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Polietilenglicoli modificati e loro complessi supramolecolari con macromolecole biologicamente attive
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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
Hydrophobized PEG for unexposed aminoacid conjugation.
No full textPEGylation has been largely applied to ameliorate the pharmacokinetic, immunological and physicochemical properties of protein therapeutics (1). However, the therapeutic performance of the bioconjugates is strictly related to the PEG molecular weight and architecture, the extent of polymer conjugation and the conjugation site.
Aimed at generating derivatives with defined structural properties and high biological activity, few single site directed conjugation strategies have been set up (1, 2). Typically, site specific bioconjugates are obtained by terminal NH2 derivatization. Alternatively, PEG can be attached to infrequent aminoacids, namely Cys, which can also be properly introduced into the protein sequence by altering the DNA sequence encoding for the protein. However, Cys is usually located inside deep hydrophobic pockets that prevent the penetration of large hydrated molecules like PEG making difficult its modification. Though PEGylation is possible under controlled protein denaturation, the unfolding/re-folding process and the insertion of a hydrophilic macromolecule into a hydrophobic pocket can induce conformational protein alteration, which may compromise dramatically its activity and stability.
In order to conjugate low accessible protein aminoacids under native conditions, we prepared a new 20 kDa PEG derivative end functionalised with an hydrophobic linear chain made of 18 C. The new polymer PEG-C18-Mal [PEG-NHCO-(CH2)11-NHCO(CH2)5-Mal] was found to possess the same reactivity towards the thiol groups as the commercial PEG-maleimide. The ability to modify unexposed aminoacids was investigated by using rh-GCSF which contains a Cys17 that can not be modified by commercial PEG-maleimide or PEG-vinylsulfone. Under native conditions, the PEGylation reaction was found to proceed slowly to yield over 55% Cys conjugation in about 140 hours. The higher efficacy in Cys bioconjugation can be ascribed to a better thermodynamic interaction between PEG-C18-Mal and the hydrophobic aminoacids surrounding the protein pocket, and to extended stability of the PEG maleimide group by micelles formation. Circular dichroism analysis showed that the PEGylation did not induce significant alteration of tertiary structure of the native protein. A stability study carried out by protein incubation at 37°C showed that the polymer conjugation yielded a derivative with lower stability (aggregation half life 60 hrs) as compared to the native protein (aggregation half life higher than 100 hrs). However, rh-GCSF-PEG conjugate obtained with the new polymer under native conditions was much more stable than the counterpart obtained under denaturant conditions either with the new or the commercial PEG-maleimide (aggregation half life 30-90 min).
The present study shows that end hydrophobized PEGs can be successfully used for modification of inaccessible aminoacids, which are located into deep hydrophobic pockets of the protein. The modification can be performed under physiological conditions thus avoiding protein unfolding which may be detrimental for the protein activity and stability
Poly-hydroxyethylaspartamide supramolucular system for prolonged rh-GH delivery.
No full textPurpose: Two PHEA self-assembling derivatives were developed for parenteral administration of rh-GH.
Results: PHEA-C16 and PHEA-PEG5-C16 yielded 12.1±1.3% and 8.5±0.4% protein/polymer (w/w) loading, respectively. The Scatchard and Klotz analysis showed that rh-GH associates more tightly and is released more slowly from PHEA-C16 as compared to PHEA-PEG5-C16. In vivo, the polymer association prolonged the drug absorption (tmax) and increased the bioavailability (AUC) as compared to the free protein. The protein bioavailability obtained with PHEA-PEG5-C16 was higher than that obtained with PHEA-C16 and increased as the protein/polymer ratio increased.
Conclusions: amphiphilic PHEAs can be successfully exploited to yield sustained protein delivery. Modulation of the polymer composition and protein/polymer ratio allows the optimisation of the protein association and release kinetic to yield effective protein delivery
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
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