Aqueous Ethanol Mixtures Research Articles

Solubility measurement, calculation, solvent effect and preferential solvation of fenoxaprop-p-ethyl in four cosolvent mixtures at (278.15–323.15) K

Equilibrium solubility of fenoxaprop-p-ethyl in aqueous mixtures of ethanol/ isopropanol/acetonitrile/N,N-dimethylformamide (DMF) plus water was experimentally measured by isothermal saturation method at (278.15–323.15) K under 101.2 kPa. The order of solubility (mole fraction) of fenoxaprop-p-ethyl in pure solvents from high to low is 4.233 × 10−2 (DMF 323.15 K) > 2.044 × 10−2 (acetonitrile 323.15 K) > 7.727 × 10−3 (isopropanol 323.15 K) > 5.338 × 10−3 (ethanol 323.15 K) > 2.565 × 10−5 (water 323.15 K). Experimental results showed that temperature and type of solvent were decisive factors for the dissolution of fenoxaprop-p-ethyl. The content of fenoxaprop-p-ethyl in solution was analyzed by high-performance liquid chromatography (HPLC). Moreover, the solubility data of fenoxaprop-p-ethyl was correlated by Jouyban-Acree (J-A) model, van’t Hoff-Jouyban-Acree (V-J-A) model and Apelblat-Jouyban-Acree (A-J-A) model. The maximum of root-mean-square deviation (RMSD), relative average deviation (RAD) and standard deviation (SD) predicted via three thermodynamic models were 1.78 × 10−4 (DMF + water), 2.87 × 10−2 (acetonitrile + water) and 1.79 × 10−4 (DMF + water), respectively. In addition, the solvent effect between solute and solvent molecules was deduced by KAT-LSER model and the result showed that dipolarity/polarizability interactions between the solute and solvent molecules were dominant in the dissolution of fenoxaprop-p-ethyl. Finally, the preferential solvation parameter (δx1,3) of fenoxaprop-p-ethyl was obtained by the method of inverse Kirkwood–Buff integrals and the preferential dissolution behavior of each concentration range is explained by Lewis acid base theory. However, for acetonitrile + water, the change of δx1,3 may be due to the polarization effects and it is not suitable for Lewis acid base theory.

A Simple Generic Model of Elastin-Like Polypeptides with Proline Isomerization.

A generic model of elastin-like polypeptides (ELP) is derived that includes proline isomerization (ProI). As a case study, conformational transition of a -[valine-proline-glycine-valine-glycine]- sequence is investigated in aqueous ethanol mixtures. While the non-bonded interactions are based on the Lennard-Jones (LJ) parameters, the effect of ProI is incorporated by tuning the intramolecular 3- and 4-body interactions known from the underlying all-atom simulations into the generic model. One of the key advantages of such a minimalistic model is that it readily decouples the effects of geometry and the monomer-solvent interactions due to the presence of ProI, thus gives a clearer microscopic picture that is otherwise rather nontrivial within the all-atom setups. These results are consistent with the available all-atom and experimental data. The model derived here may pave the way to investigate large scale self-assembly of ELPs or biomimetic polymers ingeneral.

Mathematical modeling of concentration influence on evaporative convection in a bilayer system of binary mixtures

A problem of evaporative buoyancy-thermocapillary convection in a two-phase system of binary media is studied. Characteristics of a joint steady flow of evaporating fluid and gas in a narrow plane horizontal channel are analyzed on the example of aqueous ethanol solution and mixture of the nitrogen with the ethanol vapor. The influence of solutal effects related to changes in the ethanol concentration in the liquid mixture is scrutinized. New exact solution of thermosolutal convection equations is constructed in the framework of a two-sided model based on the Oberbeck–Boussinesque approximation. The model used implies the presence of the liquid–gas interface admitting evaporation where surface phenomena play a key role. The testing of problem statements is performed in order to determine feasible closing relations. A correct problem statement is proposed that provides acceptable accordance with known experimental data concerning both the working liquid properties and possible pattern of the bilayer flows. Non-linear character of dependence of evaporation rate on the concentration of the aqueous solution is established. The solution predicts the decrease in evaporation rate due to the diffusion resistance effect for some compositions of the liquid mixture, thereby it is shown the possibility of control of the heat exchange parameter by means of the choice of the working fluid compound. The results obtained can be useful under developing the experimental methods for exploration of the interfacial effects in multicomponent fluids.

The non-ideality in binary aqueous systems contributed to the different abilities of solvent entities incorporated in the solvation shell of methylene blue

The solvatochromic properties of methylene blue (MB) were investigated in neat water, methanol, ethanol, propanol, dioxane and their corresponding aqueous mixtures. The correlation of the empirical solvent polarity scale (ET) values of MB with solvent composition was analysed using the solvent exchange model of Bosch and Roses to explain the preferential solvation of the probe thiazine dye in the binary mixed solvents. Non-linear solvatochromism of MB was observed in aqueous mixtures of methanol, ethanol, propanol and dioxane. The influence of the composition of the solvating shell in preferential solvation of the solute dye was investigated in terms of both solvent?solvent and solute?solvent interactions, and the local mole fraction of each solvent composition in the cybotactic region of the probe was also calculated. Effective mole fraction variation can provide important physicochemical insights into the microscopic and molecular interactions between MB species and solvent components. The results showed that the MB solvation shell was thoroughly saturated with the solvent complex S12 for dioxane more than ethanol and propanol mixtures, and opposite trends for methanol mixtures, whereas the solvent complex S12 could not incorporate into the MB solvation shell. Data from the binary systems were analysed with KAT parameters using a dual model of basicity and polarity. The results showed that the polarity was better suited for spectral shift in aqueous methanol and ethanol solutions, while the basicity was better for aqueous propanol and dioxane solutions.

The dissolution mechanism, molecular dynamics simulation and thermodynamic analysis of nirmatrelvir (treatment of COVID-19) in aqueous ethanol mixtures

This research investigates the cosolvent effect of nirmatrelvir (treatment of COVID-19) in ethanol + water mixtures. The result shows that the maximum solubility in mole fraction is 8.313 × 10−2 at the ethanol mass fraction of 80%, which is greater than that in pure water. The solvent effect analysis indicates that the hydrogen bond acidity (HBA) of solvent has the greatest impact on the solubility of nirmatrelvir solubility. The negative preferential solvation values in water-rich regions indicate that nirmatrelvir molecules are preferentially solvated by water molecules. With the rising mass fraction of cosolvent, ethanol disrupts the ordered structure of water molecules in solution through hydrogen bonding, allowing nirmatrelvir molecules to be preferentially solvated by ethanol. Nonetheless, nirmatrelvir molecules are preferentially solvated by water again in ethanol-rich regions. Through molecular dynamics calculations (MD), it could be found that the dissolution behavior is consistent with its calculated by solvation free energy calculation. Furthermore, the tall and sharp peak of the RDF plots of O···H-O (ethanol/water) and N-H···O (ethanol/water) were attained at 1.50–2.50 Å, indicating that ethanol and water molecules form a regular and definite coordination sphere around the nirmatrelvir moiety at the distance of 1.50–2.50 Å through hydrogen bonding form. Additionally, the correlation fitting was performed for the solubility data through the Jouyban-Acree model and its derivative models. Moreover, “Apparent thermodynamic analysis” of nirmatrelvir dissolution process in aqueous ethanol mixtures including entropy, enthalpy and Gibbs free energy were completed.

Solubility of Salicylic Acid in Some (Ethanol + Water) Mixtures at Different Temperatures: Determination, Correlation, Thermodynamics and Preferential Solvation

Equilibrium mole fraction solubility of salicylic acid in nine aqueous-ethanolic mixtures, as well as in neat water and neat ethanol, was determined at seven temperatures from T = (293.15 to 323.15) K. Salicylic acid solubility in these mixtures was adequately correlated with well-known correlation/prediction methods based on Jouyban-Acree model. Apparent thermodynamic quantities, i.e. Gibbs energy, enthalpy, and entropy, for the dissolution and mixing processes, were computed by means of the van’t Hoff and Gibbs equations. The enthalpy–entropy compensation plot of enthalpy vs. Gibbs energy of dissolution was not linear exhibiting positive slopes from neat water to the mixture of w1 = 0.30 and from the mixture of w1 = 0.50 to neat ethanol indicating enthalpy-driven drug transfer processes but negative in the interval of 0.30 < w1 < 0.50 indicating entropy-driven drug transfer processes from more polar to less polar solvent systems. Moreover, by using the inverse Kirkwood–Buff integrals it is observed that salicylic acid is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in those mixtures of 0.24 < x1 < 1.00.

Solubility enhancement of atorvastatin calcium and ethanol-mediated transition with some surfactants

ABSTRACT Atorvastatin calcium (ATC) is a class II BCS blockbuster synthetic cholesterol-lowering drug. The aim of this work is to examine the solubility of ATC in ethanol and water mixtures at room temperature and to study the effect of various concentrations of Tween 80 and benzalkonium chloride (BAC) on drug solubility in aqueous mixtures of ethanol. ATC shows maximum solubility in ethanol + water mixtures at a ratio of w1 = 0.7 ethanol. The addition of a surfactant changed the drug solubility profile relative to the surfactant type and its concentration. XRD and DSC results indicate that a high concentration of BAC may induce the formation of ATC solvate which influenced the melting point and solubility of the drug. Surfactant type and concentration influence the morphology, nucleation, and growth of drug crystals. A high concentration of BAC accelerates crystal habits and its relative growth rate while Tween 80 slows its growth rate.

Analysis of protonation equilibria of some alanyl dipeptides in water and aqueous ethanol mixtures.

The protonation constants are one of the most fundamental properties of biological molecules. The determination of the constants of the dipeptide is interesting and necessary for a full understanding of its activities in biological process. In this study, the protonation constants of some aliphatic alanine dipeptides (alanyl-alanine, alanyl-phenylalanine, alanyl-valine, alanyl-leucine, and alanyl-methionine) were studied in water and ethanol-water mixtures (20%ethanol-80%water;40%ethanol-60%water;60%ethanol-40%water, (v/v)) at 25 ± 0.1°C under nitrogen atmosphere and ionic strength at 0.10mol L-1 by potentiometry. The constants of the systems were calculated using Best computer program. The effects of the different amino acids bound to the alanine on the acidity of the alanyl dipeptides were investigated. The constants were influenced by changes in solvent composition and their variations were discussed in terms of solvent and structural properties.

Solubility of ammonium metal fluorides in aqueous ethanol mixtures - implications for scandium recovery by antisolvent crystallization.

The recovery of scandium from waste streams of other mining and metallurgical processing industries is gaining research interest due to the scarcity of scandium-containing ores. Hydrometallurgical techniques such as leaching, solvent extraction and crystallization amongst others have been successfully applied to recover scandium salts from such waste streams. Scandium can be recovered as (NH4)3ScF6 by antisolvent crystallization from NH4F strip liquors obtained after solvent extraction. The coextraction of metal impurities such as Fe, Al, Zr and Ti causes contamination of the final solid product. The extent of coprecipitation of ammonium metal fluorides depends on their initial concentration in the strip liquor and their solubility in the NH4F-antisolvent mixtures. Here, the solubility of ammonium metal fluorides of Sc, Zr, Fe, Al and Ti is reported separately in 3 mol L-1 NH4F-ethanol mixtures at 25 °C as well as in a system containing all five solid phases. The solubility of (NH4)3ZrF7 is slightly higher than that of (NH4)3ScF6, while the solubilities of (NH4)3FeF6 and (NH4)3AlF6 are significantly lower in comparison to (NH4)3ScF6. The solubility of (NH4)2TiF6 is 1-2 orders of magnitude higher than those of other ammonium metal fluorides. When a mixture of ammonium metal fluoride salts is dissolved in the same 3 mol L-1 NH4F-ethanol mixture as for the individual salts, the resultant solubility of the ammonium metal fluorides of Sc, Zr and Fe decreases significantly, while the resultant solubility of ammonium aluminum hexafluoride increases. This is likely due to changes in solution speciation with increased NH4F concentration and ionic strength.

Artichoke By-Products Valorization for Phenols-Enriched Fresh Egg Pasta: A Sustainable Food Design Project

More healthy and sustainable food are nowadays desirable to improve human health and protect the planet’s resources. From this perspective, the aim of this study is to investigate artichoke (Cynara scolymus L.) by-products as a potential source of phenolic compounds and to use these compounds to design new fresh egg pasta formulation. Sustainable extraction was carried out using ultrasound-assisted extraction (UAE) and chemometric techniques, such as the Response Surface Methodology (RSM). UAE process parameters (temperature and time) and solvent composition (ethanol aqueous mixtures) were optimized using a three-level Box–Behnken design, in order to carry out the maximum yield in phenols. Under the optimal conditions (temperature: 60 °C; time: 60 min; solvent: 50% ethanol:water), the amount of phenolics (TPC) was 22.4 ± 0.2 mg GAE g−1 d.w., characterized mainly by dicaffeoylquinic acid (32.8 ± 0.6 mg CAE g−1 d.w.) and chlorogenic acid (14.1 ± 0.2 mg CAE g−1 d.w.). Hence, the polyphenols extract was used as an ingredient to design a new formulation of functional fresh egg pasta. Four recipes with soft wheat and semolina (P1 and P2) and with soft wheat alone (P3 and P4) were prepared. Compared with control pastas (P1 and P3), the enriched ones (P2 and P4) showed a higher polyphenol content, especially for P4 (1.86 ± 0.03 mg GAE g−1 d.w. for P1, 2.05 ± 0.02 mg GAE g−1 d.w. for P2, 1.92 ± 0.03 mg GAE g−1 d.w. for P3, 2.04 ± 0.02 mg GAE g−1 d.w. for P4). A high decrease in TPC was observed as a result of the cooking process, especially for the two control formulations (−71% for P1 and −70% for P3) in comparison with P2 (−64%) and P4 (−55%). At last, to assess the antimicrobial effect of artichoke by-products on fresh pasta and to monitor its spoilage, we used image analysis. Corresponding to a higher TPC content, P2 and P4 showed an extended shelf life of 16% and 33%, respectively, probably due to the antioxidant activity of artichoke. The new fresh egg pasta enriched with polyphenols extracted from artichoke by-products showed very good nutritional and technological characteristics, even after cooking, confirming the good potentiality of artichoke by-products in the design of new, healthy, and sustainable food products.

Solubility measurement, thermodynamic modeling and solubility parameters of Clarithromycin（form ӀӀ）in aqueous ethanolic solution

ABSTRACT To develop and optimise the crystallisation process of clarithromycin, the solid–liquid equilibrium solubility and solvent effect of clarithromycin form ӀӀ in aqueous ethanol mixtures was experimentally determined at the temperature range from 273.15 K to 333.15 K under atmospheric pressure of 0.1 MPa. Experimental results confirmed that the crystal form did not change during the determination of solubility. The results indicated that the solubility of clarithromycin is dependent on the composition of the mixed solvent, and it reaches its maximum value when the mole fraction of ethanol in the mixture solvent is equal to 0.61. In addition, the solubility of clarithromycin was positively related to the temperature in the ethanol-water mixed solvent. Furthermore, solubility parameter was used to elucidate the relation between the solubility and the mixed solvent. The modified Apelblat equation, van’t Hoff equation, λh equation, CNIBS/R–K model and Jouyban–Acree model were employed to correlate the solubility data. The correlation results showed good agreement with the experimental data, the modified Apelblat equation provides the best correlation results. The NRTL equation was utilised to calculate the thermodynamic properties of the dissolution process of clarithromycin, and the dissolution process of clarithromycin was estimated to be endothermic and entropy-driven.

Expanding the Equilibrium Solubility and Dissolution Thermodynamics of Benzoic Acid in Aqueous Alcoholic Mixtures

The equilibrium solubility of benzoic acid in water and ethanol, as well as in nine {ethanol (1) + water (2)} mixtures, was determined from T = (293.15 to 323.15) K. Benzoic acid mole fraction solubility in these aqueous-ethanolic mixtures was adequately correlated with some well-known correlation/prediction models, obtaining mean percentage deviations of 2.2 to 7.6%. Apparent thermodynamic quantities, namely, Gibbs energy, enthalpy, and entropy, for the dissolution, mixing and solvation processes, were computed by means of the van ’t Hoff and Gibbs equations. The enthalpy–entropy compensation plot of apparent enthalpy vs. apparent Gibbs energy of dissolution was not linear, indicating enthalpy and entropy mechanisms for transfer. Ultimately, by using the inverse Kirkwood–Buff integrals, it is observed that benzoic acid is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in those {ethanol (1) + water (2)} mixtures of 0.24 &lt; x1 &lt; 1.00.

Preferential solvation of 5,7-dihydroxyflavone (chrysin) in aqueous co-solvent mixtures of methanol and ethanol

ABSTRACT The inverse Kirkwood-Buff integrals were used to calculate the preferential solvation parameters of the natural polyphenolic compound chrysin in binary mixtures of ethanol (1) + water (2) and methanol (1) + water (2) as a function of their thermodynamic properties. At temperatures between 298.15 K and 318.15 K, chrysin is extremely sensitive to specific solvation effects; therefore, the negative values of were found in the water-rich range of 0 < x1 < 0.30 for methanol (1) + water (2) and 0 < x1 < 0.25 for ethanol (1) + water (2) which suggested that water (2) preferentially dissolves chrysin (3). In co-solvent-rich regions, the values of were positive, and the co-solvents preferentially dissolve chrysin (3). The solvation of drugs in water-rich mixtures is likely to be facilitated by hydrophobic hydration around aromatic rings or groups.

Recent advances in sodium alginate‐based membranes for dehydration of aqueous ethanol through pervaporation

AbstractSodium alginate (SA) is a progressive material for membrane fabrication. The technological development of SA‐based membranes has made a significant contribution to the separation techniques, especially in aqueous organic solutions. The outstanding performance of SA is attributed to its outstanding structural flexibility and hydrophilicity. In view of structural characteristics, SA membranes have immense utilization in the pervaporation separation of organics. Among various organics, dehydration of aqueous ethanol is employed as a standard to check the success of pervaporation (PV) membrane. Because ethanol and water have comparable molecular sizes, thus difficult to extract water from aqueous ethanol mixtures than it is for other organics. A literature survey shows that wide‐ranging data are available on the PV performance of SA and its modified membranes. In this context, the present review addresses the recent advances made in SA membranes for enhanced ethanol dehydration performance during the last decade. Available data since 2010 has been compiled for grafted, crosslinked, blend, mixed matrix, and composite hybrid sodium alginate membranes in terms of separation factor, permeation flux, and pervaporation separation index PSI. The data are assessed with reference to the effect of feed composition, membrane selectivity, flux, and swelling behavior.

PHOTOCATALYTIC ACTIVITY OF MESOPOROUS TiO2 (ANATAS) IN THE REACTION OF HYDROGEN RELEASE FROM AQUEOUS-ETHANOLIC MIXTURE

Samples of mesoporous nanocrystalline titanium dioxide (anatase with a crystallite size of about 10 nm) were obtained by a modified sol-gel method in the presence of a template of dibenzo-18-crown-6 and small additives of surfactant (dodecylmethylethylammonium bromide) or ions of lanthanum (III) in butyl alcohol in combination with hydrothermal treatment at 175 °C for 24 hours followed by calcination in air at 500 °C for 4 hours. The photocatalytic activity of the obtained TiO2 samples was investigated in a model reaction of the photocatalytic release of H2 from an aqueous-ethanol mixture. It was found that in all cases the use of hydrothermal treatment significantly increases the photoactivity of the obtained sample, which in some cases is more than 3-4 times higher than the corresponding characteristic for commercial photocatalyst Evonik P25. The key effect of hydrothermal treatment on the increase of photoactivity of the samples is probably the consequence of a drastic increase in the treated samples of pore volume and diameter, as well as a decrease in the size of anatase crystallites. These changes (along with a significant increase in the specific surface area) are greater for samples obtained in the presence of La3+ ions. It is shown that samples of TiO2 microspheres obtained at the same concentrations of reagents in the reaction mixture show slightly higher photocatalytic activity than the corresponding lanthanum-stabilized samples of mesoporous TiO2 powders (micrometer-scale particles are not formed in the presence of lanthanum (III) ions). However, with an increasing concentration of reagents in the reaction mixture, the photocatalytic activity has the sample containing lanthanum. Probably, this can be explained by the high textural characteristics of the TiO2 sample in combination with the peculiarities of its morphology - the formation of secondary nanoparticles of agglomerated formations and the influence of La3+ ions. It is worth noting that the photocatalytic activity of TiO2 samples prepared in the presence of La3+ ions reduces as their specific surface area decreases.

Ionic liquids and deep eutectic solvents as sustainable alternatives for efficient extraction of phenolic compounds from mate leaves

Mate leaves are highly appreciated in south and central America as food ingredient for tea preparation. Their nutritional importance, due to their high content of polyphenols and other nutraceuticals, has been drawing attention worldwide, especially to produce extracts and biopharmaceuticals. However, the extraction of such nutraceuticals using conventional processes/solvents might impact their profile/concentration. Ionic liquids (ILs) and deep eutectic solvents (DES) have been recognized as green solvents, and more recently the naturally-derived have stood out. In this work, we investigated the use of bioethanol, cholinium chloride ([Ch]Cl), Ch-based DES and less expensive protic ILs derived from acetic acid, in aqueous systems at different concentrations, as potential sustainable alternatives over conventional solvents and more expensive aprotic ILs for the extraction of polyphenols from mate leaves. Simply adding the [Ch]Cl in aqueous-ethanolic mixtures at 50% improved extraction efficiency (∼35 mg/g) in comparison to conventional solvents (∼7–29 mg/g). However, IL (∼41–66 mg/g) and DES (∼47–55 mg/g) systems presented better performance, being the former presenting the best results at 75% (∼66 mg/g). The extraction yield was also related to water concentration, which is interesting to reduce viscosity and IL/DES cost for a more cost-efficient extraction and was also supported by results obtained using COSMO-SAC. Therefore, the low-cost protic IL and DES are promising sustainable solvent alternatives over conventional solvents/ILs for extraction of polyphenols from mate leaves.

Optimization of Phenolic Compound Extraction from Brewers’ Spent Grain Using Ultrasound Technologies Coupled with Response Surface Methodology

Brewers’ spent grain (BSG) is the main solid by-product from the brewery industry, rich in valuable nutrients and bioactive compounds. The aim of this study was to valorize this by-product, recovering phenolic compounds from BSG using ultrasound-assisted extraction (UAE) and chemometric techniques, such as the response surface methodology (RSM). Therefore, UAE process parameters (temperature and time) and solvent composition (ethanol aqueous mixtures) were optimized using a three-level Box–Behnken design, in order to carry out the maximum yield in phenols. Then, the extract obtained under optimal conditions was characterized for the total phenolic content and antioxidant capacity (2,20-azino-bis(3-ethylbenothiazoline-6-sulphonic acid, ABTS, and 2,2-diphenyl-1-picrylhydrazyl, DPPH), and individual phenolic compounds were identified using HPLC-DAD. The results show the highest level of total soluble phenolic content (4.1 ± 0.1 mg GAE/g d.w.) at 80 °C, 50 min and 65:35% ethanol:water, with a high goodness of fit between experimental and predicted values (R2 = 0.987), and a high antioxidant potential (DPPH: 0.42 ± 0.01 mg TE eq/g d.w.; ABTS: 5.82 ± 0.04 mg TE eq/g d.w.). A comparison between the classic extraction techniques and the UAE with the same solvent showed an increase of 156% in the phenol yield. The characterization of phenolic profile revealed that ferulic acid (1.5 ± 0.2 mg/L), vanillic acid (0.78 ± 0.18 mg/L) and p-coumaric acid (0.12 ± 0.03 mg/L) were the prevalent ones. UAE coupled with RSM was a useful tool to inexpensively and quickly recover bioactive phenolic compounds from BSG, which can be used in the food, pharmaceutical or cosmetic industries.

Excess Molar Volumes, Apparent Molar Volumes, Partial Molar Volumes of Methionine, An Amino Acid, in Water + Ethanol And Water + Methanol Solutions at 298.15 K

Methionine is an amino acid that is extremely important for human health. To better understand the biochemical events occurring in the human body, the excess molar properties of methionine and aqueous ethanol and aqueous methanol mixtures were determined at 298.15 K. Interactions between components in solutions are explained. Negative deviations from the ideal state have been observed in methionine solutions due to hydrogen bonds, dipole interactions, charge-transfer interactions.

The Effects of Proline Isomerization on the Solvation Behavior of Elastin-Like Polypeptides in Water-Ethanol Mixtures.

Elastin-like polypeptides (ELPs) are well-known proline-rich stimulus-responsive polymers. They have broad applications ranging from drug delivery to green chemistry. Recently, the authors have shown that the cis/trans proline isomerization can be used to regulate their conformational behavior while keeping the lower critical solution temperature (LCST) unchanged in pure water. In aqueous ethanol mixtures, ELPs typically exhibit an expanded-collapsed-expanded transition known as the co-non-solvency phenomenon. Since it is unclear how proline isomerization affects the solvation behavior of ELPs in aqueous ethanol mixtures, an all-atom insight on single ELPs has been provided to address this question. It is found that if all proline residues are in the cis state, the peptides only experience a collapsed-expanded transition as ethanol concentration increases, i.e., the initial collapse vanishes because cis isomers prefer the compact structures in pure water. The data from the authors also suggest that proline isomerization does not change the shift in solvation free energy of an ELP with given sequence, but it varies the affinity of the peptide to both the solvent and cosolventmolecules.

Extraction of Bioactive Compounds from Ulva lactuca

Macroalgae Ulva lactuca, has been employed as a natural source for the production of extracts with potent bioactivity. The biochemical characterization showed that the macroalgae biomass contains a remarkable amount of the polysaccharide Ulvan (49.9 wt%) which is a valuable chemical compound well known for its benefits in human health. Four nontoxic solvents, water, ethyl acetate, ethanol, and an ethanol/water mixture (70:30 v/v) were examined for their recovery efficiency of total carotenoid and phenolic contents. Experimental results showed that the aqueous mixture of ethanol was the most efficient solvent in the recovery of bioactive compounds with extraction yield of 10–15% dw. The effect of extraction parameters, namely time, temperature, and the ratio of biomass to solvent, on the carotenoid and phenolic compounds’ content, antioxidant activity, and extraction yield, was investigated, using the ethanol/water mixture as a solvent. The extract obtained under 60 °C, 3 h of extraction time and 1:10 biomass to solvent mass ratio showed the highest antioxidant activity. This extract maintained its antioxidant capacity almost stable for five days of storage under cool and dark conditions. Finally, specific phenolic and carotenoid compounds in the U. lactuca extracts were identified using the High-Performance Liquid Chromatography (HPLC) technique.