Browsing by Subject "Peptides--Synthesis."

Now showing 1 - 3 of 3

Open Access
Electrostatic effects on the self-assembly mechanism of peptide amphiphiles
(2010) Toksöz, Sıla
Self-assembling peptide amphiphiles, synthesized through solid phase peptide synthesis – a bottom-up approach, have been used with various tissue engineering purposes. Peptide amphiphile molecules self-assemble into nanofibers, which form three dimensional networks mimicking the extracellular matrix. Electrostatic interactions affect the formation of nanofibers. The effect of charged groups on the peptides on nanofiber formation were studied in this work. Neutralization of the charged groups by pH change, electrolyte addition or addition of oppositely charged biomacromolecules triggered the aggregation of the peptides. To understand the controlled formation of the gels composed of peptide nanofibers better can help the researchers develop bioactive collagen mimetic nanofibers for tissue engineering studies and use them in angiogenesis. Results obtained by Fourier Transform Infrared Spectroscopy (FT-IR), Circular Dichroism (CD), Rheology, pH titration, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM); as well as the potential of using the peptide amphiphile molecules to promote angiogenesis, are described.
Open Access
Self-assembly of peptide nanofibers and their mechanical properties
(2012) Erkal, Turan Selman
Peptide nanofibers have been drawing attention because of their versatile, tailorable and functional properties in various research areas. The self-assembly mechanism of peptides and peptide amphiphile molecules is generally based on noncovalent interactions like hydrophobic, electrostatic and metal-ligand interactions. In this thesis, I investigated hydrophobic interaction of peptide amphiphiles (PAs) with other hydrophobic molecules and effect of pH change on self-assembly mechanism. The zinc phthalocyanine molecule was used as a hydrophobic probe to be encapsulated by peptide amphiphile molecules, which help to dissolve the molecule in water instead of an organic solvent. Charge neutralization of PAs by pH change led to nanofiber formation, which resulted in encapsulation and organization of zinc phthalocyanine molecules. The degree of self-assembly by pH change determined non-linear optical properties of zinc phthalocyanine molecule. Besides, morphological, mechanical and spectroscopic properties of phthalocyanine containing peptide nanofibers were characterized by TEM, SEM, oscillatory rheology, UV-Vis, fluorescence and circular dichroism spectroscopy. The mechanical properties of peptide and PA hydrogels and nanofibers have an essential place to determine applicability in different areas. Especially, PA and peptide molecules have been widely used in regenerative medicine studies and the stiffness of the extracellular matrix has a significant role on cellular behavior. In this thesis, viscoelastic properties of the peptide and PA gels were studied by oscillatory rheology. In addition to characterization of bulk mechanical properties of peptide gels, adhesion and stiffness of peptide nanofibers were determined by Atomic Force Microscopy.
Open Access
Synthesis and characterization of metallopeptide nanostructures
(2013) Ustahüseyin, Oya
Organic-inorganic hybrid structures play a number of distinguished roles in the living milieu. For instance, metal ions function as cofactors of enzymes and apatite mineralization in bone is driven by collagen nanofibers serve as both physical and chemical templates. These unique interactions in natural systems are examples for development of synthetic materials for many applications such as catalysts, artificial enzymes or materials for regenerative medicine etc. Manufacturing a catalyst at the nanoscale is important due to increased specific surface area and reduced diffusion path length. In this thesis, we demonstrated peptide based bioinspired nanomaterials. The self-assembled peptide nanofibers were utilized as templates for palladium nanoparticle formation. Functionalization of insoluble electrospun nanofibers with a heavy metal binding peptide sequence was utilized to remove toxic metal ions from water. In addition, peptide amphiphile nanofibers complexed with ZnII were used as enzyme mimics. The resulting nanostructures resemble natural bone alkaline phosphatase activity, which is a major enzyme for natural bone apatite formation.