Nucleic acids, as one of the most important macromolecules in living systems, play critical roles in storing, transferring, regulating genetic information, directing proteins synthesis, and catalysis. Understanding the structure of nucleic acid can bring us valuable information for mechanistic study and for drug discovery as well. Among all experimental methods, X-ray crystallography is the most powerful tool in structural biology study to reveal the 3D structure of macromolecules, which has provided over 80% of the highly detailed structural information to date. However, this great technology comes with two disturbing features, crystallization and phasing. The covalent selenium modification of nucleic acids has been proven to be a powerful tool to address both issues in nucleic acid crystallography. First part of this dissertation focuses on the development of novel selenium-modified nucleic acids (SeNA) for crystallization and phasing of B-form DNA containing structures. The novel 2’-SeMeANA modification is the first and currently the only selenium modification, which is fully compatible with X-ray crystallographic study of B-form DNA. Since selenium derivatization at 2’-arabino position dose not affect the B-type 2’-endo sugar conformation, this strategy is suitable for incorporating selenium into DNA for structural studies of B-DNA, DNA-protein complexes, and DNA-drug complexes. Specific base pairing is essential to many biological processes, including replication, transcription, and translation. It is crucial to NA (nucleic acid) sequence-based diagnostic and therapeutic applications as well. By utilizing the unique steric and electronic property of selenium, we designed, synthesized the novel 2-Se-U RNA modification, and demonstrated its highly specific base-pairing property by both biophysical and crystallographic methods. Our studies of 2-Se-U-containing RNAs suggest that this single-atom replacement can largely improve base pairing fidelity against U/G wobble pair, without significant impact on U/A pair.

The steady-state and time-resolved fluorescence of 2-aminopurine (2AP) have been used to monitor base dynamics and base stacking interactions in DNA single strands and dinucleotides, and to investigate the interactions between DNA and a polymerase, Pfu-Pol. A new class of base analogues has also been investigated using a combination of experiment and quantum chemical computation. In recent years, 2AP has been widely used as a fluorescent probe to study conformational changes and inter-bases interactions in duplex DNA, but the conformational behaviour of DNA in single strands has been far less investigated. In the present work, six 2AP–labelled single strands have been studied by steady-state and time-resolved fluorescence measurements. Single strands were found to show similar conformational heterogeneity (manifested by 4-exponential fluorescence decays) to duplex DNA, but highly stacked conformations, in which 2AP is rapidly quenched by inter-base charge transfer, are less populated in single strands, whereas imperfectly stacked (weakly quenched) conformations are more highly populated. The effect of base pairing in constraining base mobility is evident. To further investigate the influence of base stacking interaction on DNA conformation and the mechanism of inter-base quenching of 2AP, the time-resolved fluorescence of 2AP-containing dinucleotides was measured. The fluorescence decay of 2AP-containing dinucleotides in PBS buffer at room temperature is also multiexponential and the shortest lifetime varies with the identity of the natural base partner, in a manner consistent with quenching by inter-base electron transfer. When the dinucleotides are frozen to 77 K, the quenching of 2AP is almost eliminated, demonstrating the importance of thermal fluctuations of the bases in facilitating inter-base quenching at room temperature. In the frozen dinucleotides, an additional decay component with a lifetime significantly longer than unquenched 2AP is also observed, suggesting the formation of a new, delocalised, inter-base excited-state. Archaeal family-B DNA polymerases bind tightly to uracil and stall replication when they encounter this base in template strands, four bases ahead of the primer-template junction. If the polymerase progresses further towards the uracil, the 3′-5′ proof reading exonuclease becomes stimulated, trimming the primer and re-setting uracil to the +4 position. Uracil sensing prevents copying of the deaminated base and the introduction of mutations into the genome. Time-resolved fluorescence of 2AP has been used to investigate the role played by unwinding of primer-templates in this mechanism. 2AP-labelled primer-templates (2AP positioned next to the terminal 3′ base of the primer strand), with a misincorpated uracil at the +2 position (U+2) or +4 position (U+4) from the replication fork in the complementary template strand, were investigated in complex with the polymerase Pfu-Pol. For the U+2 primer-template, the fluorescence decay parameters show clear evidence for a decrease in the amount of double-stranded DNA on polymerase binding, manifested by marked weakening of inter-base stacking and a large transfer of population from highly stacked to poorly stacked conformations. In contrast, for the U+4 primer-template only a small perturbation to inter-base stacking is seen, together with the persistence of a high population of strongly stacked states. A new class of base analogues with selenium replacing oxygen at the 4 position of thymine and the 6 position of guanine has been investigated experimentally and computationally. These base analogues are interesting because they show a large shift (>80 nm) in their absorption spectrum compared with the natural bases, taking their absorption into the visible region, with minimal change in molecular structure. The potential of two examples of these analogues, 4-selenium thymine-3’-phosphate and 6-selenium-2’-deoxyguanosine-3-phosphate as luminescent probes has been investigated. However, they prove to have very low emission quantum yields for both fluorescence and phosphorescence. The effect of selenium-substitution on the structural and photophysical properties of the bases has been studied by various ab initio computational methods. It has been found that replacement of oxygen by selenium does not affect the ground state structure but changes the structure of the first excited-state from buckled to nearly planar. The shift in the absorption spectrum on introduction of selenium is successfully predicted by the calculations; the red-shifted absorption band of selenium-substituted thymine is due to a new electronic transition that is not present in the natural base, whereas that of selenium-substituted guanine is from red-shifting of a guanine-like transition.

Phosphorus-Selenium chemistry has seen a surge in development over the last five to ten years thanks to the optimisation of the synthesis of 2,4-diphenyl-1,3,2,4-diselenadiphosphetane-2,4-diselenide, Woollins' Reagent. This selenium analogue of the well known Lawesson's Reagent has proved itself to be a valuable asset to modern inorganic chemistry, providing a route to novel heterocycles, as well as acting as a selenation reagent with a wide range of functional groups. A series of new ammonium phenylphosphonamidodiselenoate ligands were synthesised via the reaction of Woollins' Reagent with a range of amines. The products were obtained in high yields and could be used as ligands for the synthesis of novel metal complexes. The reaction of diisopropylamine N-isopropyl-P-phenylphosphonamidodiselenoate with nickel(II) acetate produces a dimeric structure, whilst the reaction with copper(II) acetate yields a beautiful cluster of the form Cu₆Se₃L₆. The phenylphosphonamidodiselenoate ligands were further reacted with a range of cis-Pt(PR₃)₂Cl₂ complexes to form a library of 20 novel compounds, which were studied by ³¹P{¹H}, ⁷⁷Se{¹H} and ¹⁹⁵Pt{¹H} NMR spectroscopy. The X-ray crystal structure of one of these compounds was obtained, which confirmed the atom connectivity and spatial arrangement of the complexes and the geometry around the platinum centre. During investigations into the above-mentioned platinum complexes, it was postulated that an increase in steric bulk of the phosphine ligands would aid crystallisation of the products. As such, trimesityl-, dimesitylphenyl- and mesityldiphenyl phosphine were synthesised and reacted with elemental sulfur and selenium and hydrogen peroxide, as well as Pt(cod)Cl₂ and K₂[PtCl₄], yielding nine new structures, all of which were characterised by X-ray crystallography, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR spectroscopy. Finally Woollins' Reagent was reacted directly with a selection of metal complexes, yielding some new insights into its reactivity with inorganic moieties, which has been relatively sparsely reported until now.

This thesis presents advancements in the chemistry of selenium-bearing pincer ligands with respect to their synthesis, metal association and reactivity in addition to the overall nature of selenium as a donor atom. The synthesis of a new disilylamido ligand HN(SiMe2CH2SePh)2 2.1 and its potassium salt 2.2 is reported. The attempted metal association of these species was unsuccessful with various transition metals. Multinuclear NMR data suggests coordination to silver(I), 2.3 and copper(I), 2.4 with dπ-dπ back donation from the metal to the selenium donors. It is suggested from this data that –SePh can potentially act as a π-acceptor ligand as well as a σ- donor with heavy d metals. Another explanation for the observed shielding is conformational restrictions introduced by chelation. The preparation of new selenium-bearing diarylamine compounds RN(C7H6SeMe)2 (R=H: 3.1; R= Me: 3.10; R= Boc 3.11) via aryllithium chemistry is reported. Unsuccessful attempts to synthesize the –SePh and –SetBu derivatives are described using: aryllithium chemistry, Buchwald-Hartwig Amination cross coupling and Pd-catalyzed C-Se cross coupling. When reacted with MCl2(COD) (M= Pd, Pt), compound 3.10 coordinates with PdII forming a bidentate complex 3.12, while 3.1 forms tridentate complexes with PdII and PtII. NMR spectroscopy suggests the formation of a silver(I) complex 3.1-Ag from 3.1 and AgOTf, but X-ray diffraction data is required to determine its coordination motif. The new ligands and complexes have been fully characterized by (1H, 13C, 77Se) NMR spectroscopy and X-ray crystal structures are reported for 3.10, 3.12, 3.3 and 3.4. The NMR spectrum of 3.1-Ag exhibits a similar effect as the complexes of disilylamido ligands with suggested potential dπ-dπ back donation from the metal to the selenium donors. The catalytic ability of the new complex 3.3 has been tested in the Suzuki-Miyaura cross coupling reaction without notable improvements to existing catalysts. The instability of reactive intermediates may contribute to the low conversions or the size of the methyl group may decrease nanoparticle formation, a suggested active species. / October 2016

The micronutrient selenium is essential to human physiology. As the amino acid selenocysteine, it is inserted into selenoproteins with a wide range of functions including antioxidant capacity, thyroid hormone metabolism, improvement of immune system, brain function, fertility and reproduction. Low selenium status has been associated with increased risk for chronic diseases, such as cancer, type-2 diabetes and cardiovascular disease. In this context, several studies have been conducted in order to investigate if selenium supplementation could reduce the risk of such diseases. However, genetic variations may interfere in the response of individuals to a dietary intervention and must be considered as a important source of inter-individual variation. Therefore, this study was conducted was conducted to investigate the influence of genetic variations in selenoproteins genes on the response to an intervention with Brazil nuts, the richest source of selenium known in nature. The study included 130 healthy volunteers with both genders, aged 20 to 60 years old selected in University of São Paulo. They received nuts for 8 weeks, eating one nut a day, and did a washout period for more 8 weeks. All volunteers had a blood sampling collection every 4 weeks during 4 months, in a total of 5. The following analysis were done: anthropometric measurements, lipid profile, plasma malondialdehyde, plasma and erythrocyte Se, selenoprotein P, plasma and erythrocyte GPx activity, gene expression of GPX1, SEPP1, SELS and SEP15. The volunteers were also genotyped for SNPs rs1050450, rs3811699, rs1800699, rs713041, rs3877899, rs7579, rs34713741 and rs5845. Each unit of Brazil nut provided an average of 300 µg of selenium. All 130 volunteers completed the protocol. The concentrations of total cholesterol and glucose decreased after 8 weeks of supplementation. Moreover, HDL concentrations were higher for carriers of the variant T allele for GPX4_rs713041. The frequencies of the variant genotypes were 5,4% for rs1050450, rs3811699 e rs1088668, 10% for rs3877899, 19,2% for rs713041 e rs7579, 11,5% for rs5845 and 8,5% for rs34713741. The levels of the five biomarkers increased significantly after supplementation. In addition, erythrocyte GPx activity was influenced by rs1050450, rs713041 and rs5845; erythrocyte selenium was influenced by rs5845 and plasma selenium by rs3877899. Gene expression of GPX1, SEPP1 and SEP15 were higher after supplementation. The SNP rs1050450 influenced GPX1 mRNA expression and rs7579 influenced SEPP1 mRNA expression. Therefore, it can be concluded that the supplementation with one of Brazil nut for 8 weeks was efficient to reduce total cholesterol and glucose levels and to increase the concentrations of the main biomarkers of selenium status in healthy adults. Furthermore, our results suggest that GPX4_rs713041 might interfere on HDL concentrations and GPx1 activity, GPX1_rs1050450 might interfere on GPx1 activity, SEP15_rs5845 might interfere on GPx1 activity and erythrocyte selenium and SEPP1_3877899 might interfere on plasma Se levels. Therefore, the effect of genetic variations should be considered in future nutritional interventions evaluating the response to Brazil nut supplementation. / O micronutriente selênio é essencial para a fisiologia humana, inserido nas selenoproteínas na forma do aminoácido selenocisteína. As selenoproteínas são importantes para a função antioxidante, controle do metabolismo dos hormônios tireoidianos, melhora do sistema imune, função cerebral, fertilidade e reprodução. O estado nutricional de selênio deficiente ou marginal está associado com aumento do risco de doenças crônicas, como câncer, diabetes e doença cardiovascular. Sendo assim, diversos estudos procuraram investigar se a suplementação com selênio poderia reduzir o risco dessas doenças. Entretanto, as variações genéticas podem afetar a resposta dos indivíduos a uma intervenção dietética. Portanto, esse estudo foi conduzido para investigar a influência de variações genéticas em genes de selenoproteínas na resposta à suplementação com castanha-do-brasil, melhor fonte de selênio da natureza. Participaram do estudo 130 adultos de ambos os gêneros, com idade de 20 a 60 anos, selecionados na Universidade de São Paulo. Os indivíduos receberam castanhas suficientes para 8 semanas, ingerindo uma unidade por dia e, após o período de suplementação realizaram um período de washout também por 8 semanas. Todos realizaram cinco coletas de material biológico a cada quatro semanas. Foram realizadas medidas antropométricas, perfil lipídico, malondialdeído (MDA), concentração de selênio e selenoproteína P no plasma, eritrócitos, atividade da GPx eritrocitária e plasmática, expressão gênica da GPX1, SEPP1, SELS e SEP15. Além disso, os participantes foram genotipados para os SNPs rs1050450, rs3811699, rs1800699, rs713041, rs3877899, rs7579, rs34713741 e rs5845. Cada unidade de castanha forneceu em média 350µg de selênio. Todos os 130 voluntários concluíram o estudo. As concentrações de glicose e colesterol total diminuíram após 8 semanas de suplementação. Além disso, as concentrações de HDL-c foram influenciadas pelo SNP rs713041 no gene da GPX4, sendo os valores mais altos encontrados para os indivíduos com o alelo variante T (CT+TT). As frequências dos genótipos variantes foram 5,4% para rs1050450, rs3811699 e rs1088668, 10% para rs3877899, 19,2% para rs713041 e rs7579, 11,5% para rs5845 e 8,5% para rs34713741. Os níveis dos cinco biomarcadores aumentaram significativamente após a suplementação. Além disso, a atividade da GPx eritrocitária foi influenciada pelos rs1050450, rs713041 e rs5845, o selênio eritrocitário foi influenciado pelo rs5845 e o selênio plasmático pelo rs3877899. A expressão dos genes GPX1 e SEPP foram maiores após a suplementação. Tendo em vista esses resultados, conclui-se que a suplementação com uma unidade de castanha-do-brasil durante 8 semanas foi suficiente para reduzir as concentrações de colesterol e de glicose, e elevar as concentrações dos principais biomarcadores do estado nutricional de selênio. Além disso, observou-se que o polimorfismo rs713041 parece influenciar as concentrações de HDL-c e atividade da GPx1, o polimorfismo rs1050450 parece influenciar a atividade da GPx1, o polimorfismo rs5845 parece influenciar a atividade da GPx1 e o selênio eritrocitário e o polimorfismo rs3877899 parece influenciar a o selênio plasmático. Portanto, sugere-se considerar o perfil genético dos indivíduos em futuros estudos avaliando a resposta à suplementação com castanha-do-brasil no estado nutricional de selênio da população.

Setenta e sete vacas distribuídas em três propriedades foram divididas em três grupos: G1 (sem suplementação vitamínica), G2 (suplementação com 1000 UI de vitamina E durante 30 dias antes do parto previsto e 30 dias após o parto), G3 (suplementação com 1000 UI de vitamina E de 30 a 15 dias antes do parto previsto e 3000 UI de 15 dias antes do parto a 30 dias após o parto). Todas as propriedades continham os três grupos, sendo que as vacas foram sorteadas para cada grupo de acordo com a ordem de parição e a data prevista para o parto, para que ficassem homogeneamente distribuídas. Na interrupção da lactação que antecedeu o experimento, os quartos mamários foram tratados com antibióticos específicos para o tratamento de vacas secas. Os animais foram alimentados com silagem de milho e concentrado, permanecendo confinados com acesso a piquetes de descanso. Foram efetuados os exames: tamis, CMT e microbiológico do leite de cada quarto mamário, logo após a fase colostral e uma vez por mês durante a lactação, para o diagnóstico de mastite. Foram colhidas amostras de soro de 20% dos animais e dos alimentos fornecidos para a análise de selênio. Os resultados obtidos mostraram que a ocorrência de mastite clínica foi maior (p<0,05) no grupo não suplementado do que nos grupos suplementados. Não foram verificadas diferenças estatísticas entre os três grupos quanto à ocorrência de mastite subclínica. Os principais microrganismos isolados foram Staphylococcus sp, Streptococcus sp, Corynebacterium sp. A ocorrência de infecções intramamárias foi maior (p<0,05) no grupo G3 do que nos grupos G2 e G1 e maior (p<0,05) no grupo G2 do que no grupo G1. Em relação à ocorrência de mastite nas fazendas, foi verificado maior (p<0,05) ocorrência da forma clínica no grupo G1 do que nos demais grupos apenas em uma delas e quanto às infecções intramamárias, o grupo G3 apresentou maior (p<0,05) ocorrência que o grupo G1 em todas as fazendas. Os resultados das análises sorológicas de selênio mostraram que as concentrações do elemento nos animais estavam adequadas. / Seventy seven dairy cows, kept in three herds were randomly allocated in three homogeneous groups: Group 1, control group (without vitamin E supplementation), Group 2 (supplementation of 1,000 UI of vitamin E during 60 days, thirty days prior and 30 days post-parturition) and Group 3 (supplementation of 1,000 UI of vitamin E from the thirtieth day to the fifteenth day before parturition, and, then, a supplementation of 3,000 UI from the fourteenth day before parturition until the thirtieth day after it). All the cows in the groups received a long-action intramammary antibiotic at the drying off. Animals were fed with corn silage and concentrate-mixture, and they were confined in a free stall system with grass paddock. Examinations were performed at the drying off, in the first week of lactation and once a month during lactation. Strip cup, CMT and the microbiological exams were used. Twenty percent of the animals of each group were randomly assigned for selenium analysis. The obtained results showed that clinical mastitis occurrence in Group 1 was significantly higher than in Groups 2 and 3. In relation to subclinical mastitis cases, no significant differences were detected among the groups. Microorganisms that were most frequently isolated were: Staphylococcus sp, Streptococcus sp, Corynebacterium sp. Results obtained for mammary gland infections showed a higher level of infections in supplemented groups compared to the control group. The occurrence of clinical mastitis in Group 1 was significantly higher than in Groups 2 and 3 only in one of the dairy herds. The occurrence of the intramammary infections was significantly higher in Group 3 than in Group 1 in all herds. The results obtained from selenium analysis demonstrated to be range of recommended levels.

A deposição em regime de subtensão (DRS) tem sido amplamente utilizada para a formação de filmes semicondutores, mas muito pouco utilizada para estudar a dopagem de filmes eletrodepositados. Logo, neste trabalho é discutido o uso da DRS como técnica de dopagem de filmes de selênio. Para isso, estudou-se as condições de deposição de um filme de selênio trigonal sobre substrato de ouro (f-Se) e sua posterior modificação com a DRS de Bi (f-Se_Bi), Pb (f-Se_Pb) e Cu (f-Se_Cu). Estudos empregando voltametria cíclica, cronoamperometria, microscopia óptica, microscopia de varredura eletrônica e difração de raio-X evidenciaram a produção de um filme altamente cristalino, homogêneo e aderente formado por estruturas hexagonais em forma de microbastões com diâmetros entre 300 e 600 nm. Contudo, o filme com as características citadas é formado somente com a deposição a 80 ºC em HNO3 0,1 mol L-1 contendo SeO2 0,02 mol L-1, com polarização do substrato em -0,45 V (vs SCE), sob iluminação com lâmpada de halogênio 100 W, irradiância de 200 mW cm-2, agitação magnética e tempos de deposição &#8805; 600 segundos. Essas estruturas são mantidas mesmo após a DRS dos metais, a qual foi caracterizada empregando a microbalança eletroquímica de cristal de quartzo (MECQ). A partir do perfil massométrico constatou-se a ocorrência de difusão dos metais para o interior da fase de selênio, visto que não se observou a saturação da superfície do filme. Além disso, os metais apresentam cinética de difusão diferentes, onde o metal com maior difusão é o cobre, sendo o único a apresentar dopagem efetiva da matriz de selênio. A caracterização óptica dos filmes determinou um band gap de aproximadamente 1,87 &#177;0,03 eV para f-Se, f-Se_Pb e f-Se_Bi, entretanto, o f-Se_Cu apresentou band gap de 3,19 eV. Ainda assim, ao avaliar a atividade fotoeletroquímica dos semicondutores constatou-se a obtenção de fotocorrentes distintas entre eles. O f-Se_Bi produz fotocorrente 3 vezes maior que o f-Se_Pb e 35 vezes mais elevada que os demais, embora o selênio puro e os filmes dopados com DRS de Bi e Pb apresentem densidade de portadores de carga similares, aproximadamente 6,0 x1015 cm-3, enquanto o f-Se_Cu exibe um aumento de 4 ordens de grandeza para o mesmo parâmetro. Logo, a elevada fotocorrente do filme f-Se_Bi está relacionada com a minimização da recombinação de cargas na interface semicondutor-eletrólito, enquanto a baixa fotocorrente exibida pelo f-Se_Cu se deve à elevada energia de band gap do filme. De qualquer forma, a dopagem de filmes semicondutores com a DRS mostrou ser uma maneira simples e barata de dopagem de filmes relativamente espessos. / The underpotential deposition (UPD) have been widely used to production of semiconductor films, but not applied to search the doping of electrodeposited films. Therefore, here is discussed the use of UPD as a technique to doping selenium films. Then, it was studied the conditions to attain deposits of trigonal selenium on gold substrate (f-Se) and after its modification with Bi UPD (f-Se_Bi), Pb UPD (f-Se_Pb) and Cu UPD (f -Se_Cu). Studies using cyclic voltammetry, chronoamperometry, optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed the production of a highly crystalline, homogeneous and adherent selenium film formed by hexagonal structures with microrod shape and diameters between 300 and 600 nm. However, the trigonal selenium with those features is synthezised only on the deposition into HNO3 0.1 M containing SeO2 0.02 M at 80 °C, -0.45 V (vs. SCE), under illumination with halogen lamp 100 W, irradiance of 200 mW cm-2, magnetic stirring and deposition time &#8805; 600 seconds. These structures are maintained even after the UPD of the metals, which was characterized using electrochemical quartz crystal microbalance (EQCM). From massogram profile was possible to observe the occurrence of diffusion of the metals into the selenium phase, since was not verified the surface saturation of the film. Furthermore, the metals exhibited different diffusion kinetics, where the metal with higher diffusion was copper, which was the only one to show effective doping of selenium film. The optical characterization of the films determined a band gap average of 1.87 &#177;0,03 eV for f-Se, f-Se_Pb and f-Se_Bi, although, the f-Se_Cu presented band gap of 3.19 eV. Moreover, when it is studied the photoelectrochemical activity of the semiconductors films was noted different photocurrents between them. The f-Se_Bi produces photocurrent 3 times greater than the f-Se_Pb and 35 times higher than the other, but the pure selenium and those doped with Bi and Pb UPD present similar charge-carriers density, approximately 6.0 x1015 cm-3, while the f-Se_Cu shows an increase of 4 orders of magnitude for the same parameter. Therefore, the high photocurrent to f-Se_Bi is associated with the minimization of charge recombination at semiconductor-electrolyte interface, while the low photocurrent exhibited by f-Se_Cu is due to the higher energy band gap of the film. Anyway, the doping of the semiconductor film with the UPD proved to be a simple and inexpensive way to doping relatively thick films.

Nos últimos anos o selênio tem sido objeto de muitas pesquisas envolvendo tanto aspectos nutricionais quanto funcionais relacionados à saúde humana, Entretanto, dados de composição de alimentos em relação a este nutriente são escassos, devido principalmente às dificuldades de analises, que depende de técnicas analíticas e de equipamentos sofisticados e pela dificuldade em rastrear a origem dos alimentos, considerando que este elemento é dependente das concentrações do mesmo nos solos. O estudo foi realizado com quarenta e oito bois macho, provenientes de pasto da raça Nelore e distribuídos em dois grupos de animais, Grupo I fazenda Arrastão no município Taboado /MS e Grupo II Fazenda Rancho Queimado José Bonifácio /SP. Desses 24 animais de cada estado, foram selecionados os seguintes cortes de carne para determinação da concentração de selênio: coxão mole, coxão duro, músculo, patinho e alcatra. A concentração de selênio foi determinada por meio da técnica de espectrometria de absorção atômica por geração de hidretos acoplada à cela de quartzo. Os resultados em base úmida (in natura) encontrados nos seguintes tipos de cortes de carne em São Paulo foram: coxão mole 1,86 &#181;gSe/100g, coxão duro 1,98 &#181;gSe/100g, músculo 1,47 &#181;gSe/100g, patinho 1,23 &#181;gSe/100g e alcatra 1,64 &#181;gSe/100g.e no Mato Grosso do Sul foram: coxão mole 3,78 &#181;gSe/100g, coxão duro 3,76 &#181;gSe/100g, músculo 3,01 &#181;gSe/100g, patinho 2,64 &#181;gSe/100g e alcatra 3,47 &#181;gSe/100g. Observou-se que houve diferença significativa nos teores de selênio das carnes dependendo do Estado, independente dos tipos de cortes, sendo que naqueles provenientes do Estado do Mato Grosso do Sul o teor de selênio foi maior que naqueles de São Paulo (p < 0,0001). Entre os tipos de cortes (patinho, alcatra, músculo, coxão mole e coxão duro) também houve diferença significativa independente dos Estados de onde foram provenientes (p < 0,0001). No entanto, não houve diferença significativa no teor de selênio quando os dois fatores (Estado e tipo de corte) foram observados um dependente do outro (p = 0,4736 - base seca; p = 0,3920 - base úmida). Os resultados do presente estudo confirmam a influência da localização nas concentrações de selênio dos alimentos e podemos concluir que a concentração de selênio nas carnes varia de acordo com sua procedência e o tipo de corte. / In recent years selenium has been the subject of many investigations involving both nutritional and functional aspects related to human health, however, food composition data on this nutrient are scarce, mainly due to difficulties of analysis, which relies on analytical techniques and sophisticated equipment and the difficulty in tracing the origin of food, considering that this element is dependent on the concentrations of the same in the soil. The study was conducted with forty-eight oxen Male from Nelore breed and divided into two groups of animals, Group I farm Arrastão in the city of Taboado/MS and Group II Rancho Queimado in the city of José Bonifácio/SP. Of these 24 animals of each state, we selected the following cuts of meat to determine the concentration of selenium: topside, flat, fore shank, knuckle and rump. The selenium concentration was determined using the technique of atomic absorption spectrometry coupled with hydride generation quartz cell. The results for wet (fresh) found in the following types of meat cuts in Sao Paulo were topside 1.86 &#181;gSe/100g, flat 1.98 &#181;gSe/100g, fore shank 1.47 &#181;gSe/100g, knuckle 1,23 &#181;gSe/100g and rump 1.64 &#181;gSe/100g. In Mato Grosso do Sul were topside 3.78 &#181;gSe/100g, flat 3.76 &#181;gSe/100g, fore shank 3.01 &#181;gSe/100g, knuckle 2,64 &#181;gSe/100g and rump 3.47 &#181;gSe/100g. There was a significant difference in levels of selenium from meat depending on the state, regardless of the types of cuts, while those from the State of Mato Grosso do Sul, the selenium content was higher than those of São Paulo (p <0, 0001). Among the types of cuts (topside, flat, fore shank, knuckle and rump) also was no significant difference regardless of where they were from states (p <0.0001). However, no significant difference in selenium content was found when the two factors (state and type of cut) were observed dependent on one another (p = 0.4736 - dry basis, p = 0.3920 - wet basis). The results of this study confirm the effect of selenium on the location of food and can be concluded that the selenium concentration in meat varies according to their origin and type of cut.

Relatório realizado pela CETESB em 2006 mostrou que 80% dos 645 municípios são total ou parcialmente abastecidos por água subterrânea e que em 13 bacias hidrográficas do Estado de São Paulo a água subterrânea é a fonte prioritária de abastecimento. O uso da água subterrânea em diversos setores reforça a sua importância e gera preocupações quanto a sua proteção e qualidade. A região noroeste do Estado de São Paulo, abastecida principalmente por captação de água subterrânea do aqüífero Guarani por meio de poços tubulares, apresenta ocorrência de Selênio. Assim, no presente trabalho procurou-se avaliar a contribuição de selênio em águas subterrâneas. Foram coletadas amostras de água subterrânea de quatro poços tubulares profundos captadas do aqüífero Guarani na região noroeste do Estado de São Paulo e foram realizadas medidas do elemento selênio, utilizando a espectrometria de absorção atômica com atomização eletrotérmica (GFAAS) e geração de hidretos (HGAAS). Além do selênio também foram analisados outros metais (B, Al, V, Cr, Mn, Ni, Cu, Zn, Mo, Sn, Li, Be, Mg, P, Ca, Fe, Ba, Co, Na, Si, K, Ag, Cd, Pb, Sb, Hg e As) por ICP OES em todas as amostras. A caracterização do selênio foi realizada com uma periodicidade de amostragem trimestral, no período de Março de 2006 a Março de 2007, totalizando cinco campanhas. O metal analisado neste estudo foi selecionado atendendo-se as exigências da legislação que avalia a qualidade da água para abastecimento publico, estabelecendo limites máximos permissíveis para concentração de metais: Portaria 518/2004 MS (VPM para Se: 0,010 mg/L), referente à potabilidade. As análises realizadas mostraram que as concentrações de Se estão acima do limite máximo permissível e que as técnicas atomização eletrotérmica (GFAAS) e geração de hidretos (HGAAS) demonstraram equivalência nos resultados. As análises demonstraram que a presença de Se parece estar associada a fatores mineralógicos (formação geológica da região) e as metodologias apresentaram-se eficientes com respostas similares diferenciando-se em fatores operacionais e de custo. / Report carried out for CETESB in 2006 showed 80% of the 645 cities are totally or partially supplied by underground water, and for 13 river basins of São Paulo State the underground water is the priority source for potable water supply. The use of underground water in different sectors reinforces its importance and highlight the concern about their protection and quality. The northwest region of São Paulo state is mainly supplied by underground water of the Guarani aquifer extracted by tubular wells, which presents some occurrence of Selenium. In the present study it was looked and evaluated, through the comparison of high sensitivity and selectivity methods as the atomic absorption spectrometry using electrothermal atomizaton (GFAAS) and the hydride generation (HGAAS). Underground water samples of four deep tubular wells of Guarani aquifer in the northwest of São Paulo state were collected to measure the selenium element. In addition to selenium other metals were analyzed (B, Al, V, Cr, Mn, Ni, Cu, Zn, Mo, Sn, Li, Be, Mg, P, Ca, Fe, Ba, Co, Na, Si, K, Ag, Cd, Pb, Sb, Hg and As). The characterization of selenium was carried out with quarterly sampling regularity, in the period of March of 2006 to March of 2007, totalizing five campaigns. The metal analyzed in this study was selected according to the requirements of the legislation for potable water quality evaluation, establishing permissible maximum limits for metal concentration. The results had shown the concentrations of Se are above of the maximum permissible limits and the techniques electrothermal atomization (GFAAS) and hydride generation (HGAAS) demonstrated equivalence in their results. The results demonstrated also the presence of Se can be associated with mineralogical factors (as geologic formation of the region) and the applied methodologies were efficient with similar answers for different operational factors and expenses.

Contexto: Pacientes com tireoidite autoimune crônica com anticorpos de peroxidase tireoideana (Anti-TPO) podem progredir para hipotireoidismo subclínico e clínico. Estudos anteriores mostraram uma redução no anti-TPO em pacientes com hipotireoidismo que receberam tratamento de reposição de LT4 e suplementação de selênio. Objetivos: Avaliar se a selenometionina (SeMet) reduz o anti-TPO em pacientes anti-TPO positivos eutireoideos tratados com LT4 e melhora a ecogenecidade da tireoide em comparação com grupo de pacientes tratados com placebo. Desenho: Estudo duplo-cego aleatório controlado com placebo. Pacientes e métodos: Um total de 55 pacientes consecutivos com TCA (50 mulheres, 5 homens, idade mediana de 48 anos variando de 20 a 58), 4 tabagistas, 4 anos desde o diagnóstico da doença (mediana), com TSH normal ou levemente elevado, T4L dentro dos níveis normais, anti-TPO maior que 100 U/ml foram aleatoriamente selecionados para receber uma dose diária de 200 ?g de selenometionina (grupo SeMet; n = 28) ou placebo (grupo P; n = 27) por 3 meses. Anticorpos da tireoperoxidase e tireoglobulina (TPO-Ab; TG-Ab), TSH, FT4, T3, T4, proteína C-reativa (PCR), citocinas (IL6, IL10, TNF), glicose sanguínea em jejum, calcitonina, selênio plasmático, concentração de iodo na urina, atividade da peroxidase de glutationa 1 em eritrócitos (GPx1) foram dosados no basal, após 3 e 6 meses de acompanhamento. Polimorfismo do GPx1-Pro198Leu foi avaliado no basal. Foi efetuado ultrassom de tireoide (US) em cada ponto de acompanhamento. Ecogenecidade do tecido foi caracterizada por análise histográfica computadorizada em escala de cinza e expressa como índice de ecogenecidade (EI). A relação entre concentração de Selênio e atividade GPx1 nos eritrócitos foi analisada para cada genótipo. O IE e associações de variáveis clínicas também foram avaliadas. Resultados: Não houve diferenças nas características iniciais (basais) entre o grupo SeMet e P. Selênio plasmático e atividade GPx1 aumentaram no grupo SeMet mas não variaram no grupo P durante a suplementação de SeMet. Anti-TPO, anti-TG, TSH e hormônios tireoidianos não variaram significativamente no grupo P. Anti-TPO no grupo SeMet era de 1009 (176- >3000) no basal, 958 (161- > 3000) aos 3 meses e 768 (65-2821) U/ml aos 6 meses. Neste grupo, as variações em relação ao basal foram de -5% aos 3 meses e -24% aos 6 meses, respectivamente. No grupo P, as mudanças em relação ao basal foram de 1206 (154- >3000), 1404 (231- >3000), 1430 (140- >3000 U/ml), respectivamente (valores médios e limítrofes); +16% aos 3 meses e +18% aos 6 meses, respectivamente. Níveis de TSH, no grupo SeMet, foram de 1,7 (0,8 - 2,5) no basal, 3,0 (1,1 - 6,3) aos 3 meses e 3,2 (1,1 - 6,5) ?U/mL aos 6 meses, no grupo P, os níveis de TSH foram de 1,7 (0,8 - 2,5) no basal, 2,2 (0,6 - 6,8) e 2,5 (0,9 - 5,5) ?U/mL, respectivamente (valores médios e limítrofes). Valores médios da proteína C-reativa foram inferiores a 10mg/L nos dois grupos. O percentual dos genótipos no grupo SeMet eram de 7,1%, 64,3% e 28,6% para Leu/Leu, Pro/Leu e Pro/Pro (o genótipo mais frequente), respectivamente; no grupo P, a distribuição foi 0,0%, 51,9% e 48,1% para Leu/Leu, Pro/Leu e Pro/Pro, respectivamente, comparado com controles normais (11,4%, 39,2% e 49,4% Leu/Leu, Pro/Leu e Pro/Pro respectivamente). O IE exibiu tendência a uma diferença significativa indo de 1,2 no basal para 1,0 aos 3 meses e 1,1 aos 6 meses para o grupo SeMet, respectivamente, enquanto que permaneceu constante (1,2 no basal, 1,2 aos 3 meses e 1,2 aos 6 meses) para o grupo P, respectivamente. Após o período de suplementação, o coeficiente de correlação r = 0,95 (p < 0,001) para Pro/Pro e a tendência foi a mesma que o basal para o grupo Pro/Leu. No grupo SeMet, o IE correlacionou-se positivamente com a velocidade sistólica de pico nas artérias inferiores da tireoide no basal (r = 0,5, p = 0,008) e após o período de suplementação (r = 0,46; p = 0,025). Anti-TG correlacionou-se com valores do fator de necrose tumoral médios no grupo placebo (r = 0,46; p = 0,015). Conclusão: A suplementação por 3 meses aumentou os marcadores do status de selênio. SeMet parece ser eficaz em reduzir a ecogenecidade da tireoide e em reduzir o anti-TPO (porém não o anti-TG) após 3 meses de intervenção, mas não influencia o TSH ou os hormônios tireoideanos / Context: Autoimmune chronic thyroiditis (ACT) euthyroid subjects with positive thyroid peroxidase antibodies (TPO-Ab) may progress to subclinical and overt autoimmune hypothyroidism. Previous studies have shown a decrease in TPO-Ab in hypothyroid patients receiving LT4 replacement therapy plus selenium supplementation. Objectives: To evaluate in euthyroid TPOAb-positive LT4-treated subjects whether selenometionine (SeMet) decreases TPO-Ab and improves thyroid ecogenicity in comparison with placebo. Design: Randomized, placebo-controlled, double-blind study. Patients and methods: A total of 55 consecutive patients with ACT (50 F, 5 M, age median: 48, range: 20-58 years), 4 smokers, duration of disease (median) 4 years, normal or slightly elevated TSH and FT4 within the normal range, TPO-Ab >= 100 U/mL were randomized to receive 200 ?g selenometionine daily ((group SeMet; n = 28) or placebo (group P; n = 27) for 3 months. Thyroperoxidase and thyroglobulin autoantibodies (TPO-Ab; TG-Ab), TSH, FT4, T3, T4, C-reactive protein (CRP), cytokines (IL6, IL10, TNF), fasting blood glucose, calcitonin, plasma selenium, urine iodine concentrations, activity of glutathione peroxidase 1 in erythrocytes (GPx1) were estimated at baseline, after 3 and 6 months of follow-up; GPx1-Pro198Leu polymorphism was assessed at baseline. Thyroid ultrasound (US) was performed at each follow-up point. Tissue ecogenicity was characterized by computerized grey-scale histographic analysis and expressed as ecogenicity index (EI). The relationship between Se concentration and GPx1 erytrocyte activity was analysed for each genotype group. EI and clinical variables associations were also evaluated. Results: There were no differences in baseline characteristics between the SeMet group and the P group. During SeMet supplementation, plasma Se and GPx1 activity did not change in the P group, but increased in the SeMet group. TPO-Ab, anti-TG, TSH and thyroid hormones did not change significantly in group P. TPO-Ab in the SeMet group were 1009 (176- >3000) at baseline, 958 (161- >3000) at 3 months and 768 (65-2821) U/mL at 6 months. In this group change from baseline were -5 at 3 months and -24% at 6 months, respectively. In the P group change from baseline were 1206 (154- >3000), 1404 (231- >3000) and 1430 (140- >3000) U/mL, respectively (mean values with range); from baseline were +16 at 3 months and +18% at 6 months, respectively. TSH in the SeMet group were 1.7 (0·8-2·5) at baseline, 3·0 (1·1-6·3) at 3 months and 3.2 (1,1-6,5) uU/mL at 6 months; in the P group were 1·7 (0·8-2·4), 2·2 (0·6-6·8) and 2.5 (0.9-5.5) ?U/mL, respectively (mean values with range). C-reative protein mean level was <10 mg/L in both groups. Genotype proportions in the SeMet group were 7.1, 64.3, and 28,6% for Leu/Leu, Pro/Leu and Pro/Pro (the wild-type genotype), respectively; in the P group were 0.0, 51.9 and 48.1 for Leu/Leu, Pro/Leu and Pro/Pro, respectively compared with normal controls (11.4, 39.2 and 49.4%, Leu/Leu, Pro/Leu and Pro/Pro, respectively). EI exhibited a tendency towards a significant difference from 1.2 at baseline to 1.0 at 3 months and 1.1 at 6 months for the SeMet group, respectively and remained the same (1.2 at baseline, 1.2 at 3 months and 1.2 at 6 months) for the P group, respectively. For the SeMet group there was no significant correlation for Pro/Pro and Pro/Leu genotypes at the baseline. After the supplementation period, the correlation coefficient was r = 0.95 (p < 0.001) for Pro/Pro and the trend was the same as baseline for Pro/Leu. In the Semet group EI correlated positively with systolic peak velocity in the inferior thyroid arteries at baseline (r = 0.50; p = 0.008) and after supplementation period (r = 0,46; p = 0,025). Anti-TG correlated with tumor necrosis factor mean values in the Placebo group at baseline (r = 0,46; p = 0,015). Conclusion: Three months selenometionine supplementation increased markers of selenium status. SeMet seems to be effective in reducing thyroid echogenicity and in reducing TPO-Ab (but not TG-Ab) after 3 months of intervention, but does not influence TSH or thyroid hormones