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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular modeling 2 (1996), S. 51-61 
    ISSN: 0948-5023
    Keywords: Conformational search ; Molecular mechanics ; Potential Energy (hyper)surface ; D,L-form of amino acid ; Conformational flexibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Conformational potential energy hypersurfaces, PES, for the terminally blocked L-Cysteine, L,L-Cystine and D,L-Cystine have been analyzed by means of molecular mechanics in combination with the programs ROSE, CICADA, PANIC and COMBINE. Low energy conformations and conformational transitions, conformational channels, have been located. Global and fragmental flexibility and conformational softness have been calculated for each conformer as well as for the entire molecule. The PES analyses were used for simulation of conformational movement based on Boltzmann probability of the points obtained on the PES. Boltzmann travelling revealed interesting correlated conformational movement where three or even more dihedral angles changed simultaneously. It could be shown that conformational behavior and flexibility were strongly influenced by the absolute configurations of the amino acids in the peptides.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of chemical information and modeling 31 (1991), S. 380-386 
    ISSN: 1520-5142
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2234
    Keywords: Mathematical model ; Logical structure of chemistry ; Potential energy hypersurface ; Graph theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A mathematical model of the logical structure of chemistry is suggested. The model is based on the phenomenon of convertibility between chemical species which is expressed by the so-called convertibility function Γ. In the center of the model there is the potential energy (hyper)surface, PES. A heuristic modification of the general convertibility function is presented. Several algorithms have been developed for an analysis of PES which is described by paths, and for heuristic obtaining of PES paths. The notion ofK-barrier of conformational PES is introduced as well as an algorithm for its computation.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2234
    Keywords: Conformational analysis ; Chemical reaction ; Potential energy hypersurface ; Mathematical model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Proposals of heuristic convertibility functions and general drivers for conformational and reaction potential energy (hyper)surfaces study are suggested. The functions and drivers are formulated under the mathematical model of the logical structure of chemistry which has been published in the previous paper. A part of the described theory has been realized as the computer program system DAISY.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical chemistry 3 (1989), S. 91-115 
    ISSN: 1572-8897
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract The notion of a Synthetic Precursor/Successor (SPS) is introduced, and an algorithm for the generation of all SPSs is given. The recursive algorithm is based on the so-called “stabilization” of a reaction center with respect to the whole synthon. The notion of the immersion of a subsynthon into a synthon and the notion of the order of SPSs are introduced. A mathematical theory of SPSs is given.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical chemistry 3 (1989), S. 73-89 
    ISSN: 1572-8897
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract A mathematical model of a synthon is suggested. The synthon is modelled by a special so-calledS-matrix. The notion of isomeric synthons on the set of atoms A and that of a Family of Isomeric SynthonsFIS (A) is introduced. The chemical reaction is represented by a matrix equation and it is modelled by the so-calledSR-matrix. The notion of the reaction distance (RD) between two isomeric synthons is defined. A mathematical theory of the S andSR-matrices is developed.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-4986
    Keywords: Blood group ; molecular modelling ; oligosaccharide conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The three-dimensional structures of fourteen histo-blood groups carbohydrate antigens have been established through a combination of molecular mechanics and conformational searching methods. The conformational space available for each disaccharide, constituents of these determinants, has been throroughly characterized. The results have been organized in a data bank fashion. Larger relatives, i.e. 14 tri- and tetrasaccharides of histo-blood group antigens, have been modelled using a different method for exploring the complex potential energy surface. This approach is aimed at establishing all the possible families of conformations, along with the conformational pathways. Different conformational behaviours are exhibited by these oligosaccharides. Some of them, i.e. LeX and LeY tri and tetrasaccharides, are very rigid; 99% of their populations belong to the same conformational family. Others, like H type 1, H type 2 or H type 6 oligosaccharides, are essentially rigid, but a secondary conformational family, corresponding to 3–4% of the total population, can arise. Finally, the H types 3 and 4 trisaccharides, and the A type 1 and A type 2 tetrasaccharides are predicted to behave rather flexibly. The information gathered in the present investigation has been used to analyse the body of experimental evidence, either physical or biological, available for this series of carbohydrate antigens. Of special interest are the several different alignments that can be proposed for these molecules. They yield a realistic definition of the three-dimensional features of the epitopes thereby providing essential information about how carbohydrate antigens are recognized by proteins.
    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 15 (1994), S. 937-946 
    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 methodology of conformational potential energy (hyper)surface (PES) elucidation is the subject of this article. The decomposition of the recently developed software CICADA and its implementation in the distributed environment using PVM (parallel virtual machine) is presented. CICADA has been chosen for the parallelization because of its ability to elucidate systematically the low-energy areas of PES in polynomial time. This makes the method applicable on larger systems which are beyond the scope of the grid search. To show the level of parallelization, conformational PES of two molecules, cyclohexane and terminally blocked alanine, have been studied by the distributed version, D-CICADA, and results have been compared to those of the sequential version. D-CICADA was tested on several virtual machines composed of DEC and Sun workstations. The timing shows good efficiency for both the decomposition of the original algorithm and the PVM environment. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 16 (1995), S. 296-310 
    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 potential energy hypersurfaces (PES) of several carbohydrate molecules were studied with a new algorithm for conformational searches, CICADA (Channels in Conformational Space Analyzed by Driver Approach) interfaced with the molecular mechanics program MM3(92). The method requires (1) one or a few low-energy conformations as starting points; and (2) designation of the torsion angles important for understanding the conformational behavior of the molecule. The PES is explored by driving separately each selected torsion angle (in both directions) with a concomitant full-geometry optimization at each increment (except for the driven angle). When a minimum has been detected, the molecule is freely optimized, and the minima so detected are then stored if not encountered previously. The new minima serve as starting structures for further explorations. The results from CICADA permit prediction of relative and absolute flexibility and conformational softness for both the entire molecule as well as for individual group rotations and local minima. The carbohydrates analyzed were Me-α-D-glucopyranoside, β-D-GlcNAc(1-2)α-D-Man, and α-D-GalNAc(1-3)[α-L-Fuc(1-2)]Gal-O-Me. All the low-energy conformers along with the transition states and flexibilities features were characterized. CICADA found all minima and low-energy conversion pathways for the disaccharide that were found by a traditional grid search. In contrast to the grid search method, CICADA concentrates mostly on the exploration of the low-energy regions of the PES, thereby saving a significant amount of computational time. The performance of the method opens new routes for exploring conformational space of larger molecules, such as oligosaccharides. © 1995 by John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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