1,720,979 research outputs found
Supramolecular Binding with Lectins: A New Route for Non-Covalent Functionalization of Polysaccharide Matrices
Full text linkThe chemical functionalization of polysaccharides to obtain functional materials has been of great interest in the last decades. This traditional synthetic approach has drawbacks, such as changing the crystallinity of the material or altering its morphology or texture. These modifications are crucial when a biogenic matrix is exploited for its hierarchical structure. In this work, the use of lectins and carbohydrate-binding proteins as supramolecular linkers for polysaccharide functionalization is proposed. As proof of concept, a deproteinized squid pen, a hierarchically-organized β-chitin matrix, was functionalized using a dye (FITC) labeled lectin; the lectin used was the wheat germ agglutinin (WGA). It has been observed that the binding of this functionalized protein homogenously introduces a new property (fluorescence) into the β-chitin matrix without altering its crystallographic and hierarchical structure. The supramolecular functionalization of polysaccharides with protein/lectin molecules opens up new routes for the chemical modification of polysaccharides. This novel approach can be of interest in various scientific fields, overcoming the synthetic limits that have hitherto hindered the technological exploitation of polysaccharides-based materials
Luminescent gold nanoclusters as biocompatible probes for optical imaging and theranostics
No full textOptical bioimaging is a powerful tool for investigating living organisms in real time and space, both in-vivo and in-vitro. As an advantage, luminescence based techniques are poorly invasive and highly sensitive when compared to other diagnostic approaches. In order to exploit these attractive features, the search of highly biocompatible contrast agents with spectral controllable signatures and good photostability is needed. Gold nanoclusters (GNCs) based probes promise to merge all these characteristics, being their emission tunable from the visible (VIS) to the near infrared region (NIR), a spectral window ideal for photo-activation and detection in-vivo. In this review article, examples of the most recent applications of GNCs to in-vitro and in-vivo imaging are discussed, also considering the development and the use of multimodal and multifunctional probes, able to combine diagnostic and therapeutic (theranostic) actions. Brightness, photostability and toxicity of GNCs in biological systems are critically analyzed. For a complete overview, the origin of the optical properties of GNCs, as well as their preparation, is briefly discussed
Morphological changes of calcite single crystals induced by graphene–biomolecule adducts
No full textCalcite has the capability to interact with a wide variety of molecules. This usually induces changes in shape and morphology of crystals. Here, this process was investigated using sheets of graphene–biomolecule adducts. They were prepared and made dispersible in water through the exfoliation of graphite by tip sonication in the presence tryptophan or N-acetyl-D-glucosamine. The crystallization of calcium carbonate in the presence of these additives was obtained by the vapor diffusion method and only calcite formed. The analysis of the microscopic observations showed that the graphene–biomolecule adducts affected shape and morphology of rhombohedral 10.4 faced calcite crystals, due to their stabilization of additional hk.0 faces. The only presence of the biomolecule affected minimally shape and morphology of calcite crystals, highlighting the key role of the graphene sheets as 2D support for the adsorption of the biomolecules
Pseudopeptide-Based Hydrogels Trapping Methylene Blue and Eosin Y
No full textWe present herein the preparation of four different hydrogels based on the pseudopeptide gelator Fmoc-l-Phe-d-Oxd-OH (Fmoc=fluorenylmethyloxycarbonyl), either by changing the gelator concentration or adding graphene oxide (GO) to the water solution. The hydrogels have been analysed by rheological studies that demonstrated that pure hydrogels are slightly stronger compared to GO-loaded hydrogels. Then the hydrogels efficiency to trap the cationic methylene blue (MB) and anionic eosin Y (EY) dyes has been analyzed. MB is efficiently trapped by both the pure hydrogel and the GO-loaded hydrogel through π–π interactions and electrostatic interactions. In contrast, the removal of the anionic EY is achieved in less satisfactory yields, due to the unfavourable electrostatic interactions between the dye, the gelator and GO
Carbon-Based Hybrid Nanostructures for Advanced Functional Materials
Full text linkAll the carbon based nanomaterials (CNMs) are highly hydrophobic, which make them unsuitable for most of the applications in water and organic solvents. Aggregation phenomena significantly reduce the high performances displayed by the single nanostructure. Two main strategies allow to overcome this bottleneck: the chemical functionalization with hydrophilic functional groups or the non-covalent interaction between CNMs and amphiphilic molecules.
The aim of this thesis has been to produce different carbon-based hybrid nanostructures to preserve the peculiar properties of CNMs and use them for advanced application in nanomedical and technological fields.
In the first project, the potential application of fullerene (C60) as sensitizer for photodynamic therapy was explored. Monodispersity of fullerenes is the key feature for its potential application in this field. Noncovalent approach was used to disperse C60 in water, taking advantage from the
surfactant-like properties of the proteins. C60@lyszoyme hybrid was used as model system to study the stability of fullerene in physiological conditions and to assess its ability to produce reactive oxygen species upon irradiations.
The second subject of my research concerned the study of interactions between fluorescent nanodiamonds (FNDs) and plasma proteins. FNDs show potential applications as probe for bioimaging but their tendency to aggregate in physiological environments is the main limit for their application. In this study, a procedure to keep monodispersed FNDs in relevant biological fluids was optimized and the composition of FNDs protein corona was extensively characterized.
The third project was addressed to the manufacturing of graphene based calcite nanocomposite. Both covalent (graphene oxide) and non-covalent (graphene/biomolecules adducts) approaches were used to disperse graphene in water. Following a biological inspired synthetic procedure, it
was possible to incorporate the 2D materials within a 3D crystal lattice, producing a nanocomposite possessing several new properties
Delivery systems for agriculture: Fe-EDDHSA/CaCO3 hybrid crystals as adjuvants for prevention of iron chlorosis
No full textFe-EDDHSA/CaCO3 hybrid crystals are synthesized and tested
in vitro to determine their effect in treating iron chlorosis in kiwifruit
plants, used as a proof of concept. Under the alkaline conditions
provided by the calcareous substrate, plants release protons that
dissolve the hybrids and trigger Fe uptake. These CaCO3 hybrids
represent a new system for active molecule delivery in agriculture
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
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