Survey on the phase transitions and their effect on the ion-exchange and on the proton-conduction properties of a flexible and robust Zr phosphonate coordination polymer

The flexible zirconium tetraphosphonate coordination polymer with formula Zr(O(3)PCH(2))(2)N-C(6)H(10)-N(O(3)CH(2)P)(2)X(2-x)H(2+x)·nH(2)O (X = H, Li, Na, K, 0 < x < 1, 4 < n < 7.5) (1) possesses an open framework structure with 1D cavities decorated with polar and acids P═O and P-OH groups. 1 has been fully protonated by adding HCl and then subjected to several acid-base ion-exchange reactions with alkaline metals hydroxides. 1 is a very robust coordination polymer because it can be regenerated in H- form using strong acid solutions and ri-exchanged several times without hydrolysis and loss of crystallinity. The flexibility of 1 has been also studied by means of TDXD (temperature dependent X-ray diffraction) evidencing remarkable phase transformations that lead to a different disposition of the water molecules. These transformations also influence the accessibility of the cations on the P-OH groups placed inside the channels and thus the ion-exchange properties. The dependence of the proton conductivity properties on these phase transitions has been also investigated and discussed.     

Time domain bidirectional beam propagation method for second harmonic generation in multilayers

We propose a time domain bidirectional beam propagation method based on scattering operators for wide band pulse propagation in nonlinear multilayers. The reported numerical examples demonstrate the applicability of the algorithm for the analysis of temporal effects related to the process of second harmonic generation.     

Insights into phenylalanine derivatives recognition of VLA-4 integrin: from a pharmacophoric study to 3D-QSAR and molecular docking analyses

The very late antigen-4 (VLA-4), also known as integrin alpha4beta1, is expressed on monocytes, T- and B-lympohocytes, basophils, and eosinophils and is involved in the massive recruitment of granulocytes in different pathological conditions such as multiple sclerosis and asthma. VLA-4 interacts with its endogenous ligand VCAM-1 during chronic inflammation, and blockade of VLA-4 /VCAM-1 interaction is a potential target for immunosuppression. Two classes of VLA-4 antagonists have so far been reported: beta-amino acid derivatives containing a diaryl urea moiety (BIO-1211) and phenylalanine derivatives (TR-14035). With the aim of clarifying the structural basis responsible for VLA-4 recognition by phenylalanine derivatives, we developed a combined computational study on a set of 128 antagonists available through the literature. Our computational approach is composed of three parts. (i) A VCAM-1 based pharmacophore was constructed with a restricted number of phenylalanine derivatives to identify the region of the protein that resembles synthetic antagonists. The pharmacophore was instrumental in constructing an alignment of a set of 128 compounds. This alignment was exploited to build a pseudoreceptor model with the RECEPTOR program. (ii) 3D-QSAR analysis was carried out on the computed electrostatic and steric interaction energies with the pseudoreceptor surface. The 3D-QSAR analysis yielded a predictive model able to explain much of the variance of the 128 antagonists. (iii) A homology modeling study of the headpiece of VLA-4 based on the crystal structure of alphavbeta3 was performed. Docking experiments of TR-14035 into the binding site of VLA-4 aided the interpretation of the 3D-QSAR model. The obtained results will be fruitful for the design of new potent and selective antagonists of VLA-4.     

Influence of stereoregularity on binding of counterions by poly(methacrylic acid)

The activity coefficient γ, of sodium ion, in aqueous solutions of both isotactic and conventional poly(methacrylic acid) (PMA) has been studies throughout the whole range of degree of neutralization α with a Beckman Na electrode and membrane electrodes. The results show that the fraction of sodium ions bound to isotactic PMA is higher than that bound to conventional (or syndiotactic) PMA over the entire range of α. The binding of divalent counterions (Mg⁺², Cu⁺², Co⁺², and Ni⁺²) by the two forms of PMA (at α = 0.95) has been evaluated from the release of Na⁺ ions with the Beckman Na electrode. Turbidimetric determinations of the critical amount of various divalent cation chlorides necessary to bring about precipitation of both isotactic and conventional PMA (at α = 0.95) have also been carried out.     

Enantiomeric resolution of anti-HIV agents on a cellulose derivative chiral stationary phase. Note II

Summary A series of enantiomeric 1H,3H-thiazolo[3,4-a] benzimidazoles with anti-HIV activity has been stereospecifically analyzed.The enantiomeric resolution has been carried out by means of an HPLC method using a column of cellulose tris-(4-methyl-phenylbenzoate) ester adsorbed on macroporous silica gel (Chiralcel^R OJ).     

The first example of a copper(II) chloride complex with 1,3-thiazolidine-2-thione

Summary The reaction of copper(II) chloride with 1,3-thiazolidine-2-thione in absolute ethanol yields the complex CuL₂Cl₂. This derivative has been studied by elemental analyses, molar conductance, magnetic moment measurements at different temperatures, electronic and infrared spectroscopy, thermal analyses (TG and DTG) and e.p.r. techniques. The complex has a pseudooctahedral stereochemistry, with bridging halides and with the ligands monodentate-S-bondedvia the exocyclic sulphur atom.     

Pharmacophore model for bile acids recognition by the FPR receptor

Formyl-peptide receptors (FPRs) belong to the family A of the G-protein coupled receptor superfamily and include three subtypes: FPR, FPR-like-1 and FPR-like-2. They have been involved in the control of␣many inflammatory processes promoting the recruitment and infiltration of leukocytes in regions of inflammation through the molecular recognition of chemotactic factors. A large number of structurally diverse chemotypes modulate the activity of FPRs. Newly identified antagonists include bile acids deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA). The molecular recognition of these compounds at FPR receptor was computationally investigated using both ligand- and structure-based approaches. Our findings suggest that all antagonists bind at the first third of the seven helical bundles. A closer inspection of bile acid interaction reveals a number of unexploited anchor points in the binding site that may be used to aid the design of new potent and selective bile acids derivatives at FPR.     

Circulatory bubble dynamics: From physical to biological aspects

Bubbles can form in the body during or after decompression from pressure exposures such as those undergone by scuba divers, astronauts, caisson and tunnel workers. Bubble growth and detachment physics then becomes significant in predicting and controlling the probability of these bubbles causing mechanical problems by blocking vessels, displacing tissues, or inducing an inflammatory cascade if they persist for too long in the body before being dissolved. By contrast to decompression induced bubbles whose site of initial formation and exact composition are debated, there are other instances of bubbles in the bloodstream which are well-defined. Gas emboli unwillingly introduced during surgical procedures and ultrasound microbubbles injected for use as contrast or drug delivery agents are therefore also discussed. After presenting the different ways that bubbles can end up in the human bloodstream, the general mathematical formalism related to the physics of bubble growth and detachment from decompression is reviewed. Bubble behavior in the bloodstream is then discussed, including bubble dissolution in blood, bubble rheology and biological interactions for the different cases of bubble and blood composition considered.     

Determination of herbicides by solid phase extraction gas chromatography-mass spectrometry in drinking waters

A solid phase extraction (SPE) method has been optimized for the gas chromatography-mass spectrometry (GC-MS) simultaneous determination of herbicides belonging to the following different families: carbamate (molinate), atrazines (atrazine, propazine, simazine, ametryne, cyanazine, terbutylazine, deethylterbutylazine, deethylatrazine), dinitroaniline (trifluralin, pendimethalin), chloroacetamide (alachlor, metolachlor). Different solid substrates have been compared (C18, cyano, styrene-divinylbenzene, phenyl, graphitic carbon). The type of conditioning and elution solvent, its volume, and the sample flow rate have been considered as variables affecting the recovery yields of the herbicides.The optimized experimental conditions are C18 phase conditioned with 3 mL acetone, loaded with 1 L water sample at 5 mL min⁻¹, and eluted with 3 mL acetone. Good recoveries (included between 79% and 99%) and R.S.D. (included between 2% and 12%) have been obtained for all analytes, except for deethylatrazine whose recovery was 46 ± 7%. The recovery of deethylatrazine increases up to 94 ± 17% if a non-porous graphitic carbon is coupled to the C18 phase, keeping the other parameters constant as optimized. The optimized method has been successfully checked for the identification and quantitation of the selected herbicides in raw and drinking water samples, with quantitation limits as low as 0.01 μg L⁻¹, fully in agreement with the current legislation. The method is easily routinable. After development, the method is currently routinely applied for the analysis of herbicides in waters and, up today, more than one thousand samples have been analysed at the “Laboratorio della Società Metropolitana Acque di Torino” (Laboratory of the Municipal Waterworks of Turin) in charge of the control of drinking water quality in Torino.