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Featured researches published by Madalena Humanes.


Phytochemistry | 2001

Vanadium haloperoxidases from brown algae of the Laminariaceae family.

Mércia Melo de Almeida; S. Filipe; Madalena Humanes; M.F. Maia; Ricardo Melo; N. Severino; J.A.L. da Silva; J.J.R.Fraústo da Silva; Ron Wever

Vanadium haloperoxidases were extracted, purified and characterized from three different species of Laminariaceae--Laminaria saccharina (Linné) Lamouroux, Laminaria hyperborea (Gunner) Foslie and Laminaria ochroleuca de la Pylaie. Two different forms of the vanadium haloperoxidases were purified from L. saccharina and L. hyperborea and one form from L. ochroleuca species. Reconstitution experiments in the presence of several metal ions showed that only vanadium(V) completely restored the enzymes activity. The stability of some enzymes in mixtures of buffer solution and several organic solvents such as acetone, ethanol, methanol and 1-propanol was noteworthy; for instance, after 30 days at least 40% of the initial activity for some isoforms remained in mixtures of 3:1 buffer solution/organic solvent. The enzymes were also moderately thermostable, keeping full activity up to 40 degrees C. Some preliminary steady-state kinetic studies were performed and apparent Michaelis-Menten kinetic parameters were determined for the substrates iodide and hydrogen peroxide. Histochemical studies were also performed in fresh tissue sections from stipe and blade of L. hyperborea and L. saccharina, showing that haloperoxidase activity was concentrated in the external cortex near the cuticle, although some activity was also observed in the inner cortical region.


Phytochemistry | 1998

Saccorhiza polyschides (phaeophyceae; phyllariaceae) A new source for vanadium-dependent haloperoxidases

Mércia Melo de Almeida; Madalena Humanes; Ricardo Melo; José A. L. da Silva; J.J.R.Fraústo da Silva; H. Vilter; Ron Wever

Abstract Vanadium-dependent iodoperoxidases from the brown seaweed Saccorhiza polyschides (Lightfoot) Batters, collected at three different locations along the Portuguese west coast, were extracted, purified and characterized. Several extraction procedures were tested, including two-phase aqueous systems. The purification of the iodoperoxidases was achieved using hydrophobic interaction chromatography followed by chromatofocusing. It was possible to isolate three different isoforms of the enzyme, which show mainly iodoperoxidase activity. The three native enzymes have a relative M r around 125 kDa, and two subunits of M r about 64 kDa. Reactivation studies of the apoenzymes with several metal ions revealed that vanadium(V) was essential for enzymatic activity. These enzymes are remarkably thermostable, maintaining their maximum activity up to 50°. The kinetic parameters for the enzyme catalysed iodoperoxidase reaction were obtained at pH 6.1. In the concentration range studied (0.2–8 mM) there was no inhibition by H 2 O 2 whereas iodide inhibition was already apparent at the top values of the concentration range studied (2–25 mM).


Marine Drugs | 2011

Sulfated polysaccharides in marine sponges: extraction methods and anti-HIV activity.

Ana I. S. Esteves; Marisa Nicolai; Madalena Humanes; Joao Goncalves

The extraction, fractionation and HIV-1 inhibition potential of polysaccharides extracted from three species of marine sponges, Erylus discophorus, Cliona celata and Stelletta sp., collected in the Northeastern Atlantic, is presented in this work. The anti-HIV activity of 23 polysaccharide pellets and three crude extracts was tested. Crude extracts prepared from Erylus discophorus specimens were all highly active against HIV-1 (90 to 95% inhibition). Cliona celata pellets showed low polysaccharide content (bellow 38.5%) and almost no anti-HIV activity (<10% inhibition). Stelletta sp. pellets, although quite rich in polysaccharide (up to 97.3%), showed only modest bioactivity (<36% HIV-1 inhibition). Erylus discophorus pellets were among the richest in terms of polysaccharide content (up to 98%) and the most active against HIV-1 (up to 95% inhibition). Chromatographic fractionation of the polysaccharide pellet obtained from a specimen of Erylus discophorus (B161) yielded only modestly active fractions. However, we could infer that the active molecule is most probably a high molecular weight sulfated polysaccharide (>2000 kDa), whose mechanism is possibly preventing viral attachment and entry (fusion inhibitor).


Journal of Natural Products | 2008

Isomeric Furanosesquiterpenes from the Portuguese Marine Sponge Fasciospongia sp.

Helena Gaspar; Susana Santos; Marianna Carbone; Ana Sofia Rodrigues; Ana Isabel Rodrigues; Maria J. Uriz; Sonia Savluchinske Feio; Dominique Melck; Madalena Humanes; Margherita Gavagnin

This paper reports the chemical study of a sample of Fasciospongia sp. collected along the Atlantic Portuguese coast. Three new isomeric furanosesquiterpenes, isomicrocionin-3 ( 1), (-)-microcionin-1 ( 2), and (-)-isomicrocionin-1 ( 3), were isolated along with the known (-)- ent-pallescensin A ( 4) and (-)-pallescensin-1 ( 5) from the ethyl acetate-soluble portion of the methanolic extract. The structures of the new compounds were elucidated by extensive spectroscopic studies. (-)-Microcionin-1 ( 2) tested positive against several Gram-negative bacteria.


Frontiers in Microbiology | 2015

The antimicrobial activity of heterotrophic bacteria isolated from the marine sponge Erylus deficiens (Astrophorida, Geodiidae)

Ana Patrícia Graça; Flávia Viana; Joana Bondoso; Maria Inês Correia; Luís S. Gomes; Madalena Humanes; Alberto Reis; Joana R. Xavier; Helena Gaspar; Olga Maria Lage

Interest in the study of marine sponges and their associated microbiome has increased both for ecological reasons and for their great biotechnological potential. In this work, heterotrophic bacteria associated with three specimens of the marine sponge Erylus deficiens, were isolated in pure culture, phylogenetically identified and screened for antimicrobial activity. The isolation of bacteria after an enrichment treatment in heterotrophic medium revealed diversity in bacterial composition with only Pseudoalteromonas being shared by two specimens. Of the 83 selected isolates, 58% belong to Proteobacteria, 23% to Actinobacteria and 19% to Firmicutes. Diffusion agar assays for bioactivity screening against four bacterial strains and one yeast, revealed that a high number of the isolated bacteria (68.7%) were active, particularly against Candida albicans and Vibrio anguillarum. Pseudoalteromonas, Microbacterium, and Proteus were the most bioactive genera. After this preliminary screening, the bioactive strains were further evaluated in liquid assays against C. albicans, Bacillus subtilis and Escherichia coli. Filtered culture medium and acetone extracts from three and 5 days-old cultures were assayed. High antifungal activity against C. albicans in both aqueous and acetone extracts as well as absence of activity against B. subtilis were confirmed. Higher levels of activity were obtained with the aqueous extracts when compared to the acetone extracts and differences were also observed between the 3 and 5 day-old extracts. Furthermore, a low number of active strains was observed against E. coli. Potential presence of type-I polyketide synthases (PKS-I) and non-ribosomal peptide synthetases (NRPSs) genes were detected in 17 and 30 isolates, respectively. The high levels of bioactivity and the likely presence of associated genes suggest that Erylus deficiens bacteria are potential sources of novel marine bioactive compounds.


Phytochemistry | 2000

Purification and characterisation of vanadium haloperoxidases from the brown alga Pelvetia canaliculata

M.G. Almeida; Madalena Humanes; Ricardo Melo; José A. L. da Silva; J.J.R.Fraústo da Silva; Ron Wever

Two enzymes characterised as iodoperoxidases (PcI and PcII), with vanadium-dependent activity, have been purified from the brown alga Pelvetia canaliculata (L.) Decne et Thur. (Fucaceae, Phaeophyceae), collected in the Northern Portuguese coast, at Viana do Castelo. The relative molecular masses were 166 kDa for PcI and 416 kDa for PcII, as determined by gel filtration. SDS-PAGE shows that PcI has just one band corresponding to a subunit of 66 kDa, while PcII shows four bands (66, 72, 157 and 280 kDa). The following kinetic parameters have been determined from a steady-state analysis of the oxidation of iodide by H2O2: PcI, pHopt = 6.0, KM(I-) = 2.1 mM, KM(H2O2) = 110 microM, Ki(I-) = 127 mM; and PcII, pHopt = 6.5, KM(I-) = 2.4 mM, KM(H2O2) = 20 microM and Ki(I-) = 69 mM. These iodoperoxidases are thermostable, as also observed for vanadium bromo- and chloroperoxidases.


Journal of Inorganic Biochemistry | 2011

Biocatalytic formation of synthetic melanin: The role of vanadium haloperoxidases, L-DOPA and iodide

Marisa Nicolai; Gisela Gonçalves; Filipe Natalio; Madalena Humanes

The vanadium haloperoxidase (V-HPO) enzyme, extracted from the brown alga Laminaria saccharina, is able to catalyze the formation of a black precipitate, using as precursor the amino acid L-dopa in the presence of hydrogen peroxide and iodide, in one-pot synthesis. The L-dopa oxidation is a multistep reaction with a crucial role played by the iodide in the enzyme catalyzed peroxidative production of dopachrome, a well known intermediate in the synthesis of melanin. Dopachrome is then converted to a synthetic form of melanin through a polymerization reaction. Factors, such as buffer composition and pH, influence significantly the reaction first steps, but further steps of melanin production are hardly influenced. The biosynthetic melanin produced through the combination V-HPO/I/H(2)O(2), was characterized by several spectroscopic techniques (UV-vis and FT-IR) as well as XRD. Moreover, this biopolymer is light sensitive, decomposing into oligo- and monomeric units. Scanning electron microscopy (SEM) imaging showed different morphologies when compared with commercial available melanin. The biosynthetic production of melanin can have a wide range of applications from photosensitive cells to biomedicine with the advantage of being produced under eco-friendly and mild conditions.


Chemical Speciation and Bioavailability | 1999

Elemental composition of Demospongiae from the eastern Atlantic coastal waters

M.F. Araújo; Alexandra Cruz; Madalena Humanes; Maria Teresa Lopes; José A. L. da Silva; J.J.R.Fraústo da Silva

AbstractThe elemental composition (Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr and Pb) of 30 coastal and two deep-sea Demospongiae specimens, belonging to 19 different species and ...


Journal of Materials Chemistry | 2011

V(2)O(5) nanowires with an intrinsic iodination activity leading to the formation of self-assembled melanin-like biopolymers

Filipe Natalio; Rute André; Sascha A. Pihan; Madalena Humanes; Ron Wever; Wolfgang Tremel

V2O5 nanowires act as biomimetic catalysts resembling vanadium haloperoxidases (V-HPO). The nanowires display iodinating activity as confirmed by a colorimetric assay using thymol blue (TB), UV/Vis spectrophotometry and mass spectrometry (FD-MS). In the presence of dopamine these nanowires catalyze the fast and efficient synthesis of melanin-like biopolymers under mild conditions (aqueous solution, neutral pH and room temperature). The resulting melanin-like biopolymer obtained by the V2O5 nanowire catalysts was characterized by scanning electron microscopy (SEM), X-ray diffraction, UV-Vis, FT-IR and electric conductivity resembling the natural biopolymer both in its chemical and morphological features. In addition, this synthetic biopolymer self-assembles into fibril-like structures by forming stacks due to π interactions between the aromatic rings.


Structural Chemistry | 2012

Marine sponge melanin: a new source of an old biopolymer

Marco Araujo; Joana R. Xavier; Carla D. Nunes; Pedro D. Vaz; Madalena Humanes

Various types of melanin have already been found in the majority of organisms, being this biopolymer considered as one of the major pigments present in nature. The presence of this pigment in marine sponges (Phylum Porifera, one of the simplest multicellular organisms) was postulated, but never characterized. In this context this work aims the extraction and characterization of a dark pigment observed in four different marine sponges species (Erylus mamillaris, Erylus discophorus var. deficiens, Pachymatisma johnstonia, Dercitus bucklandi). Characterization of the extracted biopolymer was performed using solid state analytical techniques, due to the characteristic non-solubility of melanin. Therefore, characterization techniques like SEM–EDS, IR, UV–vis, MALDI-MS, elemental analysis and X-ray powder diffraction (XRD) were used to identify the biopolymer. The results showed that the extracted material was obtained with high purity, being identified as melanin. The results also emphasize a large structure variability present in this pigment, showing different structure arrangements and composition depending on its source, which influences the UV behaviour. The structural characterization of this class of pigments is fundamental, allowing a better understanding of melanin properties.

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Ron Wever

University of Amsterdam

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