NMR characterization of blends of poly(hydroxybutyrate-co-hydroxyvalerate) with poly(vinyl acetate)

The extent of mixing in blends of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) (27% HV) and poly(vinyl acetate) (PVAc) has been measured using a number of different techniques, principally solid-state NMR. Differential scanning calorimetry DSC measurements indicated effective mixing of the polymer chains on a scale of several nanometres. The results of H-1 T-1 and H-1 T-1rho. measurements confirm intimate mixing of the chains. A change on blending in the H-1 T-1rho, and the H-1 NMR line width of the signal from the protons of PVAc was consistent with an increase in the amplitude and frequency of motion of this component. The PVAc chains reside within the inter-lamellar space, as confirmed by spin diffusion measurements after H-1 T-1rho preparation. (C) 2003 Society of Chemical Industry.

Antimicrobial Activity of Rosmarinus officinalis against Oral Pathogens: Relevance of Carnosic Acid and Carnosol

The in vitro inhibitory activity of crude EtOH/H(2)O extracts from the leaves and stems of Rosmarinus officinalis L. was evaluated against the following microorganisms responsible for initiating dental caries: Streptococcus mutans, salivarius, S. sobrinus, S. mitts 5 sanguinis, and Enterococcus faecalis. Minimum inhibitory concentrations (MIC) were determined with the broth microdilution method. The bioassay-guided fractionation of the leaf extract, which displayed the higher antibacterial activity than the stem extract, led to the identification of carnosic acid (2) and carnosol (3) as the major compounds in the fraction displaying the highest activity, as identified by HPLC analysis. Rosmarinic acid (1), detected in another fraction, did not display any activity against the selected microorganisms. HPLC Analysis revealed the presence of low amounts of ursolic acid (4) and oleanolic acid (5) in the obtained fractions. The results suggest that the antimicrobial activity of the extract from the leaves of R. officinalis may be ascribed mainly to the action of 2 and 3.

Synthesis and characterization of ternary hybrid material based on poly-o-methoxyaniline and poly(ethylene oxide) in mesostructured V(2)O(5)

New hybrid composites based on mesostructured V(2)O(5) containing intercalated poly(ethylene oxide), poly-o-methoxyaniline and poly(ethylene oxide)/poly-o-methoxyaniline were prepared. The results suggest that the polymers were intercalated into the layers of the mesostructured V(2)O(5). Electrochemical studies showed that the presence of both polymers in the mesostructured V(2)O(5) (ternary hybrid) leads to an increase in total charge and stability after several cycles compared with binary hybrid composites. This fact makes this material a potential component as cathode for lithium ion intercalation and further, a promising candidate for applications in batteries.

Solid-phase microextraction using poly(pyrrole) film and liquid chromatography with UV detection for analysis of antidepressants in plasma samples

Poly(pyrrole) (PPY) coating was prepared on a stainless-steel (SS) wire for solid-phase microextraction (SPME) by electrochemical deposition (cyclic voltammetric). The PPY was evaluated by analyzing new-generation antidepressants (mirtazapine, citalopram, paroxetine, duloxetine, fluoxetine, and sertraline) in plasma sample by SPME and liquid chromatography with UV detection (LC-UV). The effect of electrolyte Solution (lithium perchlorate or tetrabutylammonium perchlorate) and the number of cycles (50, 100 or 200) applied during the polymerization process on the SPME performance was evaluated. Important factors in the optimization of SPME efficiency such as extraction time, temperature, pH, influence of plasma proteins on sorption mechanisms, and desorption conditions are discussed. The SPME-PPY/LC method showed to be linear in concentrations ranging from the limit of quantification (LOQ) to 1200 ng mL(-1). The LOQ values range from 16 to 25 ng mL-1. The inter-day precision of the SPME-PPY/LC method presented coefficient of variation (CV) lower than 15%. Based on analytical validation results, the SPME-PPY/LC methodology showed to be adequate for antidepressant analysis, from therapeutic to toxic levels. In order to evaluate the proposed method for clinical use, the SPME-PPY/LC method was applied to the analysis of plasma samples from elderly depressed patients. (c) 2009 Elsevier B.V. All rights reserved,

Evaluation of the Binding Properties of Maghemite Nanoparticle Surface-Coated with Meso-2-3-Dimercaptosuccinic Acid to Serum Albumin

In this study the interaction between magnetic nanoparticles (MNPs) surface-coated with meso-2,3-dimercaptosuccinic acid (DMSA) with both bovine serum albumin (BSA) and human serum albumin (HSA) was investigated. The binding of the MNP-DMSA was probed by the fluorescence quenching of the BSA and HSA tryptophan residue. Magnetic resonance and light microscopy analyses were carried out in in vivo tests using female Swiss mice. The binding constants (K(b)) and the complex stoichiometries (n) indicate that MNP-DMSA/BSA and MNP-DMSA/HSA complexes have low association profiles. After five minutes following intravenous injection of MNP-DMSA into mice`s blood stream we found the lung firstly target by the MNP-DMSA, followed by the liver in a latter stage. This finding suggests that the nanoparticle`s DMSA-coating process probably hides the thiol group, through which albumin usually binds. This indicates that biocompatible MNP-DMSA is a very promising material system to be used as a drug delivery system (DDS), primarily for lung cancer treatment.

Electrocatalytic oxidation of ethanol on Sn((1-x))Ir((x))O(2) electrodes in acid medium

The electrochemical oxidation of ethanol at Sn((1-x))Ir (x) O(2) electrodes (with x = 0.01, 0.05, 0.1 and 0.3) was studied in 0.1 mol L(-1) HClO(4) solution. Electrolysis experiments were carried out and the reaction products were analyzed by Liquid Chromatography. It was found that the amounts of the reaction products depended on the composition of the electrode. In situ infrared reflectance spectroscopy measurements were performed to identify the adsorbed intermediates and to postulate a reaction mechanism for ethanol electrooxidation on these electrode materials. As evidence, acetaldehyde and acetic acid were formed through a successive reaction process. Carbon dioxide was also identified as the end product, showing that the cleavage of the carbon-carbon bond occurred. These results indicate that the synthesized catalysts are able to lead to the total combustion of organic compounds. Analysis of the water bending band at different potentials illustrated its role at the electrode interface.

Spectroelectrochemistry and investigation of charge transport mechanisms of iron poly(pyridyl) redox polymers

In this work, we describe the characterization of the complex [Fe(tpy-NH2)(2)](PF6)(2) (tpy-NH2 = bis[4`-(3-aminophenyl)-2, 2`:6`,2 ``-terpyridine]. The complex was oxidatively electropolymerized on glassy.-carbon electrodes in CH3CN/0.1 M tetraethylammonium perchlorate (TEAP) to generate polymer films that exhibit reversible oxidative electrochemical behavior in a wide potential range (0.0-1.6 V), as well as high conductivity and stability/durability. In situ spectrocyclic voltammetry of this modified electrode was carried out on a photodiode array spectrophotometer attached to a potentiostat, which provided UV-Vis absorption spectra of the redox species during the potential sweep. We determined charge transport parameters as a function of time and thickness of the modified electrode, and the results showed that poly-[[Fe(tpy-NH2)(2)](2+)](n) can be made to exhibit three regimes of charge transport behavior by manipulation of the film thickness and the experimental time-scale. Morphological characterization of the film was provided by atomic force microscopy. (C) 2008 Elsevier Ltd. All rights reserved.

Homocysteine-lowering treatment with folic acid, cobalamin, and pyridoxine does not reduce blood markers of inflammation, endothelial dysfunction, or hypercoagulability in patients with previous transient ischemic attack or stroke - a randomized substudy

Background and Purpose - Epidemiological and laboratory studies suggest that increasing concentrations of plasma homocysteine ( total homocysteine [tHcy]) accelerate cardiovascular disease by promoting vascular inflammation, endothelial dysfunction, and hypercoagulability. Methods - We conducted a randomized controlled trial in 285 patients with recent transient ischemic attack or stroke to examine the effect of lowering tHcy with folic acid 2 mg, vitamin B-12 0.5 mg, and vitamin B-6 25 mg compared with placebo on laboratory markers of vascular inflammation, endothelial dysfunction, and hypercoagulability. Results - At 6 months after randomization, there was no significant difference in blood concentrations of markers of vascular inflammation (high-sensitivity C-reactive protein [P = 0.32]; soluble CD40L [ P = 0.33]; IL-6 [P = 0.77]), endothelial dysfunction ( vascular cell adhesion molecule-1 [P = 0.27]; intercellular adhesion molecule-1 [P = 0.08]; von Willebrand factor [P = 0.92]), and hypercoagulability (P-selectin [P = 0.33]; prothrombin fragment 1 and 2 [P = 0.81]; D-dimer [P = 0.88]) among patients assigned vitamin therapy compared with placebo despite a 3.7-mumol/L (95% CI, 2.7 to 4.7) reduction in total homocysteine (tHcy). Conclusions - Lowering tHcy by 3.7 mumol/L with folic acid-based multivitamin therapy does not significantly reduce blood concentrations of the biomarkers of inflammation, endothelial dysfunction, or hypercoagulability measured in our study. The possible explanations for our findings are: ( 1) these biomarkers are not sensitive to the effects of lowering tHcy (eg, multiple risk factor interventions may be required); ( 2) elevated tHcy causes cardiovascular disease by mechanisms other than the biomarkers measured; or ( 3) elevated tHcy is a noncausal marker of increased vascular risk.

Synthesis and Characterization of Semi-Interpenetrating Networks Based on Poly(dimethylsiloxane) and Poly(vinyl alcohol)

Semi-interpenetrating networks (Semi-IPNs) with different compositions were prepared from poly(dimethylsiloxane) (PDMS), tetraethylorthosilicate (TEOS), and poly (vinyl alcohol) (PVA) by the sol-gel process in this study. The characterization of the PDMS/PVA semi-IPN was carried out using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and swelling measurements. The presence of PVA domains dispersed in the PDMS network disrupted the network and allowed PDMS to crystallize, as observed by the crystallization and melting peaks in the DSC analyses. Because of the presence of hydrophilic (-OH) and hydrophobic (Si-(CH(3))(2)) domains, there was an appropriate hydrophylic/hydrophobic balance in the semi-IPNs prepared, which led to a maximum equilibrium water content of similar to 14 wt % without a loss in the ability to swell less polar solvents. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 158-166, 2010

Electrochemical oxidation of acid black 210 dye on the boron-doped diamond electrode in the presence of phosphate ions: Effect of current density, pH, and chloride ions

The electrochemical oxidation of acid black 210 dye (AB-210) on the boron-doped diamond (BDD) was investigated under different pH conditions. The best performance for the AB-210 oxidation occurred in alkaline phosphate solution. This is probably due to oxidizing agents such as phosphate radicals and peroxodiphosphate ions, which can be electrochemically produced with good yields on the BDD anode, mainly in alkaline solution. Under this condition, the COD (chemical oxygen demand) removal was higher than that obtained from the model proposed by Comninellis. Electrolyses performed in phosphate buffer and in the presence of chloride ions resulted in faster COD and color removals in acid and neutral solutions, but in alkaline phosphate solution, a better performance in terms of TOC removal was obtained in the absence of chloride. Moreover, organochloride compounds were detected in all electrolyses performed in the presence of chloride. The AB-210 electrooxidation on BDD using phosphate as supporting electrolyte proved to be interesting since oxidizing species generated from phosphate ions were able to completely degrade the dye without producing organochloride compounds. (C) 2009 Elsevier Ltd. All rights reserved.

Solvent Effects in Optical Spectra of ortho-Aminobenzoic Acid Derivatives

We investigated three amino derivatives of ortho-aminobenzoic or anthranilic acid (o-Abz): a) 2-Amino-benzamide (AbzNH(2)); b) 2-Amino-N-methyl-benzamide (AbzNHCH(3)) and c) 2-Amino-N-N`-dimethyl-bezamide (AbzNH(CH(3))(2)), see Scheme 1. We describe the results of ab-initio calculations on the structural characteristics of the compounds and experimental studies about solvent effects in their absorption and steady-state and time-resolved emission properties. Ab-initio calculations showed higher stability for the rotameric conformation in which the oxygen of carbonyl is near to the nitrogen of ortho-amino group. The derivatives present decrease in the delocalization of pi electron, and absorption bands are blue shifted compared to the parent compound absorption, the extent of the effect increasing from to Abz-NH(2) to Abz-NHCH(3) Abz-NH(CH(3))(2). Measurements performed in several solvents have shown that the the dependence of Stokes shift of the derivatives with the orientational polarizability follows the Onsager-Lippert model for general effects of solvent. However deviation occurred in solvents with properties of Bronsted acids, or electron acceptor characteristics, so that hydrogen bonds formed with protic solvents predominates over intramolecular hydrogen bond. In most solvents the fluorescence decay of AbzNH(2) and AbzNHCH(3) was fitted to a single exponential with lifetimes around 7.0 ns and no correlation with polarity of the solvent was observed. The fluorescence decay of AbzN(CH(3))(2) showed lifetimes around 2.0 ns, consistent with low quantum yield of the compound. The spectroscopic properties of the monoamino derivative AbzNHCH(3) are representative of the properties presented by Abz labelled peptides and fatty acids previously studied.

Interaction of adrenocorticotropin peptides with microheterogeneous systems - A fluorescence study

Adrenocorticotropin (ACM) and alpha-melanocyte stimulating hormone (alpha-MSH) are peptides which present many physiological effects related to pigmentation, motor and sexual behavior, learning and memory, analgesia, anti-inflammatory and antipyretic processes. The 13 amino acid residues of alpha-MSH are the same initial sequence of ACM and due to the presence of a tryptophan residue in position 9 of the peptide chain, fluorescence techniques could be used to investigate the conformational properties of the hormones in different environments and the mechanisms of interaction with biomimetic systems like sodium dodecyl sulphate (SDS) micelles, sodium dodecyl sulphate-poly(ethylene oxide) (SDS-PEO) aggregates and neutral polymeric micelles. In buffer solution, fluorescence parameters were typical of peptides containing tryptophan exposed to the aqueous medium and upon addition of surfactant and polymer molecules, the gradual change of those parameters demonstrated the interaction of the peptides with the microheterogeneous systems. From time-resolved experiments it was shown that the interaction proceeded with conformational changes in both peptides, and further information was obtained from quenching of Trp fluorescence by a family of N-alkylpyridinium ions, which possess affinity to the microheterogeneous systems dependent on the length of the alkyl chain. The quenching of Trp fluorescence was enhanced in the presence of charged micelles, compared to the buffer solution and the accessibility of the fluorophore to the quencher was dependent on the peptide and the alkylpyridinium: in ACTH(1-21) highest collisional constants were obtained using ethylpyridinium as quencher, indicating a location of the residue in the surface of the micelle, while in alpha-MSH the best quencher was hexylpyridinium, indicating insertion of the residue into the non-polar region of the micelles. The results had shown that the interaction between the peptides and the biomimetic systems where driven by combined electrostatic and hydrophobic effects: in ACTH(1-24) the electrostatic interaction between highly positively charged C-terminal and negatively charged surface of micelles; and aggregates predominates over hydrophobic interactions involving residues in the central region of the peptide; in alpha-MSH, which presents one residual positive charge, the hydrophobic interactions are relevant to position the Trp residue in the non-polar region of the microheterogeneous systems. (C) 2008 Elsevier B.V. All rights reserved.