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  • Aeroallergen  (2)
  • Solvent effects  (2)
  • Theoretical, Physical and Computational Chemistry  (2)
  • Arrhythmia  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of Solvation on Ozonolysis Reaction Intermediates and Transition States (2000)
    Springer
    Journal of molecular modeling 6 (2000), S. 608-617 
    Details
    ISSN: 0948-5023
    Keywords: Ozonolysis ; Ozone ; Reaction mechanisms ; Solvent effects ; Theoretical calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electrostatic solvent effects on the ozonolysis of ethylene have been investigated using correlated ab initio and density functional approaches. We use a simple polarizable continuum model for the solvent. It allows us to evaluate the medium effect on both the electronic and nuclear structure of the chemical species involved in the reaction. The computations confirm that basically the reaction proceeds through the Criegee mechanism. However, formation of the van der Waals complexes ethyl-ene/ozone and carbonyl oxide/formaldehyde also appears to play a role. All the calculated species are stabilized with respect to the reactants except the transition state corresponding to the primary ozonide formation. In general, electrostatic solvent effects are relatively small for activation barriers of single reaction steps and more substantial for the corresponding reaction energies. Moreover, the medium significantly modifies the structure of some species for which polarization effects are crucial.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0089400060608
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation in aqueous solution of N-methylazetidinone as a model of β-lactam antibiotics (1999)
    Springer
    Theoretical chemistry accounts 101 (1999), S. 336-342 
    Details
    ISSN: 1432-2234
    Keywords: Key words:N-Methylazetidinone ; Molecular dynamics ; β-Lactam hydrolysis ; Solvent effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. In this article, we analyze the results of a molecular dynamics simulation in aqueous solution of the N-methylazetidinone molecule, often used to model β-lactam antibiotics. The radial distribution functions (RDFs) corresponding to the most interesting atoms, in terms of reactivity, are presented. We focus our study on the effect of a polar environment on the molecule. The solvent structure around the system is compared to the structure of β-lactam-water complexes, as obtained in a previous study of reaction mechanisms for the neutral and alkaline hydrolyses of N-methylazetidinone. Two types of complexes have been considered which are related to different hydrolysis mechanisms having similar energy barriers at the rate-limiting step of the reaction path. In the first type, the β-lactam-water interaction takes place through the oxygen carbonyl atom and there is agreement between the maxima of the RDFs obtained here and the ab initio structure of the complexes previously reported. In the second type, the interaction takes place through the nitrogen atom and we do not predict a coordination layer around the β-lactam nitrogen atom. The results suggest that in aqueous solution hydrolysis of the carbonyl group is the most probable starting point for the overall hydrolysis reaction. Some discussion on the use of cluster models to represent the solvent effect is included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002140050450
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Antiarrhythmic actions of clemizole as pharmacologic evidence for a circus movement mechanism in atrial flutter (1969)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 262 (1969), S. 325-336 
    Details
    ISSN: 1432-1912
    Keywords: Clemizole ; Arrhythmia ; Antihistaminics ; Cell Membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The antihistaminic clemizole was studied as an antiarrhythmic in a preparation in which two arrhythmias of different nature and mechanism were produced in the right atrium of anesthetized dogs. One of the arrhythmias was a circus movement flutter induced by the method of Rosenblueth and García Ramos; the other, an ectopic focus induced by local application of aconitine in the auricular appendage, electrically isolated from the rest of the atrium. Clemizole selectively converted the flutter to sinus rhythm with little action on the coexistent aconitine dysrhythmia. It did not modify arterial pressure. In effective doses the wave length of the impulse was increased by prolongation of the refractory period without significant reduction in conduction velocity. Similarly, in subendocardial cells of isolated rat atria, clemizole in appropriate concentrations retards repolarization with little effect on the rate of depolarization. These results afford pharmacological evidence for the existence of atrial circus movement arrhythmias which can respond to prolongation of the refractory period unaccompanied by effects on other properties of the tissue. Other arrhythmias, self-sustained by the discharge of an ectopic focus, such as the tachysystole produced by aconitine, are not suppressed by similar increase in the refractory period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00538434
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Soybean aeroallergen around the port of New Orleans: A potential cause of asthma (1996)
    Springer
    Aerobiologia 12 (1996), S. 173-176 
    Details
    ISSN: 1573-3025
    Keywords: Aeroallergen ; Soybean asthma ; Immunochemical Assay ; Air sampling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There have been reported epidemics of severe asthma in Barcelona, Spain, linked to a 10 kDa low molecular mass (LMM) allergen from soybean hulls that became airborne during unloading of ships. As a preliminary probe of the potential for dispersion of this allergen in USA cities, four automated air samplers were placed around a grain elevator in New Orleans and operated continuously from May to October 1990. The allergen was extracted from the filters and immunochemically assayed for soybean aeroallergen. On 31 separate days, the airborne allergen concentration in at least one of the samples was over 10000 U/m3 similar to those observed in Barcelona on some epidemic days. Areas North and East of the elevator were most affected. Serologie studies showed that of 50 asthmatics from New Orleans who were participants in an unrelated clinical study 4 or 8% demonstrated elevated titers of IgE antibody to LMM soybean allergen. Only 1 of 475 control sera (half of which were also asthmatic) obtained elsewhere in the US was positive for LMM soybean IgE antibody. Based on the findings in this study, there is a great possibility that on some days there is enough soybean allergen in the air and a sufficient frequency of soybean aeroallergen RAST positive asthmatics in New Orleans to warrant further investigation of the contribution of soybean aeroallergen to asthma around the port of New Orleans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02248146
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Soybean aeroallergen around the port of New Orleans: a potential cause of asthma (1996)
    Springer
    Aerobiologia 12 (1996), S. 173-176 
    Details
    ISSN: 1573-3025
    Keywords: Aeroallergen ; Soybean asthma ; Immunochemical Assay ; Air sampling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There have been reported epidemics of severe asthma in Barcelona, Spain, linked to a 10 kDa low molecular mass (LMM) allergen from soybean hulls that became airborne during unloading of ships. As a preliminary probe of the potential for dispersion of this allergen in USA cities, four automated air samplers were placed around a grain elevator in New Orleans and operated continuously from May to October 1990. The allergen was extracted from the filters and immunochemically assayed for soybean aeroallergen. On 31 separate days, the airborne allergen concentration in at least one of the samples was over 10 000 U/m3, similar to those observed in Barcelona on some epidemic days. Areas North and East of the elevator were most affected. Serologic studies showed that of 50 asthmatics from New Orleans who were participants in an unrelated clinical study 4 or 8% demonstrated elevated titers of IgE antibody to LMM soybean allergen. Only 1 of 475 control sera (half of which were also asthmatic) obtained elsewhere in the US was positive for LMM soybean IgE antibody. Based on the findings in this study, there is a great possibility that on some days there is enough soybean allergen in the air and a sufficient frequency of soybean aeroallergen RAST positive asthmatics in New Orleans to warrant further investigation of the contribution of soybean aeroallergen to asthma around the port of New Orleans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02447409
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Conformational analysis of 2-cyano-1,1-dihydroxyethane in solution (1996)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 9 (1996), S. 119-127 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The conformational space of the 2-cyano-1,1-dihydroxyethane molecule was studied at the semi-empirical PM3 level and ab initio MP2/6-31G**//6-31G level in the gas phase and in a low-polarity medium. This system has been chosen as a model compound for 2-cyanocyclohexanone propylene and ethylene acetals. This has allowed the study of the role of polar groups on the relative conformation of two adjacent OH groups, which is of interest also in relation to the anomeric effect in carbohydrate chemistry. Solvent effects are taken into account using a continuum model with general cavity shapes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 7
    Electronic Resource
    Electronic Resource
    Computation of hydration free energies using a parameterized continuum model: Study of equilibrium geometries and reactive processes in water solution (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 148-155 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A parameterized self-consistent reaction field model allowing computation of the total free energy of hydration of organic molecules at the ab initio level is presented. The approach uses electrostatic plus polarization energies calculated with the help of a continuum model. The remaining solvation free energy terms are obtained by a simple formula based on atomic parameters and atomic accessible surface areas (ASAs), which are determined with the ASA analytical algorithm. Analytical derivatives of the atomic surfaces areas have been implemented. The atomic parameters have been obtained by a linear regression fit of the calculated and experimental free energies of solution in water for a set of 35 molecules, leading to a standard deviation of 0.75 kcal/mol. Effects of nonelectrostatic terms on solute geometries, association energies, and activation barriers are illustrated. © 1996 by John Wiley & Sons, Inc.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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