194 research outputs found
Structural and dynamic properties of translocase motor SecA:
No full textSecA is a large, 204 kDa, homodimeric, helicase-like protein that is a key component of the bacteria protein secretion machinery. SecA, being a motor protein, couples the translocation of polypeptide segments across or into biological membranes with the expenditure of metabolic energy extracted from ATP hydrolysis. SecA adopts a compact conformation in the cytoplasm but switches to a relaxed one when is engaged to translocation at the membrane. Specific interaction of SecA with SecYEG induces large conformational changes to both partners that result in the stimulation of SecA’s ATPase activity and trigger the opening of the channel.
We use a combination of NMR spectroscopy, Isothermal Titration Calorimetry (ITC) and biochemical techniques to characterize E. coli SecA along the protein secretion pathway. Recent advances in isotope labeling and NMR methodology (methyl-TROSY) enabled the NMR study of SecA.
We found that the nucleotide binding cleft of SecA exists in a metastable state that undergoes a disorder-order transition upon nucleotide binding. Our data show that SecA uses a novel mechanism wherein conserved regions lining the cleft undergo cycles of disorder-order transitions while switching among functional catalytic states. The structural relation of SecA to helicases suggests that these proteins may utilize similar mechanisms to convert the ATP binding/hydrolysis energy to mechanical work.
Our data reveal that C domain undergoes cycles of detachment and rebinding to the motor that are linked with the ATPase activation of SecA. When the contacts with the C domain are loosened, SecA becomes activated and this process is probably facilitated by the membrane. Moreover, allosteric communication between the preprotein binding and the motor domain of SecA is regulated by nucleotide and signal peptide binding. Finally, we found that the extreme C terminus of SecY (C6 loop) contacts both the motor and the C domain of SecA and we identified important residues from the loop C6 that mediate this interaction.
In summary, our studies revealed the intimate relation between flexibility and catalytic efficiency in SecA as well the allosteric communication among the domains.Ph.D.Includes bibliographical references (p. 131-144)by Dimitra Keramisano
Geolinguistic spaces and the geopolitics of organization studies: movements across centers and peripheries: European group for organisational studies colloquium
No full textAcademic knowledge production and evaluation has been studied as a phenomenon situated across global and (semi)peripheral contexts (Lillis and Curry, 2010; Bennett, 2014). The metaphor of scales draws attention to the study of academic discourses as practices that develop across vertical, hierarchically organized layers (Blommaert, 2010). In this paper, we draw on 3 sub-corpora of organization studies journal articles, with each journal occupying a different position in the impact factor continuum. Building on the work of Lillis and Curry (2010), we study networked activities as social capital in the global academic economy. In our analysis we first examine the epistemological profile of organisation studies, as reflected in differentially ranked journals located in European contexts. We then explore the complex configuration of spaces/localities within and around which the production of knowledge takes place, by examining networks of author affiliations in relation to the identified sites in the empirical papers included in the corpus. Finally, we examine how constructions of the ‘local’ and the ‘global’ relate to the themes foregrounded in the aims and scope of each journal and we explore how discourses of the ‘local’ and the ‘global’ relate to key concepts in the field of organization studies, including institutions, alternatives and resistance, as well as power and gender
Assessing multiple sources of data to detect illegal fishing, trade and mislabelling of elasmobranchs in Greek markets
No full textElasmobranchs, extremely charismatic and threatened animals, still are an important economic source for fishers in many parts of the world, providing significant income through trade. Even though Greek seas host at least 67 elasmobranch species, our knowledge about their biology and ecology is to a large extent unknown. In the present study the integration of conventional (legislation, official data from fisheries landings and fish market value and import/export data) and unconventional (social media) sources of data, accompanied with the use of genetics, aim at outlining the elasmobranch fisheries and trade in Greece and identifying “weak spots” that sabotage their conservation. Results revealed that: (a) about 60% of the 68 specimens collected in fish markets were mislabelled, with that being very common for Prionace glauca and Mustelus spp., (b) Illegal fishing is a reality, c) Greece represents one of the top-three European Union southern countries in terms of elasmobranch market size, (d) Aegean Sea and especially its Northern part (Thermaikos Gulf and Thracian Sea) contributed to more than half of the M. mustelus Greek fisheries landings and (e) wholesale prices of elasmobranchs have remained stable during the last decade. Mislabelling and illegal trade of elasmobranchs are common ground in Greece. This context stems from incoherent and complex fisheries legislative framework due to institutional decoupling, discrepancies in the collection and analysis of fisheries-related data, thus substantially reducing the efficiency of the fisheries management in Greek seas
The right to childhoods : critical perspectives on rights, difference and knowledge in a transient world
No full textThis book offers an engaging study that analyses contemporary childhood by examining new lines of argument about diversity, disability and difference. The author critiques the key issues that affect both adults' and children's quality of life, including market-driven values, poverty and civic disengagement.In this fascinating study, Dimitra Hartas analyses contemporary childhood. She discusses the plurality inherent in childhood and the cultural, ideological, social and biological forces that shape children's experience of growing up in the 21st century. She engages with new lines of argument about diversity, disability and difference, and critiques the big issues that affect both adults' and children's quality of life such as market-driven values, poverty and civic disengagement.Hartas uncovers evidence of how the right to childhood is being violated in both the developed and developing world and how our consumerist culture is shaping children's lives in ways that are not always understood, and advocates the right to childhoods. She concludes by discussing the implications of her findings for both policy and practice in early childhood education, and examines pedagogies that are responsive to ethics, diversity and difference
SPECIAL ISSUE | Digital Role-Playing Games and Theatre: Retooling and Repurposing Entertainment, Art, Learning (Part 2)
No full textAuthors: Aikaterini Delikonstantinidou National and Kapodistrian University of Athens Dimitra Nikolaidou Aristotle University of Thessaloniki Download PDF version THEATRE AND/AS DIGITAL GAME As Lori M. Shyba has proposed, central among the benefits to be reaped by MMORPGs via the incorporation of theatre tools are enhanced gameplay experiences, games’ development as “a unique art form,” and their emergence as “an experiential way to rehearse social change” (2007, 779). The latter insof..
SPECIAL ISSUE | Digital Role-Playing Games and Theatre: Retooling and Repurposing Entertainment, Art, Learning (Part 1)
No full textAuthors: Aikaterini Delikonstantinidou National and Kapodistrian University of Athens Dimitra Nikolaidou Aristotle University of Thessaloniki Download PDF version INTRODUCTION What do Shakespeare’s The Tempest and modern gaming have in common? According to Gina Bloom’s Gaming the Stage (2018), the answer is a set of strategies of playing, such as withholding, divulging, speculating, and wagering on knowledge. These, on the one hand, allowed one to act upon their knowledge of gaming in ..
Split the cash from cache-friendly recommendations
No full textRecommender systems have been established as a key component of video streaming services, shaping up to 80% of content requests. Hence, recommendations are employed by the Content Providers (CPs) of these services to increase the viewing time and their revenues. Furthermore, it has been recently suggested that recommendations could be a means to reduce the operational costs of the Content Delivery Networks (CDNs) when they are related to already cached items, i.e., when they are cache-friendly. Clearly, these conflicting objectives, i.e., increasing revenue for the CP and reducing costs for the CDN, can create tensions between the two entities, and hence, prevent the full utilization of recommendations. In this work, we propose a model for capturing these tradeoffs, and an economic mechanism, based on the Nash bargaining solution, for reconciling the potentially conflicting objectives of the CP and the CDN. Our scheme enables the CP and CDN to jointly design the recommendations in a way that balances the revenue gains and cost savings, ensuring a fair and Pareto optimal split of the accrued benefits for both entities. Our numerical experiments in realistic scenarios show that the proposed scheme leads to important financial gains of up to 30%.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Embedded System
High Responsivity and Response Speed Single‐Layer Mixed‐Cation Lead Mixed‐Halide Perovskite Photodetectors Based on Nanogap Electrodes Manufactured on Large‐Area Rigid and Flexible Substrates
No full textAdv. Funct. Mater. 2019, 29, 1901371 In the initially published version of this article, the name of Akmaral Seitkhan was omitted from the final authors list. The correct author list is as follows: Dimitra G. Georgiadou,* Yen-Hung Lin, Jongchul Lim, Sinclair Ratnasingham, Akmaral Seitkhan, Martyn A. McLachlan, Henry J. Snaith, and Thomas D. Anthopoulos* The respective updated author affiliations are as follows: Dr. D. G. Georgiadou, Prof. T. D. Anthopoulos Department of Physics and Centre for Plastic Electronics Blackett Laboratory Imperial College London Exhibition Road, London SW7 2BW, UK E-mail: [email protected]; [email protected] Dr. D. G. Georgiadou, S. Ratnasingham, Dr. M. A. McLachlan Department of Materials and Centre for Plastic Electronics Imperial College London Prince Consort Road, London SW7 2BP, UK Dr. Y.-H. Lin, Dr. J. Lim, Prof. H. J. Snaith Department of Physics University of Oxford Clarendon Laboratory Parks Road, Oxford OX1 3PU, UK A. Seitkhan, Prof. T. D. Anthopoulos Division of Physical Sciences and Engineering King Abdullah University of Science and Technology (KAUST) Thuwal 23955–6900, Saudi Arabia The authors apologize for any inconvenience this error may have caused.</p
Author positioning and audience addressivity by means of 'we' in Greek academic discourse
No full textThe present chapter reports on a study of first person plural reference in a corpus of 15 Linguistics journal articles by Greek-speaking authors. This data-driven investigation aims to explore the ways in which linguists construct their positionand their relationship with the audience/academic community within the Greek context. Three main categories of semantic reference were identified: referential, generic and ambiguous. Ambiguous referential uses are examined closely,including examples that cut across the inclusive-exclusive divide. The results suggest that the rhetorical practices of Greek-speaking authors seem to relate to the size and type of the academic community they are addressing
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