Water Miscible Mono Alcohols’ Effect on the Proteolytic Performance of Bacillus clausii Serine Alkaline Protease

In this study, our investigations showed that the increasing concentrations of all examined mono alcohols caused a decrease in the V _m, k _cat and k _cat/K _m values of Bacillus clausii GMBE 42 serine alkaline protease for casein hydrolysis. However, the K _m value of the enzyme remained almost the same, which was an indicator of non-competitive inhibition. Whereas inhibition by methanol was partial non-competitive, inhibition by the rest of the alcohols tested was simple non-competitive. The inhibition constants (K _I) were in the range of 1.32–3.10 M, and the order of the inhibitory effect was 1-propanol>2-propanol>methanol>ethanol. The ΔG ^≠ and ΔG ^≠ _E???T values of the enzyme increased at increasing concentrations of all alcohols examined, but the ΔG ^≠ _ES value of the enzyme remained almost the same. The constant K _m and ΔG ^≠ _ES values in the presence and absence of mono alcohols indicated the existence of different binding sites for mono alcohols and casein on enzyme the molecule. The k _cat of the enzyme decreased linearly by increasing log P and decreasing dielectric constant (D) values, but the ΔG ^≠ and ΔG ^≠ _E???T values of the enzyme increased by increasing log P and decreasing D values of the reaction medium containing mono alcohols.     

The effect of Benzo Substitution on Complexation of Diaza 18-crown-6 ethers Derivatives with NaClO4

The complexation of the crown ethers with Na⁺ ion was studied. ¹H-NMR chemical shifts are discussed in terms of structural modification as well as also binding studies with UV–vis spectra were included. This revised version was published online in July 2005 with a corrected issue number. An erratum to this article is available at .     

Polymer supported 5,10,15,20-tetrakis(phenoxy acetic acid)porphyrin derivative for separation and preconcentration of d- and f-electron metals

5,10,15,20-tetrakis(phenoxy acetic acid) porphyrin (PAAP) was covalently linked to Merrifield chloromethylated resin. Characterization of PAAP and the modified polymeric matrix were performed by ¹H NMR, FTIR and elemental analysis. The sorbent was used for the separation and enrichment of the d-electron metals (Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)) at pH 6–8 and of the f-electron metals U(VI) and Th(IV) at pH 4–5. The metals ions were preconcentrated with a concentration factor range of 115–215 and then determined by flame atomic absorption spectrometry or visible spectrophotometry using Arsenazo(III). The retained metals were eluted with 2.0 mol L⁻¹ HNO₃ in the case of the d-electron metals and 0.1/0.25 mol L⁻¹ HCl in the case of the f-electron metals. The procedure was validated by analyzing the NIST standard reference material 2709 (San Joaquin Soil). Correspondence: Melek Merdivan, Chemistry Department, Faculty of Arts and Sciences, Dokuz Eylul University, 35160 Buca, Izmir, Turkey     

Chemisorption of thiol‐functionalized metallocene molecules on Si(111)‐ Ag√3×√3 surface: A density functional theory study

Herein, chemical adsorption properties of the thiol‐functionalized metallocene molecules [M(C₅H₄SH)₂] on Si(111)‐Ag√3×√3 surface were investigated using density functional theory calculation. For this purpose, thiol‐modified ferrocene [Fe(C₅H₄SH)₂], osmocene [Os(C₅H₄SH)₂], and ruthenocene [Ru(C₅H₄SH)₂] molecules were attached on the surface via two different binding models. The more favorable chemical binding energies of [Fe(C₅H₄SH)₂], [Os(C₅H₄SH)₂], and [Ru(C₅H₄SH)₂] molecules were calculated as ?3.42, ?2.15, and ?2.00 eV, respectively. The results showed that the adsorption energies of metallocene molecules change independently by increasing the radius of metal ions where on going down the group of the periodic table. The calculated adsorption energies showed that [Fe(C₅H₄SH)₂] molecule was more stable on the Si(111)‐Ag√3×√3 surface. By calculating the electronic band structure for metallocene/Si(111)‐Ag√3×√3 surfaces, we identified a flat dispersion band in a part of the surface Brillouin zone. © 2015 Wiley Periodicals, Inc.     

Pd(II) complexes of novel phosphine ligands: Synthesis,characterization, and catalytic activities on Heck reaction

Novel phosphine oxides, (((3-methylpyridin-2-yl)amino)methyl)diphenylphosphine oxide (1) and diphenyl((pyrazin-2-ylamino)methyl)phosphine oxide (2), were synthesized and characterized. Phosphines ligands (3 and 4) were obtained by the reduction of 1 and 2 with AlH₃, monitored by ³¹P NMR spectroscopy. Pd(II) complexes of 3 and 4 were synthesized and characterized (5 and 6). The catalytic activity of 5 and 6 was tested on the reaction of styrene with both activated and deactivated aryl bromides in air. The results of the catalytic experiments were discussed through DFT calculations.     

Microwave-assisted dilute acid pretreatment of different agricultural bioresources for fermentable sugar production

Microwave-assisted pretreatment can be used for fermentable sugar production from lignocellulosic biomass. In this study, the optimum hydrolysis conditions of barley husk, oat husk, wheat bran, and rye bran were determined in power level, treatment time, solid-to-liquid ratio and dilute acid ratio as follows: 700 W, 6.92 min, 1:18.26 w/v, and 3.67% for barley husk, 600 W, 6.96 min, 1:17.22 w/v, and 3.47% for oat husk, 600 W, 6.92 min, 1:16.69 w/v, and 1.85% for wheat bran, and 460 W, 6.15 min, 1:17.14 w/v, and 2.72% for rye bran. The fermentable sugar concentrations were 37.21 (0.68 g/g), 38.84 (0.67 g/g), 49.65 (0.83 g/g), and 36.27 g/L (0.62 g/g) under optimum conditions, respectively. The results showed that microwave-assisted pretreatment is a promising technology which can be successfully implemented for the hydrolysis of lignocellulosic biomass for high sugar yield. On the other hand, hydrolysates included some inhibitors such as organic acids, furans, and phenolic compounds. Lignocellulosic biomass used in this study can be employed as good feedstocks for value-added product production in the fermentation process, after the inhibitors have been detoxified/removed with different detoxification methods.     

The morphology and structure of PS‐b‐P4VP block copolymer films by solvent annealing: effect of the solvent parameter

Lamellae (symmetric) forming polystyrene‐b‐poly(4‐vinylpyridine) (PS‐b‐P4VP) block copolymers (BCPs) were used to produce nanostructured thin films by solvent (toluene) casting (spin‐coating) onto silicon substrates. As expected, strong micellization of PS‐P4VP in toluene results in poorly ordered hexagonally structures films. Following deposition the films were solvent annealed in various solvents and mixtures thereof. A range of both morphologies including micelle and microphase separated structures were observed. It was found that nanostructures typical of films of regular thickness (across the substrate) and demonstrating microphase separation occurred only for relatively few solvents and mixtures. The data demonstrate that simple models of solvent annealing based on swelling of the polymer promoting higher polymer chain mobility are not appropriate and more careful rationalization is required to understand these data. Analysis suggests that regular phase separated films can only be achieved when the copolymer Hildebrand solubility parameter is very similar to the value of the solvent. It is suggested that the solvent anneal method used is best considered as a liquid phase technique rather than a vapor phase method. The results show that solvent annealing methods can be a very powerful means to control structure and in some circumstances dominate other factors such as surface chemistry and surface energies. Copyright © 2009 John Wiley & Sons, Ltd.     

Inclusion complexes of fluconazole with β-cyclodextrin: physicochemical characterization and in vitro evaluation of its formulation

Fluconazole (FZ) is a triazole antifungal drug administered orally or intravenously. It is employed for the treatment of mycotic infections. However, the efficacy of FZ is limited with its poor aqueous solubility and low dissolution rate. One of the important pharmaceutical advantages of cyclodextrins is to improve pharmacological efficacy of drugs due to increasing their aqueous solubility. The aim of present study was to prepare an inclusion complex of FZ and β-cyclodextrin (β-CD) to improve the physicochemical and biopharmaceutical properties of FZ. The effects of β-CD on the solubility of FZ were investigated according to the phase solubility technique. Complexes were prepared with 1:1 M ratio by different methods namely, freeze-drying, spray-drying, co-evaporation and kneading. For the characterization of FZ/β-CD complex, FZ amount, practical yield %, thermal, aqueous solubility, XRD, FT-IR and NMR (¹H and ¹³C) analysis were performed. In vitro dissolution from hard cellulose capsules containing FZ/β-CD complexes was compared to pure FZ and its commercial capsules and evaluated by f₁ (difference) and f₂ (similarity) factors. Paddle method defined in USP 31 together with high pressure liquid chromatographic method were used in in vitro dissolution experiments. It was found that solubility enhancement by FZ/β-CD complexes depends on the type of the preparation method. High release of active agent from hard cellulose capsules prepared with β-CD complexes compared to commercial capsules was attributed to the interactions between β-CD and active agent, high energetic amorphous state and inclusion complex formation.     

Microphase Separation of Phenylene Oligomers with Polymeric Side Chains: A Dissipative Particle Dynamics Study

The microphase‐separated morphologies of p‐phenylene oligomers with POx, PCL, PS, and PEO side chains are studied using DPD simulations. It is shown that the microphase‐separated morphologies depend significantly on the degree of chemical incompatibility between the components as indicated by the Flory‐Huggins interaction parameters. The good agreement of the microphase separated morphologies as simulated by DPD with the experimentally determined thin film morphologies suggests that DPD can produce convincing morphological information at the nanoscale. The results show that grafting of polymeric side chains can be an important tool to control the morphology of polymers with a rigid backbone.