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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 33 (1994), S. 2843-2851 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    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 108 (1998), S. 9540-9549 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An optimization protocol for modeling protein structures on lattice is proposed which is based on self-consistent mean field (SCMF) theory. In this procedure, the protein residues are supposed to be independent, and their possible positions are given by a list of lattice sites. To do this, an effective larger system is considered, in which each residue i is supposed to occupy all possible sites j, each with a weight V(i,j) stored in the so-called lattice probability matrix V. The effective energy of the system is computed, and iteratively minimized with respect to the weights V, the lattice sites being fixed in space. The final self-consistent V matrix describes the conformational space available to the protein, based on the energy function implemented. This energy function contains two types of terms, namely simple geometric terms which ensure bond connectivity and prevent chain intersection, and energy terms specific to the problem of interest. The application of the above protocol to building a lattice model of a protein, given its three dimensional structure, is discussed and compared with other lattice fitting procedures. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 4768-4775 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An analytic formula is developed for calculating the generalized NMR order parameters in a protein from the normal mode analysis (NMA). The generalized order parameter, S˜2, is given as thermal ensemble average of a Taylor series in powers of Δ, the displacement of internuclear vector from its mean. Henry and Szabo developed a method to calculate the ensemble average based on the NMA carried out in the Cartesian coordinate space (CCS). However, atomic motions in each individual CCS normal modes are linear in the three-dimensional space, which may cause interatomic distances even between covalently bonded atoms to change significantly. In this situation Henry and Szabo proposed to use a special formula for S˜2 which includes a trick to compensate such changes. We showed that by carrying out the NMA in the dihedral angle space (DAS) and by interpreting each DAS normal mode into curved atomic motions, S˜2 can be calculated reliably for spin pairs separated up to about 10 intervening covalent bonds by a natural formula without any trick. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature America Inc.
    Nature structural biology 6 (1999), S. 108-111 
    ISSN: 1072-8368
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] The most recent critical assessment of structure prediction meeting (CASP3) revealed significant progress in predicting the three–dimensional folds of proteins with unknown ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature structural biology 2 (1995), S. 163-170 
    ISSN: 1072-8368
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] A new computational procedure which simultaneously provides gap closure and side-chain positioning in homology modelling is described. It uses a database search scheme to generate fragments to model gaps, a rotamer library to define side-chain conformations, and iteratively refines a conformational ...
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5001
    Keywords: Transferred NOE ; Distance geometry ; Tachykinin ; Active conformation ; NK3 receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Senktide is a highly specific and potent analog of neurokinin B, the natural ligand of the tachykinin receptor NK-3. The membrane-bound conformation of senktide, interacting with negatively charged membrane vesicles composed of perdeuterated phosphatidylcholine and phosphatidylglycerol (70:30), has been investigated using two-dimensional transferred nuclear Overhauser effect spectroscopy (TRNOESY). The occurrence of an N-methylated phenylalanine in the peptide's sequence induces a cis-trans-isomerisation of the corresponding peptide bond which is slow on the chemical-shift scale. NMR data indicate a much stronger membrane affinity of the trans isomer, allowing the determination of a highly resolved membrane-bound conformation using distance geometry and energy minimization. The membrane-bound backbone conformation of several residues is found to be close to a left-handed helix, certainly due to the presence of nonnatural residues (succinylated N-terminal, N-methyl-phenylalanine) as well as a glycine. The results are discussed in the context of a possible biological relevance of the membrane-bound conformation, in terms of the affinity and specificity of this neuropeptide.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5001
    Keywords: NMR ; Antigenic peptides ; Structure determination ; NOE back-calculation ; Dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary We have investigated the dynamics and structural behaviour of two antigenic peptides using 1H NMR. The two cyclic peptides mimic the antigenic site A of influenza haemagglutinin protein; they only differ in the way they were cyclized and in the size of their respective linkers. Homonuclear relaxation parameters extracted from a complete NOE matrix were interpreted in terms of local dynamics. A set of distance constraints was deduced from these parameters which allowed 3D models to be constructed using distance geometry. NOE back-calculation was used to check the validity of the final models. Strong variations of internal motion amplitude have been found in both peptides along their backbone. Motions with high amplitudes have been localized in the Gly-Pro-Gly sequence which forms a β-turn in both structures.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 33 (1998), S. 204-217 
    ISSN: 0887-3585
    Keywords: rotamer libraries ; energy minimization ; self consistent mean-field theory ; torsion space ; modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The ab initio folding problem can be divided into two sequential tasks of approximately equal computational complexity: the generation of native-like backbone folds and the positioning of side chains upon these backbones. The prediction of side-chain conformation in this context is challenging, because at best only the near-native global fold of the protein is known. To test the effect of displacements in the protein backbones on side-chain prediction for folds generated ab initio, sets of near-native backbones (≤ 4 Å Cα RMS error) for four small proteins were generated by two methods. The steric environment surrounding each residue was probed by placing the side chains in the native conformation on each of these decoys, followed by torsion-space optimization to remove steric clashes on a rigid backbone. We observe that on average 40% of the χ1 angles were displaced by 40° or more, effectively setting the limits in accuracy for side-chain modeling under these conditions. Three different algorithms were subsequently used for prediction of side-chain conformation. The average prediction accuracy for the three methods was remarkably similar: 49% to 51% of the χ1 angles were predicted correctly overall (33% to 36% of the χ1+2 angles). Interestingly, when the inter-side-chain interactions were disregarded, the mean accuracy increased. A consensus approach is described, in which side-chain conformations are defined based on the most frequently predicted χ angles for a given method upon each set of near-native backbones. We find that consensus modeling, which de facto includes backbone flexibility, improves side-chain prediction: χ1 accuracy improved to 51-54% (36-42% of χ1+2). Implications of a consensus method for ab initio protein structure prediction are discussed. Proteins 33:204-217, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 264-278 
    ISSN: 0887-3585
    Keywords: hydrophobic interactions ; protein stability ; hydrophobicity scale ; protein mutant stability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Hydrophobic interactions are believed to play an important role in protein folding and stability. Semi-empirical attempts to estimate these interactions are usually based on a model of solvation, whose contribution to the stability of proteins is assumed to be proportional to the surface area buried upon folding. Here we propose an extension of this idea by defining an environment free energy that characterizes the environment of each atom of the protein, including solvent, polar or nonpolar atoms of the same protein or of another molecule that interacts with the protein. In our model, the difference of this environment free energy between the folded state and the unfolded (extended) state of a protein is shown to be proportional to the area buried by nonpolar atoms upon folding. General properties of this environment free energy are derived from statistical studies on a database of 82 well-refined protein structures. This free energy is shown to be able to discriminate misfolded from correct structural models, to provide an estimate of the stabilization due to oligomerization, and to predict the stability of mutants in which hydrophobic residues have been substituted by site-directed mutagenesis, provided that no large structural modifications occur. © 1994 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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