as high as S Co,Fe =3440 and S Co,Ni =15,300. However, when the same ATPS was used at pH 2.0, the maximal extraction percentages for iron and nickel were 99.5% and 4.34%, respectively, with S Fe,Ni equal to 4380. The proposed technique was shown to be efficient in the extraction of Co(II) and Fe(III), with large viability for the selective separation of Co(II) and Fe(III) ions in the presence of Ni(II). [Copyright &y& Elsevier]

Abstract: We have synthesized 10,12-pentacosadyinoic acid (PCDA)+ N-[(2-tetradecanamide)-ethyl]-ribonamide (TDER) vesicles to determine the colorimetric response induced by pathogenic bacteria (Staphylococcus aureus and Escherichia coli). The addition of bacterial supernatants caused a colorimetric transition in TDER/PCDA vesicles, even in diluted concentrations, indicating that chemical interactions occur between the vesicles and bacterial compounds. Bacterial substrates released from S. aureus induced a greater color change compared to the color change induced by E. coli. S. aureus metabolites also induced a greater color change when TDER/PCDA vesicles were incorporated into the cellulose strips. We determined the energy involved in the interaction between the bacterial substrates and the TDER/PCDA vesicles to be exothermic (and very high) for both bacterial supernatants. In addition, we analyzed the colorimetric transition in the presence of other molecules, using apple juice as a food matrix. Both apple juice and apple juice inoculated with bacterial substrates induced a TDER/PCDA color change; however, the S. aureus supernatant induced a slightly greater color change in the vesicles both in the suspension and in the cellulose strips. TDER/PCDA vesicles show great potential to be used as a biosensor to detect food pathogens in intelligent food packaging. [Copyright &y& Elsevier]

Biosensors offer the potential for real-time pathogen detection. Polydiacetylene (PDA) is an ideal choice for use as a sensor due to its unique optical properties. PDA molecules can form thin films or vesicles that change color from deep blue to red in response to different stimuli, like temperature, pH, and the presence of biological molecules. PDA films and vesicles have been proven to be promising devices for the detection of bacteria and bacterial toxins. Langmuir troughs (for films) and microcalorimetry (for vesicles) are among the many techniques used to characterize PDA films and vesicles. In order to enable more applications of PDA films, it is imperative to elucidate and gain a deeper understanding of the molecular interactions associated with their color change. In addition, it is necessary to transfer the PDA film onto a solid support like plastic in order to incorporate PDA biosensors into an intelligent packaging system. Through the use of such a system, consumers can monitor food quality, thereby preventing foodborne outbreaks. In this review, we discuss the formation of PDA films and vesicles, their characteristics, and their potential applications as biosensors. The possibility to incorporate PDA biosensors into an intelligent packaging system to be used in the food industry is also explored. [ABSTRACT FROM AUTHOR]

Abstract: A greener and more sensitive spectrophotometric procedure has been developed for the determination of phenol and o-cresol that exploits an aqueous two-phase system (ATPS) using a liquid–liquid extraction technique. An ATPS is formed mostly by water and does not require organic solvent. Other ATPS components used in this study were the polymer, polyethylene oxide, and some salts (i.e., Li2SO4, Na2SO4 or K2HPO4 +KOH). The method is based on the reaction between phenol, sodium nitroprusside (NPS) and hydroxylamine hydrochloride (HL) in an alkaline medium (pH 12.0), producing the complex anion [Fe2(CN)10]10− that spontaneously concentrates in the top phase of the system. The linear range was 1.50–500μgkg−1 (R ≥0.9997; n =8) with coefficients of variation equal to 0.38% for phenol and 0.30% for o-cresol (n =5). The method yielded limits of detection (LODs) of 1.27 and 1.88μgkg−1 and limits of quantification (LOQs) of 4.22 and 6.28μgkg−1 for phenol and o-cresol, respectively. Recoveries between 95.7% and 107% were obtained for the determination of phenol in natural water and wastewater samples. In addition, excellent agreement was observed between this new ATPS method and the standard 4-aminoantipyrine (4-AAP) method. [Copyright &y& Elsevier]

Abstract: This study evaluated the partitioning of ovomucoid from egg white, in aqueous two-phase systems (ATPS) composed of PEG 1500 and inorganic salt (lithium sulfate, sodium sulfate, magnesium sulfate, sodium carbonate or sodium citrate) at 25°C. The results showed a great effect of the electrolyte nature on the partition coefficient. The partition coefficient value ranges from 0.02 to 6.0. The highest partition coefficients were obtained from systems composed of sodium carbonate and the lowest in systems composed of magnesium sulfate. In the system containing magnesium sulfate, a recovery percentage greater than 90% was obtained. [Copyright &y& Elsevier]

Abstract: The objective of this study was to determine the thermodynamic parameters (Δ tr G, Δ tr H and Δ tr S) associated with lysozyme and conalbumin partitioning in aqueous two-phases systems (ATPS). Influence of salt type and polyethylene glycol (PEG) concentrations on the partition coefficient of lysozyme and conalbumin from egg white was studied. The evaluated ATPS were composed of PEG 1500 and inorganic salts (sodium citrate and sodium sulfate) at a temperature of 25°C and pH 7.0, with PEG 1500gmol−1 concentrations of 14%, 16% and 18% (mass basis). Partitioning of lysozyme in PEG–citrate ATPS was enthalpically driven, however the PEG–sulfate ATPS was entropically driven. The tested systems can be employed for the separation of these two proteins in egg white, due to the fact that lysozyme migrates toward the polymeric phase and conalbumin to the saline phase in both ATPS. A high recovery of conalbumin in the saline phase of the PEG–sulfate ATPS was determined to be enthalpically driven. [Copyright &y& Elsevier]

Abstract: The extraction behavior of the ions Ni(II), Fe(III), Cd(II), Co(II), Zn(II) and Cu(II) was studied as a function of the amount of extractant added, in aqueous two-phase systems (ATPS) formed mostly by water and without the use of any organic solvent. The others ATPS components were a triblock copolymer (L35) and Na2SO4. Two types of water-soluble extractants (thiocyanate, iodide) and one slightly water-soluble extractant [1-nitroso-2-naphthol (1N2N)] were studied separately. It must be emphasized that this is the first study using a slightly water-soluble complexant for the metallic partition in ATPS, which was not a restrictive factor to the technique as believed. The extraction to the L35 rich-phase of all suited metal ions was insignificant without extractant addition. However, the effectiveness of SCN− in extracting metal ions in the system could be observed in the following sequence: Zn(II)≅Co(II)>Cd(II)>Cu(II)>Fe(III)>Ni(II), with Zn(II), Co(II) and Cd(II) quantitatively extracted and Cu(II) enriched by almost 80%. In the case of the I− extractant, all metal ions, except Cd(II) and Cu(II), remained in the salt-rich phase, providing favorable conditions to the selective separation of Ni(II), Co(II) and Fe(III) ions from Cd(II). The results show that, at pH 7.2, L35/Na2SO4/H2O ATPS can be used with 1N2N as extractant, to separate Co(II) from a complex mixture containing Fe(III), Zn(II) and Cd(II). It was observed, when using 1N2N, that a significant increase in metal extraction takes place as the pH increases, except for Cd(II) and Zn(II). [Copyright &y& Elsevier]

To explore in vivo application of quantum dots (QDs), it is essential to understand the dynamics and energetics of interactions between QDs and proteins. Here, surface plasmon resonance (SPR) and molecular docking were employed to investigate the kinetics and thermodynamics of interactions between human serum albumin (HSA) and CdTe QDs (~3 nm) functionalized with mercaptopropionic acid (MPA) or thioglycolic acid (TGA). Kinetic analysis showed that HSA–QD interactions involved transition-complex formation. Despite the structural similarities between MPA and TGA, the [HSA−CdTe@TGA]‡ formation by association of free HSA and QDs demanded 70% more energy and higher entropic gain (E a − TGA ‡= 65.10 and T ∆ S a − TGA ‡= 28.62 kJ mol−1) than the formation of [HSA−CdTe@MPA]‡ (E a − MPA ‡ = 38.13 and T ∆ S a − MPA ‡ = 0.53kJ mol−1). While the [HSA−CdTe@MPA]° dissociation required higher energy and lower entropy loss (E d − MPA ‡ = 49.96 and T ∆ S d − MPA ‡ = − 32.18kJ mol−1) than the [HSA−CdTe@TGA]° dissociation (E d − TGA ‡= 30.78 and T ∆ S d − TGA ‡= − 51.12 kJ mol−1). The stability of [HSA−QDs]° was independent of the temperature and functionalizing group. However, the enthalpic and entropic components were highly affected by the substitution of MPA (ΔH ° = − 11.83 and TΔS ° = 32.72 kJ mol−1) with TGA (ΔH ° = 34.31 and TΔS ° = 79.73 kJ mol−1). Furthermore, molecular docking results indicated that the metal site on the QDs contributes to the stabilization of [HSA−QDs]°. Therefore, differences in QD functionalization and surface coverage densities can alter the HSA–QD interaction, thus their application. [Display omitted] • Human serum albumin (HSA) binds to CdTe quantum dots (QD) with high affinity. • [HSA − CdTe @ MPA]° stable complex formation was enthalpic and entropically favorable. • [HSA − CdTe @ TGA]° stable complex formation was entropically driven. • The QD surface coverage highly affects the thermodynamic and kinetic parameters. • The HSA-QD interaction mechanism is altered by the QD surface coverage density. [ABSTRACT FROM AUTHOR]

A bioadsorbent (CEDA) capable of adsorbing As(V) and Cu(II) simultaneously was prepared by tosylation of microcrystalline cellulose (MC) and nucleophilic substitution of the tosyl group by ethylenediamine. MC, tosyl cellulose, and CEDA were characterized by elemental C, H, N, and S analysis, infrared spectroscopy, and 13C solid-state nuclear magnetic resonance spectroscopy. The adsorption of As(V) and Cu(II) on CEDA was evaluated as a function of solution pH, contact time, and initial solute concentration. The maximum adsorption capacities of CEDA for As(V) and Cu(II) were 1.62 and 1.09 mmol g−1, respectively. The interactions of As(V) and Cu(II) with CEDA were elucidated using thermodynamic parameters, molecular quantum mechanics calculations, and experiments with ion exchange of Cd(II) by Cu(II), and As(V) by SO 4 2−. Adsorption enthalpies were determined as a function of surface coverage of the CEDA, using isothermal titration calorimetry, with Δ ads H ° values of −32.24 ± 0.07 and −93 ± 2 kJ mol−1 obtained for As(V) and Cu(II), respectively. The potential to reuse CEDA was evaluated and the interference of other ions in the adsorption of As(V) and Cu(II) was investigated. Multi-component experiments showed that Cd(II), Co(II), Ni(II), and Pb(II) did not interfere in the adsorption of Cu(II), while SO 4 2− inhibited As(V) adsorption. [ABSTRACT FROM AUTHOR]

The complexation between protein and polyphenol affects their biological functions. A complete understanding of such interactions requires comprehensive thermodynamic and kinetic characterizations. Surface plasmon resonance (SPR) and fluorescence spectroscopy (FS) described similarly the thermodynamic of interaction between bovine lactoferrin (bLF) and epigallocatechin-3-gallate (EGCG). The formation of the bLF-EGCG complex is spontaneous (Δ G S P R o ≈ -29.00 kJ mol−1, Δ G F S o ≈ -26.00 kJ mol−1) and entropically driven (Δ H S P R o = 14.26, Δ H F S o = 10.20 kJ mol−1 and T Δ S S P R o ≈ 43.00, T Δ S F S o ≈ 36.00 kJ mol−1). The kinetic parameters obtained by SPR showed that the reaction occurs through an activated complex, whose energetic formation parameters from the association of free molecules ( E a c t (a) = 49.5 kJ mol−1, Δ H a ‡ = 47.0 kJ mol−1, and T Δ S a ‡ = −2.10 kJ mol−1) were higher than those in the opposite direction (namely the dissociation of the stable complex, E a c t (d) = 17.4 kJ mol−1, Δ H d ‡ = 32.8 kJ mol−1, and T Δ S d ‡ = −45.10 kJ mol−1), except for Δ G ‡ (Δ G a ‡ = 49.1 kJ mol−1 and Δ G d ‡ = 77.9 kJ mol−1). This study provides useful information for optimizing the use of bLF – EGCG complex as a bioactive compound in different systems, such as medical, food, cosmetic, and pharmaceutical formulations. Image 1 • Epigallocatechin-3-gallate (EGCG) and bovine lactoferrin (bLF) form a stable complex. • bLF – EGCG complex formation was driven by enthalpic and entropic interactions. • bLF – EGCG complex formation proceeded through an intermediate complex. • Intermediate formation from free EGCG and bLF was accompanied by an entropy decrease. • Fluorescence spectroscopy supported SPR thermodynamic binding parameters. [ABSTRACT FROM AUTHOR]

• β-casein and quercetin form supramolecular complexes driven by an entropic increase • Increase in temperature favored the thermodynamically stable complex formation • The interaction process was equally affected by both studied Hofmeister ions • KCl or KSCN increased the stability of the β-casein/quercetin complexes Characterizing the energetics and molecular dynamics of binding between proteins and bioactive compounds is strategic. Using surface plasmon resonance, we demonstrated that β-casein (β-cas) and quercetin (Qct) form supramolecular complexes driven by an increase in entropy (ΔH° = 25.86 and TΔS° =53.49 kJ∙mol-1 at 25 °C). It was possible to infer that the β-cas/Qct complex was formed via an activated complex synthesized by an entropic reduction (TΔS‡ (a) = -15.31 kJ mol-1 and TΔS‡ (d) = -68.80 kJ mol-1 at 25 °C) and an enthalpic increase (ΔH‡ (a) = 30.87 and ΔH‡ (d) =5.0 kJ∙mol-1 at 25 °C). Independent of the nature of the Hofmeister ions, the salts KCl or KSCN increased complex stability by decreasing both the kinetic and thermodynamic enthalpy values, through shielding of the electrostatic interactions at the electric double layer of the interacting molecules. An increase in temperature favored both the association of the free interacting molecules and the dissociation of the thermodynamically stable β-cas/Qct complexes. These results provide insights into the β-cas/Qct interaction process and contribute to the understanding of how Hofmeister ions can modulate intermolecular interactions between proteins and small molecules. [ABSTRACT FROM AUTHOR]

Determine the thermodynamic and kinetic parameters of interaction between micellar casein (MC) and curcumin (CUR) is useful for the application of MC-CUR systems in food products. We used surface plasmon resonance (SPR) and ultraviolet-visible spectrophotometry (UV–vis) to study the complex formation between MC obtained from skimmed milk and CUR, MC carrying capacity, and thermal protection for CUR at a pH of 6.6. An MC could carry about 18,000 molecules of CUR. SPR suggested an enthalpy-driven process (∆H° = −64.63 kJ∙mol−1 and T∆S° ranging from −42.45 to −44.46 kJ∙mol−1). Temperature increased reduced the rate of MC-CUR complex formation and increased its dissociation rate. The activation energy for the formation of MC-CUR activated complexes was negative for association of free MC and CUR molecules (−62.8 kJ mol−1) and positive for dissociation of the thermodynamically stable complexes (1.80 kJ mol−1). MC protected the CUR against its thermal degradation when it was subjected to different temperatures (30, 40, 50, and 60 °C for 5.5 h). This study shows the importance of characterizing MC-small molecules interactions for better application of MC as a nanocarrier. • Micellar casein (MC) of 180 nm can carry about 18,000 molecules of curcumin (CUR). • SPR measurements showed that the MC-CUR complex formation was exothermic. • Temperature increasing reduced MC-CUR association but increased its dissociation rate. • MC exhibited thermal protection for CUR. [ABSTRACT FROM AUTHOR]

Highlights • Polydiacetylene (PDA)/triblock copolymer (TC)/surfactant (SDS) formed nanosensor. • Enrofloxacin (ENRO) induced a colorimetric transition (CT) in the PDA/TC/SDS sensor. • Energy released by ENRO–SDS interaction was the driving force for PDA color change. • Limit of detection of sensor to ENRO was five times smaller than the allowed by EU. • PDA/TC/SDS sensor shows potential to be applied for detecting ENRO in foods. Abstract Colorimetric nanosensors formed of polydiacetylene (PDA), triblock copolymer (L64 or F68), and sodium dodecyl sulfate (SDS), so-called nanoblends, were developed to detect enrofloxacin (ENRO) in aqueous media. The nanosensors show hydrodynamic diameter ranging from 234.2 ± 3.5 to 801.6 ± 17.8 nm for SDS concentrations of 13.0–21.0 mM, respectively. The lowest limit of detection was 0.054 µM, which is five times smaller than the maximum limit allowed by the European Union. The response surfaces showed that both the SDS and ENRO concentrations influenced the colorimetric response (p < 0.05), and kinetic rate of colorimetric transition (R CT). SDS concentration between 11.0 and 14.0 mM in the nanoblend yielded the most sensitive nanosensors for detecting ENRO. When L64 was replaced by F68, the colorimetric response of the nanoblends was similar, but PDA/F68/SDS showed a slower R CT than PDA/L64/SDS. The developed nanosensor is a sensitive and simple device for the fast detection of ENRO. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Sugarcane bagasse cellulose mixed ester succinate phthalate (SBSPh) was synthesized by a novel one-pot reaction method. The effects of temperature, time and mole fraction of succinic anhydride (χ SA) on the responses weight gain (wg), number of carboxylic acid groups (n T,COOH), and adsorption capacity (q) of Co2+ and Ni2+ were evaluated by a 23 experimental design. The chemical structure of the material was elucidated by Fourier transform infrared, 13C Multiple Cross-Polarization solid-state NMR spectroscopy and 1H NMR relaxometry. The best SBSPh synthesis condition (100 °C, 11 h, χ SA of 0.2) yielded a wg of 59.1%, n T,COOH of 3.41 mmol g−1, and values of q Co 2+ and q Ni 2+ of 0.348 and 0.346 mmol g−1, respectively. The Sips model fitted better the equilibrium data, and the maximum adsorption capacities (pH 5.75 and 25 °C) estimated by this model were 0.62 and 0.53 mmol g−1 for Co2+ and Ni2+, respectively. The Δ ads H ° values estimated by isothermal titration calorimetry were 8.43 and 7.79 kJ mol−1 for Co2+ and Ni2+, respectively. Desorption and re-adsorption efficiencies were evaluated by a 22 experimental design, which showed that SBSPh adsorbent can be recovered and reused without significant loss of adsorption capacity. [ABSTRACT FROM AUTHOR]

Here, investigation was made of the interaction between lactoferrin (Lf) and the anionic surfactants sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), and sodium decyl sulfate (DSS), using isothermal titration calorimetry, Nano differential scanning calorimetry (NanoDSC), and fluorescence spectroscopy. The Lf-surfactant interaction was enthalpically favorable (the integral enthalpy change ranged from −5.99 kJ mol −1 , for SDS at pH 3.0, to −0.61 kJ mol −1 , for DSS at pH 12.0) and promoted denaturation of the protein. The Lf denaturation efficiency followed the order DSS < SDS < SDBS. The adsorption capacity of the protein with respect to surfactant strongly depended on pH and the surfactant structure, reaching a maximum value of 505 SDBS molecules per gram of Lf at pH 3.0. The different efficiencies of the surfactants in denaturing Lf were attributed to the balance of hydrophobic and electrostatic interactions, which also depended on pH and the surfactant structure, highlighting the SDBS-tryptophan residue specific interaction, where SDBS acted as a quencher of fluorescence. Interestingly, the NanoDSC and fluorescence measurements showed that the ferric ion bound to Lf increased its stability against denaturation induced by the surfactants. The results have important implications for understanding the influence of surfactants on structural changes in metalloproteins. [ABSTRACT FROM AUTHOR]

In the second part of this series of studies, the monocomponent adsorption of Cu 2+ , Co 2+ and Ni 2+ onto STA adsorbent in a fixed-bed column was investigated and optimized using a 2 2 central composite design. The process variables studied were: initial metal ion concentration and spatial time, and the optimized responses were: adsorption capacity of the bed ( Q max ), efficiency of the adsorption process ( EAP ), and effective use of the bed ( H ). The higher Q max for Cu 2+ , Co 2+ and Ni 2+ were 1.060, 0.800 and 1.029 mmol/g, respectively. The breakthrough curves were modeled by the original Thomas and Bohart-Adams models. The changes in enthalpy (Δ ads H °) of adsorption of the metal ions onto STA were determined by isothermal titration calorimetry (ITC). The values of Δ ads H ° were in the range of 3.0–6.8 kJ/mol, suggesting that the adsorption process involved physisorption. Desorption ( E des ) and re-adsorption ( E re-ads ) of metal ions from the STA adsorbent were also investigated in batch mode, and the optimum conditions were applied for three cycles of adsorption/desorption in a fixed bed column. For these cycles, the lowest values of E des and E re-ads were 95 and 92.3%, respectively, showing that STA is a promising candidate for real applications on a large scale. [ABSTRACT FROM AUTHOR]

Trimellitated-sugarcane bagasse (STA) was used as an environmentally friendly adsorbent for removal of the basic dyes auramine-O (AO) and safranin-T (ST) from aqueous solutions at pH 4.5 and 7.0. Dye adsorption was evaluated as a function of STA dosage, agitation speed, solution pH, contact time, and initial dye concentration. Pseudo-first- and pseudo-second-order, Elovich, intraparticle diffusion, and Boyd models were used to model adsorption kinetics. Langmuir, Dubinin-Radushkevich, Redlich-Peterson, Sips, Hill-de Boer, and Fowler-Guggenheim models were used to model adsorption isotherms, while a Scatchard plot was used to evaluate the existence of different adsorption sites. Maximum adsorption capacities for removal of AO and ST were 1.005 and 0.638 mmol g −1 at pH 4.5, and 1.734 and 1.230 mmol g −1 at pH 7.0, respectively. Adsorption enthalpy changes obtained by isothermal titration calorimetry (ITC) ranged from −21.07 ± 0.25 to −7.19 ± 0.05 kJ mol −1 , indicating that both dyes interacted with STA by physisorption. Dye desorption efficiencies ranged from 41 to 51%, and re-adsorption efficiencies ranged from 66 to 87%, showing that STA can be reused in new adsorption cycles. ITC data combined with isotherm studies allowed clarification of adsorption interactions. [ABSTRACT FROM AUTHOR]

The demand for bioactive molecules, such as ß- carotene (ß-car), has increased, but some characteristics such as low water solubility and low photo stability limit its application in many formulations. The bioactive entrapment into milk proteins may overcome this barrier. Thus, the aim of this work was to study the interaction between ß-car and bovine serum albumin (BSA) or ß-casein and the photo stability of this bioactive in the presence of the proteins. Fluorescence spectroscopy showed that at pH 7.0, increasing concentrations of ß-carotene reduced the fluorescence intensity of both proteins, and the fluorescence-quenching mechanism is mainly static. The stoichiometry of the ß-car/protein complex varied between proteins, being 1:1 to native BSA, 1:3 to denatured BSA (d-BSA), and 1:2 for ß-casein. The standard Gibbs-free energy (ΔG°) of complex formation was negative for all systems studied and followed the order ΔG°BSA <ΔG°ß-casein <ΔG°d-BSA. The formation of ß-car/protein complex was driven by entropy increasing in all studied conditions. Both proteins improved ß-car photo stability, but ß-casein micelle was more efficient, reducing and increasing four times, respectively, the bioactive degradation constant and the halftime of ß-car. The overall results pointed to the strategic use of milk proteins, especially ß-casein micelles as nanovehicle for ß-car in food and other systems. [ABSTRACT FROM AUTHOR]

Bovine serum albumin (BSA)/curcumin binding and dye photodegradation stability were evaluated. BSA/curcumin complex showed 1:1 stoichiometry, but the thermodynamic binding parameters depended on the technique used and BSA conformation. The binding constant was of the order of 10 5 L·mol −1 by fluorescence and microcalorimetric, and 10 3 and 10 4 L·mol −1 by surface plasmon resonance (steady-state equilibrium and kinetic experiments, respectively). For native BSA/curcumin, fluorescence indicated an enthalpic and entropic driven process based on the standard enthalpy change (ΔH ○ F = −8.67 kJ·mol −1 ), while microcalorimetry showed an entropic driven binding process (ΔH ○ cal = 29.11 kJ·mol −1 ). For the unfolded BSA/curcumin complex, it was found thatp ΔH ○ F = −16.12 kJ·mol −1 and ΔH ○ cal = −42.63 kJ·mol −1 . BSA (mainly native) increased the curcumin photodegradation stability. This work proved the importance of using different techniques to characterize the protein-ligand binding. [ABSTRACT FROM AUTHOR]

In the third part of this series of studies, the adsorption of the basic textile dyes auramine-O (AO) and safranin-T (ST) on a carboxylated cellulose derivative (CTA) were evaluated in mono- and bi-component spiked aqueous solutions. Adsorption studies were developed as a function of solution pH, contact time, and initial dye concentration. Adsorption kinetic data were modeled by monocomponent kinetic models of pseudo-first- (PFO), pseudo-second-order (PSO), intraparticle diffusion, and Boyd, while the competitive kinetic model of Corsel was used to model bicomponent kinetic data. Monocomponent adsorption equilibrium data were modeled by the Langmuir, Sips, Fowler-Guggenhein, Hill de-Boer, and Konda models, while the IAST and RAST models were used to model bicomponent equilibrium data. Monocomponent maximum adsorption capacities for AO and ST at pH 4.5 were 2.841 and 3.691 mmol g −1 , and at pH 7.0 were 5.443 and 4.074 mmol g −1 , respectively. Bicomponent maximum adsorption capacities for AO and ST at pH 7.0 were 1.230 and 3.728 mmol g −1 . Adsorption enthalpy changes (Δ ads H ) were obtained using isothermal titration calorimetry. The values of Δ ads H ranged from −18.83 to −5.60 kJ mol −1 , suggesting that physisorption controlled the adsorption process. Desorption and re-adsorption of CTA was also evaluated. [ABSTRACT FROM AUTHOR]

Polydiacetylene (PDA) vesicles have been applied as optical sensors in different areas, although there are difficulties in controlling their responses. In this study, we prepared nanoblends of PDA with triblock copolymers (TC) as a better sensor system for detecting temperature change. The influences of diacetylene (DA) monomer, and the TC chemical structure and concentration on the colorimetric response (CR) were examined. The TC/PDA nanoblend was remarkably more sensitive to temperature change, than classical vesicles. A higher L64 concentration of 12.0% (w/w) reduced the chromatic transition temperature (T tr ) to as low as 24 °C. When using different TCs, the T tr values can be ordered as L35 < F68< L64 < F127

Cinnamic acid (CA) and methyl cinnamate (MC) have attracted interest of researchers because of their broad therapeutic functions. Here, we investigated the interaction of CA and MC with bovine serum albumin (BSA) at pH 3.5, 5.0, and 7.4 using fluorescence spectroscopy, differential scanning nanocalorimetry, and measurements of interfacial tension, size, and zeta potential. BSA formed a complex with the ligands with stoichiometry of approximately 1.0. At pH 7.4, CA-BSA complex formation was entropically driven. The interaction between MC and BSA was more favorable than with CA and was enthalpically driven under the same conditions. The pH played an important role in BSA conformation, which altered the manner in which it interacts with the ligands. Interestingly, both CA and MC had no effect on the surface tension of BSA/air interfaces. These data contribute to the knowledge of CA/MC-BSA interactions and provide important data for application in the food industry. [ABSTRACT FROM AUTHOR]

To optimize the therapeutic applications of Congo red (CR), a potential inhibitor of protein aggregation, the kinetics and thermodynamics of the interactions between CR and a model protein need to be understood. We used surface plasmon resonance (SPR) and fluorescence techniques to determine the dynamics and thermodynamic parameters for the formation of complexes between CR and bovine serum albumin (BSA). CR interacts with BSA through a transition complex; the activation energy for association (E act(a) ) was determined to be 35.88 kJ mol −1 , while the activation enthalpy (ΔH ‡ ), entropy (ΔS ‡ ), and Gibbs free energy (ΔG ‡ ) are 33.41 kJ mol −1 , 0.18 J mol −1 K −1 , and 33.35 kJ mol −1 , respectively. When this intermediate transforms into the final CR-BSA complex, the entropy of the system increases and part of the absorbed energy is released; this process is associated with a reverse activation energy (E act(d) ) of 20.17 kJ mol −1 , and values of ΔH ‡ , ΔS ‡ , and ΔG ‡ of 17.69 kJ mol −1 , −162.86 J mol −1 K −1 , and 66.25 kJ mol −1 , respectively. A comparison of the SPR and fluorescence results suggests that there is more than one site where BSA interacts with CR. [ABSTRACT FROM AUTHOR]

Carbonaceous materials have been extensively studied as highly efficient adsorbents for the removal of dyes from wastewater. However, investigations of thermodynamic aspects of the interactions between these materials and dyes remain scarce. This paper describes the thermodynamics of the interactions between the Ponceau 4R (PR), Congo Red (CR), and Allura Red (AR) dyes and multi-walled carbon nanotubes (MWCNTs). The interactions between the dyes and activated carbon (AC) were also evaluated for comparison. The investigation used a combination of adsorption isotherms and isothermal titration nanocalorimetry (ITC) measurements, and a thermodynamic approach provided full characterization of the adsorption process. For both MWCNT and AC, the amount of adsorbed dye ( Γ D ) increased in the order Γ D (PR) < Γ D (AR) < Γ D (CR), and the adsorption capacity normalized by the adsorbent specific area was up to 5.6 times higher for MWCNT. The maximum amount adsorbed ( Γ D,max ) reached values of up to 2.00 μmol m −2 for CR adsorption on MWCNT. For both adsorbents, the process of dye adsorption was enthalpically driven and entropically unfavorable. All the thermodynamic parameters depended on the surface coverage and the structures of both dye and adsorbent. The adsorption enthalpy change (Δ ads H ) and entropy change (TΔ ads S ref ) values were higher than −137.0 kJ mol −1 and −114.2 kJ mol −1 , respectively. In addition to the structural differences between MWCNT and AC, the ITC data suggested that the adsorption sites are heterogeneous and that the dyes preferentially adsorb on the more hydrophilic sites on the adsorbent surfaces. [ABSTRACT FROM AUTHOR]

Ponceau 4R (P4R) and bovine serum albumin (BSA) may interact changing food properties. We compared fluorescence spectroscopy and surface plasmon resonance (SPR) for studying, in vitro , the interactions between BSA and P4R at pH 7.4 and 3.5 in different temperatures. Fluorescence data pointed to the formation of a complex where P4R was bound on site I or II of BSA, with a stoichiometry around one and a binding constant (K b ) ranging from 1.37 × 10 5 to 20.15 × 10 6 L mol −1 . The complex formation at both pH was enthalpically driven (standard enthalpy change, ΔH° F = −60.69 and −63.06 kJ mol −1 , for pH 7.4 and 3.5, respectively). Using SPR, we also found the formation of 1:1 BSA-P4R complexes, but the calculated K b values were much smaller, on the order of 10 3 L mol −1 . Again, we found that the formation of BSA-P4R complex was driven by enthalpy decreasing; however the standard enthalpy change was less negative than that found by fluorescence (ΔH° SPR = −15.05 and −40.55 kJ mol −1 , at pH 7.4 and 3.5, respectively). Our results show that these distinct techniques provided different thermodynamic binding parameters for the BSA-P4R interaction, especially regarding ΔH° values, indicating that BSA-P4R binding was a multisite phenomenon, and that sites far from tryptophan residues were the main responsible by electrostatic interaction. Thus, this work clearly shows the importance of using complementary techniques for a complete thermodynamic characterization of complexes formed between azo-colorants and proteins; which is directly related to physicochemical properties of systems containing both molecules together. [ABSTRACT FROM AUTHOR]

The interaction between Allura Red and bovine serum albumin (BSA) was studied in vitro at pH 7.4. The fluorescence quenching was classified as static quenching due to the formation of AR–BSA complex, with binding constant (K) ranging from 3.26 ± 0.09 to 8.08 ± 0.06 10 4 L.mol −1 , at the warfarin binding site of BSA. This complex formation was driven by increasing entropy. Isothermal titration calorimetric measurements also showed an enthalpic contribution. The Allura Red diffusion coefficient determined by the Taylor-Aris technique corroborated these results because it reduced with increasing BSA concentration. Interfacial tension measurements showed that the AR–BSA complex presented surface activity, since interfacial tension of the water-air interface decreased as the colorant concentration increased. This technique also provided a complexation stoichiometry similar to those obtained by fluorimetric experiments. This work contributes to the knowledge of interactions between BSA and azo colorants under physiological conditions. [ABSTRACT FROM AUTHOR]

Bovine serum albumin (BSA) has been recognized as a marker of the cow's health, milk quality, an allergenic protein and as a carrier. Its detection is important in the food, pharmaceutical and medical industries. However, traditional techniques used to detect BSA are often time-consuming, expensive, and show limited sensitivity. This paper describes properties of polydiacetylene-triblock copolymer (L64) nanosensors, synthesized to easily detect BSA. Sensor efficiency was studied as a function of nanosensor composition, polydiacetylene chemical structures, BSA conformation and hydrophobic domain availability, using spectroscopic, calorimetric, light scattering, and electrokinetic analyses. Nanosensors were sensitive to detect the average BSA concentration of milk and dairy products and discriminated between native and denatured protein through naked-eye detectable blue-to-red transition. The standard Gibbs free energy (− 10.44 < ΔG° < − 49.52 kJ M), stoichiometry complex (1 < “n” < 3), and binding constant (6.7 × 10 2 < K a < 4.79 × 10 8 M − 1 ) of BSA-nanosensor complex formation established a direct relationship between nanosensor response and BSA-nanosensor interaction. BSA-nanosensor interaction was entropically (without cholesterol), and enthalpically driven (with cholesterol). Eugenol-BSA complex did not induce colorimetric transition. Polydiacetylene-L64 nanosensors are potential low-cost sensors for rapid detection of BSA, discriminating between native/denatured and free/bound protein. [ABSTRACT FROM AUTHOR]

A new carboxylated cellulose derivative (CTA) was prepared from the esterification of cellulose with 1,2,4-Benzenetricarboxylic anhydride. CTA was characterized by percent weight gain ( pwg ), amount of carboxylic acid groups ( n COOH ), elemental analysis, FTIR, TGA, solid-state 13 C NMR, X-ray diffraction (DRX), specific surface area, pore size distribution, SEM and EDX. The best CTA synthesis condition yielded a pwg and n COOH of 94.5% and 6.81 mmol g −1 , respectively. CTA was used as an adsorbent material to remove Co 2+ , Cu 2+ and Ni 2+ from monocomponent spiked aqueous solution. Adsorption studies were developed as a function of the solution pH, contact time and initial adsorbate concentration. Langmuir model better fitted the experimental adsorption data and the maximum adsorption capacities estimated by this model were 0.749, 1.487 and 1.001 mmol g −1 for Co 2+ , Cu 2+ and Ni 2+ , respectively. The adsorption mechanism was investigated by using isothermal titration calorimetry. The values of Δ ads H ° were in the range from 5.36 to 8.09 kJ mol −1 , suggesting that the mechanism controlling the phenomenon is physisorption. Desorption and re-adsorption studies were also performed. Desorption and re-adsorption efficiencies were closer to 100%, allowing the recovery of both metal ions and CTA adsorbent. [ABSTRACT FROM AUTHOR]

Aqueous two-phase systems (ATPSs) are strategic liquid-liquid systems for extraction and purification of compounds. However, only a few studies have evaluated the thermodynamic parameters that allow comprehension of the partition process of different molecules. Here, we investigated the chymosin (Chy) partitioning behavior in macromolecule + salt + water ATPSs by obtaining the partition coefficient ( ), Gibbs free energy change of transfererence ( ), enthalpy change of transference ( ), and entropy change of transference ( ), at infinite dilution, and their dependence on the ATPS properties. Chy transfer from the bottom to the top phase of the ATPS was enthalpically driven, with -4.84 kJ mol-1 < < -170.34 kJ mol-1 and -11.69 J mol-1 K-1 < < -558.95 J mol-1 K-1 characterizing an enthalpy-entropy compensation process; -1.36 kJ mol-1 < < -3.77 kJ mol-1. became more negative as the tie-line length increased, showing that specific macromolecule-Chy interactions determine the enzyme concentration in the top phase. The nature of the cation/anion, hydrophobic/hydrophilic balance of the top phase, and macromolecule molar mass influence the intermolecular interaction between Chy and top phase components, changing the enzyme partition behavior. Negative parameters were attributed to the Chy transfer from a higher (bottom phase) to the lower (top phase) configurational entropy region. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermodynamically stable complexes are formed through activated complexes. • The water molecules of the desolvation layer influence the association. • The interaction causes a conformational change at the beta-lactoglobulin site. • At the low temperature (285.15 K) the hydrophobic interaction prevails. • At high temperatures (301.15 K), hydrophilic interactions are dominant. Despite some thermodynamics studies about β-lactoglobulin (βLG) and resveratrol (RES) interactions, there is a gap regarding kinetics data about βLG-RES complex formation. Here, we determined the kinetic and thermodynamic parameters of βLG-RES interactions by using surface plasmon resonance (SPR). The kinetic association parameters were dependent on the 3D water structure present on the solvation shell of both interacting molecules. At lower temperature (285.15 K), all activation energies were positive (E a c t a ‡ = 82.86 kJ.mol−1, T Δ S a ‡ = 32.26 kJ.mol−1, and Δ C p a ‡ = 4.15 kJ.mol−1K−1) due to the higher water structuration on the RES and βLG solvation shell. All these energetic barriers become mainly from the energetic cost for the desolvation process of RES and βLG. At higher temperature (301.15 K), the solvation water structure decreases and all the above activation energies become negative (E a c t a ‡ = - 121.58 kJ.mol−1, T Δ S a ‡ = - 173.59 kJ.mol−1, and Δ C p a ‡ = - 29.92 kJ.mol−1K−1) because the direct interaction between desolvated RES and βLG molecules released more energy than it is absorbed by desolvation process. However, kinetic dissociation parameters were not dependent on the hydrogen bond density of the water solvation shell as showed by the temperature independence of dissociation energetic parameters. This non-dependence of the dissociation process from the desolvation step probably is because the water molecules interacting with the βLG-RES complex is not concentrated around/inside the protein site of interaction. The association of free molecules was 1.5 times faster than the dissociation of the thermodynamically stable complex (Δ G (a) ‡ ≅ 48.15 kJ.mol−1, Δ G (d) ‡ ≅ 73.10 kJ.mol−1). The lower free energy barrier observed for the association came from an isokinetic process where entropic and enthalpic parameters compensated for each other. The ΔG° values indicate that the thermodynamically stable complex predominates over free molecules. At low temperature (285.15 K), the hydrophobic interaction (Δ H° = 73.06 kJ.mol−1; T Δ S° = 99.60 kJ.mol−1) drove the βLG-RES complex formation while at high temperature (301.15 K), hydrophilic interactions became dominant (Δ H° = −142.50 kJ.mol−1; T Δ S° = −118.18 kJ.mol−1). [ABSTRACT FROM AUTHOR]

• Peanut proteins (ARA or CON) interact with Congo red (CR) to form stable complexes. • CON has a higher binding affinity toward CR than does ARA. • Hydrophilic interactions were the main driving forces for [ A R A - C R ] 0 formation process. • The formation of [ C O N - C R ] 0 was enthalpically and entropically driven. • Transition complexes had a more structured conformation than their stable form. The thermodynamics and kinetics of arachin-Congo red (ARA - C R) and conarachin-Congo red (CON - C R) interactions were studied using surface plasmon resonance. KCl led to a reduction of up to 55% in the values of the associated kinetic constants, but it had less influence on the dissociation rates (less than 12%). The change in ionic strength had little effect on the thermodynamic stability of the complexes, but it did reduce their affinities (K b ( 25 ° C) [ A R A - C R ] 0 from 3.52 to 2.44 × 103 M−1 and K b (25 ° C) [ C O N - C R ] 0 from 15.1 to 12.5 × 103 M−1). The shielding of the electrical double layer favored ARA - C R hydrophilic interactions (Δ H [ A R A - C R ] 0 0 decreased from −30.60 to −42.98 kJ mol−1). On the other hand, hydrophobic interactions came to dominate during the formation of [ C O N - C R ] 0 (Δ H [ C O N - C R ] 0 0 increased from −11.21 to 28.34 kJ mol−1 and T Δ S 25 ° C [ C O N - C R ] 0 0 increased from 12.64 to 51.73 kJ.mol−1). The data presented here improve our understanding of plant-based protein nanocarriers of small bioactive molecules. [ABSTRACT FROM AUTHOR]

Polydiacetylene (PDA) and triblock copolymer nanoblends were synthesized to detect micellar casein (MC), the main milk protein and an indicator of milk quality. UV–Vis spectrum showed that MC induced blue-to-red transition in nanoblends. When nanoblends and MC were separated by dialysis membrane colorimetric response (CR) was similar, whereas a remarkable CR reduction was noticed after addition of dialyzed-MC, suggesting that small molecules present in MC (salts) caused PDA color change. Interaction enthalpy variation between nanoblends and MC showed an abrupt increase that coincided with MC concentration when colorimetric transition occurred. Copolymer hydrophobic/hydrophilic balance and presence of other molecules in the system affected nanoblends CR. MC salts were found to interact with nanoblends leading to color changes. MC concentration, MC salt release, copolymer hydrophobic/hydrophilic balance, and presence of other molecules in the system affected responses of the sensors. These results contribute to future applications of PDA/copolymer nanosensors to dairy models. [ABSTRACT FROM AUTHOR]

Recovery of mercury from effluents is fundamental for environmental preservation. A new, green method was developed for separation of mercury from effluent containing different metals. The extraction/separation of Hg(II) was studied using aqueous two-phase system (ATPS) comprising by polyethylene oxide (PEO1500) or triblock copolymers (L64 or L35), electrolyte (sodium citrate or sodium sulfate) and water in the presence or absence of chloride ions. The extraction behavior of the Hg(II) for the macromolecule-rich phase is affected by the following parameters: amount of added extractant, pH, and the nature of the electrolyte and macromolecule of the ATPS. The APTS of PEO1500 + sodium citrate + H 2 O (pH 1.00 and 0.225 mol kg −1 KCl) produced the highest Hg(II) % E = (92.3 ± 5.2)%. Under the same conditions, excellent separation factors (1.54 × 10 2 − 3.21 × 10 10 ) for recovery of mercury in the presence of co-existing metals were obtained. Efficient and selective extraction of Hg(II) from domestic and industrial synthetic effluents was achieved using this ATPS. [ABSTRACT FROM AUTHOR]

It is well-known that ionic liquids (ILs) alter the properties of aqueous systems containing only surfactants. However, the effect of ILs on polymer-surfactant systems is still unknown. Here, the effect of 1-butyl-3-methylimidazolium bromide (bmimBr) and chloride (bmimCl) on the micellization of sodium dodecyl sulfate (SDS) and its interaction with poly(ethylene oxide) (PEO) was evaluated using conductimetry, fluorimetry, and isothermal titration calorimetry. The ILs decreased the critical micellar concentration (cmc) of the surfactant, stabilizing the SDS micelles. A second critical concentration (c2thc) was verified at high SDS concentrations, due to the micelle size decrease. The stability of PEO/SDS aggregates was also affected by ILs, and the critical aggregation concentration (cac) of SDS increased. Integral aggregation enthalpy changed from −0.72 in water to 2.16 kJ mol-1 in 4.00 mM bmimBr. IL anions did not affect the SDS micellization or the beginning of PEO/SDS aggregation. Nevertheless, when chloride was replaced with bromide, the amount of SDS bound to the polymer increased. At 100.0 mM IL, the PEO-SDS interaction vanished. We suggest that the effect of ILs comes from participating in the structure of the formed aggregates, interacting with the SDS monomers at the core/interface of the micelles, and promoting preferential solvation of the polymer. [ABSTRACT FROM AUTHOR]

Partitioning behavior of the whey proteins a-lactalbumin (α-la) and β-lactoglobulin (β-lg) in aqueous two-phase systems prepared with poly ethylene glycol (PEG) and sodium polyacrilate (NaPA) was investigated as a function of pH and polymer concentrations. It was observed that α-la concentrated in the PEG phase while β-lg concentrated in the NaPA phase. Response surface methodology was applied to optimize protein partitioning and to achieve the best conditions for their fractionation. Thermodynamic analysis based on isothermal titration microcalorimetry indicated that the partitioning of α-la was accompanied by endothermic heat and was entropically driven, while β-lg partitioning was accompanied by exothermic heat and was enthalpically driven at low polymer concentrations and entropically driven at high polymer concentrations. Purification and yield parameters were determined using fresh whey and the results allowed for conclusion of the great applicability of this new system for α-la and β-lg fractionation. [ABSTRACT FROM AUTHOR]

Highlights: [•] A green and low cost technique for metal separation was discovered. [•] Aqueous two-phase system (ATPS) is predominantly composed by water. [•] ATPS is an efficient substitute for liquid-liquid extraction using organic solvent. [•] Excellent separation factor for Cu and Zn was obtained. [Copyright &y& Elsevier]

Abstract: Magnesium aluminum layered double hydroxide (LDH) was synthesized by the co-precipitation method followed by calcination. The resulting materials were characterized by X-ray diffraction (PXRD) and attenuated total reflectance with Fourier transform infrared spectroscopy (FTIR/ATR) and simultaneous thermogravimetric analysis/differential scanning calorimetry coupled to mass spectrometry (TGA–DSC–MS). Calcined and non-calcined LDHs were used as adsorbents to remove azo dye Acid Green 68:1 in an aqueous solution. Adsorption experiment results indicated that calcined LDH possesses greater adsorption capacity (154.8mgg−1) than non-calcined LDH (99.1mgg−1). Isotherms showed that adsorption of the dye was more consistent with the Langmuir model. Kinetic experiments of calcined LDH adsorption showed that for low concentration (50, 100 and 200mgL−1), the system reached the adsorption equilibrium in 1, 2, and 4h, and for higher concentration after 10h. The best kinetic model was the pseudo-second order. Adsorption studies also showed that the capacity for adsorption of the dye by calcinated LDH does not significantly diminish with pH level variation. [Copyright &y& Elsevier]

Abstract: In the present study, a thermodynamic analysis was performed using an isothermal titration microcalorimeter to measure changes in the enthalpy of mixing (ΔmixH) of water in microemulsion systems formed by soybean lecithin, isooctane and butanol. These energies were important to determine the driving forces associated with the formation of reverse micelles. It was observed that the titration curves of water in pure isooctane and in isooctane with soybean lecithin present values of ΔmixH equal to −9.46×10−3 kJ/mol and −5.68×10−3 kJ/mol, respectively. This shows that water does not form intermolecular interactions with these components. Exothermic behavior, with values of ΔmixH ranging from +2.17kJ/mol to −1.63×10−2 kJ/mol, was observed from the titration curve of water in systems formed by soybean lecithin, isooctane and butanol. These values were associated with the water dissolution process, where the formation of reverse micelles had been observed in the evaluated systems. Differences in behavior of ΔmixH for the water curves were observed in systems formed by butanol and soybean lecithin, only pure butanol and butanol with isooctane. The curve of the system containing soybean lecithin, butanol and isooctane clearly shows that the formation of aggregates occurred in this system (reverse micelles). Finally, it was also noted that soybean lecithin did not suffer any degradation process, since the energy involved in the process of water titration in the systems containing the same substance was considered low. Thus, soybean lecithin may be used without problems in this type of system. [Copyright &y& Elsevier]

Abstract: We investigated the extraction behavior of Cu(II) in the aqueous two-phase system (ATPS) formed by (L35+MgSO4 +H2O) or (L35+(NH4)2SO4 +H2O) in the presence of the extracting agent 1-(2-pyridylazo)-2-naphthol (PAN). At pH=3 and a PAN concentration of 0.285mmolkg−1, both ATPS lead to the effective separation of Cu(II) from other metallic ions (Zn(II), Co(II), Ni(II) and Fe(III)). High separation factors range between 1000 and 10,000 were obtained for the extraction of Cu(II) and concomitant metallic ions. This ATPS was used for the extraction of Cu(II) from a leached ore concentrate with a extraction percentage of 90.4±1.1%; other metals were mainly located in the bottom phase. [Copyright &y& Elsevier]

Abstract: Partitioning of the natural dye norbixin has been studied in aqueous two-phase system (ATPS) that are formed by mixing aqueous solutions of a polymer (or copolymer) and an organic salt (sodium tartrate or succinate). In this work, the norbixin partition coefficient (K N) was optimized, taking into account the variables of polymer concentration, salt concentration and pH. It was found that K N is highly dependent on the electrolyte nature, system hydrophobicity and TLL values. Testing produced K N values between 8 and 130, indicating the great potential of ATPS as a method for norbixin pre-concentration/purification. Thermodynamic transfer parameters (Δtr G, Δtr H, Δtr S) indicate that the preferential concentration of norbixin in the top phase is favored by enthalpic and entropic contributions. [Copyright &y& Elsevier]

The present study includes measurements of the phase composition, density, and refractive index of aqueous two-phase systems of poly(ethylene oxide) 1500 (PEO1500) + sodium thiosulfate + H2O at (283.15, 298.15, and 313.15) K. With the experimental results obtained, phase diagrams were established, and the influence of temperature on the densities, binodal position, and refractive index values was analyzed and discussed. The experimental tie-lines were described using the Othmer–Tobias correlation. The experimental aqueous two-phase system data were correlated with the nonrandom two-liquid (NRTL) thermodynamic model for the activity coefficients; the results were considered excellent according to a global root-mean-square deviation of 0.97 %. [ABSTRACT FROM AUTHOR]

Abstract: In order to develop a new strategy for β-lactoglobulin (β-lg) removal from whey protein, partitioning of α-lactalbumin (α-la), β-lg and glycomacropeptide (Gmp) was studied using aqueous two phase systems (ATPS). A system composed of 13% (w/w) polyethylene glycol (PEG, average molar mass 2000g/mol) and 13% (w/w) potassium phosphate was used at 25°C. A central composite rotatable design (CCRD) associated to the response surface methodology (RSM) was applied to investigate the effects of NaCl concentration and pH on the partition of these proteins. It was found that α-la and Gmp partitioned to the top phase rich in PEG, whereas β-lg partitioned to the bottom phase rich in salt. According to the RSM, optimal conditions for β-lg removal where found where pH was equal to 6.7 and salt concentration was 0.35mol/L. Under these conditions, the partition coefficient K α was 0.48 and K Gmp was 0.92. On the other hand, the partition coefficient K β was only 0.01. In such conditions β-lg preferentially concentrates in the bottom phase, while the top phase exclusively contains the proteins α-la and Gmp. Fractionation of the proteins from fresh whey was performed in a three stage cross-flow extraction system. The extraction yield for β-lg in the bottom phase was 97.3%, while the yields for α-la and Gmp in the top phase were 81.1% and 97.8%, respectively. [Copyright &y& Elsevier]

Abstract: The phase diagrams of PEO1500+sodium tartrate+water, PPO400+sodium tartrate+water, PEO1500+sodium succinate+water, PPO400+sodium succinate+water, PEO1500+sodium citrate+water, PPO400+sodium citrate+water and PPO400+sodium acetate+water aqueous two-phase systems were determined at (283.15, 298.15, and 313.15)K. Both equilibrium phases composition were analyzed by conductimetry and refractive index. In this paper, the influences of polymer hydrophobicity, salt nature and temperature on the phase diagram were analyzed. The phase separation processes was endothermic and the hydrophobic increase make easier the phase splitting, while the electrolyte capacity to induce phase separation follow the order: citrate>tartrate>succinate. The consistency of the tie-line data was ascertained by applying the Othmer–Tobias correlation. The experimental data were correlated with the NRTL model for the activity coefficient, with estimation of new interaction energy parameters. The results, analyzed in terms of root mean square deviations between experimental and calculated compositions, were considered satisfactory. [Copyright &y& Elsevier]

Abstract: Phase diagrams of two-phase systems (ATPS) composed by the triblock copolymer L64+organic salt (sodium tartrate, sodium succinate, sodium citrate, or ammonium citrate)+water, at different temperatures (278, 288, and 298K) are presented in this work. Contrary to behavior of ATPS formed by inorganic salts, the study of the temperature influence in the liquid–liquid equilibrium behavior of L64–organic salts ATPS showed an exothermic character for phase separation process. Microcalorimetric measurements showed that this phase separation energy is around −0.2kJmol−1 for all organic salts. The module of slope of tie line (STL) tends to increase with an increase in temperature. The cation nature effect showed that the salt Na3C6H5O7 was more effective in promoting phase separation than (NH4)3C6H5O7. The capacity of the different anions tested for inducing ATPS formation with L64 followed the order: C6H5O7 3− >C4H4O6 2− >C4H4O4 2−. Because the salt–L64 interaction energy to be very similar, the cation and anion effects on the phase separation could be attribute to a process driven by entropy. The interaction parameters of the NRTL and UNIFAC models were estimated through the experimental data of all ternary systems. The results of the NRTL (with 64 tie-lines) and UNIFAC (with 27 tie-lines) were considered excellent with global root mean square deviations, respectively, of the 1.04% and 0.87%. The consistencies of the all tie-line experimental compositions were improved by applying the Othmer–Tobias correlation. [Copyright &y& Elsevier]

Abstract: Partition of the natural dye carmine has been studied in aqueous two-phase systems prepared by mixing aqueous solutions of polymer or copolymer with aqueous salt solutions (Na2SO4 and Li2SO4). The carmine dye partition coefficient was investigated as a function of system pH, polymer molar mass, hydrophobicity, system tie-line length and nature of the electrolyte. It has been observed that the carmine partition coefficient is highly dependent on the electrolyte nature and pH of the system, reaching values as high as 300, indicating the high potential of the two-phase extraction with ATPS in the purification of carmine dye. The partition relative order was Li2SO4 ≫Na2SO4. Carmine molecules were concentrated in the polymer-rich phase, indicating an enthalpic specific interaction between carmine and the pseudopolycation, which is formed by cation adsorption along the macromolecule chain. When the enthalpic carmine–pseudopolycation interaction decreases, entropic forces dominate the natural dye-transfer process, and the carmine partitioning coefficient decreases. The optimization of the extraction process was obtained by a central composite face-centered (CCF) design. The CCF design was used to evaluate the influence of Li2SO4 and PEO 1500 concentration and of the pH on the partition coefficient of carmine. The conditions that maximize the partition of carmine into the top phase were determined to be high concentrations of PEO and Li2SO4 and low pH values within the ranges studied. [Copyright &y& Elsevier]

Abstract: The separation of Cd and Ni from Ni–Cd batteries using an aqueous two-phase system (ATPS) composed of copolymer L35, Li2SO4 and water is investigated. The extraction behavior of these metals from the bottom phase (BP) to the upper phase (UP) of the ATPS is affected by the amount of added extractant (potassium iodide), tie-line length (TLL), mass ratio between the phases of the ATPS, leaching and dilution factor of the battery samples. Maximum extraction of Cd (99.2±3.1)% and Ni (10.6±0.4)% is obtained when the batteries are leached with HCl, under the following conditions: 62.53% (w/w) TLL, concentration of KI equal to 50.00mmolkg−1, mass ratio of the phases equal to 0.5 and a dilution factor of battery samples of 35. This novel methodology is efficient to separate the metals in question, with the advantage of being environmentally safe, since water is the main constituent of the ATPS, which is prepared with recyclable and biodegradable compounds. [Copyright &y& Elsevier]

[Display omitted] β-Carotene (β C A R) is a pro-vitamin A carotenoid with powerful antioxidant properties. However, it has low aqueous solubility, light and heat stability, and bioavailability. An interesting strategy to improve β C A R incorporation in food matrices while preserving its properties is the use of proteins as nanocarriers. Lysozyme (LYS) is a protein capable of carrying bioactive molecules and has antitumor, antiviral, and antimicrobial activities. To enable the use of LYS with β C A R , it is important to understand the dynamics of LYS - β C A R binding. Here, a thermodynamic and kinetic investigation of LYS - β C A R ° complex formation at physiological pH was carried out using fluorescence spectroscopy (FS), differential scanning nanocalorimetry (nanoDSC), molecular docking, and surface plasmon resonance (SPR). The binding constants were found to be on the order of 105 to 103 L mol−1 by FS and SPR, respectively, revealing that the interaction between LYS and β C A R is entropically driven. In addition, kinetic parameters related to intermediate complex formation were obtained, and we found that the rate of intermediate complex formation was higher on the free molecules association than on the LYS - β C A R ° dissociation based on the lower Δ G a ‡ values than Δ G d ‡. In addition, the occurrence of an isokinetic relationship indicates that intermediate complex formation results in changes in LYS binding sites, and both desolvation of the free molecules and conformational changes are temperature dependent. Thus, we have elucidated the dynamics of LYS - β C A R ° complex formation and provided important evidence that LYS can be used to carry β C A R , which will improve its application and functionality in food. [ABSTRACT FROM AUTHOR]

Abstract: This work aimed to study the partition of cheese whey proteins α-lactoalbumin and β-lactoglobulin using aqueous two-phase system by applying the cloud point extraction technique. The cloud point temperatures were determined under different concentrations of copolymer and salt. The system providing the best protein separation conditions was 20mass% of copolymer PE61 and potassium phosphate salt solution of 100mM, at pH 7. The protein α-lactoalbumin remained preferentially in the aqueous phase and the β-lactoglobulin was transferred to the copolymer phase. [Copyright &y& Elsevier]