Synthesis of Ethyl 2,2-Bis{[(benzoylcarbamothioyl)oxy]methyl}propanoate and Its Complexes with Copper(II) and Cobalt(II) Ions

Russian Journal of General Chemistry - The structures of ethyl 2,2-bis{[(benzoylcarbamothioyl)oxy]methyl}propanoate and its 1 : 1 complexes with copper(II) and cobalt(II) ions were determined by...     

Kinetic studies of lipase from Candida rugosa

The search for an in expensive support has motivated our group to undertake this work dealing with the use of chitosan as matrix for immobilizing lipase. In addition to its low cost, chitosan has several advantages for use as a support, including its lack of toxicity and chemical reactivity, allowing easy fixation of enzymes. In this article, we describe the immobilization of Canada rugosa lipase onto porous chitosan beads for the enzymatic hydrolysis of oliveoil. The binding of the lipase onto the support was performed by physicalad sorption using hexane as the dispersion medium. A comparativestudy between free and immobilized lipase was conducted in terms of pH, temperature, and thermal stability. A slightly lower value for optimum pH (6.0) was found for the immobilized form in comparison with that attained for the soluble lipase (7.0). The optimum reaction temperature shifted from 37°C for the free lipase to 50°C for the chitosan lipase. The patterns of heat stability indicated that the immobilization process tends to stabilize the enzyme. The half-life of the soluble free lipase at 55°C was equal to 0.71 h (K _d=0.98 h⁻¹), whereas for the immobilized lipase it was 1.10 h (K _d=0.63 h⁻¹). Kinetics was tested at 37°C following the hydrolysis of olive oil and obeys the Michaelis-Menten type of rate equation. The K _m was 0.15 mM and the V _max was 51 μmol/(min·mg), which were lower than for free lipase, suggesting that the apparent affinity toward the substrate changes and that the activity of the immobilized lipase decreases during the course of immobilization.     

Synthesis and Complexing Properties of <Emphasis Type="Italic">p</Emphasis>-Toluensulfonylamido and Phosphorylamido Derivatives of Second-Generation Hyperbranched Polyester

Hyperbranched polyesters containing terminal p-toluenesulfonylamido and diethoxyphosphorylamido groups have been synthesized, and their complexes with copper(II) and cobalt(II) ions have been prepared. The thermal stability of the ligands and their metal complexes has been studied by differential scanning calorimetry.     

TGA and magnetization measurements for determination of composition and polymer conversion of magnetic hybrid particles

Magnetic hybrid colloidal particles can be characterized using various techniques and numerous tools leading generally to particles size, size distribution, and electrokinetic properties. However, the chemical composition of these hybrid particles can be estimated using thermal gravimetric analysis (TGA). More interestingly, the combination of this quantitative technique with the magnetization measurement leads not only to chemical composition but also to the overall polymerization conversion and more precisely to the polymerization conversion on the seed particles. In fact, the TGA performed on dried magnetic particles leads to exact organic/inorganic chemical composition. Regarding the magnetization, the amount of magnetic material can be deduced, and consequently, the amount of non‐magnetic material can be also estimated. Thus, TGA and magnetization measurements are considered as complementary techniques for characterization of magnetic hybrid colloidal particles. Copyright © 2015 John Wiley & Sons, Ltd.     

Esterification activity and stability of Candida rugosa lipase immobilized into chitosan

Microbial lipase from Candida rugosa immobilized into porous chitosan beads was tested for esterification selectivity with butanol and different organic acids (C2–C12), and butyric acid and different aliphatic alcohols (C2–C10). After 24 h, the acids tested achieved conversions of about 40–45%. Acetic acid was the only exception, and in this case butanol was not consumed. Different alcohols led to butyric acid conversions >40%, except for ethanol, in which case butyric acid was converted only 26%. The system’s butanol and butyric acid were selected for a detailed study by employing an experimental design. The influence of temperature, initial catalyst concentration, and acid:alcohol molar ratio on the formation of butyl butyrate was simultaneously investigated, employing a 2³ full factorial design. The range studied was 37–50°C for temperature (X₁), 1.25–2.5% (w/v) for the catalyst concentration (X₂), and 1 and 2 for the acid:alcohol molar ratio (X₃). Catalyst concentration (X₂) was found to be the most significant factor and its influence was positive. Maximum ester yield (83%) could be obtained when working at the lowest level for temperature (37°C), highest level for lipase concentration (2.5% [w/v]), and center level of acid:alcohol molar ratio (1.5). The immobilized lipase was also used repeatedly in batch esterification reactions of butanol with butyric acid, revealing a half-life of 86 h.     

Interaction of Poly(benzoyl thiocarbamate)-Modified Hyperbranched Polyester with Co(II) and Cu(II) Nitrates

The interaction of Co(NO3)2 and Cu(NO3)2 with hyperbranched polyester containing 7 terminal benzoyl thiocarbamate groups has been studied by IR-Fourier and electron absorption spectroscopy. А new polynuclear complexes of Co(II) and Cu(II) with poly(benzoyl thiocarbamate)-modified hyperbranched polyester have been synthesized. It has been found that the oxygen and sulfur atoms of the peripheral benzoyl thiocarbamate fragments of the macroligand are involved in coordination with metal ions, the metal to ligand ratio being 7 : 1.     

Preparation and characterization of submicron hybrid magnetic latex particles

Micrometer magnetic hybrid particles are of great interest in biomedical field, and various morphologies have been prepared via encapsulation processes. Regarding submicron, only few processes have been investigated and the most recent one leading to highly magnetic submicron magnetic hybrid particles is based on oil in water magnetic emulsion (MES) transformation. The encapsulation of magnetic iron oxide nanoparticles forming oil in water MES was investigated using different styrene/cross‐linker divinylbenzene volume ratio in the presence of potassium persulfate initiator. The encapsulation performed in this work is basically conducted by using well‐defined oil in water MES as a seed in radical emulsion polymerization. The chemical composition, morphology, iron oxide content, magnetic properties, electrokinetic properties, particle size, and size distribution of the prepared magnetic hybrid particles were examined using various techniques. The desired perfect magnetic core and polymer shell morphology were successfully obtained, and the final magnetic hybrid particles are superparamagnetic in nature and exhibit high iron oxide content (64 wt %). Copyright © 2015 John Wiley & Sons, Ltd.     

Poly(p‐phenylenediamine)‐coated magnetic particles: Preparation and electrochemical properties

Magnetic particles are of great interest in various biomedical applications, such as, sample preparation, in vitro biomedical diagnosis, and therapy. For biosensing applications, the used functional magnetic particles should answer numerous criteria such as; submicron size in order to avoid rapid sedimentation, high magnetic content for fast separations under applied magnetic field, and finally, good colloidal stability. Therefore, the aim of this work was to prepare submicron magnetic core and conducting polymer shell particles. The polymer shell was induced using p‐phenylenediamine as key monomer. The obtained core–shell particles were characterized in terms of particle size, size distribution, magnetization properties, Fourier transform infrared (FTIR) analysis, surface morphology, chemical composition, cyclic voltammetry, and impedance spectroscopy. The best experimental condition was found using 40 mg of povidone (PVP—stabilizing agent) and 0.16 mmol of p‐phenylenediamine. Using such initial composition, the core‐shell magnetic nanoparticles shown a narrowed size distribution around 290 nm and high magnetic content (above 50%). The obtained amino containing submicron highly magnetic particles were found to be a conducting material and superparamagnetic in nature. These promising conducting magnetic particles can be used for both transport and lab‐on‐a‐chip detection.