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    A magnetically separable biocatalyst for resolution of racemic naproxen methyl ester
    (SPRINGER, 2013) Ozyilmaz, Elif; Sayin, Serkan
    Candida rugosa lipase (CRL) was encapsulated via the sol-gel method, using 5, 11, 17, 23-tetra-tert-butyl-25,27-bis(2-aminopyridine)carbonylmethoxy-26, 28-dihydroxy-calix[4]arene-grafted magnetic Fe3O4 nanoparticles (Calix-M-E). The catalytic activity of encapsulated lipase (Calix-M-E) was tested both in the hydrolysis of p-nitrophenyl palmitate (p-NPP) and the enantioselective hydrolysis of racemic naproxen methyl ester. The present study demonstrated that the calixarene-based compound has the potential to enhance both reaction rate and enantioselectivity of the lipase-catalyzed hydrolysis of racemic naproxen methyl ester. The encapsulated lipase (Calix-M-E) had great catalytic activity and enantioselectivity (E > 400), as well as remarkable reusability as compared to the encapsulated lipase without supports (E = 137) for S-Naproxen.
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    Photoelectrochemical Biosensing Approach for Alcohol Determination by "Wiring" of Alcohol Oxidase Photonically with P(SNS-NH2)/AOx/CNT/[Ru(bpy)(3)](2+) Modified Electrodes
    (TAYLOR & FRANCIS INC, 2014) Yildiz, H. B.; Kamaci, Musa; Karaman, Mustafa; Toppare, Levent; Sayin, Serkan
    A photoelectrochemical alcohol biosensor was designed through photonic wiring of alcohol oxidase (AOx) onto conducting polymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine (SNS-NH2) and carbon nanotubes (CNTs) modified gold slides. The photoelectrochemical biosensors utilize a photonically wired electrode that oxidizes primary alcohols to aldehydes. Three different alcohols namely methanol, ethanol, and n-propanol were used as the substrates. In the presence of different concentrations of primary alcohol, the photocurrents were obtained by irradiating of the photoelectrochemical cell containing P(SNS-NH2)/AOx/CNT/[Ru(bpy)(3)](2+) electrode as the anode under air. The bipyridine complex [Ru(bpy)(3)](2+) was used to activate photoinduced electron-transfer reaction and it acted as a redox mediator to activate the bioelectrocatalytic functions of AOx. Therefore, it was shown the photonic electron-transfer wiring of AOx with the electrode. Sensitivity experiments, optimum pH value, operational stabilization and shelf life of the photoelectrochemical biosensor were investigated. Finally, the photoelectrochemical biosensors were used for alcohol detection in real samples.
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    Preparation of New Calix[4]arene-Immobilized Biopolymers for Enhancing Catalytic Properties of Candida rugosa Lipase by Sol-Gel Encapsulation
    (SPRINGER, 2013) Ozyilmaz, Elif; Sayin, Serkan
    The article describes preparation of new calixarene biopolymers consisting of the immobilization of convenience calixarene derivative onto cellulose and chitosan biopolymers, and the encapsulation of these calixarene biopolymers with Candida rugosa lipase within a chemical inert sol-gel supported by polycondensation with tetraethoxysilane and octyltriethoxysilane. The catalytic properties of immobilized lipase were evaluated into model reactions employing the hydrolysis of p-nitrophenylpalmitate and the enantioselective hydrolysis of naproxen methyl esters from racemic prodrugs in aqueous buffer solution/isooctane reaction system. The resolution studies using sol-gel support have observed more improvement in the enantioselectivity of naproxen E = 300 with Cel-Calix-E than with encapsulated lipase without calixarene-based materials. Furthermore, the encapsulated lipase (Cel-Calix-E) was still retained about 39 % of their conversion ratios after the fifth reuse in the enantioselective reaction.
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    Synthesis and properties of novel magnetic nanoparticles grafted with nitropyridine-substituted calix[4]arene derivative as Cr6+ extractant
    (SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2015) Sayin, Serkan; Dogan, Vildan
    A new calix[4]arene derivative, 3, which functionalized at the lower rim with 2-(2-aminoethyl amino)-5-nitropyridine, was synthesized and characterized by a combination of FTIR, H-1 NMR, C-13 NMR, and elemental analysis. Then the calix[4]arene 3 was grafted onto [3-(2,3-epoxypropoxy)propylltrimethoxysilane-modified Fe3O4- nanoparticles (EPPTMS-MN) to produce new calixarene-adorned magnetic nanoparticles (MN-DiNoPy-Calix (4)). The structure of the calixarene-adorned magnetic nanoparticles 4 was determined by a combination of FTIR, TEM, and elemental analysis. Moreover, a study regarding the removal of toxic HCr2O7- anion from aqueous solution was also carried out with the calixarene-adorned magnetic nanoparticles in solid liquid extraction studies.
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    Utilization of Catalytic Properties of the Encapsulated Lipase with Calix[4]arene-Adorned Sporopollenin
    (TAYLOR & FRANCIS LTD, 2018) Ozyilmaz, Elif; Sayin, Serkan
    The dihydrazide calix[4]arene was immobilized onto sporopollenin in order to encapsulate Candida rugosa lipase (CRL) via sol-gel entrapment. The kinetic resolution of the new encapsulated lipase was investigated for enantioselective hydrolysis of racemic naproxen methyl ester and 2-phenoxypropionic acid methyl ester. The results demonstrated that the activity and enantioselectivity of the lipase were improved when the lipase was encapsulated in the presence of calix[4]arene-immobilized sporopollenin. The encapsulated lipase showed an excellent rate of enantioselectivity against the (R/S)-naproxen methyl and (R/S)-2-phenoxypropionic acid methyl esters, with E = 350 and 295, respectively, compared to the free enzyme.