GCRIS

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Molecular Modeling of Polyelectrolytes - Nucleotides / Nucleic Acids Interaction
(01. Izmir Institute of Technology, 2022) Kıbrıs, Erman; Elmacı Irmak, Nuran
In this thesis, poly- N, N, N-trimethyl-3-(4-methylthiophen-3-yl) oxy) propan-1-aminium force field parameters were generated via ffTK and CHARMM program to perform MD simulations. NBFIX parameters for the interactions of adenosine nucleotides and oligomer were also produced to improve simulations. The parameters were verified by comparing MM vs QM calculations, and simulated vs experimental UV/Vis spectra. Our results revealed that force field parameters obtained by CHARMM program can be applied successfully for the MD simulations of CPTs with different types of adenosine nucleotides (AMP, ADP, and ATP). Poly-(3-(2-((4-methylthiophen-3-yl) oxy) ethyl)-1-ethyl-4H-1λ4-imidazol-3-ium) and poly- N,N,N-trimethyl-6-((4-methylthiophen-3-yl) oxy) hexan-1-aminium are used for optical sensors, therefore parametrization and MD simulations for these compounds were performed to see the effect of nucleotides on the backbone structures of oligomers. Generally, increasing the phosphate group on nucleotides stretched out the backbone of structures, but the largest response was observed in the presence of ATP. The salt effect and temperature effect were also investigated on oligomer – nucleotide complexes. The increasing temperature shortened the backbone of the compounds, but not significant as experimentally. Addition of the monovalent or divalent cations do not affect linearity of oligomer structure in ATP medium for O3. However, O1 and O2 have a great respond to ATP with Mg2+, K+ and Ca2+ (most sensed) ions, O2 has almost no respond to ATP without these ions. Ca2+ is a key ion which regulates ATP production by mitochondria. O2 may take a part of a biosensor design to recognize ATP in the presence of Ca+2.
Characterization of Conjugated Polyelectrolytes for Nucleic Acid Sensing, Gene Delivery and Imaging
(01. Izmir Institute of Technology, 2022) Yücel, Müge; Yıldız, Ümit Hakan; Yıldız, Ümit Hakan
In this thesis, cationic derivatives of poly(3-alkylmethoxythiophene) (PT) which are a class of conjugated polyelectrolytes (CPE), have been synthesized. PT has been polymerized via FeCl3 oxidative polymerization, were treated in a set of solvents to elaborate coil conformation of polymer chain in different physicochemical environment. Spectroscopic and scattering techniques have ascertained that ethylene glycol is a good solvent for PT regarding Flory-Huggins theory. The smaller interaction parameter of PT with respect to ethylene glycol than water drives a thermodynamically driven ultra-small particle (Pdot) formation in aqueous phase by a rapid nanophase separation between PTrich ethylene glycol and PT-poor water phase. All CPEs have been then employed to prepare single polymer chain polymer dots (Pdot) by “nanophase separation” method. As a next step, Pdots have been characterized in terms of optical and colloidal properties that they possess in the backbone conformations altered by solvation effect. Regarding their colloidal characteristic, translocation of Pdot into cancerous cells was analyzed compared to healthy cells by 2D cell culture and co-culture studies. It has reported that Pdots have ability to penetrate through nuclear envelope in hepatocellular carcinoma whereas accumulate around nucleus of healthy liver cells in cytoplasm. Additionally, Pdots were studied in breast cancer cell lines to understand the behavior of Pdot staining in 2D cell culture of invasive and non-invasive breast cancer types. The findings suggest that Pdots are prone to penetrate into the invasive cancerous cells attributed to the greater deformations on nucleus membrane of triple negative breast cancer cells. In a next application, the enhanced photophysical property of PT exhibited in ethylene glycol media allows PT to be utilized as a fluorescent probe for determination of single nucleotide polymorphism by a non-amplification-based protocol. Fluorescence emission at specific wavelengths resulted from very distinct conformations of PT chain is the key elements for the SNP detection assay. The evaluation of optical data obtained from the probe with principal component analysis proves the separation of healthy individuals from patients with an overall 96% accuracy.

Phd Degree / Doktora

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