Electroactive C(2) symmetry receptors based on the biphenyl scaffold and tetrathiafulvalene units

The synthesis of a family of biphenyl-tetrathiafulvalene (TTF) derivatives incorporating a binding site has been carried out in good to moderate yields through functionalization of the biphenyl scaffold. X-ray structure of one derivative (compound 3) of the series is provided and shows a dihedral angle of 74 degrees around the central Ar-Ar bond of the biphenyl unit in a cisoid conformation. (1)H NMR and cyclic-voltammetry studies demonstrate the critical importance of the nature of the substitution on the conformational rigidity and on the electrochemical behavior of the resulting biphenyl-TTF assemblies. This feature is underlined by an original electrochemical recognition process upon binding of Pb(2+), correlated to conformational changes occurring upon metal cation complexation.     

Counteranion dependent protonation and aggregation of tetrakis(4-sulfonatophenyl)porphyrin in organic solvents

The tetrabutylammonium salt of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) is soluble in dichloromethane, and the general properties of this compound have been investigated as function of various added acids HX (X = Cl, Br, I, CF(3)COO, CF(3)SO(3), TFPB) through UV-vis absorption spectroscopy, steady state fluorescence emission, and resonance light-scattering (RLS) techniques. Upon addition of HX, the initial monomeric free base TPPS is readily converted in an aggregated species, whose spectroscopic features are independent of the nature of the counteranion X. All the spectroscopic evidence suggest a J-type arrangement of chromophores in this aggregate, involving strong hydrogen bonds, electrostatic, and dispersive interactions. In the specific case of chloride and bromide, in the presence of a TBAX excess, the addition of the corresponding acid leads to a monomeric ion-pair between the TBA cations and the diacid TPPS, whose central core is strongly interacting with the halide. On further increasing the acid concentration in these latter solutions, fully protonated species are formed that eventually start to aggregate.     

Some Nonlinear Elliptic Problems in Unbounded Domains

In this paper the results of some investigations concerning nonlinear elliptic problems in unbounded domains are summarized and the main difficulties and ideas related to these researches are described. The model problem

Surface behavior and molecular recognition in DNA microarrays from N,N-dimethylacrylamide terpolymers with activated esters as linking groups

A series of terpolymers made of DMA, NAS and MAPS were synthesized by free radical copolymerization and used as functional coatings for the fabrication of glass slide DNA microarrays. The surface properties of coated glass slides were investigated through contact angle measurements, ellipsometry and atomic force microscopy. The terpolymer molecular weight showed a moderate effect on surface tension (gamma(s) = 56-62 mN x m(-1)), but no clear effect on polymeric layer thickness (5-8 nm) and roughness. Hybridization experiments with amine-functionalized oligonucleotides gave the best fluorescence intensity results for microarrays coated with intermediate-molecular-weight terpolymers. Finally, an accelerated ageing test of the microarray in a humidity chamber showed a nice relationship between decay curves of contact angle against water and fluorescence intensity.     

Stress regularity in quasi-static perfect plasticity with a pressure dependent yield criterion

This work is devoted to establishing a regularity result for the stress tensor in quasi-static planar isotropic linearly elastic – perfectly plastic materials obeying a Drucker–Prager or Mohr–Coulomb yield criterion. Under suitable assumptions on the data, it is proved that the stress tensor has a spatial gradient that is locally squared integrable. As a corollary, the usual measure theoretical flow rule is expressed in a strong form using the quasi-continuous representative of the stress.     

Universal Deformation Rings for the Symmetric Group <Emphasis Type="Italic">S</Emphasis><Subscript>4</Subscript>

Let k be an algebraically closed field of characteristic 2, and let W be the ring of infinite Witt vectors over k. Let S ₄ denote the symmetric group on 4 letters. We determine the universal deformation ring R(S ₄,V) for every kS ₄-module V which has stable endomorphism ring k and show that R(S ₄,V) is isomorphic to either k, or W[t]/(t ²,2t), or the group ring W[ℤ/2]. This gives a positive answer in this case to a question raised by the first author and Chinburg whether the universal deformation ring of a representation of a finite group with stable endomorphism ring k is always isomorphic to a subquotient ring of the group ring over W of a defect group of the modular block associated to the representation.     

Compositional Changes in Sugarcane Bagasse on Low Temperature, Long-term Diluted Ammonia Treatment

Sugarcane bagasse is the major by-product of the sugar industry. It has a great potential for the production of biofuels and chemicals due to its considerable amount of cellulose and hemicellulose. In this study, we investigated a simple and economic pretreatment process using dilute ammonia for the storage of sugarcane bagasse. Sugarcane bagasse was stored in 0, 0.03, and 0.3% (w/w) ammonium hydroxide in a closed bottle for 40 days at 30 °C under atmospheric pressure without any agitation or circulation. Samples were taken every 10 days and analyzed for changes on lignin, cellulose, hemicellulose composition, ammonia concentration, and microbial counts. Biomass storage for 40 days at 0.3% ammonium hydroxide removed 46% of lignin and retained 100% cellulose and 73% hemicellulose.     

High performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry for sensitive determination of bioactive amines in donkey milk

In the present study we report on the optimization and validation of a sensitive high performance liquid chromatography atmospheric pressure chemical ionization mass spectrometry (HPLC–APCI–MS) method for the determination of 8 bioactive amines (histamine, tyramine, tryptamine, 2-phenylethylamine, cadaverine, putrescine, spermidine and spermine) in donkey milk samples. The method involves donkey milk pre-treatment to remove proteins and pre-column dansylation of the amines. HPLC in reversed phase mode has been used for bioactive amines separation and the operating condition of the APCI–MS system proved to be powerful and very efficient for peak assignment. The separation was accomplished in a short time with an excellent resolution for all the amine peaks. Quantification was carried out by monitoring the characteristic [M+H]⁺ ion of each amine derivative. The method sensitivity, linearity and repeatability were assayed with satisfactory results. The detection limits of the analysed amines ranged from 0.5 μg L⁻¹ to 15 μg L⁻¹; the highest LOD was for spermine. Also remarkably good recovery values were obtained; at the lowest spiking level (1 μg L⁻¹) the percent mean recoveries ranged from 77.7 to 109.7. Furthermore, as the investigations relate to a complex matrix as donkey milk, suitable studies on matrix effect were performed. Finally, the developed and validated method was applied to analyse 13 donkey milk samples. Among the identified bioactive amines, putrescine, spermine and spermidine proved to be the main amines in donkey milk. Their concentration levels in the present study were lower than the values determined in mature human, cow and sow milk.     

Active-sodium-promoted reductive cleavage of halogenated benzoic acids

The outcome of the reaction between 1,2-diaryl-1,2-disodioethanes and halogenated benzoic acids strongly depends on the nature of both reaction partners. Indeed, whilst chloro-, bromo- and iodobenzoic acids are easily dehalogenated, the reductive cleavage of fluorobenzoic acids proceeds to a high extent only in the presence of the dianions endowed with more powerful reducing properties. Moreover, it was observed that ortho-substituted benzoic acids are more easily dehalogenated than the corresponding para or meta isomers. These observations allowed the development of reaction conditions for the exhaustive or regioselective cleavage of selected polyhalogenated benzoic acids.     

Study of conformational properties of a biologically active peptide of fibronectin by circular dichroism, NMR and molecular dynamics simulation

Circular dichroism (CD), and NMR spectra have been recorded and molecular dynamics (MD) simulations have been performed in water and water-trifluoroethanol (TFE) mixed solvent for a synthetic biologically active 13-amino-acid fragment of human fibronectin and two related peptides. The CD results are interpreted on the basis of statistical analyses of MD trajectories and of ensuing calculations of CD spectra based on Schellman's matrix method. It is observed that the peptide conformation is quite variable in water and loses its mobility with the addition of TFE. (1)H-NOE data were found to be consistent with the most abundant calculated conformation.