1,720,968 research outputs found
PEPTIDE-POLYMER CONJUGATES AS TOOLS TO SELECTIVELY TARGET EGFR
Full text linkNanoparticles (NPs) made of biodegradable and biocompatible polymers present several advantages as carriers for therapeutics. Targeted polymeric NPs, able to hit specific tissues and cells, can be obtained by synthesis of hybrid or biointegrated nanosystems where the combination of polymers with biomolecules such as peptides, proteins, or monoclonal antibodies offers opportunities to design precise and versatile nanoscale systems. The central challenge towards these “smart” materials is represented by the optimal interplay of biophysicochemical parameters that confer molecular targeting, immune evasion, and optimal drug release, and allow to overcome the physiological barriers in vivo.
The epidermal growth factor receptor (EGFR) is a cell-surface receptor of extracellular protein ligands of the epidermal growth factor family. Mutations that lead to EGFR overexpression or overactivity have been associated with a wide spectrum of human cancers of epithelial origin, including breast and colorectal cancers, and with autoimmune disorders like rheumatoid arthritis. Recently, several studies have reported the successful identification, by screening phage display libraries, of a peptide ligand, named GE11 (YHWYGYTPQNVI), with high binding capacity to EGFR but with low mitogenic activity.
Poly(gamma-glutamic acid) (gamma-PGA) is an extracellular bacterial water-soluble polymer with variable molecular weight produced by several members of the genus Bacillus, composed of D and/or L-glutamic acid monomers, connected by amide bonds between alpha-amino and gamma-carboxyl groups. gamma-PGA is readily biodegraded by a good number of bacteria, it is non-immunogenic and completely innocuous and so it seems to meet most of the requirements of polymers for drug delivery. In addition, it bears pendant carboxylic groups in α-position which are available for chemical derivatization allowing the modification of its molecular properties or the attachment of biologically active molecules.
The use of gamma-PGA, however, presents some inherent and not negligible issues. First of all, chemical modification of the material is very arduous: this is a consequence of its structure but also of its scarce solubility in most organic solvents. Consequently, studies are necessar to find a feasible and efficient way to exploit it for drug delivery purposes.
This PhD work aimed to find a way to valorize gamma-PGA peculiar characteristics in drug delivery field, particularly in the preparation of GE11 directed nanocarriers. We operated on two different sides: on one hand we performed intense studies on the biopolymer exploring its chemical-physical properties (mainly MW and solubility), its structure and its reactivity. On the other hand we studied and optimized methods to functionalize a well known and widely used biopolymer, poly lactic-co-glycolic acid (PLGA), with peptides. Starting from these conjugates we also prepared and characterized nanoparticles intended to be used as a drug delivery tools to EGFR overexpressing cells
Chemistry of α-mangostin : studies on the semisynthesis of minor xanthones from Garcinia mangostana
Full text linkα-Mangostin is the major prenylated xanthone from Garcinia mangostana and it has been used also in recent times as starting material for the semisynthetic preparation of various biologically active derivatives. Its structure is characterised by the presence of few functional groups amenable to chemical manipulations, but present in the molecule in multiple instances (three phenolic hydroxyl groups, two prenyl chains and two unsubstituted aromatic carbons). This study represents a first approach to the systematic investigation of the reactivity of α-mangostin and describes the semisynthesis of some minor xanthones isolated from G. mangostana
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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