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Sheet-Like Assemblies of Charged Amphiphilic α/β-Peptides at the Air–Water Interface

Authors

  • Shlomit Segman-Magidovich,

    1. Avram and Stella Goldstein-Goren, Department of Biotechnology Engineering and The Ilze Katz Institute for Nanoscale Technology, Ben Gurion University of the Negev, P. O. Box 653, Beer-Sheva 84105 (Israel), Fax: (+972) 8-6472983
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  • Myung-ryul Lee,

    1. Department of Chemistry, University of Wisconsin 1101, University Avenue, Madison, WI 53706 (USA), Fax: (+1) 608-265-4534
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  • Vladimir Vaiser,

    1. Avram and Stella Goldstein-Goren, Department of Biotechnology Engineering and The Ilze Katz Institute for Nanoscale Technology, Ben Gurion University of the Negev, P. O. Box 653, Beer-Sheva 84105 (Israel), Fax: (+972) 8-6472983
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  • Bernd Struth,

    1. HASYLAB at DESY, Notkestrasse 85, D-22603, Hamburg (Germany)
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  • Prof. Dr. Samuel H. Gellman,

    Corresponding author
    1. Department of Chemistry, University of Wisconsin 1101, University Avenue, Madison, WI 53706 (USA), Fax: (+1) 608-265-4534
    • Department of Chemistry, University of Wisconsin 1101, University Avenue, Madison, WI 53706 (USA), Fax: (+1) 608-265-4534
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  • Dr. Hanna Rapaport

    Corresponding author
    1. Avram and Stella Goldstein-Goren, Department of Biotechnology Engineering and The Ilze Katz Institute for Nanoscale Technology, Ben Gurion University of the Negev, P. O. Box 653, Beer-Sheva 84105 (Israel), Fax: (+972) 8-6472983
    • Avram and Stella Goldstein-Goren, Department of Biotechnology Engineering and The Ilze Katz Institute for Nanoscale Technology, Ben Gurion University of the Negev, P. O. Box 653, Beer-Sheva 84105 (Israel), Fax: (+972) 8-6472983
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Abstract

There is growing interest in the design of molecules that undergo predictable self-assembly. Bioinspired oligomers with well-defined conformational propensities are attractive from this perspective, since they can be constructed from diverse building blocks, and self-assembly can be directed by the identities and sequence of the subunits. Here we describe the structure of monolayers formed at the air–water interface by amphiphilic α/β-peptides with 1:1 alternation of α- and β-amino acid residues along the backbone. Two of the α/β-peptides, one a dianion and the other a dication, were used to determine differences between self-assemblies of the net negatively and positively charged oligomers. Two additional α/β-peptides, both zwitterionic, were designed to favor assembly in a 1:1 molar ratio mixture with parallel orientation of neighboring strands. Monolayers formed by these α/β-peptides at the air–water interface were characterized by surface pressure–area isotherms, grazing incidence X-ray diffraction (GIXD), atomic force microscopy and ATR-FTIR. GIXD data indicate that the α/β-peptide assemblies exhibited diffraction features similar to those of β-sheet-forming α-peptides. The diffraction data allowed the construction of a detailed model of an antiparallel α/β-peptide sheet with a unique pleated structure. One of the α/β-peptide assemblies displayed high stability, unparalleled among previously studied assemblies of α-peptides. ATR-FTIR data suggest that the 1:1 mixture of zwitterionic α/β-peptides assembled in a parallel arrangement resembling that of a typical parallel β-sheet secondary structure formed by α-peptides. This study establishes guidelines for design of amphiphilic α/β-peptides that assemble in a predictable manner at an air–water interface, with control of interstrand orientation through manipulation of Coulombic interactions along the backbone.

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