1,720,963 research outputs found
Triplex-mediated analysis of cytosine methylation at CpA sites in DNA
No full textModified triplex-forming oligonucleotides distinguish 5-methyl cytosine from unmethylated cytosine in DNA duplexes by differences in triplex melting temperatures. The discrimination is sequence-specific; dramatic differences in stabilisation are seen for CpA methylation, whereas CpG methylation is not detected. This direct detection of DNA methylation constitutes a new approach for epigenetic analysis
CG base pair recognition within DNA triple helices using N-methyl-3H-pyrrolo[2,3-d]pyrimidin-2(7H)-one nucleoside analogues
No full textTriplex-mediated recognition of Py.Pu base pairs in DNA is a greater challenge than for Pu.Py base pairs as fewer hydrogen bonds are presented for binding in the major groove. Initial studies on m-aminophenyl-modified analogues of the bicyclic nucleoside N-methyl-3H-pyrrolo[2,3-d]pyrimidin-2(7 H)-one suggest that selective recognition of the CG base pair is possible
Programmed assembly of peptide-functionalized gold nanoparticles on DNA templates
No full textWe present a novel nanoparticle building block system based on the interactions between short synthetic oligonucleotides and peptides. Gold nanoparticles coated with DNA-binding peptides can be attached to self-organized oligonucleotide templates to formulate well-ordered structures of nanoparticles. By regulating the amount of DNA-binding peptide attached to the nanoparticle surface and using specifically designed oligonucleotides, the nanoparticle assembly can be controlled to form dimers, trimers, and adjustable-length nanoparticle chains as well as more complex structures.<br/
Reversible ligation of programmed DNA-gold nanoparticle assemblies
Get PDFWe demonstrate a new method to reversibly cross-link DNA-nanoparticle dimers, trimers, and tetramers using light as an external stimulus. A DNA interstrand photo-cross-linking reaction is possible via ligation of a cyano-vinyl carbazole nucleoside with an opposite thymine when irradiated at 365 nm. This reaction results in nanoparticle assemblies that are not susceptible to DNA dehybridization conditions. The chemical bond between the two complementary DNA strands can be reversibly broken upon light irradiation at 312 nm. This is the first example of reversible ligation in DNA-nanoparticle assemblies using light and enables new developments in the field of programmed nanoparticle organization
Self-assembled DNA-based fluorescence waveguide with selectable output
No full textUsing the principle of self-assembly, a fluorescence-based photonic network is constructed with one input and two spatially and spectrally distinct outputs. A hexagonal DNA nanoassembly is used as a scaffold to host both the input and output dyes. The use of DNA to host functional groups enables spatial resolution on the level of single base pairs, well below the wavelength of light. Communication between the input and output dyes is achieved through excitation energy transfer. Output selection is achieved by the addition of a mediator dye intercalating between the DNA base pairs transferring the excitation energy from input to output through energy hopping. This creates a tool for selective excitation energy transfer on the nanometer scale with spectral and spatial control. The ability to direct excitation energy in a controlled way on the nanometer scale is important for the incorporation of photochemical processes in nanotechnology
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Potent triple helix stabilization by 5?,3?-modified triplex-forming oligonucleotides
No full textAnthraquinone and pyrene analogues attached to the 3 and/or 5 termini of triplex-forming oligonucleotides (TFOs) by various linkers increased the stability of parallel triple helices. The modifications are simple to synthesize and can be introduced during standard solid-phase oligonucleotide synthesis. Potent triplex stability was achieved by using doubly modified TFOs, which in the most favourable cases gave an increase in melting temperature of 30 °C over the unmodified counterparts and maintained their selectivity for the correct target duplex. Such TFOs can produce triplexes with melting temperatures of 40 °C at pH 7 even though they do not contain any triplexstabilizing base analogues. These studies have implications for the design of triplex-forming oligonucleotides for use in biology and nanotechnology
CG base pair recognition within DNA triple helices by modified N-methylpyrrolo-dC nucleosides
No full text3-Aminophenyl-modified analogues of the bicyclic nucleoside N-methyl-3H-pyrrolo[2,3-d]pyrimidin-2(7H)-one were synthesised and incorporated directly into triplex-forming oligonucleotides in order to utilise their extended hydrogen bonding motif for recognition of the CG base pair. All analogues demonstrated strong binding affinity and very good selectivity for CG from pH 6.2 to 7.0; a marked improvement on previous modifications.<br/
Variations on the Author
Get PDF“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
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