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  • 1
    Electronic Resource
    Electronic Resource
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Theory and Simulations 2 (1993), S. 673-684 
    ISSN: 1018-5054
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is the aim of this work to develop analytical force field expressions that can be rapidly evaluated by computers. The new expressions approximate the energy hypersurfaces as described by the usual force fields. The energies and the derivatives of the energy expressions, i. e. the forces acting on the atoms, in most cases can be very quickly calculated as functions of one squared distance of two atoms per interaction, avoiding slow operations like cosine, square root etc. Formulae and algorithms are given to calculate the parameters needed from those of the AMBER force field.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 1667-1678 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The expression “stiffness” of a polymer chain is shown to be ambiguous, and the use of the word “rectilinearity” is proposed to replace it in certain contexts. The influence of non-uniform curvature on Kuhn length and mean-square end-to-end distance of (co)polymers is studied using the frameworks of the freely-rotating-chain model and the Porod-Kratky model. It is shown that every fluctuation around the given mean curvature of a chain increases its overall rectilinearity. Specifically, it is concluded that the rectilinearity increases with increasing fluctuation magnitude and with increasing separation of the different curvatures along the chain, i. e., it becomes greater in the order: alternating, random and block copolymer.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 5 (1996), S. 829-835 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is shown that the recently developed scaling theory for the second virial coefficient, A2, of dilute solutions of polymers with non-uniform molecular weight distributions in a good solvent is able to explain in principle all seemingly contradictory observations reported in the literature, in contrast to all other theories proposed so far.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 5 (1996), S. 947-956 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular dynamic (MD) simulations based on two different force fields, CVFF and CFF91, were carried out in order to check their feasibility for the structural investigation of the wool intermediate filament (IF) monomeric unit. Selecting an ideal α-helix as start conformation, all MD-simulations with CVFF in vaccum show the α-helix to be unstable. Independently of the amino acid sequence of the α-helix, a new helical structure with a larger diameter arises during the MD-simulation, due to a shift of the intrahelical hydrogen bonds. However in simulations with surrounding water the α-helix remains stable throughout the simulations with the CVFF force field. In contrast to this, MD-simulations in vaccume based on the CFF91 force field are able to determine different stabilities for the α-helical start conformation of various IF-segments, that agree well with secondary structure predictions. The simulation results obtained with CFF91 in vacuum can like wise be verified using an explicit water environment. We found that higher partial charges attributed to the atoms of the amide groups that form the intrahelical hydrogen bonds are the reason for the superiority of the CFF91 force field.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 710-710 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 4 (1995), S. 655-666 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This investigation shows that Markov-chain copolymers can be regarded as random copolymers the segment lengths of which depend on the copolymerization parameters. It was possible to derive simple analytical formulae for the mean-square end-to-end distance (〈r2〉), the Kuhn length, and the distribution of r2 under theta-conditions. The results of these equations are in excellent agreement with data from simulations. It is shown that 〈r2〉 as well as the non-uniformity of r2 increase strongly with increasing probabilities of homopropagation, i.e., with increasing mean homosequence lengths. Furthermore it is demonstrated by simulation that even chains of identical length and composition show a distribution of r2 because of different arrangements of the sequences inside the chains. For chains or chain segments shorter than the average homosequences, a double-peak distribution of r2 is found. The equations derived in this paper can be applied to real copolymers as well as to chains the curvature of which is altered locally by the association of ligands.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A parallel algorithm is developed that allows efficient Langevin-dynamics simulations of macromolecular coils, which is the usual structure of synthetic polymers in solution and in bulk. Contrary to usual so-called spatial decomposition algorithms, we map the one-dimensional topology of the chain molecule on the parallel computer. The speedup of the algorithm is measured on different multi-processor systems. The reliability of the parallel calculations is shown by comparison with sequential simulations.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 6 (1997), S. 963-964 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 5 (1996), S. 157-163 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Scaling theory is applied to derive expressions describing the influence of polymolecularity on the second virial coefficient, A2, as obtained from osmotic pressure and light scattering measurements. Numerical values of polymolecularity correction factors are calculated for Schulz-Zimm and logarithmic normal distributions of the molecular weight, different qualities of the solvent and several ratios of the weight-average and the number-average molecular weights M̄w/M̄n. It is found that in the equation \documentclass{article}\pagestyle{empty}\begin{document}$ A_2 = K_{A_2 } \cdot M_{{\rm av}}^{a_{A_2 } } $\end{document} the weight-average molecular weight is a good approximation for Mav if A2 is measured via light scattering, while the number-average molecular weight can be inserted for Mav if A2 stems from osmotic pressure measurements.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 6 (1997), S. 1-12 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Simulations of the stability of the secondary and tertiary structure of the α-keratin intermediate filament (IF) monomeric unit of wool are reported. Based on the assumed secondary structure three segments of the primary structure were selected: 1A, L12, and a part of 2B. Starting with an ideal α-helical conformation for each IF-segment, molecular dynamics simulations were carried out on the atomistic level at various temperatures in vaccum using the CFF91 force field. In either simulation the expected destabilization of the helical structure with increasing simulation temperature was observed. By use of different procedures of analysis, transition temperatures for the α-helical denaturation were determined that are significantly higher for the supposedly α-helical segments 1A and 2B than for the linker segment L12. The different stabilities of segments 1A and L12 were further verified through simulations in water environment that show the linker segment to be non-helical at room temperature. The lower transition temperature of segment L12 confirms the expectation that its amino acid sequence leads to increased conformational flexibility. The mobility of the water molecules surrounding the IF-segment is found to be significantly decreased by protein/water interactions.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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