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Öğe DNA groove binder and significant cytotoxic activity on human colon cancer cells: Potential of a dimeric zinc (II) phthalocyanine derivative(2023) Batıbay, Gönül S.; Karaoğlan, Gülnur Keser; Köse, Gülşah Gümrükçü; Kazancıoğlu, Elif Özçelik; Metin, Eyüp; Kalındemirtaş, Ferdane Danışman; Kuruca, Serap Erdem; Arsu, NergisThe interaction of a multi-component system consisting of benzene-1,4-diyldimethanimine-bridged dimeric zinc-phthalocyanine groups (4OMPCZ) with calf thymus DNA (ct-DNA) was investigated using UV-Vis absorption, fluorescence emission spectroscopy methods, and viscosity measurements. The binding constant, Kb, which is an important parameter to gain information about the binding mode, was found as 9.7 x 107 M-1 from the UV-Vis absorption studies. Another important spectrophotometric tool is competitive displacement assays with Ethidium bromide and Hoechst 33342. Through this experiment, a higher KSV value was obtained with Hoechst for the phthalocyanine derivative, 4OMPCZ, and the ct-DNA complex than with ethidium bromide. Additionally, mo-lecular docking studies were conducted to calculate the theoretical binding constant and visualize the in-teractions of 4OMPCZ with a model DNA. According to docking results, although the interactions are mainly located in the major groove of the DNA helix, due to the wrapping, these interactions can also be extended to the minor groove of the DNA. Spectrophotometric, molecular docking, and viscosity studies revealed that the interaction of 4OMPCZ with DNA is likely to be via the major and minor grooves. The in vitro cytotoxic activity of 4OMPCZ was evaluated by MTT assay on human colon cancer cells (HT29) after 72 h of treatment. 4OMPCZ indicated significant cytotoxic activity when stimulated with UV light compared to the standard chemotherapy drugs, fluorouracil (5-FU), and cisplatin on HT29 colon cancer cells. The IC50 value of 4OMPCZ displayed considerably lower concentrations compared to the standard drugs, 5-FU, and cisplatin.Öğe In-situ photochemical synthesis and dielectric properties of nanocomposite thin films containing Au, Ag and MnO nanoparticles(Elsevier, 2021) Mutlu, Saliha; Metin, Eyüp; Yüksel, Süreyya Aydın; Bayrak, Uğur; Nuhoğlu, Ciğdem; Arsu, NergisThioxanthone-Anthracene (TX-A) was used as a one-component Type II photoinitiator for the photopolymerization of PEGMEA/PEGDA monomer mixture consisting of AgNO3, HAuCl4 and MnCl2 metallic salts. In this study, we have seen that nanoparticles (NPs) are distributed differently in solution and in polymer matrices and that the particle size also changes. The size of the AuNPs (8-16 nm) synthesized in the solution in the presence of air atmosphere is smaller than the AuNPs (18-25 nm) synthesized in the polymer matrix. It is also important to state the effect of the atmosphere on the shape and size of the NPs. Thanks to the endoperoxide formation in air atmosphere, the formation of AgNPs in the range of 45-53 nm is possible in solution, while the size of AgNPs increased up to 1900 nm in nitrogen atmosphere. Additionally, radical spin densities were calculated with Density Functional Theory to understand which radical is mainly responsible for the reduction of metal ions to form metal and metal oxide nanoparticles. Peroxy radicals were found to be mainly responsible due to their much higher electron spin density compared to the other radicals. Moreover, the dielectric properties of in-situ formed AuNPs, AgNPs and MnONPs in the nanocomposite films were investigated at room temperature. For all nanocomposite films containing metal NPs, the frequency dependent dielectric constant and dielectric loss are higher than the polymeric films up to about 50 times.Öğe In–situ formation of self-assembled Ag nanoclusters on ct-DNA in the presence of 2-mercaptothioxanthone by using UV–vis light irradiation(Elsevier, 2018) Metin, Eyüp; Batıbay, Gönül S.; Arsu, NergisSelf-assembled silver nanoparticles (Ag NPs) on calf thymus DNA (ct-DNA) chains were synthesized in the presence of 2-mercaptothioxanthone (TX-SH) by use of UV irradiation technique. Thioxanthone itself and its derivatives show interesting photochemical and biological properties. The formation of Ag NPs on the ct-DNA was achieved with and without TX-SH as a thioxanthone derivative photoinitiator which played a photoreducing role for the formation of Ag NPs. The photoreducing reaction of Ag ions to Ag NPs was followed by UV-vis absorption spectroscopy. A new band was observed at 428 nm which was a good sign of the surface plasmon resonance (SPR) of Ag NPs. Fluorescence quenching was effectively observed depending on the irradiation time of the solution, possibly as a result of Ag NPs size. Particle size analysis and Scanning Electron Microscopy (SEM) imaging confirmed the size of the formed Ag NPs and silver nanoclusters (Ag NCs) effectively. In this study, we report for the first time the formation of self-assembled Ag NPs on ct-DNA in the presence of 2-mercaptothioxanthone by photoirradiation technique. TX-SH played two important roles; photoreducing and photostabilizing agent for the formation of Ag NCs on ct-DNA. Fluorophore character of synthesized Ag NPs on DNA may help to develop new techniques for biological and medical aspects. (C) 2017 Elsevier B.V. All rights reserved.Öğe Photophysical, kinetic and thermodynamic study of one-component Type II thioxanthone acetic acid photoinitiators(Pergamon-Elsevier Science Ltd, 2020) Metin, Eyüp; Arsu, Nergis; Çatak, Şaron; Aviyente, ViktoryaIn this study, One-Component Type II thioxanthone acetic acid based photoinitiators, as well as the conventional Type II photoinitiator with phenyl acetic acid based co-initiators, have been investigated in terms of their photophysical, kinetic and thermodynamic properties by a series of Density Functional Theory (DFT) calculations. Experimental UV-Vis spectra have been compared with computationally generated UV-Vis spectra via Time-Dependent DFT (TD-DFT) and by taking into consideration the vibrational and dynamic effects (Wiggler). Natural transition orbitals have been generated for thioxanthone acetic acid derivatives to understand the physical nature of electronic transitions. Furthermore, kinetic and thermodynamic parameters of radical attack to the monomer of thioxanthone acetic acid based radicals and phenyl acetic acid based co-initiator radicals have been investigated. Comparison of the thermodynamic parameters of the initiating radicals has shown that initiation is more favorable with exocyclic radicals in both cases. Exocyclic radicals of the thioxanthone acetic acid derivatives and phenyl acetic acid derivates have been found to have comparable activation energies for their attack to methyl methacrylate. Furthermore, the spin densities and the radical Fukui functions of the attacking radicals have been nicely correlated with the activation barriers. In this way, a fast and predictive approach for the determination of radical reactivity in photopolymerization reactions has been proposed; this enables the evaluation of the initiation efficiency of the photoinitiators prior to synthesis.Öğe Synthesis of one-component type II dithioxanthone-disulfide photoinitiator and investigation of photophysical and photochemical properties(Elsevier, 2021) Koyuncu, Umut; Metin, Eyüp; Öcal, Nüket; Arsu, NergisHerein, we report the successful synthesis of dithioxanthone-disulfide [TX-S-](2) as a new one-component type II photoinitiator. Photophysical properties of [TX-S-](2) in terms of fluorescence and phosphorescence properties were investigated and low fluorescence quantum yield was observed, which indicates an efficient intersystem crossing (ISC) that leads to the generation of triplet states. Efficiently produced initiating thiyl radicals from the triplet states lead to polymerization of methyl methacrylate with [TX-S-](2) in air atmosphere. To elucidate the initiating mechanism, a disulfide exchange reaction was performed in the presence of diphenyl disulfide [Ph-S-](2), and the obtained results from HQ-TOF confirmed that [TX-S-](2) disulfide bond cleavage occurs upon irradiation with light. Initiating mechanism of [TX-S-](2) revealed the potential usage of this compound as a self-healing agent due to the efficient cleavage of disulfide bonds. In conjunction with the experimental studies series of Density Functional Theory calculations were performed and various photophysical and photochemical properties, including HOMO and LUMO, were computationally calculated and visualized.
