Bulunan: 13 Adet 0.001 sn
Koleksiyon [20]
Tam Metin [2]
Yayın Türü [4]
Yazar [20]
Konu Başlıkları [20]
Yayıncı [3]
Yayın Dili [2]
Dergi Adı [12]
Synthesis and characterization of the poly(ethylene glycol) grafted unsaturated microbial polyesters

Kılıçay, Ebru | Hazer, Baki | Çoban, Burak | Scholz, Carmen

Article | 2010 | Hacettepe Journal of Biology and Chemistry38 ( 1 ) , pp.9 - 17

Pseudomonas oleovorans was grown with either 10-undecenoic acid alone or the equimolar mixture of octanoic acid and 10-undecenoic acid to obtain unsaturated poly(3- hydroxy alkanoates) (PHA)s; poly(3-hydroxy-10-undecenoate) (PHU) and poly(3-hydroxyoctanoate- co-3-hydroxy-10-undecenoate) (PHOU), respectively. The addition of bromine to olefinic double bond, by reacting the unsaturated PHA with bromine in homogeneous solution in dark, was readily carried out. The brominated PHA was reacted with polyethylene glycol (PEG) in the presence of a base to obtain PHA-g-PEG graft copolymers. The polymers were characterized by $^ 1H$ NMR and FT . . .IR spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Pseudomonas oleovorans was grown with either 10-undecenoic acid alone or the equimolar mixture of octanoic acid and 10-undecenoic acid to obtain unsaturated poly(3- hydroxy alkanoates) (PHA)s; poly(3-hydroxy-10-undecenoate) (PHU) and poly(3-hydroxyoctanoate- co-3-hydroxy-10-undecenoate) (PHOU), respectively. The addition of bromine to olefinic double bond, by reacting the unsaturated PHA with bromine in homogeneous solution in dark, was readily carried out. The brominated PHA was reacted with polyethylene glycol (PEG) in the presence of a base to obtain PHA-g-PEG graft copolymers. The polymers were characterized by $^ 1H$ NMR and FTIR spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) Daha fazlası Daha az

One-step synthesis of triarm block copolymers via simultaneous reversible-addition fragmentation chain transfer and ring-opening polymerization

Öztürk, Temel | Göktaş, Melahat | Hazer, Baki

Article | 2010 | Journal of Applied Polymer Science117 ( 3 ) , pp.1638 - 1645

One-step synthesis of star copolymers by reversible addition-fragmentation chain transfer (RAFT) and ring-opening polymerization (ROP) by using a novel dual initiator is reported. Triarm block copolymers comprising one polystyrene (or polyacrylamide) arm and two poly(b-butyrolactone) arms were synthesized in one-step by simultaneous RAFT polymerization of styrene (St) (or acrylamide, designated as AAm) and ROP of b-butyrolactone (BL) in the presence of a novel trifunctional initiator, 1,2-propanediol ethyl xanthogenate (RAFT-ROP agent). This dual initiator was obtained through the reaction of 3-chloro-1,2- propanediol with the potas . . .sium salt of ethyl xanthogenate. The principal parameters such as monomer concentration, initiator concentration, and polymerization time that affect the one-step polymerization reaction were evaluated. The characterization of the products was achieved using Fourier-transform infrared spectroscopy (FTIR), 1H-nuclear magnetic resonance (1HNMR),13C-nuclear magnetic resonance ( 13C-NMR), Gas chromatography-mass spectrometry (GC-MS), gel-permeation chromatography (GPC), thermogravimetric analysis (TGA), and fractional precipitation (c) techniques. VC 2010 Wiley Periodicals, Inc Daha fazlası Daha az

ATRP of methyl methacrylate initiated with a bifunctional initiator bearing bromomethyl functional groups: Synthesis of the block and graft copolymers

Öztürk, Temel | Yılmaz-Savaşkan, Sevil | Hazer, Baki | Menceloğlu, Yusuf Z.

Article | 2010 | Journal of Polymer Science, Part A: Polymer Chemistry48 ( 6 ) , pp.1364 - 1373

This article reports the synthesis of the block and graft copolymers using peroxygen-containing poly(methyl methacrylate) (poly-MMA) as a macroinitiator that was prepared from the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in the presence of bls(4,4'-bromomethyl benzoyl peroxide) (BBP). The effects of reaction temperatures on the ATRP system were studied in detail. Kinetic studies were carried out to investigate controlled ATRP for BBP/CuBr/bpy initiating system with MMA at 40 °C and free radical polymerization of styrene (S) at 80 °C The plots of In ([M o]/[Mt]) versus reaction time are linear, corresp . . .onding to first-order kinetics. Poly-MMA initiators were used In the bulk polymerization of S to obtain poly (MMA-b-S) block copolymers. Poly-MMA initiators containing undecomposed peroygen groups were used for the graft copolymerization of polybutadiene (PBd) and natural rubber (RSS-3) to obtain crosslinked poly (MMA-g-PBd) and poly(MMAg-RSS-3) graft copolymers. Swelling ratio values (q v) of the graft copolymers in CHCl3 were calculated. The characterizations of the polymers were achieved by Fourier-transform infrared spectroscopy (FTIR), 1H-nuclear magnetic resonance (1H NMR), gelpermeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and the fractional precipitation (?) techniques. © 2010 Wiley Periodicals, Inc Daha fazlası Daha az

Synthesis, characterization, and antibacterial activity of metal nanoparticles embedded into amphiphilic comb-type graft copolymers

Kalaycı, Özlem A. | Cömert, Füsun B. | Hazer, Baki | Atalay, Turgay | Cavicchi, Kevin A. | Çakmak, Mükerrem

Article | 2010 | Polymer Bulletin65 ( 3 ) , pp.215 - 226

The synthesis, spectroscopic characterization, and antimicrobial efficiency of gold and silver nanoparticles embedded in novel amphiphilic comb-type graft copolymers having good film-forming properties have been described. Amphiphilic comb-type graft copolymers were synthesized by the reaction of chlorinated polypropylene (PP) (Mw = 140,000 Da) with polyethylene glycol (PEG) (Mn = 2,000 Da) at different molar ratios. Metal nanoparticles embedded graft copolymers were prepared by reducing solutions of the salts of silver or gold and the copolymer in tetrahydrofuran. The optical properties of the metal nanoparticle embedded copolymers . . . were determined by using UV-visible spectroscopy. Surface plasmon resonance (SPR) of the gold and silver nanoparticle embedded copolymers in toluene was observed at a maximum wavelength (?max) of 428 and 551 nm in the UV-VIS absorption spectra, respectively. The average particle diameters of the gold and silver nanoparticles were found to be 50 nm from the high resolution scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Amphiphilic polymer films containing silver and gold nanoparticles were found to be highly antimicrobial by virtue of their antiseptic properties to Escherichia coli and Staphylococcus aureus. © Springer-Verlag 2009 Daha fazlası Daha az

Synthesis and characterization of novel comb-type amphiphilic graft copolymers containing polypropylene and polyethylene glycol

Balcı, Murat | Allı, Abdulkadir | Hazer, Baki | Güven, Olgun | Cavicchi, Kevin | Çakmak, Mükerrem

Article | 2010 | Polymer Bulletin64 ( 7 ) , pp.691 - 705

Synthesis of microbial elastomers based on soybean oil. Autoxidation kinetics, thermal and mechanical properties

Hazer, Baki | Hazer, Derya Burcu | Çoban, Burak

Article | 2010 | Journal of Polymer Research17 ( 4 ) , pp.567 - 577

Microbial bioelastomers prepared by the autoxidation of the unsaturated medium-long chain length copoly- 3-hydroxyalkanoate's (mlcl-PHAs) based on soybean oily acids (Sy) have been reported. Pseudomonas oleovorans were grown on a series of the mixture of octanoic acid (OA) and Sy with the weight ratio of 20:80, 28:72 and 50:50 in order to obtain unsaturated mlcl-copolyesters coded PHO-Sy-2080, PHO-Sy-2872, and PHO-Sy-5050, respectively. The microorganism was also grown on the mixture of Sy and 10-undecenoic acid (UA) with the weight ratio of 50:50 to obtain unsaturated copolyester coded PHU-Sy-5050. The PHAs obtained were characteri . . .zed by 1H NMR and GC-MS techniques. Double bond contents of the unsaturated PHAs obtained were varying between 0.8 to 20 mol %. Autoxidation of the unsaturated copolyesters were carried out on exposure to air at room temperature in order to obtain new biomaterials whose mechanical strength was improved. Autoxidation kinetics, shelf life, mechanical and thermal properties of these biomaterials were evaluated Daha fazlası Daha az

The removal of heavy metal ions from aqueous solutions by novel pH-sensitive hydrogels

Yıldız, Ufuk | Kemik, Ömer Ferkan | Hazer, Baki

Article | 2010 | Journal of Hazardous Materials183 ( 01.Mar ) , pp.521 - 532

Novel non-ionic hydrogels were synthesized by radical homopolymerization of N-vinyl-2-pyrrolidone (VP) or by radical copolymerization of VP with methylacrylate (MA). A macroinimer (MIM) was used as a crosslinker and initiator, as well. The percentage of mass swelling ratios (SM), the molecular weight between crosslinks (Mc) and Young's modulus of the hydrogels were investigated. The hydrogels were used as binding materials for different heavy metal ions such as Cu2+, Cd2+, Ni2+ and Zn2+ under varying conditions. The binding capability of the hydrogels toward the metal ions decreases in the following order: Cu2+>Ni2+>Zn2+>Cd . . .2+. © 2010 Elsevier B.V Daha fazlası Daha az

Anomodon longifolius (Anomodontaceae, Bryopsida) new to the bryophyte flora of Turkey

Ören, Muhammet | Uyar, Güray | Keçeli, Tamer

Note | 2010 | Turkish Journal of Botany34 ( 2 ) , pp.141 - 145

Anomodon longifolius (Schleich. ex Brid.) Hartm. is reported for the first time from Turkey, bringing the total number of Anomodon species known from Turkey to 6. This record extends its distribution range to the Western Black Sea region of Turkey. The nearest localities to Turkey for this species are in Bulgaria, Greece, the Caucasus, and Iran. This submeridional species was collected from 3 different localities (in Bolu and Barti{dotless}n provinces) in Turkey. A site description, illustrations, and diagnostic characters of the Turkish specimens are given, together with notes on its distribution and ecology. © TÜBİTAK.

Eicosanoids mediate hemolymph oxidative and antioxidative response in larvae of Galleria mellonella L.

Büyükgüzel, Ender | Hyršl, Pavel | Büyükgüzel, Kemal

Article | 2010 | Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology156 ( 2 ) , pp.176 - 183

Antioxidant enzymes play a major role in the defense against pro-oxidative effects of xenobiotics and pro-oxidant plant allelochemicals in insects. We posed the hypothesis that eicosanoids also mediate antioxidant enzymatic defense reactions to pro-oxidant challenge. To test this idea, we reared first-instar larvae of Galleria mellonella (L.) with the lypoxygenase inhibitor, esculetin (0.001%), the phospholipase A2 inhibitor, dexamethasone (0.001%) and the dual inhibitor of cyclooxygenase and lipoxygenase, phenidone (0.1%) to seventh-instars. Newly ecdysed seventh-instars were then fed on artificial diet containing 0.05% xanthotoxin . . . (XA) for 2 days. Treating seventh-instar larvae of G. mellonella with XA induced lipid peroxidation and protein carbonylation as evident from the increased content of malondialdehyde (MDA) and protein carbonyls respectively, and antioxidative enzymatic response in a dose-dependent manner. High dietary XA concentrations (0.005 and 0.1%) were associated with increasing MDA and carbonyl content (by 3-fold) and antioxidant enzyme activities, superoxide dismutase (SOD) (by 3-fold) and catalase (CAT) (by 4-fold), and glutathione-dependent enzymes, glutathione S-transferase (GST) (by 15-fold) and glutathione peroxidase (GPx) (by 7-fold). Relative to control, eicosanoid biosynthesis inhibitors (EBIs) esculetin, dexamethasone and phenidone also resulted in impaired MDA content and antioxidant enzyme activities. However, carbonyl content did not differ between control- and EBIs-feeding larvae. Finally, MDA and carbonyl content, and antioxidant enzymes SOD, GST and GPx activities exhibited an incremental increase while CAT activity was decreased in the experimental larvae that had been reared on media amended with esculetin, dexamethasone and phenidone and then challenged with our standard XA challenge dose. Two of the markers indicated that significantly higher levels of oxidative stress were produced in the hemolymph tissue of larvae fed diets supplemented with EBIs and then challenged with XA. This oxidative stress was associated with elicited antioxidative responses by increasing SOD, GST and GPx and decreasing CAT activities in hemolymph. We infer from these findings that eicosanoids mediate insect antioxidant enzymatic responses to dietary pro-oxidants. © 2010 Elsevier Inc. All rights reserved Daha fazlası Daha az

Optical signal processing of interference fringes by Hartley transform method

Kaya, Hakan | Saraç, Zehra | Özer, Mahmut | Taşkın, Halit

Proceedings | 2010 | Proceedings of SPIE - The International Society for Optical Engineering7746 , pp.176 - 183

In this paper, the processing of interference fringes is achieved by Hartley transform method. The experimental and simulated interference fringe patterns are used for the signal analysis. Phase results are presented. These are compared with phase obtained by Fourier transform method. Disadvantages and advantages of Hartley transform method used for the evaluation of interference fringe patterns are given. © 2010 SPIE.

Simple production experiment of poly (3-hydroxy butyrate) for science laboratories and its importance for science process skills of prospective teachers

Koray, Özlem | Köksal, Mustafa Serdar | Hazer, Baki


Poly (3-hydroxybutyrate), PHB, is a biocompatible and biodegradable polymer accumulated in microorganism cells as a reserve material. PHB production in biotechnology laboratories has been carried out by using expensive instruments such as autoclave, a large thermostatted shaker, a freeze dryer, and an automatic refrigerated centrifuge. A very simple method of PHB production with Alcaligenes eutrophus for use in science teaching freshman laboratory is reported in this article. The study was conducted with 6 prospective elementary teachers. An ordinary glass 1 L jar, a 4L pressure cooker and thermostate for aquariums were used in ferm . . .entation process of the bacterium in nutrient solution containing table sugar as a substrate. In conclusion, the thermal and characterization data confirmed the PHB structure. Science Process Skills are investigated in this study. Qaulitative method was used to acquire data and analyze the science process skills experienced by the students in the experiment. The article discusses on development of some science process skills during the experimental process and gives suggestions for future use and research Daha fazlası Daha az

Amphiphilic poly(3-hydroxy alkanoate)s: Potential candidates for medical applications

Hazer, Baki

Review | 2010 | International Journal of Polymer Science2010 , pp.39 - 54

Poly(3-hydroxy alkanoate)s, PHAs, have been very attractive as biomaterials due to their biodegradability and biocompatibility. These hydrophobic natural polyesters, PHAs, need to have hydrophilic character particularly for drug delivery systems. In this manner, poly(ethylene glycol) (PEG) and hydrophilic functional groups such as amine, hydroxyl, carboxyl, and sulfonic acid have been introduced into the PHAs in order to obtain amphiphilic polymers. This review involves in the synthesis and characterization of the amphiphilic PHAs. Copyright © 2010 Baki Hazer.

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