Bactericidal block copolymer micelles

Block copolymer micelles with bactericidal properties were designed to deactivate pathogens such as E. coli bacteria. The micelles of PS‐b‐PAA and PS‐b‐P4VP block copolymers were loaded with biocides TCMTB or TCN up to 20 or 30 wt.‐%, depending on the type of antibacterial agent. Bacteria were exposed to loaded micelles and bacterial deactivation was evaluated. The micelles loaded with TCN are bactericidal; bacteria are killed in less than two minutes of exposure. The most likely interpretation of the data is that the biocide is transferred to the bacteria by repeated micelle/bacteria contacts, and not via the solution.

     

Determination of metal ions extracted by DTPA in a soil treated with effluent using an Hg-electroplated-Pt microelectrode

Determinations of Cu, Fe, Mn and Zn were performed in an oxisol soil treated with effluent originated from a biodigester septic cesspool. The extracts were obtained from a DTPA/TEA (pH 7.3) solution and analysed by electroanalytical methodologies using square wave anodic stripping voltammetry (SWASV) for the analysis of Cu, Mn and Zn and square wave voltammetry (SWV) for Fe analysis, both of them with a thin mercury film microelectrode (ME-Hg). DTPA (diethylenetriaminepentaacetic acid) complexes with Cu, Mn and Fe show electroactivity in the potentials range close to the ones for the free ions in solution, but the Zn complex did not show any electroactivity at the potential range analysed. SWASV/ME-Hg and SWV/ME-Hg results were in good agreement (r² = 0.996) with the flame atomic absorption spectroscopy (FAAS) analyses, demonstrating that electroanalytical methodologies can be used for micronutrient determinations in soil extracts without serious interferences of the matrix components. Some characteristics of the complex formed between DTPA-metals are explored by EPR experiments.     

Synthesis and structural characterization of a zinc(II) complex of the mycobactericidal drug isoniazid - Toxicity against Artemia salina

A new zinc(II) complex of the mycobactericidal drug isoniazid (complex 1) was synthesized and characterized by XRD, vibrational spectroscopy (IR, Raman) and thermogravimetric analysis. The complex is constituted by two isoniazid (INH) molecules, six hydration water molecules and two perchlorate counter-ions for each metal center (C₁₂H₂₆N₆Cl₂O₁₆Zn). Zinc(II) adopts a distorted octahedral geometry, where two INH molecules coordinate in a bidentate manner through the hydrazide group (N, O) and the other two isoniazid residues complete the coordination sphere of zinc(II) through their aromatic nitrogen atoms. This coordination pattern gives rise to a 2-D coordination polymer. Complex 1 belongs to the monoclinic system [a = 8.1190(2) Å, b = 17.977(4) Å, c = 9.1051(2) Å and β = 100.87(3)°], space group P2₁. A biological assay with Artemia salina was also performed. Complex 1 is almost 8.5 times more active than the free ligand. Its toxicity against A. salina correlates well with the cytotoxic activity for some human solid tumors. Therefore, antitumoral properties could be expected from complex 1.     

Macrocyclic multicenter complexes of nickel and copper of increasing complexity

Multicenter (bi-, tri-, and tetranuclear) tetraazamacrocyclic complexes were self-assembled from Ni and Cu tetraazamacrocyclic mononuclear units and α,ω-diamines as building blocks. The structures of all compounds studied were proved by spectroscopic methods (ESI MS and NMR spectroscopy). Electrochemical experiments revealed reversible one-electron electrode processes at each of the Ni(2+) and Cu(2+) centers with formation of metal cations in oxidation state +3. Long linkers allow bi- and trinuclear complexes with noninteracting metal centers to be obtained. In the case of the short linkers (e.g. ethylenediamine) higher, trinuclear species are formed as major product. The structures of the bis- and tris-macrocyclic systems were confirmed by single-crystal X-ray diffraction. The tris-macrocyclic systems form cations in the shape of triangles partially filled with counterions and solvent molecules. The cations form positively charged layers, which interact in the crystal lattice with the neighboring negatively charged layers of anions. In solution, the trinuclear complexes exhibit strong host-guest interactions with 9,10-dimethyltriptycene due to complementarity of shape and size of this guest molecule. The association constants were determined by NMR spectroscopy and voltammetry, and very good agreement was obtained. The structural flexibility of the tetranuclear complex with long linkers allows for attractive interactions between the metal-complexing macrocycles that result in folding of the molecule. On the contrary, no folding is possible in the case of short linkers consisting of two CH(2) groups.     

1H and 13C NMR spectral data of new saponins from Cordia piauhiensis

Two new bidesmoside triterpenoid saponins were isolated from stems of Cordia piauhiensis. Their structures, characterized as 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl pomolic acid 28-O-beta-D-glucopyranosyl ester (1) and 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (2), were unequivocally established after extensive NMR (1H, 13C, DEPT 135 degrees, COSY, HSQC, HMBC, TOCSY, and NOESY) studies.     

Analysis of some stilbenes in Italian wines by liquid chromatography/tandem mass spectrometry

Stilbenes from grapes and wines play a central role in the human diet because of their antioxidant, antimutagenic and anticarcinogenic properties. We describe a method for the direct determination of some stilbenes (cis- and trans-resveratrol, cis- and trans-resveratrol glucoside, cis- and trans-piceatannol, and cis- and trans-piceatannol glucoside) in wine by high-performance liquid chromatography/mass spectrometry using a triple quadrupole (QqQ) mass spectrometer, in multiple reaction monitoring (MRM) mode, acquiring two diagnostic product ions from the chosen precursor. All the target analytes were separated on a C-18 column using gradient elution, in a single run. Electrospray ionization (ESI) in negative ion mode gives higher sensitivity for all the target compounds than atmospheric pressure chemical ionization (APCI). For the identification of piceatannol glucoside (astringin), because of the lack of a suitable standard, an HPLC/TOFMS method was used. The method permits direct injection of samples and it is time-saving, removing the need for sample pre-treatment. The detection limits were 48.0 ng mL(-1) for cis- and trans-resveratrol and for cis- and trans-resveratrol glucoside, and 50.0 ng mL(-1) for cis- and trans-piceatannol. The procedure proved to be simple and suitable for routine and confirmatory purposes. A total of 19 red and 3 white Italian wines were analyzed and differences in the stilbene composition were found among these samples. Copyright (c) 2007 John Wiley & Sons, Ltd.     

Influence of preferential adsorption of mobile phase on retention behavior of amino acids on the teicoplanin chiral selector

The adsorption behavior of two amino acids, i.e., l,d-threonine and l,d-methionine has been investigated on the chiral stationary phase (CSP)column packed with teicoplanin bonded to a silica support. The study has been performed under non-linear conditions of adsorption isotherm for various types of organic modifiers (methanol, ethanol, propan-2-ol and acetonitrile) in the reversed-phase mode. A heterogeneous adsorption mechanism of amino acids has been identified that was strongly affected by the nature of organic modifier. Generally, isotherm non-linearity and retention decreased with decrease of the modifier content in the mobile phase exhibiting a minimum at water-rich mobile phases. These trends were suggested to result from a combined effect of the mobile as well as the adsorbed phase composition. To determine the composition of the adsorbed phase the excess adsorption of modifiers in aqueous solutions has been measured and their binary adsorption equilibria have been quantified and compared. Strongly non-ideal behavior of solvents in the mobile phase and the adsorbed phase has been accounted for by activity coefficients. The fraction of the modifiers in the adsorbed phase decreased in the sequence: methanol, ethanol, propan-2-ol and acetonitrile.     

Determination of phenolic acids in olive oil by capillary electrophoresis

A CZE method for the separation and quantitation of phenolic acids (cinnamic, syringic, p-coumaric, vanillic, caffeic, 3,4-dihydroxyphenylacetic, protocatechuic), extracted from extra virgin olive oil, was developed. The sample preparation involved the LLE and SPE extraction methods. CE separation was performed in a fused silica capillary of I.D.= 50microm using as a BGE 40 mM borate buffer at pH=9.2. The separation voltage was 18kV with corresponding current of 27-28 microA. Detection was accomplished with UV-detector at lambda=200nm. The proposed method was fully validated. A good repeatability of migration time (RSD% ranged from 0.81 to 1.63) and of corrected peak area (RSD% from 2.89 to 5.77) was obtained. The linearity of detector response in the range from 5 to 50 ppm was checked, obtaining the correlation coefficient R2 values in the range: 0.9919-0.9997. Some phenolic acids in real oil samples were detected and quantified with the proposed method.     

Efficient synthetic access to cationic dendrons and their application for ZnO nanoparticles surface functionalization: new building blocks for dye-sensitized solar cells

A new concept for the efficient synthesis of cationic dendrons, 4-tert-butyl-1-(3-(3,4-dihydroxybenzamido)benzyl)pyridinium bromide (17), 1,1'-(5-(3,4-dihydroxybenzamido)-1,3-phenylene)bis(methylene)bis(4-tert-butylpyridinium) bromide (18), N1,N7-bis(3-(4-tert-butyl-pyridium-methyl)phenyl)-4-(3-(3-(4-tert-butyl-pyridinium-methyl)phenyl-amino)-3-oxopropyl)-4-(3,4-dihydroxybenzamido)heptanediamide tribromide (19), and N1,N7-bis(3,5-bis(4-tert-butyl-pyridium-methyl)phenyl)-4-(3-(3,5-bis(4-tert-butyl-pyridinium-methyl)phenylamino)-3-oxopropyl)-4-(3,4-dihydroxybenzamido)heptanediamide hexabromide (20), and their facile binding to zinc oxide (ZnO) nanostructures is introduced. Dendrons containing highly reactive benzylic bromides reacted readily with 4-tert-butyl-pyridine and resulted in cationic dendrons. Furthermore, these permanently positively charged dendrons were equipped with a catechol anchor group. This enabled ZnO surface functionalization by simple immersion. The adsorption of 17, 18, 19, and 20 on the colloidal nanoparticles was monitored by Langmuir isotherms. The highest obtained experimental loadings correspond to 99.5%, 98.6%, 99.1%, and 42.5% of the particle surface for 17, 18, 19, and 20, respectively. These results indicate insufficient adsorption of the largest molecule 20 leading to reduced colloidal stability of the nanoparticles, while an enhanced stability after grafting with 17, 18, and 19 was observed. Mesoporous films suitable for the use as electrodes in dye-sensitized solar cells (DSSCs) were prepared. Subsequently, the films were functionalized with 18, 19, or 20 and sensitized with zinc-5,15-bis-[2',6'-bis-{2',2'-bis-(carboxy)-ethyl}-methyl-4'-tert-butyl-pheny]-10,20-bis-(4'-tert-butylphenyl)porphyrin-octasodium-salt. UV-vis absorption spectra confirmed that 18, 19, and 20 are suitable for the stable electrostatic attachment of the dye. Current-voltage characteristics of complete cells demonstrated that increasing positive functionalization of the ZnO surface leads to decreased open circuit voltages (V(oc)). All V(oc) values were around 0.4 V with a maximum for the 18 functionalized ZnO film of 0.45 V. The maximum cell efficiency obtained (0.31%) is rather high, considering the narrow spectral absorption of the dye and the rather thin ZnO films used. Finally, incident photon to current efficiency (IPCE) measurements confirmed photoinduced electron injection from the dye. These features are important assets for applications in particle technology and even facilitated advanced devices like a supramolecular DSSC complete with a subsequent layer of negatively charged porphyrins.