1,720,958 research outputs found
DESIGN OF A HIGH-THROUGHPUT METHODFOR THE ASSESSMENT OF ENZYME ACTIVITY UPON ADSORPTION ONCLUSTER-ASSEMBLED NANOSTRUCTURED TITANIUM OXIDE FILMS
Full text linkControl of nanometre-scale topography of solid surfaces has opened the possibility to tailor the interactions between materials and biomolecules maintaining the biological functions of these molecules, a crucial aspect for diverse biomaterial applications. However, the primary mechanisms that dictate protein adsorption to topographical nanostructures are often poorly understood. We have addressed this question by scrutinizing the catalytic activity of immobilized serine-protease trypsin as product of its adsorption properties on cluster-assembled nanostructured titania films. Both, adsorption and activity of surface-bound enzymes were evaluated in parallel using innovative microarray-based methodology developed in this PhD work.
Trypsin adsorption analysis demonstrated an increment with roughness of Langmuir parameters – saturation uptake and equilibrium dissociation constant, that exceeded the contribution predicted by increase in sample specific area. This finding was interpreted by the clustering of protein molecules inside titania surface nanopores, a model proposed in our previous study of three non-enzymatic proteins. The growth of adsorbed trypsin activity with roughness was attributed to the increase in specific area of titania films, whereas the drop in specific activity resulted from steric hindrance of trypsin clustered inside titania nanopores.
This study has shed light on the topographical determinants of trypsin adsorption on nanostructured titania surfaces and its impact on trypsin activity. A novel method was developed elucidating the obstacles and specifics of protease immobilization by physisorption and suggesting possible routes to solve them. This methodology is directly applicable in biomaterial screening with respect to the functionality of immobilized enzymes and can be extended beyond the trypsin-nanostructured titania model
A simple lift-off-based patterning method for micro- and nanostructuring of functional substrates for cell culture
No full textThe ability to produce cell patterning through precise surface engineering has stimulated the development of cellular bioassays that offer new insights on the mechanisms of cell adhesion, proliferation, differentiation and molecular signaling pathways. Here we describe a simple micropatterning technique combining supersonic cluster beam deposition of nanostructured titania films on bovine serum albumin functionalized substrates. A standard lift-off process enables us to generate complementary micropatterns of hydrophobic bovine serum albumin (cell-repellent) and hydrophilic nanostructured TiO(x) (cell-adhesive). We demonstrate the selective PC12 cell adhesion and growth on biocompatible nanostructured TiO(x). We also observed that these functional micropatterned substrates promote a considerable enhancement of cell attachment and proliferation
Nanoscale roughness affects the activity of enzymes adsorbed on cluster-assembled titania films
No full textIn this study, we investigated how the adsorption properties governed by the nanometer-scale surface morphology of cluster-assembled titanium oxide films influence the catalytic activity of immobilized serine-protease trypsin. We developed an activity assay for the parallel detection of physisorbed enzyme activity and mass density of the adsorbed proteins in microarray format. The method combines a microarray-based technique and advanced quantitative confocal microscopy approaches based on fluorescent labeling of enzymes and covalent labeling of active sites of surface-bound enzymes. The observed diminishing trypsin binding affinity with increasing roughness, as opposed to the steep rise in its saturation uptake, was interpreted as heterogeneous nucleation-driven adsorption of trypsin at the rough nanoporous titania surface. The increase in relative activity of adsorbed trypsin is proportional to the fractional saturation of titania surfaces, expressed as percentage of saturation uptake. In turn, the specific activity, that is, the ratio of active proteins to the absolute number of adsorbed proteins, drops with growing saturation uptake and surface roughness, witnessing a reduction in the accessibility of enzyme active sites. Both geometrical constraints of titania nanopores and the clusterwise adsorption of trypsin were identified as the key factors underpinning the steric hindrance of the immobilized enzyme. These findings are relevant for the optimization of rough nanoporous surfaces as carriers of immobilized enzymes. The proposed activity assay is particularly advantageous in the screening of candidate materials for enzyme immobilization
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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