This paper describes the synthesis and supramolecular organization of two novel hybrid
diblock copolymers based on poly(ethylene glycol) (PEG) and peptide sequences inspired by the coiled
coil protein folding motif. The self-organization of the diblock copolymers is driven by the tendency of the
peptide segments to form well-defined tertiary structures. In contrast to conventional amphiphilic block
copolymers, whose self-organization is driven by unspecific hydrophobic interactions and leads to
polydisperse aggregates, it was anticipated that this approach could allow precise control over the
aggregation number in aqueous solution. Circular dichroism and analytical ultracentrifugation experiments indicated that the self-organization properties of the peptide segments are retained upon conjugation
of PEG, and discrete, well-defined supramolecular aggregates are formed. No evidence was found for
unspecific self-organization of the diblock copolymers to large polydisperse structures, as it is the case
for conventional amphiphilic block copolymers. In contrast, the self-organization of the PEG-b-peptide
diblock copolymers is described as an equilibrium between unimeric block copolymer molecules and dimeric
and tetrameric coiled coil aggregates. The relative amounts of these species depend on concentration,
temperature, solvent, and the molecular weight of the PEG block.
This study investigates the structure and organization of a series of hybrid diblock copolymers based on poly(ethylene glycol) (PEG) and peptide sequences inspired by the coiled coil protein folding motif. Circular dichroism spectroscopy and analytical ultracentrifugation experiments indicate that the peptide sequences in these block copolymers act as structure-directing auxiliaries and mediate the formation of discrete nanosized assemblies. This self-assembly process is driven by the very specific folding and organization properties of the peptide sequences and does not involve unspecific interactions leading to large polydisperse structures. The present study also demonstrates that the self-assembly properties of the hybrid block copolymers can be controlled via selective replacement of one or two amino acid residues in the peptide block. This is an attractive feature in view of possible biomedical applications. Preliminary biological experiments show that the properties of these polymers correlate with their selfassembly behavior.
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