1,721,015 research outputs found
Dual switchable CRET-induced luminescence of CdSe/ZnS quantum dots (QDs) by the hemin/G-quadruplex-bridged aggregation and deaggregation of two-sized QDs
No full textThe hemin/G-quadruplex-catalyzed generation of chemiluminescence through the oxidation of luminol by H2O2 stimulates the chemiluminescence resonance energy transfer (CRET) to CdSe/ZnS quantum dots (QDs), resulting in the luminescence of the QDs. By the cyclic K+-ion-induced formation of the hemin/G-quadruplex linked to the QDs, and the separation of the G-quadruplex in the presence of 18-crown-6-ether, the ON-OFF switchable CRET-induced luminescence of the QDs is demonstrated. QDs were modified with nucleic acids consisting of the G-quadruplex subunits sequences and of programmed domains that can be cross-linked through hybridization, using an auxiliary scaffold. In the presence of K+-ions, the QDs aggregate through the cooperative stabilization of K+-ion-stabilized G-quadruplex bridges and duplex domains between the auxiliary scaffold and the nucleic acids associated with the QDs. In the presence of 18-crown-6-ether, the K+-ions are eliminated from the G-quadruplex units, leading to the separation of the aggregated QDs. By the cyclic treatment of the QDs with K+-ions/18-crown-6-ether, the reversible aggregation/deaggregation of the QDs is demonstrated. The incorporation of hemin into the K+-ion-stabilized G-quadruplex leads to the ON-OFF switchable CRET-stimulated luminescence of the QDs. By the mixing of appropriately modified two-sized QDs, emitting at 540 and 610 nm, the dual ON-OFF activation of the luminescence of the QDs is demonstrated
Toward the specificity of bare nanomaterial surfaces for protein corona formation
Full text linkAiming at creating smart nanomaterials for biomedical applications, nanotechnology aspires to develop a new generation of nanomaterials with the ability to recognize different biological components in a complex environment. It is common opinion that nanomaterials must be coated with organic or inorganic layers as a mandatory prerequisite for applications in biological systems. Thus, it is the nanomaterial surface coating that predominantly controls the nanomaterial fate in the biological environment. In the last decades, interdisciplinary studies involving not only life sciences, but all branches of scientific research, provided hints for obtaining uncoated inorganic materials able to interact with biological systems with high complexity and selectivity. Herein, the fragmentary literature on the interactions between bare abiotic materials and biological components is reviewed. Moreover, the most relevant examples of selective binding and the conceptualization of the general principles behind recognition mechanisms were provided. Nanoparticle features, such as crystalline facets, density and distribution of surface chemical groups, and surface roughness and topography were encompassed for deepening the comprehension of the general concept of recognition patterns
Recent Advances in the Synthesis and Functions of Reconfigurable Interlocked DNA Nanostructures
No full textInterlocked circular DNA nanostructures, e.g., catenanes or rotaxanes, provide functional materials within the area of DNA nanotechnology. Specifically, the triggered reversible reconfiguration of the catenane or rotaxane structures provides a means to yield new DNA switches and to use them as dynamic scaffolds for controlling chemical functions and positioning functional cargoes. The synthesis of two-ring catenanes and their switchable reconfiguration by pH, metal ions, or fuel/anti-fuel stimuli are presented, and the functions of these systems, as pendulum or rotor devices or as switchable catalysts, are described. Also, the synthesis of three-, five-, and seven-ring catenanes is presented, and their switchable reconfiguration using fuel/anti-fuel strands is addressed. Implementation of the dynamically reconfigured catenane structures for the programmed organization of Au nanoparticle (NP) assemblies, which allows the plasmonic control of the fluorescence properties of Au NP/fluorophore loads associated with the scaffold, and for the operation of logic gates is discussed. Interlocked DNA rotaxanes and their different synthetic approaches are presented, and their switchable reconfiguration by means of fuel/anti-fuel strands or photonic stimuli is described. Specifically, the use of the rotaxane as a scaffold to organize Au NP assemblies, and the control of the fluorescence properties with Au NP/fluorophore hybrids loaded on the rotaxane scaffold, are introduced. The future prospectives and challenges in the field of interlocked DNA nanostructures and the possible applications are discussed
Au nanoparticle/DNA rotaxane hybrid nanostructures exhibiting switchable fluorescence properties
No full textThe preparation of a DNA rotaxane consisting of a circular nucleic acid interlocked, through hybridization, on a nucleic acid axle and stoppered by two 10-nm-sized Au nanoparticles (NPs) is described. By the tethering of 5-nm- or 15-nm-sized Au NPs on the ring, the supramolecular structure of the rotaxane is confirmed. Using nucleic acids as "fuels" and "anti-fuels", the cyclic and reversible transition of the rotaxane ring across two states is demonstrated. By the functionalization of the ring with fluorophore-modified nucleic acids in different orientations, the transitions of the rings between the sites are followed by fluorescence quenching or surface-enhanced fluorescence. The experimental results are supported by theoretical modeling. © 2013 American Chemical Society
Chiroplasmonic DNA-based nanostructures
No full textChiroplasmonic properties of nanoparticles, organized using DNA-based nanostructures, have attracted both theoretical and experimental interest. Theory suggests that the circular dichroism spectra accompanying chiroplasmonic nanoparticle assemblies are controlled by the sizes, shapes, geometries and interparticle distances of the nanoparticles. In this Review, we present different methods to assemble chiroplasmonic nanoparticle or nanorod systems using DNA scaffolds, and we discuss the operations of dynamically reconfigurable chiroplasmonic nanostructures. The chiroplasmonic properties of the different systems are characterized by circular dichroism and further supported by high-resolution transmission electron microscopy or cryo-transmission electron microscopy imaging and theoretical modelling. We also outline the applications of chiroplasmonic assemblies, including their use as DNA-sensing platforms and as functional systems for information processing and storage. Finally, future perspectives in applying chiroplasmonic nanoparticles as waveguides for selective information transfer and their use as ensembles for chiroselective synthesis are discussed. Specifically, we highlight the upscaling of the systems to device-like configurations
Metal nanoparticle-functionalized DNA tweezers: From mechanically programmed nanostructures to switchable fluorescence properties
No full textDNA tweezers are modified with two 10-nm sized Au NPs and one 5-nm sized Au NP. Upon treatment of the tweezers with fuel and antifuel nucleic acid strands, the switchable closure and opening of the tweezers proceed, leading to the control of programmed nanostructures of the tethered NPs. The tweezers are further modified with a single 10-nm sized nanoparticle, and a fluorophore unit (Cy3), positioned at different distinct sites of the tweezers. The reversible and cyclic fluorescence quenching or fluorescence enhancement phenomena, upon the dynamic opening/closure of the different tweezers, are demonstrated. © 2013 American Chemical Society
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
Anestesia generale nella pratica odontostomatologica ambulatoriale Esperienza personale di 183 casi
No full textVariations 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
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