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Filipa L Sousa

Publications and source records attributed to Filipa L Sousa.

7 recordsLinked to original sources
PubMed2006

Reactions inside a porous nanocapsule/artificial cell: encapsulates' structuring directed by internal surface deprotonations.

In the cavities of unprecedentedly functionalised, spherical, porous capsules of the type {Pentagon}12{Linker}30 identical with [{(Mo)Mo5O21(H2O)6}12{Mo2O4(ligand)}30]n- reactions with the ligands -i.e. at the internal shell surfaces - can be performed, in the present case deliberate aquation/hydration and deprotonation reactions at the linker fragments {(Mo2O4)C2O4H}+ similar to that reported in the literature for [(NH3)5CoC2O4H]2+ in solution.

Journal Article↗
PubMed2006

A tyrosine residue deprotonates during oxygen reduction by the caa3 reductase from Rhodothermus marinus.

Heme-copper oxygen reductases catalyze proton translocation across the cellular membrane; this takes place during the reaction of oxygen to water. We demonstrate with attenuated total reflection-Fourier transform infrared (ATR-FTIR) difference spectroscopy that a tyrosine residue of the oxygen reductase from the thermohalophilic Rhodothermus marinus becomes deprotonated in the transition from the oxidized state to the catalytic intermediate ferryl state P(M). This tyrosine residue is most probably Y256, the helix VI tyrosine residue proposed to substitute for the D-channel glutamic acid that is absent in this enzyme. Comparison with the mitochondrial like oxygen reductase from Rhodobacter sphaeroides suggests that proton transfer from a strategically situated donor to the active site is a crucial step in the reaction mechanism of oxygen reductases.

Binding Sites↗
PubMed2006

Electron paramagnetic resonance studies of the iron-sulfur centers from complex I of Rhodothermus marinus.

Rhodothermus marinus, a thermohalophilic gram negative bacterium, contains a type I NADH/quinone oxidoreductase (complex I). Its purification was optimized, yielding large amounts of pure and active protein. Furthermore, the stoichiometry of NADH oxidation and quinone reduction was shown to be 1:1. The large amounts of protein enabled a thorough characterization by electron paramagnetic resonance (EPR) spectroscopy at different temperatures and microwave powers, using NADH, NADPH, and dithionite as reducing agents. A minimum of two [2Fe-2S](2+/1+) and four [4Fe-4S](2+/1+) centers were observed in the purified complex. Redox titrations monitored by EPR spectroscopy made possible the determination of the reduction potentials of the iron-sulfur centers; with the exception of one of the [4Fe-4S](2+/1+) centers, which has a lower reduction potential, all the other centers have reduction potentials of -240 +/- 20 mV, pH 7.5.

Binding Sites↗
PubMed2005

A nhaD Na+/H+ antiporter and a pcd homologues are among the Rhodothermus marinus complex I genes.

The NADH:menaquinone oxidoreductase (Nqo) is one of the enzymes present in the respiratory chain of the thermohalophilic bacterium Rhodothermus marinus. The genes coding for the R. marinus Nqo subunits were isolated and sequenced, clustering in two operons [nqo1 to nqo7 (nqoA) and nqo10 to nqo14 (nqoB)] and two independent genes (nqo8 and nqo9). Unexpectedly, two genes encoding homologues of a NhaD Na+/H+ antiporter (NhaD) and of a pterin-4alpha-carbinolamine dehydratase (PCD) were identified within nqoB, flanked by nqo13 and nqo14. Eight conserved motives to harbour iron-sulphur centres are identified in the deduced primary structures, as well as two consensus sequences to bind nucleotides, in this case NADH and FMN. Moreover, the open-reading-frames of the putative NhaD and PCD were shown to be co-transcribed with the other complex I genes encoded by nqoB. The possible role of these two genes in R. marinus complex I is discussed.

Amino Acid Sequence↗
PubMed2004

Structure at 1.3 A resolution of Rhodothermus marinus caa(3) cytochrome c domain.

The cytochrome c domain of subunit II from the Rhodothermus marinus caa(3) HiPIP:oxygen oxidoreductase, a member of the superfamily of heme-copper-containing terminal oxidases, was produced in Escherichia coli and characterised. The recombinant protein, which shows the same optical absorption and redox properties as the corresponding domain in the holo enzyme, was crystallized and its structure was determined to a resolution of 1.3 A by the multiwavelength anomalous dispersion (MAD) technique using the anomalous dispersion of the heme iron atom. The model was refined to final R(cryst) and R(free) values of 13.9% and 16.7%, respectively. The structure reveals the insertion of two short antiparallel beta-strands forming a small beta-sheet, an interesting variation of the classical all alpha-helical cytochrome c fold. This modification appears to be common to all known caa(3)-type terminal oxidases, as judged by comparative modelling and by analyses of the available amino acid sequences for these enzymes. This is the first high-resolution crystal structure reported for a cytochrome c domain of a caa(3)-type terminal oxidase. The R.marinus caa(3) uses HiPIP as the redox partner. The calculation of the electrostatic potential at the molecular surface of this extra C-terminal domain provides insights into the binding to its redox partner on one side and its interaction with the remaining subunit II on the other side.

Amino Acid Sequence↗
PubMedDate not supplied

Lanthanopolyoxotungstoborates: synthesis, characterization, and layer-by-layer assembly of europium photoluminescent nanostructured films.

New lanthanopolyoxotungstoborates, K6-xHx[Ln(BW11O39)(H2O)3].nH2O, Ln(III) = Sm, Eu, Tb, Er, were prepared and characterized by spectroscopic methods (Fourier transform infrared, Fourier transform-Raman, 11B solid-state nuclear magnetic resonance, and photoluminescence) and elemental analysis. A layer-by-layer assembly method was employed to fabricate multilayered films containing the europium heteropolyanion and the polyelectrolytes poly(sodium 4-styrenesulfonate) and poly(diallydimethylammonium chloride). The photoluminescence behavior of these final nanostructures was investigated and compared with that of the starting Eu(III) polyoxometalate used as the building unit.

Adsorption↗