<p>Microorganisms mediate many biogeochemical processes critical to the functioning of ecosystems, which places them as an intermediate between environmental change and the resulting ecosystem response. Yet, we have an incomplete understanding of these relationships, how to predict them, and when they are influential. Understanding these dynamics will inform ecological principles developed for macroorganisms and aid expectations for microbial responses to new gradients. To address this research goal, I used two studies of environmental gradients and a literature synthesis.</p><p>With the gradient studies, I assessed microbial community composition in stream biofilms across a gradient of alkaline mine drainage. I used multivariate approaches to examine changes in the non-eukaryote microbial community composition of taxa (chapter 2) and functional genes (chapter 3). I found that stream biofilms at sites receiving alkaline mine drainage had distinct community composition and also differed in the composition of functional gene groups compared with unmined reference sites. Compositional shifts were not dominated by groups that could benefit from mining associated increases of terminal electron acceptors; two-thirds of responsive taxa and functional gene groups were negatively associated with mining. The majority of subsidies and stressors (nitrate, sulfate, conductivity) had no consistent relationships with taxa or gene abundances. However, methane metabolism genes were less abundant at mined sites and there was a strong, positive correlation between selenate reductase gene abundance and mining-associated selenium. These results highlighted the potential for indirect factors to also play an important role in explaining compositional shifts.</p><p>In the fourth chapter, I synthesized studies that use environmental perturbations to explore microbial community structure and microbial process connections. I examined nine journals (2009–13) and found that many qualifying papers (112 of 148) documented structure and process responses, but few (38 of 112 papers) reported statistically testing for a link. Of these tested links, 75% were significant. No particular approach for characterizing structure or processes was more likely to produce significant links. Process responses were detected earlier on average than responses in structure. Together, the findings suggested that few publications report statistically testing structure-process links; but when tested, links often occurred yet shared few commonalities in linked processes or structures and the techniques used for measuring them. </p><p>Although the research community has made progress, much work remains to ensure that the vast and growing wealth of microbial informatics data is translated into useful ecological information. In part, this challenge can be approached through using hypotheses to guide analyses, but also by being open to opportunities for hypothesis generation. The results from my dissertation work advise that it is important to carefully interpret shifts in community composition in relation to abiotic characteristics and recommend considering ecological, thermodynamic, and kinetic principles to understand the properties governing community responses to environmental perturbation.</p> / Dissertation

La réaction de serpentinisation résulte de l’interaction de l’eau de mer, ou de fluides hydrothermaux avec les roches mantelliques. Elle engendre des changements des propriétés chimiques de la lithosphère océanique, avec notamment un enrichissement en éléments mobiles (ex. As, Sb, Li, Cs, Pb, et B). Ces éléments sont importants en sciences de la terre car ce sont des traceurs géochimiques des interactions fluides-roches depuis la ride océanique jusqu’aux zones de subduction. Ce travail de thèse a pour but de caractériser le partitionnement de certains éléments mobiles entre un fluide et la serpentine de manière expérimentale. Pour cela, j’ai développé deux protocoles expérimentaux en condition alcaline. Le premier, consiste en la synthèse de chrysotile à partir d’un gel à la stoechiométrie de la serpentine, à 300 °C et Psat. Pour le second protocole, la serpentine est obtenue par altération de grains d’olivine San Carlos (granulométrie : <30 µm, 30-56 µm, >56 µm) à 200 °C (Psat) pour 1M de NaOH et en présence de carbonate (HCO3-). La minéralogie des produits expérimentaux ainsi que leurs abondances ont été déterminées par diffraction des rayons-X, spectroscopie infrarouge et analyse thermogravimétrique. Les propriétés texturales ont été caractérisées par microscopie électronique à balayage et à transmission haute résolution. La composition du produit solide a été mesurée par spectrométrie de masse et analyse par microsonde-électronique et l’état d’oxydo-réduction du fer a été déterminé par analyses Mössbauer. Des analyses d’absorption des rayons-X (XAS) ont été effectuées afin d’analyser la structure locale de l’antimoine et de l’arsenic. La combinaison de ces techniques analytiques a permis de montrer que la synthèse de chrysotile est effective après seulement 8 heures de réaction. A 200°C, l’olivine est remplacée (pseudomorphose) par le chrysotile et la brucite. Le remplacement est total après 1 mois (<30 µm) et 3 mois (30 et 56 µm). En présence de carbonate, l’altération de l’olivine est caractérisée par une cinétique plus lente et est contrôlée par la précipitation de la magnésite et de la lizardite.En reprenant les 2 protocoles expérimentaux de synthèse de chrysotile (1M NaOH), et en dopant le fluide en un élément trace (Li, As, Cs, Sb et B) le partitionnement des éléments mobiles a pu être étudié. Le coefficient de partage solide-fluide (KD) a pu être défini pour chaque élément durant la synthèse du chrysotile à 300 °C en modélisant nos résultats suivant l’équation de Langmuir (concentrations en solution de 5 à 1000 µg g-1). La séquence obtenue pour les coefficients de partage est la suivante : 0.5<B < As < Li < Cs < Sb<9. En présence de lithium, d’arsenic et d’antimoine, la morphologie du chrysotile atteste d’une croissance radiale. En revanche, le bore favorise une croissance en longueur du chrysotile perpendiculaire à l’axe c. Un mécanisme d’adsorption contrôle principalement la séquestration des éléments mobiles par le chrysotile comme l’indiquent les résultats d’absorption des rayons-X sur l’arsenic et l’antimoine. Lors de l’altération des olivines, la séquestration des éléments trace est hétérogène et le changement des conditions d’oxydo-réduction du système durant la réaction de serpentinisation explique les changements dans la séquestration de l’antimoine d’abord adsorbé sous sa forme pentavalente puis incorporé sous sa forme trivalente par des phases secondaires. Même en faible concentration en solution (200 µg g-1), le lithium a un fort pouvoir catalytique sur la réaction de serpentinisation de l’olivine à 200 °C.En perspective plusieurs expériences haute pression et température (450 °C et 1-4 kbar) ont été réalisées afin de mieux comprendre le comportement des éléments traces durant les transitions de phase et la déstabilisation de la serpentine en contexte de subduction. Les résultats préliminaires indiquent que la présence de ces éléments traces a un rôle très important sur la stabilité du chrysotile. / Serpentinization reaction is the result of the interaction of seawater with mantle rocks especially at slow-spreading ridges. The formation of serpentinite during this alteration reaction changes the physico-chemical properties of the oceanic lithosphere and induces an enrichment in Fluid-mobile elements (FME: e.g. As, Sb, Li, Cs, Pb and B) compared to primary minerals. These elements are efficient geochemical tracers reflecting mantle hydration from the oceanic ridge to subduction environments. In this context, there is a lack of data concerning the partitioning and sequestration processes of FME between serpentine and fluids. The aim of this thesis is to determine fluid/serpentine partition coefficients of these elements as well as their effects on serpentine formation (reaction mechanism and kinetics, textural properties etc.). To achieve this goal, serpentine has been synthesized under highly alkaline hydrothermal conditions using two distinct protocols. Experimental-products were characterized using X-ray powder diffraction (XRPD), Fourier Transform Infra-Red spectroscopy (FTIR), N2 sorption isotherms, ThermoGravimetric Analyses (TGA), Field Emission gun Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), X-ray Absorption Spectroscopy (XAS) and Mössbauer Spectroscopy. The first protocol consists in chrysotile synthesis from H2SiO3 and MgCl2 at 300 °C using batch and semi-continuous experiments. With this approach, we were able to chrarcterized chrysotile nanotubes nucleation and growth processes. In the second protocol, we investigated olivine serpentinization reaction under high hydroxyl-alkalinity or high carbonate-alkalinity at 200 °C. We note the efficiency of serpentine formation under high alkaline conditions in the both protocols and the significant effect of the carbonate component on the serpentinization processes and crystal growth rates. The serpentinization of olivine under alkaline conditions induces the oxidation of a large part of iron trapped by brucite.Replacement is total after 1 month (<30 µm) and 3 month (30-56 µm). The presence of a carbonate component induces a lower reaction kinetic and is characterized by the co-precipitation of magnesite and lizardite.Based on these results, we chose favorable conditions in order to study FME (Li, As, Cs, Sb and B) sequestration. Solid-liquid partitioning for each FME was investigated during chrysotile synthesis at 300°C. Experimental results were modeled using the Langmuir equation and the role of each element on chrysotile textural properties was investigated. In addition, we report new results concerning the sequestration and the distribution of the trace elements during olivine replacement by serpentine and brucite. We highlight that Li act as a catalyst during olivine serpentinisation. Moreover, from XAS measurements, we indicate that Sb and As sequestration is dominated by adsorption mechanism. The precipitation of secondary As- and Sb-bearing phases was also revealed by Electron Microprobe X-ray mapping. Finally, Sb-trapping within chrysotile tubes was also suspected by HRTEM measurements. The changes of redox conditions during serpentinisation induce a change of Sb sequestration mechanism and the precipitation of Sb-bearing phases. In addition, we investigate the partitioning of FME at higher pressure (1-4 kbar) and temperature (450 °C). This pilot study brings promising results regarding the behavior of trace elements during serpentine destabilization (deep lithosphere or subduction contexts) and on the non-negligible role of trace elements on the stability of chrysotile.

This thesis presents two new algorithms for doing constrained Magnetotelluric (MT) inversion based on an existing Occam 2D inversion program. The first algorithm includes borehole resistivity logs as prior information to constrain resistivity directly in the vicinity of boreholes. The second algorithm uses reflection seismic data as prior constraints to transfer structural information from seismic images to 2D resistivity models. These two algorithms are efficient (proved through tests of synthetic examples) and widely applicable. In this thesis, they have been successfully applied to the COSC (Collisional Orogeny in the Scandinavian Caledonides) MT data. The COSC project aims to study the mountain belt dynamics in central Sweden by drilling two 2.5 km deep boreholes. MT data were collected to locate the main décollement that separates the overlying Caledonian allochthons and the underlying Precambrian basement, as the main décollement is associated with very conductive Alum shale. The previous interpretation based on part of the COSC seismic profile (CSP) was that the main décollement was located along a reflection with depth of 4.5 km underneath Åre and ~3 km underneath Mörsil, in central Jämtland. The MT resistivity model reveals a very conductive layer in the central and western parts of the profile, the top of which coincides with the first seismic reflection. This means that the first conductive alum shale layer occurs at less than 1 km depth, supporting a new interpretation of the main décollement at shallower depth. In a re-interpretation of the CSP data based on the MT model, the main décollement occurs a few hundred metres below the top of the conductor and is coincident with a laterally continuous seismic reflection. Further, the overlying seismic reflections resemble imbricated alum shale of the Lower Allochthon. MT inversion using seismic constraints from CSP gives further support to the new interpretation. Moreover, MT investigations were conducted in the Alnö alkaline and carbonatite ring-intrusion complex in Sweden. 2D and 3D resistivity models inverted from MT data together with resistivity and porosity laboratory measurements delineate a fossil magma chamber as a resistive anomaly surrounded by electrically conductive up-doming and ring-shaped faults and fractures.

The Mont Saint-Hilaire alkaline complex, Québec, is a Cretaceous rift-related intrusion comprising two gabbroic suites and the East Hill suite, an assemblage of several distinct nepheline syenites and evolved syenitic rocks. Whole-rock analysis of the East Hill suite reveals two fractionation trends, one which is described by the syenitic lithologies and one by the evolved syenites and syenoids. A lamprophyric unit stands on its own, geochemically, consistent with typical lamprophyre petrogenesis. Whole-rock geochemistry of the East Hill suite shows moderate silica content but highly alkaline rocks, enriched in Mn, Zn, Zr, Y, and Ce. Chlorine and sulfur are important and present in abundant secondary sodalite and pervasive microsulfides. Mineral geochemistry indicates decreasing oxygen fugacity with cooling, and phases such as titanite (present) and aenigmatite (absent) defined boundaries in fO2 – T space. Oxygen fugacity data combined with petrography and geothermometry defined an 2 fO – T curve for the East Hill suite magma, revealing that the oxygen fugacity ranged between approximately 10-10 bar at intrusion down to 10-25 bar subsolidus, and that, owing to non-linearity of oxygen buffers, the 2 fO – T path crossed below QFM early, went above QFM late in the crystallization history and then above HM with cooling. A similar procedure applied to sulfur fugacity generated a trend of initial increase from about 10-4 to 10-2 bar followed by decreasing sulfur fugacity with cooling down to approximately 10-8 bar. The oxygen trend implies that earlier suggestions that oxidation of iron drove the evolution of pyroxenes towards aegirine are incorrect. Textural evidence of abundant alteration and secondary mineralization suggests subsolidus action of alkaline fluids. Contrary to previous studies, most sodalite in the East Hill suite is not primary but is the product of reaction of nepheline with chloride-rich fluids after crystallization. Sodalite pseudomorphs continued to react with these fluids, whose chemistry changed with time to silica- then carbonate-rich, resulting in further reactions that led to natrolite and dawsonite deposition, accompanied by late-stage rhodochrosite. It is hypothesized that the silica- and carbonate-rich phase of these fluids caused the decomposition of a melilite groundmass in the lamprophyre to a natrolite-calcite assemblage.

Le Complexe de Jacupiranga (Cajati, SP) est l’une de plusieurs occurrences alcalines du Méso-Cénozoïque situées aux bords de la bassin de Paraná, dans la région sud-est de la Plate-forme Sud-Américaine. Cette unité présente une grande variété de roches: dunites, wehrlites, clinopyroxènites, roches de la série ijolitique, diorite, syénite, monzonite, phonolites, lamprophyres et carbonatites. Considérant que les carbonatites ont été largement étudiés au cours des dernières décennies, grâce à l’importance de sa minéralisation en phosphate, les roches silicatées ont été très peu étudiées. Cette étude présente des nouvelles données géochronologiques, de chimie minérale, de géochimie et isotopique pour le Complexe Jacupiranga, visant à mieux comprendre l'origine et l'évolution de l'unité. Âge argon des différents lithotypes varient entre 133,7±0,5 Ma et 131,9±0,5 Ma, tandis que l’âge obtenu par U-Pb au zircon est de 134,9±0,65 Ma, indiquant que la mise en place de l'unité a été contemporaine à l’extrusion de tholéiites de la Province Magmatique du Paraná. Bien qu'il ne soit pas possible de définir une séquence de mise en place parmi la clinopyroxenite, la diorite et le lamprophyre, la monzonite présente l’âges argon et U-Pb plus âgés que les autres roches. Deux séries magmatiques sont proposées pour les roches silicatées, compte tenu de leurs compositions chimiques: (1) une série fortement sous-saturé en silice, éventuellement lié à un magma parental de composition néphélinitique et (2) une deuxième série modérément sous-saturé, lié à des magmas basanitiques. Les lamprophyres sont considérés représentatifs du magma basanitique. La composition du liquide calculé en équilibre avec les coeurs de la diopside aux clinopyroxénites est similaire aux lamprophyres, ce qui indique qu'une partie des clinopyroxénites est associée au magma basanitique. Monzonite et meladiorite présentent les caractéristiques pétrographiques, compositionnelle et isotopique (87Sr/86Sri: 0,705979 à 0,706086; 143Nd/144Ndi: 0,511945 à 0,512089) qui suggèrent le processus d'assimilation crustale, bien que de caractère local et limité à certains impulsions de magma basanitique. Les carbonatites ont des rapports isotopiques (Nd et Pb) et composition trace (e.g. Ba/La, Nb/Ta) qui exclurent un lien avec les roches silicatées par immiscibilité de liquide. Il est proposé deux scénarios: un magma carbonatitique primaire, généré directement par la fusion du manteau, ou un magma secondaire généré par l’immiscibilité d'un composant silicaté encore inconnu dans l'unité. Données Nd-Sr-Pb-Hf indiquent une contribution importante du manteau lithosphérique subcontinental dans la genèse des roches du complexe. Les lamprophyres et le liquide calculé en équilibre avec le clinopyroxène ont des rapports CaO/Al2O3 et La/Zr relativement élevés et faible Ti/Eu, ce qui indique un manteau lithosphérique métasomatisé par des fluides riches en CO2 et les mécanismes de fusion "vein-plus-wall-rock". Les différences de composition entre ces liquides sont interprétés comme comme résultant du mélange entre la fusion des veines métasomatiques avec la fusion des péridotites, ainsi des proportions différentes de clinopyroxène/grenade à la source. Les variations dans les valeurs ΔεHf suggèrent que le magma basanitique represente une contribution plus grande des vein wehrlitique, tandis que le magma nephelinitiquea été être généré à partir des contributions un peu plus important des peridotites, bien que les deux fluides sont enrichis. Appauvrissement en Nb, Yb, enrichissement en ETR lèger pour rapport le lourdes et l'enrichissement en Cs, Rb et Sr dans les lamprophyres réactions suggèrent que les reactions métasomatiques à la source mantellique ont été associées aux fluides dérivés de processus de subduction. Les âges modèles TDM indiquent l'hétérogénéité à la source et sont compatibles avec les valeurs généralement obtenues pour les occurrences alcalines au du Sud-Est de la Plate-forme Sud-Américaine. / The Jacupiranga Complex (Cajati, SP) is one of several Meso-Cenozoic alkaline units intrusive along the Parana Basin margins, in the Central-Southeastern part of the South American Platform. This unit comprises a large variety of lithotypes: dunites, whehrlites, clinopyroxenites, rocks from the ijolite series, diorites, syenites, manzonites, phonolites, lamprophyres, and carbonatites. While carbonatites have been extensively investigated over the last decades, as they host an important phosphate ore deposit, little attention has been paid to the silicate rocks. The current study presents new geochronological, mineralogical, geochemical, and isotopic data on the Jacupiranga Complex, in order to better understand the origin and evolution of the unit. 40Ar/39Ar ages for different lithotypes range from 133.7±0.5 Ma to 131.9±0.5 Ma, while monzonite zircon analyzed by SHRIMP yields a U-Pb concordia age of 134.9±0.65 Ma, indicating that the Jacupiranga emplacement was contemporaneous with the extrusion of the tholeiites of the Paraná Magmatic Province. There seems to be no obvious age progression for clinopyroxenites, diorites, or lamprophyres, although the monzonite yield both 40Ar/39Ar and U-Pb ages older than those of the other rocks. Geochemical compositions of the silicate rocks are used to evaluate two main magma-evolution trends for that unit: (1) a strongly silica-undersaturated series, probably related to nephelinite melts and (2) a mildly silica-undersaturated series related to basanite melts. Lamprophyre dikes within the complex are considered as good representatives of the basanite parental magma. Compositions of the calculated melts in equilibrium with diopside cores from clinopyroxenites are quite similar to those of the lamprophyres, suggesting that at least a part of the clinopyroxenites is related to the basanite series. Meladiorite and monzonite show petrographic features and geochemical and isotope compositions (87Sr/86Sri: 0.705979-0.706086 and 143Nd/144Ndi: 0.511945-0.512089) suggestive of crustal assimilation, although it may be relegated to a local process and to some basanite batches. Carbonatites yield isotopic ratios (Nd and Pb) and trace elements composition (e.g. Ba/La, Nb/Ta) that preclude a link by liquid immiscibility with the silicate rocks. Two scenarios are envisaged: a primary magma of carbonatite composition originated by direct partial melting of the mantle or an origin by immiscibility from a hypothetical silicate magma currently unknown in the complex. Nd-Sr-Pb-Hf isotopic data indicate an important contribution of the subcontinental lithospheric mantle (SCLM) in the genesis of those rocks. Lamprophyres and calculated melts in equilibrium with clinopyroxene show relatively high CaO/Al2O3 and La/Zr ratios and low Ti/Eu, indicating a lithospheric mantle metasomatized by CO2-rich fluids and vein-plus-wall-rock melting mechanisms. Compositional variations among those liquids are attributed to the mixing between metasomatic veins partial melt and peridotite partial melt, besides as well as to the differences in the clinopyroxene/garnet ratios on in the mantle. ΔεHf variations suggest a slightly higher role of the wall-rock peridotite as a source component for the nephelinites, whereas the basanite parental magma is mainly related to the wehrlite veins, although both are enriched magmas. Depletion in Nb-Yb, enrichment of LREE relative to HREE, and enrichment in Cs, Rb and Sr in the lamprophyres suggest that the metasomatic reactions in the mantle source were caused by slab-derived fluids. TDM model ages indicate the heterogeneous nature of the mantle source and are coherent with the values generally obtained for the alkaline occurrences from the Central-Southeastern part of the South-American Platform.

[pt] Vários estudos sobre o comportamento de produtos oriundos da alteração de rochas devido à ação intempérica já foram desenvolvidos no país. Esses estudos são de grande importância para a engenharia geotécnica, principalmente em locais de clima tropical, quente e úmido, como o Brasil, já que as condições climáticas possuem uma influência significativa na formação resultante da rocha. Logo, o conhecimento detalhado da origem do solo contribui para uma melhor compreensão do seu comportamento geomecânico. Este trabalho compreende principalmente um estudo físico- químicomineralógico e micromorfológico de amostras de solo, com o propósito de analisar o comportamento das mesmas devido à ação do intemperismo. Esse material está localizado no Complexo Alcalino de Tanguá, município de Tanguá, onde as amostras foram retiradas aleatoriamente, mas com base em suas características morfológico-tátil- visuais. Ressalta-se aqui que estudos com esse enfoque desenvolvidos nesse tipo de solo e/ou rochas de origem alcalina são raramente encontrados na literatura. Portanto, a elaboração desse trabalho colabora agregando um conhecimento prévio, sobre a rocha, a materiais originários da mesma que apresentam diferentes graus de intemperização, contribuindo para uma ampliação do conhecimento geral de solos residuais como um todo. Esse estudo foi realizado dentro do contexto do projeto PRONEX-Rio, denominado Geotecnia Aplicada à Avaliação, Prevenção e Remediação de Problemas Ambientais, em desenvolvimento junto ao Núcleo de Geotecnia Ambiental do DEC/PUC-Rio na linha de pesquisa Geotecnia Ambiental do Setor de Geotecnia do DEC/PUC-Rio. / [en] The behavior of rock decomposition products has been studied by many authors throughout the country. These works have great importance for the geotechnical engineering, mainly in tropical regions, with hot and rainy climates, like it is found in Brazil, since atmospheric conditions have a great influence in the soil formation originated from the mother rock. Therefore the detailed knowledge of the soil origin provides a better understanding of its geomechanical behavior. This work deals with a physical- chemicalmineralogical and micromorphological study of arbitrary soil points on the Tanguá alkaline complex, at the Tanguá Municipality (Rio de Janeiro State, Brazil). The main subject of the present work is to analyze effects of weathering on the physical-chemical- mineralogical and structural characteristics of the residual soil derived from the alkaline rock found in Tanguá, as well as on some simple hydro-mechanical characteristics of the material. It`s important to note here that works on this type of rock and/or soil are rarely found in the literature. Thus, this work contributes towards a better understanding on the behaviour of residual soils as a whole.This study has been done within the context of the PRONEX-Rio project named Geotechnics Applied to the Evaluation, Prevention and Remediation of Environmental Problems, under development within the Environmental Geotechnics Group of DEC/PUC-Rio.

Os catalisadores eletroquímicos binários de PtSn/C, PdSn/C e PtPd/C foram sintetizados em diferentes proporções pelo método da redução via borohidreto, posteriormente estes foram caracterizados por microscopia eletrônica de transmissão, difração de raios X, espectroscopia no infravermelho por transformada de Fourier (PtSn/C e PdSn/C) e energia dispersiva de raios X. As atividades eletroquímicas dos diferentes materiais preparados foram avaliadas por intermédio de voltametria cíclica, cronoamperometria e curvas de polarização em célula a combustível alimentada diretamente por etileno glicol em eletrólito alcalino. As curvas de densidade de potência indicaram que os catalisadores eletroquímicos contendo Sn e Pd são mais ativos para a reação de oxidação do etileno glicol, especialmente a composição 70%:30% - relação molar entre os metais suportados em carbono - dos catalisadores PtSn/C, PdSn/C e PtPd/C todos superando as medidas de potência do Pt/C. Este resultado indica que a adição de Sn e Pd favorece a oxidação do etileno glicol em meio alcalino. O melhor desempenho observado para os catalisadores eletroquímicos PtSn/C, PdSn/C e PtPd/C (70%:30%) poderia estar associado à sua maior seletividade quanto a formação de oxalato, ou seja , a formação deste produto resulta em um maior número de elétrons, por consequência em maiores valores de corrente. / Binary electrochemical catalysts PtSn/C, PdSn/C and PtPd/C were synthesized in different proportions by the method of reduction via borohydride. These were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy (PtSn/C and PdSn/C) and energy dispersive X-ray. The electrochemical activities of the different materials prepared were evaluated by cyclic voltammetry, chronoamperometry and polarization curves for fuel cell powered directly by ethylene glycol in an alkaline electrolyte. Power density curves indicated that the electrochemical catalysts Sn-containing or Pd-containing are more active for ethylene glycol oxidation reaction, particularly the (70%:30%) composition of PtSn/C, PdSn/C and PtPd/C, all of them exceeding power measurements of Pt/C. These results indicate that the addition of Sn and Pd promotes the oxidation of ethylene glycol in an alkaline medium and this improved performance may be associated with a higher selectivity for the formation of oxalate that results in a larger number of electrons, consequently enhancing the current values.

Nanoesferas de sílica contendo fluoróforos encapsulados (o complexo quercetina- Al+3 e o corante rodamina B) foram preparadas com alto controle de tamanho e morfologia, utilizando catálise ácida e básica do tetraetilortossilicato (TEOS). As nanopartículas obtidas apresentaram diâmetro da ordem de 200-300 nm, possuindo maior regularidade quando preparadas em meio alcalino. Nas preparações foram utilizados o método de Stöber e o método caroço-casca. Devido à hidrólise da quercetina em meio básico, as partículas funcionalizadas com o flavonóide ou com o complexo quercetina-Al+3, apresentaram maior intensidade de emissão sob catálise ácida. No caso da catálise básica, as partículas apresentaram emissão significativa quando preparadas utilizando um sol de alumina, porém foram obtidos paralelepípedos nanométricos. Os decaimentos de fluorescência para o sistema quercetina-alumina são biexponenciais, em concordância com os dois complexos quercetina-Al+3 formados no interior da nanopartícula de sílica. No caso da rodamina B, foram realizadas medidas de espectroscopia de correlação de fluorescência, que mostraram uma relação entre relaxação difusional com tamanho e autoagregação das partículas. / Silica nanospheres doped with quercetin-Al+3 and rhodamine B were synthesized with high size control and morphology, using acid and basic catalysis of tetraethylorthosilicate (TEOS). The nanoparticle diameter obtained was about 200- 300 nm, with higher regularity when synthesized in alkaline media. The Stöber\'s and core-shell methods were used as preparation methods. Because the alkaline hydrolysis of quercetin, the flavonoid or the quercetin-Al+3 complex doped nanoparticles showed higher emission intensity when acid catalysis was used. When basic catalysis was performed, the particles prepared with an alumina-sol showed expressive emission intensity, but nanometric parallelepipeds were obtained. The quercetin-alumina fluorescence decays are biexponential, agreeing with the two types of quercetin-Al+3 complexes formed in the nanoparticles domain. In the case of rhodamine B, fluorescence correlation spectroscopy (FCS) measurements were performed, showing a relation between diffusion relaxation with size and aggregation behavior.

A organização da membrana biológica em microdomínios tem um papel chave em vários processos celulares semelhante a receptores protéicos e a transdução de sinal. A existência de microdomínios, também denominados de rafts tem sido explicada pela separação das membranas lipídicas em duas fases: liquida cristalina (L) e fase liquida ordenada (Lo) rica em colesterol e esfingolipídeos. Assim, o enfoque deste projeto foi correlacionar mecanismos de controle da atividade da fosfatase alcalina (TNAP) com a organização intermolecular e o estado de fase de alguns lipídios que compõem as vesículas da matrix. Foi estudada a modulação da atividade da enzima e sua inserção à sistemas de lipossomos constituídos com diferentes composições lipídicas (Dipalmitoilfosfatidilcolina, Colesterol, Esfingomielina e Gangliosídeo) como um mecanismo de regulação e transdução entre enzimas que não compartilham intermediários metabólicos comuns. Isto é, verificar como mudanças de organização molecular, induzida por colesterol e/ou outros lipídios, podem modular a atividade de enzimas regulando a produção de mensageiros lipídicos secundários e/ou processos de fusão e recombinação topológica da bicamada lipídica, modulando concomitantemente a atividade da fosfatase alcalina. Com tal propósito, a TNAP foi reconstituída em lipossomos constituídos de DPPC e lipossomos mistos formando sistemas binários DPPC:Chol, DPPC:SM e DPPC:GM1 com razões molares de (9:1); sistemas terciários DPPC:Chol:SM, DPPC:Chol:GM1 e DPPC:SM:GM1 com razões molares de (8:1:1) e por fim sistemas quaternários constituídos de DPPC:Chol:SM:GM1 (7:1:1:1). Estes sistemas foram propostos com o intuito de mimetizarmos os lipid rafts existentes nas membranas biológicas, porém utilizando lipídios que já foram identificados e quantificados nas vesículas da matrix. Foram avaliados os efeitos da composição lipídica dos lipossomos na inserção da enzima aos sistemas vesiculares. Além disso, foram realizados estudos biofísicos de calorimetria analisando como os parâmetros termodinâmicos são afetados com as diferentes composições lipídicas e pela presença da enzima ancorada aos sistemas. A reconstituição da enzima a lipossomos constituídos de DPPC proporcionou uma incorporação em torno de 80% da atividade enzimática. Estudos termodinâmicos dos proteolipossomos formados evidenciaram uma queda significativa nos valores de variação de entalpia em relação aos sistemas de lipossomos (de 7,63 a 1,88 kcal.mol-1). Lipossomos binários constituídos de DPPC:Chol em concentrações crescentes (9:1, 9:2, 9:3, 7:3, 9:4 e 9:5 razão molar) foram estudados tanto pelos parâmetros biofísicos como pela habilidade de inserção da enzima a tais sistemas. Foi observado um significativo decréscimo nos valores de variação entalpia com o aumento da proporção de colesterol no lipossomo. Além disso, a presença do colesterol proporcionou uma redução na inserção da atividade catalítica em até 42%, quando utilizada a composição lipídica de 9:5 DPPC:Chol. Dos sistemas binários formados com razões molares 9:1, o que apresentou maior porcentagem de reconstituição da TNAP foi o sistemas DPPC:Chol, apresentando em torno de 62% de incorporação da enzima. Os sistemas terciários apresentaram ao redor de 30% de incorporação da atividade catalítica e o sistema quaternário em torno de 25%. Além dos ensaios de atividade enzimática, a incorporação da enzima aos sistemas vesiculares também pôde ser comprovada pelas mudanças nos parâmetros termodinâmicas detectados por DSC. Nos estudos de calorimetria de todos os sistemas de proteolipossomos formados, foram observadas significativas diminuições nos valores de variação de entalpia quando comparados aos sistemas de lipossomos correspondentes. Deste modo, os resultados aqui apresentados fornecem novas informações que poderão contribuir tanto para a compreensão do comportamento da atividade da fosfatase alcalina na presença de diferentes composições lipídicas dos microdomínios existente membrana, quanto para o entendimento dos processos de regulação da enzima durante o processo de biomineralização. / The organization of the biological membrane in microdomains has a key roll in many cellular processes similar to proteic receptors and signal transduction. The existence of microdomains, also called rafts, has been explained by the lipid membrane separation in two phases: crystalline phase (L) and ordinate liquid phase (Lo), rich in cholesterol and sphingolipids. The focus of this Project was to correlate activity control mechanisms of the alkaline phosphatase (TNAP) with the intermolecular organization and the phase stat of some lipids that comprise the matrix vesicles. The enzyme activity modulation and its insertion into liposomes systems, constituted by different lipid compositions (DPPC, Chol, SM e GM1) as a regulation and transduction mechanism between enzymes that do not share common intermediary metabolites, was studied. That is, to verify how molecular organization changes, induced by cholesterol and/or other lipids, can modulate the enzyme activity regulating the production of secondary lipid messengers and/or fusion processes and topological recombination of the lipidic bilayer, concomitantly modeling the alkaline phosphatase activity. TNAP was then reconstituted in liposomes constituted by DPPC and mixed liposomes forming binary systems DPPC:Chol , DPPC:SM , DPPC: Chol:GM1 with (9:1) molar rates; tertiary systems DPPC:Chol:SM, DPPC:Chol:GM1 and DPPC:SM:GM1 with (8:1:1) molar rates and finally quaternary system constituted by DPPC:Chol:SM:GM1 (7:1:1:1). These systems were proposed aiming the mimetization of lipid rafts existent in biological membranes, but using lipids that had already been identified and quantified in the matrix vesicles. The effects of liposome lipid composition in the enzyme insertion to the vesicular systems were assayed. Besides that, calorimetry biophysical studies were done analyzing how the thermodynamic parameters are affected by the different lipid compositions e by the presence of the systems anchored enzyme. The enzyme reconstruction to the DPPC constituted liposomes has provided an incorporation of around 80% of the enzyme activity. Thermodynamic studies of the proteoliposomes formed have shown a significant decrease in the H values in relation to the liposomes systems (from 7.63 to 1.88 kcal.mol-1). Binary liposomes constituted of DPPC:Chol in increasing concentrations (9:1, 9:2, 9:3, 7:3, 9:4 e 9:5 molar ratio) were studied by the biophysical parameters as well as by the insertion ability of the enzyme into those systems. A significant decrease in the enthalpy values with the increase of the cholesterol proportion in the liposome was observed. Besides that, the presence of cholesterol has allowed a reduction in the insertion of the catalytic activity in up to 42% when the lipid composition 9:5 DPPPC:Chol was used. Among the binary systems formed with molar ratios of 9:1, the one which showed the highest percentage of TNAP reconstitution was the DPPC:Chol system, with around 62% enzyme incorporation. The tertiary systems had around 30% incorporation of the catalytic activity, and the quaternary system around 25%. Besides the enzymatic activity assays, the enzyme incorporation to the vesicular systems can also be verified by the thermodynamic parameters change detected by DSC. In the calorimetry studies of all the proteoliposomes formed, significant decreases in the enthalpy values were observed when compared to the corresponding liposomes systems. Thereby, the results presented here provide new information that can contribute to understand the alkaline phosphatase behavior in the presence of different microdomain lipid compositions existent in the membrane, as well as understanding the regulation processes of the enzyme during the biomineralization process.

Os osteoblastos são responsáveis pelo início do processo de biomineralização óssea mediada pela liberação de vesículas da matriz (MVs). As MVs surgem por brotamento das superfícies laterais dos osteoblastos e são secretadas para a matriz. A membrana das MVs possuem níveis elevados de Fosfatase Alcalina (TNAP), entre outra enzimas/proteínas, bem como de Chol, em comparação com a membrana plasmática. O objetivo deste estudo foi a construção de proteolipossomos constituídos por Dipalmitoilfosfatidilcolina (DPPC) ou Dioleoilfosfatidilcolina (DOPC), com Colesterol (Chol) em diferentes proporções para a caracterização cinética da TNAP, utilizando os substratos ATP, PPi e ADP, a fim de se obter um sistema que mimetize as MVs. O aumento da concentração de Chol dificultou a incorporação da TNAP aos sistemas constituídos com DPPC, e facilitou a sua incorporação aos constituídos por DOPC. A presença do Chol em todos os sistemas miméticos preparados afetou os parâmetros cinéticos de hidrólise da TNAP para todos os substratos estudados. Entretanto, independentemente da presença do Chol, a hidrólise do PPi apresentou sempre uma maior eficiência (maior kcat/K0.5), sugerindo que este substrato provavelmente possa ser hidrolisado preferencialmente. O tratamento com 2 mM de ciclodextrina (bmCD), resultou na remoção de apenas 70% do Chol de proteolipossomos constituídos por DPPC:Chol 36% mol. Estudos de calorimetria diferencial (DSC) revelaram que a bmCD fica ligada ao sistemas vesiculares causando interferência para os demais ensaios. Quando 36% mol de colestenona (Achol), um análogo de Chol, foi empregado na construção dos proteolipossomos de DPPC, foram encontrados comportamentos cinéticos distintos para a TNAP. O ATP foi hidrolisado com uma Vmáx menor que a os sistemas constituídos por DPPC:Chol 36% e maior do que para sistemas de DOPC:Chol 36% mol. Os valores de K0.5 foram menores para DPPC:Achol 36 % mol em comparação aos sistemas análogos. Com relação a hidrolise do PPi, os parâmetros cinéticos foram similares, em relação aos sistemas estudados contendo DPPC:Chol ou DOPC:Chol. Por fim, foi avaliada a capacidade de propagação de nódulos de mineralização pelos sistemas vesiculares contendo DPPC, DPPC:Chol e DPPC:Achol (com e sem TNAP incorporada), utilizando o ATP como substrato. A mineralização foi cerda de 16 vezes mais eficiente na presença de protelipossomos que continham tanto Chol ou colestenona, do que para o sistema somente constituído por DPPC (cerca de 4 vezes), quando comparados com os respectivos sistemas de lipossomos (na ausência de enzima). Diante destas diferenças apresentadas, tanto no comportamento cinético, quanto na capacidade de mineralização, pode-se suger que o microambiente lipídico tem um importante papel das MVs. Uma explicação que pode ser sugerida é que fatores termodinâmicos como: a diminuição da entalpia de transição; perda de pré-transição; presença de cargas superficiais; presença de diferentes substratos; bem como, orientações das ligações de hidrogênio com a molécula de água na superfície dos proteolipossomos, podem acarretar em modificações conformacionais na TNAP. A relevância dos resultados apresentados pode contribuir no entendimento da função dos lipídios e de suas interações com as proteínas presentes na MVs no processo de biomineralização. / Osteoblasts are responsible for initiating the bone biomineralization process mediated by the release of matrix vesicles (MVs). The MVs arise by budding from the membrane of the osteoblasts and are secreted into the matrix. The MVs membrane has high levels of tissue non-specific alkaline phosphatase (TNAP), among other enzymes/proteins, as well as cholesterol, compared with the plasma membrane. The objective of this study was to build proteoliposomes constituted by Dipalmitoylphosphatidylcholine (DPPC) or dioleoylphosphatidylcholine (DOPC), with cholesterol (Chol) in different molar ratios for the kinetic characterization of TNAP, using the substrates ATP, ADP and PPi, in order to obtain systems that mimic the MVs. The increase in the cholesterol concentration hampered the incorporation of TNAP into the DPPC systems, but favored its incorporation into the DOPC liposomes. The presence of cholesterol in all prepared mimetic systems affected the kinetic parameters of hydrolysis for all substrates studied. Regardless of the presence of cholesterol, PPi hydrolysis always showed greater catalytic efficiency (kcat/K0.5), suggesting a preferential hydrolysis of this substrate. Treatment with 2 mM cyclodextrin (BMCD) resulted in removal of 70% of the cholesterol from the proteoliposome constituted of DPPC:Cholesterol 36% (molar ratio). Differential scanning calorimetry (DSC) studies showed that BMCD was bound to the vesicular systems interfering with the other assays. When 36% of cholestenone (Achol), an analogue of cholesterol, was employed in the construction of DPPC proteoliposomes, a different kinetic behavior was observed for TNAP. The Vmax for ATP hydrolysis was lower compared with the systems constituted of DPPC:Chol 36% and higher than that obtained for the DOPC:Chol 36% system. The values of K0.5 were lower for DPPC:Achol 36% compared to the similar systems. With respect to the hydrolysis of PPi, the kinetic parameters were similar for the systems constituted of DPPC:Chol and DOPC:Chol. Finally, we evaluated the ability of the vesicular systems containing DPPC, DPPC:Chol and DPPC:Achol (with and without TNAP incorporated) to propagate mineralization nodules, using ATP as substrate. The mineralization was about 16 times more efficient in the presence of proteoliposomes containing Chol or Achol than for the system constituted of DPPC only (about 4 times more efficient) compared with the corresponding liposome (in the absence of enzyme). Given the differences observed for both the kinetic behavior and the mineralization ability of the different systems, we suggest that the lipid microenvironment plays an important role in MVs function. A possible explanation for these differences is that thermodynamic factors such as the decrease in the enthalpy of transition and the loss of pre-transition, as well as the presence of surface charges, the presence of different substrates, and the orientation of hydrogen bonds with the water molecule on the surface of the proteoliposomes, may cause conformational changes in TNAP molecule. These relevant results can contribute for the understanding of the role of lipids and their interactions with proteins present in MVs in the biomineralization process.