Ultraviolet excitation of photoconductivity in thin films of sol-gel SnO2

Tin dioxide (SnO2) thin film photoconductivity spectra were measured for a large temperature range using a deuterium source, the intensity of photocurrent spectra in the range 200-400 nm is temperature dependent, and the photocurrent increases in the ultraviolet even for illumination with photon energies much higher than the bandgap transition. This behavior is related to recombination of photogenerated electron-hole pairs with oxygen adsorbed at grain boundaries, which is consistent with nanoscopic crystallite size of sol-gel deposited films. (c) 2005 Elsevier Ltd. All rights reserved.

Electron scattering and effects of sources of light on photoconductivity of SnO2 coatings prepared by sol-gel

Electro-optical properties of sol-gel derived 2 mol% antimony or niobium doped tin dioxide films have been measured. The electron density has been calculated considering all the relevant scattering mechanisms and experimental conductivity data measured in the range -197 to 25 degrees C. The results support the hypothesis that both ionised impurity scattering and grain boundary scattering have comparable effects in the resistivity of coatings, for free electron density congruent to 5 x 10(18) cm(-3). We have measured variation of photoconductivity excitation with wavelength using xenon and deuterium lamp as light sources. Results show that the main band in the photoconductivity spectrum is dependent on the spectral light source emission, the excitation peak reaching 5 eV (deuterium lamp). This band is due to the recombination process involving oxygen species and photogenerated electron-hole pairs. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Bioavailability of synthetic and biosynthetic deuterated lycopene in humans

Current knowledge of the bioavailability of lycopene in humans is limited due to the inability to distinguish newly administered lycopene from the body reserves of lycopene. A quantitative method to assess the absorption and relative bioavailability of newly absorbed synthetic or natural lycopene was developed using two deuterated lycopene sources, in conjunction with an advanced LC/APCI-MS (liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry) to analyze newly absorbed lycopene in blood samples of study subjects. Two subjects (1 male and 1 female) consumed hydroponically grown tomatoes containing deuterium-enriched lycopene (8084 g wet weight tomato containing 16.3 and 17.4 mu mol lycopene, respectively) and two subjects (1 male, and 1 female) consumed 11 mu mol synthetic H-2(10) lycopene in 6 g of corn oil. Tomatoes were steamed and pureed. The doses were given together with a liquid formulated drink with 25% energy from fat. Our results showed that up to 34 days after taking an oral 2 1110 lycopene dose (synthetic or from tomato) with a liquid formula drink, the area under the curve of the average serum percent enrichment response of synthetic lycopene reached 33.9 (+/- 1.7) nmol-day/mu mol lycopene in the dose, whereas that of lycopene from the tomato dose was 11.8 (+/- 0.3) nmol-day/mu mol lycopene in the dose. Our study provides evidence that the absorption of physiological levels of lycopene in intrinsically labeled tomatoes can be studied in humans. From these preliminary investigations, we find that the bioavailability of synthetic lycopene in oil appears to be about three times higher than that of lycopene from steamed and pureed tomatoes. (c) 2005 Elsevier B.V. All rights reserved.

Oxygen related defects excitation and photoconductivity dependence of SnO2 sol-gel films with several light sources

Since oxygen vacancies act as donors in SnO2, the electrical properties are related to deviation from stoichiometric composition. Depending on stoichiometry SnO2 can be highly insulating or may exhibit fairly high n-type conductivity. Since bandgap transitions are in the ultraviolet range, its photoconductivity is strongly dependent on the excitation source. We have measured variation of photoconductivity excitation with wavelength for tin dioxide grown by dip-coating sol-gel technique using several light sources: tungsten lamp, xenon, mercury and deuterium, and present selected results. The main band is obtained in the range 3-4eV according to light source spectrum in the ultraviolet range. The presence of oxygen in the cryostat also affects the spectrum since electron-hole pairs react with adsorbed oxygen specimens. © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.

Orphan nuclear receptor NGFI-B forms dimers with nonclassical interface

The orphan receptor nerve growth factor-induced B (NGFI-B) is a member of the nuclear receptor's subfamily 4A (Nr4a). NGFI-B was shown to be capable of binding both as a monomer to an extended half-site containing a single AAAGGTCA motif and also as a homodimer to a widely separated everted repeat, as opposed to a large number of nuclear receptors that recognize and bind specific DNA sequences predominantly as homo- and/or heterodimers. To unveil the structural organization of NGFI-B in solution, we determined the quaternary structure of the NGFI-B LBD by a combination of ab initio procedures from small-angle X-ray scattering (SAXS) data and hydrogen-deuterium exchange followed by mass spectrometry. Here we report that the protein forms dimers in solution with a radius of gyration of 2.9 nm and maximum dimension of 9.0 nm. We also show that the NGFI-B LBD dimer is V-shaped, with the opening angle significantly larger than that of classical dimer's exemplified by estrogen receptor (ER) or retinoid X receptor (RXR). Surprisingly, NGFI-B dimers formation does not occur via the classical nuclear receptor dimerization interface exemplified by ER and RXR, but instead, involves an extended surface area composed of the loop between helices 3 and 4 and C-terminal fraction of the helix 3. Remarkably, the NGFI-B dimer interface is similar to the dimerization interface earlier revealed for glucocorticoid nuclear receptor (GR), which might be relevant to the recognition of cognate DNA response elements by NGFI-B and to antagonism of NGFI-B-dependent transcription exercised by GR in cells. Published by Cold Spring Harbor Laboratory Press. Copyright © 2007 The Protein Society.

The Mycobacterium tuberculosis Rv2540c DNA sequence encodes a bifunctional chorismate synthase

Background. The emergence of multi- and extensively-drug resistant Mycobacterium tuberculosis strains has created an urgent need for new agents to treat tuberculosis (TB). The enzymes of shikimate pathway are attractive targets to the development of antitubercular agents because it is essential for M. tuberculosis and is absent from humans. Chorismate synthase (CS) is the seventh enzyme of this route and catalyzes the NADH- and FMN-dependent synthesis of chorismate, a precursor of aromatic amino acids, naphthoquinones, menaquinones, and mycobactins. Although the M. tuberculosis Rv2540c (aroF) sequence has been annotated to encode a chorismate synthase, there has been no report on its correct assignment and functional characterization of its protein product. Results. In the present work, we describe DNA amplification of aroF-encoded CS from M. tuberculosis (MtCS), molecular cloning, protein expression, and purification to homogeneity. N-terminal amino acid sequencing, mass spectrometry and gel filtration chromatography were employed to determine identity, subunit molecular weight and oligomeric state in solution of homogeneous recombinant MtCS. The bifunctionality of MtCS was determined by measurements of both chorismate synthase and NADH:FMN oxidoreductase activities. The flavin reductase activity was characterized, showing the existence of a complex between FMN ox and MtCS. FMNox and NADH equilibrium binding was measured. Primary deuterium, solvent and multiple kinetic isotope effects are described and suggest distinct steps for hydride and proton transfers, with the former being more rate-limiting. Conclusion. This is the first report showing that a bacterial CS is bifunctional. Primary deuterium kinetic isotope effects show that C4-proS hydrogen is being transferred during the reduction of FMNox by NADH and that hydride transfer contributes significantly to the rate-limiting step of FMN reduction reaction. Solvent kinetic isotope effects and proton inventory results indicate that proton transfer from solvent partially limits the rate of FMN reduction and that a single proton transfer gives rise to the observed solvent isotope effect. Multiple isotope effects suggest a stepwise mechanism for the reduction of FMNox. The results on enzyme kinetics described here provide evidence for the mode of action of MtCS and should thus pave the way for the rational design of antitubercular agents. © 2008 Ely et al; licensee BioMed Central Ltd.

Caracterização da morfologia externa e do sistema reprodutor de fêmeas de Amblyomma brasiliense Aragão, 1908 (Acari: Ixodidae)

Pós-graduação em Ciências Biológicas (Biologia Celular e Molecular) - IBRC

Estudo da dinâmica conformacional das enzimas Chiquimato Quinase e 5-enolpiruvilchiquimato-3-Fosfato Sintase (EPSPS) de Mycobacterium tuberculosis através do monitoramento da troca isotópica hidrogênio/deutério por espectrometria de massas ESI

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

Análise da composição corporal em adolescentes obesos

Pós-graduação em Alimentos e Nutrição - FCFAR

Estudo teórico da contribuição à dose de partículas secundárias geradas por prótons de energias entre 100 e 200 MeV num Phantom de substituto de tecido MS20

The goal of this project is the reproduction, through the simulation code based on the MCNPX (Monte Carlo N-Particle eXtended) v2.50 method, of the proton beam interaction with the material, since, in proton therapy, only the particle ionization and excitation are analyzed and the occurence of nuclear interactive inelastic process are not considered. This work will help the development of studies concerning the contribution to the total dosis of secondary particles generated by nuclear interaction in proton therapy. They are: alpha particles ( ), deuterium(2H), tritium (3H), neutron (n) and helium (3He). A MS20 tissue substitute phantom was used as the target and the energy of the proton beams was within an interest range of 100 to 200MeV. With the results obtained, it was possible to generate graphics which allows the analysis of the dosis deposition relation with and without nuclear interaction, the percentage of secondary particles deposited dosis, the radial dispersion of neutrons in the material, the secondary particles multiplicity, as well as the relation between the secondary particles spectrum with the próton generated spectrum

Estudo teórico da contribuição a dose de partículas secundárias geradas por prótons de energias entre 100-200 MeV num phantom de músculo estriado

In the treatment plans in conventional Proton therapy are considered only the elastic interactions of protons with electrons and/or nuclei, it means, mainly ionization and coulomb excitation processes. As the energy needed to reach the deep tumors should be of several hundred of MeVs, certainly the nuclear inelastic channels are open. Only some previous studies of the contribution of these processes in the full dose have been made towards targets composed of water. In this study will be presented the results of the simulation of the processes of interaction of beams of protons in the range of 100-200 MeV of energy with a cylindrical phantom composed by striated muscle (ICRU), emphasizing in the contribution to total dose due to the deposition of energy by secondary particles alpha (α), deuterium (2H), tritium (3H), neutron (n) and hélio3 (3He), originated by nuclear inelastic processes. The simulations were performed by using the method of Monte Carlo, via the computer code MCNPX v2.50 (Monte Carlo N-Particle eXtended). The results will be shown demonstrated through the graphics of the deposited dose with or without nuclear interaction, the percentual of dose deposited by secondary particles, the radial dispersion of neutrons, as well as the multiplicity of secondary particles

Rastreabilidade da cama de aviário por isótopos estáveis em bovinos leiteiros

Pós-graduação em Zootecnia - FMVZ

Níveis de carboidratos e lipídios em dietas para juvenis de tambaqui (Colossoma macropomum): variáveis produtivas, fisiológicas e turnover isotópico

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

Efeitos da suplementação de taurina ou flavonóides de cacau associado à achocolatado sobre a composição corporal, metabolismo de carboidratos e proteinas, desempenho fisico, dano muscular e estresse oxidativo em atletas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Temporal and Spatial Variations of Ions, Isotopes and Agricultural Contaminants in Surface Waters and Groundwater of Nebraska's Rainwater Basin Wetland Region

The wetlands of south-central Nebraska’s Rainwater Basin region are considered of international importance as a habitat for millions of migratory birds, but are being endangered by agricultural practices. The Rainwater Basin extends across 17 counties and covers 4,000 square miles. The purpose of this study was to assemble baseline chemical data for several representative wetlands across the Rainwater Basin region, and determine the use of these chemical data for investigating groundwater recharge. Eight representative wetlands were chosen across the Rainwater Basin to monitor surface and groundwater chemistry. At each site, a shallow well and deep well were installed and sampled once in the summer of 2009 and again in the spring of 2010. Wetland surface water was sampled monthly from April, 2009 to May, 2010. Waters were analyzed for major ions, nutrients, pesticides and oxygen-18 and deuterium isotopes at the University of Nebraska Water Sciences Laboratory. Geochemical analysis of surface waters presents a range of temporal and spatial variations. Wetlands had variable water volumes, isotopic compositions, ion chemistries and agricultural contaminant levels throughout the year and, except for a few trends, theses variations cannot be predicted with certainty year-to-year or wetland-to-wetland. Isotopic compositions showed evaporation was a contributor to water loss, and thus, did impact water chemistry. Surface water nitrate concentrations ranged from <0.10 to 4.04 mg/L. The nitrate levels are much higher in the groundwater, ranging from <0.10 to 18.4 mg/L, and are of concern because they are found above the maximum contaminant level (MCL) of 10 mg/L. Atrazine concentrations in surface waters ranged from <0.05 to 10.3 ppb. Groundwater atrazine concentrations ranged from <0.05 to 0.28 ppb. The high atrazine concentrations in surface waters are of concern as they are above the MCL of 3 ppb, and the highest levels occur during the spring bird migration. Most sampled groundwaters had detectable tritium indicating a mix of modern (<5 to 10 years old) and submodern (older than 1950s) recharge. The groundwater also had differences in chemical and isotope composition, and in some cases, increased nitrate concentrations, between the two sampling periods. Modern groundwater tritium ages and changes in groundwater chemical and isotopic compositions may indicate connections with surface waters in the Rainwater Basin.