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Soubal J.P.,CQB | Pena L.,CQB | Santana D.,CQB | Valdes Y.,CQB | And 5 more authors.
Biotecnologia Aplicada | Year: 2013

Streptococcus pneumoniae causes annually 826 000 deaths in children under fi ve years. The serotype 6B, one ofhigher incidence, is targeted by the Cuban research and development project to develop a conjugate vaccine. There is limited data on how modifi cations caused by conjugation affect the physicochemical and antigenic characteristicsof polysaccharides, particularly for serotype 6B capsular polysaccharide (PS6B), despite being the least immunogenicamong S. pneumoniae polysaccharides. In this work, a conjugation procedure was established for PS6B comprising:fragmentation by acid hydrolysis, activation by periodate oxidation, and conjugation to tetanus toxoid (TT) by reductive amination to increase its immunogenicity. Reaction conditions were set to obtain the polysaccharide in three molecular size ranges (1-10, 10-30, 30-100 kDa) and levels of oxidation. PS6B fragmentation below 10 kDa and oxidation above 24 % of the repetitive units implied the loss of antigenicity. Polysaccharide length but not oxidation level had an impact on the physicochemical characteristics of the conjugates in the tested conditions. Unlike the native polysaccharide, conjugated 10-30 kDa and 30-100 kDa PS6B were immunogenic in rabbits, with evidence of thymus-dependent response. The procedure described supports obtaining PS6B-TT conjugates reproducibly in the 30- 100 kDa and 10-30 kDa molecular size ranges and with 8-18 % oxidized repeat units, which are immunogenic. © Biotecnología Aplicada 2013.

Veiros L.F.,University of Lisbon | Honzicek J.,New University of Lisbon | Romao C.C.,New University of Lisbon | Calhorda M.J.,CQB
Inorganica Chimica Acta | Year: 2010

Spiro[2,4]hepta-4,6-diene and spiro[4,4]nona-1,3-diene react with [Mo(CO)2Cp'(NCCH3)2][BF4] (Cp' = Cp, Ind; Ind = η5-C9H7) to afford the corresponding diene complex [Mo(diene)(CO)2Cp′]+. When Cp' = Ind, the reaction proceeded forward leading to ring opening in the case of the small spiro ring. Although this and another product resulting from migration of the side arm to the carbonyl were detected when Cp' = Cp, they did not form from the diene complex. A DFT/PBE1PBE study was carried out and showed a kinetically controlled reaction pathway leading from the [Mo(diene)(CO)2Ind]+ to the reaction product, with an activation barrier of 21.3 kcal mol-1. The thermodynamic preferred species was the non-observed complex (insertion), and its formation required higher barriers. In the presence of Cp, all the barriers increased significantly, explaining the inertness of the initial diene complex. The interpretation of this behaviour is associated with the ease of the η5 → η3 haptotropic rearrangement of the indenyl, which helps to lower some relevant barriers. This route is not available for the Cp analogue. © 2009 Elsevier B.V. All rights reserved.

Saraiva M.S.,CQB | Nunes C.D.,CQB | Nunes T.G.,University of Lisbon | Calhorda M.J.,CQB
Journal of Molecular Catalysis A: Chemical | Year: 2010

The two complexes [Mo(η3-C3H5)Br(CO)2(L)] (L = L1, C1, and L2, C2), where L1 and L2 are the ligands 2-(2′-pyridyl)imidazole (L1, pym) and 2-(2′-pyridyl)benzimidazole (L2, pyb) were immobilized in mesoporous MCM-41 and in Mg/Al hydrotalcite (HTC), in order to obtain new heterogeneous catalysts. Both the ligands and the complexes reacted with MCM-41 functionalized with a chloropropyl pendant arm; in the first approach, the immobilized ligands were then allowed to react with [Mo(η3-C3H5)Br(CO)2(NCMe)2] to afford supported C1 and C2. While spectroscopic data, DRX, and nitrogen isotherm adsorptions revealed the similarity of the two kinds of materials, and the preservation of the MCM characteristic structure, elemental analysis showed that the stepwise approach (ligand + complex precursor) allowed the introduction of a much larger amount of molybdenum. The attempts at immobilization of the complexes in HTC were less successful. Neither the deprotonated ligands or complexes were able to intercalate between the material layers, the experimental evidence suggesting the intercalation of OH- anions and the adsorption of the deprotonated ligands or complexes on the outside of the clay. Both materials exhibited higher activities in the epoxidation of cycloctene and styrene, in the presence of TBHP, than the free complexes in homogeneous conditions, with conversions close to 100% for both substrates, in the MCM based materials prepared through a stepwise route. © 2010 Elsevier B.V. All rights reserved.

Paixao V.,Polytechnic Institute of Lisbon | Carvalho A.P.,CQB | Rocha J.,University of Aveiro | Fernandes A.,University of Lisbon | Martins A.,Polytechnic Institute of Lisbon
Microporous and Mesoporous Materials | Year: 2010

The effect of several desilication experimental parameters (base concentration, temperature and time) on the characteristics of MOR zeolite was studied. The samples were characterized by X-ray diffraction, 27Al and 29Si MAS-NMR, chemical analysis, and FTIR (framework vibration region). The textural characterization was made by N2 adsorption and the acidity was evaluated by pyridine adsorption followed by FTIR and by the catalytic model reaction of n-heptane cracking. The alkaline treatments promoted the Si extraction from the zeolite framework, without considerable loss of crystallinity and, as it was envisaged, an important increase of the mesoporous structure was attained. A linear correlation between the number of framework Si per unit cell, NSi, and the asymmetric stretching wavenumber, ν1, was observed. The acidity characterization shows that the desilicated samples exhibit practically the same acid properties than the parent HMOR zeolite. The optimum desilication conditions were those used to obtain sample M/0.2/85/2, i.e., sample treated with 0.2 M NaOH solution at 85 °C for 2 h. © 2010 Elsevier Inc. All rights reserved.

Quintal S.,CQB | Concepcion Gimeno M.,University of Zaragoza | Laguna A.,University of Zaragoza | Calhorda M.J.,CQB
Journal of Organometallic Chemistry | Year: 2010

The reactions between five ferrocenyl derivatives containing both a C{double bond, long}O and at least an imidazole or pyridine nitrogen atom and AgPF6, AgOTf, or [Cu(NCCH3)4]PF6 precursors were studied. The ligand {[bis(2-pyridyl)amino]carbonyl}ferrocene (L3), derived from (2-pyridyl)amine, favored tetrahedral coordination of Ag+ (with two ligands) and of Cu+ (with two acetonitrile ligands left from the precursor). In all the other ligands, both metal centers coordinated linearly to two ligands, preferring the imidazole or pyridinic nitrogen to other nitrogen atoms (amine) or oxygen donors. When the counter anions were triflate, the crystal structure showed a dimerization of the complex, with the ferrocenyl moieties occupying cis positions, by means of a weak Ag⋯Ag interaction. This was shown experimentally in the crystal structure of complex [Ag(L1)2]OTf (L1 = ferrocenyl imidazole) and in the presence of peaks corresponding to {Ag2(L2)3(OTf)}+ and {Ag2(L2)4(OTf)}+ in the mass spectra of [Ag(L2)2]OTf (L2 = ferrocenyl benzimidazole). In all complexes containing PF6, there was no evidence for dimerization. Indeed, in the crystal structure of [Ag(L2)2]PF6, the ferrocenyl moieties occupy trans positions and the metal centers are far from each other. DFT calculations showed that the energy of the cis and trans conformers is practically the same and the balance of crystal packing forces leads to dimerization when triflate is present. © 2009 Elsevier B.V. All rights reserved.

Ruiz B.,CSIC - National Coal Institute | Cabrita I.,CQB | Mestre A.S.,CQB | Parra J.B.,CSIC - National Coal Institute | And 3 more authors.
Applied Surface Science | Year: 2010

The removal of a compound with therapeutic activity (paracetamol) from aqueous solutions using chemically modified activated carbons has been investigated. The chemical nature of the activated carbon material was modified by wet oxidation, so as to study the effect of the carbon surface chemistry and composition on the removal of paracetamol. The surface heterogeneity of the carbon created upon oxidation was found to be a determinant in the adsorption capability of the modified adsorbents, as well as in the rate of paracetamol removal. The experimental kinetic data were fitted to the pseudo-second order and intraparticle diffusion models. The parameters obtained were linked to the textural and chemical features of the activated carbons. After oxidation the wettability of the carbon is enhanced, which favors the transfer of paracetamol molecules to the carbon pores (smaller boundary layer thickness). At the same time the overall adsorption rate and removal efficiency are reduced in the oxidized carbon due to the competitive effect of water molecules. © 2010 Elsevier B.V. All rights reserved.

Borrego T.,University of Porto | Andrade M.,CQB | Pinto M.L.,CQB | Pinto M.L.,University of Aveiro | And 5 more authors.
Journal of Colloid and Interface Science | Year: 2010

Silylation of several materials where the surface area arises from the internal pores (MCM-41 and FSM-16) or is essentially external (silica gel, and clays) was performed using three organosilanes: (3-aminopropyl)triethoxysilane (APTES), 4-(triethoxysilyl)aniline (TESA) and (3-mercaptopropyl)trimethoxysilane (MPTS). The materials were characterized by nitrogen adsorption-desorption at -196 °C, powder XRD, XPS, bulk chemical analysis, FTIR and 29Si and 13C MAS NMR. For MCM-41 and FSM-16 the highest amounts of organosilane are obtained for APTES, while for the remaining materials the highest amounts are for MPTS; TESA always anchored with the lowest percentage. In terms of surface chemical analysis, TESA anchored with the highest contents irrespectively of the material, and the opposite is registered for MPTS. Comparison of bulk vs surface contents indicate that TESA is mainly anchored at the material external surface. Moreover, with N or S (surface and bulk) contents expressed per unit of surface area, MCM-41 and FSM-16 (internal porosity) show the lowest amounts of silane; the highest amounts of silane per unit of surface area are obtained for the clays. Grafting of the organosilanes to the surface hydroxyl groups was corroborated by FTIR and 29Si and 13C MAS NMR. Furthermore, NMR data suggested that TESA and APTES grafted mostly through a bidentate approach, whereas MPTS grafted by a monodentate mechanism. © 2010 Elsevier Inc. All rights reserved.

Ribeiro-Claro P.J.A.,University of Aveiro | Vaz P.D.,CQB | Nolasco M.,University of Aveiro
Journal of Molecular Structure: THEOCHEM | Year: 2010

In this work, the usefulness of the Pairs in Molecular Materials (PiMM) approach to elucidate unknown structures of molecular crystals is assessed. This methodology aims to assist the prediction of probable crystal structures from the vibrational spectra, through the identification of the most relevant motifs in the potential energy landscape of the crystal. The method is successfully applied to the elucidation of 4-(dimethylamino)benzaldehyde crystal structure, considered to be "unknown" to illustrate the applicability of the PiMM approach. The proposed crystal structure, based on weak CH⋯O hydrogen bonding and π-stacking interactions, is in full agreement with the recently reported crystal structure. © 2010 Elsevier B.V. All rights reserved.

Melato A.I.,CQB | Abrantes L.M.,CQB | Botelho do Rego A.M.,Institute of Nanoscience and Nanotechnology IN
Thin Solid Films | Year: 2010

Poly(3,4-ethylenedioxythiophene) (PEDOTh) films were potentiodynamically deposited on platinum from tetrabutylammonium hexafluorophosphate/acetonitrile solutions. Polymers prepared with different number of cycles showed reversible redox behaviour and the X-ray Photoelectron Spectroscopy (XPS) characterization revealed the existence of zones with different conductivity and confirmed the presence of PF6 -. The incorporation of the metallic complex Fe(CN)6 3- in the PEDOTh films was made in one step, after the electrosynthesis of a film grown with a given number of potential cycles, and by means of polymerization/incorporation sequences. XPS data confirmed the presence of the inorganic species and the highest Fe 2p3/2 peak intensity was observed for thin films (30 cycles) when the one step incorporation has been used. The XPS results suggest a partial dissociation of the Fe-(C-N) bond of the complex in the modified electrodes. © 2009 Elsevier B.V. All rights reserved.

Mestre A.S.,CQB | Pinto M.L.,CQB | Pires J.,CQB | Nogueira J.M.F.,CQB | Carvalho A.P.,CQB
Carbon | Year: 2010

Clofibric acid adsorption from the aqueous phase was studied using cork-based activated carbons (CAC: chemically activated with K2CO3; CPAC: physical activation of sample CAC with steam). CPAC outperformed the uptake of water treatment commercial carbons. Results highlight the importance of pH in clofibric acid adsorption: the highest removals were obtained for pH 2.0 and decrease for higher pHs. The sigmoidal adsorption isotherms obtained were fitted to the Dubinin-Astakhov equation. The characteristic adsorption energy revealed that CAC has the highest affinity for the solute, in accordance with its narrow micropore size distribution. The molecular and electronic structure showed that the solvation energy of the undissociated and dissociated forms of clofibric acid is the key factor to explain the isotherm shape and the dependence of the pH. For pH 3.6 the dissociated form is dominant and the uptake significantly decreases, showing that the solvent shields the interaction of the dissociated specie (higher solvation energy) with the carbon surface. The results show that once the solvation energies of the undissociated and dissociated forms of clofibric acid are known, a complete characterization of an activated carbon allows one to predict with confidence its behavior for the adsorption of this compound from the aqueous phase. © 2009 Elsevier Ltd. All rights reserved.

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