Experimental and in silico characterization of a biologically active inosose

Inositols have been recently reported to show a biological activity as inhibitors of both glycosidase and amyloid-β protein. After having harvested good crystals suitable for single crystal X-ray diffraction, we performed a comparison with the data inferred by means of a molecular dynamics simulation, based on the use of an appropriate Force Field coupled to the most performing charging scheme. This approach allowed a detailed analysis extended to ultra-fine details, such as atomic displacement parameters. It confirmed the good validity of a robust approach already tested by us in previous studies. A NMR analysis of the molecule in solution was also carried out, to compare the structural findings suggested by the X-ray analysis with the ones in solution and avoid confining them to the solid-state. In this framework, we investigated the above-mentioned inhibiting activity of a class of inososes, by means of a molecular docking investigation, which proved the suggested validity of the studied compound as inhibitor of the α-glucosidase.     

Molecular weight distribution in emulsion polymerization. II. The copolymer case

A model for evaluating instantaneous degree of polymerization distribution and the chain composition distribution of copolymers produced in emulsion is developed. The approach adopted is based on the mathematics of Markov processes and represents an extension of the one developed for homopolymers in Part I. As in the homopolymer case, the main aspect of the theoretical treatment is the definition of the proper one step transition probability matrix through the so called subprocess-main process procedure. The model accounts for monomolecular and bimolecular termination (both by combination and disproportionation) and, in principle, it can be applied to any number of reacting monomer species as well as to any number of active chains per particle. However, only the 0–1–2 and 0–1–2–3 emulsion copolymerization systems are discussed in detail. In the case of the chain composition distribution, the model allows the calculation of its moments only, through the method of the Generating Function associated with the probability density function. The expression obtained for the instantaneous probability density functions, as well as for the corresponding cumulative distributions, are all in explicit form and involve only algebraic operations among matrices. Efficient numerical procedure for their application are reported in the Appendix. Illustrative calculations are reported for a 0–1–2–3 copolymerization system, simulating the copolymer styrene–methylmethacrylate. The effect of the various termination mechanisms on the distribution of degrees of polymerization and on the first two moments of the chain composition distribution is discussed in detail. Finally, the three dimensional overall distribution function of both chain length and composition is shown under the assumption of Gaussian type chain composition distribution.     

Effect of alkyl group on the structure of heterodinuclear Zn(II)–Cu(II) and Zn(II)–Ni(II) complexes derived from unsymmetrical phenol-based dicompartmental macro-acyclic ligands

A series of mono- and heterodinuclear macro-acyclic complexes of [ZnLCu(II)]²⁺ and [ZnLNi(II)]²⁺ were synthesized by a stepwise procedure. The phenol-based macro-acyclic dicompartmental ligands (L^2?) possess contagious hexadentate (N₄O₂) and tetradentate (N₂O₂) coordination sites, where in the mononuclear complexes [ZnL(H⁺)₂]²⁺ the latter site containing two alkyl-imine donor groups (ethyl or isopropyl) is attached to the azomethine moieties. The alkyl group(s) is eliminated upon introduction of the second metal (II) ion into N₂O₂ coordination site as a result of steric crowding of the alkyl groups along with the lack of flexibility associated with the imine groups. When the second metal ion is Cu(II) and R = isopropyl, the both of them are eliminated but when R = Et only one ethyl group is removed. However, in case of Ni(II) as the second metal ion, the both alkyl groups are eliminated regardless of the nature of the alkyl group. The origins of the structural variations are discussed. The prepared complexes were characterized by elemental analysis, molar conductance measurements, X-ray crystallography, IR, NMR and UV–Vis spectroscopies.     

Multimerization of an Apoptogenic TRAIL‐Mimicking Peptide by Using Adamantane‐Based Dendrons

We have developed a straightforward strategy to multimerize an apoptogenic peptide that mimics the natural tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) by using adamantane‐based dendrons as multivalent scaffolds. The selective binding affinity of the ligands to TRAIL receptor 2 (TR2) was studied by surface plasmon resonance, thus demonstrating that the trimeric and hexameric forms of the peptide exert an increased affinity of about 1500‐ and 20 000‐fold, respectively, relative to the monomer. Moreover, only the trimeric and hexameric ligands were able to induce cell death in TR2 expressing cells (BJAB), thus confirming that a multivalent form of the peptide is necessary to trigger a substantial TR2‐dependent apoptotic response in vitro. These results provide interesting insight into the multivalency effect on biological ligand/receptor interactions for future therapeutic applications.     

Carbon Paste Electrode Bulk-Modified with the Conducting Polymer Poly(1,8-Diaminonaphthalene): Application to Lead Determination

Carbon paste electrodes modified with conducting polymers for sensitive and selective determination of lead are presented. A novel method for generating a reproducible polymer-coated electrode surface is developed. We prove that 1,8-diaminonaphthalene (1,8-DAN) mixed with a carbon paste electrode leads to a conducting polymer in acidic medium while, in the same medium, this polymer is known to be non-conducting on platinum electrode. The electrode behaviour of poly(1,8-DAN), electropolymerised into carbon paste, was investigated by cyclic voltammetry in the presence of the ferri-ferrocyanide couple.A carbon paste electrode modified with poly(1,8-DAN) was used to determine Pb²⁺ in aqueous solutions. Pb²⁺ ions were firstly complexed and then electrochemically deposited by a potential step to –0.9V. The accumulated lead after reduction was anodically stripped by differential pulse voltammetry. Different parameters, such as pH of the solution, preconcentration time, and electropolymerisation procedures were studied.For a preconcentration time of ten minutes, the calibration graph was linear from 40 to 2070ngmL^–1 with r²=0.998. The detection limit was found to be 30ngmL^–1, and the relative standard deviation was 6%.     

Barbituric and thiobarbituric acids: a conformational and spectroscopic study

A conformational study on Barbituric (BA) and Thiobarbituric (TBA) acids was performed at ab initio MP2/6-31G** level on the neutral, protonated, mono- and di-anionic forms. Acid-base equilibria were studied by comparing the electronic transitions evaluated for the most stable conformations and the experimental spectra at different pH values. The electronic transitions were obtained through the ZINDO approach.     

A synthesis of new 7-amino-substituted 4-aminopyrazolo[1,5-a][1,3,5]triazines via a selective three-component triazine ring annulation

3-Amino-substituted 5-aminopyrazoles were found to be suitable substrates for the synthesis of new 4-aminopyrazolo[1,5-a][1,3,5]triazines (5-aza-9-deaza-adenines) when used in the one-pot, three-component reaction with cyanamide and triethyl orthoformate under microwave irradiation. The reaction proceeded selectively and its scope was demonstrated by the preparation of a library of 4-aminopyrazolo[1,5-a][1,3,5]triazines. Some structural aspects of the prepared compounds were investigated using dynamic NMR spectroscopy and X-ray crystallography. The operational simplicity, short reaction time, and good reproducibility are attractive features of the developed robust and practical approach for the synthesis of 7-amino-substituted 4-aminopyrazolo[1,5-a][1,3,5]triazines.     

Identification of changes in <Emphasis Type="Italic">Triticum durum</Emphasis> L. leaf proteome in response to salt stress by two-dimensional electrophoresis and MALDI-TOF mass spectrometry

In order to understand the molecular basis of salt stress response, a proteomic approach, employing two-dimensional electrophoresis and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS), was used to identify proteins affected by salinity in wheat (Triticum durum ‘Ofanto’). Identification of proteins, whose levels were altered, was performed by comparing protein patterns of salt-treated and control plants. A set of control plants was grown without NaCl addition under the same conditions as the salt-treated plants. Proteins were extracted from the leaves of untreated and NaCl-treated plants, and resolved using 24-cm immobilized pH gradient strips with a pH 4–7 linear gradient in the first dimension and a 12.5% sodium dodecyl sulphate polyacrylamide gel electrophoresis in the second dimension; the gels were stained with Coomassie and image analysis was performed. Quantitative evaluation, statistical analyses and MALDI-TOF MS characterization of the resolved spots in treated and untreated samples enabled us to identify 38 proteins whose levels were altered in response to salt stress. In particular, ten proteins were downregulated and 28 were upregulated. A possible role of these proteins in response to salinity is discussed.     

Angular‐Resolved Magnetometry Beyond Triclinic Crystals Part II: Torque Magnetometry of Cp*ErCOT Single‐Molecule Magnets

The experimental investigation of the molecular magnetic anisotropy in crystals in which the magnetic centers are symmetry related, but do not have a parallel orientation has been approached by using torque magnetometry. A single crystal of the orthorhombic organometallic Cp*ErCOT [Cp*=pentamethylcyclopentadiene anion (C₅Me₅^?); COT=cyclooctatetraenedianion (C₈H₈^2?)] single‐molecule magnet, characterized by the presence of two nonparallel families of molecules in the crystal, has been investigated above its blocking temperature. The results confirm an Ising‐type anisotropy with the easy direction pointing along the pseudosymmetry axis of the complex, as previously suggested by out‐of‐equilibrium angular‐resolved magnetometry. The use of torque magnetometry, not requiring the presence of magnetic hysteresis, proves to be even more powerful for these purposes than standard single‐crystal magnetometry. Furthermore, exploiting the sensitivity and versatility of this technique, magnetic anisotropy has been investigated up to 150 K, providing additional information on the crystal‐field splitting of the ground J multiplet of the Er^III ion.     

Functionalization and Dissolution of Single-Walled Carbon Nanotubes by Chemical-Physical and Electrochemical Treatments

Single-Walled Carbon Nanotubes (SWCNTs) possess a wealth of exceptional structural, mechanical and electronic properties. These have made them potentially useful for applications in nanotube-reinforced materials, nanoelectronic devices, field emitters, probe tips for SPM, as well as for sensors, biosensors, and actuators. However, manipulation and processing of SWCNTs has been limited by their insolubility in most common solvents, although some dissolution has recently been obtained. Their chemical modification might pave the way to many useful applications, including the preparation of composite materials or the immobilization of biological molecules as enzymes (i.e., for biosensors and electrochemical sensors). Attachment of oxygen-containing functional groups (i.e., carboxy groups, carbonyl groups, hydroxy groups, etc.) on the surface of the carbon nanotubes could be achieved using different pretreatments of the nanostructured material. These involved (a) chemical and physical procedures; and (b) electrochemical functionalization. Different attempts at sidewall modification have been hampered by the presence of significant contaminants as graphitic and amorphous carbon or have required solubilization via chemical reactions on the ends of cut nanotubes. A more accommodating and direct approach to functionalize nanotubes is therefore required. We report here the sidewall functionalization of purified SWCNTs, obtained by different approaches and finally, we can discuss possible applications of functionalized SWCNTs in the sensing area.