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  • Articles: DFG German National Licenses  (3)
  • Ion channel  (2)
  • 310-/Α-HELICES  (1)
  • 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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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ion channel formation by zervamicin-IIB (1993)
    Springer
    European biophysics journal 21 (1993), S. 369-383 
    Details
    ISSN: 1432-1017
    Keywords: Ion channel ; Peptaibol ; Molecular modelling ; Channel-forming peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Zervamicin-IIB (Zrv-IIB) is a 16 residue peptaibol which forms voltage-activated, multiple conductance level channels in planar lipid bilayers. A molecular model of Zrv-IIB channels is presented. The structure of monomerc Zrv-II3 is based upon the crystal structure of Zervamicin-Leu. The helical backbone is kinked by a hydroxyproline residue at position 10. Zrv-IIB channels are modelled as helix bundles of from 4 to 8 parallel helices surrounding a central pore. The monomers are packed with their C-terminal helical segments in close contact, and the bundles are stabilized by hydrogen bonds between glutamine 11 and hydroxyproline 10 of adjacent helices. Interaction energy profiles for movement of three different probes species (K+, Cl− and water) through the central pore are analyzed. The conformations of: (a) the sidechain of glutamine 3; (b) the hydroxyl group of hydroxyproline 10; and (c) the C-terminal hydroxyl group are “optimized” in order to maximize favourable interactions between the channel and the probes, resulting in favourable interaction energy profiles for all three. This suggests that conformational flexibility of polar sidechains enables the channel lining to mimic an aqueous environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185864
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    Paper (German National Licenses)
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  • 3
    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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    Paper (German National Licenses)
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