Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Molecular Dynamics Simulations of a Cationic Thiophene Oligomer and a Nucleotide Complex(Izmir Institute of Technology, 2022) Demirci, Fethi Can; Elmacı Irmak, Nuran; Elmacı Irmak, NuranIn this thesis, parametrization of cationic polythiophene (CPT) and molecular dynamics (MD) simulations of CPT with DNA complexes were performed to understand the behaviors of the CPT with DNA complex and CPT DNA complexes in different salt solutions (NaCl, KCl, MgCl2, CaCl2). The results of MD simulations show that the end-to-end distance of CPT is affected by both the type sequences and length of the DNA, and the addition of 20T elongates the backbone of the oligomer while 20A and MIX ssDNAs almost have no significant effect. When the complementary DNA chain is added to the duplex solutions, the backbone structure of the oligomer becomes very similar to its structure without ssDNAs since Ree values in both cases are almost the same. It was observed that the CPT-20A complex has a more random coil form than the CPT-20T complex. According to the interaction analysis of MD simulations, all the CPT-DNA duplexes except CPT-20A prefer electrostatic interaction rather than π-cation interaction. DNAs like to interact with the oligomer's side chain rather than its backbone in all systems. Thus, electrostatic interactions and the side chain of oligomer play an important role in the structure of duplexes with thymine which gets the highest response from the oligomer. The addition of 20T makes backbone of F0 more elongated and less compact. 20T has higher electrostatic and π-cation interactions. Thus, F0 is more sensitive to 20T than 20A and MIX.Master Thesis Molecular Dynamics Simulation Study on the Interactions Between Dna and a Conjugated Polyelectrolyte (cationic Oligothiophene)(Izmir Institute of Technology, 2019) Nalıncı Bardak, Nehir; Elmacı Irmak, NuranThe absorption spectra of the cationic polythiophenes shift to the red, or the color changes in the solution are visible to the naked eye, when single-strand DNA (ssDNA) is added, so that they can be used as a tool for DNA detection, theranostic applications, and biological sensors. The red shift or color change is explained by the fact that the ssDNA leads to conformational changes in the polythiophene, but the form of structural change remains to be elusive (i.e. flattening, twisting, stacking, etc.). In this study, molecular dynamics (MD) simulations of complexes consisted by ssDNA sequences with different nucleotides and polythiophene containing cationic side group were performed to enlighten the experimental studies. For this purpose, force field parameters of polythiophene which are not present in the current databases, were generated. The interactions between them were analyzed to determine the nature of conformational changes in the polythiophene when ssDNA was added. MD simulations has been carried out with the CHARMM-compatible force field parameters obtained in the content of this work. Radius of gyration of oligomer increases with addition of ssDNA but is more affected by homopurine strand. Planarity index gets larger upon complexation with homopurine and T_rich strand, does not change with others. H-O and electrostatic interactions which are almost doubled in nonplanar complexes can be interpreted as the major sources of conformational changes in oligomer. Considering all types of interactions between atoms in duplexes, it was observed that planarity was high in structures with less interaction of oligomer side groups.