984 resultados para 5 ray gr.


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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Importin-alpha is the nuclear import receptor that recognizes cargo proteins with nuclear localization sequences (NLSs). Tile study of NLS peptidomimetics can provide a better understanding of the requirements for the molecular recognition of cargo proteins by importin-alpha, and potentially engender a large number of applications in medicine. Importin-a was crystallized with a set of six NLS peptidomimetics, and X-ray diffraction data were collected in the range 2.1-2.5 angstrom resolution. Preliminary electron density calculations show that the ligands are present in the crystals. (c) 2005 Elsevier B.V All rights reserved.

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Crystals of a myotoxic phospholipase A(2) from Bothrops neuwiedi pauloensis have been obtained. They diffracted at 2.5 Angstrom resolution using a synchrotron radiation source and belong to space group P3(1)21. Preliminary analysis shows that there are two molecules in the asymmetric unit. (C) 1999 Elsevier B.V. B.V. All rights reserved.

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Lectins are proteins important in various biological processes such as infection, cell differentiation and metastasis. The Parkia pendula lectin has been crystallized using the hanging-drop vapour diffusion method. X-ray diffraction data were collected using a Rigaku RU300 rotating anode generator and R-AXIS IV diffractometer. The cell parameters for P. pendula lectin are a=93.7 Angstrom b=161.1 Angstrom, c=80.0 Angstrom and space group C222. The maximum resolution was of 2.98 Angstrom. These data showed a R-sym=12.8%.

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Large single crystals have been obtained of S-III-SPIII, a phospholipase A(2) from the venom of Bothrops jararacussu. The crystals belong to the orthorhombic system space group C222, and diffract X-rays to a resolution of 1.9 Angstrom. Preliminary analysis reveals the presence of one molecule in the crystallographic asymmetric unit. The crystal structure is currently being determined using molecular replacement techniques.

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BnSP-6 (myotoxin I) is a phospholipase A2 homologue isolated from Bothrops neuwiedi pauloensis venom. Crystals of BnSP-6 were obtained which diffracted X-rays to 2.5 Angstrom resolution using a synchrotron radiation source at room temperature and belong to space group P3(1)21. The unit cell dimensions are a=b=57.7, c=131.1 Angstrom. The structure was solved by molecular replacement using the coordinates of bothropstoxin I from B. jararacussu venom. There are two molecules in the asymmetric unit.

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Raman spectroscopy and Electron Paramagnetic Resonance (EPR) studies were performed on a series of V(2)O(5)/TiO(2) catalysts prepared by a modified sol-gel method in order to identify the vanadium species. Two species of surface vanadium were identified by Raman measurements, monomeric vanadyls and polymeric vanadates. Monomeric vanadyls are characterized by a narrow Raman band at 1030 cm(-1) and polymeric vanadates by two broad bands in the region from 900 to 960 cm(-1) and 770 to 850 cm(-1). The Raman spectra do not exhibit characteristic peaks of crystalline V(2)O(5). These results are in agreement with those of X-ray Diffractometry (XRD) and Fourier Transform Infrared (FT-IR) previously reported (C.B. Rodella et al., J. Sol-Gel Sci. Techn., submitted). At least three families of V(4+) ions were identified by EPR investigations. The analysis of the EPR spectra suggests that isolated V(4+) ions are located in sites with octahedral symmetry substituting for Ti(4+) ions in the rutile structure. Magnetically interacting V(4+) ions are also present as pairs or clusters giving rise to a broad and structureless EPR line. At higher concentration of V(2)O(5), a partial oxidation of V(4+) to V(5+) is apparent from the EPR results.

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The enzymes of the shikimate pathway are potential targets for the development of new therapies because they are essential for bacteria but absent from mammals. The last step in this pathway is performed by chorismate synthase (CS), which catalyzes the conversion of 5-enolpyruvylshikimate-3-phosphate to chorismate. Optimization of crystallization trials allowed the crystallization of homogeneous recombinant CS from Mycobacterium tuberculosis (MtCS). The crystals of MtCS belong to space group P6(4)22 (or P6(2)22) and diffract to 2.8 Angstrom resolution, with unit-cell parameters a = b = 129.7, c = 156.8 Angstrom. There are two molecules in the asymmetric unit. Molecular-replacement trials were not sucessful. Heavy-atom derivative screening is in progress.

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The 5-enolpyruvylshikimate-3-phosphate synthase catalyses the sixth step of the shikimate pathway that is responsible for synthesizing aromatic compounds and is absent in mammals, which makes it a potential target for drugs development against microbial diseases. Here, we report the phosphate binding effects at the structure of the 5-enolpyruvyl shikimate-3-phosphate synthase from Mycobacterium tuberculosis. This enzyme is formed by two similar domains that close on each other induced by ligand binding, showing the occurrence of a large conformation change. We have monitored the phosphate binding effects using analytical ultracentrifugation, small angle X-ray scattering and, circular dichroism techniques. The low resolution results showed that the enzyme in the presence of phosphate clearly presented a more compact structure. Thermal-induced unfolding experiments followed by circular dichroism suggested that phosphate rigidified the enzyme. Summarizing, these data suggested that the phosphate itself is able to induce conformational change resulting in the closure movement in the M. tuberculosis 5-enolpyruvylshikimate-3-phosphate synthase. (c) 2006 Elsevier B.V. All rights reserved.

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

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Angiogenesis inhibitors have gained much public attention recently as anti-cancer agents and several are currently in clinical trials, including angiostatin (Phase I, Thomas Jefferson University Hospital, Philadelphia, PA). We report here the bowl-shaped structure of angiostatin kringles 1-3, the first multi-kringle structure to be determined. All three kringle lysine-binding sites contain a bound bicine molecule of crystallization while the former of kringle 2 and kringle 3 are cofacial. Moreover, the separation of the kringle 2 and kringle 3 lysiner binding sites is sufficient to accommodate the a-helix of the 30 residue pepticle VEK-30 found in the kringle 2/VEK-30 complex. Together the three kringles produce a central cavity suggestive of a unique domain where they may function in concert. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

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Bucain is a three-finger toxin, structurally homologous to snake-venom muscarinic toxins, from the venom of the Malayan krait Bungarus candidus. These proteins have molecular masses of approximately 6000-8000 da and encompass the potent curaremimetic neurotoxins which confer lethality to Elapidae and Hydrophidae venoms. Bucain was crystallized in two crystal forms by the hanging-drop vapour-diffusion technique in 0.1 M sodium citrate pH 5.6, 15% PEG 4000 and 0.15 M ammonium acetate. Form I crystals belong to the monoclinic system space group C2, with unit-cell parameters a = 93.73, b = 49.02, c = 74.09 Angstrom, beta = 111.32degrees, and diffract to a nominal resolution of 1.61 Angstrom. Form II crystals also belong to the space group C2, with unit-cell parameters a = 165.04, b = 49.44, c = 127.60 Angstrom, beta = 125.55degrees, and diffract to a nominal resolution of 2.78 Angstrom. The self-rotation function indicates the presence of four and eight molecules in the crystallographic asymmetric unit of the form I and form II crystals, respectively. Attempts to solve these structures by molecular-replacement methods have not been successful and a heavy-atom derivative search has been initiated.

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Lys49-phospholipase A(2) (Lys49-PLA(2)) homologues damage membranes by a Ca2+-independent mechanism which does not involve catalytic activity. The myotoxic Lys-49 phospholipase myotoxin II from Cerrophidion (Bothrops) godmani has been crystallized, and X-ray diffraction data were collected to 2.8 Angstrom resolution. Preliminary analysis reveals the presence of one molecule in the asymmetric unit.

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Crotoxin, a potent neurotoxin from the venom of the South American rattlesnake Crotalus durissus terrificus, exists as a heterodimer formed between a phospholipase A(2) and a catalytically inactive acidic phospholipase A(2) analogue (crotapotin). Large single crystals of the crotoxin complex and of the isolated subunits have been obtained. The crotoxin complex crystal belongs to the orthorhombic space group P2(1)2(1)2, with unit-cell parameters a = 38.2, b = 68.7, c = 84.2 angstrom, and diffracted to 1.75 angstrom resolution. The crystal of the phospholipase A(2) domain belongs to the hexagonal space group P6(1)22 (or its enantiomorph P6(5)22), with unit-cell parameters a = b = 38.7, c = 286.7 angstrom, and diffracted to 2.6 angstrom resolution. The crotapotin crystal diffracted to 2.3 angstrom resolution; however, the highly diffuse diffraction pattern did not permit unambiguous assignment of the unit-cell parameters.

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