Cinética de hidrólise de GPTS sob estimulação ultrassônica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comparación de la conductancia hidráulica dentinaria, de acuerdo al tiempo de aplicación de desensibilizantes con base de oxalatos

ABSTRACT. Introduction: an in vitro model was used to measure the hydraulic conductance in human dentin discs treated with oxalic acid for 15, 30 or 60 s maintaining the occlusive effect and measuring 7 and 14 days after application. Methods: 45 dentin discs measuring 1 mm thick were obtained from human third molars which were free of caries and in no occlusion; the samples were obtained from patients aged 16 to 30 years. Discs were sorted out into three study groups (n = 15) depending on the time of application of a commercial solution of oxalate-based dentin desensitizer (DD) (BisBlock®) which contains ˂ 5% oxalic acid of 1.5-1.8 pH: in group A the agent was applied for 15 s, in group B it was applied for 30 s, and in group C for 60 s. The hydraulic conductance of each disc was calculated after acid etching, which corresponds to the maximum permeability of discs (100%) after immediate application of oxalic acid, as well as seven and fourteen days of storage in saline solution. The statistical analysis was done with ANOVA test and post-hoc Games-Howell test. Results: 35,46 ± 23.41% in Group A, 36.34 ± 15.88% in Group B and 24.99 ± 14.99% in Group C, showing that the use of DD for 15, 30 or 60 s decreased permeability in a statistically significant manner (p <0.05). Conclusions: DD was effective in reducing hydraulic conductance regardless of application time, but this reduction was temporary only, since after seven days permeability returns to values close to those of baseline.

Efecto del ácido oxálico bajo restauraciones cervicales en dientes con hipersensibilidad: ensayo clínico randomizado controlado doble ciego

To evaluate the effect of oxalic acid in cervical hypersensitivity, used under two different resin restorations one based on methacrylate and another based on silorane. Methods: 19 patients with “LCNC with hypersensitivity” were distributed into 4 groups according to treatment: G1 (n = 31): 0.5% oxalic acid (Desenssiv, SSWhite) + Z250 (3MESPE), G2 (n = 31): 0.5% oxalic acid + Filtek Silorane - P90 (3MESPE), G3 (n = 30): Distilled water + Z250; G4 (n = 30): Distilled water + Filtek Silorane - P90. Two clinical calibrated (kappa> 0.75) evaluated the sensitivity of the teeth: Before treatment, at 30, 60 and 90 days post-treatment (VAS). Results: The 4 groups at 30, 60 and 90 days reduced HS compared with the baseline (p <0.05). G1 and G2 showed less HS than G3 and G4 (p <0.05). Conclusion: The 4 restorative procedures significantly reduce the hypersensitivity, 30, 60 and 90 days compared to the baseline.

Orange pectin mediated growth and stability of aqueous gold and silver nanocolloids

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

The role of Ce(III) in BZ oscillating reactions

Herein we present results on the oscillatory dynamics in the bromate-oxalic acid-acetone-Ce(III)/Ce(IV) system in batch and also in a CSTR. We show that Ce(III) is the necessary reactant to allow the emergence of oscillations. In batch, oscillations occur with Ce(III) and also with Ce(IV), but no induction period is observed with Ce(III). In a CSTR, no oscillations were found using a freshly prepared Ce(IV), but only when the cerium-containing solution was aged, allowing partial conversion of Ce(IV) to Ce(III) by reaction with acetone. (C) 2012 Elsevier B. V. All rights reserved.

The chemiluminescent peroxyoxalate system: state of the art almost 50 years from its discovery

Almost fifty years after the discovery of the peroxyoxalate reaction by E. A. Chandross in the early nineteen sixties, this review article intends to give a general overview on mechanistic aspects of this system and to describe the principles of its analytical application. After a short general introduction on the principles of chemiluminescence and the history of peroxyoxalate discovery, mechanistic aspects of high-energy intermediate formation, its structure and its reaction with an activator in the peroxyoxalate system are discussed. Finally, analytical applications of peroxyoxalate chemiluminescence are exemplified using representative recent examples, including oxalic acid detection in biological samples.

USE OF ADDITIVES IN THE WOOD BIODEGRADATION BY THE FUNGUS Ceriporiopsis subvermispora: EFFECT IN THE MANGANESE PEROXIDASE-DEPENDENT LIPID PEROXIDATION

USE OF ADDITIVES IN THE WOOD BIODEGRADATION BY THE FUNGUS Ceriporiopsis subvermispora: EFFECT IN THE MANGANESE PEROXIDASE-DEPENDENT LIPID PEROXIDATION. Ceriporiopsis subvermispora is a selective fungus in the wood delignification and the most promising in biopulping. Through the lipid peroxidation initiated by manganese peroxidase (MnP), free radicals can be generated, which can act in the degradation of lignin nonphenolic structures. This work evaluated the prooxidant activity (based in lipid peroxidation) of enzymatic extracts from wood biodegradation by this fungus in cultures containing exogenous calcium, oxalic acid or soybean oil. It was observed that MnP significant activity is required to promote lipid peroxidation and wood delignification. Positive correlation between prooxidant activity x MnP was observed up to 300 IU kg(-1) of wood.

Effect of aqueous extracts from Ceriporiopsis subvermispora-biotreated wood on the decolorization of Azure B by Fenton-like reactions

Aqueous extracts from wood biotreated with the white-rot fungus Ceriporiopsis subvermispora were evaluated for their Fe3+- and Cu2+-reducing activities and their anti- or prooxidant properties in Fenton-like reactions to decolorize the recalcitrant dye Azure B. The decolorization of Azure B was strongly inhibited in the presence of 10% (v/v) wood extracts. Only 0.1% (v/v)-diluted extracts provided some enhancement of the Azure B decolorization. The iron-containing reactions decolorized more Azure B and consumed substantially more H2O2 than the reactions containing copper. This study demonstrates that water-soluble wood phenols exert anti- or prooxidant effects that depend on their concentration in the reactions and on the type of cation, Fe3+ or Cu2+, used to convert H2O2 to OH radicals. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.

Uso de aditivos na biodegradação de madeira pelo fungo Ceriporiopsis subvermispora: efeito na peroxidação de lipídios dependente de manganês-peroxidase

Ceriporiopsis subvermispora is a selective fungus in the wood delignification and the most promising in biopulping. Through the lipid peroxidation initiated by manganese peroxidase (MnP), free radicals can be generated, which can act in the degradation of lignin nonphenolic structures. This work evaluated the prooxidant activity (based in lipid peroxidation) of enzymatic extracts from wood biodegradation by this fungus in cultures containing exogenous calcium, oxalic acid or soybean oil. It was observed that MnP significant activity is required to promote lipid peroxidation and wood delignification. Positive correlation between prooxidant activity x MnP was observed up to 300 IU kg-1 of wood.

Cocristalli di acidi dicarbossilici: sintesi, caratterizzazione e stabilità allo stato solido

It is well-known that crystalline materials obtain their fundamental physical properties from the molecular arrangement within the solid, and altering the placement and or interactions between these molecules can impact the properties of the particular solid. Solid state chemistry looks at an attempt to alter the chemical and physical solid-state properties of APIs through many different strategies as the formation of salts, polymorphs, hydrates, solvates, and cocrystals. The final aim of this work is to study the chemical and physical propriety of new crystal structures. The work consists of three parts. The first is the cocrystallization of α,ω-alkanedicarboxylics acids with pirimidine. Single-crystal X-ray diffraction analysis of this adduct have been carried out at RT, 150 and 200 K. The cocrystals show an alteration of their melting point similar to pure acids. The two significant deviations are for the cocrystals with succinico and glutarico acids. The second object of work is the structure determination of β polymorph undecandioic acids. In literature is known the other polymorph α. We observed that the thermodynamic relation for this dimorphics system is monotropic. In the third part we synthesized and analyzed the stability of four new salts of serine and oxalic acid. This project highlights the advantage of the solid state synthesis.

Cross-Talk tra Bifidobacterium e intestino umano: impatto sulle attività health promoting

Bifidobacteria constitute up to 3% of the total microbiota and represent one of the most important healthpromoting bacterial groups of the human intestinal microflora. The presence of Bifidobacterium in the human gastrointestinal tract has been directly related to several health-promoting activities; however, to date, no information about the specific mechanisms of interaction with the host is available. The first health-promoting activities studied in these job was the oxalate-degrading activity. Oxalic acid occurs extensively in nature and plays diverse roles, especially in pathological processes. Due to its highly oxidizing effects, hyper absorption or abnormal synthesis of oxalate can cause serious acute disorders in mammals and be lethal in extreme cases. Intestinal oxalate-degrading bacteria could therefore be pivotal in maintaining oxalate homeostasis, reducing the risk of kidney stone development. In this study, the oxalate-degrading activity of 14 bifidobacterial strains was measured by a capillary electrophoresis technique. The oxc gene, encoding oxalyl-CoA decarboxylase, a key enzyme in oxalate catabolism, was isolated by probing a genomic library of B. animalis subsp. lactis BI07, which was one of the most active strains in the preliminary screening. The genetic and transcriptional organization of oxc flanking regions was determined, unravelling the presence of other two independently transcribed open reading frames, potentially responsible for B. animalis subsp. lactis ability to degrade oxalate. Transcriptional analysis, using real-time quantitative reverse transcription PCR, revealed that these genes were highly induced in cells first adapted to subinhibitory concentrations of oxalate and then exposed to pH 4.5. Acidic conditions were also a prerequisite for a significant oxalate degradation rate, which dramatically increased in oxalate pre-adapted cells, as demonstrated in fermentation experiments with different pH-controlled batch cultures. These findings provide new insights in the characterization of oxalate-degrading probiotic bacteria and may support the use of B. animalis subsp. lactis as a promising adjunct for the prophylaxis and management of oxalate-related kidney disease. In order to provide some insight into the molecular mechanisms involved in the interaction with the host, in the second part of the job, we investigated whether Bifidobacterium was able to capture human plasminogen on the cell surface. The binding of human plasminogen to Bifidobacterium was dependent on lysine residues of surface protein receptors. By using a proteomic approach, we identified six putative plasminogen-binding proteins in the cell wall fraction of three strain of Bifidobacterium. The data suggest that plasminogen binding to Bifidobactrium is due to the concerted action of a number of proteins located on the bacterial cell surface, some of which are highly conserved cytoplasmic proteins which have other essential cellular functions. Our findings represent a step forward in understanding the mechanisms involved in the Bifidobacterium-host interaction. In these job w studied a new approach based on to MALDI-TOF MS to measure the interaction between entire bacterial cells and host molecular target. MALDI-TOF (Matrix Assisted Laser Desorption Ionization-Time of Flight)—mass spectrometry has been applied, for the first time, in the investigation of whole Bifidobacterium cells-host target proteins interaction. In particular, by means of this technique, a dose dependent human plasminogen-binding activity has been shown for Bifidobacterium. The involvement of lysine binding sites on the bacterial cell surface has been proved. The obtained result was found to be consistent with that from well-established standard methodologies, thus the proposed MALDI-TOF approach has the potential to enter as a fast alternative method in the field of biorecognition studies involving in bacterial cells and proteins of human origin.

Die 18 F-Fluorierung verschiedener Aminosäuren als Tracer für die Tumor-Diagnostik mittels Positronen-Emissions-Tomographie

Die Zielsetzung dieser Arbeit war die Synthese und Markierung, sowie die in vitro- und in vivo-Evaluierung zweier markierter Aminosäure. Es wurden die PET-Tumor-Tracer C1-(2-[18F]Fluoreth- ylamino)-asparagin und S-2-Amino-4-[18F]fluor-butansäure synthetisiert. Die Markierung zum C1-(2-[18F]Fluorethylamino)-asparagin wurde mit 2-[18F]Fluorethylamin als Precursor durchgeführt. Ausgehend von N,N-Dibenzyl-(2-bromethyl)-amin wurde zunächst N,N-Dibenzyl-(2-[18F]fluorethyl)-amin in einer nukleophilen Substiution mit [18F]Fluorid in Acetonitril bei 80 °C mit einer Reaktionsdauer von 5 min dargestellt. Zur Abtrennung überschüssigen [18F]Fluorids wurde das Roh-Produkt auf einer Sep-Pak Plus Kartusche (C18) fixiert und mit Acetonitril eluiert. Die Abspaltung der Benzyl-Schutzgruppen erfolgte durch die Zugabe von Pd/C zu dem eluierten N,N-Dibenzyl-(2-[18F]fluorethyl)-amin und Behandelung der Lösung im leichten Wasserstoffstrom. Im finalen Aufreinigungsschritt wird der Katalysator Pd/C mittels eines Membranfilters abgetrennt. Das 2-[18F]Fluorethylamin wird im Sauren in das Amino-Salz überführt und im Vakuum vom Lösungsmittel befreit. Die Markierung zum C1-(2-[18F]Fluorethylamino)-asparagin wurde in DMF durchgeführt. Die höchsten Ausbeuten werden nach 4 min bei 60 °C erhalten. Die Abspaltung der Schutzgruppe erfolgt durch Trifluoressigsäure bei Raumtemperatur in 8 min. Die Aufreinigung des C1-(2-[18F]Fluorethylamino)-asparagin mittels HPLC und Festphasenextraktion liegt das Produkt in einer isotonischne isotonischen Kochsalzlösung vor. Die in vitro-Versuche wurden mit C1-(2-[18F]Fluorethylamino)-asparagin an 5 verschiedenen Zelllinen durchgeführt, 3 Plattenepitele und 2 Melanome. Hierbei konnte eine erhöhte Akkumulation von C1 -(2-[18F]Fluorethylamino)-asparagin beobachtet werden, die innerhalb von 20 min einen konstanten Wert erreicht. Ein Blockade-Experiment zeigte, dass sich die Aufnahme von C1 -(2-[18F]Fluorethylamino)-asparagin durch gesättinge Asparagin-Lösung bei den Plattenepitelen gar nicht und bei den Melanomen nur leicht vermindern ließ. Da die Aufnahme von C1-(2-[18F]Fluorethylamino)-asparagin in die Zellen höher war als bei FDG bei dem gleichen Versuchsaufbau, wurden in vivo-Versuche angesetzt. Die in vivo-Versuche an Sprague Dawley Ratten mit C1-(2-[18 F]Fluorethylamino)-asparagin zeigten keine messbare Anreicherung von C1-(2-[18F]Fluorethylamino)-asparagin in Tumoren. Fast die komplette Aktivität wurde in der Niere und Blase wiedergefunden. Die Synthese von S-2-Amino-4-[18F]fluor-butansäure wurde über stereodirigierende Auxilliare realisiert. Dazu wurden die geeignetsten Auxillare ausgewählt und auf ihre Eignung verglichen. Der Vergleich der stereodirigierenden Auxilare zeigte, dass das (1R,2R,5R)-2-Hydroxy-2,6,6-trimethyl- bicyclo[3.1.1]hept-3-ylidenamino)-essigsäure tert.-butylester (Laue-Auxillar) am geeignetesten ist. Die 18F-Markierung von S-2-Amino-4-[18F]fluor-butansäure wurde so optimiert, dass eine möglichst hohe stereochemische Reinheit des Produktes erzielt wird. Die optische Reinheit von S-2-Amino-4-[18 F]fluor-butansäure wurde mit > 93 % ee berechnet. Die Synthese des Markierungsvorläufers wurde ausgehend vom Laue-Auxilliar aufgebaut. Als Abgangsgruppe hat sich die Tosylgruppe besonders bewährt. Sie lässt sich unter besonders schonenden Bedingungen in den säurelabilen (1R,2R,5R)-4-Hydroxy-2-(2-hydroxy-2,6,6-trimethyl-bi- cyclo[3.1.1]hept-3-ylidenamino) butansäure tert.-butylester einführen. Bei der 18F-Markierung von S-2-Amino-4-[18F]fluor-butansäure mittels n.c.a. [18F]Fluorid hat sich die Wahl des Basensystems als besonders wichtig erwiesen. Die maximale Ausbeuten von 55% wurde mit Oxalat als Basensystem in Acetonitril bei 80 °C und einer Reaktionszeit von 15 min erzielen. Die Abspaltung der Schutzgruppen und die Abtrennung des Produktes wird in mehreren Schritten durchgeführt einschließlich einer HPLC-Abtrennung. Es wird nach 150 min Synthesedauer das gereinigte S-2-Amino-4-[18F]fluor-butansäure in isotonischer Kochsalzlösung mit einer Ausbeute von > 10 % RCA erhalten. Bei in vivo-Versuchen an Sprague Dawley Ratten reicherte sich der Hauptteil der Aktivität in der Niere an und nur weniger als ein halbes Prozent der applizierten Aktivität fand sich in den Tumoren wieder. Nach 10 min wurde ein maximaler Wert erreicht, der sich bis zum Ende der Messung nicht verändert. Das Verhältnis von Tumoraktivität zu unspezifisch-gebundener Aktivität betrug 2,2. Damit liegt das Verhältnis im Bereich der meisten klinisch eingesetzten PET-Tumor-Tracer wie dem des O-(2-[18F]Fluorethyl)-L-tyrosin mit 1,5.

Seasonal variation and sources of low molecular weight organic acids in precipitation in the rural area of Anshun

Low mol. wt. (LMW) org. acids are important and ubiquitous chem. constituents in the atm. A comprehensive study of the chem. compn. of pptn. was carried out from June 2007 to June 2008 at a rural site in Anshun, in the west of Guizhou Province, China. During this period, 118 rainwater samples were collected and the main LMW carboxylic acids were detd. using ion chromatog. The av. pH of rainwater was 4.89 which is a typical acidic value. The most abundant carboxylic acids were formic acid (vol. wt. mean concn.: 8.77 μmol L-1) and acetic acid (6.90 μmol L-1), followed by oxalic acid (2.05 μmol L-1). The seasonal variation of concns. and wet deposition fluxes of org. acids indicated that direct vegetation emissions were the main sources of the org. acids. Highest concns. were obsd. in winter and were ascribed to the low winter rainfall and the contribution of other air pollution sources northeast of the study area. The ratio of formic and acetic acids in the pptn. ([F/A]T) was proposed as an indicator of pollution source. This suggested that the pollution resulted from direct emissions from natural or anthropogenic sources. Comparison with acid pptn. in other urban and rural areas in Guizhou showed that there was a decreasing contribution of LMW org. acids to free acidity and all anions in rainwater from urban to remote rural areas. Consequently, it is necessary to control emissions of org. acids to reduce the frequency of acid rain, esp. in rural and remote areas. [on SciFinder(R)]

EVOLUTION OF SELECTED ISOPRENE OXIDATION PRODUCTS IN DARK AQUEOUS AMMONIUM SULFATE

The aqueous phase processing of glyoxylic acid, pyruvic acid, oxalic acid and methylglyoxal was studied simulating dark and radical free atmospheric aqueous aerosol. A novel observation of the cleavage of a carbon-carbon bond in pyruvic acid and glyoxylic acid leading to their decarboxylation was made in the presence of ammonium salts but no decarboxylation was observed from oxalic acid. The empirical rate constants for decarboxylation were determined. The structure of the acid, ionic environment of solution and concentration of species found to affect the decarboxylation process. A tentative set of reaction mechanisms was proposed involving nucleophilic attack by ammonia on the carbonyl carbon leading to fragmentation of the carbon-carbon bond between the carbonyl and carboxyl carbons. Whereas, the formation of high molecular weight organic species was observed in the case of methylglyoxal. The elemental compositions of the species were determined. It was concluded that, additional pathways that are not currently known likely contribute to aqueous phase processing leading to high molecular weight organic species. Under similar conditions in atmospheric aerosol, the aqueous phase processing will markedly impact the physicochemical properties of aerosol.

Seasonal variation of high-molecular-weight compounds in the water-soluble fraction of organic urban aerosols

Aerosol samples were collected in Zurich, Switzerland, at an urban background site and were analyzed with size exclusion chromatography (SEC) and laser/desorption ionization mass spectrometry (LDI-MS) for water-soluble organic compounds with high molecular weight. Daily samples were collected during two campaigns in winter and summer, for 1 month each. The concentration of high-molecular-weight compounds (humic-like substances (HULIS)) was between 0.4 and 4 μg/m3 in winter and summer. The most intense signals in the LDI-MS mass spectra were measured between m/z150 and 500, comparing well with the mode of the two main high mass peaks determined with SEC corresponding to masses between 200 and 600 Da. For the maximum molecular weight, however, different results were obtained by the two techniques: whereas a maximum molecular weight between 1300 and 3300 Da was found with SEC, hardly any peaks above m/z700 were measured with LDI-MS. During summer the maximum molecular weight of HULIS (determined with SEC) correlates positively with several parameters such as ozone and increased temperature indicative of enhanced atmospheric photo-oxidation. The HULIS concentration also correlates positively with the oxalic acid concentration in the particles. This suggests that HULIS are generated by secondary processes in summer. The lack of such correlations during winter suggests that other sources and processes might be important during colder seasons.