1,720,973 research outputs found
PNA-functionalized magnetic microbeads as substrates for enzyme-labelled voltammetric genoassay for DNA sensing applied to identification of GMO in food
No full textA novel enzyme-labelled voltammetric magnetogenoassay for DNA sensing based on the use of carboxyl-surface coated magnetic microbeads functionalized with PNA probes and subsequent read-out on screen-printed electrode (SPE) substrates was developed. The assay was validated for determination of non-amplified genomic DNA from genetically modified Roundup Ready soy. Outstanding performance with respect to other genoassays requiring preliminary amplification of target DNA via PCR was demonstrated. The analytical performance was also improved compared to previous methods based on the immobilization of the same PNA probes on SPE substrates, since the method was found capable of achieving LOD and LOQ of 415 fM and 995 fM, respectively. The ability of the magnetogenoassay to detect the presence of Roundup Ready soy DNA sequence was tested on genomic DNA extract from European Reference Material soy flours, demonstrating the capability of the method to match the European Union regulation for labelling of food containing a percentage of GM products greater than 0,9%
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
Building on the peptide nucleic acid (PNA) scaffold: a biomolecular engineering approach
No full textPeptide nucleic acids (PNAs) are polyamide analogues of nucleic acids, very effective in terms of affinity and selectivity in DNA/RNA recognition. As other supramolecular entities, the PNA structure has been an interesting scaffold for the development of new molecules, aimed to DNA and RNA recognition, with improved or completely new properties. This review describes recent work, with the aim of describing how the design of these molecules has evolved in recent years, using increasingly effective tools, from simple crystal structure analysis to molecular dynamics and metadynamics. Modified PNA with additional modules appended, either on the backbone or on the nucleobase, are described. Polyfunctional molecules with both backbone and nucleobase modification are then considered. Finally, recent examples of architectures obtained by conjugation of PNAs to inorganic nanostructures as cargo systems for diagnostics and nano-biotechnology are presented
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
A Bifunctional Monomer for On-Resin Synthesis of Polyfunctional PNAs and Tailored Induced-Fit Switching Probes
Full text linkA synthetic
strategy for the production of polyfunctional PNAs
bearing substituent groups both on the nucleobase and on the backbone
C5 carbon of the same monomer is described; this is based on the use
of a tris-orthogonally protected monomer and subsequent solid-phase
selective functionalization. This strategy can be used for synthesizing
PNAs that are not readily accessible by use of preformed modified
monomers. As an example, a PNA-based probe that undergoes a switch
in its fluorescence emission upon hybridization with a target oligonucleotide,
induced by tailor-made movement of two pyrene substituent groups,
was synthesized
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
Novel amperometric genosensor based on peptide nucleic acid (PNA) probes immobilized on carbon nanotubes-screen printed electrodes for the determination of trace levels of non-amplified DNA in genetically modified (GM) soy
Full text linkA novel amperometric genosensor based on PNA probes covalently bound on the surface of Single Walled Carbon
Nanotubes – Screen Printed Electrodes (SWCNT-SPEs) was developed and validated in samples of non-amplified
genomic DNA extracted from genetically modified (GM)-Soy. The sandwich assay is based on a first recognition
of a 20-mer portion of the target DNA by a complementary PNA Capture Probe (CP) and a second hybridization
with a PNA Signalling Probe (SP), with a complementary sequence to a different portion of the target DNA. The
SP was labelled with biotin to measure current signal by means of a final incubation of an Alkaline Phosphatasestreptavidin
conjugate (ALP-Strp). The electrochemical detection was carried out using hydroquinone diphosphate
(HQDP) as enzymatic substrate. The genoassay provided a linear range from 250 pM to 2.5 nM, LOD of
64 pM and LOQ of 215 pM Excellent selectivity towards one base mismatch (1-MM) or scrambled (SCR) sequences
was obtained. A simple protocol for extraction and analysis of non-amplified soybean genomic DNA
without sample treatment was developed and validated. Our study provides insight into how the outstanding
recognition efficiency of PNAs can be combined with the unique properties of CNTs in terms of signal response
enhancement for direct detection of genomic DNA samples at the level of interest without previous amplificatio
Tuning the conformational flexibility of quinoxaline cavitands for complexation at the gas-solid interface
Full text linkThe selectivity and efficiency of benzene and toluene uptake at the gas-solid interface by quinoxaline cavitands is strongly enhanced by partial rigidification of the receptor cavity and immobilization of the cavitand onto silica gel particles
Hollow Core Inhibited Coupling Fibers for Biological Optical Sensing
No full textIn this work, we report how tube lattice hollow-core fibers can be successfully used to build sensors for molecule detection. The inner silica surface of the fiber is functionalized and coated with a probe layer, which permits to bond only with a particular molecule (the target). When the fiber is infiltrated with a solution containing the target an additional layer is crated on the silica surface causing a redshift of the fiber transmission spectrum. The technique does not require any additional transducer component such as Bragg gratings, amplifying techniques such as nano-particles nor coherent sources. It simply consists of the measurement of the transmission spectrum of a piece of fiber some tens centimeters long. The principle is validated with experimental results showing the detection of streptavidin protein. A solution containing streptavidin was flowed trough the hollow core of the fiber coated with biotine. The measurement of the transmitted spectrum before and after the infiltration showed the presence of a some nanometer thick bio-layer
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