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  • Articles: DFG German National Licenses  (46)
  • Chemistry  (45)
  • (Micelle)  (1)
  • 310/α-helix transition  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Fluorescent probe studies of mixed micelles of phospholipids and bile salts. Effect of cholesterol incorporation
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 597 (1980), S. 70-82 
    Details
    ISSN: 0005-2736
    Keywords: (Micelle) ; Alkylamine ; Bile salt ; Cholesterol incorporation ; Fluorescent probe
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2736(80)90151-0
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  • 2
    Electronic Resource
    Electronic Resource
    Helix packing of leucine-rich peptides: A parallel leucine ladder in the structure of Boc-Aib-Leu-Aib-Aib-Leu-Leu-Leu-Aib-Leu-Aib-OMe (1992)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 324-330 
    Details
    ISSN: 0887-3585
    Keywords: X-ray diffraction analysis ; hydrogen bonds ; peptide conformation ; 310/α-helix transition ; antiparallel helix packing ; leucyl-leucyl interaction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The packing of peptide helices in crystals of the leucine-rich decapeptide Boc-Aib-Leu-Aib-Aib-Leu-Leu-Leu-Aib-Leu-Aib-OMe provides an example of ladder-like leucylleucyl interactions between neighboring molecules. The peptide molecule forms a helix with five 5→1 hydrogen bonds and two 4→1 hydrogen bonds near the C terminus. Three head-to-tail NH ċ O = C hydrogen bonds between helices form continuous columns of helices in the crystal. The helicial columns associate in an antiparallel fashion, except for the association of Leu ċ Leu side chains, which occurs along the diagonal of the cell where the peptide helices are parallel. The peptide, with formula C56H102N10O13, crystallizes in space group P212121 with Z = 4 and cell parameters a = 16.774(3) Å, b = 20.032(3) Å and c = 20.117(3) Å; overall agreement factor R = 10.7% for 2014 data with |Fobs| 〈 3σ(F); resolution 1.0 Å.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340120404
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  • 3
    Electronic Resource
    Electronic Resource
    Apolar peptide models for conformational heterogeneity, hydration, and packing of polypeptide helices: Crystal structure of hepta- and octapeptides containing α-aminoisobutyric acid (1990)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 7 (1990), S. 62-73 
    Details
    ISSN: 0887-3585
    Keywords: hydrophobic α-helices ; water insertion into helix ; water in hydrophobic pocket ; helix unfolding ; helix folding ; parallel packing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The crystal structures of two helical peptides Boc-Val-Ala-Leu-Aib-Val-Ala-Leu-OMe (VALU-7) and Boc-Val-Ala-Leu-Aib-Val-Ala-Leu-Aib-OMe (VALU-8) have been determined to a resolution of 1.0 and 0.9 Å, respectively. Both the seven and eight residue peptides crystallize with two conformers per asymmetric unit. The VALU-8 conformers are completely helical and differ only at the C-terminus by a sign reversal of the φ, ψ angles of the last residue. One of the VALUE-7 conformers occurs as a normal α-helix, whereas in the other, the N(7)=O(3) α-type hydrogen bond is ruptured by the entry of a water molecule (W) into the helix, which in turn makes hydrogen bonds N(7)⃛W = 2.97 Å and ⃛O(3) = 2.77 Å. The other side of the water molecule is surrounded by a hydrophobic pocket. These two conformers give a static representation of a step in a possible helix unwinding or folding process. In the value-8 crystal the helices aggregate in a parallel mode, whereas the aggregation is antiparallel in the VALU-7 crystal. The crystal parameters are VALUE-7 crystal. The crystal parameters are VALUE-7, P21, a = 10.203 (3) Å, b = 19.744 (6) Å, c = 22.561 (6) Å, α = 96.76°, Z = 4, C38, H69N7O10·0.5 H2O, R = 6.65% for 3674 reflections observed 〉3σ(F): and VALU-8, P21, a; = 10.596 (4) Å, b = 27.57 (6) Å, c = 17.745 (5) Å, β = 95.76 (3)°, Z = 4, C42H76N76O11·0.25 CH3OH, R = 6.63% for 4701 reflections observed 〉3σ(F).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340070107
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of organic solvents on protein structures: Observation of a structured helical core in hen egg-white lysozyme in aqueous dimethylsulfoxide (1997)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 29 (1997), S. 492-507 
    Details
    ISSN: 0887-3585
    Keywords: folding intermediates ; NMR ; protein folding ; dimethylsulfoxide ; near-UV circular dichroism ; lysozyme ; molten globules ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A partly folded state of hen egg-white lysozyme has been characterized in 50% DMSO. Low concentrations of DMSO (〈10%) have little effect on the overall folded conformation of lysozyme as seen from 1H NMR chemical shift dispersion. At increasing DMSO concentrations (〉10%) a cooperative transition of the structure to a new, partially folded state is observed. This transition is essentially complete by ∼50% DMSO. NMR studies show an overall decrease in chemical shift dispersion with marked broadening of many resonances. A substantial number of backbone and side chain-side chain NOEs suggests the presence of secondary and tertiary interactions in the intermediate state. Tertiary organization of the aromatic residues is also demonstrated by enhanced near-UV circular dichroism and limited exposure of tryptophans as monitored by iodide quenching of fluorescence. The intermediate state exhibits enhanced binding to hydrophobic dyes. Further, the structural transition from this state to a largely unfolded conformation is cooperative. H/D exchange rates of several amide protons and four indole protons of tryptophans (W28, W108, W111, and W123), measured by refolding from 50% DMSO at different time intervals reveal that protection factors are high for the helical domain, whereas NH groups in the triple stranded antiparallel β-sheet domain are largely solvent-exposed. An ordered hydrophobic core in the intermediate state comprising of helix A, helix B, and helix D is consistent with the high protection factors observed. The structured intermediate in 50% DMSO resembles the early kinetic intermediate observed in the refolding of hen egg white lysozyme, as well as a molten globule state of equine lysozyme at low pH. The results demonstrate the potential use of nonaqueous structure perturbing solvents like DMSO to stabilize partially folded conformations of proteins. Proteins 29:492-507, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of End Group and Aggregation on Helix Conformation: Crystal Structure of Ac-(Aib-Val-Ala-Leu)2-Aib- OMe (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 2 (1996), S. 106-116 
    Details
    ISSN: 1075-2617
    Keywords: all parallel helix assemblies ; helix transition ; 310-/Α-HELICES ; two conformers ; water associated with non-polar helices ; X-ray crystallography ; Chemistry ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The role of end groups in determining stereochemistry and packing in hydrophobic helical peptides has been investigated using an α-aminosobutyric acid (Aib) containing model nonapeptide sequence. In contrast to the Boc-analogue, Ac-(Aib-Val-Ala-Leu)2-Aib-OMe crystallizes with two independent molecules in a triclinic cell. The cell parameters are: space group P1, a=10.100(2)Å, b=15.194(4) Å, c=19.948(5) Å, α=63.12(2)°, β=88.03(2)°, γ=88.61(2)°, Z=2, R=7.96% for 5140 data where |Fo|〉3σ(F). The two independent molecules alternate in infinite columns formed by head-to-tail hydrogen bonding. The helices in the two independent molecules are quite similar to each other but one molecule is rotated ≍123° about its helix axis with respect to the other. All the helical columns pack parallel to each other in the crystal. Replacement of the bulky Boc group does not lead to any major changes in conformation. Packing characteristics are also similar to those observed for similar helical peptides.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/psc.52
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  • 6
    Electronic Resource
    Electronic Resource
    Circular dichroism studies of α-aminoisobutyric acid-containing peptides: Chain length and solvent effects in alternating Aib-L-Ala and Aib-L-Val sequences (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 877-886 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The CD spectra of the peptides Boc-X-(Aib-X)n-OMe (n = 1, 2, 3) and Boc-(Aib-X)5-OMe, where X = L-Ala or L-Val have been examined in several solvents. The X = Ala and Val peptides behave similarly in all solvents, suggesting that the Aib residues dominate the folding preferences of these peptides. The decapeptides adopt helical conformations in methanol and trifluoroethanol, with characteristic negative CD bands at 222 and 205 nm. In the heptapeptides, similar spectra with reduced intensities are observed. Comparison with nmr studies suggest that estimates of helical content in oligopeptides by CD methods may lead to erroneous conclusions. The pentapeptides yield solvent-dependent spectra indicative of conformational perturbations. Peptide association in dioxane results in an unusual spectrum with a single negative band at 210 nm for the decapeptides. Disaggregation is induced by the addition of methanol or water to dioxane solutions. Aggregation of the heptapeptides is less pronounced in dioxane, suggesting that a critical helix length may be necessary to promote association stabilized by helix dipole-dipole interactions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230505
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  • 7
    Electronic Resource
    Electronic Resource
    Stabilization of γ-turn conformations in peptides by disulfide bridging (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 2041-2043 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360241104
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  • 8
    Electronic Resource
    Electronic Resource
    Stereochemistry of α-aminoisobutyric acid peptides in solution: Conformations of decapeptides with a central triplet of contiguous L-amino acids (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 2209-2223 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The decapeptides Boc-Aib-L-Val-Aib-Aib-(L-Val)3-Aib-L-Val-Aib-OMe and Boc-Aib-L-Leu-Aib-Aib-(L-Leu)3-Aib-L-Leu-Aib-OMe have been studied in CDCl3 and (CD3)2SO solutions by 270-MHz1 H-nmr. In CDCl3, the presence of eight intramolecularly hydrogen-bonded NH groups has been established, consistent with a 310-helical conformation, for both decapeptides. In (CD3)2SO, only seven solvent-shielded NH groups are observed, supporting either an α-helical conformation or a partially unfolded 310-helix. Ir studies provided supporting evidence for intramolecularly hydrogen-bonded structures in CHCl3, while CD studies suggest helical conformation in both decapeptides in various solvents. CD studies also support helical folding in the C-terminal hexapeptides. The central triplet of L-amino acids appears to destabilize 310-helical conformations in polar solvents like (CD3)2SO.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360251112
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  • 9
    Electronic Resource
    Electronic Resource
    Solvated helical backbones: X-ray diffraction study of Boc-Ala-Leu-Aib-Ala-Leu-Aib-OMe · H2O (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 773-781 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A second example of insertion of a water molecule into the helical backbone of an apolar peptide is presented here and compared to a similar occurrence in a longer peptide with the same type of sequence of residues, i.e., Boc-Aib-(Ala-Leu-Aib)3-OMe. The backbone of the title compound assumes an approximate 310-helical form with three 4 → 1 hydrogen bonds. In the place of a fourth 4 → 1 hydrogen bond, a water molecule is inserted between O(1) and N(4), and acts as a bridge by forming hydrogen bonds N(4) … W(1) (2.95 Å) and W(1) … O(1) (2.81 Å). The water molecule participates in a third hydrogen bond with a neighboring peptide molecule, W(1) … O(4) (2.91 Å). The insertion of the water molecule causes the apolar peptide to mimic an amphiphilic helix. Crystals grown from ethyl acetate/petroleum ether (reported here) or from methanol/water solution are in space group P212121 with a = 12.024(4) Å, b = 15.714(6) Å, c = 21.411(7) Å, Z = 4 and dcalc = 1.124 g/cm3 for C32H58N6O9 · H2O. The overall agreement factor R is 6.3% for 2707 reflections observed with intensities 〉 3σ(F) and the resolution is 0.90 Å.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280307
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  • 10
    Electronic Resource
    Electronic Resource
    Peptide design: Influence of a guest Aib-Pro segment on the stereochemistry of an Oligo-Val sequence - solution conformations and crystal structure of Boc-(Val)2-Aib-Pro-(Val)3-OMe (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1433-1442 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The peptide Boc-Val-Val-Aib-Pro-Val-Val-Val-OMe has been synthesized to investigate the effect of introduction of a strong β-turn promoting guest segment into an oligopeptide with a tendency to form extended structures. 1H-nmr studies in solution using analysis of NH group solvent accessibility and nuclear Overhauser effects suggest an appreciable solvent dependence of conformations. In chloroform a 310-helical structure is favored while in dimethylsulfoxide an Aib-Pro β-turn with extended arms on either side is suggested. In the crystal, the backbone forms a somewhat distorted 310-helix despite the presence of a Pro residue in the middle. Among the four possible intrahelical hydrogen bonds three are of the 4 → 1 type and one 5 → 1. Head-to-tail NH⃛O=C hydrogen bonds link the helical molecules into continuous columns. The space group is P212121 with a = 11.320(2), b = 19.889(3), and c = 21.247(3) Å.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360291010
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