Ultrasonic Velocities,Densities, and Refractive Indices of Binary Mixtures of Polyethylene Glycol 250 Dimethyl Ether with 1-Propanol and with 1-Butanol

Measurements of the ultrasonic velocity (u), density (ρ) and refractive index (n) for binary mixtures of polyethylene glycol 250 dimethyl ether with 1-propanol and 1-butanol have been made at three temperatures (T=293, 303 and 31 K) over the entire composition range in order to investigate the nature of intermolecular interactions between the components of these liquid mixtures. Various excess thermodynamic properties such as the excess ultrasonic velocity (Δu), deviation in isentropic compressibility (Δk _S ), excess intermolecular free length (L_f^E)(L_{\mathrm{f}}^{\mathrm{E}}), excess acoustic impedance (Z ^E), excess pseudo-Grüneisen parameter (Γ ^E), and molar refraction deviation (ΔR _m) were calculated using experimental values of the ultrasonic velocity, density and refractive index and were then represented with the Redlich-Kister polynomial equation. The observed excess deviation parameter values were explained on the basis of the strength of intermolecular interactions between the components of the mixtures. Estimations of the refractive index and ultrasonic velocity have also been made using various empirical relations and are discussed in terms of the average percentage deviations (APD).     

Volumetric Properties of Aqueous Solutions of L-Glutamic Acid and Magnesium-L-Glutamate

Densities of aqueous solutions of L-glutamic acid and magnesium-L-glutamate were determined from T=288.15 to 333.15 K at 5 K temperature intervals. The measured densities were used to evaluate the apparent molar volumes, V _2,φ (m,T), the cubic expansion coefficients, α(m,T), and the changes of isobaric heat capacities with respect to pressure, (∂ C _p /∂ p) _T,m . They were qualitatively correlated with changes in the structure of water that occur when L-glutamic acid or magnesium-L-glutamate are present.     

Partial Molar Volumes of Uracil,Thymine, Adenine in Water and of Adenine in Aqueous Solutions of Uracil and Thymine

The partial molar volumes of uracil, thymine and adenine in water and adenine in aqueous solutions of uracil and thymine, at fixed composition, were determined over a range of temperatures. The partial molar volumes of adenine in aqueous uracil and thymine are less than in pure water.     

Synthesis Characterization and Viscosity Studies of Homopolymer of Methyl Methacrylate and Copolymer of Methyl Methacrylate and Styrene

A homopolymer of methyl methacrylate (MMA) and its copolymer with styrene at different compositions were synthesized and characterized. Viscosity measurements of the synthesized homopolymer and the copolymers in toluene solutions were performed at 313 K. Different equations were used to calculate the intrinsic viscosity, viscometric constants values, and molecular weight of the synthesized polymers. The values of intrinsic viscosity and viscosity average molecular weight obtained by the two methods (single point determination and graphical extrapolation) were compared in order to verify the validity of the single point determination for the polymers. Viscometric properties derived included the specific viscosity (it determines the contribution of the solute to the viscosity of the solution), the reduced viscosity (that provides a measure of the polymer capacity for increasing the solution viscosity), and the intrinsic viscosity.     

Stability and Coordination Mode of Complexes of Polyphosphates and Polymetaphosphates with Copper(II) Ions in Aqueous Solution—Potentiometric,Spectral and Theoretical Studies

Complexes of copper(II) with a number of polyphosphate and polymetaphosphate anions have been studied in aqueous solutions by potentiometric, spectroscopic and theoretical methods. Stability constants of the complexes have been determined as well as their coordination modes. Results of the equilibrium studies provided evidence for the formation of ML, MHL and ML(OH) _x type complexes with the ligands studied. The length of the polyphosphate chain was found to affect the oxygen atom charge that is reflected in the stability constants of the ML type complexes. Moreover, the stability of the complex is also influenced by the spatial arrangement of the phosphate groups in phosphates and metaphosphates. The spectral parameters observed for certain complexes have permitted us to deduce the inner coordination sphere of the studied complexes.     

The Enthalpies of Solution of L-cysteine, L-serine and L-asparagine in Aqueous Solutions of Some Alcohols at 298.15 K

Heats of solution, Δ_sol H _m , of L-cysteine, L-serine and L-asparagine amino acids have been measured at different concentrations of aqueous ethanol, propanol and 2-propanol at 298.15 K using solvation calorimetry. These data are compared with the results reported earlier for L-alanine in ethanol. The enthalpic coefficients, h _xy , of the solute-organic cosolvent pair interaction in water have been obtained from the McMillan-Mayer approach and the data have been interpreted in terms of various interactions and changes in solvent structure.     

Viscosity of Aqueous Solutions of Lithium,Sodium, Potassium,Rubidium and Caesium Cyclohexylsulfamates from 293.15 to 323.15 K

The viscosities of aqueous solutions of lithium, sodium, potassium, rubidium and caesium cyclohexylsulfamates were measured at 293.15, 298.15, 303.15, 313.15 and 323.15 K. The relative viscosity data were analyzed and interpreted in terms of the Kaminsky equation, η _r=1+Ac ^1/2+Bc+Dc ². The viscosity A-coefficient was calculated from the Falkenhagen-Dole theory. The viscosity B-coefficients are positive and relatively large. Their temperature coefficient ∂ B/∂ T is negative or near zero for lithium and sodium salts whereas for potassium, rubidium and caesium salts it is positive. The viscosity D-coefficient is positive. This was explained by the size of the ions, structural solute–solute interactions, hydrodynamic effect, and by higher terms of the long-range Debye-Hückel type of forces. From the viscosity B-coefficients the thermodynamic functions of activation of viscous flow were calculated. The limiting partial molar Gibbs energy of activation of viscous flow of the solute was divided into contributions due to solvent molecules and the solute in the transition state. The activation energy of the solvent molecules was calculated using the limiting Gibbs energy of activation for the conductance of the solute ions. The activation energy of the solvent molecules was then discussed in terms of the nature of the alkali-metal ions and their influence on the structure of water. The limiting activation entropy and enthalpy of the solute for activation of viscous flow were interpreted by ion-solvent bond formation or breaking in the transition state of the solvent. The hydration numbers of the investigated electrolytes were calculated from the specific viscosity of the solutions.     

Mitochondria-targeted theranostic nanoparticles for optical sensing of oxygen,photodynamic cancer therapy,and assessment of therapeutic efficacy

We report on a novel kind of mitochondria-targeted theranostic nanoparticles (NPs). The NPs are doped with the oxygen-sensitive probe Pt(II)-porphyrins (PtTFPP) which exerts a dual role in acting as a diagnostic tool that can sense oxygen via quenching of luminescence, but also acts as an agent in photodynamic therapy (PDT) of cancer. In addition, it allows therapeutic efficacy to be assessed in-situ. Upon appropriate high-energy photoirradiation, the NPs generate singlet oxygen by energy transfer from triplet PtTFPP to ground state oxygen, and cell death is induced via PDT. Under low-energy light irradiation, in contrast, the NPs can be utilized to detect oxygen consumption rate via time-resolved luminescence measurements in order to study the efficacy of PDT. This is the first report where a single nanoagent is used to stimulate PDT and also to assess the efficacy of PDT. In our perception, the method provides a promising platform for testing anti-cancer drugs.

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Graphical abstract We report on a kind of mitochondria-targeted theranostic nanoparticles (NPs) doped with Pt(II)-porphyrins for oxygen sensing via quenching of luminescence, efficient photodynamic therapy (PDT) of cancer and quantitative assessment of therapeutic response in-situ.

     

Measurement of Magnesium Stability Constants of Biologically Relevant Ligands by Simultaneous Use of pH and Ion-Selective Electrodes

Simultaneous measurements with magnesium ion-selective and pH glass electrodes have been used for determination of the stability constants of magnesium ions with various biologically relevant ligands by alkalimetric titration under physiological conditions (37^○C, I=0.15 mol⋅dm⁻³). New systems were investigated: magnesium with pyroglutamate, pyridoxine and HEPES, along with citrate, lactate, glycinate, aspartate and glutamate. For comparison, calcium stability constants with the same ligands were determined similarly, using calcium ion-selective and pH glass electrodes. Ligand protonation constants, necessary for the calculation of the metal complex formation constants, were also determined.     

Effects of a non-ionic surfactant,Tween 20, on adsorption/desorption of saccharification enzymes onto/from lignocelluloses and saccharification rate

In this work, we examined the role of a non-ionic surfactant, Tween 20, on enzymatic hydrolysis of lignocelluloses. Delignified lignocelluloses (pine wood chip) were used as model substrates. Effects of Tween 20 on adsorption/desorption onto/from lignocelluloses with and without hydrolysis were evaluated respectively. Tween 20 lowered the non-biospecific adsorption of β-glucosidase and enhanced the bio-specific adsorption of cellulase. Tween 20 did not affect the liquid phase reaction (cellobiose hydrolysis). However, for the solid surface reaction (cellulose hydrolysis), cellulose conversion for 72 hrs was increased 9–21% and 1–8.5% for samples with high lignin contents (PI) and low lignin contents (PIII) by injection of Tween 20 (0.024–0.24 mM), respectively. Moreover, Tween 20 increased the cellulose conversion rate substantially. It is suggested that the increase of cellulase amount adsorbed due to the increase of effective cellulose surface by Tween 20 contribute to the enhancement of cellulose conversion.     

Molecularly imprinted adsorbents for preconcentration and isolation of progesterone and testosterone by solid phase extraction combined with HPLC

The use of a novel procedure of solid-phase extraction with molecularly imprinted polymers (MISPE) has been described. A MISPE procedure relying on tailor-made, artificial-mimic materials capable of selectively rebinding target analytes (steroids) based on a combination of recognition mechanisms, such as size, shape and functionality, was custom designed for progesterone and testosterone. The combination of MISPE with LC/DAD is a simple and an efficient method for the determination and quality control of progesterone and testosterone in human urine samples.     

Adsorption properties of BEA zeolites and their aluminum phosphate extrudates for purification of isomaltose

The disaccharide isomaltose is produced via an enzymatic reaction and is adsorbed to BEA zeolite. This reaction integrated adsorption can be achieved as fluidized bed as well as fixed bed. We investigated isotherms, adsorption enthalpies and sorption kinetics of BEA zeolite and extrudates with a novel aluminum phosphate sintermatrix. These extrudates contain 50% (w/w) of BEA 150 zeolites (Si/Al = 75) as primary crystals. BET-surface for extrudates is 245 m²⋅g⁻¹ and 487 m²⋅g⁻¹ for zeolite. Extrudates show a monomodal macropore structure with a maximum at 90 nm. All isotherms show a type I shape. For lower equilibrium concentrations, which occur during the enzymatic reaction, Henry’s law is applied and compared to a Langmuir model. Adsorption equilibrium constant K _i,L calculated from Langmuir for extrudates at 4 °C is 64.7 mL⋅g⁻¹ and more than twice as high as obtained from Henry’s law with K _i is 26.8 mL⋅g⁻¹. Adsorption on extrudates at 4 °C is much stronger than on zeolite crystals where the Henry coefficient K _i is 17.1 mL⋅g⁻¹. Adsorption enthalpy Δh _Ad calculated from van’t Hoff plot with the Henry equation is −44.3 kJ⋅mol⁻¹ for extrudates and −29.6 kJ⋅mol⁻¹ for zeolite crystals. Finally, the kinetics for ad- and desorption were calculated from the initial slope. The diffusion rate for ad- and desorption on extrudates were in the same range while adsorption on zeolites is three orders of magnitudes faster than desorption.     

Adsorption of toluene, methylcyclohexane and neopentane on silica MCM-41

Adsorption-desorption isotherms of toluene, methylcyclohexane and neopentane were determined on a silica MCM-41 material of pore diameter ∼3.4 nm over the temperature range 258 K to 308 K (278 K for neopentane). The isosteric enthalpies of adsorption were determined from the isotherms at the various temperatures. It was found that the isotherms of toluene and methylcyclohexane have a similar variation with the temperature, exhibiting hysteresis at 268 K and at lower temperature, while the adsorption of neopentane is reversible at all temperatures. The three organic adsorptives interact differently with the silica surface and the isosteric enthalpies of adsorption indicated that methylcyclohexane has the weakest interaction and toluene the strongest. A slight increase in the adsorption enthalpy at the beginning of the capillary condensation step is observed with methylcyclohexane and neopentane but not with toluene.     

Temperature Dependence of Physical Properties of Imidazolium Based Ionic Liquids: Internal Pressure and Molar Refraction

Density, speed of sound and refractive index of the imidazolium-based ionic liquids (ILs), 1-methyl-3-octylimidazolium chloride [C₈mim][Cl], 1-butyl-3-methylimidazolium methyl sulfate [C₄mim][C₁OSO₃], and 1-butyl-3-methylimidazolium octyl sulfate [C₄mim][C₈OSO₃], have been measured in the temperature range from 283.15 to 343.15 K. Experimental density and speed of sound have been used to calculate the internal pressure p _i of the ILs. The p _i values were found to be higher than those of water and molecular organic liquids, but lower than those of classical molten salts. We also calculated molar refraction R _M from the measured refractive index n _D in the temperature range from 288.15 to 343.15 K. Refractive indices of ILs were also higher than those of normal organic liquids, but comparable to long-chain hydrocarbon organic solvents. The structure-property correlation of the ILs has been discussed and the results have been compared to our earlier studies (Kumar in J. Solution Chem. 37:203–214, 2008).     

Synthesis,structural characterization,and in vitro antimicrobial properties of salicylate and pyrazoline complexes of bismuth(III)

Displacement reactions of dichlorobismuth(III)pyrazolinates with oxygen donors such as sodium salicylate and acetate in 1?:?1 and 1?:?2 molar ratio in refluxing anhydrous benzene yields (C₁₂H₁₅N₂OX)Bi(C₆H₄O₃), (CH₃COO)BiCl(C₁₅H₁₂N₂OX), and (CH₃COO)₂Bi(C₁₅H₁₂N₂OX) [C₁₂H₁₅N₂OX?=?3(2′-hydroxyphenyl)-5-(4-X-substituted phenyl) pyrazoline X?=?H in 1,5,9, CH₃ in 2,6,10, OCH₃ in 3,7,11, and Cl in 4,8,12, respectively, (C₆H₄O₃)?=?salicylate and (CH₃COO)?=?acetate]. Newly synthesized derivatives are brown solids, soluble in organic solvents like benzene, chloroform, and acetone. The compounds have been characterized by elemental analyses (C, H, N, Cl, and Bi), molecular weight measurements, and spectral (IR, ¹H NMR, ¹³C NMR) studies. The (C₁₂H₁₅N₂OX) and (C₆H₄O₃) are bidentate while (CH₃COO) is monodentate to bismuth(III), leading to a distorted trigonal bipyramidal structure. The complexes were screened against different bacteria and fungi showing potential antibacterial and antifungal activities.     

Effect of Ionic Strength and Temperature on the Protonation of Oxidized Glutathione

The protonation constants for oxidized glutathione, H _i−1L^(4−i+1)−, K _i ^H=[H _i L⁽⁴⁻ⁱ⁾⁻]/[H _i−1L^(4−i+1)−][H⁺] i=1,2,…,6 have been measured at 5, 25 and 45 °C as a function of the ionic strength (0.1 to 5.4 mol⋅[kg(H₂O)]⁻¹) in NaCl solutions. The effect of ionic strength on the measured protonation constants has been used to determine the thermodynamic values (K _i ^H0) and the enthalpy (ΔH _i ) for the dissociation reaction using the SIT model and Pitzer equations. The SIT (ε) and Pitzer parameters (β ⁽⁰⁾, β ⁽¹⁾ and C) for the dissociation products (L⁴⁻, HL³⁻, H₂L²⁻, H₃L⁻, H₄L, H₅L⁺, H₆L²⁺) have been determined as a function of temperature. These results can be used to examine the effect of ionic strength and temperature on glutathione in aqueous solutions with NaCl as the major component (body fluids, seawater and brines).     

Thermal and quality evaluation of vegetable oils used in ruminant feed

Dairies add fat supplements to the diets of small ruminants to increase energy production and consequently the production and quality nutritional and sensorial of the milk. This study investigated the thermal and oxidative stability of babassu, castor, faveleira, and sesame oils by TG/DTA and PDSC. The profile of the fatty oils studied was determined by GC–MS as well as physicochemical characteristics. The thermogravimetric profile of the oils indicated that mass loss was caused by the decomposition or volatility of the triacylglycerides. Faveleira and sesame oils showed a high percentage of polyunsaturated fatty acids, especially C18:2. From a nutritional standpoint, unsaturated oils are more suitable supplements for animals because they promote biochemical changes beneficial to human health.     

Densities and Excess Molar Volumes of Binary and Ternary Mixtures Containing Acetonitrile + Acetophenone + 1,2-Pentanediol: Experimental Data,Correlation and Prediction by PFP Theory and ERAS Model

Densities were determined experimentally over the entire range of composition at 298.15 K for the ternary system acetonitrile (1) + acetophenone (2) + 1,2-pentanediol (3) and for the three corresponding binary systems. Excess molar volumes were calculated for the binary and the ternary systems. These results were fitted to variable-degree polynomials. Further, the Prigogine-Flory-Patterson (PFP) theory and Extended Real Associated Solution (ERAS) model were applied to V_m^EV_{m}^{\mathrm{E}} for the binary mixtures of acetonitrile + acetophenone, acetonitrile + 1,2-pentanediol and acetophenone + 1,2-pentanediol, and the findings compared with the experimental results.     

Enthalpies of Dilution of N,N′-hexamethylenebisacetamide in Pure Water and Aqueous Solutions of Alkali Halide at 298.15 K

Enthalpies of dilution of N,N′-hexamethylenebisacetamide in water and aqueous alkali halide solutions at the concentration of 0.150 mol⋅kg⁻¹ (approximately the concentration of physiological saline) have been determined by isothermal titration microcalorimetry at 298.15 K. The enthalpic interaction coefficients in the solutions have been calculated according to the excess enthalpy concept based on the calorimetric data. The values of enthalpic pair-wise interaction coefficients (h ₂) of the solute in aqueous solutions of different salts were discussed in terms of the different alkali salt ions and weak interactions of the diluted component with coexistent species as well as the change in solvent structure caused by ions.