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  • 1
    Electronic Resource
    Electronic Resource
    The properties of ion channels formed by zervamicins (1992)
    Springer
    European biophysics journal 21 (1992), S. 117-128 
    Details
    ISSN: 1432-1017
    Keywords: Ion channel ; Peptaibol ; Channel forming peptide ; Planar bilayer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The zervamicins (Zrv) are a family of 16 residue peptaibol channel formers, related to the 20 residue peptaibol alamethicin (Alm), but containing a higher proportion of polar sidechains. Zrv-1113 forms multi-level channels in planar lipid (diphytanoyl phosphatidylcholine) bilayers in response to cis positive voltages. Analysis of the voltage and concentration dependence of macroscopic conductances induced by Zrv-IIB suggests that, on average, channels contain ca. 13 peptide monomers. Analysis of single channel conductance levels suggests a similar value. The pattern of successive conductance levels is consistent with a modified helix bundle model in which the higher order bundle are distorted within the plane of the bilayer towards a “torpedo” shaped cross-section. The kinetics of intro-burst switching between adjacent conductance levels are shown to be approximately an order of magnitude faster for Zrv-IIB than for Alm. The channel forming properties of the related naturally occurring peptaibols, Zrv-Leu and Zrv-IC, have also been demonstrated, as have those of the synthetic apolar analogue Zrv-Al-16. The experimental studies on channel formation are combined with the known crystallographic structures of Zrv-Al-16 and Zrv-Leu to develop a molecular model of Zrv-II3 channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185426
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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
    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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  • 4
    Electronic Resource
    Electronic Resource
    Stereochemistry of peptides containing 1-aminocyclopentanecarboxylic acid (Acc5): Solution and solid-state conformations of Boc-Acc5-Acc5-NHMe (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1635-1644 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational analysis of a protected homodipeptide of 1-aminocyclopentanecarboxylic acid (Acc5) has been carried out. 1H-nmr studies establish a β-turn conformation for Boc-Acc5-Acc5-NHMe in chloroform and dimethylsulfoxide solutions involving the methylamide NH in an intramolecular hydrogen bond. Supportive evidence for the formation of an intramolecular hydrogen bond is obtained from ir studies. X-ray diffraction studies reveal a type III β-turn conformation in the solid state stabilized by a 4 → 1 hydrogen bond between the Boc CO and methylamide NH groups. The φ,ψ values for both Acc5 residues are close to those expected for an ideal 310-helical conformation (φ≃ ± 60°, ψ∼ ±30°).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250907
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