1,720,962 research outputs found
Dual amplification strategy triggered by triple helix probe for the detection of microRNAs
No full textThe triple helix is an alternative structure adopted by nucleic acids based on Watson–Crick and Hoogsteen base pairings involving three strands in the correct orientation.
Since the stability of the triple helix stem can be higher even compared to longer duplexes, triple stranded DNA has been used in biosensing to build aptasensors or sensors for nucleic acids detection [1-4] and good sensitivity and selectivity have been generally observed. Moreover, different recognition elements specific for different targets can be included in the nucleic acid probe on a same single-stranded sequence, allowing in principle a universal assay strategy [5]. In the literature, the use of only one of the involved oligonucleotides for signal amplification and transduction is generally reported. We herein propose the use of both the triple helix forming strands in this process as this would give an advantage, such as the chance to combine different transduction approaches leading to a stronger and more reliable detection method. For this reason, we designed triple helix DNA probes specific for different microRNAs, in which both the sequences hidden in the stem would be available for subsequent signal amplification and transduction after target recognition (Fig. 1). To simply test the feasibility of our system to induce a double response triggered by the target, we designed hybridization chain reactions (HCR) [6] started by both the oligonucleotides involved in the triple helix. Furthermore, in our peculiar design, the self-assembled nanostructures resulting from a single recognition event can interact with each other forming bigger nanostructures, thus enhancing the recognition signal. After characterizing this strategy in solution (see Fig. 2), we are now in the process of implementing it in a biosensor platform
DNA triple helix triggered double amplification for miRNA detection
No full textTriple helix DNA has been exploited in building molecular switches, based on Watson–Crick and Hoogsteen base pairings, and adapted to several biosensing strategies for the detection of nucleic acids and aptasensors development [1-4]. The stability of the triple helix stem can be higher compared to longer duplex, and good sensitivity and selectivity have been generally observed in sensing. Moreover, different recognition elements specific for different targets can be included in the probe on a same single-stranded sequence, allowing in principle a universal assay strategy [5]. Examples in literature in using triple helix DNA probes usually employ only one of the involved oligonucleotides for signal amplification and transduction. We herein propose the use of both the triple helix forming strands in this process as this would give an advantage, such as the chance to combine different transduction approaches leading to a stronger and more reliable detection method. For this reason, we designed triple helix DNA probes specific for different microRNAs, in which both the sequences hidden in the stem would be available for subsequent signal amplification and transduction after target recognition. (Fig.1). To simply test the capacity of our system to induce a double response in the presence of the target, we designed hybridization chain reactions (HCR) [6] triggered by both the oligonucleotides involved in the triple helix. Furthermore, in our peculiar design, the self-assembled nanostructures resulting from a single recognition event can interact with each other forming bigger nanostructures, thus enhancing the recognition signal. After characterizing this strategy in solution (see Fig. 2), we are now in the process of implementing it in a biosensor platform
Hybridization chain reaction design and biosensor implementation
No full textDNA biosensors could overcome some of the common drawbacks of lab-based techniques for nucleic acids detection for diagnostics purposes. One of the main impediments for such applications of DNA biosensors is their lack of sensitivity: this can prevent their full exploitation in the diagnostic analytical field. DNA nanotechnology could enhance DNA biosensors and let them perform at the required high sensitivity. Well-designed, programmable self-assembly reactions can be triggered by a specific nucleic acid target. The Hybridization Chain Reaction (HCR) is a self-assembly strategy in which the target nucleic acid sequence triggers the formation of long nicked double-stranded DNA nanostructures. This can be performed in solution or on a surface, and the process can be coupled to different signal transduction schemes. We here describe the methods to design and test HCR reactions for the detection of different nucleic acid targets in solution and the procedures to exploit this strategy on surfaces with an electrochemical biosensing platform
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
A colorimetric assay of DNA methyltransferase activity based on peroxidase mimicking of DNA template Ag/Pt bimetallic nanoclusters
Full text linkDNA methylation catalyzed by DNA methyl transferase (MTase) is a significant epigenetic process for modulating gene expression. Abnormal levels of DNA MTase enzyme have been regarded as a cancer biomarker or a sign of bacterial diseases. We developed a novel colorimetric method to assay M.SssI MTase activity employing peroxidase-like activity of DNA template Ag/Pt NCs without using restriction enzymes. Based on inhibiting the peroxidase reaction that occurred in the TMB-H2O2system, in the presence of MTase, a highly sensitive and selective colorimetric biosensor was fabricated with a detection limit (LOD) of 0.05 U/mL and a linear range from 0.5 to 10 U/mL. The changes in absorption intensity were monitored to quantify the M.SssI activity. This strategy had a high selectivity over other proteins. Furthermore, it is also demonstrated that this method can be used for the evaluation and screening of inhibitors for DNA MTase
Surgical prevention of femoral neck fractures in elderly osteoporotic patients. A literature review
No full textFragility fractures of the femur are one of the major causes of morbidity and mortality worldwide. The incidence of new contralateral hip fractures in elderly osteoporotic patients ranges from 7 to 12% within 2 years after the first fracture. Secondary prevention can be divided in: pharmacological therapy based on the prescription of anti-osteoporotic drugs with different mechanism of action and nonpharmacological therapy which is based on modification of environmental risk factors, on a healthy diet with daily supplements of calcium and Vitamin D and calcium and on the use of hip protectors. Recently a new form of prevention is becoming achievable: surgical prevention; the rationale of surgical reinforcement is the need to increase the resistance of the femoral neck to the compression and distraction forces acting on it. In this paper we analyse all the experimental and "on the market" device available for the surgical prevention of femoral neck fracture
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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