127 results on '"Sastre G"'
Search Results
102. CFA-1: the first chiral metal-organic framework containing Kuratowski-type secondary building units.
- Author
-
Schmieder P, Denysenko D, Grzywa M, Baumgärtner B, Senkovska I, Kaskel S, Sastre G, van Wüllen L, and Volkmer D
- Abstract
The novel homochiral metal-organic framework CFA-1 (Coordination Framework Augsburg-1), [Zn5(OAc)4(bibta)3], containing the achiral linker {H2-bibta = 1H,1'H-5,5'-bibenzo[d][1,2,3]triazole}, has been synthesised. The reaction of H2-bibta and Zn(OAc)2·2H2O in N-methylformamide (NMF) (90 °C, 3 d) yields CFA-1 as trigonal prismatic single crystals. CFA-1 serves as a convenient precursor for the synthesis of isostructural frameworks with redox-active metal centres, which is demonstrated by the postsynthetic exchange of Zn(2+) by Co(2+) ions. The framework is robust to solvent removal and has been structurally characterized by synchrotron single-crystal X-ray diffraction and solid state NMR measurements ((13)C MAS- and (1)H MAS-NMR at 10 kHz). Results from MAS-NMR and IR spectroscopy studies are corroborated by cluster and periodic DFT calculations performed on CFA-1 cluster fragments.
- Published
- 2013
- Full Text
- View/download PDF
103. Drug-Drug Interactions within Protein Cavities Probed by Triplet-Triplet Energy Transfer.
- Author
-
Nuin E, Jiménez MC, Sastre G, Andreu I, and Miranda MA
- Abstract
A new direct and noninvasive methodology based on transient absorption spectroscopy has been developed to probe the feasibility of drug-drug interactions within a common protein binding site. The simultaneous presence of (R)-cinacalcet (CIN) and (S)-propranolol (PPN) within human or bovine α1-acid glycoproteins (AAGs) is revealed by detection of (3)CIN* as the only transient species after laser flash photolysis of CIN/PPN/AAG mixtures at 308 nm. This is the result of triplet-triplet energy transfer from (3)PPN* to CIN, which requires close contact between the two drugs within the same biological compartment. Similar results are obtained with nabumetone and CIN as donor/acceptor partners. This new methodology can, in principle, be extended to a variety of drug/drug/biomolecule combinations.
- Published
- 2013
- Full Text
- View/download PDF
104. Macronutrients during pregnancy and life-threatening respiratory syncytial virus infections in children.
- Author
-
Ferolla FM, Hijano DR, Acosta PL, Rodríguez A, Dueñas K, Sancilio A, Barboza E, Caría A, Gago GF, Almeida RE, Castro L, Pozzolo C, Martínez MV, Grimaldi LA, Rebec B, Calvo M, Henrichsen J, Nocito C, González M, Barbero G, Losada JV, Caballero MT, Zurankovas V, Raggio M, Schavlovsky G, Kobylarz A, Wimmenauer V, Bugna J, Williams JV, Sastre G, Flamenco E, Pérez AR, Ferrero F, Libster R, Grijalva CG, and Polack FP
- Subjects
- Acute Disease, Area Under Curve, Argentina, Developing Countries, Diet Surveys, Female, Hospitalization, Humans, Incidence, Infant, Logistic Models, Male, Poverty, Pregnancy, Prospective Studies, Respiratory Syncytial Viruses, Respiratory Tract Infections diagnosis, Respiratory Tract Infections epidemiology, Seasons, Dietary Carbohydrates adverse effects, Prenatal Nutritional Physiological Phenomena physiology, Respiratory Syncytial Virus Infections epidemiology, Respiratory Tract Infections virology
- Abstract
Rationale: Respiratory syncytial virus (RSV) is an important cause of hospitalization and death in infants worldwide. Most RSV deaths occur in developing countries, where burden and risk factors for life-threatening illness are unclear., Objectives: We defined the burden of life-threatening (O(2) saturation [O(2) sat] ≤ 87%) and fatal RSV infection, and characterized risk factors for life-threatening disease in hospitalized children. Special emphasis was placed on studying the impact of dietary habits during pregnancy. We hypothesized that dietary preferences, differing from those of our remote ancestors, would negatively impact children's pulmonary health. For instance, a diet rich in carbohydrates is a signature of recent millennia and typical of low-income populations, heavily burdened by life-threatening RSV disease., Methods: Prospective study in a catchment population of 56,560 children under 2 years of age during the RSV season in Argentina. All children with respiratory signs and O(2) sat less than 93% on admission were included., Measurements and Main Results: Among 1,293 children with respiratory infections, 797(61.6%) were infected with RSV: 106 of these had life-threatening disease; 1.9 per 1,000 children (95% confidence interval [CI], 1.5-2.2/1,000) under 24 months. A total of 22 hospitalized children died (9 RSV(+)), 26 died at home due to acute respiratory infection (14 attributed to RSV); all were under 12 months old. The annual attributable mortality rate for RSV was 0.7 per 1,000 infants (95% CI, 0.4-1.1/1,000). Life-threatening disease was dose-dependently associated with carbohydrate ingestion during pregnancy (adjusted odds ratio from 3.29 [95% CI, 1.15-9.44] to 7.36 [95% CI, 2.41-22.5] versus the lowest quartile)., Conclusions: Life-threatening and fatal RSV infections are a heavy burden on infants in the developing world. Diets rich in carbohydrates during pregnancy are associated with these severe outcomes.
- Published
- 2013
- Full Text
- View/download PDF
105. Simulating the properties of small pore silica zeolites using interatomic potentials.
- Author
-
Combariza AF, Gomez DA, and Sastre G
- Abstract
Despite the sustained use of forcefield methodologies to study SiO(2) polymorphs few reviews on the subject are available in the literature. The present study is an attempt to help fill this gap, focusing on classical forcefields used to reproduce and predict properties of pure silica zeolites (or zeosils) such as cell parameters, SiO distance and especially pore size. Instead of an exhaustive study we have focused on an application where diffusion of hydrocarbons makes important the use of pure silica zeolites. A particular area of interest is small pore zeosils containing 8-rings as the largest window, which are industrially interesting for their ability to perform kinetic separations of mixtures of C3 hydrocarbon molecules whose dimensions are of similar characteristics. A set of forcefields have been selected from the literature to analyze their accuracy and transferability when predicting structural, mechanical and dynamical properties of small pore pure silica zeolites and their performance at selective diffusion of C3 hydrocarbons.
- Published
- 2013
- Full Text
- View/download PDF
106. Confinement effects in the hydrogen adsorption on paddle wheel containing metal-organic frameworks.
- Author
-
Gomez DA, Combariza AF, and Sastre G
- Abstract
The confinement effects upon hydrogen adsorption in Cu(II)-paddle wheel containing metal-organic frameworks (MOFs) were evaluated and rationalized in terms of the structural properties (cavity types and pore diameters) of PCN-12, HKUST-1, MOF-505, NOTT-103 and NOTT-112. First-principles calculations were employed to identify the strongest adsorption positions at the paddle wheel inorganic building unit (IBU). The adsorption centres due to confinement were located through analysis of 3D occupancy maps obtained from the hydrogen trajectories computed via molecular dynamics simulations. It was found that the confinement enhances the adsorption on the weakest adsorption centres around the IBU in regions close to the narrowest windows and promotes the formation of new adsorption regions into the small cavities. Our results indicate that at low pressure, the high H(2) uptake in these materials is partly due to the presence of small cavities (5.3-8.5 Å) or narrow windows where the long-range contribution to the adsorption becomes important. Conversely, confinement effects in cavities with diameters >12 Å were not observed.
- Published
- 2012
- Full Text
- View/download PDF
107. From microscopic insights of H2 adsorption to uptake estimations in MOFs.
- Author
-
Gomez DA and Sastre G
- Abstract
The adsorption of hydrogen in MOFs takes place mainly close to the inorganic secondary building unit (IBU). The adsorption capacities on MIL-88, UiO-66, MIL-47 and MFU-1 were investigated. Quantum chemical calculations at the ab initio HF/MP2 theoretical level were employed to estimate the maximum uptake of H(2) molecules per metallic centre. Extrapolating the results on small clusters to the unit cell of each particular MOF, the H(2) uptakes (gravimetric and volumetric) were estimated. The loading of hydrogen per metal atom (H(2) molecules/M-atom) and the density of metal atoms (M-atoms Å(-3)) were defined as useful parameters to assess hydrogen storage properties and to estimate the optimum density that the material should have to be a good H(2) adsorbent. It was found that values above 3 H(2) molecules/M-atom and around 0.004 M-atoms Å(-3) for MOFs with densities around 0.7-1.0 g cm(-3) are required to reach the 2015 storage targets.
- Published
- 2011
- Full Text
- View/download PDF
108. Dansyl labeling to modulate the relative affinity of bile acids for the binding sites of human serum albumin.
- Author
-
Rohacova J, Sastre G, Marin ML, and Miranda MA
- Subjects
- Binding Sites, Energy Transfer, Humans, Spectrometry, Fluorescence, Affinity Labels chemistry, Cholic Acids chemistry, Phosphatidylcholines chemistry, Serum Albumin chemistry
- Abstract
Binding of natural bile acids to human serum albumin (HSA) is an important step in enterohepatic circulation and provides a measure of liver function. In this article, we report on the use of four dansyl (Dns) derivatives of cholic acid (ChA) to demonstrate a regiodifferentiation in their relative affinity for the two binding sites of HSA. Using both steady-state and time-resolved fluorescence, formation of Dns-ChA@HSA complexes was confirmed; the corresponding binding constants were determined, and their distribution between bulk solution and HSA microenvironment was estimated. By means of energy transfer from Trp to the Dns moiety, donor-acceptor distances were estimated (21-25 Å) and found to be compatible with both site 1 and site 2 occupancies. Nevertheless, titration using warfarin and ibuprofen as specific displacement probes clearly indicated that 3α- and 3β-Dns-ChA bind to HSA at site 2, whereas their C-7 regioisomers bind to HSA at site 1. Furthermore, the C-3-labeled compounds are displaced by lithocholic acid, whereas they are insensitive to ChA, confirming the assumption that the former binds to HSA at site 2. Thus, Dns labeling provides a useful tool to modulate the relative affinity of ChA to the major binding sites of HSA and, in combination with other fluorescent ChA analogs, to mimic the binding behavior of natural bile acids.
- Published
- 2011
- Full Text
- View/download PDF
109. Photophysical properties of Kuratowski-type coordination compounds [M(II)Zn4Cl4(Me2bta)6] (M(II) = Zn or Ru) featuring long-lived excited electronic states.
- Author
-
Liu YY, Grzywa M, Tonigold M, Sastre G, Schüttrigkeit T, Leeson NS, and Volkmer D
- Abstract
The syntheses of Kuratowski-type pentanuclear clusters featuring {MZn(4)Cl(4)} cores (M(II) = Ru or Zn) that incorporate triazolate ligands are described. The coordination compounds are characterized by single-crystal X-ray diffraction, X-ray powder diffraction (XRD), FTIR- and UV-vis spectroscopy. [Ru(II)Zn(4)Cl(4)(Me(2)bta)(6)]·2DMF (Me(2)bta(-) = 5,6-dimethyl-1,2,3-benzotriazolate) (1) crystallizes in the cubic system, while [Zn(5)Cl(4)(ta)(6)] (ta(-) = 1,2,3-triazolate) (3) crystallizes in the tetragonal system. Both compounds feature structurally similar cluster topologies in which the central octahedrally coordinated metal ion is coordinated to six triazolate ligands. Each triazolate ligand is coordinated with two zinc ions (μ(3)-bridging mode), leading altogether to a pentanuclear cluster of T(d) point group symmetry. Photophysical investigations reveal that compound [Zn(5)Cl(4)(Me(2)bta)(6)]·2DMF (2) shows a short-lived excited electronic state, which can be populated with high quantum yield. The isostructural compound [Ru(II)Zn(4)Cl(4)(Me(2)bta)(6)]·2DMF (1), on the other hand, shows a long-lived photoexcited state, owing to an internal singlet to triplet conversion of the electronic states, as revealed by time-resolved fluorescence spectroscopy. Insights gained from these studies open up novel design strategies towards photocatalytically active metal-organic frameworks incorporating photoactive Kuratowski-type secondary building units such as MFU-4 (Metal-Organic Framework Ulm University-4).
- Published
- 2011
- Full Text
- View/download PDF
110. Ammonia IRMS-TPD measurements on Brønsted acidity of proton-formed SAPO-34.
- Author
-
Suzuki K, Nishio T, Katada N, Sastre G, and Niwa M
- Abstract
By utilizing the advantages of a combined method of IRMS-TPD of ammonia and DFT calculations, the solid acidity of HSAPO-34 was studied. The number, strength and structure of the Brønsted OH were measured experimentally. The quantitative measurements and DFT calculations supported the identification of Brønsted OH to account for the generation model of the Brønsted OH primarily located in the edge of the Si domain (island). The acid strength of SAPO-34 was slightly weaker than that of chabazite, a zeolite with the same structure. Thus, some important insights were obtained to understand the acid site generation of SAPO-34.
- Published
- 2011
- Full Text
- View/download PDF
111. Modular organic structure-directing agents for the synthesis of zeolites.
- Author
-
Simancas R, Dari D, Velamazán N, Navarro MT, Cantín A, Jordá JL, Sastre G, Corma A, and Rey F
- Abstract
Organic structure-directing agents (OSDAs) are used to guide the formation of particular types of pores and channels during the synthesis of zeolites. We report that the use of highly versatile OSDAs based on phosphazenes has been successfully introduced for the synthesis of zeolites. This approach has made possible the synthesis of the elusive boggsite zeolite, which is formed by 10- and 12-ring intersecting channels. This topology and these pore dimensions present interesting opportunities for catalysis in reactions of industrial relevance.
- Published
- 2010
- Full Text
- View/download PDF
112. Multifunctional hybrid organic-inorganic catalytic materials with a hierarchical system of well-defined micro- and mesopores.
- Author
-
Corma A, Díaz U, García T, Sastre G, and Velty A
- Abstract
Novel layered zeolitic organic-inorganic materials (MWW-BTEB) have been synthesized by intercalation and stabilization of arylic silsesquioxane molecules between inorganic zeolitic MWW layers. The organic linkers are conformed by two condensed silyl-arylic groups from disilane molecules, such as 1,4-bis(triethoxysilyl)benzene (BTEB), which react with the external silanol groups of the zeolitic layers. The hybrids contain micropores within the inorganic layers and a well-defined mesoporous system in between the organic linkers. An amination post-treatment introduces basic groups in the organic linkers close to the acid sites present in the structural inorganic counterpart. Through this methodology it has been possible to prepare bifunctional acid-base catalysts where the acid sites are of zeolitic nature located in the inorganic building blocks and the basic sites are part of the organic structure. The resultant materials can act as bifunctional catalysts for performing a two-step cascade reaction that involves the catalytic conversion of benzaldehyde dimethylacetal into benzylidene malononitrile.
- Published
- 2010
- Full Text
- View/download PDF
113. Quantum-chemistry calculations of hydrogen adsorption in MOF-5.
- Author
-
Gomez DA, Combariza AF, and Sastre G
- Abstract
High concentrations of molecular hydrogen adsorption on MOF-5 were evaluated at the semiempirical PM6 (periodic and cluster) and ab initio MP2 (cluster) theoretical levels. From the semiempirical calculations, an uptake of 3.9% weight on the inorganic building unit of MOF-5 was estimated, in good agreement with a recent accurate estimation of 4.5-5.2%. Although PM6 allows a correct estimation of the maximum uptake, the adsorption energy was overestimated and hence ab initio calculations, including a correlation treatment at the MP2 level as well as corrections for basis set superposition error, were performed with full optimisation, including the 6-31G basis set, which rendered an adsorption energy (per hydrogen molecule) of -0.14 kcal mol(-1). The crucial role of the quality of the basis set, as well as the importance of simulating high hydrogen loading (resembling experimental measurements), are remarked. Single point calculations (using the 6-31G geometry) with improved basis sets 6-31G(d,p) and 6-31++G(d,p) yielded adsorption energies of -0.33 and -0.57 kcal mol(-1), the latter in reasonable agreement with a recent experimental estimation of -1.0 kcal mol(-1). The role of the intermolecular hydrogen interactions is highlighted in this study, since many previous computational studies were performed at low hydrogen loadings, far from the experimental uptake conditions.
- Published
- 2009
- Full Text
- View/download PDF
114. A zeolitic structure (ITQ-34) with connected 9- and 10-ring channels obtained with phosphonium cations as structure directing agents.
- Author
-
Corma A, Diaz-Cabanas MJ, Jorda JL, Rey F, Sastre G, and Strohmaier KG
- Published
- 2008
- Full Text
- View/download PDF
115. Ammonia IRMS-TPD measurements and DFT calculation on acidic hydroxyl groups in CHA-type zeolites.
- Author
-
Suzuki K, Sastre G, Katada N, and Niwa M
- Subjects
- Models, Molecular, Oxygen chemistry, Temperature, Thermodynamics, Algorithms, Ammonia chemistry, Hydroxyl Radical chemistry, Spectrophotometry, Infrared methods, Zeolites analysis, Zeolites chemistry
- Abstract
Brønsted acidity of H-chabazite (CHA) zeolites (Si : Al(2) = 4.2) was investigated by means of ammonia infrared-mass spectrometry/temperature-programmed desorption (IRMS-TPD) methods and density functional calculations. Four IR bands were observed at 3644, 3616, 3575 and 3538 cm(-1), and they were ascribable to the acidic OH groups on four nonequivalent oxygen sites in the CHA structure. The absorption band at 3538 cm(-1) was attributed to the O(4)H in the 6-membered ring (MR), and ammonia adsorption energy (DeltaU) of this OH group was the lowest among the 4 kinds of OH groups. The other 3 bands were assigned to the acidic OH groups in 8MR. It was observed that the DeltaU in 8 and 6MR were 131 (+/-3) and 101 kJ mol(-1), respectively. On the other hand, the density functional theory (DFT) calculations within periodic boundary conditions yielded the adsorption energies on these OH groups in 8 and 6MR to be ca. 130 and 110 kJ mol(-1), respectively, in good agreement with the experimentally-observed values.
- Published
- 2007
- Full Text
- View/download PDF
116. A computational chemistry insight in the role of structure directing agents in the synthesis of zeolites.
- Author
-
Sastre G
- Subjects
- Chemical Phenomena, Chemistry, Computer Simulation, Thermodynamics, Zeolites chemistry, Aluminum chemistry, Fluorides chemistry, Germanium chemistry, Organic Chemicals chemistry, Silicon chemistry, Zeolites chemical synthesis
- Abstract
The role of structure directing agents in the synthesis of zeolites has been studied through atomistic simulation techniques. Three different kinds of structure directing agents have been reviewed: (i) isomorphic heteroatom Si --> Al and Si --> Ge substitutions; (ii) F(-) anions; and (iii) organic SDAs. The interplay between these structure directing agents is described and the separate effects of each one have been found from energy calculations and analysis of energetic terms.
- Published
- 2007
- Full Text
- View/download PDF
117. Computational study of location and role of fluoride in zeolite structures.
- Author
-
Pulido A, Corma A, and Sastre G
- Abstract
The distribution of fluoride ions has been studied in the pure silica IFR, ITH, IWR, STF and STT zeolite structures using computational techniques. The interactions between the F- and SDA+ ions (where SDA is the organic structure directing agent) are able to explain the F- cage occupation found experimentally. While studying the short-range fluoride-framework interactions, a relationship was found between the Si atoms forming the pentacoordinated units and the lowest F- defect energies, which rationalizes the experimental Si-F bonding in terms of energetic stability. It is proposed that the F- location is governed by a two step process. In a first stage, the electrostatic long-range forces and, especially, the interactions between the F- and the SDA+ ions, decide which cage will be filled with F-; in a second stage, once the F- cage location is decided, the F- forms a covalent bond with a Si site to form an energetically stable pentacoordinated unit [SiO4/2F]-.
- Published
- 2006
- Full Text
- View/download PDF
118. Rings and strain in pure silica zeolites.
- Author
-
Sastre G and Corma A
- Abstract
The stability of rings in pure silica zeolite frameworks is investigated through a new method. The energetic terms influencing the stability of rings are evaluated through the short-range plus electrostatics corresponding to SiO bonds and OSiO and SiOSi angles. Several atomistic force fields have been evaluated, and a reparametrization of the Vessal-Leslie-Catlow force field has been chosen because of its physical meaning and good structural accuracy. The ring energetics are analyzed and discussed in terms of local strain in the framework and in terms of geometric variables. This methodology allows to differentiate between the strain of rings of a given size in different zeolite structures. In particular, it is found that double four rings (D4Rs) are not necessarily, as previously stated, a strained secondary building unit. The analyses of D4Rs in the topologies AST, BEC, and LTA allow the calculation of its stability in the different structures showing high energy in BEC and LTA and low energy in AST. Implications of these results on nucleation of zeolites are drawn regarding the facility with which D4Rs are inserted in different frameworks.
- Published
- 2006
- Full Text
- View/download PDF
119. Computational study of 19F NMR spectra of double four ring-containing Si/Ge-zeolites.
- Author
-
Pulido A, Sastre G, and Corma A
- Abstract
(19)F NMR chemical shifts are calculated in order to study the F(-) environment in double four ring (D4R) containing Si/Ge-zeolites. The calculations with the DFT/CSGT/B3PW91 methodology yielded an agreement within 2 ppm with respect to the experimental peaks corresponding to the D4R units containing 8Si0Ge, 7Si1Ge and 0Si8Ge of the octadecasil zeolite. The optimisation of the 7Si1Ge-, 6Si2Ge-, 5Si3Ge- and 4Si4Ge-D4R units with DFT/B3LYP methodology shows that a covalent Ge-F bond is formed and therefore a Ge atom in the D4R is pentacoordinated. The displacement of the fluoride ion towards a Ge atom in the Ge-containing D4R units locates four Si/Ge atoms in the close vicinity of the F(-) and this makes possible a rationalization of the (19)F NMR signals in groups according to the number of Si (n) and Ge (m) atoms in the nearest F(-) environment, F-Si(n)Ge(m) (where n+m=4). Thus, the calculated chemical shifts show that higher values are observed when the number of Ge atoms in the nearest F(-) environment increases.
- Published
- 2006
- Full Text
- View/download PDF
120. Influence of pore dimension and sorption configuration on the heat of sorption of hexane on monodimensional siliceous zeolites.
- Author
-
Gribov EN, Sastre G, and Corma A
- Abstract
Sorption of n-hexane on monodimensional pure silica SSZ-35, CIT-5, ZSM-12, and ZSM-22 zeolites with different pore dimension and on recently synthesized ITQ-29 was studied by IR spectroscopic and computational chemistry methods. Heats of sorption of n-hexane on these zeolites was determined experimentally from the temperature dependence of the intensity of IR bands of sorbed hexane as well as from theoretical calculations. Calculations have shown the different orientations of sorbed hexane molecules inside zeolite channels, which depend on the type of zeolite and loading. At high loadings, ordering of hexane inside the channels is observed due to optimization of sorbate-sorbate and sorbate-zeolite interaction energies. Such ordering is responsible for the increase of the sorption energy. A decrease of the sorption energy upon increasing the pore dimension of zeolite was observed, in agreement with results previously published in the literature. Effects of pore diameter of zeolites and ordering of molecules inside zeolite channels on the sorption energy of hexane are discussed.
- Published
- 2005
- Full Text
- View/download PDF
121. A multisite molecular mechanism for Baeyer-Villiger oxidations on solid catalysts using environmentally friendly H2O2 as oxidant.
- Author
-
Boronat M, Corma A, Renz M, Sastre G, and Viruela PM
- Abstract
The molecular mechanism of the Baeyer-Villiger oxidation of cyclohexanone with hydrogen peroxide catalyzed by the Sn-beta zeolite has been investigated by combining molecular mechanics, quantum-chemical calculations, spectroscopic, and kinetic techniques. A theoretical study of the location of Sn in zeolite beta was performed by using atomistic force-field techniques to simulate the local environment of the active site. An interatomic potential for Sn/Si zeolites, which allows the simulation of zeolites containing Sn in a tetrahedral environment, has been developed by fitting it to the experimental properties of quartz and SnO2(rutile). The tin active site has been modeled by means of a Sn(OSiH3)3OH cluster, which includes a defect in the framework that provides the flexibility necessary for the interaction between the adsorbates and the Lewis acid center. Two possible reaction pathways have been considered in the computational study, one of them involving the activation of the cyclohexanone carbonyl group by Sn (1) and the other one involving hydrogen peroxide being activated through the formation of a tin-hydroperoxo intermediate (2). Both the quantum-chemical results and the kinetic study indicate that the reaction follows mechanism 1, and that the catalyst active site consists of two centers: the Lewis acid Sn atom to which cyclohexanone has to coordinate, and the oxygen atom of the Sn-OH group that interacts with H2O2 forming a hydrogen bond.
- Published
- 2005
- Full Text
- View/download PDF
122. Pentacoordinated germanium in AST zeolite synthesised in fluoride media. A 19F NMR validated computational study.
- Author
-
Sastre G, Pulido A, and Corma A
- Subjects
- Crystallography, X-Ray, Models, Molecular, Molecular Structure, Organometallic Compounds chemistry, Sensitivity and Specificity, Computer Simulation, Fluorides chemistry, Germanium chemistry, Magnetic Resonance Spectroscopy methods, Organometallic Compounds chemical synthesis, Zeolites chemistry
- Abstract
A computational study shows that Ge is pentacoordinated in the double four rings (D4R) of Si/Ge AST zeolites; the calculated chemical shifts of F-D4R containing 8Si, 7Si1Ge and 8Ge reproduce the trends of 19F NMR experiments.
- Published
- 2005
- Full Text
- View/download PDF
123. Synthesis, characterization, and framework heteroatom localization in ITQ-21.
- Author
-
Blasco T, Corma A, Díaz-Cabañas MJ, Rey F, Rius J, Sastre G, and Vidal-Moya JA
- Abstract
ITQ-21 has been synthesized in a wide range of compositions. By rationally modifying the synthesis variables and zeolite composition, it is possible to fine-tune the crystallite size from nanocrystals (<80 nm) up to microns and to avoid the competition of other phases such as CIT-5, SSZ-24, or a laminar phase that can also be synthesized with the same organic structure directing agent. By means of XRD and (19)F MAS NMR, Ge and Si have been localized among the different crystallographic positions, and it is shown that Ge preferentially occupies T1 positions at the D4R cages, avoiding formation of Ge-O-Ge pairs. However, at high Ge loadings (Si/Ge = 1.7), a new (19)F MAS NMR signal at -14 ppm has been observed and assigned to the presence of Ge-O-Ge in Ge-rich D4R cages. Energetic configurations obtained by theoretical calculations fully agree with experimental observations, with the following increasing order in energy for Ge substitution: T1 < T2 < Ge-O-Ge in T1 < T3.
- Published
- 2004
- Full Text
- View/download PDF
124. Preferential location of Ge atoms in polymorph C of beta zeolite (ITQ-17) and their structure-directing effect: a computational, XRD, and NMR spectroscopic study.
- Author
-
Sastre G, Vidal-Moya JA, Blasco T, Rius J, Jordá JL, Navarro MT, Rey F, and Corma A
- Published
- 2002
- Full Text
- View/download PDF
125. Her-2/neu oncogene expression in Puerto Rican females with breast cancer.
- Author
-
Peredo R, Sastre G, Serrano J, and Hunter Mellado R
- Subjects
- Adenocarcinoma ethnology, Adenocarcinoma genetics, Adenocarcinoma pathology, Adult, Age Factors, Aged, Biomarkers, Tumor analysis, Breast Neoplasms ethnology, Breast Neoplasms genetics, Breast Neoplasms pathology, Cohort Studies, Female, Hispanic or Latino, Humans, Immunohistochemistry, Lymphatic Metastasis, Menopause, Middle Aged, Oncogene Proteins immunology, Ploidies, Proto-Oncogene Mas, Puerto Rico ethnology, Receptor, ErbB-2 immunology, S Phase, Adenocarcinoma metabolism, Breast Neoplasms metabolism, Oncogene Proteins metabolism, Receptor, ErbB-2 metabolism
- Abstract
Her-2/neu belongs to the family of tyrosine kinase transmembrane proteins whose overexpression has been associated with a poor prognosis in patients with breast cancer. The product of this proto-oncogene is overexpressed in 25-30% of human breast cancer and is the target of selective immunotherapy. Concerned about the ethnic differences on the expression of this oncogene, we have evaluated 143 consecutive specimens of primary breast cancer diagnosed in San Pablo Hospital, Puerto Rico. The specimens were analyzed for Her-2/neu expression using immunohistochemistry assays (Hercept test). We have related the expression of hormone receptor status, percent cells in S phase, DNA ploidy, tumor size, nodal status and menopausal state with the Her2/neu expression. Out of 143 specimens, 28 overexpressed the Her-2/neu (19.6%). Of the Her/2 negative 30/114 (26%) were estrogen receptor negative as compared to 9/27 (33%) (p = 0.464). The degree of aneuploidy was abnormal in 25/104 (24%) in the Her-2/neu negative vs 11/27 (41%) p = 0.083. The percent cell in DNA synthesis was high in 16/77 (21%) in Her-2/neu negative vs 4/15 (27%) p = 0.613. The tumor size was greater than 2 cm in 35/106 (33%) in Her-2/neu negative vs 9/23 (39%) p = 0.575. In the progesterone specimens negative for Her2, 44/114 (39%) were Her2/neu negative vs 15/27 (56%) p = 0.108. No differences were seen regarding menopausal status, age and nuclear grading. A trend favoring abnormal aneuploidy in Her2/neu positive was seen. Nodal involvement was significantly associated with Her2/neu overexpression. (p = 0.037). Although the incidence of Her2 overexpression found in this database was somewhat lower than the one reported in the literature, this might also be due to the small cohort examined or to the technique utilized.
- Published
- 2001
126. [Characterization of the resistance to combinations of beta lactams and inhibitors of beta-lactamases in Escherichia coli. Effect of the type and amount of beta-lactamase production].
- Author
-
del Mar Pérez-Moreno M, Pous-Miralles G, Romera-Sastre G, Panisello-Bertomeu JM, Jardí-Baiges AM, and Zarazoga-López J
- Subjects
- Anti-Bacterial Agents administration & dosage, Bacterial Proteins antagonists & inhibitors, Bacterial Proteins biosynthesis, Drug Combinations, Enzyme Inhibitors administration & dosage, Escherichia coli enzymology, Microbial Sensitivity Tests, Species Specificity, beta-Lactamase Inhibitors, beta-Lactamases biosynthesis, beta-Lactamases classification, beta-Lactams, Anti-Bacterial Agents pharmacology, Bacterial Proteins physiology, Enzyme Inhibitors pharmacology, Escherichia coli drug effects, beta-Lactam Resistance, beta-Lactamases physiology
- Abstract
Background: The aim of this study was to characterize resistance of Escherichia coli in our environment to four associations of beta-lactams and beta-lactamase inhibitors (beta Lac) studying the influence of the type and level of beta Lac production., Methods: The minimum inhibitory concentration (MIC) to ampicillin/sulbactam (A/S), amoxycillin/clavulanic acid (A/C), ticarcillin/clavulanic acid (T/C) and piperacillin/tazobactam (P/T) assessed was in 245 strains of E. coli resistant to ampicillin, consecutively isolated in our laboratory from September 1995 to March 1996. The beta Lac produced by these isolates were identified by isoelectrofocusing and spectrophotometrically quantified., Results: The sensitivity to A/S, A/C, T/C and P/T was of 9.4, 86.9, 64.5 and 89.4%, respectively. The strains with only one beta Lac which cofocused with TEM-1 were the most frequent (215/245), followed by those producing a cofocusing enzyme with SHV-1 (7/245). A significant correlation was observed between beta Lact activity of the 215 TEM-1 strains and their MIC at A/S (r = 0.53; p < 0.001), A/C (r = 0.46; p < 0.001), T/TC (r = 0.58; p < 0.001), and P/T (r = 0.42; p < 0.001). The comparison between enzyme activity of the isolates of the different categories of susceptibility showed significant differences (p < 0.05) for the four associations studied., Conclusion: TEM-1 production is the main cause of resistance to beta-lactams in E. coli in our environment. The inhibitory efficacy of sulbactam, clavulanic acid and tazobactam over TEM-1 is inversely proportional to the amounts of enzyme produced. The high rate of resistance to A/S and T/C E. coli presents in our environment is mainly due to a hyperproduction of TEM-1.
- Published
- 1997
127. [Development of intellectual deficiencies during operational learning. Conservation of continuous quantities. Conservation of discrete quantities].
- Author
-
Moreno M and Sastre G
- Subjects
- Child, Female, Humans, Male, Mathematics, Mental Processes, Methods, Intellectual Disability etiology, Intelligence, Learning
- Published
- 1972
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.