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Öğe A calix[4]arene derivative-doped perchlorate-selective membrane electrodes with/without multi-walled carbon nanotubes(SPRINGER HEIDELBERG, 2017) Erturun, H. Elif Kormali; Özel, Ayça Demirel; Ayanoğlu, Melek Nur; Şahin, Özlem; Yılmaz, MustafaIn this study, poly (vinyl chloride)(PVC) membrane electrodes with/without multi-walled carbon nanotubes (MWCNTs) based on a calix[4]arene derivative for perchlorate ion were described. The influence of membrane composition, pH, conditioning solution on the potentiometric response of the electrodes was investigated. Perchlorate-selective PVC membrane electrode exhibited a slope of 47.8 +/- 0.6 mV/pClO(4) in the range of 1.0 x 10(-7)-1.0 x 10(-1) mol L-1 at pH 4.0 while the coated Pt electrodes with MWCNT-OH, MWCNT-COOH and MWCNT displayed slopes of 46.1 +/- 0.7 mV/pClO(4) (5.0 x 10(-6)-1.0 x 10(-1) mol L-1), 50.4 +/- 1.9 mV/pClO(4) (1.0 x 10(-6)-1.0 x 10(-1) mol L-1) and 44.4 +/- 0.3 mV/pClO(4) (1.0 x 10(-5)-1.0 x 10(-1) mol L-1), respectively. Other response characteristics of these electrodes such as response time, lifetime and detection limit were identified, and the selectivity coefficients towards various anions were calculated by separate solution method. Moreover, the perchlorate-selective electrodes described here were successfully used as an indicator electrode for the determination of perchlorate in real samples such as tap water, river water and human urine by direct calibration method.Öğe Calixarene-proline functionalized iron oxide magnetite nanoparticles (Calix-Pro-MN): An efficient recyclable organocatalyst for asymmetric aldol reaction in water(ELSEVIER SCIENCE BV, 2015) Akceylan, Ezgi; Uyanık, Arzu; Eymur, Serkan; Şahin, Özlem; Yılmaz, MustafaCalix[4]arene-based chiral organocatalyst derived from L-proline supported onto well-defined (15 +/- 3 nm) magnetic Fe3O4 nanoparticles was used as a highly active, recoverable, and reusable catalyst for the asymmetric aldol reaction in water without need for organic solvents. The chiral organocatalyst showed high catalytic activity (up to 94%), enantioselectivity (up to 93%) and diastereoselectivity (up to 97:3) for the reaction between cyclohexanone and aromatic aldehydes. The catalyst could easily separated using an external magnetic field and reused for several times without any significant loss of activity. (C) 2015 Elsevier B.V. All rights reserved.Öğe Chiral Calix[4]arenes-Bearing Prolinamide Functionality as Organocatalyst for Asymmetric Direct Aldol Reactions in Water(TAYLOR & FRANCIS LTD, 2018) Şahin, Özlem; Eymur, Serkan; Uyanık, Arzu; Akceylan, Ezgi; Yılmaz, MustafaThe chiral calix[4]arene derivative (6) bearing an L-prolinamido group has been designed and proved to be a water compatible efficient organocatalysts for a direct enantioselective aldol reaction. Compound 6 catalyzes the aldol reaction of cyclohexanone and a variety of aromatic aldehydes yielding anti-aldol products in high yield with enantioselectivities of up to 93% and diastereoselectivity of up to 95:5.Öğe Direct enantioselective aldol reactions catalyzed by calix[4]arene-based L-proline derivatives in the water(PERGAMON-ELSEVIER SCIENCE LTD, 2014) Eymur, Serkan; Akceylan, Ezgi; Şahin, Özlem; Uyanık, Arzu; Yılmaz, MustafaTwo novel p-tert-butylcalix[4]arene-based chiral organocatalysts derived from L-proline have been developed to catalyze direct aldol reactions between cyclohexanone and aromatic aldehydes in water. Under the optimal conditions, high yields (up to 95%), enantioselectivities (up to 90%), and moderate diastereoselectivities (up to 65:35) were obtained. Considering the catalytic inefficiency of sole proline for the aldol reaction in water, these results clearly display the enormous effect of the hydrophobic part of calix[4]arene of compound A. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Diyabetik retinopati tedavisinde çok noktalı lazerlerin konvansiyonel lazerler ile etkinlik ve yan etkiler yönünden karşılaştırılması(2017) Çeliker, Hande; Bulut, Azer Erdağı; Şahin, ÖzlemPanretinal fotokoagülasyon (PRF), proliferatif diyabetik retinopati tedavisinde standart tedavidir. Konvansiyonel lazer (KL) ile tedavi, teknokta modunda bir veya daha fazla seansta gerçekleştirilir. KL sonrası maküler ödem gelişmesi nedeniyle, santral görme kaybı, genişleyeniç retinal skar dokusu nedeniyle periferal görme alanı kayıpları rapor edilmiştir. Çok odaklı lazer [multispot lazer (MSL)] fotokoagülasyonson yıllarda klinik uygulamaya girmiştir. Yapılan çalışmalarda; PRF uygulamalarında MSL ile KL karşılaştırıldığında, MSL ile dahaaz retinal doku hasarı, daha az ağrı ve artan hasta konforu bildirilmiştir. Bu çalışmanın amacı, diyabetik retinopati tedavisinde MSL veKL’lerin, etkinliği ve yan etkilerini karşılaştırmaktır.Öğe Does Treatment with Somatostatin Analogs Affect the Radioactivite Uptake of Normal Target Organs and Malignant Lesions on 68GaDOTATATE PET/CT imaging?(Selçuk Üniversitesi, 2022) Şahin, Özlem; Erol, Çağlagül; Yılmaz, Farise; Önner, Hasan; Gedik, Gonca Kara; Çelik, Ahmet VolkanObjective: Somatostatin analogs (SSA) are used in treating low-grade neuroendocrine tumors (NET), mainly because of their antiproliferative effect. 68Ga tetraazacyclododecantetraacetic acid-DPhe1-Tyr3-octreotate (DOTATATE) PET/CT as somatostatin receptor imaging has been widely used in recent years. However, there are conflicting publications in the literature, although there are guidelines for discontinuing the use of SSA before imaging. This study aims to investigate the effect of SSAs on Somatostatin receptor imaging. Material and Method: We retrospectively analyzed 253 patients who underwent 68Ga-DOTATATE PET/CT imaging between 2018 and 2022. Among these patients, those with low grades (grade 1 and grade 2) using SSA were included in the study. SUVmax (maximum standard uptake volume) of normal target organs, primary tumors, and metastases with the highest SUVmax in each organ were compared before and after SSA treatment. Results: 28 patients (16 females; 12 males, age [mean±SD], 54.82±14.27, range 18-78) with low-grade NET and 68Ga-DOTATATE PET/CT imaging with SSA therapy were included in the study. Although SUVmax was decreased in the values measured after SSA application in the liver and spleen, it was not statistically significant (p>0.05). There was no significant difference between SUVmax values in primary tumors and metastatic lesions in the liver, bone, lung, or lymph nodes before and after SSA application (P> 0.05). Conclusion: In conclusion, these drugs do not need to be discontinued before 68Ga-DOTATATE PET/CT imaging for treatment follow-up in neuroendocrine tumor patients using SSAs. In addition, these drugs may help report interpretation by increasing the intensity of metastatic lesions in the liver and spleen.Öğe Effect of the glutaraldehyde derivatives of Calix[n]arene as cross-linker reagents on lipase immobilization(SPRINGER, 2009) Erdemir, Serkan; Şahin, Özlem; Uyanık, Arzu; Yılmaz, MustafaSynthesis of the glutaraldehyde derivatives calix[n]arene (n = 4,6,8) (Calix[n]-GA) and using as cross-linkers for immobilization of Candida rugosa lipase (CRL) have been discussed in this paper. The amino functional calix[n]arene derivatives (Calix[n]-NH (2)) were synthesized via reduction of dinitrile, hexanitrile and octanitrile derivatives of calix[n]arenes. These amino functional calix[n]arene derivatives (Calix[n]-NH (2)) were converted to their aldehyde derivativatives with glutaraldehyde. The calix[n]arene derivatives were used in lipase immobilization in order to see the role of calix[n]arene binding site on the lipase activitiy and stability. The activity recovery of calix[n]arene-supported lipases (Calix[n]-CRL) based on the Calix[4]-CRL, Calix[6]-CRL and Calix[8]-CRL reaches to 53.5, 66.1 and 76.4%, respectively.Öğe Electrocatalytic properties of nanostructured multimetallic Pt-SnCs/C AND Pt-M/C (M=Ag, Ca, Cd, Cs, Cu, Fe, Ir, Mg, Pd, Sn, Zr) direct ethanol fuel cell catalysts(Selçuk Üniversitesi Mühendislik Fakültesi, 2013) Kıvrak, Hilal; Demir, N. Ceyhun; Şahin, ÖzlemCarbon supported Pt and Pt-M (M=Ag, Ca, Cd, Cs, Cu, Fe, Ir, Mg, Pd, Sn, Zr) bimetallic nanocatalysts (10% Pt loading) and Pt-Sn-Cs trimetallic nanocatalysts were prepared by ethylene glycol (EG) reduction method. The ethanol electrooxidation (EOR) performance of these catalysts were studied by cyclic voltammetry (CV), chronoamperometry (CA), electrochemical impedance spectroscopy (EIS) techniques. Considering Pt-M bimetallic nanocatalysts, carbon supported Pt-Sn bimetallic nanocatalyst showed the best EOR activity as a result of these CV, CA, EIS measurements. Furthermore, Cs promoted Pt bimetallic nanocatalyst also improved the activity of reverse current, attributed to the basic character of Cs. Pt-Sn nanocatalyst was promoted by Cs to neutralize the surface acid sites of the Pt-Sn nanocatalyst. Pt-Sn-Cs/C nanocatalyst showed the superior activity compared to Pt-Sn nanocatalysts. Hence, we further performed EIS measurements on Pt-Sn-Cs, Pt-Sn, Pt-Cs nanocatalysts to compare their electrocatalytic activities.Öğe Enantioselective hydrolysis of (R,S)-Naproxen methyl ester using Candida rugosa lipase with calix[4]arene derivatives(SPRINGER, 2015) Akceylan, Ezgi; Aköz, Enise; Şahin, Özlem; Yılmaz, MustafaCandida rugosa lipase has been immobilized on a variety of calix[4] arene derivatives using the sol-gel encapsulation technique, and the catalytic activities of the resulting encapsulated lipases towards the hydrolysis of p-nitrophenyl palmitate and the hydrolytic kinetic resolution of racemic Naproxen methyl ester were evaluated using standard techniques. The results revealed that the calix[4]arene- based immobilized encapsulated lipases 5-CRL and 6-CRL gave higher levels of enantioselectivity and conversion than the free encapsulated lipase.Öğe Enantioselective hydrolysis of (R/S)-Naproxen methyl ester with sol-gel encapculated lipase in presence of calix[n]arene derivatives(ELSEVIER SCIENCE BV, 2009) Şahin, Özlem; Erdemir, Serkan; Uyanık, Arzu; Yılmaz, MustafaLipases are enzymes that catalyses a variety of reactions, such esterifications, interesterification and hydrolysis. Several methods have been reported for the immobilization of lipases, such as deposition onto solid supports, covalent binding and encapsulation within a polymer matrix or silica glasses obtained by sol-gel techniques. In this study, the Candido rugosa lipase was encapsulated within a chemically inert sol-gel support prepared by polycondensation by tetraetoxysilane (TEOS)and octyltrietoxysilane(OTES) in the presence and absence of calix[n]arene, calix[n]-NH2 and calix[n]-COOH (n = 4,6,8) compounds as additives. The catalytic activity of the encapsulated lipases was evaluated into model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate (p-NPP), and the enantioselective hydrolysis of rasemic Naproxen methyl ester that was studied in aqueous buffer solution/isooctane reaction system. The results indicated that the particularly calix[4,6]-NH2 and calix[6]-COOH based encapsulated lipases had higher conversion and enantioselectivity compared to the sol-gel free lipase. (C) 2009 Elsevier B.V. All rights reserved.Öğe Findings on fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography in a patient with malignant pheochromocytoma(2011) Özcan, Pelin Kara; Kara, Taylan; Kara, Gonca Gedik; Sarı, Oktay; Şahin, ÖzlemFeokromasitomalar sempatoadrenal sistemin kromafin hücrelerinden köken alan nadir tümörlerdir ve %85’i adrenal medullada lokalize olur. Malign feokromasitomalar tüm feokromasitomaların %10’unu oluşturur. Klinik, biyokimyasal ve histopatolojik yöntemlerin hiçbiri malign tümörleri benign tümörlerden ayıramadığından, malignite uzak metastaz varlığında tanımlanır. Her ne kadar bazı vakalarda metastazlar takip sırasında gelişebilirse de, vakaların büyük çoğunluğunda ilk tanı anında metastatik hastalık mevcuttur. Bu olgu sunumunda, malign feokromasitomalı bir hastada takip sırasında rekürens ve uzak metastazlarının 18-florodeoksiglukoz pozitron emisyon tomografi/ bilgisayarlı tomografi (FDG PET/BT ) ile saptanması sunulmuştur. (MIRT 2011;20:67-69)Öğe Floresans özellik gösteren kaliks[4]aren türevlerinin sentezi, karakterizasyonu ve bazı özelliklerinin incelenmesi(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2011-06-23) Şahin, Özlem; Yılmaz, MustafaSupramoleküler kimyada büyük yeri olan kaliksarenler bu alandaki diğer moleküllere kıyasla kolay sentezlenebilmeleri ve kolay fonksiyonlandırılabilmeleri sebebi ile sentetik organik kimyada en çok dikkat çeken makrosiklik bileşikler olmuşlardır. Kaliksarenler fenolik -O üzerinden ve ter-bütil grupları dealkilasyonla giderildikten sonra aromatik birimlerin p-pozisyonundan fonksiyonlandırılarak anyon, katyon ve nötral moleküller için reseptör olarak kullanılabilirler. Bu çalışmada piren, naftalin ve naftilimid grupları taşıyan kaliks[4]arenler türevleri sentezlendi. Sentezlenen bu bileşiklerin yapıları spektroskopik teknikler (FTIR, 1H NMR, 13C NMR, COSY) ile aydınlatıldı. Bu kaliks[4]aren türevlerinin bazı metal katyonları (Na+, Li+, Mg+2, Ni+2, Ba+2, Ca+2, Cu+2, Ca+2 , Pb+2, Zn+2) ve anyonlarına (F-, Cl-, Br-, H2PO4-, NO3-, I- , HSO4-, CH3COO-) karşı floresans özellikleri UV-Vis., NMR ve floresans spektroskopik teknikleri kullanılarak incelendi. Piren amin türevli kaliks[4]arenin Pb+2 ve Cu+2 iyonlarına karşı floresans sensör olarak, piren imin türevli kaliks[4]arenlerin Pb+2, Mg+2 ve Cu+2 iyonlarına karşı floresans sensörü olarak ve naftilimid türevli kaliks[4]arenlerin ise Cu+2 ve F- iyonlarına karşı floresans sensör olarak davrandığı gözlendi.Öğe Improvement of catalytic activity of lipase in the presence of wide rim substituted calix[4]arene carboxylic acid-grafted magnetic nanoparticles(SPRINGER, 2014) Akceylan, Ezgi; Şahin, Özlem; Yılmaz, MustafaCandida rugosa lipase immobilized on calix[4] arene carboxylic acid-grafted magnetic nanoparticles using a sol-gel encapsulation technique was tested for activity, which was assessed both in the enantioselective hydrolysis of racemic Naproxen methyl ester and that of p-nitrophenylpalmitate. It has also been noticed that, compared to the free enzyme (E = 137) with an ee value of [98 %, S-Naproxen calix[4] arene carboxylic acid-grafted magnetic nanoparticles based on encapsulated lipase (Calix-1-MN and Calix-2-MN) offer excellent enantioselectivity (E = 373 and E = 381). Moreover, the results indicated that after the fifth reuse in the enantioselective reaction, the encapsulated lipase (Calix-2-MN) still retained about 43 % of its conversion power.Öğe A new anthracene derivative of calix[4]arene as a fluorescent chemosensor(SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2013) Şahin, Özlem; Şahin, Mustafa; Koçak, Nuriye; Yılmaz, MustafaA new anthracene derivative of calix[4]arene was synthesized as a highly fluorescent compound. This compound was examined for its fluorescent properties towards different metal ions (Li+, Na+, Mg2+, Ca2+, Ba2+, Ni2+, Cu2+, Zn-2+, Pb2+) by UV and fluorescence spectroscopy. On complexation by alkaline earth metal cations and transition metal cations, the fluorescence spectrum was quenched. In particular, Ca2 + caused greater than 98% quenching of the anthracene derivative of calix[4] arene.Öğe Salicylate Ion-Selective Electrode Based on a Calix[4]arene as Ionophore(WILEY-V C H VERLAG GMBH, 2015) Ayanoğlu, Melek Nur; Erturun, H. Elif Kormali; Özel, Ayça Demirel; Şahin, Özlem; Yılmaz, Mustafa; Kılıç, EsmaA salicylate-selective electrode based on calix[4]arene derivative was developed and its response characteristics were investigated. The optimum membrane composition was 1% ionophore, 30% PVC, 69% DOS. The electrode exhibited a Nernstian slope of 58.8 +/- 0.5mV/pSal in the range of 1.0x10(-5)-1.0x10(-1)M with a detection limit of 4.3x10(-6)M at pH4.0, 20 +/- 1 degrees C. The potentiometric response of the electrode in the presence of different anions was investigated by the separate solution method. The lifetime was found at least 4months, and its response time was 5-10s. It was successfully used for the potentiometric determination of salicylate in pharmaceutical preparations.Öğe Synthesis and characterization of novel Ti doped hexagonal mesoporous silica catalyst for nonenzymatic hydrogen peroxide oxidation(ELSEVIER SCIENCE BV, 2018) Düzenli, Derya; Şahin, Özlem; Kazıcı, Hilal Çelik; Aktaş, Nahit; Kıvrak, HilalA new electrocatalyst, Ti-HMS was successfully synthesized by sol-gel method employing Ti source tetrabutyl orthotitanate (TBOT) and silica source tetraethyl orthosilicate (TEOS, 99% purity). Ti-HMS catalysts were prepared at varying Ti:Si ratios by employing sol-gel method. Physicochemical properties of these nanoparticles were characterized and confirmed by BET, TG-DTA, XPS, and XRD. Electrochemical properties of Ti-HMS catalysts prepared at varying Ti:Si ratios were examined by cyclic voltammetry (CV) and chronoamperometry (CA) for determination of the oxidation and reduction activity of H2O2. It was observed that the Ti-HMS (Ti:Si = 0.02) electrode exhibits significant oxidation and reduction of H2O2 at applied potentials of 0.65 V and -0.30 V with the addition of H2O2, respectively. The excellent electrocatalytic response to H2O2 is mainly attributed to varying electronic properties with the incorporation of Ti to HMS. (C) 2017 Elsevier Inc. All rights reserved.Öğe Synthesis and Dichromate Anion Extraction Ability of Calix[4]arene Schiff Base Derivatives(TAYLOR & FRANCIS INC, 2014) Şahin, Özlem; Şahin, Mustafa; Yılmaz, Mustafa[Abstract not Available]Öğe Synthesis and fluorescence sensing properties of a new naphthalimide derivative of calix[4]arene(PERGAMON-ELSEVIER SCIENCE LTD, 2012) Şahin, Özlem; Yılmaz, MustafaA new naphthalimide derivative of calix[4]arene was synthesized as a highly selective fluorescent compound for Cu2+ among the selected metal ions. This compound was examined for its fluorescent properties toward different metal ions (Na+, Li+, Mg2+, Ni2+, Ba2+, Ca2+, Cu2+, Pb2+, Zn2+) and anions (F-, Cl-, Br-, H2PO4-, NO3-, HSO4-, CH3COO-) by UV, NMR and fluorescence spectroscopy. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Synthesis and fluorescence sensing properties of novel pyrene-armed calix[4] arene derivatives(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Şahin, Özlem; Yılmaz, MustafaFluorogenic tert-butylcalix[4]arenes bearing two pyrene pendant groups at the lower rim were synthesized. Based on ratiometric changes of monomer and excimer emissions, the pyrene amine derivative of calix[4]arene has been found to act as a selective sensor for Pb2+ and Cu2+ ions, respectively, due to a conformational change upon chelation of these ions. (c) 2011 Elsevier Ltd. All rights reserved.Öğe Synthesis of a glutaraldehyde derivative of calix[4]arene as a cross-linker reagent for lipase immobilization(SPRINGER, 2009) Özcan, Fatih; Şahin, Özlem; Yılmaz, MustafaThis article describes the synthesis of a new calix[4]arene 1,3-distal glutaraldehyde derivative 4 as a cross-linker-reagent for immobilization of Candida rugosa lipase (CRL). p-tert-Butylcalix[4]arene 1,3-distal diaminoalkyl derivative (3) synthesized via aminolysis reaction of 5,11,17,23-tert-butyl-25,27-ethoxycarbonylmethoxy-26,28-hydroxycalix[4]arene (2) with 1,8-diaminooctane. Compound 3 was converted to its aldehyde derivative (4) by the treatment with glutaraldehyde solution. 4 was used in lipase immobilization in order to see the role of calix[4]arene binding site on the lipase activity and stability. It was observed that the immobilized lipase activity was maintained at levels exceeding 95% of its original activity after 40 min.
