Activity In Aqueous Solution Research Articles

N-Doped Carbon Materials as Heterogeneous Catalysts for High Efficiency Isomerization Glucose to Fructose in Aqueous Media

Fructose is not only an important food and beverage ingredient, but also a renewable resource for production of bio-chemicals. In this paper, a series of N doped mesoporous carbon materials (MCNs) were prepared and evaluated as heterogeneous catalysts for catalytic isomerization of glucose to fructose. The MCNs were prepared through carbonization of p-phenylenediamine disulfate and the effects of desulfonation with NaOH and hydrogenation treatments were examined. It is found that the molar ratio of H2SO4/pPDA crucially affects the porous structure and the nitrogen content. Desulfonation with NaOH treatment could largely eliminate the sulfonic groups on the carbon edges and thus enhance the basicity of the MCN materials, whereas hydrogenation reduction could modify the N atom species and reinforce the strength of the basic sites, as a result enhancing the catalytic activities in glucose isomerization to fructose. Among all of the prepared MCN samples, MCN-2-DH showed an excellent activity in aqueous solution, which afforded a fructose yield of 31.6% with 84.6% selectivity.

Measurements and Correlation of Water Activity in Aqueous Solutions Containing Diphenhydramine-Hydrochloride Drug, (D+)-Galactose, (D−)-Fructose, (D+)-Lactose, and Sucrose at 298.15 K

Water activity in aqueous solutions containing diphenhydramine-hydrochloride, DPH-HCl, (D+)-galactose, (D−)-fructose, (D+)-lactose, and sucrose was measured using an improved isopiestic method at T...

Effect of diphenhydramine-hydrochloride, guaifenesin and naproxen sodium drugs on water activity in aqueous solutions of 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ionic liquid at 298.15 K

Water activities for the binary aqueous solution of ionic liquid of 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([BMP][TfO]), and also three ternary aqueous solutions containing ionic liquid of [BMP][TfO] and drugs of diphenhydramine-hydrochloride, guaifenesin and naproxen sodium were measured using an improved isopiestic method to study the medicines effect on water activity of ionic liquid aqueous solution at T = 298.15 K. Vapor pressure values were calculated from the water activity data measured in this work. NRTL, NRF-NRTL, mNRTL, Wilson and TNRF-mNRTL local composition based models were applied for correlating the water activity data for binary and ternary aqueous solutions containing ionic liquid and drugs considered in this work. All of these models satisfactorily predicted the water activity data for the systems investigated. Water activity data and vapor pressure decreasing were utilized to highlight the solute-solvent interactions.

Antioxidant properties of different pectin-containing solutions

At the present stage, the tasks of state policy is to preserve the functions of life support for the stable development of society, improving the health of the population, ensuring environmental safety of the country. Antioxidant activity is manifested in the ability of substances to delay the radical oxidation of organic and high-molecular compounds, and thereby reduce the yield of alcohols, hydroperoxides, fatty acids, aldehydes and ketones. Pectin substances are contained in all plants and some algae and are able to exhibit antioxidant activity. The article presents the study of antioxidant activity of pectin-containing solutions. To determine the antioxidant activity, aqueous solutions of pectin substances of Apple, citrus, beet pectin, their combinations with a concentration of 1% were prepared. According to the obtained data, the value of antioxidants for aqueous solutions of pectin substances and their combinations was calculated. According to the diagram of antioxidant activity of aqueous solutions of pectin substances and their combinations. An increase in antioxidant activity in the combination of Apple and citrus pectins with beet, which is explained by the influence of beet pectin on the properties of substances combined with it. Apple pectin does not increase antioxidant activity in combination with citrus pectin, due to its chemical and physiological form. The ability of pectins to show antioxidant activity depending on the combination of pectins is proved. It was found that the most antioxidant activity has an aqueous solution of beet pectin. Moreover, there is an increase in antioxidant activity when combining Apple and citrus pectins with beet, which is explained by the predominant effect of beet pectin on this indicator.

Insight into the Structure and Activity of Surface-Engineered Lipase Biofluids.

Despite a successful application of solvent-free liquid protein (biofluids) concept to a number of commercial enzymes, the technical advantages of enzyme biofluids as hyperthermal stable biocatalysts cannot be fully utilized as up to 90-99% of native activities are lost when enzymes were made into biofluids. With a two-step strategy (site-directed mutagenesis and synthesis of variant biofluids) on Bacillus subtilis lipase A (BsLA), we elucidated a strong dependency of structure and activity on the number and distribution of polymer surfactant binding sites on BsLA surface. Here, it is demonstrated that improved BsLA variants can be engineered via site-mutagenesis by a rational design, either with enhanced activity in aqueous solution in native form, or with improved physical property and increased activity in solvent-free system in the form of a protein liquid. This work answered some fundamental questions about the surface characteristics for construction of biofluids, useful for identifying new strategies for developing advantageous biocatalysts.

Highly efficient electrocatalysts for oxygen reduction reaction: Nitrogen-doped PtNiMo ternary alloys

The relatively low efficiency of the reaction of oxygen reduction (ORR) remains among the main obstacles for hydrogen fed proton exchange membrane fuel cells (H-PEMFCs) commercialization.In the present work, PtNiMo ternary alloy catalysts are obtained through reducing by NaBH4 and subsequent thermal annealing in NH3 at 1.0 atm. The as prepared catalysts are physico-chemically (XRD, TEM and XPS) characterized, exhibiting alloy nanostructure.From the electrochemical tests it is found that they exhibit high ORR activity in aqueous solutions saturated with O2 and acidified with HClO4. From the as synthesized catalysts, Pt3Ni3MoN/C shows the highest mass activity (539.41 mA mg−1 Pt); 3.5 times greater than that observed over commercial Pt/C (154.46 mA mg−1 Pt). Moreover, they show very good stability, while their ORR activity is only slightly altered after 5,000 cycles.These highly performing and low cost catalysts could thus open up new possibilities for the commercialization of hydrogen fed PEMFCs.

Amides as models to study the hydration of proteins and peptides — spectroscopic and theoretical approach on hydration in various temperatures

Interactions with water are one of the key factors which determine protein stability and activity in aqueous solutions. However, the protein hydration is still insufficiently understood. N-methylacetamide (NMA) is regarded as a minimal part of the peptide backbone and the relative simplicity of its structure makes it a good model for studies on protein–water interactions.In this paper, the influence of NMA and N,N-dimethylacetamide (DMA) on surrounding water molecules in a range of temperature (25–75 °C) is studied by means of the FTIR spectroscopy. The results of the difference HDO spectra method are compared with the results of theoretical DFT calculations of NMA and DMA aqueous complexes.Both NMA and DMA can be regarded as “structure-makers”, yet their hydration spheres are different. These molecules exhibit a mixed and mutually dependent types of hydration: hydrophilic and hydrophobic. In the case of a NMA molecule that has one methyl group less than DMA, the type of hydrophobic hydration is more important. The DMA hydration sphere is less stable: the interactions between water molecules around the methyl groups are strained. Moreover, the hydration of NMA is much more temperature dependant than in the case of DMA. The source of the differences may be hidden in the NH⋯H2O interaction.The delicate nature of water interactions with the peptide block models may be cautiously translated into the much more complicated interactions of proteins with their hydration shells.

Preparation, rheology, and film properties of polyacrylate latex using amphiphilic macroreversible addition‐fragmentation chain transfer agents as surfactants

ABSTRACTReversible addition‐fragmentation chain transfer (RAFT) radical emulsion polymerization of n‐butyl acrylate (nBA) and methyl methacrylate (MMA) was successfully performed in the presence of the amphiphilic macro‐RAFT agents poly(acrylic acid‐b‐styrene) (PAA‐PSt) trithiocarbonate. First, the amphiphilic macro‐RAFT agents PAA‐PSt were prepared and their surface activities in aqueous solutions were studied. Subsequently, the effects of pH values of the latexes and degree of polymerization (DP) of the PAA hydrophilic segments in the amphiphilic macro‐RAFT agents on the latex particle size and molecular weight of the polyacrylate products, as well as the rheological properties of the latexes, surface morphology, and water resistance of the latex films were investigated in detail. It was found that the rheological behaviors of the as‐prepared latexes can be tuned by adjusting solid content, temperature, pH value, and DP of the hydrophilic segments, respectively, due to their effects on particle packing, hydrophobic association, hydration layer, and hydrodynamics volume. In addition, atomic force microscopy (AFM) was applied to investigate the surface morphology, and the results demonstrated that the surface phase separation and roughness of the latex films changed with the latex pH values and DP of the hydrophilic segments. Finally, the films with good water resistance were obtained by directly casting the as‐prepared polyacrylate latexes at room temperature. Our study indicated that employing amphiphilic macro‐RAFT agents to prepare polyacrylate latexes with well‐defined chemical compositions and structures is a facile and environmentally friendly strategy, which would have wide potential application in coatings, inks, adhesives and thickening agents, and so on. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47463.

Composite materials based on active carbon/TiO2 for photocatalytic water purification

The present work describes the preparations of active carbon (AC) – titania composites with different AC/TiO2 ratio, their characterization using XRD, BET and SEM and evaluation of adsorption capacity and photocatalytic activity in aqueous solution using azo-dye Acid Orange 7 (AO7). Composite materials based on AC/TiO2 were prepared from commercial active carbon (1737 m2 g-1) and TiO2 (P25, 45 m2 g-1) materials by the mixing method. The studied parameters were the ratio of AC/TiO2, hydrothermal treatment and milling of as-prepared composites.The composites show increased BET surface area proportional to the content of AC in the material. The disappearance of AO7 is due to the combination of two processes, e. g. adsorption and photocatalytic oxidation which take place in parallel. Thus the overall removal of AO7 has been corrected on adsorption (measured in dark) to obtain the rate of AO7 disappearance due to photocatalytic oxidation (PO). The optimum ratio of AC/TiO2 was found to be 0.23 where PO rate is only slightly lower than that for P25 and overall AO7 removal is twice higher than for P25 itself. The less intensive (low-frequency) milling of the composite results in the decrease of carbon particle size, increase in AO7 adsorption and decline in the PO of AO7. More intensive milling (high-frequency) results in the decrease of the anatase content, appearance of the small amount of brookite and almost negligible PO rate of AO7. Irradiation of low-frequency milled AC/TiO2 composite in aqueous suspensions resulted in the generation of a comparable concentration of hydroxyl radical spin-adduct (DMPO−OH) as non-milled composite, high-frequency milled composite revealed substantially lower DMPO−OH concentration which can be explained by the increased concentration of carbon-centered radicals in AC acting as scavengers of photogenerated electrons.

Point-of-care Ratiometric Fluorescence Imaging of Tissue for the Diagnosis of Ovarian Cancer.

During a minimally invasive tumor resection procedure, it is still a challenge to rapidly and accurately trace tiny malignant tumors in real time. Fluorescent molecular imaging is considered an efficient method of localizing tumors during surgery due to its high sensitivity and biosafety. On the basis of the fact that γ-glutamyltranspeptidase (GGT) is overexpressed in ovarian cancer, we herein designed a highly sensitive ratiometric fluorescent GGT-responsive probe Py-GSH for rapid tumor detection.Methods: The GGT response probe (Py-GSH) was constructed by using GSH group as a response group and pyrionin B as a fluorescent reporter. Py-GSH was characterized for photophysical properties, response speed and selectivity of GGT and response mechanism. The anti-interference ability of ratiometric probe Py-GSH to probe concentration and excitation power was evaluated both in vitro and in tissue. The biocompatibility and toxicity of the ratiometric probe was examined using cytoxicity test. The GGT levels in different lines of cells were determined by ratiometric fluorescence imaging and cytometry analysis.Results: The obtained probe capable to rapidly monitored GGT activity in aqueous solution with 170-fold ratio change. By ratiometric fluorescence imaging, the probe Py-GSH was also successfully used to detect high GGT activity in solid tumor tissues and small peritoneal metastatic tumors (~1 mm in diameter) in a mouse model. In particular, this probe was further used to determine whether the tissue margin following clinical ovarian cancer surgery contained tumor.Conclusion: In combination of ratiometric fluorescence probes with imaging instrument, a point-of-care imaging method was developed and may be used for surgical navigation and rapid diagnosis of tumor tissue during clinical tumor resection.

Chlorhexidine Digluconate Formulations Used for Skin Antisepsis

Aims: The representativeness of European standards phase 2, step 1 regarding bactericidal and yeasticidal activities was used for the comparison of two marketed antiseptic solutions, one containing chlorhexidine digluconate (0.5%) and the other combining chlorhexidine digluconate (0.25%), benzalkonium chloride (0.025%) and benzylic alcohol (4%). Methods: The bactericidal activity of the antiseptic solutions used pure or diluted was assessed according to the European standards NF EN 13727 and NF EN 13624 for the bactericidal and yeasticidal activity respectively. The contact time was 1 min at 20°C. Interfering substances used correspond to soiling conditions i.e. bovine serum albumin and sheep erythrocytes. A reduction of colony-forming units by ≥5 log10 was deemed to meet the requirements to conclude bactericidal activity and ≥4 log10 for yeasticidal activity. Results: Regarding all the mandatory strains, both solutions are bactericidal and yeasticidal even after a 40% dilution and even under “dirty” conditions. Conclusions: The present study demonstrated the efficient bactericidal and yeasticidal activity of aqueous solutions containing chlorhexidine digluconate either alone at a concentration of 0.5% (w/v) or at a concentration of 0.25% (w/v) when combined with benzalkonium chloride at 0.025% (w/v) and benzylic alcohol 4%. These results have to be considered regarding the respective formulations and potent allergy risks.

Aggregation properties and toxicity of newly synthesized thiazolium based surfactants – Thermodynamic and computational study

Two new thiazolium-based surfactants namely N-dodecylthiazolium bromide, [NddTz][Br] and N-dodecyl-4-methylthiazolium bromide, [4mNddTz][Br], were synthesized and investigated as new surface active and antimicrobial agents. Their thermal stability is determined by TG/DSC measurements, and the self-assembly behaviour in aqueous solutions systematically studied applying experimental and molecular dynamics (MD) approach. Obtained results of surface tension and electrical conductivity showed that both newly synthesized salts possess a similar surface activity in aqueous solutions compared to imidazolium-based surface active N-dodecyl-3-methylimidazolium bromide, [NddmIm][Br], ionic liquid. Also, thermodynamic parameters of micellization are calculated and compared with the results obtained by volumetric measurements. Antimicrobial activity of these salts is tested by microdilution method on Gram-positive and Gram-negative bacteria and yeasts. In vitro cytotoxicity study has been performed using human fetal lung fibroblasts (MRC-5) and colon adenocarcinoma (HT-29) cell line.

Synthesis and properties of double-chain single-head acetamidinium bicarbonate switchable surfactants

A series of switchable surfactants with double hydrophobic chains and a single hydrophilic head N,N’-dialkylacetamidinium bicarbonate with an alkyl length between diC8 and diC12 were synthesized by using new approaches. The structures of acetamidinium bicarbonate were characterized by 1 H NMR and ESI-MS spectroscopy. The surface activity in aqueous solution of N,N’-dialkylacetamidinium bicarbonate and N’-alkyl-N,N-dimethylacetamidinium were compared by surface tension methods. Some surface activity parameters were studied, such as cmc, γcmc, pC20, cmc/C20, Γmax, and Amin. The results indicated that double-chain surfactant was superior to single-chain surfactant and showed more excellent surface activity. The switchability was confirmed by monitoring the conductivity of a solution of amidine in ethanol and their effect in emulsion stability was also investigated.

Antibacterial behaviors of Cu2O particles with controllable morphologies in acrylic coatings

Biofouling, a global issue, exerts an adverse impact on ocean shipping, deep-sea exploration, aquaculture and other industries. The addition of Cu2O particles to coatings is the most popular and effective method used for biofouling resistance in the ocean circumstance. Herein, Cu2O particles with three kinds of morphologies, including cube, sphere and cubooctahedron, were fabricated by liquid phase reducing method. Particle size, crystallinity, component, activity in aqueous solution, antibacterial property and copper ion leaching rate were systematically investigated. XRD and XPS jointly reflected that as-prepared Cu2O particles were highly pure and impurity was absent. Among three kinds of Cu2O particles, cubooctahedron Cu2O was the most active, possessed the highest ion leaching rate and exhibited the best antibacterial property. It could be deduced that morphology of Cu2O particles affected its activity in aqueous solution, then impacted release rate and ultimately influenced antibacterial capacity. Morphology and component of bacteria, before and after being exposed to as-synthesized Cu2O-acrylic hybrid coatings were also studied and results proved that copper ion was prone to do a damage to the cell membrane of E.coli rather than B. subtilis because of the difference between cell walls.

Size and shape effect on the photocatalytic efficiency of TiO2 brookite

Thanks to aqueous sol–gel chemistry, it is now possible to prepare several phase pure TiO2 brookite colloidal systems that significantly differ on nanoparticles size and shape. This TiO2 polymorph is more difficult to be obtained as phase pure material than anatase or rutile. Here we have prepared a set of four different sol–gel brookite syntheses with particles size ranging from 10 to 500 nm and significantly different morphologies as demonstrated by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. We have studied their photocatalytic activities in aqueous solution on phenol and formic acid. The brookite sample with higher specific surface displays better activity for both pollutants abatement than anatase and rutile reference samples and very close to the TiO2 P25 commercial reference. Additional experimental characterization of photogenerated charge carriers and their lifetime is performed using time-resolved microwave conductivity. We could then explain why another efficient brookite material is able to compensate a significantly lower specific surface with a higher photon conversion rate. This study involving a broad set of pure phase brookite samples brings back that phase into the TiO2 polymorphs race for light-enhanced applications. It confirms that size/shape–activity correlation already observed for the anatase polymorph is also valid for the brookite phase.

Influence of growth medium composition on the incorporation of boron in HPHT diamond

Influence of growth medium composition on the efficiency of boron doping of carbonado-like diamond at 8–9GPa was studied by diluting the C-B growth system with metallic solvents of carbon, Co and Ni. Addition of these metals to the original system leads to a decrease in the synthesis temperature, degree of doping with boron and suppression of superconductivity in diamond. According to XPS analysis, content of substitutional boron is equal to 0.07, 0.16 and 0.39at.% in diamonds obtained in Co-C-B, Ni-C-B and C-B growth systems, respectively. Metallic behavior at normal temperatures and superconductivity below 5K in diamond, synthesized in C-B system, change to semiconducting character of conductivity down to 2K in diamonds obtained in the diluted systems; a faint hint of superconducting transition at 2K was detected in the case of diamond grown in Ni-C-B system. By comparing phase composition of the inclusions and the doping efficiency of the diamonds, we are able to suggest that high chemical affinity of boron to boride-forming metals hinders the boron doping of diamond. The heavily boron-doped carbonado-like diamond compacts demonstrate high electrochemical activity in aqueous solutions and can be used as miniature electrodes in electrosynthesis and electroanalysis.

Three tetrasiloxane-tailed cationic gemini surfactants: The effect of different spacer rigidity on surface properties and aggregation behaviors

Gemini cationic surfactant with tetrasiloxane-tailed has potential to improve performance and biocompatibility in a range of applications. With different rigidity spacers, structure effects on their self-assembling behavior and interface properties are obvious. Hence, it should be possible to tune system surface properties and aggregation morphology in aqueous solution by changing rigidity of spacers. A series of novel cationic tetrasiloxane Gemini surfactants MR8M, MDM, MDOM were designed and synthesized by a simple process. Their surface property, hydrolysis resistance ability, wetting ability, aggregation behavior as well as antibacterial activity in aqueous solutions were studied. These three surfactants exhibited high hydrolysis resistance in both acidic and neutral aqueous solutions. On one hand, surface tension of MR8M (γCMC = 19 mN/m) and MDOM (γCMC = 23 mN/m), significantly lower than C8-PSi-C8 (γCMC = 37 mN/m) with siloxane spacer and pure hydrocarbon equivalents. On the other hand, MR8M can wet the highly hydrophobic PTEF plate completely at low concentration (0.4 mM). In addition, different aggregations, MDM with only vesicle, MDOM with spherical micelle and vesicle micelle and MR8M spherical micelle, wormlike micelle and vesicle were observed to assemble. Moreover, the antibacterial activity of these surfactants increased as the rigidity of spacer increased and MDM exhibited best antibacterial activity.

Significant Enhancement of Structural Stability of the Hyperhalophilic ADH from Haloferax volcanii via Entrapment on Metal Organic Framework Support.

The use of an in situ immobilization procedure for the immobilization of hyperhalophilic alcohol dehydrogenase in a metal organic framework material is described. The easy and rapid in situ immobilization process enables retention of activity over a broad range of pH and temperature together with a decrease in the halophilicity of the enzyme. The catalytic activity of the immobilized enzyme was studied in nonaqueous solvent mixtures with the highest retention of activity in aqueous solutions of methanol and acetonitrile. The approach demonstrates that this immobilization method can be extended to hyperhalophilic enzymes with enhancements in activity and stability.

Measurement and Modeling of Isobaric Vapor–Liquid Equilibrium of Water + Glycols

We present new experimental data on the isobaric vapor–liquid equilibria (VLE) of four binary mixtures of water with ethylene glycol, diethylene glycol, triethylene glycol, or tetraethylene glycol, measured at three different system pressures (0.05, 0.07, and 0.1 MPa). Water activity coefficients were estimated from the mixtures boiling temperatures and used to rationalize the effect of the increasing glycols chain length on the molecular interactions with water. The soft statistical associating fluid theory (SAFT) equation of state was used to describe the experimental VLE data of these highly nonideal systems, providing insights into the molecular interactions leading the macroscopic behavior of the mixtures. Glycols and water were both modeled as associating molecules, with models and parameters from previous works, in a transferable manner. Soft-SAFT accurately reproduces the experimental data using one single, state independent, binary interaction parameter to correct the mixtures dispersive energy. It is further shown that the parametrization obtained from the pure glycols can be used to provide accurate predictions of the water activities in aqueous solutions of PEGs of higher molecular weight (600–6000 g/mol) highlighting the soft-SAFT robustness and the soundness of the parametrization used.

Multifunctional Poly‐N‐Isopropylacrylamide/DNAzyme Microgels as Highly Efficient and Recyclable Catalysts for Biosensing

AbstractThe development of highly efficient, recyclable, and multifunctional biocatalysts is of great importance for various applications, especially in biosensing. In this study, highly catalytic and recyclable DNAzyme functionalized poly‐N‐isopropylacrylamide (pNIPAM) microgels are prepared via one‐step precipitation polymerization. The pNIPAM/DNAzyme microgels exhibit highly catalytic activities in aqueous solution at room temperature, and become hydrophobic and separable from the reaction mixture at temperature higher than the lower critical solution temperature of pNIPAM, which facilitate the recyclable utilization of these catalysts. Different kinds of DNAzyme functionalized catalytic microgels can be facilely prepared via the one‐step synthesis procedure. Two typical catalytic DNA structures, the Mg2+‐dependent DNAzyme and the hemin‐G‐quadruplex horseradish peroxidase (HRP)‐mimicking DNAzyme, are chosen as model systems to validate the feasibility. These pNIPAM/DNAzyme microgel catalysts maintain 80% to 91% initial catalytic activity after eight times of catalysis recycling. Furthermore, the pNIPAM microgels by themselves provide additional interfaces to capturing an enzyme, glucose oxidase, which can cascade with the linked HRP mimicking DNAzymes, to form recyclable bi‐enzyme cascading system for the sensing of glucose.