ISEL - Engenharia Química e Biológica
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- 1D Copper(II)-aroylhydrazone coordination polymers: magnetic properties and microwave assisted oxidation of a secondary alcoholPublication . Sutradhar, Manas; Alegria, Elisabete; Roy Barman, Tannistha; Guedes Da Silva, M. Fátima C.; Liu, Cai-Ming; Pombeiro, ArmandoThe 1D Cu(II) coordination polymers [Cu-3(L-1)(NO3)(4)(H2O)(2)](n) (1) and [Cu-2(H2L2)(NO3)(H2O)(2)](n)(NO3)(n) (2) have been synthesized using the aroylhyrazone Schiff bases N'(1),N'(2)-bis(pyridin-2-ylmethylene)oxalohydrazide (H2L1) and N'(1),N'(3)-bis(2-hydroxybenzylidene)malonohydrazide (H4L2), respectively. They have been characterized by elemental analysis, infrared (IR) spectroscopy, UV-Vis spectroscopy, electrospray ionization mass spectrometry (ESI-MS), single crystal X-ray diffraction and variable temperature magnetic susceptibility measurements (for 2). The ligand (L-1)(2-) coordinates in the iminol form in 1, whereas the amide coordination is observed for (H2L2)(2-) in 2. Either the ligand bridge or the nitrate bridge in 2 mediates weak antiferromagnetic coupling. The catalytic performance of 1 and 2 has been investigated toward the solvent-free microwave-assisted oxidation of a secondary alcohol (1-phenylethanol used as model substrate). At 120 degrees C and in the presence of the nitroxyl radical 2,2,6,6-tetramethylpiperydil-1-oxyl (TEMPO), the complete conversion of 1-phenylethanol into acetophenone occurs with TOFs up to 1,200 h(-1).
- 1D Zn(II) coordination polymer of arylhydrazone of 5,5-dimethylcyclohexane-1,3-dione as a pre-catalyst for the Henry reactionPublication . Martins, Nuno M. R.; Mahmudov, Kamran T.; Silva, M. Fátima C. Guedes; Martins, Luisa; Guseinov, Firudin I.; Pombeiro, Armando J. L.Reaction of a new hydrazone of β-diketone, 5-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)isophthalic acid (H3L), with zinc(II) nitrate hexahydrate in a mixture of DMF and water (1:1) under hydrothermal conditions affords the 1D coordination polymer [Zn(μ3-HL)(H2O)2]n ∙ nH2O (1), where one of the carboxylic groups links two Zn(II) centers in a bridging bidentate (syn-syn-type) mode and the remaining one ligates a third metal cation in a monodentate fashion. It was characterized by IR and NMR spectroscopies, ESI-MS, elemental and single-crystal X-ray crystal structural analyses. 1 acts as an efficient pre-catalyst for the Henry reaction at 40 °C in aqueous medium, providing β-nitroalcohols with good yields (67–86%) and diastereoselectivities (syn:anti 77:23–69:31).
- Action of euptox A from Ageratina adenophora juice on human cell lines: a top-down study using FTIR spectroscopy and protein profilingPublication . André, Rebeca; Catarro, Joana; Freitas, Dalia; Pacheco, Rita; Oliveira, Maria Conceição; Serralheiro, Maria Luisa; Fale, PedroEuptox A, from Ageratina adenophora juice, is a toxin associated with the plant's resistance to infections, invasiveness and traditional use in cancer treatment. We used FTIR spectroscopy and protein profiling of cell lines to study the impact of euptox A on human cells, to clarify its mechanism of action in a top-down approach. Euptox A was extracted from the juice of A. adenophora. Its stability in the gastrointestinal tract was evaluated, as the compound/juice is generally taken orally. Cytotoxicity was determined in HeLa, Caco-2 and MCF7 cells, and the mechanism of action analyzed by protein and metabolite profiles using electrophoresis and FTIR spectroscopy. Euptox A resisted gastrointestinal digestion and was the most cytotoxic component of the extract for all cell lines tests. Euptox A-treated HeLa cells showed changes in protein profile, especially on 40S ribosomal protein S8 (RP), generally associated with cancer cells. FTIR profiles of treated cells diverged in the same metabolites as cells treated with cisplatin, both in metabolite directed analysis and in multivariate analysis (principal component analysis). In conclusion, euptox A in this top-down study showed a cellular impact that suggests a strong potential against cancer, acting on cancer targeted cellular characteristics.
- Active and passive behaviors of soft tissues: Pelvic floor musclesPublication . Pato, Matilde Pós de Mina; Areias, P.: A new active-contraction visco-elastic numerical model of the pelvic floor (skeletal) muscle is presented. Our model includes all elements that represent the muscle constitutive behavior, contraction and relaxation. In contrast with the previous models, the activation function can be null. The complete equations are shown and exactly linearized. Small verification and validation tests are performed and the pelvis is modeled using the data from the intra-abdominal pressure tests
- Acylated cyanoimido-complexes trans-[Mo(NCN){NCN(O)R}(DPPE)(2)]Cl and their reactons with electrophiles: Chemical, electrochemical and theoretical studyPublication . Alegria, Elisabete; Silva, Maria de Fátima Costa Guedes da; Kuznetsov, Maxim L.; Cunha, S. M. P. R. M.; Martins, Luisa; Pombeiro, ArmandoTreatment of a dichloromethane solution of trans-[Mo(NCN){NCNC(O)R}(dppe)(2)]Cl [R = Me (1a), Et (1b)] (dppe = Ph2PCH2CH2PPh2) with HBF4, [Et3O][BF4] or EtC(O)Cl gives trans-[Mo(NCN)Cl-(dppe)(2)]X [X = BF4 (2a) or Cl (2b)] and the corresponding acylcyanamides NCN(R')C(O)Et (R' = H, Et or C(O)Et). X-ray diffraction analysis of 2a (X = BF4) reveals a multiple-bond coordination of the cyanoimide ligand. Compounds 1 convert to the bis(cyanoimide) trans-[Mo(NCN)(2)(dppe)(2)] complex upon reaction with an excess of NaOMe (with formation of the respective ester). In an aprotic medium and at a Pt electrode, compounds 1 (R = Me, Et or Ph) undergo a cathodically induced isomerization. Full quantitative kinetic analysis of the voltammetric behaviour is presented and allows the determination of the first-order rate constants and the equilibrium constant of the trans to cis isomerization reaction. The mechanisms of electrophilic addition (protonation) to complexes 1 and the precursor trans[Mo(NCN)(2)(dppe)(2)], as well as the electronic structures, nature of the coordination bonds and electrochemical behaviour of these species are investigated in detail by theoretical methods which indicate that the most probable sites of the proton attack are the oxygen atom of the acyl group and the terminal nitrogen atom, respectively.
- Adsorption of a textile dye on commercial activated carbon: a simple experiment to explore the role of surface chemistry and ionic strengthPublication . Martins, Angela; Nunes, NelsonIn this study, an adsorption experiment is proposed using commercial activated carbon as adsorbent and a textile azo dye, Mordant Blue-9, as adsorbate. The surface chemistry of the activated carbon is changed through a simple oxidation treatment and the ionic strength of the dye solution is also modified, simulating distinct conditions of water hardness. The purpose of this experimental work, directed to undergraduate (second-year) students is to allow them to understand the influence of surface chemistry and ionic strength on the interaction between the carbon surface and the dye molecule.
- Adsorption of myoglobin on calixarenes and biocatalysis in organic mediaPublication . Semedo, Magda C.; Karmali, Amin; Barata, Patrícia; Prata, José V.Derivatives of p-tert-butylcalix[4,6,8]arene carboxylic acids were used for selective adsorption of myoglobin.Amixtureofmyoglobin,laccaseandperoxidase wasusedforextractionwithcalixarenesandonlymyoglobin was selectively extracted to organic media. Myoglobin and Mb c–calixarene exhibited pseudoactivity of peroxidase in aqueous and organic media. This protein-calixarene complex exhibited the highest specific activity of 1.37 × 10−1 U.mg protein−1 at initial pH 6.5 of myoglobin aqueous solution. Apparent kinetic parameters (V max, K m, k cat and k cat/K m) for the pseudoperoxidase activity were determined in organic media for different initial pH values of myoglobin aqueous solution by Michaelis-Menten plot. The stability of this complex was studied for different initial pH values and t1/2 values were obtained in the range of 3.5–5.2 days. The extracted Mb c in organic media was recovered into fresh aqueous solutions at alkaline pH with a recovery of pseudoperoxidase activity of over 100%.
- Advanced instrumental approaches for chemical characterization of indoor particulate matterPublication . Duarte, Regina; Gomes, João; Querol, Xavier; Cattaneo, Andrea; Bergmans, Benjamin; Saraga, Dikaia; MAGGOS, THOMAS; Di Gilio, Alessia; Rovelli, Sabrina; Villanueva, FlorentinaParticulate matter (PM) is an important player of indoor air quality and a topic of great interest in terms of public health. Deciphering the complex chemical composition of indoor PM is critical to understand the association between particles components and a wide range of adverse health effects. Over the last decades, advanced analytical instrumentation has been produced capable of providing various levels of information on the chemical features of indoor PM. This article reviews the most promising of these sophisticated analytical techniques that could be employed in the identification of organic and inorganic constituents of indoor PM, including (high-resolution) mass spectrometry, organic, carbonaceous and ions analytical techniques, elemental analysis techniques such as atomic spectrometry and X-ray based methods, and surface analysis techniques. A distinction is made between online and offline instrumentation, focusing on their capabilities and how they are currently being used in the targeted and untargeted analysis of PM components. This review aims to provide the indoor air chemistry community with insights into the power of the different techniques available today, so that they can be used advantageously in future studies.
- Advances on the development of novel heterogeneous catalysts for transesterification of triglycerides in biodieselPublication . Puna, Jaime; Gomes, João; Correia, M. Joana N.; Dias, A. P. Soares; Bordado, J. C.This paper describes experimental work done towards the search for more profitable and sustainable alternatives regarding biodiesel production, using heterogeneous catalysts instead of the conventional homogenous alkaline catalysts, such as NaOH, KOH or sodium methoxide, for the methanolysis reaction. This experimental work is a first stage on the development and optimization of new solid catalysts, able to produce biodiesel from vegetable oils. The heterogeneous catalytic process has many differences from the currently used in industry homogeneous process. The main advantage is that, it requires lower investment costs, since no need for separation steps of methanol/catalyst, biodiesel/catalyst and glycerine/catalyst. This work resulted in the selection of CaO and CaO modified with Li catalysts, which showed very good catalytic performances with high activity and stability. In fact FAME yields higher than 92% were observed in two consecutive reaction batches without expensive intermediate reactivation procedures. Therefore, those catalysts appear to be suitable for biodiesel production.
- Ageing effects on the wettability behavior of laser textured siliconPublication . Nunes, B.; Serro, A. P.; Oliveira, Vitor; Montemor, M. F.; Alves, E.; Saramago, B.; Colaço, R.In the present work we investigate the ageing of acid cleaned femtosecond laser textured < 100 > silicon surfaces. Changes in the surface structure and chemistry were analysed by Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS), in order to explain the variation with time of the water contact angles of the laser textured surfaces. It is shown that highly hydrophobic silicon surfaces are obtained immediately after laser texturing and cleaning with acid solutions (water contact angle >120 degrees). However these surfaces are not stable and ageing leads to a decrease of the water contact angle which reaches a value of 80 degrees. XPS analysis of the surfaces shows that the growth of the native oxide layer is most probably responsible for this behavior. (C) 2010 Elsevier B.V. All rights reserved.