365 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
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
Trait Impulsivity, cigarette smoking and e-cigarette use
No full textAlthough there is considerable evidence of an association between impulsivity and cigarette smoking, the magnitude of this association varies greatly across studies. On the other hand, research on the relationship between trait impulsivity and e-cigarette use is limited, and the available results also provide mixed findings. This thesis aimed to understand the relationship between trait impulsivity, cigarette smoking, and e-cigarette use. It also examines the role of e-cigarettes in smoking cessation as there is great controversy over the efficacy of e-cigarette use as a smoking cessation tool. A systematic review of the literature identified that cigarette smokers are more impulsive than non smokers, while emotion-based impulsivity is the impulsivity-related trait most associated with nicotine dependence. A study of 720 mainly European adults found different relationships between specific impulsivity-related traits and different classes of smoking status, suggesting that lack of perseverance differentiated e-cigarette users from cigarette smokers, and emotion-based impulsivity differentiated e-cigarette users from dual users (those who smoke a cigarette and use an e-cigarette). Additionally, it was found that trait impulsivity is related to e-cigarette use through positive e-cigarette attitudes. An Ecological Momentary Assessment study further showed that emotion-based impulsivity is a significant predictor of real-time cravings and real-time moods in cigarette smokers, e-cigarette users and dual users. The final study of the thesis assessed the role of e-cigarettes and trait impulsivity in smoking cessation. Findings suggest that e-cigarette use could potential be a useful tool in helping cigarette smokers to quit smoking. These findings help to further understand the role of trait impulsivity in cigarette smoking and e-cigarette use, and the relationship between cigarette smoking and e-cigarette use
Understanding health behaviours in context : A systematic review and meta-analysis of Ecological Momentary Assessment studies of five key health behaviours
No full textAcknowledgments The review team would like to thank Dr. David Simons for his help with the R code, as well as Dr. Pierre Gerain, Sally Di Maio, Rike Panse, Noemi Lorbeer, Malte Stollwerck, Dr. Paul Gellert, and Dr. Ann DeSmet for their contributions to the data extraction. Funding Olga Perski and Dimitra Kale receive salary support from Cancer Research UK (C1417/A22962). Daniel Powell is funded by the Scottish Government’s Rural and Environment Science and Analytical Services (RESAS) and by the School of Medicine, Medical Sciences, and Nutrition (SMMSN) at the University of Aberdeen. Felix Naughton’s salary is covered by the Faculty of Medicine and Health Sciences at the University of East Anglia. Dominika Kwasnicka’s work is carried out within the HOMING program of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund (grant number POIR.04.04.00-00-5CF3/18-00; HOMING 5/2018) and she is also funded by the NHMRC CRE in Digital Technology to Transform Chronic Disease Outcomes, Australia.Peer reviewe
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 ..
Commentary on Lim et al.: Real-world e-cigarette use under prescription-only regulation
No full text"Prescription-only access to e-cigarettes has been proposed as a regulatory compromise that could restrict youth uptake while enabling access for smoking cessation. Evidence from Australia’s experience suggests that this model neither prevented experimentation among never-smokers nor facilitated the widespread use of regulated products for cessation, instead shifting use toward unregulated supply channels.
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
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