Browsing by Subject "Intercalation"
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Item Open Access Benzothiazole derivatives as human DNA topoisomerase IIα inhibitors(2013) Kaplan-Ozen, C.; Tekiner-Gulbas, B.; Foto, E.; Yildiz I.; Diril, N.; Aki, E.; Yalcin I.Benzothiazole derivatives resembling the structure of DNA purine bases were tested to determine their topoisomerase inhibition activities. Based on DNA topoisomerase I and II relaxation assay results, all 12 derivatives acted as human topoisomerase IIα inhibitors, whereas only two compounds inhibited Calf thymus topoisomerase I. 3-amino-2-(2-bromobenzyl)-1,3-benzothiazol-3-ium 4-methylbenzensulfonate (BM3) was observed to be the most effective human topoisomerase IIα inhibitor with the lowest IC50 value of 39 nM. The mechanistic studies suggested that BM3 was neither a DNA intercalator nor a topoisomerase poison, it was only a DNA minor groove-binding agent. BM3 initially bound to the DNA topoisomerase IIα enzyme, then to DNA. As a result, the tested benzothiazole derivatives were obtained as strong topoisomerase IIα inhibitors. The benzothiazole tosylated salt form BM3 was found as the most effective topoisomerase IIα inhibitor. BM3's mechanisms of action might be its direct interaction with the enzyme. BM3's minor groove-binding property might also contribute to this action. Hence, BM3 could be a good candidate as a new anticancer agent. © 2013 Springer Science+Business Media New York.Item Open Access Controlling the photoconductivity: graphene oxide and polyaniline self assembled intercalation(American Institute of Physics Inc., 2015) Vempati S.; Ozcan, S.; Uyar, TamerWe report on controlling the optoelectronic properties of self-assembled intercalating compound of graphene oxide (GO) and HCl doped polyaniline (PANI). Optical emission and X-ray diffraction studies revealed a secondary doping phenomenon of PANI with -OH and -COOH groups of GO, which essentially arbitrate the intercalation. A control on the polarity and the magnitude of the photoresponse (PR) is harnessed by manipulating the weight ratios of PANI to GO (viz., 1:1.5 and 1:2.2 are abbreviated as PG1.5 and PG2.2, respectively), where ±PR = 100(RDark - RUV-Vis)/RDark and R corresponds to the resistance of the device in dark or UV-Vis illumination. To be precise, the PR from GO, PANI, PG1.5, and PG2.2 are +34%, -111%, -51%, and +58%, respectively.Item Open Access Graphene-enabled optoelectronics on paper(American Chemical Society, 2016-06) Polat, E. O.; Uzlu, H. B.; Balci, O.; Kakenov, N.; Kovalska, E.; Kocabas, C.The realization of optoelectronic devices on paper has been an outstanding challenge due to the large surface roughness and incompatible nature of paper with optical materials. Here, we demonstrate a new class of optoelectronic devices on a piece of printing paper using graphene as an electrically reconfigurable optical medium. Our approach relies on electro-modulation of optical properties of multilayer graphene on paper via blocking the interband electronic transitions. The paper based devices yield high optical contrast in the visible spectrum with a fast response. Pattering graphene into multiple pixels, folding paper into three-dimensional shapes or printing colored ink on paper substrates enable us to demonstrate novel optoelectronic devices which cannot be realized with wafer-based techniques.Item Open Access Poly(epsilon caprolactone)/clay nanocomposites via host-guest chemistry(Elsevier Ltd, 2015) Arslan, M.; Tasdelen, M. A.; Uyar, Tamer; Yagci, Y.Cyclodextrin-modified montmorillonite (MMT-CD) has been prepared from commercial montmorillonite clay (Closite 30B) containing two hydroxyl groups by reacting succinic anhydride through esterification. Poly(epsilon caprolactone) (PCL)/clay nanocomposites are prepared by host-guest chemistry between MMT-CD as host and PCL, hydrophobic polymer as guest. The structures of the intermediates and final nanocomposite are investigated in detail by FT-IR XRD, TEM, DSC and TGA measurements. The intercalated/exfoliated morphologies are determined by combined XRD and TEM analyses. Thermal stabilities of all nanocomposites are improved by the addition of MMT-CD compared to the neat polymer. The DSC data confirm that the crystallinity of PCL is slightly increased by increasing clay loading. © 2015 Elsevier Ltd. All rights reserved.