E. A. Castro

National Scientific and Technical Research Council, Buenos Aires, Buenos Aires F.D., Argentina

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Publications (189)191.18 Total impact

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    ABSTRACT: In this chapter, the methodology of building up quantitative structure-property/activity relationships (QSPRs/QSARs)-by means of the CORAL software is described. The Monte Carlo method is the basis of this approach. Simplified Molecular Input-Line Entry System (SMILES) is used as the representation of the molecular structure. The conversion of SMILES into the molecular graph is available for QSPR/ QSAR analysis using the CORAL software. The model for an endpoint is a mathematical function of the correlation weights for various features of the molecular structure. Hybrid models that are based on features extracted from both SMILES and a graph also can be built up by the CORAL software. The conceptually new ideas collected and revealed through the CORAL software are: (1) any QSPR/QSAR model is a random event; and (2) optimal descriptor can be a translator of eclectic information into an endpoint prediction.
    Full-text · Article · Jan 2015
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    ABSTRACT: This communication describes a novel structural-type that could be the basis for a potentially new allotrope of C. The novel structural-type is called “exocyclobutadieneite”, and it is thus named for the 1,3-dimethylenecyclobutane generating fragment that the lattice is based upon. It is a 3-,4-connected network consisting of slightly distorted tetrahedral vertices, and slightly distorted pairs of trigonal planar vertices. The lattice can be derived from a known mineral structure called Cooperite (PtS or PdO) by a topologically isomorphic substitution of trigonal planar atom pairs, for square planar vertexes, in the parent Cooperite unit cell. As such, the new pattern bears a distinct counterpoint relationship with its sibling structural-type called the glitter lattice, which has already been described by the authors in several other papers. And whereas glitter is generated by a topologically isomorphic substitution of trigonal planar atom pairs for the square planar vertices in the Cooperite unit cell, in a fashion that extends the unit cell vertically along the crystallographic c-axis, the exocyclobutadieneite structure is generated, in counterpoint, by such an isomorphic substitution that extends the unit cell horizontally along the a- and b-axes. Both the resulting glitter and exocyclobutadieneite structural-types possess AB $_{2}$ stoichiometry (where A is a tetrahedral vertex and B is a trigonal planar vertex) and both occur in the tetragonal symmetry space group P4 $_{2}$ /mmc (#131). The networks differ, however, in the special positions adopted by the vertices in the resultant unit cells, and in their respective topology, as is evidenced by consideration of the Wells point symbols and Schläfli symbols for the 2 tetragonal networks. These differences are illustrated further in the course of the discussion to follow.
    No preview · Article · Mar 2013 · Journal of Mathematical Chemistry
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    ABSTRACT: A quantitative structure activity relationship analysis was applied to a library of 51 benzylacetamide derivatives with anticonvulsant activity. The molecular structures of 51 compounds were optimized with the Semiempirical Method PM6 (Parametric Method-6) included in the MOPAC2009 software. The optimized structures of all the examined compounds were represented by 1497 DRAGON-type descriptors. Using multiple linear regression (MLR), the influence of constitutional, topological, electronic, physicochemical and quantum molecular descriptors on the activity was investigated. The validation of models were performed through the leave-one-out cross technique in conjunction with external validation. From different types of molecular descriptors, six new QSAR models were developed. The models using 0D descriptors (constitutional descriptors) and quantum descriptors do not have high statistical quality. The combination of 2D and 3D descriptors produce a model of high predictive quality (Rcal= 0.888; Scal= 0.195; Rval= 0.814; Sval=0.431; Rloo=0.867; Sloo=0.212). Results show the important role of electronic and topologic features of molecules on their anticonvulsant activity in relative to constitutional parameters.
    No preview · Article · Jan 2012 · MATCH Communications in Mathematical and in Computer Chemistry
  • M.J. Bucknum · E.A. Castro
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    ABSTRACT: This section has described the structure of a hypothetical 3-,4-connected net termed glitter. This is a model of an allotrope of carbon in the form of a synthetic metal. That paper pointed to the importance of through-space pσ interactions of adjacent olefin units in the net in understanding the electronic structure at the Fermi level. The present communication elucidates the role of spiroconjugation in understanding features of the electronic band structure and density of states of glitter. With this analysis of spiroconjugation in the 1-dimensional polyspiroquinoid polymer and the 3-dimensional glitter lattice, the foundations have been laid for a new type of quantum chemistry herein called spiro quantum chemistry. Spiro quantum chemistry complements traditional quantum chemistry which is focused on linear polyenes, circular annulenes, polyhexes, 2- dimensional graphene sheets and related structures including fullerenes, by focusing on spiroconjugated hydrocarbon structures in 1- ,2- and 3-D, including linear spiro[n]quinoids and polyspiroquinoid in 1D, circular cyclospiro[n]quinoids, spiro[m,n]graphene fragments and spirographene in 2D and [m,n,o]glitter fragments and glitter in 3D.
    No preview · Article · Jan 2012
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    Ethel N. Coscarello · Ruth Hojvat · Dora A. Barbiric · Eduardo A. Castro

    Preview · Chapter · Jan 2011
  • P.R. Duchowicz · E.A. Castro
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    ABSTRACT: Present chapter reviews the application of Quantitative Structure-Activity Relationships for the treatment of molecules involving thousands of atoms, such as proteins, nucleic acids (DNA, RNA), or polysaccharides. This is a new developing area of interest in Chemoinformatics, and it is expected to have a growing number of applications during the forthcoming years. Among the several points to be addressed during the modeling of macromolecules, the most important one appears to be the accurate representation of the chemical structure through numerical descriptors. It has to be noticed that descriptors based on optimized three-dimensional geometry are difficult to specify, and it is also a drawback the fact that the experimental geometry is not available. However, different experts in the field have been generalizing the employment of classical types of topological descriptors in macromolecular systems.
    No preview · Article · Jan 2011
  • P.R. Duchowicz · E.A. Castro
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    ABSTRACT: The Fuzzy Logic Theory has been considered a brilliant and potent revolutionary computer technology that has received broad attention during the last decades, widely employed in the fields of Physics, Mathematics and Chemistry, particularly for the classification and systematization of information with applications in Theoretical Computer Science and Artificial Intelligence. The main reason for this is that Fuzzy Logic is a system of concepts, principles and methods for approximate ways of reasoning which are expressed in natural language. This chapter reviews the application of Fuzzy Logic Theory to the field of the Quantitative Structure Property-Activity Relationships Theory, describing the studies developed by different experts in this fascinating field.
    No preview · Article · Jan 2011
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    ABSTRACT: The thermal decomposition study of 3,3,6,6-tetramethyl-1,2,4,5-tetroxane (acetone cyclic diperoxide) was carried out in 2-methoxyethanol solution in the 130-166 °C temperature range. The overall reaction follows a first-order kinetic law up to at least 75% diperoxide conversion. The activation parameters (ΔH# = 22.5 ± 0.7 kcal⋅mol–1 and ΔS# = -25.6 ± 0.5 cal⋅mol–1⋅K–1) for the unimolecular rupture of the O–O bond in the diperoxide molecule were obtained by measuring the remnant diperoxide at different reaction times by the CG technique. Acetone was detected by GC as the major organic product of the reaction. Keywordsacetone cyclic diperoxide-diacetone diperoxide-tetroxane-thermolysis
    No preview · Article · Dec 2010 · Chemistry of Heterocyclic Compounds
  • M. B. LOPEZ · G. L. ESTIU · E. A. CASTRO · A. J. ARVIA
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    No preview · Article · Feb 2010 · ChemInform
  • M. B. LOPEZ · G. L. ESTIU · E. A. CASTRO · A. J. ARVIA
    [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    No preview · Article · Feb 2010 · ChemInform
  • M.J. Bucknum · E.A. Castro

    No preview · Article · Feb 2010
  • M.J. Bucknum · E.A. Castro
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    ABSTRACT: Calcite lattice parameters have been measured at simultaneous pressure andtemperature using a newly designed hydrothermal diamond anvil cell capable of 1200°Cand 25 kbar. Real-time energy dispersive diffraction patterns were obtained from agasketed sample of powdered calcite immersed in water using white synchrotronradiation. A path of constant density was followed in the PT-plane of water as the samplechamber volume remained constant. Temperature was directly measured from chromelalumelthermocouples cemented to the upper and lower diamond anvils, and the pressurewas calculated from the equation of state of water using the temperature (115 ± 3°C) atwhich the vapour phase disappeared to mark the isochore (0.950 ± 0.005 gm/cm3)followed. Least squares regression of eight calcite reflections from a room pressuretempeaturepattern obtained at the Cornell High Energy Synchrotron Source (CHESS)yielded ao = 4.988 ± 0.001 Å and co = 17.088 ± 0.001 Å.A high temperature diffractometer on a conventional source was used to measurelattice parameters of the calcite to 524°C. From a linear least squares fit to these data, thethermal anisotropy previously reported for calcite was confirmed as a/ao changed by -3.63x10-6/°C, while in contrast changed by +3.26x10-5/°C. At CHESS, diffraction datawere collected in the PT-plane from calcite immersed in water, and each pattern was leastsquares refined for the calcite lattice parameters. Along the 0.950 gm/cm3 isochore ofwater, the thermal anisotropy in the calcite lattice parameters changed slightly with theapplication of water pressure. From a linear fit on the calcite data obtained at CHESS,a/ao changed by -5.196x10-6/°C and c/co changed by +2.872x10-5/°C along the 0.950gm/cm3 isochore of water. Because the expansion of the c-lattice parameter of calcite is nearly an order of magnitude greater than the contraction of the a-lattice parameter, theunit cell volume of calcite expands along the temperature axis and along this waterisochore to 7.62 kbar water pressure at 533°C.
    No preview · Article · Jan 2010

  • No preview · Article · Dec 2009
  • EC Ibezim · PR Duchowicz · NE Ibezim · EA Castro
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    ABSTRACT: QSPR constitutes one of the major areas within computational chemistry and refers to the process of correlating chemical structure of compounds with their physicochemical properties. To achieve this, it employs a wide range of computational programmes and computer softwares including DRAGON, MATLAB, HYPERCHEM and RECKON. Experimental data are first generated from which models or equations are derived that now help to predict the properties of known or unknown compounds whose properties are hitherto unknown. It is a very useful tool in the search for new compounds with improved physicochemical properties like melting point, boiling point, free energy, activation energy, partition coefficient,diffusion coefficient and the like.
    No preview · Article · Dec 2009
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    ABSTRACT: Molecular modeling has proved an indispensible tool in exact science research utilizing tested computational theories. One important area of application of molecular modeling is in the physics discipline. It has been used extensively in understudying some physics based principles which have often proved difficult to unravel by laboratory experimental studies. Use is made of theories and models like density functional theory, molecular mechanics method, Thomas Fermi model and molecular dynamics. Several computer softwares have been employed in physics-based modeling and include: Ascalaph, BOSS, CHARMM, COSMOS, Ghemical, GROMOS, GROMACS, MDynaMix, NAMD, STR3DI32, TINKER, Zodiac, X-PLOR.
    No preview · Article · Dec 2009
  • M. J. Bucknum · E. A. Castro
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    ABSTRACT: A novel 4,6-connected network, called Hsichengia, is described. The novel network lies in the trigonal space group P3m1 (no. 156), with a = b = 3.447 Å and c = 12.948 Å; these lattice parameters were derived assuming Fe-S composition. It implies a binary AB2 stoichiometry in which the 6-connected A (Fe) atoms have octahedral configuration, and the 4-connected B (S) atoms have tetrahedral configuration. The Hsichengia network seems to be very closely related to the layered MoS2 structure-type, in which puckered MoS2 layers composed of octahedral Mo centers and trigonal-pyramidal S centers are held together by weak van der Waals forces normal to the a and b directions where the MoS2 layers extend. Thus the Hsichengia network can be generated from the MoS2 lattice by the formation of disulfide (S-S) bridges between particular layers, thereby creating a 3-dimensional network from a 2-dimensional layered structure, so that the S atoms are transformed from 3-connected trigonal-pyramidal coordination into fully 4-connected tetrahedral coordination. The Wells point symbol for the Hsichengia network is given by (4666)(4363)2, and it is thus seen to have the translated Schläfli symbol given as (5, 42/3). The latter is identical to that intrinsic to the well-known mineral structure of the pyrite network, FeS2, with the corresponding Wells point symbol (512)(56)2. Therefore, the Hsichengia network may be regarded as a topological isomer of the pyrite network, where topological isomerism is defined as occurring between unique networks possessing the same Schläfli symbol. Phase transformation between the two topological isomers is possible.
    No preview · Article · Nov 2009 · Russian Journal of General Chemistry
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    María López · Eduardo Castro
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    ABSTRACT: DFT study on the the stability and reactivity of Pt(100) and Pt(111) surfaces modified by nickel UPD monolayer deposition have been carried out. We used the binding energy calculation of bimetallic structures versus the cohesion energy of the bulk adsorbate to quantify the underpotential shift (ΔEupd) to determine the stability of the bimetallic systems. The reactivity of the clean and modified surface was analized by energy levels of the highest occupied molecular orbital (HOMO), softness and local softness. We concluded that the stability of Pt(100)25Ni9 and Pt(111)25Ni10 bimetallic structures cannot be explained by excess of the metal- substrate binding energy but the instability can be explained by structural effects. We found that the modified surfaces are more reactive and the active sites are located in the centre of the cluster which favores the formation of islands of atoms onto these surfaces.
    Preview · Article · Oct 2009 · Nature Precedings
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    ABSTRACT: Thermal decomposition of formaldehyde diperoxide (1,2,4,5-tetraoxane) in aqueous solution with an initial concentration of 6.22 × 10−3 M was studied in the temperatures range from 403 to 439 K. The reaction was found to follow first-order kinetic law, and formaldehyde was the major decomposition product. The activation parameters of the initial step of the reaction (ΔH ≠ = 15.25 ± 0.5 kcal mol−1, ΔS ≠ = −47.78 ± 0.4 cal mol−1K−1, E a = 16.09 ± 0.5 kcal mol−1) support a mechanism involving homolytic rupture of one peroxide bond in the 1,2,4,5-tetraoxane molecule with participation of the solvent and formation of a diradical intermediate.
    No preview · Article · Oct 2009 · Russian Journal of General Chemistry
  • N. B. Okulik · A. H. Jubert · E. A. Castro
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    No preview · Article · Sep 2009 · ChemInform
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    ABSTRACT: The complexation by β-cyclodextrin (β-CD) of three organophosphorus pesticides, fenitrothion, parathion and methylparathion, and of their carboxylic ester analogues was analyzed using PM3 and molecular mechanics methods. The objective was to elucidate structural features and energy changes that accompany the complexation and could possibly affect the hydrolysis process, which is catalyzed by β-CD in the case of carboxylic esters but inhibited for the pesticides, in alkaline medium. The complexation of fenitrothion was further explored, since experiments proved its hydrolysis is relatively less inhibited and progresses mainly through a different pathway than that usually accepted. The results of this study show that complex structures involving esters enable effective interactions between the guest carbonyl and the rim of the host; methylparathion and parathion, however, appear to be deeply included in the cavity of β-CD. Therefore the conditions for a nucleophilic attack by the β-CD are favorable for the carboxylic esters but not for the two pesticides. Different complex geometries resulted for fenitrothion depending on its mode of inclusion in the cavity, none apparently being prone to an attack by the β-CD, but favoring instead the approach of an external OH− group, in agreement with the experiment.
    No preview · Article · Aug 2009 · Journal of Structural Chemistry

Publication Stats

1k Citations
191.18 Total Impact Points

Institutions

  • 2013
    • National Scientific and Technical Research Council
      Buenos Aires, Buenos Aires F.D., Argentina
  • 1981-2011
    • National University of La Plata
      • • Facultad de Ciencias Exactas
      • • Departamento de Química
      • • Instituto de Investigaciones Físicoquímicas Teóricas y Aplicadas (INIFTA)
      Eva Perón, Buenos Aires, Argentina
  • 2006-2009
    • University of Buenos Aires
      Buenos Aires, Buenos Aires F.D., Argentina
  • 2008
    • IVI Buenos Aires
      Buenos Aires, Buenos Aires F.D., Argentina
  • 2005-2006
    • Georgia College and State University
      • Department of Chemistry, Physics and Astronomy
      MLJ, Georgia, United States
    • Universidad de la Cuenca del Plata
      Eva Perón, Buenos Aires, Argentina
  • 2001-2004
    • National University of the Northeast
      • Faculty of Natural and Exact Sciences and Surveying
      Corrientes, Corrientes, Argentina
  • 1998
    • Universidad Nacional de Mar del Plata
      • Departamento de Química
      Mar de Plata, Buenos Aires, Argentina