1,721,034 research outputs found
SERS characterization of self-assembling oligopeptides for tissue engineering
No full textEight alternating polar/non-polar peptides derived from the self-assembling peptide EAK-16 (Ac- AEAEAKAKAEAEAKAK-NH2) were examined in comparison with the EAK-16 parent form (peptide 1), both as-synthesized and after gamma-radiation treatment in oxidative environment (formation of ∙OH radical), to mimic the inflammation process occurring during the first phases of implantation. The peptides were studied for their possible use as biomimetic materials [1] due to their self-assembling properties and to the presence, in two of them, of the RGD sequence, an active modulator of cell adhesion. Previous investigations on titanium surfaces [2] demonstrated that some oligopeptides, i.e. EAK16 (peptide 1), peptide 3 (obtained by K→Orn substitution), peptide 5 (A→Abu substitution), peptide 7 (insertion at the N-terminus of the RGD sequence), and peptide 8 (RGD insertion and “scrambling” of the sequence) were not severely affected by the treatment and retained their prevalent structure. The other peptides, i.e. peptide 2 (obtained by E→D substitution), peptide 4 (E→D and K→Orn substitutions) and peptide 6 (A→Y substitution), underwent significant conformational changes (i.e. increase in the á-helix content). Interestingly, these same last 3 peptides were severely affected also by the radical attack induced by irradiation [3], changing their secondary structure and lateral chains interactions.
To better investigate the interaction between peptides and metallic surfaces, we carried out SERS experiments on silver nanoparticles. As regards the as-synthesized peptides, all of them interacted with the Ag colloid by the COO- lateral groups of aspartic or glutamic acid residues. Other observed interaction sites were:
- NH2/NH3+ of basic aminoacidic residues (lysine and/or ornithine) in peptides 3, 4 and 7;
- amide group in peptides 1, 2, 4 and 8;
- the aromatic ring of Tyr side chains in peptide 6.
As regards the peptides after irradiation, they still interact through the before-mentioned groups; however, those undergoing conformational changes showed differences in band intensities and positions (see Fig.1)
References
[1] A. Tinti, M. Di Foggia, P. Taddei, A. Torreggiani, M. Dettin, C. Fagnano, J. Raman Spetrosc. 39, 250 (2008)
[2] M. Di Foggia, P. Taddei, A. Torreggiani, M. Dettin, A. Tinti, J. Raman Spetrosc. 42, 276 (2011)
[3] M. Di Foggia, P. Taddei, A. Torreggiani, M. Dettin, A. Tinti, J. Raman Spetrosc. 44, 1446 (2013
Human vitronectin-derived peptide covalently grafted onto titanium surface improves osteogenic activity: a pilot in vivo study on rabbits
No full textPeptide and protein exploitation for the biochemical functionalization of biomaterial surfaces allowed fabricating biomimetic devices able to evoke and promote specific and advantageous cell functions in vitro and in vivo. In particular, cell adhesion improvement to support the osseointegration of implantable devices has been thoroughly investigated. This study was aimed at checking the biological activity of the (351-359) human vitronectin precursor (HVP) sequence, mapped on the human vitronectin protein; the peptide was covalently linked to the surface of titanium cylinders, surgically inserted in the femurs of New Zealand white rabbits and analyzed at short experimental time points (4, 9, and 16 days after surgery). To assess the osteogenic activity of the peptide, three vital fluorochromic bone markers were used (calcein green, xylenol orange, and calcein blue) to stain the areas of newly grown bone. Static and dynamic histomorphometric parameters were measured at the bone-implant interface and at different distances from the surface. The biological role of the (351-359)HVP sequence was checked by comparing peptide-grafted samples and controls, analyzing how and how much its effects change with time across the bone regions surrounding the implant surface. The results obtained reveal a major activity of the investigated peptide 4 days after surgery, within the bone region closest to the implant surface, and larger bone to implant contact 9 and 16 days after surgery. Thus, improved primary fixation of endosseous devices can be foreseen, resulting in an increased osteointegration
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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