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  • 1
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 592-603 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Glycine and alanine aminoacids chemistry in solution is explored using a hybrid three parameters density functional (B3PW91) together with a continuum model. Geometries, energies, and vibrational spectra of glycine and alanine zwitterions are studied at the B3PW91/6-31+G** level and the results compared with those obtained at the HF and MP2/6-31+G** levels. Solvents effects are incorporated by means of an ellipsoidal cavity model with a multipolar expansion (up to sixth order) of the solute's electrostatic potential. Our results confirm the validity of the B3PW91 functional for studying aminoacid chemistry in solution. Taking into account the more favorable scaling behavior of density functional techniques with respect to correlated ab initio methods these studies could be extended to larger systems. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 11087-11091 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    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
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  • 6
    ISSN: 1572-8951
    Keywords: Calmodulin ; calcium-binding proteins ; molecular dynamics simulations ; trifluoperazine binding ; ratcheting mechanism of bending ; structure-function relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Calmodulin (CAM) is a modulatory protein that regulates cellular activity by binding to a large number of proteins. Key elements in the Ca2+-dependent mechanism of interaction between CAM and the proteins it activates are the selectivity for Ca2+ ions and the requirement for Ca2+-dependent conformational changes. We report on results from a series of molecular dynamics simulations that identified discrete steps in the mechanism of structural rearrangement of CAM. The findings implicate the side chains of arginine residues in the bending of the central alpha helix. Structural and energetic considerations point to a dynamic hydrogen bonding pattern around the arginine residues as a ratcheting-type mechanism, causing the kinking of the central helix in consecutive steps stabilized by each new pattern of hydrogen bonds. Initial model building studies to locate potential binding sites of ligands such as trifluoperazine (TFP) indicate that the compaction of CAM results in several structural changes, that explain the selective binding of molecules such as TFP in the N-terminal domain. The present studies identify specific residues involved in the process of compaction and point to specific CAM residues involved in the binding of the ligand. These insights lead directly to propositions for experimental engineering of the molecular structure of CAM in order to probe the hypotheses and their consequences for the function of this important protein.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 1077-1088 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The algorithm used by the program GEPOL for a finer description of molecular surface (for a fast calculation of molecular area and volume and for an efficient selection of sampling points) is presented in detail. Different types of surfaces such as van der Waals and Richard's molecular surfaces can be computed. As we described in the first article (J.L. Pascual-Ahuir and E. Silla, J. Comp. Chem., 11, 1047(1990)), GEPOL begins by building a set of spherical surfaces which fill the space which is not solvent accessible. In this second article, a triangular tessellation approach to select the parts of these spherical surfaces which form the molecular surface is described. By using a data coded generic pentakisdodecahedron, each spherical surface is divided in triangular tesserae. A simple method is used to eliminate all triangles found at the intersection volume of the spheres. The center coordinates and the surface of the remaining triangles are used in order to calculate the molecular area and volume and as starting point of the graphic representation of scalar and vector properties. We study the behavior of the method, presenting several examples of application. Special attention is given to the accuracy, spatial invariance and computer efficiency measured by CPU time. Some models of aligned spheres whose area and volume can be found exactly allow us to do a comparative study with a well-known method, analyzing their behavior in line with their respective graining parameters. A fragment of protein is used as an example of the application of the method for characterizing biomolecular surfaces. Aqueous solubility of organic compounds is studied as an example of the experimental property that depends on the molecular area obtaining a good correlation between the logarithm of the solubility and the area calculated using GEPOL.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1047-1060 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The algorithm used by the program GEPOL to compute the Molecular Surface (MS), as defined by Richards, is presented in detail. GEPOL starts like other algorithms from a set of spheres with van der Waals radii, centered on the atoms or group of atoms of the molecule. GEPOL computes the MS by first searching the spaces inaccessible to the solvent and consequently filling them with a new set of spheres. Here we study the behavior of the method with its parameters, presenting several examples of application.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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