FCT2-Artigos (em revistas ou actas indexadas)
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- 1,1-Bis(Phenylseleno)-and 1,1-Bis(Methylseleno)- alkyllithiums as building-blocks in organic synthesisPublication . Vanende, D.; Cravador, A.; Krief, A.1,1 - Bis(phenylseleno)alkyllithiums are conveniently prepared from the corresponding selenoacetals and lithium tetramethylpiperidide in HMPT/THF.
- 1,2,4-Trioxolane and 1,2,4,5-Tetraoxane endoperoxides against old-world Leishmania parasites: in vitro activity and mode of actionPublication . Mendes, Andreia; Armada, Ana; Cabral, Lília; Amado, Patrícia; Campino, Lenea; Cristiano, Maria de Lurdes; Cortes, SofiaLeishmaniasis remains one of the ten Neglected Tropical Diseases with significant morbidity and mortality in humans. Current treatment of visceral leishmaniasis is difficult due to a lack of effective, non-toxic, and non-extensive medications. This study aimed to evaluate the selectivity of 12 synthetic endoperoxides (1,2,4-trioxolanes; 1,2,4,5-tetraoxanes) and uncover their biochemical effects on Leishmania parasites responsible for visceral leishmaniasis. The compounds were screened for in vitro activity against L. infantum and L. donovani and for cytotoxicity in two monocytic cell lines (J774A.1 and THP-1) using the methyl thiazol tetrazolium assay. Reactive oxygen species formation, apoptosis, and mitochondrial impairment were measured by flow cytometry. The compounds exhibited fair to moderate anti-proliferative activity against promastigotes of the 2 Leishmania species, with IC50 values ranging from 13.0 ± 1.7 µM to 793.0 ± 37.2 µM. Tetraoxanes LC132 and LC138 demonstrated good leishmanicidal activity on L. infantum amastigotes (IC50 13.2 ± 5.2 and 23.9 ± 2.7 µM) with low cytotoxicity in mammalian cells (SIs 22.1 and 118.6), indicating selectivity towards the parasite. Furthermore, LC138 was able to induce late apoptosis and dose-dependent oxidative stress without affecting mithocondria. Compounds LC132 and LC138 can be further explored as potential antileishmanial chemotypes.
- 1-Methylcyclopropene and lemongrass essential oil nanocoatings effect on the preservation of cold stored ‘Rocha’ pearPublication . Gago, Custódia; Guerreiro, Adriana; Cruz, Sandra; Martins, Nuno; Cabrita, Maria João; Miguel, Maria; Faleiro, Maria Leonor; Antunes, Maria DulceThe effects of coating 'Rocha' pear with alginate-based nanoemulsions enriched with lemongrass essential oil (LG) was evaluated and compared to the usual 1-MCP treatment. Fruit were treated with 1-MCP (312 nL L-1) or coated with nanoemulsions: sodium alginate 2 % (w/w) + lemongrass essential oil 1.25 % (w/w) (LG 1.25 %) or lemongrass essential oil 2.5 % (w/w) (LG 2.5 %). Then, fruit were stored at 0 degrees C and 90-95 % relative humidity (RH), for eight months. Fruit samples were collected at harvest and after two, four, six and eight months of cold storage, and then transferred to shelf-life at 22 degrees C. Upon removal and after 7 d shelf-life, fruit symptoms of superficial scald and internal browning, ethylene production, color CIE (L*, hue), firmness, soluble solids content (SSC), titratable acidity (TA), weight loss, electrolytic leakage (EL), antioxidant activity and fatty acids of pear peel, microbial growth and sensory analyses were evaluated. Coatings and 1-MCP reduced fruit color evolution and preserved better firmness than control. Coatings and 1-MCP did not affect SSC and TA. Treatments did not influence the sensory quality. Microbial growth was within the safety limits in all treatments. Treatments with 1-MCP and LG-nanoemulsions were similarly efficient to reduce superficial scald, nevertheless the LG-nanoemulsions showed higher internal disorders after 8 months of storage and LG 2.5 % had higher decay at the same period, similar to control. 1-MCP treated fruit had the lowest softening rate after shelf-life up to 4 months and LG 2.5 % showed higher weight loss. Also, ethylene production was higher in control and LG 1.25 % up to 6 months plus shelf-life, while after 8 months there was no difference among treatments. This study suggests that 1-MCP is the most efficient for preserving quality of 'Rocha' pear for 8 months, while up to 6 months the best effect is obtained with LG 1.25 % nanocoatings.
- 1st METECH workshop – From deep-sea to coastal zones: Methods and Techniques for studying PalaeoenvironmentsPublication . Veiga-Pires, Cristina; Guillaume St-OngeReconstructing past climate and past ocean circulation demands the highest possible precision and accuracy which urges the scientific community to look at different sediment records such as the ones from coastal zones to deep-sea with a more complete set of technical and methodological tools. However, the information given by each tool varies in precision, accuracy and in significance according to their environmental settings. It is therefore essential to compare tools. With that in mind, and as part of the International year of Planet Earth, a workshop entitled `From deep-sea to coastal zones: Methods and Techniques for studying palaeoenvironments' took place in Faro (Portugal), from 25–29 February 2008.
- 2-D difference gel electrophoresis approach to assess protein expression profiles in Bathymodiolus azoricus from Mid-Atlantic Ridge hydrothermal ventsPublication . Company, Rui; Antúnez, Oreto; Bebianno, Maria João; Cajaraville, Miren P.; Torreblanca, AmparoHydrothermal vent mussels Bathymodiolus azoricus are naturally exposed to toxic chemical species originated directly from vent chimneys. The amount of toxic elements varies significantly among vent sites along the Mid-Atlantic Ridge and B. azoricus must be able to adapt to changes in hydrothermal fluid composition, temperature and pressure. The aim of this work was to study changes in the proteome in the "gill-bacteria complex" of mussels B. azoricus from three hydrothermal vent sites with distinct environmental characteristics using 2-D Fluorescence Difference Gel Electrophoresis (2-D DIGE). Results showed that 31 proteins had different expression profiles among vent sites and both cluster and principal component analysis confirm a clear separation of mussels between sites. This suggests the existence of specific parameters grouping individuals from the same hydrothermal site. Protein spots of the more abundant differentially expressed proteins were excised, digested with trypsin and identified by mass spectrometry. All identified proteins (actin, ubiquinone, S-adenosylhomocysteine hydrolase, cysteine peptidases, chaperonin and catalase) have been related previously with oxidative stress conditions and are known to be affected by ROS inducing stressors, including metals. Results point out to specific adaptations at the proteome level of B. azoricus depending on the level of toxicants present in their environment.
- 3 x 3 lemma for star-exact sequencesPublication . Gran, Marino; Janelidze, Zurab; Rodelo, DianaA regular category is said to be normal when it is pointed and every regular epimorphism in it is a normal epimorphism. Any abelian category is normal, and in a normal category one can define short exact sequences in a similar way as in an abelian category. Then, the corresponding 3 x 3 lemma is equivalent to the so-called subtractivity, which in universal algebra is also known as congruence 0-permutability. In the context of non-pointed regular categories, short exact sequences can be replaced with "exact forks" and then, the corresponding 3 x 3 lemma is equivalent, in the universal algebraic terminology, to congruence 3-permutability; equivalently, regular categories satisfying such 3 x 3 lemma are precisely the Goursat categories. We show how these two seemingly independent results can be unified in the context of star-regular categories recently introduced in a joint work of A. Ursini and the first two authors.
- [4+2] Cycloadditions of 3-Tetrazolyl-1,2-diaza-1,3-butadienes: synthesis of 3-Tetrazolyl-1,4,5,6-tetrahydropyridazinesPublication . Lopes, Susana M. M.; Brigas, Amadeu; Palacios, Francisco; Lemos, A.; Melo, Teresa M. V. D. Pinho eThe synthesis of new 3-tetrazolyl-1,4,5,6-tetrahydropyridazines by Diels–Alder reactions of ethyl 3-(tetrazol-5-yl)-1,2- diaza-1,3-butadiene-1-carboxylates is reported. These 1,2- diaza-1,3-dienes reacted with electron-rich heterocycles, nucleophilic olefins and cumulenes, as well as with electrondeficient dienophiles, to give the target compounds regioselectively. Computational studies corroborated the rationalization of the observed reactivity and selectivity.
- 4,4 '-Di-tert-butyl-2,2 '-bipyridinePublication . Amarante, Tatiana R.; Figueiredo, Sonia; Lopes, Andre D.; Gonçalves, Isabel S.; Almeida Paz, Filipe A.In the title compound, C18H24N2, the molecular unit adopts a trans conformation around the central C-C bond [N-C-C-N torsion angle of 179.2(3)degrees], with the two aromatic rings almost coplanar [dihedral angle of only 0.70 (4)degrees]. The crystal packing is driven by co-operative contacts involving weak C H center dot center dot center dot N and C-H center dot center dot center dot pi interactions, and also the need to fill effectively the available space.
- 5-Deazaalloxazine as photosensitizer of singlet oxygen and potential redox-sensitive agentPublication . Insińska-Rak, Małgorzata; Golczak, Anna; Gierszewski, Mateusz; Anwar, Zubair; Cherkas, Volodymyr; Kwiatek, Dorota; Sikorska, Ewa; Khmelinskii, Igor; Burdziński, Gotard; Cibulka, Radek; Mrówczyńska, Lucyna; Kolanowski, Jacek Lukasz; Sikorski, MarekFlavins are a unique class of compounds that combine the features of singlet oxygen generators and redox-dependent fluorophores. From a broad family of flavin derivatives, deazaalloxazines are significantly underdeveloped from the point of view of photophysical properties. Herein, we report photophysics of 5-deazaalloxazine (1a) in water, acetonitrile, and some other solvents. In particular, triplet excited states of 1ain water and in acetonitrile were investigated using ultraviolet-visible (UV-Vis) transient absorption spectroscopy. The measured triplet lifetimes for 1a were all on the microsecond time scale (approximate to 60 mu s) in deoxygenated solutions. The quantum yield of S-1 -> T-1 intersystem crossing for 1ain water was 0.43 based on T1 energy transfer from 1a to indicaxanthin (5) acting as acceptor and on comparative actinometric measurements using benzophenone (6). 1a was an efficient photosensitizer for singlet oxygen in aerated solutions, with quantum yields of singlet oxygen in methanol of about 0.76, compared to acetonitrile similar to 0.74, dichloromethane similar to 0.64 and 1,2-dichloroethane similar to 0.54. Significantly lower singlet oxygen quantum yields were obtained in water and deuterated water (Phi(Delta)similar to 0.42 and 0.44, respectively). Human red blood cells (RBC) were used as a cell model to study the antioxidant capacity in vitro and cytotoxic activity of 1a. Fluorescence-lifetime imaging microscopy (FLIM) data were analyzed by fluorescence lifetime parameters and distribution for different parts of the emission spectrum. Comparison of multidimensional fluorescent properties of RBC under physiological-like and oxidative-stress conditions in the presence and absence of 1a suggests its dual activity as probe and singlet-oxygen generator and opens up a pathway for using FLIM to analyze complex intracellular behavior of flavin-like compounds. These new data on structure-property relationship contribute to the body of information required for a rational design of flavin-based tools for future biological and biochemical applications.
- A background-priority discrete boundary triangulation methodPublication . Loke, R. E.; Jansen, F. W.; du Buf, J. M. H.Discrete boundary triangulation methods generate triangular meshes through the centers of the boundary voxels of a volumetric object. At some voxel configurations it may be arbitrary whether a part of the volume should be included in the object or could be classified as background. Consequently, important details such as concave and convex edges and corners are not consistently preserved in the describing geometry. We present a "background priority" version of an existing "object priority" algorithm [6]. We show that the ad hoc configurations of the well-known Discretized Marching Cubes algorithm [13] can be derived from our method and that a combined triangulation with "object priority" and "background priority" better would preserve object details.