Generation of Gevrey class semigroup by non‐selfadjoint Euler–Bernoulli beam model

Asymptotic and spectral properties of a non‐selfadjoint operator that is a dynamics generator for the Euler–Bernoulli beam model of a finite length are studied in this paper. The hyperbolic equation, which governs the vibrations of the Euler–Bernoulli beam model, is supplied with a one‐parameter family of physically meaningful boundary conditions containing damping terms. The initial boundary‐value problem is equivalent to the evolution equation that generates a strongly continuous semigroup in the state space of the system. It is found that the semigroup, being non‐analytic, belongs to Gevrey class semigroups. This means that the differentiability of such semigroup is slightly weaker than that of an analytic semigroup. In the forthcoming works, the results of the present paper will be applied (a) to the solution of the exact controllability problem for Euler–Bernoulli beam and (b) to spectral analysis of a planar network of serially connected Euler–Bernoulli beams modelling ‘flying wing configurations’ in aeronautic engineering. Copyright © 2006 John Wiley & Sons, Ltd.     

Fractional logarithmic Schrödinger equations

By means of nonsmooth critical point theory, we obtain existence of infinitely many weak solutions of the fractional Schrödinger equation with logarithmic nonlinearity. We also investigate the Hölder regularity of the weak solutions. Copyright © 2015 JohnWiley & Sons, Ltd     

A Nanocomposite Containing Carbon Nano-onions and Polyaniline Nanotubes as a Novel Electrode Material for Electrochemical Sensing of Daidzein

Glassy carbon electrode (GCE) were modified with nanocomposites containing conductive polyaniline nanotubes (PANI_nt) and carbon nano-onions (CNOs). Herein we report a simple and sensitive way for daidzein (DA) determination at concentrations between 1 and 10 μM by linear sweep voltammetry using GCE/PANI_nt/CNOs system. The DA electrochemical behavior was examined in two buffer environments (pH 7.5 and 4.5) using electrodes modified with the oxidized CNOs or their derivatives containing carboxyl and benzylamino functional groups. The direct electrooxidation of DA was observed at +0.65 V and +0.8 V at pH 7.5 and at +0.7 V and +1.1 V vs. Ag/AgCl at pH 4.5.     

Giant Shape-Persistent Tetrahedral Porphyrin System: Light-Induced Charge Separation

Tetraphenylmethane appended with four pyridylpyridinium units works as a scaffold to self-assemble four ruthenium porphyrins in a tetrahedral shape-persistent giant architecture. The resulting supramolecular structure has been characterised in the solid state by X-ray single crystal analysis and in solution by various techniques. Multinuclear NMR spectroscopy confirms the 1 : 4 stoichiometry with the formation of a highly symmetric structure. The self-assembly process can be monitored by changes of the redox potentials, as well as by modifications in the visible absorption spectrum of the ruthenium porphyrin and by a complete quenching of both the bright fluorescence of the tetracationic scaffold and the weak phosphorescence of the ruthenium porphyrin. An ultrafast photoinduced electron transfer is responsible for this quenching process. The lifetime of the resulting charge separated state (800 ps) is about four times longer in the giant supramolecular structure compared to the model 1 : 1 complex formed by the ruthenium porphyrin and a single pyridylpyridinium unit. Electron delocalization over the tetrameric pyridinium structure is likely to be responsible for this effect.     

Visible‐Light‐Induced Direct Photocatalytic Carboxylation of Indoles with CBr4/MeOH

Photocatalysis enables the cascade reactions of indoles and CBr₄ in MeOH through a C(sp²)?H functionalization/methanolysis sequence. The title reaction provides an efficient access to indole 2‐ and 3‐carboxylates in a single operation (no preinstallation of protecting as well as directing groups was required) with good yields under mild reaction conditions.     

5,6-dihydroxyindole tetramers with "anomalous" interunit bonding patterns by oxidative coupling of 5,5',6,6'-tetrahydroxy-2,7'-biindolyl: emerging complexities on the way toward an improved model of eumelanin buildup

Chemical or enzymatic oxidation of 5,6-dihydroxyindole (1) leads to the rapid deposition of a black solid resembling eumelanin pigments by way of a complex oligomerization/polymerization process that proceeds in the early stages via dimers 2-3 and trimers 5-6 characterized by 2,4'- and 2,7'-couplings. Despite extensive efforts, the structures of the higher oligomers, which define the structural architecture and physicochemical properties of the eumelanin particles, have so far defied elucidation. Using a dimer-dimer coupling strategy that has recently allowed the first successful entry to a tetramer of 1, we report now three additional tetramers obtained by oxidation of 5,5',6,6'-tetrahydroxy-2,7'-biindolyl (3) with the peroxidase/H2O2 system. On the basis of extensive 2D NMR and mass spectrometric analysis, the products were identified as 5,5',5',5',6,6',6',6'-octaacetoxy-7,2':3',3':2',7'-tetraindolyl (acetylated 8, 3%), 5,5',5',5',6,6',6',6' '-octaacetoxy-2,7':4',4':7',2'-tetraindolyl (acetylated 9, 4%), and 5,5',5',5',6,6',6',6'-octaacetoxy-2,7':2',3':2',7'-tetraindolyl (acetylated 10, 5%), in which the inner units are linked through unexpected 3,3'-, 4,4'-, and 2,3'-linkages. If verified in further studies, the newly uncovered coupling patterns would entail important consequences for current models of eumelanin structure based on one-dimensional structural chains with extended pi-electron conjugation or pi-stacked flat oligomer aggregates.     

Structural Basis of Artemisinin Binding Sites in Serum Albumin with the Combined Use of NMR and Docking Calculations

Artemisinin is known to bind to the main plasma protein carrier serum albumin (SA); however, there are no atomic level structural data regarding its binding mode with serum albumin. Herein, we employed a combined strategy of saturation transfer difference (STD), transfer nuclear Overhauser effect spectroscopy (TR-NOESY), STD–total correlation spectroscopy (STD-TOCSY), and Interligand Noes for PHArmacophore Mapping (INPHARMA) NMR methods and molecular docking calculations to investigate the structural basis of the interaction of artemisinin with human and bovine serum albumin (HSA/BSA). A significant number of inter-ligand NOEs between artemisinin and the drugs warfarin and ibuprofen as well as docking calculations were interpreted in terms of competitive binding modes of artemisinin in the warfarin (FA7) and ibuprofen (FA4) binding sites. STD NMR experiments demonstrate that artemisinin is the main analyte for the interaction of the A. annua extract with BSA. The combined strategy of NMR and docking calculations of the present work could be of general interest in the identification of the molecular basis of the interactions of natural products with their receptors even within a complex crude extract.     

Reagent-controlled stereoselectivity in titanocene-catalyzed epoxide openings: reductions and intermolecular additions to alpha,beta-unsaturated carbonyl compounds

The generation and addition reactions of metal bound radicals derived from normal and meso epoxides by electron transfer from titanocene(III) reagents is described. The control of enantioselectivity and diastereoselectivity of these transformations is investigated by variation of the ligands of the metal complex. The reaction can lead to unprecedented and highly selective reactions, in which synthetically useful alcohols may be prepared. The synthesis presented also circumvents the use of toxic metals. Another advantage is that there is no loss of two functional groups as usually observed in reductive radical chain reactions.     

A New Photoactivatable Ruthenium(II) Complex with an Asymmetric Bis-Thiocarbohydrazone: Chemical and Biological Investigations

The synthesis, photoactivation and biological activity of a new piano-stool Ru(II) complex is herein reported. The peculiarity of this complex is that its monodentate ligand which undergoes the photodissociation is an asymmetric bis-thiocarbohydrazone ligand that possesses a pyridine moiety binding to Ru(II) and the other moiety contains a quinoline that endows the ligand with the capacity of chelating other metal ions. In this way, upon dissociation, the ligand can be released in the form of a metal complex. In this article, the double ability of this new Ru(II) complex to photorelease the ligand and to chelate copper and nickel is explored and confirmed. The biological activity of this compound is studied in cell line A549 revealing that, after irradiation, proliferation inhibition is reached at very low half maximal inhibitory concentration (IC₅₀) values. Further, biological assays reveal that the dinuclear complex containing Ni is internalized in cells.     

Prediction of calcite morphology from computational and experimental studies of mutations of a de novo-designed peptide

Many organisms use macromolecules, often proteins or peptides, to control the growth of inorganic crystals into complex materials. The ability to model peptide-mineral interactions accurately could allow for the design of novel peptides to produce materials with desired properties. Here, we tested a computational algorithm developed to predict the structure of peptides on mineral surfaces. Using this algorithm, we analyzed energetic and structural differences between a 16-residue peptide (bap4) designed to interact with a calcite growth plane and single- and double-point mutations of the charged residues. Currently, no experimental method is available to resolve the structures of proteins on solid surfaces, which precludes benchmarking for computational models. Therefore, to test the models, we chemically synthesized each peptide and analyzed its effects on calcite crystal growth. Whereas bap4 affected the crystal growth by producing heavily stepped corners and edges, point mutants had variable influences on morphology. Calculated residue-specific binding energies correlated with experimental observations; point mutations of residues predicted to be crucial to surface interactions produced morphologies most similar to unmodified calcite. These results suggest that peptide conformation plays a role in mineral interactions and that the computational model supplies valid energetic and structural data that can provide information about expected crystal morphology.