Re-examination of the anion derivatives of isoflavones by radical fragmentation in negative electrospray ionization tandem mass spectrometry: experimental and computational studies

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electroactive LbL films of metallic phthalocyanines and poly(O-methoxyaniline) for sensing

Multilayered nanostructured films have been widely investigated for electrochemical applications as modified electrodes, including the layer-by-layer (LbL) films where properties such as thickness and film architecture can be controlled at the molecular level. In this study, we investigate the electrochemical features of LbL films of poly (o-methoxyaniline; POMA) and tetrasulfonated phthalocyanines containing nickel (NiTsPc) or copper (CuTsPc). The films displayed well-defined electroactivity, with redox pairs at 156 and 347 mV vs SCE, characteristic of POMA, which allowed their use as modified electrodes for detecting dopamine and ascorbic acid at concentrations as low as 10(-5) M.

Preparation, characterization and taste sensing properties of Langmuir-Blodgett Films from mixtures of polyaniline and a ruthenium complex

Langmuir-Blodgett (LB) films from a ruthenium complex, mer-[RuCl3(dppb)(py)] (dppb = PPh2(CH2)(4)PPh2; py = pyridine) (Rupy), and from mixtures with varied amounts of polyaniline (PANi) were fabricated. Molecular-level interactions between the two components are investigated by surface potential, dc conductivity and Raman spectroscopy measurements, particularly for the mixed film with 10% of Rupy. For the latter, the better miscibility led to an interaction with Rupy inducing a decrease in the conducting state of PANi, as observed in the Raman spectra and conductivity measurement. The interaction causes the final film properties to depend on the concentration of Rupy, and this was exploited to produce a sensor array made up of sensing units consisting of 11-layer LB films from pure PANi, pure Rupy and mixtures with 10 and 30% of Rupy. It is shown that the combination of only four non-specific sensing units allows one to distinguish the basic tastes detected by biological systems, viz. saltiness, sweetness, sourness and bitterness, at the muM level. (C) 2003 Elsevier B.V. Ltd. All rights reserved.

Nanostructured films employed as sensing units in an electronic tongue system

Nanostructured films of lignin (macromolecule extracted from sugar cane bagasse), polypyrrole (conducting polymer) and bis butylimido perylene (organic dye) were used in the detection of trace levels of fluorine (from H2SiF6), chlorine (from NaCIO), Pb+2, Cu+2, and Cd+2 in aqueous solutions. Langmuir monolayers on ultrapure water were characterised by surface pressure-mean molecular area (II-A) isotherms. Langmuir-Blodgett (LB) films were transferred onto gold interdigitated electrodes and used as individual sensing units of an electronic tongue system. Impedance spectroscopy measurements were taken with the sensor immersed into aqueous solutions containing the ions described above in different molar concentrations. Fourier transform infrared absorption (FTIR) was employed to identify possible interactions between the LB films and the analytes in solution, and no significant changes could be observed in the FTIR spectra of BuPTCD and Ppy. Therefore, the results for lignin point to an interaction involving the electronic cloud of the phenyl groups with the metallic ions.

Polystyrene-type resin used for peptide synthesis: application for anion-exchange and affinity chromatography

This paper deals with an unusual application for a copolymer of styrene-1 % divinylbenzene bearing high amount of aminomethyl groups for anion-exchange and affinity chromatography. The so-called aminomethyl resin (AMR), to date only employed for peptide synthesis, swelled appreciably in water and was used successfully to purify negatively charged peptides. By correlating swelling degree of beads with pH of the media, it was possible to estimate that the AMR amino group pK(a) is approximately 5.5. In addition, the synthesized acetyl-(NANP)(3)-AMR succeeded in the affinity interaction with large antibody molecules related to malaria transmission and raised previously against this dodecapeptide sequence. (C) 2004 Elsevier B.V. All rights reserved.

A study of habitat fragmentation in Southeastern Brazil using remote sensing and geographic information systems (GIS)

The purpose of this work was to study fragmentation of forest formations (mesophytic forest, riparian woodland and savannah vegetation (cerrado)) in a 15,774-ha study area located in the Municipal District of Botucatu in Southeastern Brazil (São Paulo State). A land use and land cover map was made from a color composition of a Landsat-5 thematic mapper (TM) image. The edge effect caused by habitat fragmentation was assessed by overlaying, on a geographic information system (GIS), the land use and land cover data with the spectral ratio. The degree of habitat fragmentation was analyzed by deriving: 1. mean patch area and perimeter; 2. patch number and density; 3. perimeter-area ratio, fractal dimension (D), and shape diversity index (SI); and 4. distance between patches and dispersion index (R). In addition, the following relationships were modeled: 1. distribution of natural vegetation patch sizes; 2. perimeter-area relationship and the number and area of natural vegetation patches; 3. edge effect caused by habitat fragmentation, the values of R indicated that savannah patches (R = 0.86) were aggregated while patches of natural vegetation as a whole (R = 1.02) were randomly dispersed in the landscape. There was a high frequency of small patches in the landscape whereas large patches were rare. In the perimeter-area relationship, there was no sign of scale distinction in the patch shapes, In the patch number-landscape area relationship, D, though apparently scale-dependent, tends to be constant as area increases. This phenomenon was correlated with the tendency to reach a constant density as the working scale was increased, on the edge effect analysis, the edge-center distance was properly estimated by a model in which the edge-center distance was considered a function of the to;al patch area and the SI. (C) 1997 Elsevier B.V. B.V.

Use of commercial anion-exchange resins as solid support for peptide synthesis and affinity chromatography

This report demonstrates that due to the presence of residual reactive sites in their matrices, classical diethylaminoethyl-attaching commercial anion-exchanger resins such as DEAE-MacroPrep and DEAE-Sephadex A50 supports can be used for peptide synthesis. Moreover, due to the high stability of the peptide-resin bond in the final cleavage treatments, desired peptidyl-resins free of side-chain protecting groups, which enables them to be further used as solid support for affinity chromatography, can be obtained. To demonstrate this potentiality, a fragment corresponding to the antigenic and immunodominant epitope of sporozoites of the Plasmodium falciparum malaria parasite was synthesized in these traditional resins and antibody molecules generated against the peptide sequence were successfully retained in these peptidyl supports. Due to the maintenance of their original anion-exchange capacities, the present findings open the unique possibility of applying, simultaneously, dual anion-exchange and affinity procedures for purification of a variety of macromolecules. (C) 2003 Elsevier B.V. (USA). All rights reserved.

Nanoscale processing of polyaniline and phthalocyanines for sensing applications

Nanostructured polyaniline-modified electrodes were fabricated via the electrostatic layer-by-layer (LbL) technique where polyaniline (PANI) was assembled with one of three tetrasulfonated metallic phthalocyanines, viz. iron (FeTsPc), nickel (NiTsPc) and copper (CuTsPc). The multilayer formation was monitored via UV-vis spectroscopy by measuring the increase in the 800 run absorption band due to PANI. Infrared spectroscopy in the transmission mode suggested specific interactions between PANI and the phthalocyanines, such as those between SO3- groups from the phthalocyanines and the protonated NH group from PANI. The films were employed to detect dopamine (DA) using cyclic voltammetry. In the presence of dopamine the PANI-based LbL films showed additional redox peaks at ca. 230 and 190 mV the oxidation peak increased linearly with the concentration of DA in the electrolytic solution. Films comprising PANI/FeTsPc were able to distinguish between DA and ascorbic acid (AA), which acts as a natural interferent in biological fluids. (c) 2005 Elsevier B.V. All rights reserved.

BEHAVIOR OF THE ANION-RADICALS ELECTROCHEMICALLY GENERATED IN THE REDUCTION OF NOSYL AMIDES

The behaviour of nitrobenzenesulfonamide anion radicals generated from the electrochemical reduction of aliphatic and aromatic amines protected by nitrobenzenesulfonyl (nosyl) groups in N,N-' dimethylformamide has been reported. The species have been characterized by voltammetry and optical and electron spin resonance spectroscopies. The visible spectra of the anion radicals were recorded and the hyperfine splitting constants were assigned to specific proton positions and nitrogen nuclei of the molecule. The stabilities of the anion radicals are affected by electronic properties of the protecting group and specific features of the amines, which show direct influence on the route of cathodic cleavage of the nitrobenzenesulfonamides.

Novel allosteric conformation of human HB revealed by the hydration and anion effects on O-2 binding

The effect of anions on the stability of different functional conformations of Hb is examined through the determination of the dependence of O-2 affinity on water activity (a(w)). The control of a(w) is effected by varying the sucrose osmolal concentration in the bathing solution according to the osmotic stress method. Thus, the hydration change following Hb oxygenation is determined as a function of Cl- and of DPG concentration. We find that only similar to 25 additional water molecules bind to human Hb during the deoxy-to-oxy conformation transition in the absence of anions, in contrast with similar to 72 that bind in the presence of more than 50 mM Cl- or more than 15 mu M DPG. We demonstrate that the increase in the hydration change linked with oxygenation is coupled with anion binding to the deoxy-Hb. Hence, we propose that the deoxy-Hb coexists in two allosteric conformations which depend on whether anion is bound or not: the tense T-state, with low oxygen affinity and anion bound, or a new allosteric P-state, with intermediate oxygen affinity and free of bound anions. The intrinsic oxygen affinity of this unforeseen P-state and the differential binding of Cl-, DPG, and H2O between states P and T and P and R are characteristics which are consistent with those expected for a putative intermediate allosteric state of Hb. These findings represent a new opportunity to explore the structure-function relationships of hemoglobin regulation.

Regeneration of poly-L-lysine modified carbon electrodes in the accumulation and cathodic stripping voltammetric determination of the cromoglycate anion

Cromoglycate is accumulated on a poly-L-lysine (PLL) modified carbon electrode best from pH 4 solution, where it is anionic and the PLL is cationic, and at which pH the cromoglycate gives a good reduction peak at -0.82 V. The PLL film can be regenerated readily by washing the electrode with 3 M sodium hydroxide solution, in which the PLL is deprotonated. Regeneration of the film is not required as frequently when larger amounts of PLL are incorporated into it. This allows standard addition procedures to be carried out without regenerating the electrode. Linear calibration graphs have been obtained typically in the range 0.1 - 1.5 mug ml(-1). Detection limits have been calculated to be 10 ng ml(-1). The standard addition method has been applied satisfactorily to diluted urine solutions. (C) 2003 Elsevier B.V. B.V. All rights reserved.

PROLACTIN INDUCES MATURATION OF GLUCOSE SENSING MECHANISMS IN CULTURED NEONATAL RAT ISLETS

The effects of PRL treatment on insulin content and secretion, and Rb-86 and Ca-45 fluxes from neonatal rat islets maintained in culture for 7-9 days were studied. PRL treatment enhanced islet insulin content by 40% and enhanced early insulin secretion evoked by 16.7 mm glucose. Insulin release stimulated by oxotremorine-M, a muscarinic agonist, in the presence of glucose (8.3 or 16.7 mm) was unchanged by PRL treatment. However, PRL treatment potentiated phorbol 12,13-dibutyrate-stimulated insulin secretion in the presence of the above glucose concentrations. PRL treatment potentiated the reduction in Rb-86 efflux induced by glucose or tolbutamide and enhanced the increase in Rb-86 efflux evoked by diazoxide. PRL treatment slightly potentiated the increment in Ca-45 uptake induced by high concentrations of K+, but failed to affect the increment evoked by 16.7 mm glucose. Since glucose-induced Ca-45 uptake was not affected by PRL, we suggest that the enhancement in first phase insulin secretion evoked by glucose in the PRL-treated islets occurs at a step in the secretory process that may involve protein kinase-C. These data further support observations that PRL treatment increases islet sensitivity to glucose.

Remote sensing techniques applied to slope failure analysis

The paper evaluates the applicability of products of remote sensing in studies related to the structural conditionings of slope stability in saprolites, usually conducted through field surveys. In this article we use a regional approach concentrating on an area of lane duplication of a major highway. In that area, resistance reduction to stress and the low cohesions of muscovite saprolites - schists and gneiss which are associated to geological discontinuities, all result in inumerous instabilities. The joints and foliations were extracted from satellite images as well as aerial photographs. Following that, the study area was divided into various sectors based on the directions and dips of the foliation. Different relationships between the structures and the slopes were analyzed in order to indicate the most feasible type of slope failure in each sector of analysis. The aim of the study is to subsidize further detailed future research.

Natural gum-assisted phthalocyanine immobilization in electroactive nanocomposites: Physicochemical characterization and sensing applications

Natural gums have been traditionally applied in cosmetics and the food industry, mainly as emulsification agents. Due to their biodegradability and excellent mechanical properties, new technological applications have been proposed involving their use with conventional polymers forming blends and composites. In this study, we take advantage of the polyelectrolyte character exhibited by the natural gum Chicha (Sterculia striata), extracted in the Northeastern region of Brazil, to produce electroactive nanocomposites. The nanocomposites were fabricated in the form of ultrathin films by combining a metallic phthalocyanine (nickel tetrasulfonated phthalocyanine, NiTsPc) and the Chicha gum in a tetralayer architecture, in conjunction with conventional polyelectrolytes. The presence of the gum led to an efficient adsorption of the phthalocyanine and enhanced the electrochemical response of the films. Upon combining the electrochemical and UV-vis absorption data, energy diagrams of the Chicha/NiTsPc-based system were obtained. Furthermore, modified electrodes based on gum/phthalocyanine films were able to detect dopamine at concentrations as low as 10(-5) M.

Immobilization of humic acid in nanostructured layer-by-layer films for sensing applications

Humic acids (HAs), naturally occurring biomacromolecules, were incorporated into nanostructured polymeric films using the layer-by-layer (LbL) technique, in which HA layers were alternated with layers of poly(allylamine hydrochloride) (PAH). Atomic force microscopy (AFM) revealed very smooth films, with mean roughness varying from 0.89 to 1.19 nm for films containing 5 and 15 PAH/HA bilayers, respectively. The films displayed electroactivity, with the presence of only one reduction peak at ca. 0.675 V (vs Ag/AgCl). Such a well-defined electroactivity allowed the films to be used as highly sensitive pesticide sensors, with detection of pentachlorophenol (PCP) in solutions at concentrations as low as 10(-9) mol L(-1).