Control of self-assemblies and secondary structures in polypeptide-surfactant complexes

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Aalto-yliopiston teknillinen korkeakoulu | Doctoral thesis (article-based)
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Verkkokirja (16749 KB, 32 s.)
TKK dissertations, 256
Polyelectrolyte-surfactant complexes are known to form self-assembled structures at nanometer length scale. When polypeptides are used instead of traditional synthetic polymers, another level of structural control is introduced due to the ability of polypeptides to fold into secondary structures. In this thesis, self-assembly and secondary structure formation of selected cationic homopolypeptides and block copolypeptides are studied in ionic complexes with anionic surfactants. The surfactant architecture as well as the amount of surfactant were varied and their effect on the self-assembly and polypeptide secondary structures was investigated. Articles I, II and III describe the self-assembly of stoichiometric complexes with single and double alkyl tail surfactants. The complexes were found to respond to a simple external trigger, i.e. temperature, by showing structural changes. In addition, when the amount of surfactant was increased from the stoichiometric value, a plasticization effect from solid to soft liquid crystalline material was observed. Plasticization could be important for solid state applications requiring processing. In Articles IV and V, hierarchical self-assemblies, i.e. materials with structures at different length scales, are described. Two approaches were used. In Article IV, an asymmetric triple-tail lipid was found to induce a helical conformation in the polypeptides and packing of the helices into a layered structure with 2D correlation between the helices, resulting in an oblique lattice. Crystallization of the lipid alkyl tails was found crucial for such structure formation. Heating past the melting temperature of the side-chain crystallites caused a reversible order-order transition from oblique to hexagonal self-assembly. In Article V, a diblock copolypeptide with one cationic block was complexed with surfactants and hierarchical structure-and-structure-within-structure self-assemblies were observed. The morphology was found to depend on the surfactant architecture, i.e. the amount of branching in the alkyl tail. In conclusion, this thesis encourages pursuing novel rationally designed self-assemblies based on polypeptides to enable new schemes for biomimetic materials.
Supervising professor
Ikkala, Olli, Prof.
Thesis advisor
Ikkala, Olli, Prof.
polypeptide, surfactant, self-assembly
Other note
  • [Publication 1]: Ramasubbu Ramani, Sirkku Hanski, Ari Laiho, Roman Tuma, Simo Kilpeläinen, Filip Tuomisto, Janne Ruokolainen, Olli Ikkala, Evidence of PPII-like Helical Conformation and Glass Transition in a Self-Assembled Solid-State Polypeptide–Surfactant Complex: Poly(L-histidine)/Dodecylbenzenesulfonic Acid, Biomacromolecules 2008, 9, 1390-1397.
  • [Publication 2]: Sirkku Hanski, Susanna Junnila, László Almásy, Janne Ruokolainen, Olli Ikkala, Structural and Conformational Transformations in Self-Assembled Polypeptide–Surfactant Complexes, Macromolecules 2008, 41, 866-872.
  • [Publication 3]: Susanna Junnila, Sirkku Hanski, Richard J. Oakley, Sami Nummelin, Janne Ruokolainen, Charl Faul, Olli Ikkala, Effect of Double-Tailed Surfactant Architecture on the Conformation, Self-Assembly, and Processing in Polypeptide–Surfactant Complexes, Biomacromolecules 2009, 10, 2787-2794.
  • [Publication 4]: Sirkku Hanski, Susanna Junnila, Antti J. Soininen, Janne Ruokolainen, Olli Ikkala, Oblique Self-Assemblies and Order–Order Transitions in Polypeptide Complexes with PEGylated Triple-Tail Lipids, Biomacromolecules, 2010, ASAP (DOI: 10.1021/bm100972m).
  • [Publication 5]: Sirkku Hanski, Nikolay Houbenov, Janne Ruokolainen, Dimitra Chondronicola, Hermis Iatrou, Nikos Hadjichristidis, Olli Ikkala, Hierarchical Ionic Self-Assembly of Rod–Comb Block Copolypeptide–Surfactant Complexes, Biomacromolecules 2006, 7, 3379-3384.