Robust tori-like Lagrangian coherent structures

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

Molecular structures and vibrational frequencies for [PdX2(tdmPz)] (X = Cl-, SCN-): A DFT study

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

New antifungal terpenoid glycosides from Alibertia edulis (Rubiaceae)

Phytochemical investigation from the stems of Alibertia edulis led to the isolation and identification of a new iridoid 6 beta-hydroxy-7-epigardoside methyl ester (1) and a new saponin 3 beta-O-[alpha-L-rhamnopyranosyl-(1 -> 2)-O-beta-D-glucopyranosyl-(1 -> 2)-O-beta-D-glucopyranosyl]-28-O-beta-D-glucopyranoside pomolate (2), along with three known compounds, shanzhiside methyl ester (3), ixoside (4), and 3,4,5-trimethoxyphenyl 1-O-beta-D-apiofuranosyl-(1 -> 6)-O-beta-D-glucopyranoside (5). The structures of 1 and 2 were established on the basis of their spectroscopic data. Iridoid 1 and saponin 2 exhibited moderate inhibitory activities against Candida albicans and C krusei in a dilution assay.

Natural products from Brazilian biodiversity as a source of new models for medicinal chemistry

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

New insights into the in vitro organogenesis process: the case of Passiflora

We present evidences that ultrastructural electron microscope findings are valuable ways to understand the in vitro regeneration process, in particular in the yellow passion fruit. Shoot-regeneration was induced in hypocotyl and leaf-derived explants using 4.44 mu M BAP, and the entire organogenic process was analyzed using conventional histology, scanning and transmission electronic microscopy. Both direct and indirect regeneration modes were observed in hypocotyl explants, but only direct regeneration occurred in leaf-derived cultures. In the direct pathway from both explant types, meristemoids developed into globular structures, here called protuberances. The peripheral meristematic layers of the protuberances displayed ultrastructural characteristics indicative of a high metabolic activity, and only these cells originated shoots and leaf primordia, the latter being frequent when leaf explants were used. Moreover, the peripheral cells of the protuberances derived from leaf explants lost adhesion during the culture, diminishing the regeneration rates. We recommend the use of hypocotyls as a source of explant to obtain shoots as well as a genetic transformation system for the yellow passion fruit. However, the direct pathway is preferred because a type of amitosis occurred in the peripheral cells of hypocotyl-derived calli, which has the potential to result in genetic instability of the regenerating plants/tissue.

Fabrication and analysis of self-assembled photonic crystals structures

This paper presents the fabrication and analysis of a three-dimensional FCC photonic crystal (PhC) based on a self-assembly synthesis of monodispersive latex spheres. Experimental optical characterization, achieved by measurements of the specular reflectance under variable angles, indicated the clear presence of a Bragg diffraction pattern. Results are further explored by theoretical calculations based on the Finite Difference Time Domain (FDTD) method to determine the full PhC band structure.

Chitinolytic activities in the gut of Aedes aegypti (Diptera : Culicidae) larvae and their role in digestion of chitin-rich structures

Mosquito larvae are believed to be capable of digesting chitin, an insoluble polysaccharide of N-acetylglucosamine, for their nutritional benefit. Studies based on physiological and biochemical assays were conducted in order to detect the presence of chitinase activities in the gut of the detritus-feeding Aedes aegypti larvae. Larvae placed for 24 h in suspensions of chitin azure were able to digest the ingested chitin. Semi-denaturing PAGE using glycol chitin and two fluorogenic substrate analogues showed the presence of two distinct chitinase activities: an endochitinase that catalyzed the hydrolysis of chitin and an endochitinase that cleaved the short substrates [4MU(GlcNAc)(3)] and [4MU(GlcNAc)(2)] that hydrolyzed the chitobioside [4MU(GlcNAc)(2)]. The endochitinase had an extremely broad pH-activity against glycol chitin and chitin azure, pH ranging from 4.0 to 10.0. When the substrate [4MU(GlcNAc)(3)] was used, two activities were observed at pH ranges 4.0-6.0 and 8.0-10.0. Chitinase activity against [4MU(GlcNAc)(3)] was detected throughout the gut with the highest specific activity in the hindgut. The pH of the gut contents was determined by observing color changes in gut after feeding the larvae with color indicator dyes. It was observed a correlation between the pH observed in the gut of feeding larvae (pH 10-6.0) and the optimum pH for gut chitinase activities. In this work, we report that gut chitinases may be involved in the digestion of chitin-containing structures and also in the partial degradation of the chitinous peritrophic matrix in the hindgut. (C) 2003 Elsevier B.V. All rights reserved.

mer-[RuCl3(P-P)H2O] (P-P=dppb or diop) as a starting material for the synthesis of binuclear complexes. Crystallographic structures of [(dppb)ClRu-mu(Cl)(3)-RuCl(dppb)] and [(eta(6)-C6H6)Ru-mu(Cl)(3)-RuCl(dppb)]. Imine hydrogenation using mono- and binuclear ruthenium complexes

The reactivity of the mer-[RuCl3(dppb)H2O] complex (1) with di-hydrogen shows that the products formed depend on the conditions of the reaction, i.e., solvents and presence or absence of a base. The new mixed-valence complexes [(diop)ClRu-(h-Cl)(3)-RuCl(dppb)] (3), [(binap)CIRu-(p-Cl)(3)-RuCl(dppb)] (4), [(PPh3)(2)ClRu-(mu-Cl)(3)-RuCl(dppb)] (6), [(dppn)ClRu-(mu-Cl)(3)-RuCl(dppb)] (7), [(P-ptol(3))(2)ClRu-(mu-Cl)(3)-RuCl(dppb)] (8), [(SbPh3)(2)ClRu-(mu-Cl)(3)-RuCl(dppb)] (9), [(eta(6)-C6H6)Ru-(mu-Cl)(3)-RuCl(dppb)] (11) and the known mixed-valence [(dppb)CIRu-(mu-Cl)(3)-RuCl(dppb)] (5) and [(diop)ClRu-(mu-Cl)(3)-RuCl(diop)] (10) were synthesized from complexes (1) or (2) using a methodology developed in our research group. The known complexes [(dppb)ClRu-(mu-Cl)(2)-RuCl(dppb)] (12), [(dppb)(CO)Ru-(mu-Cl)(3)-RuCl(dppb)] (13) and [H2NEt2][(dppb)ClRu-(mu-Cl)(3)-RuCl(dppb)] (14) were synthesized by changing the reaction conditions between mer-[RuCl3(dppb)H2O] (1) and dihydrogen. The crystal structures of (5) and (11) were determined by single-crystal X-ray diffraction. Some of the complexes described here are effective pre-catalysts for the hydrogenation of imines. Preliminary results on the homogeneous hydrogenation of the imines Ph-CH2-N=CH-Ph and Ph-N=CH-Ph are presented. (C) 2004 Elsevier Ltd. All rights reserved.

Structural analysis of Canavalia maritima and Canavalia gladiata lectins complexed with different dimannosides: New insights into the understanding of the structure-biological activity relationship in legume lectins

Plant lectins, especially those purified from species of the Legummosae family, represent the best studied group of carbohydrate-binding proteins. The legume lectins from Diocleinae subtribe are highly similar proteins that present significant differences in the potency/ efficacy of their biological activities. The structural studies of the interactions between lectins and sugars may clarify the origin of the distinct biological activities observed in this high similar class of proteins. In this way, this work presents a crystallographic study of the ConM and CGL (agglutinins from Canavalia maritima and Canavalia gladiata, respectively) in the following complexes: ConM/ CGL:Man(alpha 1-2)Man(alpha 1-0)Me, ConM/CGL:Man(alpha 1-O)Man(alpha 1-O)Me and ConM/CGL:Man(alpha 1-4)Man(alpha 1-O)Me, which crystallized in different conditions and space group from the native proteins.The structures were solved by molecular replacement, presenting satisfactory values for R-factor and R-factor. Comparisons between ConM, CGL and ConA (Canavalia ensiformis lectin) binding mode with the dimannosides in subject, presented different interactions patterns, which may account for a structural explanation of the distincts biological properties observed in the lectins of Diocleinae subtribe. (C) 2007 Elsevier B.V. All rights reserved.

Isolation and structure elucidation of two new flavonoid glycosides from the infusion of Maytenus aquifolium leaves. Evaluation of the antiulcer activity of the infusion

Droplet countercurrent chromatography and high-performance liquid chromatography fractionation of the aqueous infusion from Maytenus aquifolium Martius leaves afforded two flavonoid tetrasaccharides: quercetin 3-O-alpha-L-rhamnopyranosyl(1-->6)-O-[beta-D-glucopyranosyl(1-->3)-O-alpha-L-rhamnopranosyl( 1-->2)-O-beta-D-galactopyranoside and kaempferol 3-O-alpha-L-rhamnopyranosyl(1-->6)-O-[beta-D-glucopyranosyl( 1-->3)-O-alpha-L-rhamnopyranosy(1-->2-2)-O-beta-D-galactopyranoside. All structures were elucidated by spectroscopic methods. Pharmacological essays of the infusion showed antiulcer activity in rats.

Studies on the constituents of a Brazilian folk infusion. Isolation and structure elucidation of new triterpene saponins from Ilex amara leaves

The isolation of three new triterpene saponins 3beta-O-beta-D-glucopyranosyl-(1-->3)-alpha-L-2-O-acetylara-binopyranosylolean-12-en-28-oic acid 28-O-beta-D-glucopyranosyl ester (2), 3beta-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-O-arabinopyranosylurs-12-en-28-oic acid (3), and 3beta-O-beta-D-glucopyranosyl-(1-->2)-beta-D-O-galactopyranosylurs-12-en-28-oic acid (4) together with five known saponins and one flavonoid glycoside from the aqueous infusion of flex amara (Vellozo) Loes. leaves is reported. All structures were elucidated by spectroscopic methods, including the concerted application of one-dimensional (H-1, TOCSY, C-13, and C-13 DEPT NMR) and two-dimensional NMR techniques (DQF-COSY, HSQC, and HMBC).

New antioxidant C-glucosylxanthones from the stems of Arrabidaea samydoides

Three new C-glucosylxanthones, 2-(2'-O-trans-caffeoyl)-C-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone (1), 2-(2'-O-trans-cinnamoyl)-C-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone (2), and 2-(2'-O-trans-coumaroyl)-C-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone (3), were isolated from the stems of Arrabidaea samydoides, in addition to three known C-glucosylxanthones, mangiferin (4), 2-(2'-O-benzoyl)-C-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone (5), and muraxanthone (6). Their chemical structures were assigned on the basis of MS and 1D and 2D NMR experiments. Xanthones 1-6 showed moderate free radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) as well as antioxidant activity evidenced by redox properties measured on ElCD-HPLC.

Preparation of new glass systems by the polymeric precursor method for dental applications

Glass ionomer cements (GICs) are largely employed in Dentistry for several applications, such as luting cements for the attachment of crowns, bridges, and orthodontic brackets as well as restorative materials. The development of new glass systems is very important in Dentistry to improve of the mechanical properties and chemical stability. The aim of this study is the preparation of two glass systems containing niobium in their compositions for use as GICs. Glass systems based on the composition SiO2,Al2O3-Nb2O5-CaO were prepared by chemical route at 700degreesC. The XRD and DTA results confirmed that the prepared materials are glasses. The structures of the obtained glasses were compared to commercial material using FTIR, Al-27 and Si-29 MAS-NMR. The analysis of FTIR and MAS-NMR spectra indicated that the systems developed and commercial material are formed by SiO4 and AlO4 linked tetrahedra. These structures are essential to get the set time control and to have cements. These results encourage further applications of the experimental glasses in the formation of GICs. (C) 2004 Elsevier B.V. All rights reserved.

A Non-Destructive Testing Based on Electromagnetic Measurements and Neural Networks for the Inspection of Concrete Structures

This paper presents a new non-destructive testing (NDT) for reinforced concrete structures, in order to identify the components of their reinforcement. A time varying electromagnetic field is generated close to the structure by electromagnetic devices specially designed for this purpose. The presence of ferromagnetic materials (the steel bars of the reinforcement) immersed in the concrete disturbs the magnetic field at the surface of the structure. These field alterations are detected by sensors coils placed on the concrete surface. Variations in position and cross section (the size) of steel bars immersed in concrete originate slightly different values for the induced voltages at the coils.. The values for the induced voltages were obtained in laboratory tests, and multi-layer perceptron artificial neural networks with Levemberg-Marquardt training algorithm were used to identify the location and size of the bar. Preliminary results can be considered very good.

Designing spatial correlation of quantum dots: towards self-assembled three-dimensional structures

Buried two-dimensional arrays of InP dots were used as a template for the lateral ordering of self-assembled quantum dots. The template strain field can laterally organize compressive (InAs) as well as tensile (GaP) self-assembled nanostructures in a highly ordered square lattice. High-resolution transmission electron microscopy measurements show that the InAs dots are vertically correlated to the InP template, while the GaP dots are vertically anti-correlated, nucleating in the position between two buried InP dots. Finite InP dot size effects are observed to originate InAs clustering but do not affect GaP dot nucleation. The possibility of bilayer formation with different vertical correlations suggests a new path for obtaining three-dimensional pseudocrystals.