ChemInform Abstract: Covalent Capture: Merging Covalent and Noncovalent Synthesis (original) (raw)
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Oxidative stress Parkinson's disease a b s t r a c t a-Synuclein (asyn) fibril formation is considered a central event in the pathogenesis of Parkinson's disease (PD). In recent years, it has been proposed that prefibrillar annular oligomeric b-sheet-rich species, called protofibrils, rather than fibrils themselves, may be the neurotoxic species. The oxidation products of dopamine (DAQ) can inhibit asyn fibril formation supporting the idea that DAQ might stabilize asyn protofibrils.
Surface Functionalization of Fluorine-Doped Tin Oxide Samples through Electrochemical Grafting
ACS Applied Materials & Interfaces, 2013
Transparent conductive oxides are emerging materials in several fields, such as photovoltaics, photoelectrochemistry, and optical biosensing. Their high chemical inertia, which ensured long-term stability on one side, makes challenging the surface modification of transparent conductive oxides; long-term robust modification, high yields, and selective surface modifications are essential prerequisite for any further developments. In this work, we aim at inducing chemical functionality on fluorine-doped tin oxide surfaces (one of the most inexpensive transparent conductive oxide) by means of electrochemical grafting of aryl diazonium cations. The grafted layers are fully characterized by photoemission spectroscopy, cyclic voltammetry, and atomic force microscopy showing linear correlation between surface coverage and degree of modification. The electrochemical barrier effect of modified surfaces was studied at different pH to characterize the chemical nature of the coating. We showed immuno recognition of biotin complex built onto grafted fluorine-doped tin oxides, which opens the perspective of integrating FTO samples with biological-based devices.
European Journal of Organic Chemistry, 2012
Functionalization of the bis-lacunary Keggin polyoxotungstate [γ-SiW 10 O 36 ] 8has been achieved with a two-step synthesis, by the covalent attachment of a 3-aminopropylsilane spacer and further linkage of the dansyl (5-dimethylamino-1-naphthalenesulfonyl-) residue. The resulting bis-decorated molecular hybrid [{{(CH 3 ) 2 N}C 10 H 6 SO 2 NH(CH 2 ) 3 Si} 2 O(γ-SiW 10 O 36 )] 4has been isolated and characterized in solution and in the solid state by FTIR, multinuclear NMR, ESI-MS, UV/Vis, luminescence spectroscopy, dynamic light scattering (DLS), and Scanning Electron Microscopy (SEM). The inorganic polyoxometalate provides a molecular nano-surface where the dansyl fluorophores are anchored with a tweezertype arrangement. The merging of the organic and inorganic domains of the bis-dansylated complex dictates its fluorescence features, which are observed in the range 375-600 nm,
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ChemSusChem, 2011
The production of carbon-neutral energy is an important emergence of this century, due to the projected shortage of fossil fuels, the increase in the petrol barrel price, and the environmental burden that massive exploitation of natural resources is imposing to present and future generations. [1, 2] Molecular hydrogen has the potential to quench the world's energy thirst and could in principle be produced by the splitting of water molecules. In practice, water splitting is hindered by the remarkable chemical stability of water itself, as the Gibbs free energy, DG, required for its splitting is at least 2.46 eV per molecule. Nevertheless, water activation occurs continuously at the heart of the photosynthetic II enzyme (PSII), which is the renewable feedstock employed by nature to power our daily lives and produce oxygen and carbohydrates as biological fuels. Following bio-inspired guidelines, the big challenge is to devise a functional mimicry, enabling an economically viable, artificial transposition of the process to produce hydrogen as a sustainable energy vector. Success in this task is, in the first instance, based on the development of multi-electron redox catalysts, which can perform water splitting at low overpotentials with high turnover efficiency (TON) and frequency (TOF). [1][2] Whereas several catalyst packages based on functionalized carbon nanotubes (CNTs) have been successfully implemented for the half-cell reduction of H + to hydrogen, [4] analogous systems for oxygen evolution are still very rare. Indeed, the oxidative half-reaction, (2 H 2 O!O 2 +4 H + +4 e À ), is a four-electron/ four-proton process, which dictates a large molecular rearrangement, as four OÀH bonds are cleaved to release a new OÀO bond. Therefore, water oxidation poses a severe chemical hurdle, involving both kinetic and thermodynamic challenges. A recent publication described completely inorganic molecular metal-oxides, which displayed a unique mimicry of PSII enzymes. [6] These complexes belong to the class of polyoxometalates (POM) with extended polyanionic charges, feature a tetrasubstituted core enabling oxygen evolution from water under dark or illuminated conditions, [7] and behave as multi-redox electrocatalysts. In particular, we have recently addressed the fabrication of innovative nano-materials for electrocatalytic water splitting, by tailoring the combination of polycationic CNTs by using the oxygen-evolving tetra-ruthenium(IV)-substituted POM with the formula {Ru IV 4 (m-OH) 2 (m-O) 4 (H 2 O) 4 [g-SiW 10 O 36 ]} 10À , in short, Ru 4 (POM). [6, 8] Functionalized, multiwalled carbon nanotubes (MWCNTs) carrying positively charged dendrimeric chains have been successfully used as nano-scaffolds to: 1) template the heterogeneous support of Ru 4 (POM), 2) control the morphology and surface area of the resulting nano-hybrid material, and 3) funnel the direction of sequential electron-transfer to the electrode. At pH 7.0, composite indium tin oxide (ITO) anodes, which incorporate the nanotube-POM material, effect the electrocatalytic splitting of water, with remarkable TOF of up to 306 h À1 at relatively low overpotentials of h = 0.35-0.60 V. This sets a record value compared to previously reported figures for Co-or Mn-based systems, with TOFs found in the range 0.7-20 h À1 at h ! 0.40 V. Moreover, the hybrid nanomaterial showed extreme robustness, excellent structural stability, and retention of electrocatalytic properties upon multi-cycle activity.
The continuous-flow cycloaddition of azomethine ylides to carbon nanotubes
Chemical Communications, 2011
The covalent chemistry of carbon nanostructures has put forth a wide variety of interesting derivatives that widen their potential as functional materials. However, the synthetic procedures that have been developed to functionalize the nanostructures may require long reaction times and harsh conditions. In this paper, we study the continuous flow processing of single-wall carbon nanotubes with azomethine ylides and diazonium salts and demonstrate that this approach is effective to reduce reaction times and tune the properties of the functionalized carbon materials.
Covalent Graft of Lipopeptides and Peptide Dendrimers to Cellulose Fibers
Introduction: Bacterial proliferation in health environments may lead to the development of specific pathologies, but can be highly dangerous under particular conditions, such as during chemotherapy. To limit the spread of infections, it is helpful to use gauzes and clothing containing antibacterial agents. As cotton tissues are widespread in health care environments, in this contribution we report the preparation of cellulose fibers characterized by the covalent attachment of lipopeptides as possible antimicrobial agents. Aim: To covalently link peptides to cotton samples and characterize them. Peptides are expected to preserve the features of the fabrics even after repeated washing and use. Peptides are well tolerated by the human body and do not induce resistance in bacteria. Materials and Methods: A commercially available cotton tissue (specific weight of 150 g/m 2 , 30 Tex yarn fineness, fabric density of 270/230 threads/10 cm in the warp and weft) was washed with alkali and bleached and died. A piece of this tissue was accurately weighed, washed with methanol (MeOH) and N,N-dimethylformamide (DMF), and air-dried. Upon incubation with epibromohydrin, followed by treatment with Fmoc-NH-CH 2 CH 2 -NH 2 and Fmoc removal, the peptides were synthesized by incorporating one amino acid at a time, beginning with the formation of an amide bond with the free NH 2 of 1,2-diaminoethane. We also linked to the fibers a few peptide dendrimers, because the mechanism of action of these peptides often requires the formation of clusters. We prepared and characterized seven peptide-cotton samples. Results: The new peptide-cotton conjugates were characterized by means of FT-IR spectroscopy and X-ray Photoelectron Spectroscopy (XPS). This latter technique allows for discriminating among different amino acids and thus different peptide-cotton samples. Some samples maintain a pretty good whiteness degree even after peptide functionalization. Interestingly, these samples also display encouraging activities against a Gram positive strain. Conclusions: Potentially antimicrobial lipopeptides can be covalently linked to cotton fabrics, step-by-step. It is also possible to build on the cotton Lys-based dendrimers. XPS is a useful technique to discriminate among different types of nitrogen. Two samples displaying some antibacterial potency did also preserve their whiteness index.
ACS Nano, 2010
A novel two-step bottom-up approach to construct a 2D long-range ordered, covalently bonded fullerene/porphyrin binary nanostructure is presented: in the first place, reversible supramolecular interactions between C 60 and 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin are exploited to obtain large domains of an ordered binary network, subsequently a reaction between fullerene molecules and the amino-groups residing on porphyrin units, triggered by thermal treatment, is used to freeze the supramolecular nanostructure with covalent bonds. The resulting nanostructure resists high temperature treatments as expected for an extended covalent network, whereas very similar fullerene/porphyrin nanostructures held together only by weak interactions are disrupted upon annealing at the same or at lower temperatures.