Estudo das estruturas terciária e quaternária de proteínas por espalhamento de raios X a baixos ângulos integrado a técnicas de modelagem

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Espumas cerâmicas produzidas pela conjugação dos processos sol-gel, aeração e emulsificação

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudos estruturais com fosfolipases A2 isoladas de venenos de serpentes dos gêneros Bothrops e Crotalus

Pós-graduação em Ciências Biológicas (Genética) - IBB

Desenvolvimento e caracterização de sistemas líquido-cristalinos para aplicação tópica de metotrexato: estudos de liberação, retenção e permeação in vitro

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structure and thermal behavior of PMMA-polysilsesquioxane organic-inorganic hybrids

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Matrizes híbridas siloxano-poliéter incorporadas com argila montmorilonita para liberação controlada de fármaco

Pós-graduação em Química - IQ

SAXS Studies of the Endoglucanase Cel12A from Gloeophyllum trabeum Show Its Monomeric Structure and Reveal the Influence of Temperature on the Structural Stability of the Enzyme

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aplicações clássicas da técnica de espalhamento de raios-x a baixo ângulo em materiais nanoestruturados

The small angle X-ray scattering (SAXS) technique has been used with very much versatility and success in the structural characterization of nanostructured materials. The present work deals with a study of the principles of the SAXS technique and of some classical models employed in the structural characterization of nanostructured materials. Particularly, the study of the models and of the associated methodologies is applied to a set of samples of silica gels, of varied typical structures, prepared in the Laboratório de Novos Materiais of the Departamento de Física of the IGCE. The work discusses in an introductory chapter the principles of the SAXS technique and the foundation of classical models often used in the structural characterization of materials. The classical models and the associated methodologies were applied to a variety of silica gel structures. The studies include: i) the scattering from a system of particles - Guinier's law; ii) the asymptotic scattering from a two-phase system - Porod's law; iii) systematic deviation from Porod's law - Surface Fractal; iv) heterogeneities in solids with random size distribution - DAB Model; and v) the scattering from mass fractal structures. The analyses were carried out from experimental SAXS data obtained in several opportunities at the Laboratório Nacional de Luz Síncrotron (LNLS)

Structural properties of cerium doped siloxane-PMMA hybrid coatings with high anticorrosive performance

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relationship between composition and organizational levels of nanostructured systems formed by Oleth 10 and PPG-5-Ceteth-20 for potential drug delivery

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Sistemas precursores de cristais líquidos mucoadesivos para administração bucal de curcumina no tratamento do câncer bucal

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development and in vitro skin delivery of dexamethasone acetate-loaded surfactant-based systems

Topical corticosteroids, e.g., dexamethasone acetate (DMA), are extensively used to treat cutaneous inflammatory disorders even though their use is correlated with potential local and systemic side effects. The objective of this study was to develop and test the topical delivery of DMA-loaded surfactant based systems in vitro; these studies could guarantee a suitable delivery and therapeutic efficacy, as well as minimize DMA's side effects. A phase diagram was constructed using polyoxypropylene (5) polyoxyethylene (20) cetyl alcohol as the surfactant (S), isopropyl myristate as the oil phase (O) and water (W). The systems were characterized using polarization light microscopy (PLM), as well as rheological and small angle X-ray scattering (SAXS) measurements. Depending on the concentration of the constituents, it was possible to obtain microemulsions (MEs) and liquid crystalline mesophases (lamellar and hexagonal). These types of arrangement were verified using PLM measurements. The SAXS results revealed that increasing the W/S ratio led to ME, as well as lamellar (LAM) and hexagonal (HEX) arrangements. The MEs displayed typical Newtonian behavior while the LAM and HEX phases exhibited pseudoplasticity and plasticity, respectively. The MEs displayed excellent drug solubilization that was approximately 10-fold higher than was observed with the individual components. The in vitro cutaneous permeation studies using pig ear skin and analysis of the mechanical parameters (hardness, compressibility, cohesiveness and adhesiveness) were carried out with a HEX phase and O/W emulsion. The HEX phase achieved better drug permeation and retention in the skin while its mechanical properties were suitable for skin administration. PPG-5-CETETH-20-based systems may be a promising platform delivering DMA and other topical corticosteroids through the skin.

Cimentos bioativos injetáveis funcionalizados com peptídeo osteogênico para reparação óssea

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Interaction of cationic water-soluble meso-tetrakis(4-N-methylpyridiniumyl)porphyrin (TMPyP) with ionic and nonionic micelles: aggregation and binding

The equilibrium of meso-tetrakis(4-N-methylpyridiniumyl)porphyrin (TMPyP) in aqueous solution in the presence of surfactants was studied by optical spectroscopic techniques and SAXS (small angle X-ray scattering). Anionic SDS (sodium dodecyl sulfate), zwitterionic HPS (N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate) and nonionic TRITON X-100 (t-octyl-phenoxypolyethoxyethanol), surfactants were used. TMPyP is characterized by a protonation equilibrium with a pK(a) around 1.0, associated with the diacid-free base transition, and a second pK(a) around 12.0 related with the transition between the free base and the monoanion form. Three independent species were observed for TMPyP at pH 6.0 as a function of SDS concentration: free TMPyP, TMPyP-SDS aggregates and porphyrin monomer bound to micelles. For HPS and TRITON X-100, the equilibrium of TMPyP as a function of pH is quite similar to that obtained in pure aqueous solution: no aggregation was observed, suggesting that electrostatic contribution is the major factor in the interaction between TMPyP and surfactants. SAXS data analysis demonstrated a prolate ellipsoidal shape for SDS micelles; no significant changes in shape and size were observed for SDS-TMPyP co-micelles. Moreover, the ionization coefficient, alpha, decreases with the increase of the porphyrin concentration, suggesting the ""screening"" of the anionic charge of SDS by the cationic porphyrin. These results are consistent with optical absorption, fluorescence and RLS (resonance light scattering) spectroscopies data, allowing to conclude that neutral surfactants present a smaller interaction with the cationic porphyrin as compared with an ionic surfactant. Therefore, the interaction of TMPyP with the ionic and nonionic surfactants is predominantly due to the electrostatic contribution. Copyright (c) 2008 Society of Porphyrins & Phthalocyanines.

Variations in Structure Explain the Viscometric Behavior of AOT Microemulsions at Low Water/AOT Molar Ratios

The viscosity of AOT/water/decane water-in-oil microemulsions exhibits a well-known maximum as a function of water/AOT molar ratio, which is usually attributed to increased attractions among nearly spherical droplets. The maximum can be removed by adding salt or by changing the oil to CCl4. Systematic small-angle X-ray scattering (SAXS) measurements have been used to monitor the structure of the microemulsion droplets in the composition regime where the maximum appears. On increasing the droplet concentration, the scattering intensity is found to scale with the inverse of the wavevector, a behavior which is consistent with cylindrical structures. The inverse wavevector scaling is not observed when the molar ratio is changed, moving the system away from the value corresponding to the viscosity maximum. It is also not present in the scattering from systems containing enough added salt to essentially eliminate the viscosity maximum. An asymptotic analysis of the SAXS data, complemented by some quantitative modeling, is consistent with cylindrical growth of droplets as their concentration is increased. Such elongated structures are familiar from related AOT systems in which the sodium counterion has been exchanged for a divalent one. However, the results of this study suggest that the formation of non-spherical aggregates at low molar ratios is an intrinsic property of AOT.