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    Covalent Immobilization of Candida rugosa Lipase on Epichlorohydrin-Coated Magnetite Nanoparticles: Enantioselective Hydrolysis Studies of Some Racemic Esters and HPLC Analysis
    (Springer, 2020) Cakmak, Resit; Topal, Giray; Cinar, Ercan
    In this study, a new biocatalyst was prepared by immobilizing Candida rugosa lipase epichlorohydrin-functionalized onto the surface of the nanoparticles. Magnetite nanoparticles were obtained by chemical co-precipitation method of Fe2+ and Fe3+, and then the prepared uncoated and coated nanoparticles were characterized by XRD, FT-IR and TGA. Lipase was covalently attached to activated nanoparticles. The catalytic properties of free and immobilized lipases were determined. It was found that the optimum temperature for free and immobilized lipases was 30 degrees C and 35 degrees C, respectively. The optimum pH values were found to be 7.0 and 8 for free and immobilized lipases, respectively. Immobilized lipase was found to retain significant activity even after the seventh use. In the final section of the study, optically pure compounds were obtained by carrying out the enantioselective hydrolysis studies of racemic esters by using immobilized lipase. Enantiomeric excesses of the products in the enantioselective hydrolysis of racemic ibuprofen and naproxen methyl ester and racemic butyl mandelate were determined to be 94.93, 77.30 and 68.15, respectively.
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    Design, preparation and application of a Pirkle-type chiral stationary phase for enantioseparation of some racemic organic acids and molecular dynamics studies
    (Acg Publications, 2017) Cakmak, Resit; Ercan, Selami; Sunkur, Murat; Yilmaz, Hayrullah; Topal, Giray
    This study consists of two parts. In the first part of the study; a Pirkle-type chiral stationary phase was prepared by synthesizing an aromatic amine derivative of (R)-2-amino-1-butanol as a chiral selector and binding to L-tyrosine-modified cyanogen bromide (CNBr)-activated Sepharose 4B and then, packed into the separation column. The chromatographic performance of the separation column was evaluated with racemic mandelic acid and 2-phenylpropionic acid by using phosphate buffers at three different pHs as mobile phase. In the resolution processes, the prepared solutions were loaded onto the separation column at two different concentrations and at three different pHs for each racemic organic acid, separately. Enantiomeric excess (ee%) of the eluates was determined on CHIRALPAK AD-H chiral analytical column by HPLC. The maximum ee% for mandelic acid and 2-phenylpropionic acid was determined to be 60.84 and 27.4, respectively. Separation factors (k(1)', k(2)', alpha, and Rs) were calculated for each acid. The structures of the obtained compounds were characterized using the spectroscopic methods (NMR, and elemental analysis). In the second part of the study; enantioselective interactions between the prepared CSP and the analytes have been widely studied by docking, molecular dynamics simulation and quantum mechanical computation methods. The reason of column eluation of rac-2-phenylpropionic acid with lower enantiomeric yield was explained by these techniques.
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    Öğe
    Design, synthesis and biological evaluation of novel nitroaromatic compounds as potent glutathione reductase inhibitors
    (Pergamon-Elsevier Science Ltd, 2011) Cakmak, Resit; Durdagi, Serdar; Ekinci, Deniz; Senturk, Murat; Topal, Giray
    Discovery of GR inhibitors has become very popular recently due to antimalarial and anticancer activities. In this study, the synthesis and GR inhibitory capacities of novel nitroaromatic compounds (NCs) (1-3) were reported. Some commercially available molecules were also tested for comparison reasons. The novel NCs were obtained in high yields using simple chemical procedures and exhibited much potent inhibitory activities against GR at low micromolar concentrations with K-i values ranging from 0.211 to 4.57 mu M as compared with well-known agents. Inhibition mechanism was assessed as being due to occlusion of the active site entrance by means of the NCs. Molecular docking results have shown that docking poses of ligands are able to construct binding interactions with the essential amino acids. (C) 2011 Elsevier Ltd. All rights reserved.
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    Öğe
    Design, synthesis, structural characterization, in vitro anticancer activity, and in silico studies of some new hydroxylated and fluorinated-substituted hydrazone derivatives
    (2025) Cakmak, Resit; Basaran, Eyup; Erdogan, Omer; Mali, Suraj N.; Kopru, Semiha; Yasin, Haya; Gurav, Shailesh S.
    Today, due to improved lifestyles and increased survival, the number of new cancer cases and cancer-related deaths continues to increase. In this study, novel hydroxylated and fluorinated-substituted hydrazone derivatives bearing an aromatic nitro moiety (2a-d and 3a-d) were designed as potential anticancer drug candidates, synthesized for the first time, and evaluated for their anticancer activity against chondrosarcoma (SW1353), a common primary malignant cartilage-forming tumor, neuroblastoma (SH-SY5Y), a type of brain cancer, and healthy (L929) cell lines using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method for 24 h. The chemical structures of the target molecules were confirmed by FT-IR, 1D NMR (1Hand 13C- NMR, and APT), 2D NMR (COSY, HETCOR, and HMBC), and elemental analysis. Some of the compounds targeted against these cancer cell lines showed activity greater than 200 mu M, whereas others (2d and 3a) demonstrated significant cytotoxic activity. Among them, compound 3a (IC50 = 9.45 +/- 2.14 mu M), a fluorinatedsubstituted hydrazone derivative, showed significant cytotoxic activity against the human SW1353 cell line compared to cisplatin (IC50 = 11.9 +/- 0.95 mu M). The anti-migratory properties of compounds 2d and 3a in SW1353 cells, were investigated. In particular, compound 3a exhibited anti-migration behavior in SW1353 cells, with a wound closure rate of 22.25 % compared with control cells. Further, scaffolds 2d and 3a exhibited the best docking with target receptor proteins 2OH4 (-8.3 and -8.4 kcal/mol) and 3QX3 (-12.2 and 11.0 kcal/mol), thereby supporting our bioactivity studies. Compounds 2a, 3a, 3b, and 3c showed high gastrointestinal (GI) absorption, with all except 3a being non-permeable to the blood-brain barrier (BBB). Most compounds, except 3d, are non-substrates of P-glycoprotein (P-gp). In conclusion, the in vitro and in silico results of some of the tested compounds indicate that they could be promising molecular frameworks for further studies.