Browsing by Subject "peptide"

Now showing 1 - 3 of 3

Open Access
Detecting secondary structure and surface orientation of helical peptide monolayers from resonant hybridization signals
(Nature Publishing Group, 2013) Alici, K. B.; Gallardo I.F.
Hybridization of dominant vibrational modes with meta-surface resonance allows detection of both structural changes and surface orientations of bound helical peptides. Depending on the resonance frequency of meta-molecules, a red- or blue- shift in peptide Amide-I frequency is observed. The underlying coupling mechanism is described by using a temporal coupled mode theory that is in very good agreement with the experimental results. This hybridization phenomenon constitutes the basis of many nanophotonic systems such as tunable coupled mode bio-sensors and dynamic peptide systems driven by infrared signals.
Open Access
Slow release and delivery of antisense oligonucleotide drug by self-assembled peptide amphiphile nanofibers
(2012) Bulut, Selma
Antisense oligonucleotides are short single stranded DNA sequences and they are suggested to be used for treatment of several disorders including cancer. They could enter the cell and specifically inhibit the target gene, however chemical stability, controlled release and intracellular delivery are areas that has to be focused on to increase their efficacy. Gels composed of nanofibrous peptide network have been previously suggested as carriers for controlled delivery of drugs to improve stability and to provide controlled release, but have not been used for oligonucleotide delivery. In this work, a self-assembled peptide nanofibrous system is formed by mixing a cationic peptide amphiphile (PA) with Bcl-2 antisense oligodeoxynucleotide (ODN), G3139, through electrostatic interactions. The self-assembly of PA-ODN gel was characterized by circular dichroism, rheology, atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM and SEM images revealed establishment of the nanofibrous PA-ODN network. Due to the electrostatic interactions between PA and ODN, ODN release can be controlled by changing PA and ODN concentrations in the PA-ODN gel. Cellular delivery of the ODN by PA-ODN nanofiber complex was observed by fluorescently labeled ODN molecule. Cells incubated with PA-ODN complex had enhanced cellular uptake compared to cells incubated with naked ODN. Furthermore, Bcl-2 mRNA amounts were lower in MCF-7 human breast cancer cells in the presence of PA-ODN complex compared to naked ODN and mismatch ODN evidenced by quantitative RT-PCR studies. These results suggest that PA molecules can control ODN release, enhance cellular uptake and present a novel efficient approach for gene therapy studies and oligonucleotide based drug delivery. In follow-up studies, increase in the internalization efficacy of ODN by incorporation of bioactive sequences, RGDS, to peptide sequence was also shown.
Open Access
Supramolecular chiral self-assembled peptide nanostructures
(2016-01) Hatip, Meryem
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.