Screening of Dowex® anion-exchange resins for invertase immobilization

Commercial yeast invertase (Bioinvert^®) was immobilized by adsorption on anion-exchange resins, collectively named Dowex^® (1×8:50–400, 1×4:50–400, and 1×2:100–400). Optimal binding was obtained at pH 5.5 and 32°C. Among different polystyrene beads, the complex Dowex-1×4–200/invertase showed a yield coupling and an immobilization coefficient equal to 100%. The thermodynamic and kinetic parameters for sucrose hydrolysis for both soluble and insoluble enzyme were evaluated. The complex Dowex/invertase was stable without any desorption of enzyme from the support during the reaction, and it had thermodynamic parameters equal to the soluble form. The stability against pH presented by the soluble invertase was between 4.0 and 5.0, whereas for insoluble enzyme it was between 5.0 and 6.0. In both cases, the optimal pH values were found in the range of the stability interval. The K _m and V _max for the immobilized invertase were 38.2 mM and 0.0489 U/mL, and for the soluble enzyme were 40.3 mM and 0.0320 U/mL.     

Near infrared spectroscopy in the study of polymorphic transformations

The potential of near infrared (NIR) spectroscopy for the characterization of polymorphs in the active principle of a commercial formulation prior to and after the manufacturing process was assessed. Polymorphism in active principles is extremely significant to the pharmaceutical industry. Polymorphic changes during the production of commercial pharmaceutical formulations can alter some properties of the resulting end-products. Multivariate curve resolution-alternating least squares (MCR-ALS) methodology was used to obtain the “pure” NIR spectrum for the active principle without the need to pretreat samples. This methodology exposed the polymorphic transformation of Dexketoprofen Trometamol (DKP) in both laboratory and production samples obtained by wet granulation. No polymorphic transformation, however, was observed in samples obtained by direct compaction. These results were confirmed using by X-ray powder diffractometry (XRD) and differential scanning calorimetry (DSC) measurements. Pure crystalline polymorphs of DKP were available in the laboratory but amorphous form was not, nevertheless the developed methodology allows the identification of amorphous and crystal forms in spite of the lack of pure DKP.     

Microwave-induced multiple functionalization of carbon nanotubes

We describe a new synthetic strategy to produce multifunctionalized carbon nanotubes using a combination of two different addition reactions, the 1,3-dipolar cycloaddition of azomethine ylides and the addition of diazonium salts, both via a simple and fast microwave-induced method. The presence of multifunctionality on the SWNTs has been confirmed using the most useful techniques for the characterization of carbon nanotubes. The doubly functionalized SWNTs can be considered potentially useful for many interesting applications.     

Curcumin as Prospective Anti-Aging Natural Compound: Focus on Brain

The nutrients and their potential benefits are a new field of study in modern medicine for their positive impact on health. Curcumin, the yellow polyphenolic compound extracted from Curcuma longa species, is widely used in traditional Ayurvedic medicine to prevent and contrast many diseases, considering its antioxidant, immunomodulatory, anti-inflammatory, anti-microbial, cardio-protective, nephron-protective, hepato-protective, anti-neoplastic, and anti-rheumatic proprieties. In recent years, the investigations of curcumin have been focused on its application to aging and age-associated diseases. Aging is a physiological process in which there is a decreasing of cellular function due to internal or external stimuli. Oxidative stress is one of the most important causes of aging and age-related diseases. Moreover, many age-related disorders such as cancer, neuroinflammation, and infections are due to a low-grade chronic systemic inflammation. Curcumin acting on different proteins is able to contrast both oxidative stress than inflammation. In the brain, curcumin is able to modulate inflammation induced by microglia. Finally in brain tumors curcumin is able to reduce tumor growth by inhibition of telomerase activity. This review emphasizes the anti-aging role of curcumin focusing on its mechanism to counteract aging in the brain. Moreover, new formulations to increase the bioavailability of curcumin are discussed.     

Facile synthesis of azocino[4,3-b]indoles by ring-closing metathesis

The azocino[4,3-b]indole system, tricyclic substructure of the indole alkaloids apparicine and ervaticine, is efficiently assembled by ring-closing metathesis of 2-allyl-3-(allylaminomethyl)indoles. The metathesis sites are introduced into the indole nucleus by reductive amination of a 3-formyl derivative with allylamine, followed by α-lithiation with subsequent electrophilic trapping with acrolein.     

Analysis of 27 polycyclic aromatic hydrocarbons by matrix solid-phase dispersion and isotope dilution gas chromatography-mass spectrometry in sewage sludge from the Spanish area of Madrid

A method for the determination of 27 polycyclic aromatic hydrocarbons (PAHs) in sludge from wastewater treatment plants (WWTPs) located in urban, industrial or rural zones is presented. PAHs were extracted by matrix solid-phase dispersion (MSPD) assisted by sonication. Purification of extracts was carried out by solid-phase extraction with C(18) and PAHs were eluted with acetonitrile. PAHs were determined by isotope dilution gas chromatography with electron impact mass spectrometric detection in the selected ion-monitoring mode (GC-MS-SIM), using deuterated PAHs as internal standards. The limits of detection ranged from 0.03 ng/g for acenaphthylene to 0.45 ng/g for benzo[b]naphtho[2,1-d]thyophene. After optimization, the method was validated with a certified reference sludge. The proposed analytical method was applied to determine PAH levels in sewage sludge samples collected from 19 water treatment plants located in the province of Madrid (Spain). In most of the examined samples, phenanthrene was the main compound with a mean concentration of 1062 ng/g. PAHs were detected in all of the samples, with total concentrations between 390 and 6390 ng/g dry weight for the 27 PAHs analyzed and from 310 to 5120 ng/g dry weight for the sum of the 10 PAHs considered in the draft European Union directive.     

Central limit theorem for Maxwellian molecules and truncation of the wild expansion

We prove an L¹ bound on the error made when the Wild summation for solutions of the Boltzmann equation for a gas of Maxwellian molecules is truncated at the n^th stage. This gives quantitative control over the only constructive method known for solving the Boltzmann equation. As such, it has recently been applied to numerical computation but without control on the approximation made in truncation. We also show that our bound is qualitatively sharp and that it leads to a simple proof of the exponentially fast rate of relaxation to equilibrium for Maxwellian molecules along lines originally suggested by McKean. © 2000 John Wiley & Sons, Inc.