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Fernández FM. Comment on: ‘A doubly anharmonic oscillator in an induced electric dipole system’. Proc Math Phys Eng Sci 2022. [DOI: 10.1098/rspa.2021.0645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We argue that recent conclusions about a doubly anharmonic oscillator appear to be wrong. The radial eigenvalue equation is conditionally solvable and the authors derived some analytical eigenvalues for states with polynomial solutions. The allowed discrete values of the cyclotron frequency or intensity of the uniform magnetic field are an artefact of the approach used to obtain such particular solutions. There are bound states when the angular velocity of the rotating reference frame is null, contrary to what the authors claimed.
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Affiliation(s)
- Francisco M. Fernández
- División Química Teórica Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas Diagonal 113 y 64 S/N 1900 La Plata Argentina
| | - Javier Garcia
- División Química Teórica Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA) Diagonal 113 y 64 S/N 1900 La Plata Argentina
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Soper-Hopper MT, Vandegrift J, Baker ES, Fernández FM. Metabolite collision cross section prediction without energy-minimized structures. Analyst 2020; 145:5414-5418. [PMID: 32583823 DOI: 10.1039/d0an00198h] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Matching experimental ion mobility-mass spectrometry data to computationally-generated collision cross section (CCS) values enables more confident metabolite identifications. Here, we show for the first time that accurately predicting CCS values with simple models for the largest library of metabolite cross sections is indeed possible, achieving a root mean square error of 7.0 Å2 (median error of ∼2%) using linear methods accesible to most researchers. A comparison on the performance of 2D vs. 3D molecular descriptors for the purposes of CCS prediction is also presented for the first time, enabling CCS prediction without a priori knowledge of the metabolite's energy-minimized structure.
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Affiliation(s)
- M T Soper-Hopper
- Northern Kentucky University, Department of Chemistry and Biochemistry, 1 Nunn Drive, Highland Heights, KY 41099, USA
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Amore P, Fernández FM. Mathematical analysis of recent analytical approximations to the collapse of an empty spherical bubble. J Chem Phys 2013; 138:084511. [DOI: 10.1063/1.4793217] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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García J, Duchowicz PR, Rozas MF, Caram JA, Mirífico MV, Fernández FM, Castro EA. A comparative QSAR on 1,2,5-thiadiazolidin-3-one 1,1-dioxide compounds as selective inhibitors of human serine proteinases. J Mol Graph Model 2011; 31:10-9. [PMID: 21908217 DOI: 10.1016/j.jmgm.2011.07.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 07/28/2011] [Accepted: 07/31/2011] [Indexed: 11/30/2022]
Abstract
Selective inhibitors of target serine proteinases have a potential therapeutic role for the treatment of various inflammatory and related diseases. We develop a comparative quantitative structure-activity relationships based analysis on compounds embodying the 1,2,5-thiadiazolidin-3-one 1,1-dioxide scaffold. By means of classical Molecular Dynamics we obtain the conformation of each lowest-energy molecular structure from which we derive more than a thousand of structural descriptors necessary for building predictive QSAR models. We resort to two different modeling approaches with the purpose of testing the consistency of our results: (a) multivariable linear regressions based on the replacement method and forward stepwise regression, and (b) the calculation of flexible descriptors with the CORAL program. All the models are properly validated by means of standard procedures. The resulting QSAR models are supposed to be of great utility for the rational search and design (including synthesis and/or in vitro biochemical studies) of new effective non-peptidyl inhibitors of serine proteinases.
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Affiliation(s)
- Javier García
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, CCT La Plata-CONICET), Casilla de Correo 16, La Plata, Argentina
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Mercader AG, Duchowicz PR, Fernández FM, Castro EA. Advances in the Replacement and Enhanced Replacement Method in QSAR and QSPR Theories. J Chem Inf Model 2011; 51:1575-81. [DOI: 10.1021/ci200079b] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Andrew G. Mercader
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, UNLP, CCT La Plata-CONICET), Diag. 113 y 64, Sucursal 4, C.C. 16, 1900 La Plata, Argentina
- PRALIB (UBA-CONICET), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina
| | - Pablo R. Duchowicz
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, UNLP, CCT La Plata-CONICET), Diag. 113 y 64, Sucursal 4, C.C. 16, 1900 La Plata, Argentina
| | - Francisco M. Fernández
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, UNLP, CCT La Plata-CONICET), Diag. 113 y 64, Sucursal 4, C.C. 16, 1900 La Plata, Argentina
| | - Eduardo A. Castro
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, UNLP, CCT La Plata-CONICET), Diag. 113 y 64, Sucursal 4, C.C. 16, 1900 La Plata, Argentina
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Mercader AG, Goodarzi M, Duchowicz PR, Fernández FM, Castro EA. Predictive QSPR Study of the Dissociation Constants of Diverse Pharmaceutical Compounds. Chem Biol Drug Des 2010; 76:433-40. [DOI: 10.1111/j.1747-0285.2010.01033.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Mercader AG, Duchowicz PR, Fernández FM, Castro EA. Replacement Method and Enhanced Replacement Method Versus the Genetic Algorithm Approach for the Selection of Molecular Descriptors in QSPR/QSAR Theories. J Chem Inf Model 2010; 50:1542-8. [DOI: 10.1021/ci100103r] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Andrew G. Mercader
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, UNLP, CCT La Plata-CONICET), Diag. 113 y 64, Sucursal 4, C.C. 16, 1900 La Plata, Argentina, and PRALIB (UBA-CONICET), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina
| | - Pablo R. Duchowicz
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, UNLP, CCT La Plata-CONICET), Diag. 113 y 64, Sucursal 4, C.C. 16, 1900 La Plata, Argentina, and PRALIB (UBA-CONICET), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina
| | - Francisco M. Fernández
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, UNLP, CCT La Plata-CONICET), Diag. 113 y 64, Sucursal 4, C.C. 16, 1900 La Plata, Argentina, and PRALIB (UBA-CONICET), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina
| | - Eduardo A. Castro
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, UNLP, CCT La Plata-CONICET), Diag. 113 y 64, Sucursal 4, C.C. 16, 1900 La Plata, Argentina, and PRALIB (UBA-CONICET), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina
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Abstract
It was recently found that the lowest-energy collective normal modes dominate the evolutionary divergence of protein structures. This was attributed to a presumed functional importance of such motions, i.e., to natural selection. In contrast to this selectionist explanation, we proposed that the observed behavior could be just the expected physical response of proteins to random mutations. This proposal was based on the success of a linearly forced elastic network model (LFENM) of mutational effects on structure to account for the observed pattern of structural divergence. Here, to further test the mutational explanation and the LFENM, we analyze the structural differences observed not only in homologous (globin-like) proteins but also in unselected experimentally engineered myoglobin mutants and in wild-type variants subject to other perturbations such as ligand-binding and pH changes. We show that the lowest normal modes dominate structural change in all the cases considered and that the LFENM reproduces this behavior quantitatively. The collective nature of the lowest normal modes results in global conformational changes that depend little on the exact nature or location of the perturbation. Significantly, the evolutionarily conserved structural core matches the regions observed to be more robust with respect to mutations, so that the core would be more conserved even under unselected random mutations. In a word, the observed patterns of structural variation can be seen as the natural response of proteins to perturbations and can be adequately modeled using the LFENM, which serves as a common framework to relate a priori different phenomena.
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Affiliation(s)
- Julián Echave
- Instituto Nacional de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Consejo Nacional de Investigación Científica y Técnicas & Universidad Nacional de La Plata, La Plata, Argentina.
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Mercader AG, Duchowicz PR, Fernández FM, Castro EA, Cabrerizo FM, Thomas AH. Predictive modeling of the total deactivation rate constant of singlet oxygen by heterocyclic compounds. J Mol Graph Model 2009; 28:12-9. [DOI: 10.1016/j.jmgm.2009.03.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 03/04/2009] [Accepted: 03/07/2009] [Indexed: 11/29/2022]
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Goodarzi M, Duchowicz PR, Wu CH, Fernández FM, Castro EA. New Hybrid Genetic Based Support Vector Regression as QSAR Approach for Analyzing Flavonoids-GABA(A) Complexes. J Chem Inf Model 2009; 49:1475-85. [DOI: 10.1021/ci900075f] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mohammad Goodarzi
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas INIFTA (UNLP, CCT La Plata-CONICET), Diag. 113 y 64, C.C. 16, Suc.4, 1900 La Plata, Argentina,
- Department of Digital Content and Technology, National Taichung University No. 140, Ming-Shen Road, 40306 Taichung, Taiwan
| | - Pablo R. Duchowicz
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas INIFTA (UNLP, CCT La Plata-CONICET), Diag. 113 y 64, C.C. 16, Suc.4, 1900 La Plata, Argentina,
- Department of Digital Content and Technology, National Taichung University No. 140, Ming-Shen Road, 40306 Taichung, Taiwan
| | - Chih H. Wu
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas INIFTA (UNLP, CCT La Plata-CONICET), Diag. 113 y 64, C.C. 16, Suc.4, 1900 La Plata, Argentina,
- Department of Digital Content and Technology, National Taichung University No. 140, Ming-Shen Road, 40306 Taichung, Taiwan
| | - Francisco M. Fernández
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas INIFTA (UNLP, CCT La Plata-CONICET), Diag. 113 y 64, C.C. 16, Suc.4, 1900 La Plata, Argentina,
- Department of Digital Content and Technology, National Taichung University No. 140, Ming-Shen Road, 40306 Taichung, Taiwan
| | - Eduardo A. Castro
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas INIFTA (UNLP, CCT La Plata-CONICET), Diag. 113 y 64, C.C. 16, Suc.4, 1900 La Plata, Argentina,
- Department of Digital Content and Technology, National Taichung University No. 140, Ming-Shen Road, 40306 Taichung, Taiwan
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Mercader AG, Duchowicz PR, Fernández FM, Castro EA, Wolcan E. QSPR study of solvent quenching of the 5D0→7F2 emission of Eu(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate)3. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.08.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Mercader AG, Duchowicz PR, Fernández FM, Castro EA, Bennardi DO, Autino JC, Romanelli GP. QSAR prediction of inhibition of aldose reductase for flavonoids. Bioorg Med Chem 2008; 16:7470-6. [PMID: 18585047 DOI: 10.1016/j.bmc.2008.06.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Revised: 06/02/2008] [Accepted: 06/04/2008] [Indexed: 11/25/2022]
Abstract
We performed a predictive analysis based on quantitative structure-activity relationships (QSAR) of an important property of flavonoids, which is the inhibition (IC(50)) of aldose reductase (AR). The importance of AR inhibition is that it prevents cataract formation in diabetic patients. The best linear model constructed from 55 molecular structures incorporated six molecular descriptors, selected from more than a thousand geometrical, topological, quantum-mechanical, and electronic types of descriptors. As a practical application, we used the obtained QSAR model to predict the AR inhibitory effect of newly synthesized flavonoids that present 2-, 7-substitutions in the benzopyrane backbone.
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Affiliation(s)
- Andrew G Mercader
- INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Diag. 113 y 64, Sucursal 4, C.C. 16, 1900 La Plata, Argentina.
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Diez RP, Duchowicz PR, Castañeta H, Castro EA, Fernández FM, Albesa AG. A theoretical study of a family of new quinoxaline derivatives. J Mol Graph Model 2006; 25:487-94. [PMID: 16682241 DOI: 10.1016/j.jmgm.2006.03.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Revised: 03/12/2006] [Accepted: 03/13/2006] [Indexed: 10/24/2022]
Abstract
Hybrid density functional calculations are performed on a series of 21 new quinoxaline derivatives, which would likely exhibit important biological activities. Optimized geometries, harmonic vibrational frequencies, and (1)H chemical shifts are reported and compared with experimental data when available. In addition, melting points of 75 derivatives are predicted resorting to the Quantitative Structure-Property Relationship (QSPR) Theory, doing the variable selection by means of the Replacement Method and using 875 theoretical descriptors obtained from Dragon 5 software. The best relationship found has seven descriptors with R=0.8818 and R(l-10%-o)=0.7705.
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Affiliation(s)
- Reinaldo Pis Diez
- CEQUINOR, Centro de Química Inorgánica (CONICET, UNLP), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 962, 1900 La Plata, Argentina
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Craig MI, Barrandeguy ME, Fernández FM. [Equine herpesvirus 2: A study on the relation between viral excretion and respiratory disease in thoroughbred horses]. Rev Argent Microbiol 2006; 38:216-8. [PMID: 17370575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023] Open
Abstract
Equine herpesvirus 2 (EHV-2) was isolated from healthy animals; therefore, the association between EHV-2 infection and respiratory disease raises the question of the role of this agent in this pathology. To date, there are no reports that relate viral excretion to health, this study then analysed 153 nasal swabs from horses in different age groups (older and younger than 1 year old) and state of health (clinically healthy and with respiratory symptoms). Results showed that the percentage of horses with viral excretion was higher within the clinically healthy group, being significative (p < 0.05) in the younger than 1 year old group, whereas the percentage of animals with respiratory symptoms did not show significant differences (p > 0.05) between age groups.
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Affiliation(s)
- M I Craig
- Instituto de Virología, Centro de Investigación en Ciencias Veterinarias y Agronómicas-INTA, CC25 (1712) Castelar, Pcia. de Buenos Aires, Argentina.
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Duchowicz PR, Fernández M, Caballero J, Castro EA, Fernández FM. QSAR for non-nucleoside inhibitors of HIV-1 reverse transcriptase. Bioorg Med Chem 2006; 14:5876-89. [PMID: 16766190 DOI: 10.1016/j.bmc.2006.05.027] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2006] [Revised: 05/06/2006] [Accepted: 05/15/2006] [Indexed: 10/24/2022]
Abstract
By means of QSAR algorithms we model the potency pIC(90) [mM] of 154 non-nucleoside reverse transcriptase inhibitors (NNRTI) of the wild-type HIV-1 virus, considered as the second generation analogues of Efavirenz. In addition, 56 inhibitors of the K-103N viral mutant form are also investigated. A pool of 1494 theoretical molecular descriptors provided mainly by the Dragon 5 software is explored by several methods of variable selection: forward stepwise regression, the replacement method, and the genetic algorithm approach. The optimal models found include up to seven parameters: R = 0.7991, R(l-20%-o) = 0.7233 for the case of wild-type, and R = 0.9261, R(l-5%-o) = 0.8802 for the K-103N mutation.
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Affiliation(s)
- Pablo R Duchowicz
- INIFTA, División Química Teórica, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Diag. 113 y 64, Suc. 4 C. C. 16, (1900) La Plata, Argentina.
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Muse JO, Carducci CN, Stripeikis JD, Tudino MB, Fernández FM. A link between lead and cadmium kinetic speciation in seawater and accumulation by the green alga Ulva lactuca. Environ Pollut 2006; 141:126-30. [PMID: 16289726 DOI: 10.1016/j.envpol.2005.08.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2005] [Accepted: 08/02/2005] [Indexed: 05/05/2023]
Abstract
In this work, studies on the bioaccumulation of Cd and Pb by Ulva lactuca at different sites of Gulf San Jorge (Patagonia, Argentina) are presented. Higher values of bioaccumulated Cd were found in Punta Maqueda - a site believed to serve as a control - in comparison to those in Punta Borja, a place highly exposed to urban and industrial activities. Consequently; the labile fractions of Cd and Pb in seawater were determined with a flow injection-preconcentration manifold interfaced to a graphite furnace-atomic absorption spectrometer (FI-GFAAS). The results obtained by kinetic speciation showed that the variable that correctly explains heavy metals accumulation in the alga, is the labile metal fraction in seawater. We propose to use an enhancement ratio - on the basis of the kinetically labile metal fraction - for calculation of the metal accumulated by the alga relative to its environment.
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Affiliation(s)
- J O Muse
- Departamento de Química Analítica y Fisicoquímica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Qulmica Analitica, 3er. Piso, Junin 956-1113, Buenos Aires, Argentina.
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Duchowicz PR, Castro EA, Fernández FM, Gonzalez MP. A new search algorithm for QSPR/QSAR theories: Normal boiling points of some organic molecules. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2005.07.016] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Amore P, Aranda A, Sáenz R, Fernández FM. Systematic perturbation calculation of integrals with applications to physics. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 71:016704. [PMID: 15697761 DOI: 10.1103/physreve.71.016704] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2004] [Indexed: 05/24/2023]
Abstract
In this paper we generalize and improve a method for calculating the period of a classical oscillator and other integrals of physical interest, which was recently developed by some of the authors. We derive analytical expressions that prove to be more accurate than those commonly found in the literature, and test the convergence of the series produced by the approach.
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Affiliation(s)
- Paolo Amore
- Facultad de Ciencias, Universidad de Colima, Bernal Díaz del Castillo 340, Colima, Colima, Mexico.
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Fernández FM, Vadillo JM, Engelke F, Kimmel JR, Zare RN, Rodriguez N, Wetterhall M, Markides K. Effect of sequence length, sequence frequency, and data acquisition rate on the performance of a Hadamard transform time-of-flight mass spectrometer. J Am Soc Mass Spectrom 2001; 12:1302-1311. [PMID: 11766757 DOI: 10.1016/s1044-0305(01)00322-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Various factors influencing the performance of a Hadamard transform time-of-flight mass spectrometer (HT-TOFMS) have been investigated. Using a nitrogen corona discharge to produce an ion stream of N2+, N3+, and N4+, it is found for spectra containing only N4+ that the signal-to-noise ratio (SNR) closely approaches the value calculated from the ion background by assuming that the ion background follows a Poisson distribution. In contrast, for a more intense beam containing N2+, N3+, and N4+, the SNR is less than its theoretical value because of the appearance of discrete spikes in the mass spectrum caused by deviations in the actual modulation sequence from the ideal one. These spikes can be reduced, however, by decreasing the modulation voltage. Under these optimized conditions, the pseudo-random sequence length is varied to understand how it alters SNR, mass resolution, and scan speed. When the length of the pseudo-random sequence is doubled, the SNR increases by the square root of 2 while the time necessary to record a mass spectrum also doubles. Mass resolution can be varied between 500 and 1200 at m/z = 609 as the sequence length, modulation speed (10 MHz, 25 MHz), and acquisition rate (up to 50 MHz) are changed. Scan speeds of 6000 passes per s can be obtained using a sequence containing 4095 elements modulated at 25 MHz. The capability to tailor the HT-TOFMS to increase the scan speed and resolution with a constant 50% duty cycle makes the technique extremely appealing as a mass analyzer for measuring rapid changes in the composition of an ion stream.
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Affiliation(s)
- F M Fernández
- Department of Chemistry, Stanford University, California 94305-5080, USA
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Pérez Filgueira DM, Wigdorovitz A, Zamorano PI, Ostermann W, Fernández FM, Romera A, Borca MV, Sadir AM. Effect of Mycobacterium sp. wall and Avridine on the antibody response, IgG isotype profile and proliferative response induced by foot and mouth disease virus (FMDV) vaccination in cattle. Vaccine 1999; 17:345-52. [PMID: 9987173 DOI: 10.1016/s0264-410x(98)00204-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Different immunomodulators have been previously tested in our laboratory as enhancers of the specific immune response to FMDV vaccines in a murine model [2-4]. Here, we present results of two of these immunomodulators, a water-soluble fraction of the cell wall of Mycobacterium sp. (WSF) and a synthetic lipoamide, Avridine (AV), which were tested in bovines included in FMDV oil vaccines. Two different concentrations of inactivated viral antigen were employed and the effect of different concentrations of the adjuvants were studied when added to the lower viral dose. It is shown that the inclusion of these adjuvants in the higher concentration in vaccines formulated with low antigen concentration induced the same antibody levels as those induced by vaccines containing twice the concentration of virus, and no adjuvants, and as a commercial formulation which performed with 100% of protection in the potency test. The IgG isotypes profiles induced in these experimental vaccines differed from those elicited by the commercial and control vaccines. Both IgG1 and IgG2 were augmented by the experimental formulations. These adjuvants, specially the WSF, also enhanced the cellular immune response against the FMDV in antigen driven proliferation assays, thus acting on a broad range of immune mechanisms.
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Affiliation(s)
- D M Pérez Filgueira
- Instituto de Virología, Centro de Investigaciones en Ciencias Veterinarias, Buenos Aires, Argentina
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Blasco F, Medina-Hernández MJ, Sagrado S, Fernández FM. Simultaneous spectrophotometric determination of calcium and magnesium in mineral waters by means of multivariate partial least-squares regression. Analyst 1997; 122:639-43. [PMID: 9330035 DOI: 10.1039/a608244k] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A method for simultaneous spectrophotometric determination of calcium and magnesium in mineral waters using multivariate calibration methods is proposed. The method is based on the development of the reaction between the analytes and Methylthymol Blue at pH 11. Two operational modes were used: static (spectral information) and flow injection (FI) (spectral and kinetic information). The selection of variables was studied. A series of synthetic solutions containing different concentrations of calcium and magnesium were used to check the prediction ability of the partial least-squares models. The method was applied to the analysis of mineral waters and the results were compared with those obtained by complexometry. No significant differences at the 95% confidence level were found. The proposed method is simple, accurate and reproducible, and it could be easily adapted as a portable (static mode) or automatic (FI) method.
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Affiliation(s)
- F Blasco
- Departamento de Química Analítica, Facultad de Farmacia, Universidad de Valencia, Burjassot, Spain
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Fernández FM, Stripeikis JD, Tudino MB, Troccoli OE. Fully automatic on-line separation preconcentration system for electrothermal atomic absorption spectrometry: determination of cadmium and lead in sea-water. Analyst 1997; 122:679-84. [PMID: 9330038 DOI: 10.1039/a607598c] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
An automatic separation preconcentration system coupled to an electrothermal (graphite furnace) atomic absorption spectrometer is described. The preconcentration step is performed on a chelating resin microcolumn (Chelex-100) placed in the injection tip of the autosampler. A time based manifold with two- and three-way solenoid valves commanded by an eight channel microcomputer programmable controller is used for column conditioning, preconcentration and washing steps; no manual operations are involved. Elution is performed by the programmable graphite furnace autosampler and achieved in only one step. Operations involving complete and partial injection of the eluate into the graphite furnace are also discussed. The system was applied to the determination of Cd and Pb in near shore sea-water from Patagonia, Argentina. Detection limits of 1 and 8 ng l-1 were obtained for Cd and Pb respectively. Analysis of a certified reference material (CASS-3) showed good agreement with the certified values.
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Affiliation(s)
- F M Fernández
- Departamento de Química Inorgánica, Analítica y Química Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
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Wigdorovitz A, Zamorano P, Fernández FM, López O, Prato-Murphy M, Carrillo C, Sadir AM, Borca MV. Duration of the foot-and-mouth disease virus antibody response in mice is closely related to the presence of antigen-specific presenting cells. J Gen Virol 1997; 78 ( Pt 5):1025-32. [PMID: 9152419 DOI: 10.1099/0022-1317-78-5-1025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Natural and experimental hosts infected with foot-and-mouth disease virus (FMDV) develop a long-lasting immune response that is closely related to the presence of anti-FMDV antibodies (Ab). We show here that spleen cells from animals which had been infected 3 or more months previously induced an anti-FMDV-Ab response in untreated animals which lasted more than 210 days after cell transfer. Persistence of infectious virus was excluded since virus isolation or detection of the viral genome by PCR in donor splenocytes were consistently negative. The role of antigen presentation (AP) in this phenomenon was studied in vivo by using irradiated splenocytes from virus-sensitized donor mice. Although these irradiated cells were unable to induce anti-FMDV-Ab in normal or irradiated recipient mice, they elicited a strong secondary reaction in FMDV-pre-sensitized recipients. The presence of AP cells (APC) presenting FMDV epitopes (FMDV/APC) was also analysed in mice sensitized to FMDV in different ways. A close correlation between FMDV/APC and the presence of anti-FMDV-Ab was found in infected mice as well as in mice immunized with different doses of inactivated virus, with or without adjuvants. Experiments in vivo and in vitro showed that the APC activity can be specifically blocked with either anti-MHC class II monoclonal antibody or anti-FMDV antiserum, and is dependent on the presence of T cell function. These results strongly suggest that persistent FMDV/APC are responsible for the existence and maintenance of an anti-virus immune response regardless of the immunization method used.
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Affiliation(s)
- A Wigdorovitz
- Instituto de Virología, C.I.C.V., INTA-Castelar, Buenos Aires, Republica Argentina
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Fernández FM, Castro EA. Comment on "Iterative Bogoliubov transformations and anharmonic oscillators". Phys Rev A 1993; 48:3398-3399. [PMID: 9909999 DOI: 10.1103/physreva.48.3398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Fernández FM, Castro EA. A new implementation of stationary perturbation theory for separable quantum‐mechanical problems. J Chem Phys 1993. [DOI: 10.1063/1.464836] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Cornaglia EM, Fernández FM, Gottschalk M, Barrandeguy ME, Luchelli A, Pasini MI, Saif LJ, Parraud JR, Romat A, Schudel AA. Reduction in morbidity due to diarrhea in nursing beef calves by use of an inactivated oil-adjuvanted rotavirus-Escherichia coli vaccine in the dam. Vet Microbiol 1992; 30:191-202. [PMID: 1313621 PMCID: PMC7117420 DOI: 10.1016/0378-1135(92)90113-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
An outbreak of neonatal diarrhea occurred among beef calves (2000 animals) from one large Argentinian farm in 1985. Rotavirus was detected in 78% (106/136) and enterotoxigenic Escherichia coli in 1.5% of the samples (2/136) obtained from sick calves. In comparison rotavirus was identified in only 1.6% (1/63) of the samples from clinically healthy calves. The rotavirus strain responsible for the outbreak was characterized as serotype 6 belonging to group A. In the following three years the protective capacity of a combined rotavirus-E. coli inactivated vaccine administered to the dams during the last third of the gestation period was evaluated on this farm by comparison of morbidity due to diarrhea in calves from vaccinated vs. placebo cows within the same year. The morbidity due to diarrhea among calves from dams in the vaccinated and placebo groups was 34% and 77%, respectively in 1986; 23% and 47% in 1987, and 15% and 34%, in 1988. In 1987 morbidity of diarrhea in calves born from vaccinated heifers was 54% and 74% in calves from placebo heifers. In 1988 morbidity from diarrhea was 41% and 54%, respectively among calves in these two groups. In all experiments, calves from heifers showed significantly greater morbidity than calves from cows. Differences in diarrhea morbidity between the vaccinated and placebo groups were statistically significant (P less than 0.05). Additional studies showed that the diarrhea had a significant influence (P less than 0.05) on the average live weight of the calves at weaning (5 to 7 months) with an average weight loss of 7.8 kg per calf among the calves affected with diarrhea.
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Affiliation(s)
- E M Cornaglia
- Comisión de Investigaciones Cientificas, Buenos Aires, Argentina
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Echave J, Fernández FM, Campanaro M, Micha DA. Construction of effective Hamiltonians for time‐dependent phenomena from variational principles. J Chem Phys 1991. [DOI: 10.1063/1.460811] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Echave J, Fernández FM, Micha DA. A generalized intermediate picture of quantal time evolution using operator algebraic methods. Application to translational–vibrational energy transfer in molecular collisions. J Chem Phys 1991. [DOI: 10.1063/1.459775] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Fernández FM, Ogilvie JF. Application of the hypervirial perturbation theory to the vibrational-rotational spectroscopy of diatomic molecules. Phys Rev A 1990; 42:4001-4007. [PMID: 9904500 DOI: 10.1103/physreva.42.4001] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Fernández FM, Ogilvie JF. Approximate solutions to the Thomas-Fermi equation. Phys Rev A 1990; 42:149-154. [PMID: 9903787 DOI: 10.1103/physreva.42.149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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