Caracterização físico-química de sistemas micelares

The process of adsorption and micellization of the surfactants sodium dodecyl sulfate, dodecylammonium chloride and hexaethylene glycol mono-n-dodecyl ether in water-air interface has been studied using measurements of surface tension in aqueous media and NaCl 0.1 mol/L in temperatures of 25, 33 and 40 °C. From these data, critical micelle concentrations and thermodynamic parameters of micellization and adsorption were determined in order to elucidate the behaviors of micellization and adsorption for these surfactants in the proposed medium. For the determination of the thermodynamic parameters of adsorption we utilized the equations of isotherms of Langmuir and Gibbs. Γmáx values determined by the different equations were correlated to the explanation of results. Temperature and salinity were analyzed in terms of their influence on the micellization and adsorption process, and the results were explained based on intermolecular interactions. The values of Gmic have confirmed that the micelle formation for the surfactants studied occurs spontaneously

Avaliação funcional e estrutural de um novo peptídeo antimicrobiano do escorpião Tityus stigmurus

In Brazil, there is a high incidence of venomous animals. Among them, scorpions are highlighted by their medical importance, and for being their venom a source of several molecules with biological and pharmacological activity not yet fully understood, including several bioactive peptides. Antimicrobial peptides (AMPs) are components of the immune system in prokaryotes and eukaryotes, used in the first line of defense against microorganisms. In the present study, we characterized the first PAM previously identified through transcriptome of the venom gland of the scorpion Tityus stigmurus, named Stigmurin. The characteristics of Stigmurin were investigated by computational modeling and construction of dendrogram. In vitro tests investigated the antibacterial, antifungal, haemolytic and cytotoxic effects of crude venom and Stigmurin. In addition, the structural characteristics of Stigmurin were investigated by circular dochroism in water, 2, 2 , 2- trifluoethanol (TFE) and sodium dodecyl sulfate (SDS) and the models were refined by molecular dynamics simulations. The results showed that the selected sequence encodes a mature protein of 17 amino acid residues and the dendrogram reveals a case of convergent evolution. The crude venom showed no antimicrobial activity, however, Stigmurin exhibited a broad spectrum of antibacterial activity, with minimal inhibitory concentrations (MIC) ranging from 31.25 and 250 µg/mL for different strains, while the hemolytic activity at these concentrations was low. In cytotoxicity studies, the crude venom was unable to reduce cell viability in VERO E6 cells; in contrast, its activity in SiHa cells was significantly higher, corresponding to IC50 of 3.6 µg/mL. For Stigmurin the concentration sable to decrease cell viability of Vero E6 and SiHa cells in 50% were 275.67 µg/mL and 212.54 µg/mL, respectively. The dichroism spectra revealed the conformational flexibility, with predominating extended and β–sheet structures, as well as a remark able renaturation ability. The results suggest that Stigmurin could be considered as a potential antiinfective drug

Purificação e caracterização de uma ß-N-acetillhexosaminadase extraída do mamífero marinho Sotalia fluviatilis

This report shows 2232 times purification of a βNAcetylhexosaminidase from hepatic extracts from the sea mammal Sotalia fluviatilis homogenate with final recovery of 8,4%. Sequenced steps were utilized for enzyme purification: ammonium sulfate fractionation, Biogel A 1.5 m, chitin, DEAESepharose and hydroxyapatite chromatographies. The protein molecular mass was estimated in 10 kDa using SDSPAGE and confirmed by MALDITOF. It was found to have an optimal pH of 5.0 and a temperature of 60°C. Using pnitrophenylNAcetylβDglycosaminide apparent Km and Vmax values were of 2.72 mM and 0.572 nmol/mg/min, respectively. The enzyme was inhibited by mercury chloride (HgCl2) and sodium dodecil sulfate (SDS)