Effect of power densities and irradiation times on the degree of conversion and temperature increase of a microhybrid dental composite resin

The different parameters used for the photoactivation process provide changes in the degree of conversion (DC%) and temperature rise (TR) of the composite resins. Thus, the purpose of this study was to evaluate the DC (%) and TR of the microhybrid composite resin photoactivated by a new generation LED. For the KBr pellet technique, the composite resin was placed into a metallic mould (1-mm thickness and 4-mm diameter) and photoactivated as follows: continuous LED LCU with different power density values (50-1000 mW/cm(2)). The measurements for the DC (%) were made in a FTIR Spectrometer Bomen (model MB-102, Quebec-Canada). The spectroscopy (FTIR) spectra for both uncured and cured samples were analyzed using an accessory for the diffuse reflectance. The measurements were recorded in the absorbance operating under the following conditions: 32 scans, 4-cm(-1) resolution, and a 300 to 4000-cm(-1) wavelength. The percentage of unreacted carbon-carbon double bonds (% C=C) was determined from the ratio of the absorbance intensities of aliphatic C=C (peak at 1638 cm(-1)) against an internal standard before and after the curing of the specimen: aromatic C-C (peak at 1608 cm-1). For the TR, the samples were made in a metallic mould (2-mm thickness and 4-mm diameter) and photoactivated during 5, 10, and 20 s. The thermocouple was attached to the multimeter to allow the temperature readings. The DC (%) and TR were calculated by the standard technique and submitted to ANOVA and Tukey`s test (p < 0.05). The degree of conversion values varied from 35.0 (+/- 1.3) to 45.0 (+/- 2.4) for 5 s, 45.0 (+/- 1.3) to 55.0 (+/- 2.4) for 10 s, and 47.0 (+/- 1.3) to 52.0 (+/- 2.4) for 20 s. For the TR, the values ranged from 0.3 (+/- 0.01) to 5.4 (+/- 0.11)degrees C for 5 s, from 0.5 (+/- 0.02) to 9.3 (+/- 0.28)degrees C for 10 s, and from 1.0 (+/- 0.06) to 15.0 (+/- 0.95)degrees C for 20 s. The power densities and irradiation times showed a significant effect on the degree of conversion and temperature rise.

Influence of light guide tip used in the photo-activation on degree of conversion and hardness of one nanofilled dental composite

The aim of this study was to evaluate the degree of conversion and hardness of a dental composite resin Filtek (TM) Z-350 (3M ESPE, Dental Products St. Paul, MN) photo-activated for 20 s of irradiation time with two different light guide tips, metal and polymer, coupled on blue LED Ultraled LCU (Dabi Atlante, SP, Brazil). With the metal light tip, power density was of 352 and with the polymer was of 456 mW/cm(2), respectively. Five samples (4 mm in diameter and 2mm in thickness-ISO 4049), were made for each Group evaluated. The measurements for DC (%) were made in a Nexus-470 FT-IR, Thermo Nicolet, E.U.A. Spectroscopy (FTIR). Spectra for both uncured and cured samples were analyzed using an accessory of reflectance diffuse. The measurements were recorded in absorbance operating under the following conditions: 32 scans, 4 cm(-1) resolution, 300-4000 cm(-1) wavelength. The percentage of unreacted carbon double bonds (% C=C) was determined from the ratio of absorbance intensities of aliphatic C=C (peak at 1637 cm(-1)) against internal standard before and after curing of the sample: aromatic C-C (peak at 1610 cm(-1)). The Vickers hardness measurements (top and bottom surfaces) were performed in a universal testing machine (Buehler MMT-3 digital microhardness tester Lake Bluff, Illinois USA). A 50 gf load was used and the indenter with a dwell time of 30 s. The data were submitted to the test t Student at significance level of 5%. The mean values of degree of conversion for the polymer and metal light guide tip no were statistically different (p = 0.8389). The hardness mean values were no statistically significant different among the light guide tips (p = 0.6244), however, there was difference between top and bottom surfaces (p < 0.001). The results show that so much the polymer light tip as the metal light tip can be used for the photo-activation, probably for the low quality of the light guide tip metal.

Adsorption Behavior of 5-Fluorouracil on Au(111): An In Situ STM Study

The biological effects of chemical substitution of DNA bases triggered several investigations of their physicochemical properties This paper studies the adsorption behavior of a halogenated uracil, 5-fluorouracil (5FU). at the electrochemical interface of Au(111) and sulfuric acid solution. Upon modulation of the electric field across the interface, four distinct phases could be inferred by means of cyclic voltammetry (CV) At negative potentials relative to the SCE electrode, limited by the threshold of hydrogen evolution, no molecular species could be detected by scanning tunneling microscopy (STM) at the reconstructed Au(111)-(23 x root 3) surface, indicating that any physisorbed molecules are randomly distributed Incursion into more positive potentials increases the surface population but doer not form any two-dimensional (2D) physisorbed ordered structure Instead, we observed metastable structures that are only detectable. on surfaces with high defect density At sufficiently high positive potentials. limited by gold oxidation, the molecules are chemisorbed in a (3 x 2 root 3) ordered structure. with the aromatic ring perpendicular to the surface We report the densest chemisorbed monolayer for pyrimidine-derivative molecules (area per molecule 0 14 +/- 0 04 nm(2)). A comparison of the adsorption behavior of uracil derivatives has been made based on recent results of chemical substitution and solvent effects. We propose that pi-stacking is enhanced when halogens are incorporated in the uracil structure, in a similar fashion to what is observed in then crystal structure

Spectroscopic Investigation on the Formation of a Dinuclear Me(2)SO-Ru(2)-Mercaptopyridine Bridged Complex: [Ru(2)Cl(3)(mu-pyS)(mu-dmso)(dmso)(4)]center dot 2H(2)O

A dinuclear ruthenium(II) complex double-bridged by an N-aromatic ligand 2-mercaptopyridine (2-pyridinethiol or 2-pyridyl mercaptan) and a methyl sulfoxide (dmso) have been characterized by X-ray crystallography. The reported compound with formula [Ru(2)Cl(3) (mu-pyS)(mu-dmso)(dmso)(4)] center dot 2H(2)O, [C(15)H(36)Cl(3)NO(7)S(6)Ru(2)] (P2/c, a = 13.8175(2) angstrom, b = 10.5608(2) angstrom, c = 21.3544 (3) angstrom, beta = 106.090(1)degrees, V = 2,994.05(8) angstrom(3), Z = 4) represents a seven-membered ring system with both rutheniums in an octahedral geometry. All the hydrogen bonds (C-H-Cl) and the van der Waals contacts give rise to three-dimensional network in the structure and add stability to the dinuclear compound. To our knowledge, this is the first time that the formation of a dinuclear ruthenium(II) complex double-bridged by an N-aromatic ligand 2-mercaptopyridine and dmso have been reported. The study also provided valuable insight into bioinorganic chemistry as continuing efforts are being made to develop metal-based cancer chemotherapeutics. A major feature of this paper is the resolution of a double bridged ruthenium structure which contributes to a better understanding of ruthenium reactivity.

Structural and spectroscopic characterization of poly(styrene sulfonate) films doped with neodymium ions

This work reports the structural and spectroscopy characterization of poly(styrene sulfonate) (PSS) films doped with neodymium (Nd) ions. Nd-PSS films were processed using the acid of poly(styrene sulfonate) - H-PSS and neodymium nitrate - Nd(NO(3))(3); the maximum incorporation of Nd ions in the polymeric matrix was equal 19.3%. The absorption in the UV-Vis-NIR spectral region presents typical electronic transitions of Nd 3, ions, with well resolved peaks. The infrared spectra present the transition bands of PSS with characteristic line shape broadening, and the presence of vibrational modes of N-O groups in the range of 1400-720 cm(-1), prove the permanence of Nd(NO(3))(x), with x = 1, 2 and/or 3. in the H-PSS matrix. UV-Vis site selective photoluminescence data indicate that the incorporation of Nd 31 introduces a blue shift in PSS emission (325-800 nm), decreasing the interaction between adjacent PSS lateral groups (aromatic rings). Nd(3+) reabsorption and energy transfer effects between the PSS matrix and Nd(3+) were also observed. The IR emission of Nd-PSS films at 1076 rim ((4)F(3/2) -> (4)I(11/2)) present constant efficiency, independent on Nd(3+) concentration. The Judd-Ofelt theory was employed to analyze radiative properties. The excitation spectra prove the energy transfer between the polymeric matrix and Nd(3+). Complex impedance data was used to probe relaxation processes during the charge transport within the polymeric matrix. (C) 2008 Elsevier B.V. All rights reserved.

SBTX, a new toxic protein distinct from soyatoxin and other toxic soybean [Glycine max] proteins, and its inhibitory effect on Cercospora sojina growth

SBTX, a novel toxin from soybean, was purified by ammonium sulfate fractionation followed by chromatographic steps DEAE-Cellulose, CM-Sepharose and Superdex 200 HR fast-protein liquid chromatography (FPLC). Lethality of SBTX to mice (LD50 5.6 mg/kg) was used as parameter in the purification steps. SBTX is a 44-kDa basic glycoprotein composed of two polypeptide chains (27 and 17 kDa) linked by a disulfide bond. The N-terminal sequences of the 44 and 27 kDa chains were identical (ADPTFGFTPLGLSEKANLQIMKAYD), differing from that of 17 kDa (PNPKVFFDMTIGGQSAGRIVMEEYA). SBTX contains high levels of Glx, Ala, Asx, Gly and Lys and showed maximum absorption at 280 nm, epsilon(1 cm) (1%) of 6.3, and fluorescence emission in the 290-450nm range upon excitation at 280nm. The secondary structure content was 35% alpha-helix, 13% beta-strand and beta-sheet, 27% beta-turn, 25% unordered, and 1% aromatic residues. Immunological assays showed that SBTX was related to other toxic proteins, such as soyatoxin and canatoxin, and cross-reacted weekly with soybean trypsin inhibitor and agglutinin, but it was devoid of protease-inhibitory and hemagglutinating activities. The inhibitory effect of SBTX on growth of Cercospora sojina, fungus causing frogeye leaf spot in soybeans, was observed at 50 mu g/ml, concentration 112 times lesser than that found to be lethal to mice. This effect on phytopathogenic fungus is a potential attribute for the development of transgenic plants with enhanced resistance to pathogens. (c) 2007 Elsevier Ltd. All rights reserved.

Solid-state NMR characterization of a series of copolymers containing fluorene, phenylene and thiophene units

Fluorene and thiophene units are commonly used in polymeric materials for electro-optical applications. Due to differences in reactivity, the final composition of polymers containing these components often differs from that used in their preparation. This contribution describes the synthesis of PPV type terpolymers built by fluorene, phenylene and thiophene units and their quantification by CPMAS NMR. The similarity of the three aromatic co-monomers makes it difficult to separate the analytical responses that would allow quantification of each copolymer unit in the chain. In this sense, we show that the combination of dipolar dephased CPMAS with radiofrequency ramp and proper spectral treatment allows a good estimation and quantification of the copolymer constitution. (C) 2011 Elsevier Ltd. All rights reserved.

Role of cis-cis muconic acid in the catalysis of Pseudomonas putida chlorocatechol 1,2-dioxygenase

Chlorocatechol 1,2-dioxygenase (1,2-CCD) is a non-heme iron protein involved in the intradiol cleavage of aromatic compounds that are recalcitrant to biodegradation. In particular, 1,2-CCD catalyzes the conversion of catechol and its halogenated derivatives to cis-cis muconic acid. In this study we describe a series of experiments concerning the interaction of chlorocatechol 1,2-dioxygenase from Pseudomonas putida (Pp1,2-CCD) with cis-cis muconic acid. We used single-injection ITC to show that the reaction product inhibits enzyme kinetics. DSC and EPR measurements probed whether this was accomplished by a direct binding of the product to the enzyme active site. DSC shows that cis-cis muconic acid affects the thermal unfolding of the protein and allowed us to estimate a binding constant. Furthermore, EPR spectra of the Fe(III) center demonstrate that, upon product binding, a significant decrease in resonance intensity is observed, indicating that cis-cis muconic acid binds directly to the active site. Based on the increasing interest for understanding dioxygenases mechanism of action and, moreover, how to control such process, our data indicate that the product of the reaction does play a relevant role in the catalysis and should therefore be taken into account when one thinks about ways of regulating enzyme activity. (C) 2010 Elsevier B.V. All rights reserved.

Oxidation and nitration of ribonuclease and lysozyme by peroxynitrite and myeloperoxidase

In spite of the many studies on protein modifications by reactive species, knowledge about the products resulting from the oxidation of protein-aromatic residues, including protein-derived radicals and their stable products, remains limited. Here, we compared the oxidative modifications promoted by peroxynitrite and myeloperoxidase/hydrogen peroxide/nitrite in two model proteins, ribonuclease (6Tyr) and lysozyme (3Tyr/6Trp). The formation of protein-derived radicals and products was higher at pH 5.4 and 7.4 for myeloperoxidase and peroxynitrite, respectively. The main product was 3-nitro-Tyr for both proteins and oxidants. Lysozyme rendered similar yields of nitro-Trp, particularly when oxidized by peroxynitrite. Hydroxylated and dimerized products of Trp and Tyr were also produced, but in lower yields. Localization of the main modified residues indicates that peroxynitrite decomposes to radicals within the proteins behaving less specifically than myeloperoxidase. Nitrogen dioxide is emphasized as an important protein modifier. (C) 2009 Elsevier Inc. All rights reserved.

MPO Inhibitors Selected by Virtual Screening

The hemeprotein myeloperoxidase (MPO) participates in innate immune defense through its ability to generate potent microbicidal oxidants. However, these oxidants are also key mediators of the tissue damage associated with many inflammatory diseases. Thus, there is considerable interest in developing therapeutically useful MPO inhibitors. Here, we used structure-based drug design (SBDD) and ligand-based drug design (LBDD) to select for potentially new and selective MPO inhibitors. A pharmacophore model was developed based on the crystal structure of human MPO in complex with salicylhydroxamic acid (SHA), a known inhibitor of the enzyme. The pharmacophore model was used to screen the ZINC database for potential ligands, which were further filtered on the basis of their physical-chemical properties and docking score. The filtered compounds were visually inspected, and nine were purchased for experimental studies. Surprisingly, almost all of the selected compounds belonged to the aromatic hydrazide class, which had been previously described as MPO inhibitors. The compounds selected by virtual screening were shown to inhibit the chlorinating activity of MPO; the top four compounds displayed IC(50) values ranging from 1.0 to 2.8 mM. MPO inactivation by the most effective compound was shown to be irreversible. Overall, our results show that SBDD and LBDD may be useful for the rational development of new MPO inhibitors.

Salinity influences glutathione S-transferase activity and lipid peroxidation responses in the Crassostrea gigas oyster exposed to diesel oil

Biochemical responses in bivalve mollusks are commonly employed in environmental studies as biomarkers of aquatic contamination. The present study evaluated the possible influence of salinity (35, 25,15 and 9 ppt) in the biomarker responses of Crassostrea gigas oysters exposed to diesel at different nominal concentrations (0.01, 0.1 and 1 mLL(-1)) using a semi-static exposure system. Salinity alone did not resulted in major changes in the gill`s catalase activity (CAT), glutathione S-transferase activity (GST) and lipid peroxidation levels (measured as malondialdehyde. MDA), but influenced diesel related responses. At 25 ppt salinity, but not at the other salinity levels, oysters exposed to diesel showed a strikingly positive concentration-dependent GST response. At 25 ppt and 1 mLL(-1) diesel, the GST activity in the gills remained elevated, even after one week of depuration in clean water. The increased MDA levels in the oysters exposed to diesel comparing to control groups at 9, 15 and 35 ppt salinities suggest the occurrence of lipid peroxidation in those salinities, but not at 25 ppt salinity. The MDA quickly returned to basal levels after 24 h of depuration. CAT activity was unaltered by the treatments employed. High toxicity for 1 mLL(-1) diesel was observed only at 35 ppt salinity, but not in the other salinities. Results from this study strongly suggest that salinity influences the diesel related biomarker responses and toxicity in C. gigas, and that some of those responses remain altered even after depuration. (C) 2011 Elsevier B.V. All rights reserved.

Negishi cross-coupling of organotellurium compounds: synthesis of biaryls, aryl-, and diaryl acetylenes

A functional group tolerant palladium-catalyzed Negishi coupling of diaryl tellurides with organozinc has been developed. This methodology permits efficient preparation of biaryls, aryl acetylenes and diaryl acetylenes in moderate to good yields. A preliminary study to gain further insight into the reaction was performed using in situ ReactIR technology. (C) 2011 Elsevier Ltd. All rights reserved.

Determination of anthropogenic and biogenic compounds on atmospheric aerosol collected in urban, biomass burning and forest areas in Sao Paulo, Brazil

This study was conducted at three sites of different characteristics in Sao Paulo State Sao Paulo (SPA), Piracicaba (PRB) and Mate Atlantica Forest (MAT) PM(10), n-alkanes. pristane and phytane, PAHs, water-soluble ions and biomass burning tracers like levoglucosan and retene, were determined in quartz fiber filters. Samplings occurred on May 8th to August 8th, 2007 at the MAT site; on August 15th to 29th in 2007 and November 10th to 29th in 2008 at the PRB site and, March 13th to April 4th in 2007 and August 7th to 29th in 2008 at the SPA site Aliphatic compounds emitted biogenically were less abundant at the urban sites than at the forest site, and its distribution showed the influence of tropical vascular plants Air mass transport front biomass burning regions is likely to impact the sites with specific molecular markers The concentrations of all species were variable and dependent of seasonal changes In the most dry and polluted seasons, n-alkane and canon total concentrations were similar between the megacity and the biomass burning site PAHs and inorganic ion abundances were higher at Sao Paulo than Piracicaba, yet, the site influenced by biomass burning seems lobe the most impacted by the organic anion abundance in the atmosphere Pristane and phytane confirm the contamination by petroleum residues at urban sites, at the MAT site, biological activity and long range transport of pollutants might influence the levels of pristane (C) 2010 Elsevier B V All rights reserved

Experimental Evidence of the Occurrence of Intramolecular Electron Transfer in Catalyzed 1,2-Dioxetane Decomposition

The activation parameters for the thermal decomposition of 13 acridinium-substituted 1,2-dioxetanes, bearing an aromatic moiety, were determined and their chemiluminescence emission quantum yields estimated, utilizing in situ photosensitized 1,2-dioxetane generation and observation of its thermal decomposition kinetics, without isolation of these highly unstable cyclic peroxides. Decomposition rate constants show linear free-energy correlation for electron-withdrawing substituents, with a Hammett reaction constant of rho = 1.3 +/- 0.1, indicating the occurrence of an intramolecular electron transfer from the acridinium moiety to the 1,2-dioxetane ring, as postulated by the intramolecular chemically initiated electron exchange luminescence (CIEEL) mechanism. Emission quantum yield behavior can also be rationalized on the basis of the intramolecular CIEEL mechanism, additionally evidencing its occurrence in this transformation. Both relations constitute the first experimental evidence for the occurrence of the postulated intramolecular electron transfer in the catalyzed and induced decomposition of properly substituted 1,2-dioxetanes.

Improved Prediction of Hydrocarbon Flash Points from Boiling Point Data

Flash points (T(FP)) of hydrocarbons are calculated from their flash point numbers, N(FP), with the relationship T(FP) (K) = 23.369N(FP)(2/3) + 20.010N(FP)(1/3) + 31.901 In turn, the N(FP) values can be predicted from experimental boiling point numbers (Y(BP)) and molecular structure with the equation N(FP) = 0.987 Y(BP) + 0.176D + 0.687T + 0.712B - 0.176 where D is the number of olefinic double bonds in the structure, T is the number of triple bonds, and B is the number of aromatic rings. For a data set consisting of 300 diverse hydrocarbons, the average absolute deviation between the literature and predicted flash points was 2.9 K.