Neste trabalho serão apresentados resultados sobre três sistemas proteícos diferentes: Lisozima, Crioglobulina e Proteassomo, analisados a partir, principalmente, da técnica de espalhamento de Raios X a baixos ângulos. Técnicas como microscopia eletrônica de transmissão e espalhamento de luz dinâmico foram utilizadas como técnicas complementares. Os resultados apresentados demonstram o potencial único que a técnica de espalhamento a baixos ângulos possui no estudo de sistemas em solução. Os dados correspondem a um estudo em um grande intervalo de tamanhos para as proteínas estudadas (15kDa to 750 kDa), requerendo diferentes abordagens em cada caso. Como será mostrado, para casos onde se tem um meio monodisperso, diversas metodologias de modelagem podem ser utilizadas. Para o sistema composto de Lisozima, por se tratar de uma proteína amplamente estudada na literatura, é interesante poder comparar os resultados encontrados com os já publicados e observar sua estabilidade em solução. O peso molecular calculado a partir dos dados de espalhamento foi 15kDa, que está em bom acordo com a esperado para esta proteina (14,6 kDa). Além disso, ao variar-se a concentração da proteína em solução, é possível observar um fator de interação entre as partículas para maiores concentrações. Esse fator de interação pode ser considerado próximo ao de esferas rígidas. Para o sistema de Crioglobulinas, houve uma dificuldade na purificação da amostra, mas ainda assim apresentaremos alguns resultados interessantes, em que a técnica de SAXS fornece informações sobre a flexibilidade de proteínas e as análises para as amostras de um pool de imunoglobulinas indicou que com a diminuição da temperatura a dispersão de raios de giro aumenta, indicando a formação de agregados. Para o sistema do Proteassomo, diversas análises se mostraram possível e resultados novos puderam ser obtidos e publicados. Dos estudos utilizando MET,com as micrografias obtidas tem-se a indicação de diferenças na estrutura, quando a molécula está em condições diferentes. Das análises feitas por SAXS, é possível utilizar duas modelagens diferentes, uma simples, outra mais avançada, em que se pode concluir que a redução do Cys-PT glutatiolado induz mudanças conformacionais. Além disso, resultados de SAXS e MET estão em concordância e fornecem informações complementares. / In this work results will be presented on three different protein system: Lysozime, Cryoglobulin and Proteasome, analyzed mainly by Small Angle X-ray scattering technique. Techniques such as transmission electron microscopy and dynamic light scattering were used as complementary techniques. The results show that an unic potential Small Angle X-ray scattering technique around the study of systems in solution. The data correspond to a study of a wide range of sizes for the studied proteins (15kDa to 750 kDa), requiring different approaches in each case. As will be shown for cases where there is a monodisperse system, different modeling methodologies may be used. For the system composed of Lysozyme, because it is a protein widely studied in the literature, it is interesting to compare the results with those already published and observe its stability in solution. The molecular weight calculated from the scattering data was 15kDa, which is in good agreement with the expected for this protein (14.6kDa). Futhermore by varying the concentration of the protein in solution, it is possible to observe a factor of interaction between the particles for higher concentrations. This interaction factor can be considered close to the rigid spheres. For Cryoglobulins system, there was a difficulty in the sample purification, but still present some interesting results, where the SAXS technique provides information on the flexibility of proteins and the analysis for the samples from a pool of immunoglobulin indicated that with decreasing temperature, the dispersion of radius of gyration increases, indicating the formation of aggregates. For the proteasome system, various analyzes have proved possible and new results could be obtained and published. From studies using TEM, with the micrographs we have the indication of differences in the structure, when the molecule is in different conditions. From the analyzes made by SAXS, it is possible to use two different modeling, a simple one, and other more advanced, where it can be concluded that the reduction of the Cys-PT glutathiolated induces conformational changes. Moreover, SAXS and TEM results are in agreement and provide additional information.

Neste trabalho serão apresentados resultados sobre três sistemas proteícos diferentes: Lisozima, Crioglobulina e Proteassomo, analisados a partir, principalmente, da técnica de espalhamento de Raios X a baixos ângulos. Técnicas como microscopia eletrônica de transmissão e espalhamento de luz dinâmico foram utilizadas como técnicas complementares. Os resultados apresentados demonstram o potencial único que a técnica de espalhamento a baixos ângulos possui no estudo de sistemas em solução. Os dados correspondem a um estudo em um grande intervalo de tamanhos para as proteínas estudadas (15kDa to 750 kDa), requerendo diferentes abordagens em cada caso. Como será mostrado, para casos onde se tem um meio monodisperso, diversas metodologias de modelagem podem ser utilizadas. Para o sistema composto de Lisozima, por se tratar de uma proteína amplamente estudada na literatura, é interesante poder comparar os resultados encontrados com os já publicados e observar sua estabilidade em solução. O peso molecular calculado a partir dos dados de espalhamento foi 15kDa, que está em bom acordo com a esperado para esta proteina (14,6 kDa). Além disso, ao variar-se a concentração da proteína em solução, é possível observar um fator de interação entre as partículas para maiores concentrações. Esse fator de interação pode ser considerado próximo ao de esferas rígidas. Para o sistema de Crioglobulinas, houve uma dificuldade na purificação da amostra, mas ainda assim apresentaremos alguns resultados interessantes, em que a técnica de SAXS fornece informações sobre a flexibilidade de proteínas e as análises para as amostras de um pool de imunoglobulinas indicou que com a diminuição da temperatura a dispersão de raios de giro aumenta, indicando a formação de agregados. Para o sistema do Proteassomo, diversas análises se mostraram possível e resultados novos puderam ser obtidos e publicados. Dos estudos utilizando MET,com as micrografias obtidas tem-se a indicação de diferenças na estrutura, quando a molécula está em condições diferentes. Das análises feitas por SAXS, é possível utilizar duas modelagens diferentes, uma simples, outra mais avançada, em que se pode concluir que a redução do Cys-PT glutatiolado induz mudanças conformacionais. Além disso, resultados de SAXS e MET estão em concordância e fornecem informações complementares. / In this work results will be presented on three different protein system: Lysozime, Cryoglobulin and Proteasome, analyzed mainly by Small Angle X-ray scattering technique. Techniques such as transmission electron microscopy and dynamic light scattering were used as complementary techniques. The results show that an unic potential Small Angle X-ray scattering technique around the study of systems in solution. The data correspond to a study of a wide range of sizes for the studied proteins (15kDa to 750 kDa), requiring different approaches in each case. As will be shown for cases where there is a monodisperse system, different modeling methodologies may be used. For the system composed of Lysozyme, because it is a protein widely studied in the literature, it is interesting to compare the results with those already published and observe its stability in solution. The molecular weight calculated from the scattering data was 15kDa, which is in good agreement with the expected for this protein (14.6kDa). Futhermore by varying the concentration of the protein in solution, it is possible to observe a factor of interaction between the particles for higher concentrations. This interaction factor can be considered close to the rigid spheres. For Cryoglobulins system, there was a difficulty in the sample purification, but still present some interesting results, where the SAXS technique provides information on the flexibility of proteins and the analysis for the samples from a pool of immunoglobulin indicated that with decreasing temperature, the dispersion of radius of gyration increases, indicating the formation of aggregates. For the proteasome system, various analyzes have proved possible and new results could be obtained and published. From studies using TEM, with the micrographs we have the indication of differences in the structure, when the molecule is in different conditions. From the analyzes made by SAXS, it is possible to use two different modeling, a simple one, and other more advanced, where it can be concluded that the reduction of the Cys-PT glutathiolated induces conformational changes. Moreover, SAXS and TEM results are in agreement and provide additional information.

Breast cancer is the most common cause of cancer death in Australian women. Current pathological analysis examines a small section of tissue for cellular and plasma abnormalities using a light microscope. However, this method of diagnosis, despite being the current gold standard, has its limitations, where human error and professional experience can influence a patient’s diagnosis. A potential alternative or adjunct to conventional histopathology for classifying tissue disease status is offered by Small Angle X-ray Scattering (SAXS). At the time of commencement of this work, there had been several small scale studies which examined the potential of SAXS to classify the disease status of breast tissue. These tended to focus on the supramolecular structure of collagen fibrils found in the breast, where it is known that the degradation of these fibres is related to the spread of disease. Most previous studies also used a synchrotron as an X-ray source, due to the intense and highly collimated flux available. This study used a synchrotron source, but also evaluated the use of a laboratory X-ray source, as a more convenient and relatively inexpensive alternative that could one day find application in the clinic. The work presented in this thesis analyses the largest cohort of patients and breast tissue samples studied to date using SAXS: 130 patients with 543 tissue samples. Tissues were sourced from surgical waste and classified into four groups: invasive carcinoma, benign, normal, and mammoplasty. Mammoplasty tissue samples were harvested from patients undergoing breast reduction and/or reconstruction, where no history or presence of disease was indicated. Normal tissue was sampled from patients with known disease, but pathological analysis of the tissue core diagnosed it as normal. A comprehensive analysis of the scattering patterns was carried out, analysing features arising from the collagen structure and orientation, the total scattered intensity, and adipose tissue in the breast. Features related to the axial D-spacing of the collagen fibrils within the breast tissue as well as the integrated scattering intensity (called amorphous scatter) demonstrated the highest ability to discriminate tissue types, in SAXS images acquired from both the synchrotron source and the laboratory X-ray source. The amorphous scatter intensities obtained using a synchrotron source showed highly significant differences (p < 0.01) for almost all of the tissue pair comparisons: invasive carcinoma vs. benign, invasive carcinoma vs. normal, invasive carcinoma vs. mammoplasty, benign vs. mammoplasty, and normal vs. mammoplasty. However, no significant difference was seen in the amorphous scatter between benign versus normal tissues (p = 0.30). The amorphous scatter values increased with severity of disease, i.e. it was the highest for invaded tissues and decreased progressively from benign to normal to mammoplasty. There was a significant difference between normal and mammoplasty tissue types using the amorphous scatter as a discriminator (p = 0.0025). Pathological assessment cannot differentiate between these two tissue types, which suggests that there may be changes occurring in these tissue structures at the supramolecular level that can be characterised using SAXS. The ability of SAXS to reveal structural differences between normal and mammoplasty tissue types is highly significant, for both disease diagnosis and treatment, as well as for understanding disease progression. For example, these differences might aid in determining surgical margin clearance of excised breast lesions as well as potentially provide a means of pre-screening or perhaps improve false-negative rates of diagnosis. The potential of SAXS to reveal macroscopic extent and directional spread of disease was explored using two-dimensional mapping of the amorphous scatter. These maps showed broad agreement with histopathological diagnosis, but further investigation regarding their reliability and interpretation for clinical utility is still needed. Changes in both the amorphous scatter and the axial D- spacing were seen in tissue samples up to 6 cm away from the primary site of disease. In particular, a significant decrease in both parameters was seen between the centre of the tumour (at 0 cm) and 2 cm away, suggesting that closer examination of the tissue structures over the disease/healthy tissue border may provide information regarding the mechanisms of metastasis and growth of cancerous tumours. The combination of the amorphous scattering results from the two X-ray sources indicates that the size of the scatterers may be the key in classifying tissue types. The synchrotron source was able to access a lower q-range (q = 0.1-0.6 nm-1) and the laboratory source covered a larger q-range (q = 0.25-2.3 nm-1). Mammoplasty tissues appear to be characterised by large scattering components (d > 25.13 nm), whereas normal tissues are characterised by slightly smaller scattering components (10.47 nm < d < 25.13 nm) and benign tissues by even smaller scattering components (4.83 < d < 10.47 nm). It appears that the size of the scatterers contributing to the total scattering intensity decreases with severity of disease, which was seen independently with both X-ray sources. Further investigation is warranted to determine the biological origin of these differences. These results also suggest that the optimum SAXS instrument may need to cover a scattering vector range of q < 0.25 nm-1 to identify differences in healthy tissue types, and q > 2.3 nm-1 to possibly investigate invasive carcinoma tissue types. A SAXS apparatus that can examine a large q-range may provide all of the necessary information from the amorphous scatter to differentiate between tissue groups. The periodic structure of collagen fibrils along their longitudinal axis can be characterised by the axial D-spacing, where this spacing was found to change with the presence of disease. The axial D-spacing for healthy breast tissues was found to be significantly lower in normal and mammoplasty tissues compared to invaded tissues (p = 0.0050 and p = 0.0093, respectively). However, no significant differences between the other tissue group pairs were seen (p > 0.05). These differences were evident in classification modelling of the four tissue groups, where the amorphous scatter and the amplitude of a collagen axial peak were used to build a probability model for disease status. The model showed high sensitivities (> 70%) and widely variable specificities (ranged from 18-97%) for the data examined with the synchrotron source. This means that the model was a good indicator of disease, but poor at indentifying healthy tissue types. The work presented in this thesis shows that SAXS is capable of distinguishing breast tissue types with high sensitivity and has the potential to become a significant tool for the investigation of cancer progression or even diagnosis. Further investigation into the amorphous scatter and axial D-spacing in particular may provide insight into the biological mechanisms related to tissue degradation associated with invasive disease.

This work represents a small-angle X-ray scattering (SAXS) investigation into the structure of two rather different materials: chemically impregnated activated carbons (IACs) and the nanostructured alloy of tin-cobalt-carbon. Five impregnant species, namely sodium benzoate, potassium biphthalate, zinc chloride, potassium carbonate, and silver nitrate, were impregnated into activated carbon using the incipient wetness or imbibing method to various loadings and examined. Using a modified version of the Kalliat model and a suitable interpretation, two different impregnant behaviours arose: one marked by good chemical dispersion over all classes of carbon pores, the other characterized by a formation of large grains but little deposition in micropores or formation of small grains. A special apparatus was constructed to collect SAXS data of Li-ion coin cells with beryllium windows using a nanostructured SnCoC electrode. When one such cell was charged and discharged, the entry and exit of lithium atoms into the SnCoC material caused structural deformations, which were visible in SAXS data through the use of the modified Kalliat model. The size of the SnCo grains changed as lithium was inserted and removed from the SnCoC electrode. However, when the cell voltage was less than 0.2 V the SnCo grain size was constant, suggesting lithium insertion and removal below 0.2 V was occurring in the carbon matrix.

Mediante a técnica de espalhamento de raio-X a baixos ângulos por macromoléculas em solução, estudou-se as variações de forma e tamanho da crotamina, proteína básica e neurotóxica do veneno das cascavéis (crotalus durissus terrificus), em diferentes condições de pH e uma concentração de 10% visando a determinação dos valores do raio de giro. Este raio, RG, é definido como RG = (&#8747vr2 &#961 r&#963; dv&#963;) 1 &#8260 2 onde v é o volume da macromolécula, r o módulo do vetor posição r&#963 com origem no centro de massa, &#961 (r&#963) a densidade eletrônica e n o número de elétrons da macromolécula. Este parâmetro não conduz obviamente ao conhecimento completo da estrutura da macromolécula, mas a sua determinação possibilita estudo de variações conformacionais de forma relativamente simples em sistemas com condições semelhantes às biológicas. Os valores do raio de giro foram determinados mediante gráficos de Guinier (Log JN(s) vs s2, onde s é o módulo do vetor posição do espaço recíproco e JN(s) a intensidade normalizada e livre de espalhamento parasita). Preliminarmente, foi feito um estudo com oxi-hemoglobina, Insulina e hemoglobina de caramujo, por apresentarem características semelhantes às da crotamina, isto é, serem do tipo globular e de forma aproximadamente esférica com o objetivo de familiarizar-se com a técnica experimental e testar a aparelhagem. Os valores de raio de giro deduzidos para a oxi-hemoglobina RGOX= 23.9 &#177 0.7 (A &#176), Insulina RGI= 18.4 &#177 0.5 (A &#176), e hemoglobina de caramujo RGhc= 92 &#177 2 (A&#176), concordam satisfatoriamente com resultados previamente encontrados na literatura. Os valores de raio de giro medido para as diferentes soluções de crotamina encontram-se em bom acordo com a teoria e com o valor do raio de giro esperado de crotamina REC= 9.7 A&#176 / The small angle x-ray scattering technique was used in order to determine the radius of gyration of crotamine, a basic and neurotoxic protein from rattle snake venom, in 10% solutions at different PHs. The radius of gryration, RG is defined as: RG = (&#8747vr2 &#961 r&#963; e dv&#963;) 1 &#8260 2 Where: v is the volume of the macromolecule, r is the modulus of the position vector r with origin at the center of mass, &#961 (r&#963) is the electronic density and n the number of electrons of the macromolecule. This parameter does not give a complete information about the structure of the macromolecule but it is possible to get information about conformation to close to the biological ones. The values of the radius of gyration were fdetermined by means of the Guinier graphics (Log JN(s) vs s2, where s is the magnitude of the scattering vetor and JN(s) is the normalized intensity. In order to get familiar wi th the experimental technique and to test the equipment the study of oxihaemoglobin, Insulin and sea-mail hemoglobin was done. This proteins are very similar to crotamine in the sense that they are globular type and almost of the same spherical shape. The values of the radius of gyration obtained agree very well with the reported ones: Oxihaemoglobin RGOX= 23.9 &#177 0.7 (A &#176), Insulin RGI= 18.4 &#177 0.5 (A &#176), and sea-mail hemoglobin RGhc= 92 &#177 2 (A&#176). The values od the radius of gyration measured for the different solution of crotamine are in good agreement with the calculated and with the expected value REC= 9.7 A&#176

Este trabalho teve por objetivo o preparo e estudo das propriedades de vidros fotocrômicos. Foram preparados vidros de aluminoborosilicatos de potássio (40\'SI\'\'O IND. 2\'.10\'AL IND. 2\'\'O IND. 3\'.(50-x)\'B IND. 2\'\'O IND. 3\'.X\'K IND. 2\'\'O\'- 14,9 < x < 17,7) dopados com \'AG\'\'CL\' e \'CU POT. 2+\'. As amostras foram fundidas em cadinho de platina, em forno de elementos resistivos de \'SI\'\'C\', a \'1400 GRAUS\'C por duas horas, sendo derramados sobre molde de aço inoxidável. Uma tentativa de análise química quantitativa dos componentes após a fusão foi feita por Retroespalhamento de Rutherford. A proporção de prata retida no vidro foi determinada por este método. Medidas de dilatometria e densidade foram feitas para amostras de composição base diferentes. As medidas de dilatometria permitem a obtenção do coeficiente de dilatação térmica, e os parâmetros típicos de vidros conhecidos como: temperatura de transição vítrea e temperatura de \"softening dilatométrico\". Tratamentos térmicos em temperaturas próximas do ponto de amolecimento (softening point) provocam a precipitação de partículas coloidais de \'AG\'\'CL\' na matriz vítrea. Estas são responsáveis pelo comportamento fotocrômico dos vidros. Fatias de uma amostra foram submetidas a programas de tratamento térmico de 0,5 h a várias temperaturas entre \'480 GRAUS\'C e \'620 GRAUS\'C e programas de vários intervalos de tempo entre 0,25 e 1,25h a \'600 GRAUS\'C. As propriedades de absorção óptica das várias fatias, antes e depois de exposição à luz UV, foram comparadas. As características morfológicas das partículas coloidais de \'AG\'\'CL\' produzidas pelos tratamentos térmicos foram investigadas por SAXS. Os raios R das partículas mostraram uma relação linear com a temperatura para tratamentos de 0,5 h entre 550 e \'620 GRAUS\'C e uma relação linear de \'R POT. 3\' com o tempo de tratamento a \'600 GRAUS\'C. Duas séries de amostras foram preparadas para estudar: 1. a influência da quantidade de cobre 2. a influência da proporção de \'K IND. 2\'\'O\' em relação a \'B IND. 2\'\'O IND. 3\'. As propriedades de absorção óptica (antes e depois de exposição à luz UV) das amostras das duas séries, submetidas a tratamentos térmicos a \'600 GRAUS\'C por diversos tempos entre 0,25 e 1,6 h foram comparadas. / The purpose of the present work was to prepare and study the properties of photochromic glasses. Potassium aluminoborosilicate glasses (40\'SI\'\'O IND. 2\'.10\'AL IND. 2\'\'O IND. 3\'.(50-x)\'B IND. 2\'\'O IND. 3\'.X\'K IND. 2\'\'O\'- 14,9 < x < 17,7) doped with \'AG\'\'CL\' and \'CU POT. 2+\' were prepared. The samples were melted in platinum crucible, in electric furnace with silicon carbide resistences, at \'1400 GRAUS\'C for two hours, and poured on stainless steel mold. An attempt to perform a quantitative chemical analisis of the components after melting was carried out by Rutherford Backscattering method. The amount of silver incorporated into the glass was determined by this method. Measurements of dilatometry and density were performed for samples of different base composition. The dilatometric measurements give the thermal expansion coefficient, and the typical glass parameters such as glass transition point and dilatometric softening point. Thermal treatments at temperatures near the softening point precipitate colloidal \'AG\'\'CL\' particles in the glass matrix. These particles are responsible for the photochromic characteristics of the glass. Slices of a sample were submitted to thermal treatments for 0.5 hours at temperatures between 480 and \'620 GRAUS\'C and treatments at \'600 GRAUS\'C for several) time intervals between 0.25 and 1.25 hours. The optical absorption properties of these slices, before and after UV light exposure, were compared. The morphological aspects of the \'AG\'\'CL\' coloidal particles were investigated by SAXS. The particle radii R presented a linear relation with the temperature for treatments for 0.5 hour at temperatures between 550 and \'620 GRAUS\'C and a linear relation of \'R POT. 3\' with time for treatments at \'600 GRAUS\'C. Two sample series were prepared to investigate: 1. the influence of the amount of copper 2. the influence of the amount of \'K IND. 2\'\'O\' in relation to the amout of \'B IND. 2\'\'O IND. 3\' The optical absorbances (before and after exposure to UV light) for samples of the two series, annealed at \'600 GRAUS\'C for different times between 0.25 and 1.6 hours were compared.

Foram estudadas fases micelares do sistema lauril (dodecil) sulfato de sodio (sls)/agua/decanol nos estados isotropico i e liquido-cristalino por espalhamento de raios-x com enfase nas transicoes de fase iSETAhexagonal hALFA e iSETAnematica nc. O estudo das posicoes do pico intermicelar no sistema binario sls/agua, indica que as micelas sao estaveis e levemente anisometricas nas fases i concentradas com empacotamento local de micelas esferoidais. Ocorre crescimento micelar na vizinhanca da transicao iSETAhALFA. A analise da curva de espalhamento i (q) em concentracoes menores (ate 9% em peso de sls) mostra ser possivel a determinacao da funcao distribuicao de distancias p (r), em casos especificos onde i (q) e dominada por um pico predominantemente relacionado a estrutura interna micelar. As anisometrias micelares NI sao deduzidas dos valores de dmax sendo p (r)=0 para r> OU =dmax obtemos NIAPROXIMADAMENTE IGUAL1.5. A analise das curvas de espalhamento de solucoes mais concentradas evidenciam que as micelas crescem mais por adicao de decanol ao longo da transicao de fase iSETAnc (NIAPROXIMADA MENTE IGUAL3) do que por aumento de concentracao de anfifilico no sistema binario ao longo de iSETAhALFA (NIAPROXIMADAMENTE IGUAL2,4). Estes resultados sao discutidos no ambito de previsoes teoricas recentes de transicoes de fase iSETAliquido-cristalinas / Micellar phases of the system sodium dodecyl sulfate (SLS)/water/decanol have been studied by X-ray scattering in isotropic I and liquid crystalline states, with emphasis on the 1-+hexagonal Ha and 1nematic Nc phase transitions. Study of the intermicellar peak position in the binary SIS/water system, taking into account relative volumes of amphiphile, shows that micelles are stable and slightly anisometric in concentrated I phases, with local close packing of spheroidal micelles. Micellar growth occurs only near the 1Ha transition. Analysis of the scattering curve I( q) for lower concentrations (up to 9 wt% SLS) shows that it is possible to obtain the distance distribution function p(r), in specific cases in which l(q) is dominated by a peak due to the inner micellar structure. Micellar anisometries v are deduced from Dmax values, with p(r)=O for r Dmax. It results v.: 1.5. The electron density distribution p(r) obtained from p(r) in these lower concentrations confirm the existence of micellar anisometry.

Septinas fazem parte de uma família de proteínas de ligação ao nucleotídeo guanina que atuam no ciclo de divisão celular e também são amplamente encontradas em doenças neurodegenerativas tais como mal de Parkinson e Alzheimer e em alguns tipos de câncer como leucemia, linfoma e tumores sólidos. Neste trabalho investigamos como a temperatura e a concentração impactam na agregação do domínio GTPase da septina 2 (SEPT2G), podendo levar a formação de bras amilóides, por espalhamento de luz (DLS) e Raios-X a baixos ângulos (SAXS). Resultados de DLS revelaram que a cinética de agregação da proteína é da ordem de segundos para temperaturas maiores que 25ºC. Os dados de SAXS da proteina a 0,5 mg/ml mostraram que a SETP2G é um dímero em solução aquosa a 4ºC e esta conguração se mantém estável por cerca de 1 hora de observação experimental. A 15ºC, os resultados de SAXS revelaram uma coexistência de três populações em solução compostas por 88% de dímeros, 10% de agregados pequenos tipo-cilindros (protobrilas), e 2% de agregados grandes maiores que a resolução da técnica. Após cerca de 30 minutos existe um rearranjo preferencial de dímeros em favor de agregados muito grandes cuja contribuição à curva de espalhamento torna-se 8%. A 25ºC, a porcentagem de dímeros decresce para 70% com uma contribuição de cerca de 30% de agregados grandes já no início das medidas experimentais. Nas temperaturas de 37ºC e 45ºC, dímeros e agregados muito grandes coexistem em solução desde o início das medidas experimentais, cujo equilíbrio se desloca rapidamente tal que após 20 minutos de observação a solução é composta majoritariamente por agregados muito grandes, identicados como estruturas amilóides pela técnica de uorescência da tioavina, que se intercala em estruturas cross-. A 1 mg/mL e temperatura de 4ºC, a proteína permaneceu estável durante cerca de 1 hora de observação sendo que existe um equilíbrio de dímeros (93%) com agregados alongados (contendo cerca de 80 monômeros) em solução. Com o aumento da temperatura para 15ºC, a maioria da população ainda é dimérica. Já a 25ºC, a presença de agregados muito grandes é bem significativa (da ordem de 30% coexistindo com dímeros e oligômeros). A 37ºC e 45ºC existe a formação de grandes agregados similar ao observado para a SEPT2G a 0,5 mg/mL. Em suma, os resultados de SAXS demonstraram que a SEPT2G tem uma cinética muito rápida de agregação a temperatura siológica, acentuada com o aumento de concentração da proteína em solução. / Septins are proteins from the GTP-binding family and participate in cell division cycle performing functions such as secretion and cytoskeletal division. They can also be found in neurodegenerative conditions as Alzheimer\'s and Parkinson\'s diseases and some kinds of cancer as leukemia, lymphoma and solid tumors. In this work, we investigated the influence of temperature and concentration on the septin 2 GTPase domain (SEPT2G) aggregation using dynamic light scattering (DLS) and small angle x-ray scattering (SAXS). DLS results revealed the protein aggregation kinetic is around seconds for temperatures above 25ºC. SAXS data of the protein at 0.5 mg/mL showed that SEPT2G is a dimer in aqueous solution at 4_C and this condition is kept stable for approximately one hour of experimental observation. At 15ºC, SAXS results revealed the coexistence of three populations in solution composed by 88% of dimers, 10% of cylinder-like smaller aggregates (protofibrils) and 2% of aggregates bigger than the technique detection. After 30 minutes there is a preferential rearrangement of dimers into very large aggregates which contribution on the scattering curve becomes 8%. At 25ºC, the dimers percentage decreases to 70% with a contribution of circa 30% of bigger aggregates, even at the beginning of data acquisition. At temperatures of 37ºC and 45ºC, dimers and very large aggregates coexist in solution since the beginning of data acquisition, which equilibrium quickly shifts in such a way that after 20 minutes of observation the solution is mostly composed by very large aggregates, indented as amyloid structures by the thioflavine fluorescence technique, which intercalates in the cross- structures. At 1 mg/mL and 4ºC, the protein was stable over 1 hour of observation where an equilibrium of dimers (93%) and elongated structures (composed by approximately 80 monomers) in solution takes place. Increasing the temperature to 15ºC, most of the protein remains dimeric. On the other hand, at 25ºC the very large aggregates contribution is around 30% coexisting with dimers and oligomers. At 37ºC and 45ºC there is the formation of large aggregates, similar to what was observed at 0.5 mg/mL. In conclusion, our SAXS results indicated that the aggregation process of SEPT2G in solution may follow different pathways depending on concentration and temperature.

Foram estudadas fases micelares do sistema lauril (dodecil) sulfato de sodio (sls)/agua/decanol nos estados isotropico i e liquido-cristalino por espalhamento de raios-x com enfase nas transicoes de fase iSETAhexagonal hALFA e iSETAnematica nc. O estudo das posicoes do pico intermicelar no sistema binario sls/agua, indica que as micelas sao estaveis e levemente anisometricas nas fases i concentradas com empacotamento local de micelas esferoidais. Ocorre crescimento micelar na vizinhanca da transicao iSETAhALFA. A analise da curva de espalhamento i (q) em concentracoes menores (ate 9% em peso de sls) mostra ser possivel a determinacao da funcao distribuicao de distancias p (r), em casos especificos onde i (q) e dominada por um pico predominantemente relacionado a estrutura interna micelar. As anisometrias micelares NI sao deduzidas dos valores de dmax sendo p (r)=0 para r> OU =dmax obtemos NIAPROXIMADAMENTE IGUAL1.5. A analise das curvas de espalhamento de solucoes mais concentradas evidenciam que as micelas crescem mais por adicao de decanol ao longo da transicao de fase iSETAnc (NIAPROXIMADA MENTE IGUAL3) do que por aumento de concentracao de anfifilico no sistema binario ao longo de iSETAhALFA (NIAPROXIMADAMENTE IGUAL2,4). Estes resultados sao discutidos no ambito de previsoes teoricas recentes de transicoes de fase iSETAliquido-cristalinas / Micellar phases of the system sodium dodecyl sulfate (SLS)/water/decanol have been studied by X-ray scattering in isotropic I and liquid crystalline states, with emphasis on the 1-+hexagonal Ha and 1nematic Nc phase transitions. Study of the intermicellar peak position in the binary SIS/water system, taking into account relative volumes of amphiphile, shows that micelles are stable and slightly anisometric in concentrated I phases, with local close packing of spheroidal micelles. Micellar growth occurs only near the 1Ha transition. Analysis of the scattering curve I( q) for lower concentrations (up to 9 wt% SLS) shows that it is possible to obtain the distance distribution function p(r), in specific cases in which l(q) is dominated by a peak due to the inner micellar structure. Micellar anisometries v are deduced from Dmax values, with p(r)=O for r Dmax. It results v.: 1.5. The electron density distribution p(r) obtained from p(r) in these lower concentrations confirm the existence of micellar anisometry.

Mediante a técnica de espalhamento de raio-X a baixos ângulos por macromoléculas em solução, estudou-se as variações de forma e tamanho da crotamina, proteína básica e neurotóxica do veneno das cascavéis (crotalus durissus terrificus), em diferentes condições de pH e uma concentração de 10% visando a determinação dos valores do raio de giro. Este raio, RG, é definido como RG = (&#8747vr2 &#961 r&#963; dv&#963;) 1 &#8260 2 onde v é o volume da macromolécula, r o módulo do vetor posição r&#963 com origem no centro de massa, &#961 (r&#963) a densidade eletrônica e n o número de elétrons da macromolécula. Este parâmetro não conduz obviamente ao conhecimento completo da estrutura da macromolécula, mas a sua determinação possibilita estudo de variações conformacionais de forma relativamente simples em sistemas com condições semelhantes às biológicas. Os valores do raio de giro foram determinados mediante gráficos de Guinier (Log JN(s) vs s2, onde s é o módulo do vetor posição do espaço recíproco e JN(s) a intensidade normalizada e livre de espalhamento parasita). Preliminarmente, foi feito um estudo com oxi-hemoglobina, Insulina e hemoglobina de caramujo, por apresentarem características semelhantes às da crotamina, isto é, serem do tipo globular e de forma aproximadamente esférica com o objetivo de familiarizar-se com a técnica experimental e testar a aparelhagem. Os valores de raio de giro deduzidos para a oxi-hemoglobina RGOX= 23.9 &#177 0.7 (A &#176), Insulina RGI= 18.4 &#177 0.5 (A &#176), e hemoglobina de caramujo RGhc= 92 &#177 2 (A&#176), concordam satisfatoriamente com resultados previamente encontrados na literatura. Os valores de raio de giro medido para as diferentes soluções de crotamina encontram-se em bom acordo com a teoria e com o valor do raio de giro esperado de crotamina REC= 9.7 A&#176 / The small angle x-ray scattering technique was used in order to determine the radius of gyration of crotamine, a basic and neurotoxic protein from rattle snake venom, in 10% solutions at different PHs. The radius of gryration, RG is defined as: RG = (&#8747vr2 &#961 r&#963; e dv&#963;) 1 &#8260 2 Where: v is the volume of the macromolecule, r is the modulus of the position vector r with origin at the center of mass, &#961 (r&#963) is the electronic density and n the number of electrons of the macromolecule. This parameter does not give a complete information about the structure of the macromolecule but it is possible to get information about conformation to close to the biological ones. The values of the radius of gyration were fdetermined by means of the Guinier graphics (Log JN(s) vs s2, where s is the magnitude of the scattering vetor and JN(s) is the normalized intensity. In order to get familiar wi th the experimental technique and to test the equipment the study of oxihaemoglobin, Insulin and sea-mail hemoglobin was done. This proteins are very similar to crotamine in the sense that they are globular type and almost of the same spherical shape. The values of the radius of gyration obtained agree very well with the reported ones: Oxihaemoglobin RGOX= 23.9 &#177 0.7 (A &#176), Insulin RGI= 18.4 &#177 0.5 (A &#176), and sea-mail hemoglobin RGhc= 92 &#177 2 (A&#176). The values od the radius of gyration measured for the different solution of crotamine are in good agreement with the calculated and with the expected value REC= 9.7 A&#176