392 research outputs found
Directed Evolution of a Novel N-Carbamylase/D-Hydantoinase Fusion Enzyme for Functional Expression with Enhanced Stability
No full textBifunctional enzymes find a wide application as a monitoring facility and a potential biocatalyst in molecular biology and biotechnology. Recombination of natural enzymes to a bifunctional fusion offers valuable tools, but the functional and structural instability of artificial
fusion enzymes remains to be solved. Based on
structural traits of microbial D- hydantoinase, we attempted to construct a bifunctional N-carbamylase/Dhydantoinase
fusion enzyme that would be useful for the
synthesis of nonnatural D-amino acids in a concerted fashion. The bifunctional ability of D-hydantoinase, as a fusion partner, was noticeable, but the resulting fusion
enzyme was subjected to serious proteolysis in vivo, as generally encountered in the expression of large the multidomain
polypeptide in E. coli. In an effort to improve the structural instability imposed by artificial linear fusion, directed evolution of the fusion enzyme was performed
using DNA shuffling with a consensus primer to maintain a crucial domain for the enzyme activity. The evolved fusion enzyme, F11, was selected after repeated rounds, and this enzyme was found to show sixfold increased
performance in the production of D-amino acid
compared with the parent fusion enzyme, which was mainly due to the enhanced structural stability of the evolved fusion enzyme. This result is an example showing
that directed evolution of the linearly fused polypeptide may broaden the opportunity to generate a fusion enzyme with greater potential
Crystal structure of D-hydantoinase from Bacillus stearothermophilus: Insight into the stereochemistry of enantioselectivity
No full textIndustrial production of antibiotics, such as semisynthetic penicillins and cephalosporins, requires optically pure D-p-hydroxylphenylglycine and its derivatives as important side-chain precursors. To produce optically pure D-amino acids, microbial D-hydantoinase (E.C. 3.5.2.2) is used for stereospecific hydrolysis of chemically synthesized cyclic hydantoins. We report the apo-crystal structure Of D-hydantoinase from B. stearothermophilus SDI at 3.0 Angstrom resolution. The structure has a classic TIM barrel fold. Despite an undetectable similarity in sequence, D-hydantoinase shares a striking structural similarity with the recently solved structure of dihydroorotase. A structural comparison of hydantoinase with dihydroorotase revealed that the catalytic chemistry is conserved, while the substrate recognition is not. This structure provides insight into the stereochemistry of enantioselectivity in hydrolysis and illustrates how the enzyme recognizes stereospecific exocyclic substituents and hydrolyzes hydantoins. It should also provide a rationale for further directed evolution of this enzyme for hydrolysis of new hydantoins with novel exocyclic substituents
A model for pseudo-Dirac neutrinos: leptogenesis and ultra-high energy neutrinos
No full textWe propose a model where sterile neutrinos are introduced to make light neutrinos to be pseudo-Dirac particles. It is shown how tiny mass splitting necessary for realizing pseudo-Dirac neutrinos can be achieved. Within the model, we show how leptogenesis can be successfully generated. Motivated by the recent observation of very high energy neutrino events at IceCube, we study a possibility to observe the effects of the pseudo-Dirac property of neutrinos by performing astronomical-scale baseline experiments to uncover the oscillation effects of very tiny mass splitting. We also discuss future prospect to observe the effects of the pseudo-Dirac property of neutrinos at high energy neutrino experiments. © 2016, The Author(s)3611Nsciescopu
Unravelling Interdependence: Coordinating Public-Private Service Networks
No full textGovernments aim to improve service delivery towards citizens and businesses. One of the main trends in this area is that organisations are increasingly trying to integrate service delivery by using information and communication technology (ICT). Service integration is necessary as individual service offerings are often just a part of a bigger process. This overall process does not stop at the boundaries of individual organisations, or at the boundary between the public and the private sector. Therefore, in order to improve service delivery, the service providers have to collaborate and integrate their services across organisational boundaries. The challenges that these collaborations face are varied, including heterogeneous organisations, a variety of processes, and fragmented information systems. How can we deal with these challenges to realise integrated service delivery? It is this question that is the background of this dissertation. It is addressed by exploring the interdependence in integrated service delivery, provided by networks of public and private organisations. Ultimately, the dissertation improves the understanding of the coordination of such public-private service networks.Infrastructure Systems & ServicesTechnology, Policy and Managemen
Fears about treatment among young drug abusers in Hong Kong
No full textAuthor name used in this publication: Yida Y.H. Chung2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishedVoR allowe
IT-induced public sector transformation
No full textIT-induced public sector transformation investigates the organizational changes that are undertaken to transform public administrations using information technology (IT). While IT made governments more efficient, it is unclear whether it will also make them more effective in creating public value for citizens and businesses. This study investigates the outcomes of IT-induced transformation and the factors that influence these outcomes. It finds that transformed organizations do not emerge on the short term; IT-induced transformation often remains a promise of IT projects rather than an outcome. Instead of realizing organizational change, governments focus on setting up governance. While many of the public sector IT-projects traditionally aim to improve service delivery to citizens and businesses, in practice, they more often create better enforcement and control for government organizations.ICTTechnology, Policy and Managemen
Author Correction: Rapid increase in the risk of heat-related mortality.
No full textCorrection to: Nature Communicationshttps://doi.org/10.1038/s41467-023-40599-x, published online 24 August 2023 The original version of this Article omitted from the author list the 17th author, “Multi-Country Multi-City (MCC) collaborative research network”, which is the consortium providing the mortality data. A list of consortium authors and their affiliations are provided in the HTML version of this Correction. Part of the Author Contributions statement was incorrectly given and should have read ‘A.M.V.C., E.M.F., B.A., M.D.S.Z.S.C., Y.L.G., Y.G., Y.H., V.H., J.K., E.L., D.R., N.R., N.S., S.S., A.U., A.G. and the MCC were involved in resources and data curation.’ In addition, the primary affiliation ‘Climate Research Foundation (FIC), Madrid, Spain’ for Dominic Roye was missing
Netcentric Information Orchestration: Assuring Information and System Quality in Public Safety Networks
No full textDuring daily operations, relief agencies such as police, fire brigade and medical services manage information in accordance with their respective processes and organization structure. When disaster strikes, the ad-hoc combinations of such hierarchy based information systems fail to assure high information quality (IQ) and system quality (SQ) for relief workers. Disaster such as 9/11, Katrina and the Polderbaan-crash have taught us that poor IQ and SQ significantly hamper disaster response efforts and can be lethal for relief workers and citizens. Drawing on empirical data (field studies) and pathways in ‘state of the art’ theories, this dissertation presents ten design principles for assuring IQ and SQ in public safety networks. These principles are the cornerstones of a design theory coined as ‘Netcentric Information Orchestration’ and are meant to guide information system architects, practitioners, software vendors and policy makers in the (re)design of information systems for disaster response. We evaluated the design principles on their technical feasibility (using prototyping) and on their ability to assure IQ and SQ for relief workers (using quasi-experimental gaming-simulation). Findings indicate that the proposed design principles assure higher levels for most IQ and SQ dimensions.Information and Communication TechnologyTechnology, Policy and Managemen
Service Composition: A Method for Developing Compositions in a Multi-actor Context
No full textInfrastructures, Systems and ServicesTechnology, Policy and Managemen
Serving the Poor: Designing a Mobile Service Platform for Smallholder Farmer Inclusion in Global Value Chains
No full textThe starting point for this research was the rapid proliferation of mobile devices, which had covered 95% of the world’s population by 2014. This research addresses the role of multi-sided mobile service platforms in improving the lives of smallholder farmers, who make up a large proportion of the world’s poor. The mobile phone has the potential to serve as a ‘two-sided market’ to intermediate between two or more groups of agents, smallholder farmers at the one hand and, providers of public and private services at the other hand, to offer each other network benefits, particularly in the application of traceability to connect smallholder farmers to global value chains. First, mobile service approaches for the rural poor in agriculture were reviewed, followed by semi-structured interviews with key informants to identify platform providers, stakeholders and business models. We then investigated the role of smallholders, use of mobile platforms to enable traceability from farms to consumers, and user context of smallholder farmers in Indonesia. Then we described the methodology for the design of requirements, structural specifications and a prototype mobile service platform. Through user and stakeholder interviews in Indonesia between 2011 and 2013, requirements for the platform were used to analyze both from a service provider and consumer aspect, where the service offers marginal benefits and serves strategic and operational interests. Through a field experiment, we investigated the technology acceptance model for smallholder farmers to deliver traceability data to global value chains, adding value to the market for premium cocoa and creating a better economic position for themselves. This research makes a strong case to focus on designing solutions using the principles of two-sided markets, service platforms, stakeholders and business models, to include the world’s poor in the global economy.Infrastructure Systems & ServicesTechnology, Policy and Managemen
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