Person: OSMAN, BİLGEN
Loading...
Email Address
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
OSMAN
First Name
BİLGEN
Name
11 results
Search Results
Now showing 1 - 10 of 11
Publication A new design to enhance the enzyme activities: Investigation of L-asparaginase catalytic performance by IMAC effect on g-C₃N₄ nanolayers(Springer, 2023-07-08) Sert, Buse; Acet, Ömür; Noma, Samir Abbas Ali; Osman, Bilgen; Odabaşı, Mehmet; Ocakoğlu, Kasim; NOMA, Samir Abbas Ali; OSMAN, BİLGEN; Fen Edebiyat Fakültesi; Kimya Bölümü; 0000-0001-8406-149X ; ABH-1773-2021; ABF-4791-2020Recently, graphite carbon nitride (g-C3N4) has come to the fore as a new material with its carbon-based two-dimensional structure, simple preparation procedure, and excellent physicochemical stability properties. This study aims to investigate the activity and kinetic studies of the L-asparaginase enzyme via immobilized metal ion affinity chromatography (IMAC) process of g-C3N4 nanolayers. Firstly, g-C3N4 nanolayers were synthetized and Ni2+ ions were binded their surfaces. The synthesized samples were investigated by SEM, ICP-MS, XRD, and FTIR. The highest L-ASNase adsorption on Ni2+-g-C3N4 nanostructures was 444.1 mg/g, at 3 mg/mL L-ASNase concentration. Optimal medium conditions for L-ASNase adsorption occurred at pH 8.0 and 25 degrees C. The immobilized enzyme showed improved stability relating to the soluble enzyme in extreme situations. On the other hand, the storage stability and reusability of the immobilized enzyme were found to be approximately 64 and 53% of the original activity after 29 days at room temperature and 10 cycles, respectively. From the Michaelis-Menten constants Km and Vmax, both of them decreased after immobilization compare to the free one. The obtained outcomes showed that the g-C3N4 is a suitable matrix for L-asparaginase immobilization with ideal catalytic efficiency and improved stability.[GRAPHICS].Publication Adsorption of cinnabarinic acid from culture fluid with magnetic microbeads(Wiley, 2016-02-01) Sarıkaya, Aslı Göçenoğlu; Osman, Bilgen; Kara, Ali; Pazarlıoğlu, Nurdan; Besirli, Necati; GÖÇENOĞLU SARIKAYA, ASLI; OSMAN, BİLGEN; KARA, ALİ; Besirli, Necati; Fen Edebiyat Fakültesi; Kimya Bölümü,; 0000-0002-7161-7003; 0000-0001-8406-149X; 0000-0003-2457-6314; AAC-6901-2020; ABF-4791-2020; JXW-6168-2024; AAG-6271-2019In this study, antimicrobial pigment cinnabarinic acid (CA) was produced from Pycnoporus cinnabarinus in laboratory-scale batch cultures. Magnetic poly(ethylene glycol dimethacrylate-N-methacryloyl-l-tryptophan methyl ester) [m-poly(EGDMA-MATrp)] beads (average diameter = 53-103 mu m) were synthesized by copolymerizing of N-methacryloyl-l-tryptophan methyl ester (MATrp) with ethylene glycol dimethacrylate (EGDMA) in the presence of magnetite (Fe3O4) and used for the adsorption of CA. The m-poly(EGDMA-MATrp) beads were characterized by N-2 adsorption/desorption isotherms (Brunauer Emmet Teller), X-ray photoelecron spectroscopy, scanning electron microscopy, infrared spectroscopy, thermal gravimetric analysis, electron spin resonance and swelling studies. The efficiency of m-poly(EGDMA-MATrp) beads for separation of CA from culture fluid was evaluated. The effects of pH, initial concentration, contact time and temperature on adsorption were analyzed. The maximum CA adsorption capacity of the m-poly(EGDMA-MATrp) beads was 272.9mgg(-1) at pH7.0, 25 degrees C. All the isotherm data can be fitted with the Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The adsorption process obeyed pseudo-second-order kinetic model. Thermodynamic parameters H = 5.056kJmol(-1), S = 52.44JK(-1)mol(-1) and G = -9.424kJmol-(1) to -11.27kJmol-(1) with the rise in temperature from 4 to 40 degrees C indicated that the adsorption process was endothermic and spontaneous.Publication L-(+)-tryptophan methyl ester derived polymeric microbeads as an efffiicient heterogeneous catalyst for green synthesis of 2-amino-4-(nitromethyl)-4h-chromene-3-carbonitriles(Tubitak Scientific & Technological Research Council Turkey, 2022-01-01) Poslu, Ayse Haliç; Kaya, Yunus; Koz, Ömer; Koz, Gamze; Osman, Bilgen; OSMAN, BİLGEN; Fen Edebiyat Fakültesi; Kimya Bölümü; 0000-0001-8406-149X; ABF-4791-2020The cross-linked microbeads with average diameter of 106-300 mu m, [poly(EGDMA-MATrp)], were obtained by copolymerization reaction of N-methacryloyl-L-(+)-tryptophan methyl ester (MATrp) with ethylene glycol dimethacrylate (EGDMA) and successfully applied as a heterogeneous catalyst in conjugate addition reaction of nitromethane to substituted 2-iminochromenes in aqueous media. A variety of 2-amino-4-(nitromethyl)-4H-chromene-3-carbonitriles has been synthesized in good yields. Polymeric microbeads were very durable and reused 5 times without a significant loss of activity. DFT calculations and experimental results revealed the significant role of Tr-Tr interactions as well as hydrogen bonding in the reaction mechanism.Publication Dummy molecularly imprinted polymer-based solid-phase extraction method for the determination of some phthalate monoesters in urine by gas chromatography-mass spectrometry analysis(Elsevier, 2023-11-24) Küçük, Melike; Osman, Bilgen; Özer, Elif Tumay; KÜÇÜK, MELİKE; OSMAN, BİLGEN; TÜMAY ÖZER, ELİF; Fen Edebiyat Fakültesi; Kimya Bölümü; 0000-0001-8406-149X; V-1616-2019; JCP-4547-2023; JME-2199-2023A dummy molecularly imprinted polymer-based solid-phase extraction (SPE) sorbent was used for the selective extraction of some phthalate monoesters, monoethyl phthalate (MEP), monobutyl phthalate (MnBP) and mono-(2-ethylhexyl) phthalate (MEHP) in urine prior to gas-chromatography-mass spectrometry (GC-MS) analysis. Diethyl phthalate (DEP), a phthalate ester, was successfully used as a dummy template to prepare selective sorbent for MEP, MnBP, and MEHP extraction. DEP-imprinted poly(ethylene glycol dimethacrylate N-meth-acryloyl-L-tryptophan methyl ester) (DPEMT) microbeads were synthesized by suspension polymerization and characterized by Fourier Transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Brunauer Emmet Teller (BET) analysis. The critical parameters (i.e., pH, sorbent amount, ionic strength, sample volume, elution solvent) affecting the extraction performance of the DPEMT-SPE sorbent were optimized. Under optimum conditions, good linearities were obtained in the concentration range of 4 to 60 ng/mL with deter-mination coefficients (R2) of greater than 0.9959. The developed SPE method provided low limits of detection (LOD) of 0.05-1.20 ng/mL and limits of quantification (LOQ) of 0.18-4.01 ng/mL with relative standard de-viations (RSDs) of less than 8.95 % for intra-and inter-day analyses. The proposed SPE method was used to analyze phthalate monoesters in spiked urine samples, and recoveries of 97.45-109.26 % were obtained. DPEMT-SPE sorbent was reused for 15 times without any losses of performance. Consequently, a highly selective and sensitive SPE method based on a dummy molecularly imprinted polymer combined with GC-MS was suc-cessfully developed to monitor human phthalate exposure via urine samples.Publication P(hema)-so 3 h catalyst: Preparation, characterization and its catalytic activity in ritter reaction(Springer, 2022-10-15) ARIKAN ÖLMEZ, NEVİN; Ölmez, Nevin Arıkan; OSMAN, BİLGEN; Osman, Bilgen; Fen Edebiyat Fakültesi; Kimya Bölümü; 0000-0001-8406-149X; AAH-6337-2021In this study, poly(hydroxyethyl methacrylate) [P(HEMA)] microsphere-supported sulfuric acid [P(HEMA)-SO3H] was prepared as a novel heterogenous solid acid catalyst and its catalytic activity was investigated in the synthesis of amides via Ritter reaction. The P(HEMA) microspheres were synthesized via suspension polymerization and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer, Emmett and Teller surface area and energy dispersive X-ray (EDX) analyses. The specific surface area and the pore volume of the microspheres were determined as 33.80 m(2)/g and 1.490 cm(3)/g, respectively. The pore size was in the range of 9.18-122.59 A degrees. The specific surface area of P(HEMA)-SO3H catalyst was 26.24 m(2)/g decreasing after modification with sulfo groups. FTIR, SEM and EDX analyses demonstrated that P(HEMA) microspheres were successfully modified with sulfo groups. The acidity of P(HEMA)-SO3H catalyst was determined as to 7.48 +/- 0.16 mmol H+/g P(HEMA)-SO3H catalyst by titration with standardized NaOH solution. The catalyst was then successfully applied in the Ritter reaction to prepare a series of different amides in high to excellent yields. The P(HEMA)-SO3H catalyst was recovered and reused four times without a significant decrease in the catalytic activity. The other advantages of this novel catalyst include excellent yield, short reaction time and solvent-free conditions.[GRAPHICS]Publication A rational approach for 3d recognition and removal of l-asparagine via molecularly imprinted membranes(Elsevier, 2023-01-17) Acet, Ömür; Acet, Burcu Onal; Dikici, Emrah; Odabası, Mehmet; NOMA, Samir Abbas Ali; Noma, Samir Abbas Ali; OSMAN, BİLGEN; Osman, Bilgen; Fen Edebiyat Fakültesi; Kimya Ana Bilim Dalı; 0000-0001-8406-149X; ABF-4791-2020; ABH-1773-2021In this study, a L-asparagine (L-Asn) imprinted membranes (L-Asn-MIPs) were synthesized via molecular imprinting for selective and efficient removal of L-Asn. The L-Asn-MIP membrane was prepared by using acrylamide (AAm) and hydroxyethyl methacrylate (HEMA) as a functional monomer and a comonomer, respectively. The membrane was characterized by scanning electron microscopy (SEM) and Fourier Transform infrared spectroscopy (FTIR). The L-Asn adsorption capacity of the membrane was investigated in detail. The maximum L-Asn adsorption capacity was determined as 408.2 mg/g at pH: 7.2, 24 degrees C. Determination of L-Asn binding behaviors of L-Asn-MIPs also shown with Scatchard analyses. The effect of pH on L-Asn adsorption onto the membrane and also the selectivity and reusability of the L-Asn-MIPs for L-Asn adsorption were determined through L-asparaginase (L-ASNase) enzyme activity measurements. The selectivity of the membrane was investigated by using two different ternary mixtures; L-glycine (L-Gly)/L-histidine (L-His)/L-Asn and L-tyrosin (L-Tyr)/L-cystein(L-Cys)/L-Asn. The obtained results showed that the L-Asn-MIP membranes have a high selectivity towards L-Asn.Publication Thioether-substituted benzimidazolium salts: Synthesis, characterization, crystal structure, and their inhibitory properties against acetylcholinesterase and xanthine oxidase(Elsevier, 2023-05-10) Yavuz, Kemal; Sen, Betül; Taşkın-Tok, Tuğba; Aktas, Aydın; Ateş, Burhan; Aygün, Muhittin; Gök, Yetkin; OSMAN, BİLGEN; Noma, Samir Abbas Ali; NOMA, Samir Abbas Ali; Fen Edebiyat Fakültesi; Kimya Ana Bilim Dalı; ABF-4791-2020 ; ABH-1773-2021The sulfurous compounds are known as organosulfur, which has been associated with numerous biological activities in both natural products and synthetic organic compounds. In this work, we present the synthesis of a series of 4-(methylthio)benzyl substituted benzimidazolium salts. All compounds were characterized using NMR (1H and 13C) and FTIR spectroscopic methods as well as an elemental analysis technique. The molecular and crystal structures of the compound 1a were determined by X-ray crystallography revealing that the compound crystallized in the trigonal space group R-3. Enzyme inhibition studies demonstrated that a new series of sulfurous compounds precursors were highly potent inhibitors for xanthine oxidase (XO) and acetylcholinesterase (AChE) enzyme. The IC50 values were found in the range of 0.548 +/- 0.033 to 0.725 +/- 0.043 mu M for XO promising strategy for the treatment from gout disease, while IC50 values were found in the range 0.813 +/- 0.076 to 1.149 +/- 0.072 mu M toward AChE as the key enzyme promising strategy for the treatment of neurological disorders such as Alzheimer's disease (AD). Furthermore, pharmacodynamics studies prove the binding interaction patterns, structural orientations and drug potential of sulfide derivatives in the binding sites of xanthine oxidase (XO) and acetylcholinesterase (AChE) enzymes. Potential inhibitors (compounds 1d-f) were compared with standard compounds allopurinol (for XO) and donepezil (for AChE). Compared to the positive compound of target XO, the 4-vinylbenzyl group of potential compound 1f and the 4-methylbenzyl group of compound le more effectively formed electrostatic and hydrophobic interactions with the target's interaction site. While donepezil as standard compound interacts only at the peripheral anionic site of AChE, the related compounds interact with both regions (PAS and CAS sites) of the same target. These compounds were placed at the active sites of the respective targets by molecular docking method using AutoDock software. Binding energy, binding modes and interaction types were used to evaluate the series of 4-(methylthio)benzyl substituted benzimidazolium salts's ability to bind to each target. Binding energy lower than zero remarks spontaneous binding, and equal and/or lower than -5 kcal/mol remarks good binding. Besides XO, the related compounds show higher activity against the AChE enzyme. They can also be analyzed as strong candidate compounds in biological studies of related enzymes.Publication Preparation and characterization of latanoprost-loaded pva nanofibers as an ocular drug delivery system for glaucoma treatment(Taylor & Francis As, 2023-05-15) Karaca, Esra; KARACA, ESRA; Cesur, Merve İlkay Altuntuğ; Osman, Bilgen; OSMAN, BİLGEN; KANMAZ, DİLAYDA; TÜMAY ÖZER, ELİF; Baykara, Mehmet; BAYKARA, MEHMET; Tıp Fakültesi; Oftalmoloji Ana Bilim Dalı; 0000-0001-8406-149X; 0000-0002-5555-1649; 0000-0003-1777-3977; HSI-3968-2023; AAS-8480-2020In this study, latanoprost-loaded polyvinyl alcohol (PVA/LAT) nanofibers were developed as an ocular drug delivery system for glaucoma treatment. The nanofibers were constructed via electrospinning and crosslinked by glutaraldehyde. The characterization studies were conducted by scanning electron microscopy, Fourier Transform infrared spectroscopy, Brunauer, Emmett, and Teller analyses, water contact angle measurements, and also swelling and degradation studies. The PVA/LAT nanofibers crosslinked with 0.5% glutaraldehyde solution for 20 min had a cumulative release of 52% for 23 days. The results demonstrated that the PVA/LAT nanofibers have a usage potential as an ocular drug delivery system for glaucoma treatment.Publication Adsorptive removal of 4-hydroxybenzoic acid via cross-linked polymeric microbeads: Analysis of isothermal, kinetic and thermodynamic parameters(Taylor & Francis Inc, 2023-05-26) Özer, Elif Tumay; Osman, Bilgen; KÜÇÜK, MELİKE; OSMAN, BİLGEN; TÜMAY ÖZER, ELİF; Fen Edebiyat Fakültesi; Kimya Bölümü; 0000-0001-8406-149X; JCP-4547-2023In this study, the performance of cross-linked microbeads prepared through suspension polymerization was investigated for removal of 4-hydroxybenzoic acid (4-HBA) from aqueous solution. Adsorption studies were conducted at different pHs (2.0-8.0), temperatures (282-308 K) and initial 4-HBA concentrations (1-500 mg/L). The maximum 4-HBA adsorption was 49.05 +/- 2.89 mg/g at pH 2.0 (282 K). The adsorption data obeyed to the Langmuir isotherm model. The modified Ritchie second-order and the pseudo second-order kinetic model fitted the adsorption data. The 4-HBA adsorption capacity did not significantly change after 10 consecutive usages. Gibbs free energy changes of the adsorption were calculated as -24.372, -28.431 and -29.093 kJ/mol for 282, 298 and 308 K, respectively. The microbeads were also used for the removal of 4-HBA from spiked river water samples. The removal efficiencies of 43.2% to 68.8% and RSDs of 0.49% to 4.78% demonstrated the usability of the microbeads in application.Publication Superhydrophobic surface based on cross-linked polymer(Iop Publishing Ltd, 2019-05-01) Osman, Bilgen; OSMAN, BİLGEN; Aydemir, Tuğba Gün; Mühendislik Fakültesi; 0000-0001-8406-149X; ABF-4791-2020The aim of this study was to prepare a superhydrophobic surface by coating poly(divinylbenzene-N-methacryloyl-amido-L-phenylalanine ethyl ester) [poly(DVB-MAPA)] cross-linked polymer onto a glass surface. N-methacryloyl-amido-L-phenylalanine ethyl ester (MAPA) and 1, 4-divinylbenzene (DVB) were used as a monomer and a cross-linker, respectively. The polymerization mixture was dispersed in 1, 4 butanediol (BDO) for phase separation and polymerized on the glass surface. The superhydrophobic surface was characterized with Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and contact angle measurements. The effect of the composition of a polymerization mixture on hydrophobicity was investigated by varying the cross-linker to monomer mol ratio. Additionally, the influence of the composition of monomer/BDO mixtures was determined. The prepared poly(DVB-MAPA) surface showed a superhydrophobicity with a high water contact angle (WCA) of 162 degrees and a low sliding angle (SA) of 7 degrees . Moreover, the poly(DVB-MAPA) surface has a good chemical, thermal and daylight stability.