927 resultados para motif


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Mode of access: Internet.

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Chemokine (C-C motif) ligand-2 (CCL2) is a chemoattractant and activator of macrophages and is a key determinant of the macrophage infiltrate into tumours. We demonstrate here that CCL2 is expressed in normal human ovarian surface epithelium ( HOSE) cells and is silenced in most ovarian cancer cell lines, and silenced or downregulated in the majority of primary ovarian adenocarcinomas. Analysis of the CCL2 locus at 17q11.2-q12 showed loss of heterozygosity (LOH) in 70% of primary tumours, and this was significantly more common in tumours of advanced stage or grade. However, we did not detect any mutations in the CCL2 coding sequence in 94 primary ovarian adenocarcinomas. These data support the hypothesis that CCL2 may play a role in the pathobiology of ovarian cancers, but additional studies will be required to evaluate this possibility.

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The cyclotides are a large family of plant proteins that have a cyclic backbone and a knotted arrangement of three conserved disulfide bonds. Despite the apparent complexity of their cystine knot motif it is possible to efficiently fold these proteins, as exemplified by oxidative folding studies on the prototypic cyclotide, kalata B1. This mini-review reports on the current understanding of the folding process in cyclotides. The synthesis and folding of these molecules paves the way for their application as stable molecular templates.

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Cyclotides are a large family of mini-proteins that have the distinguishing features of a head-to-tail cyclised backbone and a cystine knot formed by six conserved cysteine residues. They are present in plants from the Rubiaceae, Violaceae and Cucurbitaceae families. The unique structural features of the cyclotides make them extremely resistant to chemical, thermal and proteolytic degradation. In this article we review recent Studies from our laboratory that dissect the role of the individual structural elements in defining the stability of cyclotides. The resistance of cyclotides to chemical and proteolytic degradation is in large part due to the cystine knot, whereas the thermal stability is I composite of several features including the cystine knot, the cyclic backbone and the hydrogen bonding network. A range of biological activities of cyclotides is critically dependent oil the presence of the cyclic backbone.

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The cyclotides are a family of circular proteins with a range of biological activities and potential pharmaceutical and agricultural applications. The biosynthetic mechanism of cyclization is unknown and the discovery of novel sequences may assist in achieving this goal. In the present study, we have isolated a new cyclotide from Oldenlandia affinis, kalata B8, which appears to be a hybrid of the two major subfamilies (Mobius and bracelet) of currently known cyclotides. We have determined the three-dimensional structure of kalata B8 and observed broadening of resonances directly involved in the cystine knot motif, suggesting flexibility in this region despite it being the core structural element of the cyclotides. The cystine knot motif is widespread throughout Nature and inherently stable, making this apparent flexibility a surprising result. Further-more, there appears to be isomerization of the peptide backbone at an Asp-Gly sequence in the region involved in the cyclization process. Interestingly, such isomerization has been previously characterized in related cyclic knottins from Momordica cochinchinensis that have no sequence similarity to kalata B8 apart from the six conserved cysteine residues and may result from a common mechanism of cyclization. Kalata B8 also provides insight into the structure-activity relationships of cyclotides as it displays anti-HIV activity but lacks haemolytic activity. The 'uncoupling' of these two activities has not previously been observed for the cyclotides and may be related to the unusual hydrophilic nature of the peptide.

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Natural myo-inositol phosphate antioxidants containing the 1,2,3-trisphosphate motif bind Fe3+ in the unstable penta-axial conformation.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

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The following paper examines Walter Benjamin’s reflection on the category of “redemption”, mainly developed in the theses On the concept of History. To this end, we will try firstly to reconstruct Benjamin’s critique of “fate”, as it unfolds in the twenties on the field of right, economy and, especially, history. The critique of the expiatory logic of “fate” – developed in essays such as Fate and Character, Critique of violence or Capitalism as religion – will then allow us to disclose the “dialectical” structure of redemption, whereby Benjamin mobilizes his previous theory of knowledge against the doctrine of progress.

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The search for patterns or motifs in data represents an area of key interest to many researchers. In this paper we present the Motif Tracking Algorithm, a novel immune inspired pattern identification tool that is able to identify variable length unknown motifs which repeat within time series data. The algorithm searches from a completely neutral perspective that is independent of the data being analysed and the underlying motifs. In this paper we test the flexibility of the motif tracking algorithm by applying it to the search for patterns in two industrial data sets. The algorithm is able to identify a population of motifs successfully in both cases, and the value of these motifs is discussed.

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Ce mémoire est constitué de trois volets. Tout d'abord, on y présente une création littéraire, court recueil de nouvelles intitulé Les regards traîtres. Celui-ci est suivi d'un essai portant sur le sous-genre fantastique, qui dans sa forme canonique offre une place prépondérante aux motifs littéraires. Suit une courte revue du motif du mauvais œil et une analyse détaillée d'un corpus de nouvelles de l'auteur québécois Bertrand Bergeron. Celles-ci ont été sélectionnées parmi les ouvrages de l'auteur afin de mettre en lumière la transformation et la refonte du motif littéraire du mauvais œil dans l'écriture néo-fantastique contemporaine. Enfin, le dernier volet consiste en un retour réflexif ayant pour but de démontrer les mécanismes à l’œuvre dans ma création afin d'illustrer les questions étudiés dans le mémoire. Il s'agit donc ici, tant dans l'étude des théories et dans celle du corpus de Bergeron que dans la création inédite, d'explorer non seulement les constituants du sous-genre fantastique et la présence du motif à l'étude, mais bien de cerner l'actualisation de ce motif dans l’œuvre de Bergeron, d'en démontrer la forme, renouvelée ou pas, et finalement de procéder à la mise en scène dans mes propres nouvelles de cette actualisation. Les résultats obtenus à la suite de ces exercices démontrent que le motif littéraire du mauvais œil, bien qu'utilisé de manière différente, subsiste dans une forme revisitée sous la plume d'un auteur de néo-fantastique tel que Bertrand Bergeron. Les nouvelles du recueil Les regards traîtres concrétisent, quant à elles, la possibilité de faire vivre ce motif, voire d'en faire le moteur de mes intrigues.

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The search for patterns or motifs in data represents a problem area of key interest to finance and economic researchers. In this paper we introduce the Motif Tracking Algorithm, a novel immune inspired pattern identification tool that is able to identify unknown motifs of a non specified length which repeat within time series data. The power of the algorithm comes from the fact that it uses a small number of parameters with minimal assumptions regarding the data being examined or the underlying motifs. Our interest lies in applying the algorithm to financial time series data to identify unknown patterns that exist. The algorithm is tested using three separate data sets. Particular suitability to financial data is shown by applying it to oil price data. In all cases the algorithm identifies the presence of a motif population in a fast and efficient manner due to the utilisation of an intuitive symbolic representation. The resulting population of motifs is shown to have considerable potential value for other applications such as forecasting and algorithm seeding.

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DnaD is a primosomal protein that remodels supercoiled plasmids. It binds to supercoiled forms and converts them to open forms without nicking. During this remodeling process, all the writhe is converted to twist and the plasmids are held around the periphery of large scaffolds made up of DnaD molecules. This DNA-remodeling function is the sum of a scaffold-forming activity on the N-terminal domain and a DNA-dependent oligomerization activity on the C-terminal domain. We have determined the crystal structure of the scaffold-forming N-terminal domain, which reveals a winged-helix architecture, with additional structural elements extending from both N- and C-termini. Four monomers form dimers that join into a tetramer. The N-terminal extension mediates dimerization and tetramerization, with extensive interactions and distinct interfaces. The wings and helices of the winged-helix domains remain exposed on the surface of the tetramer. Structure-guided mutagenesis and atomic force microscopy imaging indicate that these elements, together with the C-terminal extension, are involved in scaffold formation. Based upon our data, we propose a model for the DnaD-mediated scaffold formation.