130,531 research outputs found
Expression and Purification of Diphtheria Toxin Variant CRM197 in Escherichia coli
No full textThe cross reacting material 197 (CRM197) is a nontoxic variant of the diphtheria toxin (DTx) featuring identical immunological properties and similar ability to bind the heparin-binding epidermal growth factor (HB-EGF). The only difference between CRM197 and DTx is a single amino acid substitution at position 52 (glutamic acid instead of glycine). Due to the absence of toxicity, and to its strong inflammatory-immunological property, the CRM197 protein is currently used in several conjugate vaccines. Diphtheria toxin and other related CRM proteins are generally produced using cultures of Corynebacterium diphteriae infected by specific β-phages carrying the tox gene (wt or mutated, respectively).
Here we propose a new and alternative procedure for the production of CRM197 using Escherichia coli as host strain. This process presents several advantages: a reduced time for the coltivation of bacteria; a simple culture medium; the safety of E. coli bacteria compared to C. diptheriae. To this aim, a synthetic gene coding for CRM197 and optimized for E. coli codon usage, was cloned into a specific vector (pET9a) based on the T7 RNA polymerase system. The over-expression was induced in BL21AI E. coli strain simply by adding arabinose to the culture medium. The recombinant protein was insoluble and always found inside protein aggregates, which were solubilized using urea as denaturant. After the expression and solubilization steps, the refolding and purification conditions were experimentally assayed to define a simple procedure for the production of CRM197 in a pure and active form. In particular, the recombinant protein was purified by two different chromatographic steps (affinity and gel-filtration chromatography) and the purity of the final preparation reached up to 95%
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Clinical management of rivaroxaban-treated patients
No full textIntroduction: Until recently, only vitamin K antagonists (VKAs) were used for long-term anticoagulation. New oral anticoagulants, with pharmacokinetic and pharmacodynamic characteristics different to VKAs, are now available for some indications. Rivaroxaban (Xarelto (R)) is an oral Factor Xa inhibitor approved in many countries for long-term treatment of patients with atrial fibrillation or venous thromboembolism. This article is addressed to all professionals involved in the management of treated patients to highlight the characteristics of rivaroxaban and provide practical guidance on management of treated patients. Areas covered: This article is based on a consensus of specialists involved in the management of anticoagulant treatment, including thrombosis experts, cardiologists, neurologists, emergency medicine specialists, and general practitioners. The authors performed a nonsystematic review of the literature, and expressed guidance statements based on the results of the review as well as personal experience. Expert opinion: Availability of new anticoagulant drugs, including rivaroxaban, is an important step forward to allow easier, more effective, and safer long-term anticoagulation in patients in whom adequate anticoagulation is currently denied due to the limitations of VKAs. However, given their totally new properties, associated risks, and expected broad clinical use, expert professionals and manufacturers must urgently tackle a series of issues
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
Overexpression and purification of the recombinant diphtheria toxin variant CRM197 in Escherichia coli
No full textThe expression of the recombinant diphtheria toxin mutant CRM197 in bacteria other than Corynebacterium diphtheriae has proven to be difficult. Here we propose a new and alternative procedure for the production of full-length CRM197 in Escherichia coli. The present study relates specifically to the expression of an artificial sequence and to a method for the isolation and purification of the corresponding protein. In particular, a synthetic gene coding for CRM197, bearing a short histidine tag and optimized for E. coli codon usage, was cloned in the pET9a vector. Accordingly, the over-expression of the protein was simply induced with arabinose in E. coli BL21AI. The recombinant protein was insoluble and always found inside protein aggregates, which were solubilised using urea. Surprisingly, the expression of CRM197, devoid of the short tag, always failed. Following a refolding step, the his-tagged CRM197 was purified by affinity and gel-filtration chromatography and the purity of the final preparation reached 95%. Interestingly, the recombinant protein features DNase activity, indicating that the presence of the tag is not affecting its biochemical properties. However, the removal of the synthetic tag could be easily obtained by incubating the target protein with a proper quantity of a commercial enterokinase
The R&D Tax Incentives
No full textThis article sets out some background information and reflections of the author on the R&D tax incentive schemes included in the Common Corporate Tax Base (CCTB) Proposal. In particular the author analyzes the stimulus to private R&D through ad hoc tax incentives included in the CCTB Proposal and dives into the actual provisions included in the Proposal highlighting the most relevant issues connected with their design and interpretation. Moreover, the author explores the interaction between the CCTB Proposal and the granting by Member States of domestic R&D tax incentives
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