Characterization of electronic structure and physicochemical properties of antiparasitic nifurtimox analogues: A theoretical study

American trypanosomiasis, also known as Chagas' disease, is caused by Trypanosoma cruzi (T. cruzi). It is well known that trypanosomes, and particularly T. cruzi, are highly sensitive towards oxidative stress, i.e., to compounds than are able to produce free radicals. Generally, nifurtimox (NFX) and benznidazol are most effective in the acute phase of the disease; therefore, nitroheterocycles constitute good models to design other nitrocompounds with specific biological characteristics. Thus, we have performed an ab initio study at the Hartree‐Fock and Density Functional Theory levels of theory of several NFX analogues recently synthesized, to characterize them by obtaining their electronic, structural, and physicochemical properties, which might be linked to the observed antichagasic activity. The antitrypanosomal activity scale previously reported for the NFX analogues studied in this work is in good agreement with our theoretical results, from which we can conclude that the activity seems to be related to the reactivity along with the acidity observed for the most active molecules. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Magnetic material in head, thorax, and abdomen of Solenopsis substituta ants: a ferromagnetic resonance study

Ferromagnetic resonance temperature dependence is used to study the magnetic material in smashed head, thorax, and abdomen of Solenopsis substituta ants. These three body parts present the five lines previously observed in other social insects. The magnetic material content is slightly higher in heads with antennae than in abdomen with petiole. Isolated nanoparticle diameters were estimated as 12.5 +/- 0.1 and 11.0 +/- 0.2 nm in abdomen with petiole and head with antennae, respectively. The presence of linear chains of these particles or large ellipsoidal particles are suggested. A bulk-like magnetite particle was observed in the thorax. The Curie-Weiss, the structural-electronic and ordering transition temperatures were obtained in good agreement with those proposed for magnetite nanoparticles.     

Hugoniot–Maslov chains of a shock wave in conservation law with polynomial flow

In this paper we give a theoretical foundation to the asymptotical development proposed by V. P. Maslov for shock type singular solutions of conservations laws, in the framework of Colombeau theory of generalized functions. Indeed, operating with Colombeau differential algebra of simplified generalized functions, we proof that Hugoniot–Maslov chains are necessary conditions for the existence of shock waves in conservation laws with polynomial flows. As a particular case, these equations include the Hugoniot–Maslov chains for shock waves in the Hopf equation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Carbon Nanotubes,Nanocrystal Forms,and Complex Nanoparticle Aggregates in common fuel-gas combustion sources and the ambient air

Aggregated multiwall carbon nanotubes (with diameters ranging from ∼3 to 30nm) and related carbon nanocrystal forms ranging in size from 0.4 to 2 μm (average diameter) have been collected in the combustion streams for methane/air, natural gas/air, and propane gas/air flames using a thermal precipitator. Individual particle aggregates were collected on carbon/formvar-coated 3mm nickel grids and examined in a transmission electron microscope, utilizing bright-field imaging, selected-area electron diffraction analysis, and energy-dispersive X-ray spectrometry techniques. The natural gas and propane gas sources were domestic (kitchen) stoves, and similar particle aggregates collected in the outdoor air were correspondingly identified as carbon nanocrystal aggregates and sometimes more complex aggregates of silica nanocrystals intermixed with the carbon nanotubes and other carbon nanocrystals. Finally, and in light of the potential for methane-series gas burning as major sources of carbon nanocrystal aggregates in both the indoor and outdoor air, data for natural gas consumption and corresponding asthma deaths and incidence are examined with a degree of speculation regarding any significance in the correlations.     

Preparation and optical characterization of two photoactive poly(bisphenol a ethoxylate diacrylate) copolymers containing designed amino‐nitro‐substituted azobenzene units,obtained via classical and frontal polymerization,using novel ionic liquids as initiators

The frontal polymerization (FP) of bisphenol A ethoxylate diacrylate (BPAEDA) was carried with and without the presence of two different azobenzene comonomers by means of an external heating source. The first azomonomer (MDR‐1) is a derivative of disperse red‐1, N‐ethyl‐N‐(2‐hydroxyethyl)‐4‐(4‐nitrophenylazo)aniline, whereas the second (E)‐2‐(4‐((4‐nitrophenyl)diazenyl)phenyl)‐5,8,11‐trioxa‐2‐azatridecan‐13‐yl methacrylate (4PEGMAN) comes from the azo‐dye N‐methyl‐N‐{4‐[(E)‐(4‐nitrophenyl)diazenyl]phenyl}‐N‐(11‐hydroxy‐3,6,9‐trioxaundecas‐1‐yl) amine. In this work, an ionic liquid trihexyltetradecylphosphonium persulfate was used as initiator. This compound produced stable propagating polymerization fronts with good velocities and moderate maximum temperature values. Moreover, this initiator prevented bubble formation and was found to be the most efficient when it was used in lower amounts with respect to other initiators, such as benzoyl peroxide, 2,2′‐azobisisobutyronitrile, aliquat persulfate®, and tetrabutylphosphonium persulfate. The thermal properties of the obtained polymers and copolymers were determined by thermogravimetric analysis and differential scanning calorimetry. The nonlinear optical (NLO) characterizations of the developed BPAEDA/MDR‐1 and BPAEDA/4PEGMAN copolymers were performed according to the Z‐Scan technique in film samples prepared by classical polymerization. It has been proven that samples with higher 4PEGMAN content (0.26 mol %) exhibited outstanding cubic NLO‐activity with positive NLO‐refractive coefficients in the promising range of n₂ = +3.2 × 10^?4 esu. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Conotoxins containing nonnatural backbone spacers: cladistic-based design, chemical synthesis, and improved analgesic activity

Disulfide-rich neurotoxins from venomous animals continue to provide compounds with therapeutic potential. Minimizing neurotoxins often results in removal of disulfide bridges or critical amino acids. To address this drug-design challenge, we explored the concept of disulfide-rich scaffolds consisting of isostere polymers and peptidic pharmacophores. Flexible spacers, such as amino-3-oxapentanoic or 6-aminohexanoic acids, were used to replace conformationally constrained parts of a three-disulfide-bridged conotoxin, SIIIA. The peptide-polymer hybrids, polytides, were designed based on cladistic identification of nonconserved loci in related peptides. After oxidative folding, the polytides appeared to be better inhibitors of sodium currents in dorsal root ganglia and sciatic nerves in mice. Moreover, the polytides appeared to be significantly more potent and longer-lasting analgesics in the inflammatory pain model in mice, when compared to SIIIA. The resulting polytides provide a promising strategy for transforming disulfide-rich peptides into therapeutics.     

Characterization of Wallpaintings from the Caliphal Baths of Cordoba (Spain) by X-Ray Diffraction and Raman Microspectroscopy

Wallpainting fragments from the Caliphal Baths of Cordoba, Spain, were studied in this work for the first time. X-ray diffraction (XRD) and Raman microspectroscopy allowed the chemical nature of the pigments used by the Arabic artists of the time to be identified. All pigments were applied over a gypsum priming layer. The white, red, and yellow colors used were obtained from gypsum, hematite, and goethite, respectively. Some pigments were prepared by mixing these materials. The analytical techniques used also allowed the mortar material to be identified. The results of this study may be useful to develop effective conservation strategies for archaeological remains.