1,721,057 research outputs found
The role and mechanisms of REMORIN assembly
No full textLes remorines (REMs) sont des protéines multifonctionnelles qui jouent des rôles essentiels dans l'immunité des plantes, le développement et la symbiose en s'associant à la membrane plasmique et en séquestrant des lipides spécifiques dans des nanodomaines membranaires fonctionnels. Ces protéines sont classées dans une famille multigénique avec six groupes caractérisés par des compositions distinctes de domaines de protéines. Tous les membres de la famille des REMs partagent une ancre membranaire C-terminale (REM-CA), un domaine d'homo-oligomérisation, et une région N-terminale intrinsèquement désordonnée (IDR) de longueur variable. De manière unique, les REMs contournent la voie sécrétoire pour cibler la membrane et se localisent dans distincts nanodomaines en fonction de leur groupe phylogénétique. Dans cette étude, nous avons combiné la spectroscopie de Résonance Magnétique Nucléaire (RMN), les calculs de structure de protéines et des simulations avancées de dynamique moléculaire (MD) pour révéler les propriétés de structuration et de dynamiques des REMs. Nous avons découvert que les REMs forment des dimères stables pré-structurés en coiled-coil dans le cytosol, qui agissent comme des unités modulables pour cibler des nanodomaines. Ces dimères présentent, avant l'association avec la membrane, une charge positive de la surface en forme de code-barres, dépendante des REMs. En outre, les REM-CA montrent des variations en structures et dynamiques au sein de la famille, fournissant une plateforme sélective pour l’association avec les phospholipides lors du contact avec la membrane. L'IDR N-terminale forme un ensemble structural flexible en forme de « fuzzy coat » autour du coeur coiled-coil. Les ancres C-terminales créent une avidité à travers des interactions électrostatiques multivalentes entre les groupes des lipides anioniques et la surface chargée positivement du dimère, indiquant un mécanisme synergique entre REM-CA et le domaine coiled-coil pour ségréguer les nanodomaines lipides-protéines. La RMN du solide et les simulations MD à gros grain de REMs sur la membrane lipidique ont également révélé le comportement distinct des REM-CA lorsqu'ils sont associés aux lipides de la membrane. Nous observons des différences dans les profils d'association des REM-CA et des coiled-coils chargés à la membrane, en fonction des charges de surface du dimère et des lipides présents dans la membrane. La stabilité du coiled-coil et l'intensité de l'association à la membrane sont modulées par les groupement des tête chargées des lipides présents à la surface de la membrane. Ces découvertes améliorent notre compréhension des mécanismes moléculaires sous-jacents au rôle des REMs dans l'organisation de la membrane des plantes, des localisations séléctives des REMs dans les nanodomaines des membranes et des facteurs structurales contribuant aux différentes fonctions des remorines. Cette recherche propose une base pour de futures études visant à élucider les comportements complexes des REMs associés aux membranes et les ajustement des structures lors des mécanismes de signalisation et de défense cellulaires.Remorins are multifunctional proteins that play vital roles in plant immunity, development, and symbiosis by associating with the plasma membrane and sequestering specific lipids into functional membrane nanodomains. These proteins are classified into a multigenic family with six groups characterized by distinct protein-domain compositions. All remorin family members share a C-terminal membrane anchor (REM-CA), a homo-oligomerization domain, and the N-terminal is an intrinsically disordered region (IDR) of variable length. Uniquely, REMs bypass the secretory pathway for membrane targeting and localize to different nanodomains based on their phylogenetic group. In this study, we combined Nuclear Magnetic Resonance (NMR) spectroscopy, protein structure calculations, and advanced molecular dynamics (MD) simulations to reveal the structural and dynamic properties of REMs. We discovered that remorins form stable pre-structured coiled-coil dimers in the cytosol, which act as tunable nanodomain-targeting units. These dimers feature a REM-dependent barcode-like positive surface charge before membrane association. Furthermore, the REM-CAs exhibit structural and dynamic variations across the family, providing a selective platform for phospholipid binding upon membrane contact. The N-terminal IDR forms a flexible fuzzy structural ensemble around the coiled-coil core. The C-terminal anchors create avidity through multivalent electrostatic interactions between anionic lipid headgroups and the positively charged dimer surface, supporting a synergistic mechanism between REM-CA and the coiled-coil domain to segregate lipid-protein nanodomains. Solid-state NMR and coarse-grained MD simulations further revealed the distinct behavior of REM-CAs when associated to the lipid membrane. We observe differences in membrane association profiles of the REM-CAs and of the charged coiled-coils dependent on the dimer surface charges and dependent on the lipids present in the membrane. Coiled-coil stability and the intensity of membrane association is tuned by the lipid headgroups on the membrane surface. The insights enhance our understanding of the molecular mechanisms underlying the role of remorins in membrane organization in plants, the distinct localizations of remorins in membrane nanodomains and the structural factors contributing to the different remorin functions. This research lays the groundwork for future studies to elucidate the complex behaviors of membrane-associated REMs and their structural tuning during cellular signaling and defense mechanisms
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Études structurales des protéines fibrillaires par spectroscopie de RMN à l’état solide
No full textLa RMN à l’état solide est une méthode de choix pour l’étude des protéines insolubles et des complexes protéiques de haut poids moléculaire. L’insolubilité intrinsèque des protéines fibrillaires, ainsi que leur architecture complexe, rendent difficile leur caractérisation structurale par la cristallographie et par la RMN en solution. La RMN à l‘état solide n’est pas limitée par le poids moléculaire et constitue donc un outil puissant pour l’étude des protéines fibrillaires. L’attribution des résonances RMN est le prérequis pour obtenir des informations structurales à résolution atomique. La première partie de ce travail de thèse décrit le développement de méthodes en RMN à l’état solide pour l’attribution des résonances. Nous avons appliqué ces méthodes afin d’attribuer le domaine C-terminal du prion Ure2 (33 kDa), qui est à ce jour la plus grande protéine attribuée par RMN à l’état solide. Nos résultats fournissent les bases pour l’étude de protéines à haut poids moléculaire à l’échelle atomique. Ceci est démontré dans la seconde partie de ce travail de thèse avec les premières études RMN à l’état solide des fibrilles des prions Ure2 et Sup35. Nous avons caractérisé la structure de ces prions pour les fibrilles entières ainsi que pour les domaines isolés. La troisième fibrille étudiée est l’α- synuclein, fibrille associée à la maladie de Parkinson, pour laquelle nous présentons l’attribution des résonances RMN ainsi que la structure secondaire d’un nouveau polymorphe. Les études présentées ici fournissent de nouvelles clés pour comprendre la diversité des architectures de fibrilles, en considérant les fibrilles comme entités individuelles d’un point de vue structuralSolid-state NMR is the method of choice for studies on insoluble proteins and other high molecular weight protein complexes. The inherent insolubility of fibrillar proteins, as well as their complex architecture, makes the application of x-ray crystallography and solution state NMR difficult. Solid-state NMR is not limited by the molecular weight or by the absence of long-range structural order, and is thus a powerful tool for the 3D structural investigation of fibrillar proteins. The assignment of the NMR resonances is a prerequisite to obtain structural information at atomic level. The first part of this thesis describes the development of solid-state NMR methods to assign the resonances in large proteins. We apply these methods to assign the 33 kDa C-terminal domain of the Ure2p prion which is up to now the largest protein assigned by solid-state NMR. Our results provide the basis to study high molecular weight proteins at atomic level. This is demonstrated in the second part with the first high-resolution solid-state NMR study of Ure2 and Sup35 prion fibrils. We describe the conformation of the functional domains and prion domains in the full-length fibrils and in isolation. The third fibrillar protein addressed in this work is the Parkinson’s disease related α-synuclein whereof we demonstrate the NMR resonance assignment and the secondary structure determination of a new polymorph. Thus, the studies described here provide new insights in the structural diversity of fibril architectures, and plead to view fibrils as individuals from a structural point of view, rather than a homogenous protein famil
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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