Electrochemical Oxidation of Hydroxylamine on Gold in Aqueous Acidic Electrolytes: An in Situ SERS Investigation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The Oxidation of Hydroxylamine on Gold Electrodes in Mildly Acidic Aqueous Electrolytes: Electrochemical and In Situ Differential Reflectance Studies

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

GENETIC INTERRELATIONSHIPS OF PROTEOLYTIC CLOSTRIDIUM-BOTULINUM TYPE-A, TYPE-B, AND TYPE-F AND OTHER MEMBERS OF THE CLOSTRIDIUM-BOTULINUM COMPLEX AS REVEALED BY SMALL-SUBUNIT RIBOSOMAL-RNA GENE-SEQUENCES

The phylogenetic interrelationships of members of the Clostridium botulinum complex of species was investigated by direct sequencing of their 16S rRNA genes. Comparative analysis of the 16S rRNA sequences demonstrated the presence of four phylogenetically distinct lineages corresponding to: i) proteolytic C. botulinum types Al B, and F, and C. sporogenes, ii) saccharolytic types B, E and F, iii) types C and D and C. novyi type A, and iv) type G and C. subterminale. The phylogenetic groupings obtained from the 16S rRNA were in complete agreement with the four divisions recognised within the 'species complex' on the basis of phenotypic criteria.

Correlation between acidic ninhydrin and HPLC methods to evaluate fraudulent addition of whey in milk

The acidic ninhydrin spectrophotometric method (ANSM) for quantitative determination of free and bound sialic acid of milk glycoprotein has been proved to be fast and efficient for routine detection of fraudulent addition of rennet whey to fluid milk. In this research the ANSM was compared with the high performance liquid chromatography (HPLC) method, internationally recommended for caseinomacropeptide (CMP) determination, which besides its high accuracy is more sophisticated and requires trained personnel. For several sample conditions (raw milk and milk with variable added amounts of rennet cheese whey), the methods showed an excellent linear correlation, with r = 0.981 when milk was deproteinized with a 120 g.L-1 final concentration of trichloroacetic acid (TCA) concentration. The best correlations could be seen with final concentrations of 100 g.L-1 and 80 g.L-1 TCA; respectively, r = 0.992 and 0.993.

Chromotropic acid-formaldehyde reaction in strongly acidic media. The role of dissolved oxygen and replacement of concentrated sulphuric acid

The procedure for formaldehyde analysis recommended by the National Institute for Occupational Safety and Health (NIOSH) is the Chromotropic acid spectrophotometric method, which is the one that uses concentrated sulphuric acid. In the present study the oxidation step associated with the aforementioned method for formaldehyde determination was investigated. Experimental evidence has been obtained indicating that when concentrated H2SO4 (18 mol l(-1)) is used (as in the NIOSH procedure) that acid is the oxidizing agent. on the other hand, oxidation through dissolved oxygen takes place when concentrated H2SO4 is replaced by concentrated hydrochloric (12 mol l(-1)) and phosphoric (14.7 mol l(-1)) acids as well as by diluted H2SO4 (9.4 mol l(-1)). Based on investigations concerning the oxidation step, a modified procedure was devised, in which the use of the potentially hazardous and corrosive concentrated H2SO4 was eliminated and advantageously replaced by a less harmful mixture of HCl and H2O2. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Neodymium biosorption from acidic solutions in batch system

Biosorption of neodymium in batch experiments took similar to 2 h to achieve the equilibrium biosorbent-metal for all microorganisms tested. The best biosorption coefficient at a constant pH value of 1.5 was obtained using the microalgae Monoraphidium sp. (1521 mg g(-1) cell), followed by Bakers' yeast (313 mg g(-1) cell), Penicillium sp. (178 mg g(-1) cell), and activated carbon (61 mg g(-1) cell). When compared to the biosorption of other metals, these results pointed out to the application of biosorption in neodymium recovery from acidic solutions. (C) 2000 Elsevier B.V. Ltd. All rights reserved.

Tuning the acidic properties of aluminas via sol-gel synthesis: New findings on the active site of alumina-catalyzed epoxidation with hydrogen peroxide

This study answers several pending questions about alumina-catalyzed epoxidation with aqueous 70 wt% H2O2. To evaluate the effect of the water-to-aluminum tri-sec-butoxide molar ratio, this was systematically changed from 1 to 24. The xerogels were calcined at 450 degrees C and gave different gamma-Al2O3's with distinct textural and acidic properties. A combination of Al-27 MAS NMR and TPD-NH3 results of calcined aluminas allowed us to assign the type la. Al-OH sites as the catalytic sites for epoxidation. The type Ib Al-OH sites have no function in catalytic epoxidation, because ethyl acetate poisons these sites. The strong acid sites of types IIa, IIb, and III Al-OH groups are responsible for the undesired H2O2 decomposition and decreased oxidant selectivity. (c) 2006 Elsevier B.V. All rights reserved.

In vitro evaluation of the effectiveness of acidic fluoride dentifrices

This study evaluated the effectiveness of acidic low-fluoride dentifrices compared to conventional neutral dentifrices. Enamel blocks were submitted to pH cycling and treatment with slurries of dentifrices containing 0, 275, 412, 550 and 1,100 mu g F/g (pH 4.5 or 7.0), and also a commercial dentifrice (1,100 mu g F/g) and a commercial children's dentifrice (500 mu g F/ g). Variations in surface microhardness and in the mineral content in enamel after pH cycling were calculated. Enamel blocks treated with acidic dentifrices exhibited less mineral loss compared to neutral dentifrices (ANOVA; p < 0.05). The acidic dentifrices with 412 and 550 mu g F/g had the same effectiveness as the neutral 1,100-mu g F/g dentifrice and commercial 1,100-mu g F/g dentifrice. Copyright (c) 2007 S. Karger AG, Basel

Isolation, characterization and biological activity of acidic phospholipase A(2) isoforms from Bothrops jararacussu snake venom

Acidic phospholipase A(2) (PLA(2)) isoforms in snake venoms, particularly those from Bothrops jararacussu, have not been characterized. This article reports the isolation and partial biochemical, functional and structural characterization of four acidic PLA(2)s (designated SIIISPIIA, SIIISPIIB, SIIISPIIIA and SIIISPIIIB) from this venom. The single chain purified proteins contained 122 amino acid residues and seven disulfide bonds with approximate molecular masses of 15 kDa and isoelectric points of 5.3. The respective N-terminal sequences were: SIIISPIIA-SLWQFGKMIDYVMGEEGAKS; SIIISPIIB-SLWQFGKMIFYTGKNEPVLS; SIIISPIIIA-SLWQFGKMILYVMGGEGVKQ and SIIISPIIIB-SLWQFGKMIFYEMTGEGVL. Crystals of the acidic protein SIIISPIIIB diffracted beyond 1.8 Angstrom resolution. These crystals are monoclinic with unit cell dimensions of a = 40.1 Angstrom, b = 54.2 Angstrom and c = 90.7 Angstrom. The crystal structure has been refined to a crystallographic residual of 16.1% (R-free = 22.9%). Specific catalytic activity (U/mg) of the isolated acidic PLA(2)s were SIIISPIIA = 290.3 U/mg; SIIISPIIB = 279.0 U/mg; SIIISPIIIA = 270.7 U/mg and SIIISPIIIB = 96.5 U/mg. Although their myotoxic activity was low, SIIISPIIA, SIIISPIIIB and SIIISPIIIA showed significant anticoagulant activity. However, there was no indirect hemolytic activity. SIIISPIIIB revealed no anticoagulant, but presented indirect hemolytic activity. With the exception of SIIISPIIIB, which inhibited platelet aggregation, all the others were capable of inducing time-independent edema. Chemical modification with 4-bromophenacyl bromide did not inhibit the induction of edema, but did suppress other activities. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

Upregulation of gp91(phox) Subunit of NAD(P)H Oxidase Contributes to Erectile Dysfunction Caused by Long-term Nitric Oxide Inhibition in Rats: Reversion by Regular Physical Training

OBJECTIVES To test the hypothesis that glyco protein 91phox (gp91(phox)) subunit of nicotinamide adenine dinucleotide phosphate [NAD(P) H] oxidase is a fundamental target for physical activity to ameliorate erectile dysfunction (ED). Vascular risk factors are reported to contribute to ED. Regular physical exercise prevents cardiovascular diseases by increasing nitric oxide (NO) production and/or decreasing NO inactivation.METHODS Male Wistar rats received the NO synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) for 4 weeks, after which animals were submitted to a run training program for another 4 weeks. Erectile functions were evaluated by in vitro cavernosal relaxations and intracavernous pressure measurements. Expressions of gp91(phox) subunit and neuronal nitric oxidase synthase in erectile tissue, as well as superoxide dismutase activity and nitrite/nitrate (NO(x)) levels were determined.RESULTS The in vitro acetylcholine-and electrical field stimulation-induced cavernosal relaxations, as well as the increases in intracavernous pressure were markedly reduced in sedentary rats treated with L-NAME. Run training significantly restored the impaired cavernosal relaxations. No alterations in the neuronal nitric oxidase synthase protein expression (and its variant penile neuronal nitric oxidase synthase) were detected. A reduction of NO(x) levels and superoxide dismutase activity was observed in L-NAME-treated animals, which was significantly reversed by physical training. Gene expression of subunit gp91(phox) was enhanced by approximately 2-fold in erectile tissue of L-NAME-treated rats, and that was restored to basal levels by run training.CONCLUSIONS Our study shows that ED seen after long-term L-NAME treatment is associated with gp91(phox) subunit upregulation and decreased NO bioavailability. Exercise training reverses the increased oxidative stress in NO-deficient rats, ameliorating the ED. UROLOGY 75: 961-967, 2010. (C) 2009 Elsevier B.V.

The significance of root growth on cotton nutrition in an acidic low-P soil

Toxic levels of Al and low availability of Ca have been shown to decrease root growth, which can also be affected by P availability. In the current experiment, initial plant growth and nutrition of cotton (Gossypium hirsutum var. Latifolia) were studied as related to its root growth in response to phosphorus and lime application. The experiment was conducted in Botucatu, Sao Paulo, Brazil, in pots containing a Dark Red Latosol (Acrortox, 20% clay, 72% sand). Lime was applied at 0.56, 1.12 and 1.68 g kg -1 and phosphorus was applied at 50, 100 and 150 mg kg -1. Two cotton (cv. IAC 22) plants were grown per pot for up to 42 days after plant emergence. There was no effect of liming on shoot dry weight, root dry matter yield, root surface and length, but root diameter was decreased with the increase in soil Ca. Shoot dry weight, as well as root length, surface and dry weight were increased with soil P levels up to 83 mg kg -1. Phosphorus concentration in the shoots was increased from 1.6 to 3.0 g kg -1 when soil P was increased from 14 to 34 mg kg -1. No further increases in P concentration were observed with higher P rates. The shoot/root ratio was also increased with P application as well as the amount of nutrients absorbed per unit of root surface. In low soil P soils the transport of the nutrient to the cotton root surface limits P uptake. In this case an increase in root growth rate due to P fertilisation does not compensate for the low P diffusion in the soil.

Conserved sequences in the β subunit of archaeal and eukaryal translation initiation factor 2 (elF2), absent from elF5, mediate interaction with elF2γ

The eukaryotic translation initiation factor 2 (eIF2) binds the methionyl-initiator tRNA in a GTP-dependent mode. This complex associates with the 40 S ribosomal particle, which then, with the aid of other factors, binds to the 5' end of the mRNA and migrates to the first AUG codon, where eIF5 promotes GTP hydrolysis, followed by the formation of the 80 S ribosome. Here we provide a comparative sequence analysis of the β subunit of eIF2 and its archaeal counterpart (aIF2β). aIF2β differs from eIF2β in not possessing an N-terminal extension implicated in binding RNA, eIF5 and eIF2B. The remaining sequences are highly conserved, and are shared with eIF5. Previously isolated mutations in the yeast eIF2β, which allow initiation of translation at UUG codons due to the uncovering of an intrinsic GTPase activity in eIF2, involve residues that are conserved in aIF2β, but not in eIF5. We show that the sequence of eIF2B homologous to aIF2β is sufficient for binding eIF2γ, the only subunit with which it interacts, and comprises, at the most, 78 residues, eIF5 does not interact with eIF2γ, despite its similarity with eIF2β, probably because of a gap in homology in this region. These observations have implications for the evolution of the mechanism of translation initiation.

Two short peptides including segments of subunit A of Escherichia coli DNA gyrase as potential probes to evaluate the antibacterial activity of quinolones

Quinolones constitute a family of compounds with a potent antibiotic activity. The enzyme DNA gyrase, responsible for the replication and transcription processes in DNA of bacteria, is involved in the mechanism of action of these drugs. In this sense, it is believed that quinolones stabilize the so-called 'cleavable complex' formed by DNA and gyrase, but the whole process is still far from being understood at the molecular level. This information is crucial in order to design new biological active products. As an approach to the problem, we have designed and synthesized low molecular weight peptide mimics of DNA gyrase. These peptides correspond to sequences of the subunit A of the enzyme from Escherichia coli, that include the quinolone resistance-determining region (positions 75-92) and a segment containing the catalytic Tyr-122 (positions 116-130). The peptide mimic of the non-mutated enzyme binds to ciprofloxin (CFX) only when DNA and Mg2+ were present (Kd = 1.6 × 10 -6 m), a result previously found with DNA gyrase. On the other hand, binding was reduced when mutations of Ser-83 to Leu-83 and Asp-87 to Asn-87 were introduced, a double change previously found in the subunit A of DNA gyrase from several CFX-resistant clinical isolates of E. coli. These results suggest that synthetic peptides designed in a similar way to that described here can be used as mimics of gyrases (topoisomerases) in order to study the binding of the quinolone to the enzyme-DNA complex as well as the mechanism of action of these antibiotics. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd.

Short Communication: In vitro evaluation of the abrasiveness of acidic dentifrices.

AIM: This in vitro study evaluated the abrasiveness of acidic fluoride (F) dentifrices with different F concentrations on bovine enamel. METHODS: Enamel blocks (4.0 x 4.0 mm2, n=120) were selected according to their surface microhardness and divided into 12 groups. Slurries of dentifrices were used containing 0 (placebo), 275, 412, 550 and 1,100 ppm F (pH 4.5 or 7.0), as well as testing two commercial dentifrices (Crest, positive control, 1,100 ppm F and Colgate Baby, 500 ppm F). Enamel blocks were partially protected with an adhesive tape (control area) and then brushed by an automated toothbrushing machine (16,000 strokes). During this process, 0.4 ml of the slurries were injected every 2 mins on the enamel blocks. After toothbrushing, enamel wear was determined by profilometry. STATISTICS: Results were analyzed by ANOVA and Tukey's test (p<0.05). RESULTS: The mean values for pH in the suspensions during treatment were 6.93, 4.32, 7.56 and 8.19 for neutral experimental dentifrices, acidic experimental dentifrices, Crest and Colgate baby, respectively. The abrasiveness of the acidic dentifrices was similar (p<0.05) to the neutral ones, whereas commercial dentifrices yielded lower abrasion (p<0.05). CONCLUSION: It was concluded that a reduction of the pH of dentifrices does not increase their abrasiveness.