Supramolecular chiral self-assembled peptide nanostructures
Author
Hatip, Meryem
Advisor
Güler, Mustafa Özgür
Date
2016-01Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Self-assembly process is an easy and convenient bottom-up technique for designing
novel functional materials. Self-assembled peptide amphiphile (PA) molecules are
remarkable building blocks for a wide-range of applications due to their easy
synthesis, biocompatibility, biodegradabability and dynamic nature in aqueous
conditions.
Controlling self-assembly behavior still remains complex, since it can be affected by
multiple factors. Chirality is an important parameter for designing and controlling
self-assembled supramolecular nanomaterials. In this thesis, self-assembly
mechanism of chiral peptide molecules was studied with different driving forces in
order to develop new methodsfor producing self-assembled nanomaterials. In
addition to self-assembly mechanism, different morphologies and chiral behaviors of
the self-assembled supramolecular chiral peptide amphiphile nanostructureswere
monitored with variouscharacterization methods.
pH is a significant contributor for the self-assembly process and this effect was
studied in detail to elucidate pH dependency of supramolecular conformation.
According to morphological characterizations, histidine containing PA molecules
form nanosheet like structures under acidic pH.At the isoelectric point of imidazole,
they have a tendency to form twisted fiber or ribbon structures. Athigh pH
iv
conditions, pH 10, they form nanotubes due to the neutralization of imidazole groups
and π-π interactionsat theside chain of histidine moiety.When another aromatic ring
is included in the sequence, in this case phenylalanine residue, different
nanostructures were observed.
In addition to histidine PA, lysine and glutamic acid containing peptide building
blocks were also studied to understand the effect of electrostatic interactions.
Phenylalanine containing PAs and valine containing PAs were compared in terms of
their chiral self-assembly behaviors. As a result of self-assembly of the positively
charged and negatively charged peptides, well defined nanostructures were obtained.
While valine containing PA molecules form straight nanofibers, phenyl alanine
containing PAs form well ordered rigid twisted fibers and twisted ribbon structures.
Keywords
peptideself-assembly
nanostructured materials
programmed selfassembly
tuning morphology
nanofiber
nanotube
circular dichroism
twisted β- sheet
nanotechnology