Physical properties of edible films based on bovine myofibril proteins

Myofibril proteins have excellent filmogenic properties. The objective of this article was to study the effect of the thermal treatment, of the pH and of the plasticizer concentration (Cp) of the filmogenic solution (FS), using over some physical properties of edible films, using a surface and response methodology (SRM). Films were made of lyophilized myofibril proteins (LMP) extracted from bovine muscle, employing the technique of solubility obtained from diluted saline solutions. The films were elaborated from FS containing 1 g of LMP/100g of FS and from Cp of 50 g to 79 g of glycerin/100 g of LMP. The LMP was dispersed in water under moderate agitation, and the pH was kept at 2.5-3.5 with the use of acetic acid. The FS were submitted to thermal treatment at different temperatures for 45 minutes. Films were dried in ventilated oven at 37 degrees C/18hr, conditioned at 75% of relative humidity at 25 degrees C/48 hr before analysis of: mechanical properties by puncture test; apparent opacity by spectrophotometer; solubility by immersion in water; and water vapor permeability by the gravimetric method. In general, films showed good appearance, translucent, easily handled and touchable, except for the films formed with pH 2.5 and at a low temperature (35 degrees C), with a medium thickness of 0.400 +/- 0.005 mm. The pH of the FS significantly affected all the physical properties under study. The temperature of the thermal treatment of the FS greatly affected the force at the rupture, solubility and water vapor permeability. This treatment can promote intermolecular interactions through the formation of disulphide bonds; however a very intense treatment can reverse this effect by irreversible structural alterations in the proteins. The glycerol concentration affected considerably all the properties under study, with the exception of the apparent opacity. Plasticizer increases the mobility of macromolecules with consequences in all physical properties.

Exponential depletion of neutral dangling bonds density (D-0) by rare-earth doping in amorphous Si films

In this work we study the effect reduction in the density of dangling bond species D-0 states in rare-earth (RE) doped a-Si films as a function concentration for different RE-specimens. The films a-Si-1_(x) REx, RE=Y3+, Gd3+, Er3+, Lu3+) were prepared by co-sputtering and investigated by electron spin resonance (ESR) and Raman scattering experiments. According to our data the RE-doping reduces the ESR signal intensity of the D-0 states with an exponential dependence on the rare-concentration. Furthermore, the reduction produced by the magnetic rare-earths Gd3+ and Er3+ is remarkably greater than that caused by Y3+ and Lu3+, which led us to suggest an exchange-like coupling between the spin of the magnetic REs3+ and the spin of silicon neutral dangling bonds. (C) 2011 Elsevier B.V. All rights reserved.

Degradation of resin-dentin bonds of etch-and-rinse adhesive system to primary and permanent teeth

The aim of this in vitro study was to compare the degradation of resin-dentin bonds of an etch-and-rinse adhesive system to primary and permanent teeth. Flat superficial coronal dentin surfaces from 5 primary second molars and 5 permanent third molars were etched with phosphoric acid and bonded with an adhesive system (Adper Single Bond 2, 3M ESPE). Blocks of resin composite (Z250, 3M ESPE) were built up and the teeth sectioned to produce bonded sticks with a 0.8 mm(2) cross-sectional area. The sticks of each tooth were randomly divided and assigned to be subjected to microtensile testing immediately (24 h) or after aging by water storage (6 months). Data were analyzed by two-way repeated measures ANOVA and Tukey post hoc test (alpha = 0.05). Failure mode was evaluated using a stereomicroscope (400x). Microtensile values significantly decreased after the 6 months aging, independent of the dentin substrate. In 24 h, the values obtained to primary dentin were lower compared with permanent dentin. This difference was not maintained after aging. Adhesive/mixed failure was predominant in all experimental groups. In conclusion, degradation of resin-dentin bonds of the etch-and-rinse adhesive system occurred after 6 months of water storage; however, the reduction in bond strength values was higher for permanent teeth.

The nature of Ru-NO bonds in ruthenium tetraazamacrocycle nitrosyl complexes-a computational study

Ruthenium complexes including nitrosyl or nitrite complexes are particularly interesting because they can not only scavenge but also release nitric oxide in a controlled manner, regulating the NO-level in vivo. The judicious choice of ligands attached to the [RuNO] core has been shown to be a suitable strategy to modulate NO reactivity in these complexes. In order to understand the influence of different equatorial ligands on the electronic structure of the Ru-NO chemical bonding, and thus on the reactivity of the coordinated NO, we propose an investigation of the nature of the Ru-NO chemical bond by means of energy decomposition analysis (EDA), considering tetraamine and tetraazamacrocycles as equatorial ligands, prior to and after the reduction of the {RuNO}(6) moiety by one electron. This investigation provides a deep insight into the Ru-NO bonding situation, which is fundamental in designing new ruthenium nitrosyl complexes with potential biological applications.

Degradation of the resin-dentin bonds after simulated and inhibited cariogenic challenge in an in situ model

The aim of this study was to evaluate the resindentin bonds of two simplified etch-and-rinse adhesive after simulated cariogenic and inhibited cariogenic challenge in situ. Dental cavities (4 mm wide, 4 mm long, and 1.5 mm deep) were prepared in 60 bovine teeth with enamel margins. Restorations were bonded with either adhesive Adper Single Bond 2 (3MESPE) or Optibond Solo Plus (Kerr). Forty restorations were included in an intra-oral palatal appliance that was used for 10 adult volunteers while the remaining 20 dental blocks were not submitted to any cariogenic challenge [NC group] and tested immediately. For the simulated cariogenic challenge [C+DA], each volunteer dropped 20% sucrose solution onto all blocks four times a day during 14 days and distilled water twice a day. In the inhibited cariogenic challenge group [C + FA], the same procedure was done, but slurry of fluoride dentifrice (1.100 ppm) was applied instead of water. The restored bovine blocks were sectioned to obtain a slice for cross-sectional Vickers microhardness evaluation and resindentin bonded sticks (0.8 mm2) for resindentin microtensile evaluation. Data were evaluated by two-way ANOVA and Tukey's tests (a = 0.05). Statistically lower microhardness values and degradation of the resindentin bonds were only found in the C + DW group for both adhesives. The in situ model seems to be a suitable short-term methodology to investigate the degradation of the resindentin bonds under a more realistic condition. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 100B: 14661471, 2012.

Uma análise econômico-atuarial dos death bonds

Um death bond é um título emitido por uma instituição financeira para comprar uma apólice de seguro de vida de um segurado que deseja receber recursos ainda em vida. Este trabalho faz a precificação dos death bonds para ambos os gêneros e diferentes idades de contratação do seguro, empregando técnicas de modelagem atuarial. Os resultados iniciais mostram pouca atratividade para os investidores no título. Uma extensão do modelo mostra que se os investidores conseguirem identificar os segurados com as piores condições de saúde, os retornos são substancialmente mais elevados e os desvios-padrão são bastante reduzidos.

Electron Interactions with Disulfide Bridges

Because of its electronic properties, sulfur plays a major role in a variety of metabolic processes and, more in general, in the chemistry of life. In particular, S-S bridges between cysteines are present in the amino acid backbone of proteins. Protein disulfur radical anions may decay following different paths through competing intra and intermolecular routes, including bond cleavage, disproportionation, protein-protein cross linking, and electron transfer. Indeed, mass spectrometry ECD (electron capture dissociation massspectroscopy) studies have shown that capture of low-energy (<0.2 eV) electrons by multiply protonated proteins is followed by dissociation of S-S bonds holding two peptide chains together. In view of the importance of organic sulfur chemistry, we report on electron interactions with disulphide bridges. To study these interactions we used as prototypes the molecules dimethyl sulfide [(CH3)2S] and dimethyl disulfide [(H3C)S2(CH3)]. We seek to better understand the electron-induced cleavage of the disulfide bond. To explore dissociative processes we performed electron scattering calculations with the Schwinger Multichannel Method with pseudopotentials (SMCPP), recently parallelized with OpenMP directives and optimized with subroutines for linear algebra (BLAS) and LAPACK routines. Elastic cross sections obtained for different S-S bond lengths indicate stabilization of the anion formed by electron attachment to a σ*SS antibonding orbital, such that dissociation would be expected.