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Projeto de investigação
Twin to Illuminate Metals in Biology and Biocatalysis through Biospectroscopy
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Molecular Mechanisms of Microbial Extracellular Electron Transfer
Publication . Paquete, Catarina M.; Morgado, Leonor; Salgueiro, Carlos A.; Louro, Ricardo O.; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); UCIBIO - Applied Molecular Biosciences Unit; DQ - Departamento de Química; IMR Press Limited
Extracellular electron transfer is a key metabolic process of many organisms that enables them to exchange electrons with extracellular electron donors/acceptors. The discovery of organisms with these abilities and the understanding of their electron transfer processes has become a priority for the scientific and industrial community, given the growing interest on the use of these organisms in sustainable biotechnological processes. For example, in bioelectrochemical systems electrochemical active organisms can exchange electrons with an electrode, allowing the production of energy and added-value compounds, among other processes. In these systems, electrochemical active organisms exchange electrons with an electrode through direct or indirect mechanisms, using, in most cases, multiheme cytochromes. In numerous electroactive organisms, these proteins form a conductive pathway that allows electrons produced from cellular metabolism to be transferred across the cell surface for the reduction of an electrode, or vice-versa. Here, the mechanisms by which the most promising electroactive bacteria perform extracellular electron transfer will be reviewed, emphasizing the proteins involved in these pathways. The ability of some of the organisms to perform bidirectional electron transfer and the pathways used will also be highlighted.
Long-lived NIR emission in sulfur-doped zeolites due to the presence of [S3]2- clusters
Publication . Viola, Catarina; Laia, César A. T.; Outis, Mani; Ferreira, Luís F. V.; Alves, Luís C.; Teixeira, Miguel; Folgosa, Filipe; Lima, João C.; Ruivo, Andreia; Avó, João; DQ - Departamento de Química; LAQV@REQUIMTE; VICARTE - Vidro e Cerâmica para as Artes; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); Elsevier
The exploration of novel long-lived near-infrared (NIR) luminescent materials has attracted significant attention due to their applications in optical communications, anticounterfeiting, and bioimaging. However, these materials usually present low photoluminescence quantum yields and low photo- and chemical stability. Novel emitters that overcome these limitations are in demand. In this study, NIR emission was achieved using widely available, sustainable, and non-toxic materials through the synthesis of sulfur-doped zeolites, with different S/Cl ratios. With a combination of computational calculations (TD-DFT) and spectroscopic data, this emission was assigned to the radiative decay of excited triplet states of [S3]2- clusters, which resulted in a remarkably high Stokes shift (1.97 eV, 440 nm) and an average decay time of 0.54 ms. These new materials present high stability, external quantum efficiency of up to 17%, and a long-lived NIR emission, placing these compounds in a unique position to be used in applications demanding NIR emitters.
Role of multiheme cytochromes involved in extracellular anaerobic respiration in bacteria
Publication . Edwards, Marcus J.; Richardson, David J.; Paquete, Catarina M.; Clarke, Thomas A.; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); Wiley-Blackwell
Heme containing proteins are involved in a broad range of cellular functions, from oxygen sensing and transport to catalyzing oxidoreductive reactions. The two major types of cytochrome (b-type and c-type) only differ in their mechanism of heme attachment, but this has major implications for their cellular roles in both localization and mechanism. The b-type cytochromes are commonly cytoplasmic, or are within the cytoplasmic membrane, while c-type cytochromes are always found outside of the cytoplasm. The mechanism of heme attachment allows for complex c-type multiheme complexes, having the capacity to hold multiple electrons, to be assembled. These are increasingly being identified as secreted into the extracellular environment. For organisms that respire using extracellular substrates, these large multiheme cytochromes allow for electron transfer networks from the cytoplasmic membrane to the cell exterior for the reduction of extracellular electron acceptors. In this review the structures and functions of these networks and the mechanisms by which electrons are transferred to extracellular substrates is described.
Exploring the Effects of bolA in Biofilm Formation and Current Generation by Shewanella oneidensis MR-1
Publication . da Silva, Ana Vieira; Edel, Miriam; Gescher, Johannes; Paquete, Catarina M.; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); Frontiers Research Foundation
Microbial electrochemical technologies (METs) have emerged in recent years as a promising alternative green source of energy, with microbes consuming organic matter to produce energy or valuable byproducts. It is the ability of performing extracellular electron transfer that allows these microbes to exchange electrons with an electrode in these systems. The low levels of current achieved have been the limiting factor for the large-scale application of METs. Shewanella oneidensis MR-1 is one of the most studied electroactive organisms regarding extracellular electron transfer, and it has been shown that biofilm formation is a key factor for current generation. The transcription factor bolA has been identified as a central player in biofilm formation in other organisms, with its overexpression leading to increased biofilm. In this work we explore the effect of this gene in biofilm formation and current production by S. oneidensis MR-1. Our results demonstrate that an increased biofilm formation and consequent current generation was achieved by the overexpression of this gene. This information is crucial to optimize electroactive organisms toward their practical application in METs.
Spectroscopic and Structural Characterization of Reduced Desulfovibrio vulgaris Hildenborough W-FdhAB Reveals Stable Metal Coordination during Catalysis
Publication . Oliveira, Ana Rita; Mota, Cristiano; Klymanska, Kateryna; Biaso, Frederic; Romão, Maria Joao; Guigliarelli, Bruno; Pereira, Inês Cardoso; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); UCIBIO - Applied Molecular Biosciences Unit; DQ - Departamento de Química; ACS - American Chemical Society
Metal-dependent formate dehydrogenases are important enzymes due to their activity of CO2reduction to formate. The tungsten-containing FdhAB formate dehydrogenase from Desulfovibrio vulgaris Hildenborough is a good example displaying high activity, simple composition, and a notable structural and catalytic robustness. Here, we report the first spectroscopic redox characterization of FdhAB metal centers by EPR. Titration with dithionite or formate leads to reduction of three [4Fe-4S]1+clusters, and full reduction requires Ti(III)-citrate. The redox potentials of the four [4Fe-4S]1+centers range between -250 and -530 mV. Two distinct WVsignals were detected, WDVand WFV, which differ in only the g2-value. This difference can be explained by small variations in the twist angle of the two pyranopterins, as determined through DFT calculations of model compounds. The redox potential of WVI/Vwas determined to be -370 mV when reduced by dithionite and -340 mV when reduced by formate. The crystal structure of dithionite-reduced FdhAB was determined at high resolution (1.5 Å), revealing the same structural alterations as reported for the formate-reduced structure. These results corroborate a stable six-ligand W coordination in the catalytic intermediate WVstate of FdhAB.
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Entidade financiadora
European Commission
Programa de financiamento
H2020
Número da atribuição
810856