Electrochemical triggering and control of atom transfer radical polymerization

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Synthesis and mechanical characterisation of cellulose based textiles grafted with acrylic monomers

Grafting polymerisation of methyl methacrylate and ethyl acrylate onto linen and cotton was carried out in order to reinforce these materials, when they underwent degradation. Take into account this aim, an artificially ageing was performed onto cellulose based textiles by metaperiodate oxidation, in order to obtain degraded model samples. Carbonyl groups were introduced in the cellulose and used as photosensitive agents, allowing the formation of radical sites during the polymerisation reaction, that started by irradiating the substrate by ultraviolet light.In this paper the effectiveness of grafting polymerisation as a method for textile conservation is discussed, starting from the results obtained from several characterisations, as the grafting yields and the grafting efficacy evaluation, the DSC analysis, the FTIR spectroscopy and the SEM observations. Moreover the consolidating and the protective effects were investigated by evaluating the mechanical properties and the wetting behaviour of the grafted samples, and comparing them with the original and aged substrates. The mechanical strength of cellulose based textiles has been improved, as well as the wetting behaviour has been enhanced.     

Absolute stereochemistry of dihydrofuroangelicins bearing C-8 substituted double bonds: a combined chemical/exciton chirality protocol

Coumarins are associated with a variety of pharmacological activities which have led to the synthesis of numerous derivatives. However, no general method for determination of the absolute configuration of chiral coumarins is known. This has now been achieved for a series of dihydrofuroangelicins bearing a variety of C-8 substituted double bonds, synthesized in the racemic form and resolved through enantioselective chromatography. A combined chemical/chiroptical protocol has been developed in which the C[double bond, length as m-dash]C double bonds are replaced with a styrenoid chromophore through either (i) cross metathesis, (ii) Heck reaction, or (iii) a combined method of cross metathesis and Heck reaction with about 1 mg sample under mild conditions. The coupling between the styrenoid and coumarin chromophores gives rise to clear-cut exciton coupled CD curves, suitable for assignments of absolute configurations. The solution conformation of the styrenoid derivatives is determined by NMR and DFT molecular modeling; the electronic structure of the 7-hydroxy coumarin chromophore is also clarified by semi-empirical and TDDFT methods. The conformation thus derived, in conjunction with quantitative DeVoe's coupled-oscillator CD calculation, establishes the absolute configurations of the coumarins. The theoretical study described herein justifies the straightforward approach of the current chemical/exciton chirality protocol to this type of dihydrofuroangelicins.     

Complexes of diethylenetriaminepentaacetic acid as contrast agents in NMR imaging. Computer simulation of equilibria in human blood plasma

In magnetic resonance imaging (MRI), the degree of contrast can be improved by using suitable contrast agents. The diethylenetriaminepentaacetic acid (DTPA) complexes of paramagnetic ions have been proposed for this purpose. This paper deals with extensive simulations of the distribution of species in blood plasma when solutions of manganese(II), copper(II), iron(III) and gadolinium(III) ions (as their soluble salts and as DTPA complexes) are injected. The various interaction equilibria, for which formation constants are known, are considered in order to assess toxic side-effects associated with their use in MRI. The data obtained support from the thermodynamic point of view, the use of GdDTPA, and suggest that the administration of a slight excess of ligand would guarantee complete coordination of the toxic gadolinium ion, and only minor interaction with the metal ions naturally present in blood plasma.     

In-water reactivity of nucleosides and nucleotides: one-step preparation and biological evaluation of novel ferrocenyl-derivatives

The reactivity in water of a series of nucleosides and nucleotides towards ferrocenemethanol was investigated. Several adducts incorporating the ferrocenemethyl moiety into the heterocyclic base were isolated and their activity was tested against HIV-1, HBV, YFV, BVDV and several bacteria. However, none of the new compounds showed significant antiviral activity nor cytotoxicity. The reaction with ferrocenemethanol of the model dinucleotide ^5′dCpdG^3′, for a direct comparison of the behaviour of purine versus pyrimidine bases, is also discussed.     

Analysis of heavy metals in atmospheric particulate by ion chromatography

Cu, Ni, Zn, Co, Fe+2, Mn, Cd, Fe+3 and Pb are easily separated and detected in isocratic mode by ion chromatography with post-column derivatization using a bifunctional ion-exchange column and an eluent formed by oxalic acid (28 mM) and sodium nitrate (250 mM). The separation is optimised by using a suggested sample solution containing a given concentration of chloride. Detection limits were 10-15 ppb for all the metals except for cadmium and lead, for which detection limits of 30 and 60 ppb were found, respectively. The method was tested on an atmospheric particulate certified sample. The measured values were in good agreement with certified values. Real samples of atmospheric particulate from industrial and urban sites were analysed and the results are discussed.     

Optimisation of the formulation of a bubble bath by a chemometric approach market segmentation and optimisation

The optimisation of the formulation of a commercial bubble bath was performed by chemometric analysis of Panel Tests results. A first Panel Test was performed to choose the best essence, among four proposed to the consumers; the best essence chosen was used in the revised commercial bubble bath. Afterwards, the effect of changing the amount of four components (the amount of primary surfactant, the essence, the hydratant and the colouring agent) of the bubble bath was studied by a fractional factorial design. The segmentation of the bubble bath market was performed by a second Panel Test, in which the consumers were requested to evaluate the samples coming from the experimental design. The results were then treated by Principal Component Analysis. The market had two segments: people preferring a product with a rich formulation and people preferring a poor product. The final target, i.e. the optimisation of the formulation for each segment, was obtained by the calculation of regression models relating the subjective evaluations given by the Panel and the compositions of the samples. The regression models allowed to identify the best formulations for the two segments ofthe market.     

Solution and biologically relevant conformations of enantiomeric 11-cis-locked cyclopropyl retinals

To gain information on the conformation of the 11-cis-retinylidene chromophore bound to bovine opsin, the enantiomeric pair (2a and 2b) of 11-cis-locked bicyclo[5.1.0]octyl retinal (retCPr) 2 was prepared and its conformation was investigated by NMR, geometry optimization, and CD calculations. This compound is also of interest since it contains a unique moiety in which a chiral cyclopropyl group is flanked by triene and enal chromophores, and hence would clarify the little-known chiroptical contribution of a cyclopropyl ring linked to polyene systems. NMR revealed that the seven-membered ring of retCPr adopts a twist chair conformation. The NMR-derived structure constraints were then used for optimizing the geometry of 2 with molecular mechanics and ab initio methods. This revealed that enantiomer 2a with a 11 beta,12 beta-cyclopropyl group exists as two populations of diastereomers depending on the twist around the 6-s bond; however, the sense of twist around the 12-s is positive in both rotamers. The theoretical Boltzmann-weighted CD obtained with the pi-SCF-CI-DV MO method and experimental spectra were consistent, thus suggesting that the conjugative effect of the cyclopropyl moiety is minimal. It was found that only the beta-cyclopropyl enantiomer 2a, but not the alpha-enantiomer 2b, binds to opsin. This observation, together with earlier retinal analogues incorporation results, led to the conclusion that the chromophore sinks into the N-terminal of the opsin receptor from the side of the 4-methylene and 15-aldehyde, and that the binding cleft accommodates 11-cis-retinal with a slightly positive twist around C12/C13. A reinterpretation of the previously published negative CD couplet of 11,12-dihydrorhodopsin also leads to a chromophoric C12/C13 twist conformation with the 13-Me in front as in 1b. Such a conformation for the chromophore accounts for both the observed biostereoselectivity of retCPr 2a and the observed negative couplet of 11,12-dihydro-Rh7.     

Thermodynamics and kinetics of PNA-DNA quadruplex-forming chimeras

PNA-DNA chimeras present the interesting properties of PNA, such as the high binding affinity to complementary single-strand (DNA or RNA), and the resistance to nuclease and protease degradation. At the same time, the limitations of an oligomer containing all PNA residues, such as low water solubility, self-aggregation, and low cellular uptake, are effectively overcome. Further, PNA-DNA chimeras possess interesting biological properties as antisense agents. We have explored the ability of PNA-DNA chimeric strands to assemble in quadruplex structures. The rate constant for association of the quadruplexes and their thermodynamic properties have been determined by CD spectroscopy and differential scanning calorimetry (DSC). Thermal denaturation experiments indicated higher thermal and thermodynamic stabilities for chimeric quadruplexes in comparison with the corresponding unmodified DNA quadruplex. Singular value decomposition analysis (SVD) suggests the presence of kinetically stable intermediate species in the quadruplex formation process. The experimental results have been discussed on the basis of molecular dynamic simulations. The ability of PNA-DNA chimeras to form stable quadruplex structures expands their potential utility as therapeutic agents.     

Simultaneous reversed-phase high-performance liquid chromatographic separation of mono-, di-and trichloroanilines through a gradient elution optimised by experimental design

A new RP-HPLC method for the simultaneous determination of the 13 mono-, di- and trichloroanilines has been developed. In order to obtain the analyte resolution within an acceptable analysis time, a gradient elution program has been optimised through the use of an experimental design and a grid search algorithm. The optimized conditions provided the resolution of all the analytes in less than 80 min. The primary validation of the analytical method gave limit of detection values ranging between 0.02 and 0.06 mg/l and very good linearity of the calibration curves.