1,721,077 research outputs found
PNA: applications and perspectives in the regulation of gene expression
No full textThe structure, function and applications of Peptide Nucleic Acids as decoy and miRNA inhibitors are discussed
New peptide nucleic acid analogues: synthesis and applications
No full textPeptide nucleic acids are oligonucleotide mimics characterised by high
chemical and enzymatic stability, high specificity and affinity toward
complementary DNA/RNA. The lack of charge and polar groups in the
backbone decrease their solubility in aqueous environment and their ability
to cross cell membranes, reducing their performance in in vivo applications.
To improve solubility, increase affinity and specificity of binding and to
control recognition between nucleic acids, several analogues bearing
modifications on the nucleobase, nucleobase-backbone linker and on
the backbone were synthesised. This paper describes the synthesis and
applications of Peptide nucleic acid analogues and discusses the potential of
analogues for which no application is reported
Interactions of antimicrobial peptides with bacterial membrane model systems and with whole E. coli bacterial cells
No full textAntimicrobial peptides are a primitive component of the innate immune system, produced by organisms after the invasion of pathogens. Extensive studies have led to the discovery of a wide variety of such peptides, from diverse organisms, showing different activities and structures. Studies on peptides secreted on the frog skin allowed the characterization of a class of short peptides, temporins, characterized by strong antimicrobial activity against Gram-positive bacteria and fungi. We have recently developed a Temporin B analogue, named TB_G6AKK, composed of natural amino acids, showing activity at low concentrations either against Gram-positive and Gram-negative bacteria (Avitabile et al 2013, in press). TB_G6AKK interacts with E.coli LPS, as demonstrated by fluorescence, CD and ITC studies, and folds as a kinked helix upon interaction with the E.coli LPS, as demonstrated by NMR. Studies aimed to characterize the ability of this peptide to kill pathogens as Pseudomonas aeruginosa, whose infection is cause of complications in patients suffering cystic fibrosis are currently in progress. In order to deeply characterize the interactions of such peptide with the bacterial cells, as LPS is only one of the components of the bacterial cell wall, we started to explore the secondary structure of the peptide in the presence of whole bacterial cells by CD and by fluorescence the binding of the peptide to the cells. Analysis of the data obtained with cells and comparison with those obtained with LPS will help us to understand the effectiveness of the LPS as a model system to represent the cells Gram negative bacteria
Conformational features of peptidic nucleic acids for the rational design of biologically active PNAs and hybrids PNA-oligonucleotides
No full textThe search for new oligonucleotides with improved properties represents an important step for the development of oligonucleotides as powerful biomolecular tools, antisense and antigene agents, molecular probes and biosensors. One of the most interesting of the new derivatives is Peptide Nucleic Acid (PNA), an analogue of DNA in which the backbone is a pseudopeptide rather than a sugar. PNA mimics the behaviour of DNA and binds complementary nucleic acid strands, with higher affinity and specificity than corresponding oligonucleotides. The unique properties of PNA open up novel molecular biology and biochemistry applications that are unachievable with traditional oligonucleotides and peptides. The non-charged nature of the PNA backbone is an important feature leading to higher thermal stability of PNA/DNA duplexes compared to DNA/DNA duplexes and stability of PNA duplexes with DNA independent of salt concentration. PNA oligomers are resistant to degradation by enzymes, and the lifetime of these compounds is extended both in vivo and in vitro. The direction of rational drug design of new PNA with specific functions depends critically on understanding the basic principles of specificity of biomolecular recognition for this class of molecules. Thus, the comparative analysis of conformational data on PNA/PNA, PNA/RNA, PNA/DNA duplexes and PNA2/DNA triplex represents the starting point for the design of new PNAs. In addition, the investigation of modified PNAs and PNA/DNA chimeras may provide a new generation of nucleic acid mimetics with large-scale application in biological systems
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
- …
