1,720,959 research outputs found
Recombinant biomaterials: are they worth the trouble?
No full textIntroduction
Proteins play a crucial role in the field of biomaterials due to their inherent biocompatibility, bioactivity, and ability to interact with biological systems. As structural and functional components of natural tissues, proteins such as collagen, gelatin, fibrin, and silk fibroin are widely used in tissue engineering, drug delivery, and medical implants. However, the biological origin of these materials also raises questions related to batch-to-batch variability, the risk of disease transfer or ethical considerations (1). As a result, recombinant proteins are often proposed as a workaround since the tightly regulated expression of human proteins in e.g., microbial host systems rules out these risks. However, designing and expressing recombinant proteins is not straightforward and requires a good understanding of the necessary steps to translate a gene of interest into purified proteins that can be used as a biomaterial (2). The numerous interdependent experimental parameters make this field difficult to navigate for biomaterials scientists new to recombinant proteins. This contribution presents a systematic approach for the expression of elastin-like proteins (ELPs) that will help avoid common pitfalls and increase protein yield and purity.
Materials and Methods
Plasmids encoding ELPs were generated based on a previously described method (3): short oligonucleotide fragments were fused together and ligated into a pUC18 cloning vector, after which the full construct was transferred to a pET15b expression vector used to transform the typical expression strain E. coli BL21(DE). Expression conditions reported in literature were applied, followed by isolating the ELPs from the cell lysate using immobilised metal affinity chromatography (IMAC) or inverse transition cycling (ITC).
Results
Despite reproducing protocols from literature, overexpression of the ELPs was not observed in SDS-PAGE analyses. Moreover, no apparent difference between induced (+1mM IPTG) and non-induced cultures could be observed. Purifying the cell lysate resulted in minimal recovery of the protein of interest (PoI). To increase the expression yields alternative expression strains were considered together with adapting the experimental parameters, but this only resulted in minimal improvements. By starting from scratch and not relying on recommendations from literature, protein yield started to increase. By changing the sequence, the expression vector, replacing the expression strain and optimising the expression parameters via the Design of Experiments, expression yields comparable to literature reports were finally obtained.
Discussion
The results indicate that expression parameters depend on the primary sequence of the PoI, making it difficult to reproduce experimental results and discouraging others from entering the field. Surprisingly, low reproducibility was also observed for expression vectors obtained from the Addgene repository and linked to the original scientific publication. This hints at an important yet unidentified experimental parameter currently not included in published method sections.
Conclusions
It can be challenging to produce recombinant biomaterials, even for scientists familiar with recombinant DNA technology. However, many of these difficulties can be mitigated by applying a systematic approach tilting the balance in favour of the design freedom and unparallelled control that recombinant biomaterials offer, making recombinant biomaterials worth the trouble
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
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
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