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Öğe Electrospun graphene-cellulose acetate/paulschulzia pseudovolvox (algae) modified photoelectrodes generating electricity via harnessing solar energy: a novel biosensing design for photoelectrochemical pesticide detection via photosynthesis inhibition(Elsevier Ltd, 2025) Büyükharman, Mustafa; Ashurov, Nurbek; Atakhanov, Abdumutolib; Vardar, Deniz Özkan; Azak, Hacer; Yıldız, Hüseyin BekirThis article explores the possibility of biophotovoltaic devices (BPVs) as a sustainable solution to the global energy issue and climate change mitigation. BPVs produce renewable power by harnessing sunshine and water, employing the photosynthetic processes of biological photocatalysts such as green algae and cyanobacteria. Carbon-based electrodes, particularly graphene (Gr), are distinguished as advantageous alternatives owing to their affordability, electrical conductivity, and mechanical robustness. While reduced graphene oxide is frequently utilized, non-oxidized graphene has not been extensively studied until recent researches emphasized its remarkable current-harvesting abilities. Moreover, one-dimensional structured nanomaterials, such as electrospun nanofibers, present opportunities for enhancing electron transit and augmenting charge collecting efficiency. A novel photoanode design has been developed, using Paulschulzia pseudovolvox sp. (green algae) immobilized on a graphene-cellulose acetate electrospun matrix. This mat offers a porous structure that facilitates suitable algal attachment and effective electron transfer. The cathode is linked to a gold electrode surface coated with Poly (4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzamine), P(SNS-NH2) electrochemically, on which the bilirubin oxidase (BOx) enzyme gets immobilized via glutaraldehyde activation. The algae-based system employs light to oxidize and dissociate water at the photoanode, producing oxygen. At the same time oxygen is converted to water at the cathode through bioelectrocatalysis. Optimizations were carried out to improve electron transport and promote electron transfer, hence achieving high photocurrent. Under optimal conditions, the BPV attained a peak power output of 55.2 mW/m² at a steady state with a current density of 125 mA/m². In addition to conversion of light energy to electricity, the system was applied as a pesticide biosensor. The BPV system effectively detected atrazine and diuron, with analytical characterisation performed for atrazine within the 0.1–1.2 μM range and diuron within the 0.01–0.15 μM range. The detection limits were significantly low, measuring 7.5 nM for atrazine and 0.29 nM for diuron. Furthermore, recovery studies were also performed to evaluate the pesticide biosensor capabilities of BPV. © 2025 Elsevier LtdÖğe Acquiring stereospecific new pseudosugars: Obtaining rac-decahydro-1,4-epoxynaphthalene-2,3,5,6,7,8-hexaols from the Diels-Alder reaction and investigating their biological effects(Academic Press Inc., 2025) Aydın, Gökay; Çoban, Canan Çakır; Kurbanoğlu, N.İzzet; Türk, Mustafa; Baran, ArifIn this study, Diels–Alder reaction was performed to sulfolene and endo/exo-diacetate compounds. After a series of reactions, new conduritol A and F analogs containing oxo-bridge and naphthalene rings in their structures were synthesized. To the starting compound, bromination, elimination, singlet oxygen reaction, acetylation, selective oxidation with osmium tetroxide (OsO4), and m-chloroperbenzoic acid (m-CPBA), re-acetylation, and finally hydrolysis of the compounds by NH3(g)/MeOH reactions were carried out. 1H NMR, 13C NMR, IR, and elemental analysis elucidated the structures of all synthesized compounds. The ?, ?-glucosidase, and ?-amylase inhibitory potentials of the new polycyclitols, conduritol A and F analogs, were examined for biological activity. Also, enzyme kinetic studies of well-active compounds were carried out. Compound 30 showed the best inhibition activity against ?, ?-glucosidase, and ?-amylase enzymes. Compound 28a showed the best activity against L929 and Capan-1 cell lines, and compound 22 showed the best activity against the A549 fibroblast cell line. Moreover, hemolysis (ASTM F756 standard) and genotoxicity test results were recorded. © 2024 Elsevier Inc.Öğe Koronavirüs-19 hastalığının makro ve moleküler olarak incelenmesi: Derleme(Karamanoğlu Mehmetbey Üniversitesi, 2021) Karagöz, Sami; Özbay, ErkanDünya Sağlık Örgütü verilerine göre, dünyada Ağustos 2021’in ortalarında (4.400.284’ü ölüm) 456.225.677, ülkemizde ise (53.891’i ölüm) 8.641.372 doğrulanmış Korona-virus 19 vakası bildirilmiştir. Korona-virus 19, sitokin salıverilme ile karakterize olan şiddetli akut solunum sendromu oluşturur. Sitokin aracılı hiperinflamasyon olası tedavileri artan ölüm oranlarını azaltmak amacıyla ivedilikle araştırılmaktadır. Günümüzde uzun vadeli etkileri bilinmemekle birlikte aşı uygulamaları yapılmasına rağmen, halen, Korona-viruslara karşı kesin onaylanmış bir tedavi uygulaması bulunmamaktadır. Deneyim ve bulunabilirliğe göre çok sayıda ilaç ampirik olarak kullanılmaktadır. Etkinliklerini ve güvenliğini gösteren çalışmalar hala yayınlanacaktır. Ancak bazı potansiyel tedaviler ve doğal tedaviler önerilmiştir. Çok sayıda aromatik bitki ve fitokimyasallar, koronaviruslar da dahil olmak üzere genetik ve işlevsel olarak farklı viruslara karşı terapötik kullanım için beklemektedir. Türkiye, zengin etnomedikal deneyimi ve zengin florasıyla (% 34 endemik) bu konuda araştırma yapmak için yüksek potansiyele sahiptir. Yüzyıllardır influenzaya karşı kullanılan bitkiler etkili alternatifler sunabilir.Öğe Determination of half maximal effective concentration (EC50) values on skeletal muscle mechanic activityof arum dioscoridis, a species belonging to arum genus, one of the plants of Karaman province region (phase 0 – preclinical studies)(Karamanoğlu Mehmetbey Üniversitesi, 2021) Özbay, Erkan; Türkseven, Çağatay Han; Karagöz, Sami; Büyükakıllı, BelginArum dioscoridis sadece Anadolu'da değil dünyanın çeşitli yerlerinde fitoterapötik olarak kullanılan bitkilerden biridir. Bu bitkinin kas mekanik aktivitesi üzerine etkileri konusunda literatürde herhangi bir çalışma bulunmamaktadır. Bu pilot çalışmada, Arum dioscoridis'in iskelet kasının kasılma aktivitesi üzerindeki yarı maksimum etkili konsantrasyon (EC50) değerleri belirlendi. Maksimum toksik olmayan konsantrasyon (MnTK) değerine gore farklı konsantrasyonlarda hazırlanan AD ekstraktına maruz bırakılan Wistar albino sıçan ekstansör digitorum longus kasının mekanik tepkileri 1, 10, 20, 40, 80 ve 100 Hz frekanslarında kaydedildi. Sonuç olarak, MnTK değerinin 1/16 ve 1/32 konsantrasyonlarında kontrole gore sırasıyla 20, 40, 80 Hz ve 40, 80 Hz frekanslarında mekanik tepkide artış ve daha yüksek konsantrasyon değerlerinde bir düşüş gözlemlendi.Öğe Synthesis of new generation calix[4]arene derivatives as fluorescence chemosensor and its theoretical calculation(2020) Azak, HacerCalixarenes are among the commonly preferred molecules of the supramolecular chemistrysince they are easily synthesizable and functionalizable.In this study, new types of calix[4]arenderivatives containing benzylisoquinoline groups were synthesized and the structures of theobtaining compounds were characterized by spectroscopic techniques such as 1H-NMR, 13CNMR. Synthesized calix[4]aren derivatives towards some metal cations (Ag+, Al+3, Ba+, Ca+2,Co+2, Cs+2, Fe+3, Hg+2, Li+, Pb+2, Mg+2, Mn+2, Na+, Cu+2, Ba+2, Ni+2, Zn+2, Sr+2 showedfluorescence behaviors ve these behaviors were investigated utilizing UV-visspectrophotometer and fluorescence spectroscopic techniques.It was found out according tothe obtained results that it got complexed in 1:1 ratio as stoichiometric as a result of itsactivation with aqueous solutions of Cu+2 and Fe+2 ions and responded as an off-on sensor. Inthis regard, a highly selective and sensitive sensor was developed. Theoretical studies werealso conducted in addition to the achieved experimental results. The bonding of metal ionswas also calculated theoretically by using Gaussian 09 and GaussView 5.0.8.Öğe Catalase-conjugated surfaces: H2O2 detection based on quenching of tryptophan fluorescence on conducting polymers(Elsevier Ltd, 2020) Gelen, S.S.; Munkhbat, T.; Rexhepi, Z.; Kirbay, F.O.; Azak, Hacer; Demirkol, D.O.Conducting polymers are promising materials used to prepare electrochemical and optical detection platforms for bioanalytical systems. After conjugation of biomolecules onto electropolymerized monomers for preparation of multifunctional surfaces, they can be used to easily monitor small molecules, macromolecules, and cells. In this study, multifunctional monomer with indole (necessary for fluorescence detection of H2O2) and carboxyl functional groups (necessary for covalent immobilization of biological material) was synthesized, electropolymerized, modified with biomolecules (catalase) and then applied for the selective detection of target analyte (H2O2). Tryptophan sequestered dithione [3,2-b:2?,3?-d] pyrrole (DTP-Trp) was synthesized and electropolymerized on indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates, which is a transparent support. Afterward, catalase (CAT) was immobilized on the Poly(DTP-Trp) using a zero-length crosslinker, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), via covalent bonds between carboxyl groups of CAT and amino groups of Poly(DTP-Trp). Surface characterization of Poly(DTP-Trp)/CAT was done by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX). The presence of Poly(DTP-Trp)/CAT on ITO-PET surfaces were also confirmed by electrochemical methods to show the success of support modification. Determination of H2O2 was investigated using fluorescence spectrometry based on quenching mechanism of H2O2 on the fluorescence of tryptophan. After optimization of working conditions of Poly(DTP-Trp)/CAT, H2O2 detection in synthetic samples was done without any interference of the matrices. © 2020 Elsevier LtdÖğe Calculation of conductive polymer-based SO2 and SO3 gas sensor mechanisms by using the DFT method(Springer, 2019) Azak, Hacer; Görgül, Resul; Tekin, Burak; Yıldız, MuratIn this study, we carried out with the DTP (dithieno(3,2-b:2,3-d) pyrrole) molecule which is a member of the conductive polymer class that is one of the topics that have been studied prevalently in recent times, and the density functional theory’s (DFT) calculation methods were used to shed light on the sensor mechanisms of its interactions with SOx (SO2 and SO3) sulfur oxides. The changes in the geometric and electronic characteristics of a sensor mechanism designed with the DTP molecule when it encountered sulfur oxides were examined. With these changes, the usability of DTP as a sensor material was proven. DTP sensor applications using this method were not investigated in previous studies. The B3LYP 6–31 G(d) levels of DFT were used in the calculations. In the calculations, during the interaction between analyte (SO2-SO3) and the conductive polymer DTP (dithieno(3,2-b:2,3-d) pyrrole), especially, the changes in its geometric and electronic structures were observed. With these changes that were observed in the geometric structure, as a result of the interaction between the conductive polymer and gas molecules, the resistance on the polymer’s main chain decreased, and conductivity increased. Calculations on the bandgap on HOMO-LUMO energy levels were observed to decrease. Thus, the structural conductivity of the molecule increased. Additionally, the experiments showed that, as a result of interaction with gas molecules, the bandgap in the ionization potential, electron affinity, and HOMO-LUMO energy levels varied. These variations showed the detection mechanisms for sulfur oxides by the DTP (dithieno(3,2-b:2,3-d) pyrrole) molecule that may be used to design sensorsÖğe Synthesis of an amine-functionalized naphthalene-containing conducting polymer as a matrix for biomolecule immobilization(Royal Soc Chemistry, 2013) Azak, Hacer; Güler, Emine; Can, Ümmügülsüm; Demirkol, Dilek Odacı; Yıldız, Huseyin Bekir; Talaz, Oktay; Timur, SunaN-functionalized dithienopyrroles (DTP-NH2) were synthesized and electropolymerized onto a graphite electrode as a novel conducting polymer matrix for biomolecule immobilization. H-1-NMR and C-13-NMR were utilized to investigate the characteristics of the monomer. After that, glucose oxidase (GOx) was immobilized onto the amino-functionalised matrix by means of glutaraldehyde. The surface morphologies of both DTP-NH2 and DTP-NH2-GOx were visualised by using SEM and fluorescence microscopy. The chronoamperometric signals of the electrochemical DTP-NH2-GOx biosensors were measured by monitoring the O-2 consumption during an enzymatic reaction in the presence of glucose at -0.7 V. After the optimization of the pH and scan number of the polymer deposition in batch mode, the DTP-NH2-GOx biosensor was also tested in Flow Injection Analysis (FIA) mode. The DTP-NH2-GOx biosensors had a very good linearity between 0.05 and 1.0 mM, and between 0.1 and 2.5 mM for glucose in batch and FIA modes, respectively. Finally, it was applied for glucose analysis in real samples where commercial glucose kits were used as the reference method to verify the data obtained with the proposed biosensor.Öğe Synthesis of 1,4-bis(indolin-1-ylmethyl)benzene derivatives and their structure-activity relationships for the interaction of human carbonic anhydrase isoforms I and II(Pergamon-Elsevier Science Ltd, 2013) Talaz, Oktay; Çavdar, Hüseyin; Durdağı, Serdar; Azak, Hacer; Ekinci, DenizSeveral 1,4-bis(indolin-1-ylmethyl)benzene-based compounds containing substituents such as five, six and seven cyclic derivatives on indeno part (9a-c) were prepared and tested against two members of the pH regulatory enzyme family, carbonic anhydrase (CA). The inhibitory potencies of the compounds at the human isoforms hCA I and hCA II targets were analyzed and K-I values were calculated. K-I values of compounds for hCA I and hCA II human isozymes were measured in the range of 39.3-42.6 mu M and 0.17-0.29 mu M, respectively. The structurally related compound indole was also tested in order to understand the structure-activity relationship. Most of the compounds showed good CA inhibitory efficacy. In silico docking studies of these derivatives within hCA I and II were also carried out and results are supported the kinetic assays. (C) 2012 Elsevier Ltd. All rights reserved.Öğe A comparative study: Immobilization of yeast cells and invertase in poly (ethyleneoxide) electrodes(Elsevier Science Bv., 2013) Yıldız, Hüseyin Bekir; Kamacı, Musa; Azak, Hacer; Seçgin, Ömer; Suer, ÖzlemYeast cells (Saccharomyces cerevisiae) and invertase enzyme were immobilized in thiophene capped poly(ethyleneoxide)/polypyrrole (PEO-co-PPy) and 3-methylthienyl methacrylate-co-p-vinyl benzyloxy poly(ethyleneoxide)/polypyrrole (CP-co-PPy) matrices. Immobilization of the enzyme and yeast cells was performed via entrapment in conducting copolymers during electrochemical polymerization of pyrrole through the thiophene moiety of the polymers. Maximum reaction rates, Michaelis-Menten constants, optimum temperature and pH values, operational and storage stabilities of the enzyme and yeast cell electrodes were investigated. (c) 2013 Elsevier B.V. All rights reserved.Öğe Electrochemical hydrogen peroxide nanosensor using a reduced graphene oxide-poly(6-(4H-dithieno[3,2-b:2 ',3 '-d]pyrrol-4-yl)hexan-1-amine) hybrid-modified electrode(Wiley) Azak, HacerThe construction and biofunctionalization of graphene-based conjugated polymer nanocomposite that included reduced graphene oxide-poly DTP-NH2 hybrid-modified glassy carbon electrode (GCE) for the electrochemical H2O2 sensing were accomplished in this work. For the construction of the hydrogen peroxide bioassay, as an initial step of fabrication of the nanobiosensor, a novel conductive polymer structure was synthesized by the Suzuki-Miyaura coupling reaction and structural characterization was carried out by H-1-NMR and Mass spectroscopy techniques. Then, graphene oxide was chemically synthesized according to Hummers' method to expand the effective surface area to enhance the interaction between enzymes and conjugated polymers. This synthesized structure was assembled by an electrochemically polymerized conductive polymer with graphene oxide on a GCE. The modified glassy electrode surface was obtained by covalent bonding of the electrochemically polymerized DTP-NH2 with graphene oxide and coated on each well as biomimetic material. The structure and sensing properties of the nanosensing hybrid structure were investigated using UV-vis, AFM, SEM, and XRD. Thanks to the fast electron transfer at the poly(DTP-NH2)/rGO nanocomposite electrode interface, the developed biosensor exhibits a fast and linear amperometric response upon H2O2. Finally, a biosensor that is more selective and sensitive to H2O2 was developed. Also, the Poly(DTP-NH2)/rGO nanocomposite based Hydrogen Peroxide Nano sensor displayed excellent selectivity as well as good reproducibility and stability. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48538.
