Repositório RCAAP

In this article are described dendritic structures containing photoactive groups at the surface or in the core. The observed supramolecular effects can be attributed to the nature of the photoactive group and their location in the dendritic architecture. The peripheric azobenzene groups in these dendrimeric compounds can be regarded as single residues that retain the spectroscopic and photochemical properties of free azobenzene moiety. The E and Z forms of higher generation dendrimer, functionalized with azobenzene groups, show different host ability towards eosin dye, suggesting the possibility of using such dendrimer in photocontrolled host-guest systems. The photophysical properties of many dendritic-bipyridine ruthenium complexes have been investigated. Particularly in aerated medium more intense emission and a longer excited-state lifetime are observed as compared to the parent unsubstituted bipyridine ruthenium complexes. These differences can be attributed to a shielding effect towards dioxygen quenching originated by the dendritic branches.

Multiple uses for synthetic cationic liposomes composed of dioctadecyldimethylammonium bromide (DODAB) bilayer vesicles are presented. Drugs or biomolecules can be solubilized or incorporated in the cationic bilayers. The cationic liposomes themselves can act as antimicrobial agents causing death of bacteria and fungi at concentrations that barely affect mammalian cells in culture. Silica particles or polystyrene microspheres can be functionalized by coverage with DODAB bilayers or phospholipid monolayers. Negatively charged antigenic proteins can be carried by the cationic liposomes which generate a remarkable immunoadjuvant action. Nucleotides or DNA can be physically adsorbed to the cationic liposomes to be transferred to mammalian cells for gene therapy. An overview of the interactions between DODAB vesicles and some biomolecules or drugs clearly points out their versatility for useful applications in a near future.

Two-dimensional inorganic networks can shown intracrystalline reactivity, i.e., simple ions, large species as Keggin ions, organic species, coordination compounds or organometallics can be incorporated in the interlayer region. The host-guest interaction usually causes changes in their chemical, catalytic, electronic and optical properties. The isolation of materials with interesting properties and making use of soft chemistry routes have given rise the possibility of industrial and technological applications of these compounds. We have been using several synthetic approaches to intercalate porphyrins and phthalocyanines into inorganic materials: smectite clays, layered double hydroxides and layered niobates. The isolated materials have been characterized by elemental and thermal analysis, X-ray diffraction, surface area measurements, scanning electronic microscopy, electronic and resonance Raman spectroscopies and EPR. The degree of layer stacking and the charge density of the matrices as well their acid-base nature were considered in our studies on the interaction between the macrocycles and inorganic hosts.

The importance of copper as an essential element can be estimated by the wide range of copper proteins and enzymes playing different roles in biological systems. In the last decades many bioinorganic studies were developed on mimetic complexes of copper-dependent proteins, in order to verify the interrelations between structural and functional properties of active copper centers. Among the most studied copper ion ligand, diimine compounds have deserved special attention due their flexibility, facility of preparation, and ability to stabilize both oxidation states of this metal. In our laboratory, we have been investigating some Schiff base copper complexes as mimics of different proteins, with emphasis on functional aspects, trying to elucidate mechanisms of reaction, based on proposed intermediary species, in addition to molecular shapes. Particularly, mimics of the copper-zinc superoxide dismutase, and of monooxigenases and oxidases exhibiting dicopper sites are discussed in this work.

New materials porphyrinosilica and metalloporphyrinosilica template have been obtained by a sol-gel processing where functionalyzed porphyrins and metalloporphyrins "building blocks" were assembled into a three-dimensional silicate network. The optimized conditions for preparation of these materials are revised. The monomer precursors porphyrinopropylsilyl and metalloporphyrinopropylsilyl preparation reactions and subsequent one pot sol-gel processing with tetraethoxysilane are discussed. In the case of metalloporphyrins the nitrogen base coordinates to the central metal and acts as a template in the molecular imprinting technique. UV-visible absorption spectroscopy, thermogravimetric analysis, electron paramagnetic resonance, nuclear magnetic spectra, infrared spectra, luminescence spectra, surface area and electron spectroscopy imaging of the materials are used to characterize the prepared materials. The catalytic activities of these metalloporphyrinosilica- template are compared.

Supramolecular photochemistry as well as solar cells are fascinating topics of current interest in Inorganic Photochemistry and very active research fields which have attracted wide attention in last two decades. A brief outline of the investigations in these fields carried out in our Laboratory of Inorganic Photochemistry and Energy Conversion is given here with no attempt of an exhaustive coverage of the literature. The emphasis is placed on recent work and information on the above mentioned subjects. Three types of supramolecular systems have been the focus of this work: (i) cage-type coordination compounds; (ii) second-sphere coordination compounds, exemplified by ion-pair photochemistry of cobalt complexes and (iii) covalently-linked systems. In the latter, modulation of the photoluminescence and photochemistry of some rhenium complexes are discussed. Solar energy conversion and development of thin-layer photoelectrochemical solar cells based on sensitization of nanocrystalline semiconductor films by some ruthenium polypyridyl complexes are presented as an important application that resulted from specifically engineered artificial assemblies.

The formation and characterization of self-assembled films of zirconium phosphonate / N,N'-di(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (DPN) is presented. The films were produced on glass substrates by deposition of alternating layers of Zr+4 and DPN. Films containing up to 16 layers on each side of the substrate were obtained and monitored by absorption spectroscopy and ellipsometry. When irradiated, the initially colorless films turned to a persistent pinky color reminiscent of that of DPN anion radical. These films are a promising material to the development of photovoltaic devices.

Trypanosomatid protozoan parasites express an aggressive strategy of parasitism by infecting host macrophages and inducing extensive T-lymphocyte activation. One goal of such strategy is to drive the immune response of genetically susceptible hosts to a state of unresponsiveness regarding parasite killing. Unresponsiveness is achieved through different mechanisms, depending on the parasite species. In this brief review, recent findings on the molecular and cellular bases of the parasites' exploitation of host immune responses are discussed.

Neonatal lupus erythematosus (NLE) is an auto-immune disease related to systemic lupus erythematosus (SLE). Unlike SLE it is not a spontaneous syndrome but rather an acquired one. In NLE the most common disease manifestations are a transient cutaneous lesion and cardiac conduction disturbances. The cutaneous lesions and other non-cardiac manifestations of NLE are transient and disappear about six months after birth, at the time when maternal antibodies disappear from the neonatal circulation. This fact suggests that maternal antibodies may cross the placenta leading to an inflamatory reaction in the fetal tissues. NLE is the principal cause of atria-ventricular block, when it is not associated with congenital birth defects. All the clinical studies to date correlate the heart block in NLE with the presence of certain types of circulating maternal antibodies, against the Ro/SSA nuclear proteins, in the serum of the newborn. In this paper we discuss animal models that have been developed by our and others groups to study the participation of the anti-Ro/SSA antibodies in the pathogenesis of the cardiac conduction blockades that occur in NLE.

Microglial cells within the developing central nervous system (CNS) originate from mesodermic precursors of hematopoietic lineage that enter the nervous parenchyma from the meninges, ventricular space and/or blood stream. Once in the nervous parenchyma, microglial cells increase in number and disperse throughout the CNS; these cells finally differentiate to become fully ramified microglial cells. In this article we review present knowledge on these phases of microglial development and the factors that probably influence them.

We use equivariant geometry methods to study and classify zero scalar curvature O(p + 1) x O(p + 1)-invariant hypersurfaces in R2p+2 with p > 1.

We study the asymptotic behavior of curvature and prove that the integral of curvature along a geodesic without conjugate points is nonpositive and some generalizations of Myers theorem and Cohn-Vossen's theorem. Some applications are also given.

We develop a convenient surface theory in E³ in order to apply it to the class of the surfaces invariant under a one-parameter group of isometries of E³. In this way we derive intrinsic characterizations along with several results of subclasses of this class of surfaces that satisfy certain preassigned properties. In the process all results are also effortlessly derived. Among these subclasses are those with surfaces; of constant mean curvature, of constant Gaussian curvature, isothermic, with constant difference or ratio of the principal curvatures.

Proca's equations for two types of fields in a Dirac's æther with electric conductivity sigma are solved exactly. The Proca electromagnetic fields are assumed with cylindrical symmetry. The background is a static, curved spacetime whose spatial section is homogeneous and has the topology of either the three-sphere S³ or the projective three-space P³. Simple relations between the range of Proca field lambda, the Universe radius R, the limit of photon rest mass mgamma and the conductivity sigma are written down.

Four DNA datasets were combined in tandem (6700 bp) and Maximum parsimony and Neighbor-Joining analyses were performed. The results suggest three groups emerging almost at the same time: Atelidae, Pitheciidae and Cebidae. The total analysis strongly supports the monophyly of the Cebidae family, grouping Aotus, Cebus and Saimiri with the small callitrichines. In the callitrichines, the data link Cebuela to Callithrix, place Callimico as a sister group of Callithrix/Cebuella, and show Saguinus to be the earliest offshoot of the callitrichines. In the family Pithecidae, Callicebus is the basal genus. Finally, combined molecular data showed congruent branching in the atelid clade, setting up Alouatta as the basal lineage and Brachyteles-Lagothrix as a sister group and the most derived branch. Two major points remain to be clarified in the platyrrhine phylogeny: (i) what is the exact branching pattern of Aotus, Cebus, Saimiri and the small callitrichines, and (ii), which two of these three lineages, pitheciines, atelines or cebids, are more closely related?

The interaction between each one of Trichomonas vaginalis and Tritrichomonas foetus with their hosts is a complex process in which components associated to the cell surfaces of both parasites and host epithelial cells, and also to soluble components found in vaginal/urethral secretions, are involved. Either cytoadhesion or the cytotoxicity exerted by parasites to host cells can be dictated by virulence factors such as adhesins, cysteine proteinases, laminin-binding proteins, integrins, integrin-like molecules, a cell detachment factor, a pore-forming protein, and glycosidases among others. How trichomonads manipulate informations from the extracellular medium, transduce such informations, and respond to them by stimulating the activities of some surface molecules and/or releasing enzymes are the aspects concerning trichomonal virulence which are here briefly reviewed and discussed.

This paper describes a possible fossil egg proceeding from the Bauru Group, Late Cretaceous of Paraná Basin, Brazil. External morphology, dimensions, texture and shell ornamentation examined under electron microscopy show close resemblance to the Recent podocnemidid chelonian eggs. Association with bony material in the outcrop suggests that it is related to a species of Podocnemis. Computerized tomography reveals a high density outer region corresponding to the shell component layers, and successive layers with decreasing density towards the nucleus. An area of high density in the central region may represent remains of an embryo.

Sandbox experiments with different boundary conditions demonstrate that antiformal stacks result from a forward-breaking thrust sequence. An obstacle blocks forward thrust propagation and transfers the deformation back to the hinterland in a previously formed true duplex. In the hinterland, continued shortening causes faults to merge toward the tectonic transport direction until the older thrusts override the younger thrusts. In experiments using thin sand layers or high basal friction, shortening is accommodated by a cyclic process of thrusting, back rotation of the newly formed thrust combined with strong vertical strain, and nucleation of a new thrust. Continuous deformation produces an antiformal stack through progressive convergence of branch lines.

Nd isotopes represent one of the best tools to investigate the processes involved in the evolution of the continental crust and mantle. This is due mainly to the similar geochemical behaviour of Sm and Nd, both light rare earth elements, which inhibits their fractionation during most varied geological processes. In order to carry out crustal evolution studies in central Brazil, the Sm-Nd isotopic method was implanted at the Geochronology Laboratory of the University of Brasília. The Sm-Nd separation methodology is basically that described in Richard et al. (1976), with the addition of some improvements. In this study we describe in detail the methodology used in Brasília. Precision and accuracy were checked with the international standards such as JB-3, BCR-1, BHVO-1 and La Jolla, and the following results were found: JB-3 (Nd=15.74 ppm and Sm=4.28 ppm), BCR-1 (143Nd/144Nd=0.512647±8, Nd=28.73 ppm and Sm=6.66 ppm), BHVO-1 (Nd=24.83 ppm and Sm=6.2 ppm) and La Jolla (143Nd/144Nd=0.511835±14).

This paper discusses the facies distribution of Mesozoic eolian sandstones between the Sanga do Cabral and Botucatu formations and also their contact relationships, in São Leopoldo area, State of Rio Grande do Sul (RS), southern Brazil. The main distinctive characteristics regarding these sandstones and formations are the mineralogical composition, paleocurrents and the occurrence of wet interdune deposits. These interdune deposits are characterized by frequent thin mudstone layers with mudcracks, ichnofossils and salt impressions. There are also some features that resemble plant fossils. The distinctive characteristics of these sequences to Sanga do Cabral and Botucatu formations allow us to suggest the informal name of Pedreira Sandstone, considering its type section, the Pedreira Cliff, at Sapucaia do Sul, RS.