Antioxidant effects of dihydroquercetin and rutin in peroxidase reactions catalyzed by cytochrome <Emphasis Type="Italic">c</Emphasis>

The combination of cytochrome c (Cyt c) and cardiolipin is known to catalyze free radical oxidation of membrane lipids, thereby triggering the cascade of reactions that lead to programmed cell death (apoptosis). It was interesting to estimate the possibility of controlling this reaction with the use of inhibitors of free radical reactions (antioxidants). The effects of bovine heart cardiolipin (BCL) and synthetic 1,1′,2,2′-tetraoleyl cardiolipin (TOCL) on the Cyt c peroxidase activity detected by luminol-enhanced chemiluminescence (CL) were studied. The CL amplitude substantially increased in the presence of TOCL and BCL in the ranges of the cardiolipin to Cyt c molar ratios from 0 to 30 and from 0 to 50, respectively, and insignificantly increased upon further increase in these ratios to 640: 1 and 320: 1. This dependence of the CL amplitude on the cardiolipin to protein ratio may have been accounted for by saturation of the protein surface with cardiolipin molecules reached at a certain molar ratio. The effects of the antioxidants rutin and dihydroquercetin (DHQ) on the peroxidase activity of Cyt c in combination with BCL was studied in the presence of the CL activator coumarine C-525 at a BCL to Cyt c molar ratio of 32: 1. In both cases, the peroxidase activity decreased as the antioxidant content of the system increased. A 50% inhibition of the reaction was observed at DHQ and rutin concentrations of 10 and 3 μM, respectively. It is supposed that the use of antioxidants will make it possible to control the formation of lipid radicals on membrane-bound Cyt c, which is the key stage of apoptosis.     

Enantioselective hydrogen transfer hydrogenation on rhodium colloid systems with optically active stabilizers

Hydrogen transfer hydrogenation of acetophenone and methyl benzoylformate with 2-propanol was studied on colloidal systems obtained by reduction of rhodium complexes in the presence of optically active compounds: chiral diamines, quaternary salt (4S,5S)-(–)-N¹,N⁴-dibenzylene-2,3-dihydroxy-N¹,N¹,N⁴,N⁴-tetramethylbutane-1,4-diammonium dichloride and (8S,9R)-(–)-cinchonidine. The increase in the molar ratio modifier/Rh leads to the increase in the enantioneric excess (ee) of the reaction products. The largest ee [43.8% of (R)-1-phenylethanol and 58.2% of methyl ester of (R)-mandelic acid] were achieved for the ratios (8S,9R)-(–)-cinchonadine: Rh = 9: 1 and 3: 1, respectively. The catalyst was characterized by the high-resolution transmission electron microscopy, X-ray diffraction analysis, and thermal analysis.     

Elucidating the Effect of Glycerol Concentration and C/N Ratio on Lipid Production Using <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> SKY7

The high demand for renewable energy and increased biodiesel production lead to the surplus availability of crude glycerol. Due to the above reason, the bio-based value addition of crude glycerol into various bioproducts is investigated; among them, microbial lipids are attractive. The present study was dedicated to find the optimal glycerol concentration and carbon/nitrogen (C/N) ratio to produce maximum lipid using Yarrowia lipolytica SKY7. The glycerol concentration (34.4 to168.2 g/L) and C/N ratio (25 to 150) were selected to investigate to maximize the lipid production. Initial glycerol concentration 112.5 g/L, C/N molar ratio of 100, and with 5 % v/v inoculum supplementation were found to be optimum for biomass and lipid production. Based on the above optimal parameters, lipid concentration of 43.8 % w/w with a biomass concentration of 14.8 g/L was achieved. In the case of glycerol concentration, the maximum Yp/s (0.192 g/g); Yx/s (0.43 g/g) was noted when the initial glycerol concentration was 112.5 g/L with C/N molar ratio 100 and inoculum volume 5 % v/v. The glycerol uptake was also noted to increase with the increase in glycerol concentration. At low C/N ratio, the glycerol consumption was found to be high (79.43 g/L on C/N 25) whereas the glycerol consumption was observed to decrease when the C/N ratio was raised to 150 (40.8 g/L).     

Determination of thermal to epithermal neutron flux ratio (f), epithermal neutron flux shape factor (α) and comparator factor (F<Subscript>c</Subscript>) in the Triga Mark II reactor,Malaysia

The thermal to epithermal neutron flux ratio (f or Ø _th /Ø _e ), epithermal neutron flux shape factor (α) and comparator factor (F _c ) are essential parameters when calculating the concentration of sample using k ₀-standardization method in the neutron activation analysis (NAA). The work was performed in the Triga Mark II reactor of Malaysian Institute for Nuclear Technology Research (MINT) using Au/Zr monitor couple. Twenty channels in the reactor have been evaluated and the corresponding thermal to epithermal neutron flux ratios (f) ranged from 11.69 to 47.89. The epithermal neutron flux shape factors (α) were found in the range of ?1.50·10^?1 to 1.59·10^?1 and the comparator factors (F _c ) were calculated within the range of 9.85·10³ to 6.70·10⁴. These results allowed us to study the neutron flux distribution more precisely and established the goodness of fit for k ₀-NAA.     

Poly(<Emphasis Type="Italic">β</Emphasis>-cyclodextrin)-mediated polylactide-cholesterol stereocomplex micelles for controlled drug delivery

A series of host-guest interaction-adjusted polylactide stereocomplex micelles was prepared via the self-assembly of 4-armed poly(ethylene glycol)-block-poly(L-lactide/D-lactide)-cholesterol (4-armed PEG-b-PLLA/PDLA-CHOL) and poly(β-cyclodextrin) (PCD) with the molar ratios of CHOL/β-CD at 1:0.5, 1:1, and 1:2 in an aqueous environment. The hydrodynamic diameters of the micelles ranged from 84.1 nm to 107 nm depending on the molar ratio of CHOL/β-CD. It was shown that the micelle with the largest proportion of PCD possessed excellent abilities in drug release, cell internalization as well as proliferation inhibitory effect toward human A549 lung cancer cells. The results demonstrated that the stereocomplex and host-guest interactions-mediated PLA micelles exhibited great potential in sustained drug delivery.     

Copolymer of lactide and ε-caprolactone catalyzed by bimetallic Schiff base aluminum complexes

A series of copolymers of lactide(LA) and e-caprolactone(ε-CL) with different monomer feed ratios were achieved using three kinds of bimetallic Schiff aluminum complexes as catalysts. The ratios of LA and ε-CL units in different copolymers and the average segments length were determined by NMR analysis. The comparative kinetic study of L-LA/ε-CL and rac-LA/ε-CL copolymerization systems showed that the polymerization rate of LA was faster than ε-CL, and L-LA showed polymerization rate slightly faster than rac-LA. It was inferred that the copolymers achieved by these complexes were gradient copolymers with gradual change in distribution of LA and e-CL units. The thermal properties of these copolymers were characterized by DSC analysis, which showed that the glass transition temperature(Tg) of these copolymers changed regularly according to the pro-portion change of two structural units.     

Semicontinuous microemulsion copolymerization of vinyl acetate and butyl acrylate: high solid content and effect of monomer addition rate

Vinyl acetate and butyl acrylate were copolymerized in microemulsion under monomer-starved conditions by a semicontinuous process using different monomer addition rates (R _a). A mixture of sodium dodecyl sulfate and polyethylene glycol dodecyl ether (Brij®35) were used as surfactants. Potassium persulfate was the initiator. High copolymer content latexes (around 40 wt.%), average particle diameters (D _p)?M _w) between 180,000 and 760,000. D _p and M _w of the copolymers decrease as R _a is decreased. As R _a increases, a shoulder in the molar mass distribution was observed at high values of M _w, which was ascribed to chain transfer to polymer. Homogeneous copolymer compositions were observed throughout the reaction, which cannot be obtained by the usual batch process.     

Teicoplanin-functionalized magnetic beads for detection of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> via inhibition of the luminol chemiluminescence by intracellular catalase

An affinity-based protocol is described for the detection of Staphylococcus aureus (S. aureus). It is utilizing teicoplanin-functionalized magnetic beads as carriers. Teicoplanin, which binds to the walls of cells of S. aureus via five hydrogen bonds, acts as the recognition agent. Captured S. aureus is magnetically separated from the sample matrix and then specifically lysed by lysostaphin which cleaves the cross-linking pentaglycine bridges of peptidoglycan in the cell wall. Lastly, S. aureus is quantified via the inhibitory effect of released intracellular catalase on a chemiluminescent (CL) system composed of peroxidase, luminol, H₂O₂ and p-iodophenol because catalase decomposes H₂O₂. S. aureus can be detected with CL response in the 140 to 1.4?×?10⁷ CFU·mL^?1 concentration range and a detection limit as low as 47 CFU·mL^?1 at a signal-to-noise ratio of 3. The method was evaluated by analyzing spiked samples including milk, human urine and saline injection solutions. The reliability was demonstrated by a recovery test and by comparison with a conventional plate counting method.

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Graphical abstract An antibiotic-affinity protocol is developed to detect Staphylococcus aureus (S. aureus) by utilizing teicoplanin-functionalized magnetic beads (Teic-MBs) as carriers. S. aureus can be quantified by measuring the inhibition of luminol chemiluminescence (CL) signal by intracellular catalase.

     

Solution Thermodynamics of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis><Superscript>/</Superscript>-Ethylenebis-(salicylideneiminato)-diaquochromium(III) Chloride in Aqueous Dimethylsulphoxide

The densities, viscosities and refractive indices of N,N ^/-ethylene-bis(salicylideneiminato)-diaquochromium(III) chloride, [Cr(salen)(H₂O)₂]Cl, in aqueous dimethylsulfoxide (DMSO) with different mass fractions (w ₂ = 0.20, 0.40, 0.60, 0.80 and 1.00) of DMSO were determined at 298.15, 308.15 and 318.15 K under atmospheric pressure. From measured densities, viscosities and refractive indices the apparent molar volumes (V _φ ), standard partial molar volume (V _φ ⁰ ), the slope (S _V ^* ), standard isobaric partial molar expansibility (φ _E ⁰ ) and its temperature dependence (?φ _E ⁰ /?T) _p , the viscosity B-coefficient, its temperature dependence (?B/?T), solvation number (S _n ) and apparent molar refractivity (R _D ^φ ), etc., were calculated and discussed on the basis of ion–ion and ion–solvent interactions. These results revealed that the solutions are characterized by ion–solvent interactions rather than by ion–ion interactions and the complex behaves as a long range structure maker. Thermodynamics of viscous flow was discussed in terms of transition state theory.     

Specific Refractive Index Increment (∂<Emphasis Type="Italic">n</Emphasis>/∂<Emphasis Type="Italic">c</Emphasis>) of Polymers at 660 nm and 690 nm

The specific refractive index increment (?n/?c) is an essential datum for the accurate quantitation of molar mass averages and distributions (inter alia) of macromolecules when refractometry, static light scattering, and/or viscometry detection are coupled on-line to size-based separation techniques. The latter include methods such as size-exclusion and hydrodynamic chromatography, and asymmetric and hollow-fiber flow field-flow fractionation. The ?n/?c is also needed for accurate determination of the weight-average molar mass of polymers by off-line, batch-mode multi-angle static light scattering. However, not only does ?n/?c differ among chemical species, it also depends on experimental conditions such as solvent, temperature, and wavelength. For the last 17 years, the author’s laboratories have measured the ?n/?c of a variety of natural and synthetic polymers, at both 690 nm and, more recently, 660 nm, under a variety of solvent and temperature conditions. In all cases, this has been done by off-line, batch-mode differential refractometry, not by assuming 100% analyte column recovery and 100% accurate peak integration. Results of these determinations are presented here, along with the relevant experimental data.     

Unexpected reactions of dichloro(ethyl)silane with DMSO in organic solvents

The effect of the solvent nature on the composition of the products formed upon the reaction between EtSi(H)Cl₂ and DMSO (molar ratio 1: 1, 0 °C) was revealed. This reaction in non-polar and low polar solvents (toluene, chloroform) gives oligoethyl(hydro)cyclo-siloxanes ((EtSi(H)O) _n , n = 3—8) as the major products in the yields up to 77%. In MeCN, oligoethyl(hydro)cyclosiloxanes are formed along with cyclic monochlorinated siloxanes ((EtSi(H)O) _n (EtSi(Cl)O), n = 2—7) in a ratio of ~7: 3 (68: 29 wt.%). In excess diethyl ether, the overall yield of oligoethyl(hydro)cyclosiloxanes does not exceed 25% and the major products are linear α,ω-diethoxyoligoethyl(hydro)siloxanes (EtO(EtSi(H)O) _n Et, n = 2—7) formed in 70—75% yields. A plausible reaction mechanism leading to the final products was suggested. Apparently, the reaction proceeds via ethyl(hydro)-and chloro(ethyl)silanones as intermediates.     

New linear driving force correlation spanning long and short cycle time pressure swing adsorption processes

A simple, semi-empirical, generalized expression was developed for the LDF mass transfer coefficient k as a function of the half cycle time θ _c that encompasses and transitions between the well-known regions governed by the long cycle time constant Glueckauf k and the short cycle time dependent k. This new expression can be used to estimate k = f(θ _c ) for any system, irrespective of the loading and irrespective of θ _c , no matter if k is in the cycle time dependent region or not. A three times wider transition region between the Glueckauf k and the cycle time dependent k was also established, with the Glueckauf LDF limit now valid for θ _c  > 0.3 and the short cycle time limit now valid for θ _c  < 0.01. When evaluating this region for several adsorbate-adsorbent systems, the minimum Glueckauf θ _c spanned three orders of magnitude from thousands of seconds to just a few seconds, indicating a cycle time dependent k is not necessarily limited to what is normally considered a short cycle time. For virtually any θ _c less than this minimum Glueckauf θ _c , this new first-of-its-kind expression can be used to readily provide an accurate value of k = f(θ _c ). Since the widely accepted half cycle time concept does not apply to the actual simulation of a multi-step, unequal step time, pressure swing adsorption process, the value of k = f(θ _c ) from this new expression can be based on either the shortest cycle step in the cycle or a different value of k = f(θ _c ) for each cycle step time in the cycle, with validity confirmed either by experiment or by process simulation using the exact solution to the pore diffusion equation.     

Determination of the Elemental Composition of Hydrocarbon Mixtures by Gas Chromatography with Atomic Emission Detection: Increasing the Accuracy

In this work, the accuracy of the ratio of the numbers of carbon and hydrogen atoms (n_C/n_H) determined in the molecules of the components of aliphatic hydrocarbon mixtures by gas chromatography with atomic emission detection (GC-AED) is studied as a function of the oxygen concentration in helium. It is shown that the highest accuracy is achieved at about 9% of oxygen, which is the highest oxygen concentration possible for the Agilent model G2350A GC-AED device. At the standard oxygen concentration (about 1.5%) recommended by the manufacturer, the accuracy of the n_C/n_H ratios was five to ten times lower. It is shown that improving the accuracy of the n_C/n_H ratios at the maximum oxygen concentration in plasma is followed by an increase in the detection limit approximately by an order of magnitude.     

Apparent Molar Volumes of Aqueous Solutions of Magnesium Tetraborate from 283.15 to 363.15 K and 0.1 MPa

Densities for aqueous solutions of magnesium tetraborate MgB₄O₇(aq) at the molalities of (0.00556–0.03341) mol·kg^?1 were measured with an Anton Paar Digital vibrating-tube densimeter at temperature intervals of 5 K from 283.15 to 363.15 K and 0.1 MPa. Apparent molar volumes were obtained based on the experimental density data, and the 3D diagrams of the apparent molar volume (V _? ) of MgB₄O₇(aq) against temperature (T) and molality (m) were plotted. On the basis of the Vogel–Tamman–Fulcher equation, the coefficients of the correlation equation for densities of MgB₄O₇(aq) against temperature and molality were parameterized. According to the Pitzer ion-interaction model of the apparent molar volume, the temperature correlation equations of Pitzer single-salt parameters F(i,p,T)?=?a₀?+?a₁?×?T?+?a₂?×?T ²?+?a₃/T?+?a₄?×?ln(T)?+?a₅?×?T ³ (where T is temperature in Kelvin, a _i are model parameters) for MgB₄O₇ were obtained for the first time.     

Investigation of cationic soapless P(St-<Emphasis Type="Italic">co</Emphasis>-DMAEMA) latex and its electrostatic adsorption of laponite

Cationic poly(styrene-co-N,N-dimethylaminoethyl methacrylate) (P(St-co-DMAEMA)) latexes were prepared in the absence of surfactant by using 2,2’ -azobis (2-methylpropionamidine) dihydrochloride (AIBA) as the initiator. The effects of the AIBA concentration, HCl/DMAEMA molar ratio and DMAEMA amount on the emulsion polymerization and the latex properties were investigated. The particle morphology and size, the zeta potential and the amino distribution of the P(St-co-DMAEMA) latexes were characterized by transmission electron microscope (TEM), dynamic light scattering (DLS) and conductometric titration, respectively. Results showed that the emulsion polymerization performed smoothly with high monomer conversion and narrow particle size distribution under the optimized conditions with AIBA concentration of 1 wt%, HCl/DMAEMA molar ratio of 1.2 and DMAEMA content of 5 wt%. The diameter of the dried latex particles decreased and the density of amino groups on the particle surfaces increased with increasing the DMAEMA content. The zeta potential of the P(St-co-DMAEMA) latexes was pH-dependent and the zero point was around at pH 7.2. A facile method was developed to fabricate P(St-co-DMAEMA)/laponite hybrid nanoparticles via electrostatic adsorption, in which the loading capacity of laponite platelets reached 17.7 wt%, and the resultant hybrid nanoparticles showed good thermal stability.     

Solute–solvent interactions in 2,4-dihydroxyacetophenone isonicotinoylhydrazone solutions in N,N-dimethylformamide and dimethyl sulfoxide at 298–313 K on ultrasonic and viscometric data

The speed of sound (u), density (ρ), and viscosity (η) of 2,4-dihydroxyacetophenone isonicotinoylhydrazone (DHAIH) have been measured in N,N-dimethyl formamide and dimethyl sulfoxide at equidistance temperatures 298.15, 303.15, 308.15, and 313.15 K. These data were used to calculate some important ultrasonic and thermodynamic parameters such as apparent molar volume (V _{? s} ^st ), apparent molar compressibility (K _?), partial molar volume (V _? ⁰ ) and partial molar compressibility (K _? ⁰ ), were estimated by using the values of (V _? ⁰ ) and (K _?), at infinite dilution. Partial molar expansion at infinite dilution, (? _E ⁰ ) has also been calculated from temperature dependence of partial molar volume V _? ⁰ . The viscosity data have been analyzed using the Jones–Dole equation, and the viscosity, B coefficients are calculated. The activation free energy has been calculated from B coefficients and partial molar volume data. The results have been discussed in the term of solute–solvent interaction occurring in solutions and it was found that DHAIH acts as a structure maker in present systems.     

Temperature-dependent selectivity of inclusion by <Emphasis Type="Italic">trans</Emphasis>-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid

From acetophenone solution with a small amount of water, a widely used clathrate forming compound, trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (DED), crystallizes either in the form of a clathrate with acetophenone (25°C) or in the form of hydrate (5°C). The clathrate of DED with acetophenone is triclinic, space group P-1 with the unit cell parameters: a = 8.5002(2) Å, b = 12.5247(8) Å, c = 12.8251(8) Å; α = 62.876(2)°, β = 80.454(2)°, γ = 89.789(2)°; V = 1194.4(1) ų, Z = 2; the molar ratio DED:acetophenone is 2:3. The clathrate is of channel type; the system of mutually intersecting channels propagates in [100] and [01–1] directions in the structure. The guest molecules of acetophenone are included in the channels and do not form any H-bonds with the host molecules of DED. The hydrate of DED crystallizes in monoclinic system, in space group C2/c, with the unit cell parameters: a = 31.770(6) Å, b = 8.503(2) Å, c = 12.888(3) Å; β = 104.26(3)°; V = 3374(1) ų, Z = 8; the molar ratio DED:water is 1:3. One of two carboxylic groups of the molecule of DED is deprotonated and the proton is incorporated into the hydroxonium ion H₃O⁺. The crystal structure of the hydrate of DED is of layer type with well distinguished hydrophobic and hydrophilic parts.     

Bulk properties of a liquid phase mixture {ethylene glycol+<Emphasis Type="Italic">tert</Emphasis>-butanol} in the temperature range 278.15–348.15 K and pressures of 0.1–100 MPa. II. Molar isothermal compressibility,molar isobaric expansibility,thermal pressure coefficient,and internal pressure

Based on the experimental data, the molar isothermal compressibilities, molar isobaric expansibilities, thermal pressure coefficients, internal pressures of a liquid phase mixture {ethylene glycol (1) + tert-butanol (2)} are calculated for a wide spectrum of compositions in the range of pressures of 0.1–100 MPa and temperatures of 278.15–323.15 K. Shown that the dependences of molar isothermal compressibilities K _{T, m} , molar isobaric expansibilities E _{P, m} , and isochoric thermal pressure coefficients β on the mole fraction of tert-butanol in the mixture are characterized by the absence of extrema typical of aqueous systems. The manifestation of negative partial expansibility and negative partial expansibility of ethylene glycol in the mixture is found. The thermal pressure coefficients decrease with an increase in the mole fraction of tert-butanol at all pressures and temperatures. A rise in the pressure increases the thermal pressure coefficient, while a rise in the temperature decreases its value due to a decrease of free space in the mixture. An increase in the concentration of tert-butanol leads to an increase in the negative temperature coefficient of internal pressure ΔP _int/ΔT, which indicates a weakening of intermolecular interaction at these compositions.     

Bulk properties of a liquid phase mixture {ethylene glycol+<Emphasis Type="Italic">tert</Emphasis>-butanol} in the temperature range 278.15–348.15 K and pressures of 0.1-100 MPa. I. Experimental results,excess and partial molar volumes

The densities ρ and coefficients of compressibility k = ΔV/V ₀ of a binary mixture {ethylene glycol (1) + tert-butanol (2)} in the temperature range of 278.15–323.15 K and pressures of 0.1–100 MPa over the entire range of compositions of liquid phase state are measured. Found that the coefficients of compressibility k of the mixture increase both with an increase in the concentration of tert-butanol and with a rise in temperature and pressure. The excess molar volumes of the mixture, apparent, partial molar volumes, and limiting partial molar volumes of the components are calculated. It is showed that the excess molar volumes of the mixture are negative and decrease when the pressure increases. The excess molar volumes are described by the Redlich-Kister equation. The partial molar volumes of ethylene glycol sharply decrease in the range of high concentrations of tert-butanol. The dependences of partial molar volumes of ethylene glycol are characterized by the presence of a region of temperature inversion. The “negative compressibility” of the limiting partial volumes of ethylene glycol is revealed.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-chloroamines with carbanions derived from ethyl acetoacetate and diethyl malonate

Carbanions derived from ethyl 3-oxobutanoate and diethyl malonate reacted with an equimolar amount of N-chloro-N-ethylethanamine, N-chloromorpholine, or N-chloropiperidine to give diethyl 2,3-diacetylbutanedioate and tetraethyl ethane-1,1,2,2-tetracarboxylate in 68–83% yield. The possibility of heterocoupling of ethyl 3-oxobutanoate and diethyl malonate carbanions by the action of N-chloro-N-ethylethanamine and the effect of the molar reactant ratio on the selectivity of oxidative homo- and heterocoupling were studied.