992 resultados para twisted canonical homomorphism


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Ascorbate (vitamin C) is an essential antioxidant and enzyme cofactor in both plants and animals. Ascorbate concentration is tightly regulated in plants, partly to respond to stress. Here, we demonstrate that ascorbate concentrations are determined via the posttranscriptional repression of GDP-l-galactose phosphorylase (GGP), a major control enzyme in the ascorbate biosynthesis pathway. This regulation requires a cis-acting upstream open reading frame (uORF) that represses the translation of the downstream GGP open reading frame under high ascorbate concentration. Disruption of this uORF stops the ascorbate feedback regulation of translation and results in increased ascorbate concentrations in leaves. The uORF is predicted to initiate at a noncanonical codon (ACG rather than AUG) and encode a 60- to 65-residue peptide. Analysis of ribosome protection data from Arabidopsis thaliana showed colocation of high levels of ribosomes with both the uORF and the main coding sequence of GGP. Together, our data indicate that the noncanonical uORF is translated and encodes a peptide that functions in the ascorbate inhibition of translation. This posttranslational regulation of ascorbate is likely an ancient mechanism of control as the uORF is conserved in GGP genes from mosses to angiosperms.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Canonical single-stranded DNA-binding proteins (SSBs) from the oligosaccharide/oligonucleotide-binding (OB) domain family are present in all known organisms and are critical for DNA replication, recombination and repair. The SSB from the hyperthermophilic crenarchaeote Sulfolobus solfataricus (SsoSSB) has a ‘simple’ domain organization consisting of a single DNA-binding OB fold coupled to a flexible C-terminal tail, in contrast with other SSBs in this family that incorporate up to four OB domains. Despite the large differences in the domain organization within the SSB family, the structure of the OB domain is remarkably similar all cellular life forms. However, there are significant differences in the molecular mechanism of ssDNA binding. We have determined the structure of the SsoSSB OB domain bound to ssDNA by NMR spectroscopy. We reveal that ssDNA recognition is modulated by base-stacking of three key aromatic residues, in contrast with the OB domains of human RPA and the recently discovered human homologue of SsoSSB, hSSB1. We also demonstrate that SsoSSB binds ssDNA with a footprint of five bases and with a defined binding polarity. These data elucidate the structural basis of DNA binding and shed light on the molecular mechanism by which these ‘simple’ SSBs interact with ssDNA.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Copyright estates have been unduly empowered by the extension of the term of copyright protection in Europe, the United States, Australia and elsewhere. The Estate of the Irish novelist, James Joyce, has been particularly aggressive in policing his revived copyrights. The "keepers of the flame" have relied upon threats of legal action to discourage the production of derivative works based upon the canonical texts of the novelist. The Estate has also jealously guarded the reputation of the author by vetoing the use of his work in various scholarly productions. Most radically of all, the grandson Stephen Joyce threatened to take legal action to prevent the staging of "Rejoyce Dublin 2004", a festival celebrating the centenary of Bloomsday. In response, the Irish Parliament rushed through emergency legislation, entitled the Copyright and Related Rights (Amendment) Act 2004 (Ireland) to safeguard the celebrations. The legislation clarified that a person could place literary and artistic works on public exhibition, without breaching the copyright vested in such cultural texts. Arguably, though, the ad hoc legislation passed by the Irish Parliament is inadequate. The Estate of James Joyce remains free to exercise its suite of economic and moral rights to control the use and adaptation of works of the Irish novelist. It is contended that copyright law needs to be revised to promote the interests of libraries and other cultural institutions. Most notably, the defence of fair dealing should be expanded to allow for the transformative use of copyright works, particularly in respect of adaptations and derived works. There should be greater scope for compulsory licensing and crown acquisition of revived copyrights.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This project investigated the interactions between insulin and its receptor. A combination of computational and experimental investigations resulted in the identification of four residues in non-canonical sites that, when mutated, had detrimental effects on insulin binding. An increased understanding of the binding mechanism will aid future research into diseases involving the insulin receptor and its relatives and could potentially lead to new therapeutic avenues to combat these health related issues.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The shoot represents the basic body plan in land plants. It consists of a repeated structure composed of stems and leaves. Whereas vascular plants generate a shoot in their diploid phase, non-vascular plants such as mosses form a shoot (called the gametophore) in their haploid generation. The evolution of regulatory mechanisms or genetic networks used in the development of these two kinds of shoots is unclear. TERMINAL EAR1-like genes have been involved in diploid shoot development in vascular plants. Here, we show that disruption of PpTEL1 from the moss Physcomitrella patens, causes reduced protonema growth and gametophore initiation, as well as defects in gametophore development. Leafy shoots formed on ΔTEL1 mutants exhibit shorter stems with more leaves per shoot, suggesting an accelerated leaf initiation (shortened plastochron), a phenotype shared with the Poaceae vascular plants TE1 and PLA2/LHD2 mutants. Moreover, the positive correlation between plastochron length and leaf size observed in ΔTEL1 mutants suggests a conserved compensatory mechanism correlating leaf growth and leaf initiation rate that would minimize overall changes in plant biomass. The RNA-binding protein encoded by PpTEL1 contains two N-terminus RNA-recognition motifs, and a third C-terminus non-canonical RRM, specific to TEL proteins. Removal of the PpTEL1 C-terminus (including this third RRM) or only 16–18 amino acids within it seriously impairs PpTEL1 function, suggesting a critical role for this third RRM. These results show a conserved function of the RNA-binding PpTEL1 protein in the regulation of shoot development, from early ancestors to vascular plants, that depends on the third TEL-specific RRM.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The title compound, C15H11NO, consists of a planar isoquinolinone group to which a phenyl ring is attached in a twisted fashion [dihedral angle = 39.44 (4)degrees]. The crystal packing is dominated by intermolecular N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds which define centrosymmetric dimeric entitities.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Let E be an elliptic curve defined over Q and let K/Q be a finite Galois extension with Galois group G. The equivariant Birch-Swinnerton-Dyer conjecture for h(1)(E x(Q) K)(1) viewed as amotive over Q with coefficients in Q[G] relates the twisted L-values associated with E with the arithmetic invariants of the same. In this paper I prescribe an approach to verify this conjecture for a given data. Using this approach, we verify the conjecture for an elliptic curve of conductor 11 and an S-3-extension of Q.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The growth of the Australian eastern king prawn (Melicertus plebejus) is understood in greater detail by quantifying the latitudinal effect. The latitudinal effect is the change in the species' growth rate during migration. Mark-recapture data (N = 1635, latitude 22.21 degrees S-34.00 degrees S) presents northerly movement of the eastern king prawn, with New South Wales prawns showing substantial average movement of 140 km (standard deviation: 176 km) north. A generalized von Bertalanffy growth model framework is used to incorporate the latitudinal effect together with the canonical seasonal effect. Applying this method to eastern king prawn mark-recapture data guarantees consistent estimates for the latitudinal and seasonal effects. For M. plebejus, it was found that growth rate peaks on 25 and 29 January for males and females, respectively; is at a minimum on 27 and 31 July, respectively; and that the shape parameter, k (per year), changes by -0.0236 and -0.0556 every 1 degree of latitude south increase for males and females, respectively.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Information structure and Kabyle constructions Three sentence types in the Construction Grammar framework The study examines three Kabyle sentence types and their variants. These sentence types have been chosen because they code the same state of affairs but have different syntactic structures. The sentence types are Dislocated sentence, Cleft sentence, and Canonical sentence. I argue first that a proper description of these sentence types should include information structure and, second, that a description which takes into account information structure is possible in the Construction Grammar framework. The study thus constitutes a testing ground for Construction Grammar for its applicability to a less known language. It constitutes a testing ground notably because the differentiation between the three types of sentences cannot be done without information structure categories and, consequently, these categories must be integrated also in the grammatical description. The information structure analysis is based on the model outlined by Knud Lambrecht. In that model, information structure is considered as a component of sentence grammar that assures the pragmatically correct sentence forms. The work starts by an examination of the three sentence types and the analyses that have been done in André Martinet s functional grammar framework. This introduces the sentence types chosen as the object of study and discusses the difficulties related to their analysis. After a presentation of the state of the art, including earlier and more recent models, the principles and notions of Construction Grammar and of Lambrecht s model are introduced and explicated. The information structure analysis is presented in three chapters, each treating one of the three sentence types. The analyses are based on spoken language data and elicitation. Prosody is included in the study when a syntactic structure seems to code two different focus structures. In such cases, it is pertinent to investigate whether these are coded by prosody. The final chapter presents the constructions that have been established and the problems encountered in analysing them. It also discusses the impact of the study on the theories used and on the theory of syntax in general.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In this study I offer a diachronic solution for a number of difficult inflectional endings in Old Church Slavic nominal declensions. In this context I address the perhaps most disputed and the most important question of the Slavic nominal inflectional morphology: whether there was in Proto-Slavic an Auslautgesetz (ALG), a law of final syllables, that narrowed the Proto-Indo-European vowel */o/ to */u/ in closed word-final syllables. In addition, the work contains an exhaustive morphological classification of the nouns and adjectives that occur in canonical Old Church Slavic. I argue that Proto-Indo-European */o/ became Proto-Slavic */u/ before word-final */s/ and */N/. This conclusion is based on the impossibility of finding credible analogical (as opposed to phonological) explanations for the forms supporting the ALG hypothesis, and on the survival of the neuter gender in Slavic. It is not likely that the */o/-stem nominative singular ending */-u/ was borrowed from the accusative singular, because the latter would have been the only paradigmatic form with the stem vowel */-u-/. It is equally unlikely that the ending */-u/ was borrowed from the */u/-stems, because the latter constituted a moribund class. The usually stated motivation for such an analogical borrowing, i.e. a need to prevent the merger of */o/-stem masculines with neuters of the same class, is not tenable. Extra-Slavic, as well as intra-Slavic evidence suggests that phonologically-triggered mergers between two semantically opaque genders do not tend to be prevented, but rather that such mergers lead to the loss of the gender opposition in question. On the other hand, if */-os/ had not become */-us/, most nouns and, most importantly, all adjectives and pronouns would have lost the formal distinction between masculines and neuters. This would have necessarily resulted in the loss of the neuter gender. A new explanation is given for the most apparent piece of evidence against the ALG hypothesis, the nominative-accusative singular of the */es/-stem neuters, e.g. nebo 'sky'. I argue that it arose in late Proto-Slavic dialects, replacing regular nebe, under the influence of the */o/- and */yo/-stems where a correlation had emerged between a hard root-final consonant and the termination -o, on the one hand, and a soft root-final consonant and the termination -e, on the other.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Molecular dynamics (MD) simulations are reported for an anchored bilayer formed by the intercalation of cetyl trimethyl ammonium (CTA) and CH3(CH2)15N+(CH3) ions in a layered solid, CdPS3. The intercalated CTA ions are organized with the cationic headgroups tethered to the inorganic sheet and the hydrocarbon tails arranged as bilayers. Simulations were performed at three temperatures, 65, 180, and 298 K, using an isothermal−isobaric ensemble that was subsequently switched once macroscopic parameters had converged to a canonical isothermal−isochoric ensemble. The simulations are able to reproduce the experimental features of this system, including the formation of the bilayer and layer-to-layer separation distance. An analysis of the conformation of the chains showed that at all three temperatures a fraction of the alkyl chains retained a planar all-trans conformation, and that gauche bonds occurred as part of a “kink” (gauche+−trans−gauche−) sequence and not as isolated gauche bonds. Trans−gauche isomerization rates for the alkyl chains in the anchored bilayer are slower than those in lipid bilayers at the same temperature and show a progressive increase as the torsion numbers approach the tail. A two-dimensional periodic Voronoi tessellation analysis was performed to obtain the single-molecular area of an alkyl chain in the bilayer. The single-molecular area relaxation times are an order of magnitude longer than the trans−gauche isomerization times. The results indicate that the trans−gauche isomerization is associated with the creation and annihilation of a kink defect sequence. The results of the present MD simulation explain the apparent conflicting estimates of the gauche disorder in this system as obtained from infrared and 13C nuclear magnetic resonance measurements.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The dissertation "From Conceptual to Corporeal, from Quotation to Site: Painting and History of Contemporary Art" explores the state of painting in contemporary art and art theory since the 1960s. The purpose of the study is to re-consider the dominant "end of painting" -narrative in contemporary art history, which goes back to the modernist ideology of painting as a reductive, medium-specific form of art. Drawing on Michel Foucault´s concepts of discursive formation and archive, as well as Jean-Luc Nancy´s post-phenomenological philosophy on corporeality, I suggest that contemporary painting can be redefined as a discursive-sensuous practice. Instead of seeing painting as obsolete or over as an avantgarde art genre, I show that there have been alternative, neo-avantgardist ways of defining painting since the end of the 1960s, such as French artist Daniel Buren´s early writings on painting as "theoretical practice". Consequently, the tendency of the canonical Anglo-American contemporary art narratives to underestimate the historical and institutional codes of art can be questioned. This tendency can be seen, for example, in Rosalind Krauss´s influential theory on index. The study also reflects the relations between conceptual art and painting since the 1960s and maps recent theories of painting, which re-examine the genre´s possibilities after the modernist rhetoric. Concepts of "flatbed", "painting in the extended field", "as painting" and so on are compared critically with the idea of painting as discursive practice. It is also shown that the issues in painting arise from the contemporary critical art debate while the dematerialisation paradigm of conceptual art has dissolved. The study focuses on the corporeal-material-sensuous -cluster of meanings attached to painting and searches for its avantgardist possibilities as redefined by postfeminist and post-phenomenological discourse. The ideas of hierarchy of the senses and synesthesia are developed within the framework of Jean-Luc Nancy´s and Luce Irigaray´s thought. The parameters for the study have been Finnish painting from 1990 to 2002. On the Finnish art scene there has been no "end of painting" ideology, strictly speaking. The mythology and medium-specificity of modernism have been deconstructed since the mid-1980s, but "the archive" of painting, like themes of abstraction, formalism and synesthesia have been re-worked by the discursive practice of painting, for example, in the works of Nina Roos, Tarja Pitkänen-Walter and Jussi Niva.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The study explores the first appearances of Russian ballet dancers on the stages of northern Europe in 1908 1910, particularly the performances organized by a Finnish impresario, Edvard Fazer, in Helsinki, Stockholm, Copenhagen and Berlin. The company, which consisted of dancers from the Imperial Theatres of St. Petersburg, travelled under the name The Imperial Russian Ballet of St. Petersburg. The Imperial Russian Ballet gave more than seventy performances altogether during its tours of Finland, Sweden, Denmark and central Europe. The synchronic approach of the study covers the various cities as well as genres and thus stretches the rather rigid geographical and genre boundaries of dance historiography. The study also explores the role of the canon in dance history, revealing some of the diversity which underlies the standard canonical interpretation of early twentieth-century Russian ballet by bringing in source material from the archives of northern Europe. Issues like the central position of written documentation, the importance of geographical centres, the emphasis on novelty and reformers and the short and narrow scholarly tradition have affected the formation of the dance history canon in the west, often imposing limits on the historians and narrowing the scope of research. The analysis of the tours concentrates on four themes: virtuosity, character dancing, the idea of the expressive body, and the controversy over ballet and new dance. The debate concerning the old and new within ballet is also touched upon. These issues are discussed in connection with each city, but are stressed differently depending on the local art scene. In Copenhagen, the strong local canon based on August Bournonville s works influenced the Danish criticism of Russian ballet. In Helsinki, Stockholm and Berlin, the lack of a solid local canon made critics and audiences more open to new influences, and ballet was discussed in a much broader cultural context than that provided by the local ballet tradition. The contemporary interest in the more natural, expressive human body, emerging both in theatre and dance, was an international trend that also influenced the way ballet was discussed. Character dancing, now at low ebb, played a central role in the success of the Imperial Russian Ballet, not only because of its exoticism but also because it was considered to echo the kind of performing body represented by new dance forms. By exploring this genre and its dancers, the thesis brings to light artists who are less known in the current dance history canon, but who made considerable careers in their own time.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Anselm of Canterbury (1033–1109) was a prolific letter writer. The modern edition of his letter collection comprises more than 600 folio-size pages in print and includes 472 letters, the vast majority of which were sent by him. Our knowledge of Anselm’s letters is derived from collections of his letters, for none of his correspondence survives in its original form of individual letters. There was no one canonical version of the collection, and the extant manuscripts generally differ substantially: the largest medieval manuscript witnesses include over 400 letters, while the smallest contain only a few. We know 38 manuscript witnesses, but no authorial manuscript survives. Certain references in Anselm’s letters reveal, however, that he collected his correspondence on at least two occasions while he was still abbot of Bec, and this study proposes that a third collection was possibly made under his supervision in Christ Church. The third collection also covered Anselm’s Canterbury period. Whether the third collection was authorial or posthumous is unclear. Certain contextual evidence and references in letters would suggest that the collection was authorial. If so, the collection was probably a register book, which was started in c. 1101 at the earliest. There is no positive proof that any of the three surviving minor collections may be authorial. Each of these collections was circulating at a very early stage, however, some probably in Anselm’s lifetime. Moreover, the minor collections seem to have been put together from smaller source units, which possibly originated at Bec. The contents of these units suggest very early and possibly authorial origins: the letters are mainly from Anselm’s years as prior of Bec. The critical edition by F. S. Schmitt represents the current phase in the textual tradition of Anselm’s letter collection. This study demonstrates that the value of the edition is weakened in particular by the way in which Schmitt selected manuscripts for collation, doubtless influenced by the fact that he had not established the structure of the tradition properly. Ultimately it is impossible to undertake systematic research on the letter collection on the basis of Schmitt’s edition.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In the title compound, C17H15Cl2NO, the dimethylaminophenyl group is close to coplanar with the central propenone group [dihedral angle =13.1 (1)degrees between the mean planes], while the dichlorophenyl group is twisted from the plane [dihedral angle = 64.0 (1)degrees].In the crystal, C-H center dot center dot center dot O and weak C-H center dot center dot center dot pi interactions are formed between molecules.