Volume and energy folding landscape of prion protein revealed by pressure

The main hypothesis for prion diseases proposes that the cellular protein (PrP C) can be altered into a misfolded, ß-sheet-rich isoform, the PrP Sc (from scrapie). The formation of this abnormal isoform then triggers the transmissible spongiform encephalopathies. Here, we discuss the use of high pressure as a tool to investigate this structural transition and to populate possible intermediates in the folding/unfolding pathway of the prion protein. The latest findings on the application of high pressure to the cellular prion protein and to the scrapie PrP forms will be summarized in this review, which focuses on the energetic and volumetric properties of prion folding and conversion.

Classification of brain tumor extracts by high resolution ¹H MRS using partial least squares discriminant analysis

High resolution proton nuclear magnetic resonance spectroscopy (¹H MRS) can be used to detect biochemical changes in vitro caused by distinct pathologies. It can reveal distinct metabolic profiles of brain tumors although the accurate analysis and classification of different spectra remains a challenge. In this study, the pattern recognition method partial least squares discriminant analysis (PLS-DA) was used to classify 11.7 T ¹H MRS spectra of brain tissue extracts from patients with brain tumors into four classes (high-grade neuroglial, low-grade neuroglial, non-neuroglial, and metastasis) and a group of control brain tissue. PLS-DA revealed 9 metabolites as the most important in group differentiation: γ-aminobutyric acid, acetoacetate, alanine, creatine, glutamate/glutamine, glycine, myo-inositol, N-acetylaspartate, and choline compounds. Leave-one-out cross-validation showed that PLS-DA was efficient in group characterization. The metabolic patterns detected can be explained on the basis of previous multimodal studies of tumor metabolism and are consistent with neoplastic cell abnormalities possibly related to high turnover, resistance to apoptosis, osmotic stress and tumor tendency to use alternative energetic pathways such as glycolysis and ketogenesis.

Development of gluten-free cookie from medicinal plants (Guaraná - Paullinea cupana and Catuaba - Anemopaegma mirandum) aiming at copper, iron, and zinc supplementation

Two flavors of cookies were developed (savory and peppery) containing a mixture of plants such as "guaraná" (Paullinia cupana) and "catuaba" (Anemopaegma mirandum). A test of acceptance and buying intention was applied to 48 consumers through a structured hedonic scale of 9 points. Afterwards, the centesimal compositions of these cookies were obtained as well as their total contents of copper, iron, and zinc through the method of atomic absorption spectrometry with flame. Sensorial tests indicated that the cookies presented good acceptance with potential to sensorial growth. The amount of fibers in the samples, 3 g/100 g, surpassed expectations since the product was not invented with the intention of being a source of this nutrient. The total amount of copper (0.41 mg.100 g-1), iron (4.50 mg.100 g-1), and zinc (1.32 mg.100 g-1) was considered good. The cookies produced can be considered good sources of fibers, copper, iron, and zinc. Furthermore, they are beneficial to people affected by celiac disease because they lack gluten. They also present functional properties. In addition, the medicinal plants used are considered energetic.

Biosensor for determination of glucose in real samples of beverages

A biosensor was developed for spectrophotometric determination of glucose concentrations in real samples of orange juice energetic drinks, and sport drinks. The biosensor consisted of glucose oxidase (GOD) and horseradish peroxidase (HRP) immobilized onto polyaniline activated with glutaraldehyde (PANIG). Immobilization parameters were optimized for GOD, and maximum immobilization yield was 16% when 5.0 mg of PANIG and 8.9 U prepared in 0.1 mol.L-1 sodium phosphate buffer (pH 7.0) reacted for 60 minutes at 4 °C with gentle stirring. The linear operational range for glucose determination using optimized operational parameters was between 0.05 and 6.0 mg.mL-1 with a very good reproducibility of response. The results obtained in the biosensor were compared with those obtained using free enzymes (commercial kits) and then validated through statistical analysis using the Tukey test (95% confidence interval).

Mangaba (Hancornia speciosa Gomez) ice cream prepared with fat replacers and sugar substitutes

The effect of replacing shortening and sugar on the physical and chemical properties of mangaba ice cream and its acceptability were evaluated. Ice cream formulations were tested with the following fat replacers: Selecta Light, Litesse, and Dairy Lo and the following sugar substitutes: Lactitol and Splenda. All formulations were subjected to physical, chemical, and microbiological analyses and evaluated by acceptability tests. In the sensory analysis, it was observed a larger acceptance of the formulations containing Selecta Light (SL) and the combination of Litesse, Lactiol, and Splenda (LLS). The largest reduction in total energetic value (50%) was observed in the formulation LLS. The use of fat and/or sugar substitutes caused a reduction in the air incorporation (overrun) and affected viscosity. The highest melting speed was observed in the formulation with Dairy-Lo, Lactitol, and Splenda. All formulations showed good levels of global acceptability and appearance. The substitution of shortening for fat replacers caused a reduction in air incorporation and changes in ice-cream viscosity. The low-fat mangaba ice-cream elaborated with Selecta Light was the best formulation in terms of viscosity and air incorporation when compared with the control. It also showed a good level of acceptability and low fat content.

Study of thermodynamic water properties and moisture sorption hysteresis of mango skin

The equilibrium moisture content for adsorption and desorption isotherms of mango skin was determined using the static gravimetric method at temperatures of 20, 26, 33, 38 and 44 oC in the 0.056 to 0.873 water activity range. Both sorption curves show a decrease in equilibrium moisture content as the temperature increasing. The hysteresis effect was observed at constant water activity. The Guggenheim, Anderson, and de Boer (GAB) model presented the best fitting accuracy among a group of models and was used to determine the thermodynamic properties of water sorption. Integral enthalpy and integral entropy areas showed inverted values for the adsorption and desorption isotherms over the wide range of water activity studied. These values confirm, in energetic terms, the difference between adsorption and desorption isotherms observed in the hysteresis phenomenon. Finally, the Gibbs free energy revealed that the sorption process was spontaneous for both sorption isotherms.