Yazar "Sagiroglu, Ayten" seçeneğine göre listele
Listeleniyor 1 - 15 / 15
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Antioxidant Potential of Different Dill (Anethum Graveolens L.) Leaf Extracts(Taylor & Francis Inc, 2011) Isbilir, Sebnem Selen; Sagiroglu, AytenDill (Anethum graveolens L.) have been extensively used in salads, soups, and pickles for its aromatic odor and flavor. Recently, interest in plant-derived food additives has grown. In this study, the possible antioxidant properties of water, ethanol, and acetone extracts of dill leaves were investigated. In order to evaluate antioxidant activities of all extracts, different antioxidant tests were used, such as total antioxidant activity by ferric thiocyanate method, reducing power, DPPH (1,1-diphenyl-2-picryl-hydrazyl) free radical scavenging, hydrogen peroxide scavenging, and ferrous ions chelating activities. The content of phenolic compounds was also determined to be the gallic acid equivalent. Among the three extracts, the water extract of dill leaf showed the most potent antioxidative capacity in each assay, showing 79.66% (at 1 mg/mL) in the DPPH center dot radical scavenging activity, 63% (at 800 g/mL) in the metal chelating effect, 60% (at 400 g/mL) in the H2O2 scavenging activity, and 0.61 absorbance (at 1 mg/mL) in the reducing power.Öğe AN ASSESSMENT OF IN VITRO ANTIOXIDANT ACTIVITIES OF DIFFERENT EXTRACTS FROM PAPAVER RHOEAS L. LEAVES(Taylor & Francis Inc, 2012) Isbilir, Sebnem Selen; Sagiroglu, AytenCorn poppy (Papaver rhoeas L.) leaf has been extensively used as garniture in salads and drugs in folk medicine. In this study, the possible antioxidant properties of water (WE), ethanol (EE), and acetone (AE) extracts of corn poppy leaves were investigated using different antioxidant tests, including total antioxidant activity in linoleic acid system, DPPH center dot scavenging activity, reducing power, chelation activity, and hydrogen peroxide scavenging activity. In addition, the amount of total phenolics was also determined. Total antioxidant activities of all extracts were greater than 85% at 400 mu g/mL concentration. The scavenging effects of WE and EE on DPPH center dot radical were found to be 88.46 +/- 0.08% and 86.81 +/- 0.37% at 800 mu g/mL concentration, respectively, which was comparable to standard antioxidants, such as BHA and alpha-TP. The reducing power of extracts was in the order of WE > EE > AE. The percentage of metal chelating activity of 800 mu g/mL concentration of WE was found to be 79.51 +/- 4.05%. Our results indicated that the leaves of Papaver rhoeas L. showed the potential to be used as a natural antioxidant.Öğe Bioconversion of methanol to formaldehyde.: II.: By purified methanol oxidase from modified yeast, Hansenula polymorpha(Taylor & Francis Inc, 2006) Sagiroglu, Ayten; Altay, VolkanModified methylotrophic yeast Hansenula polymorpha (HP A16) that was obtained by repressing leucine oxotrophic yeast; a wild type of Hansenula polymorpha CB4732 was used in this study. The yeast is grown with methanol, which is used as a sole carbon source, using various methanol concentrations and temperatures, and methanol oxidase (MOX) which is a key enzyme of methanol metabolism; production is maximized. Whole yeast cells were cultivated under optimized inoculation conditions; they were separated into two portions. One portion of these cells was directly used in bioconversion of methanol to formaldehyde. The second portion of the free cells was broken into pieces and a crude enzyme extract was obtained. The MOX enzyme in this extract was purified via salt precipitation, dialysis, and chromatographic methods. The purified MOX enzyme of yeast (HP A16) oxidized the methanol to formaldehyde. Optimization of bioconversion conditions was studied to reach maximum activity of enzyme. The optimum temperature and pH were found to be 35 degrees C and pH 8.0 in boric acid/NaOH buffer, and it was stable over the pH range of 6 9, at the 20 degrees C 15 min. A suitable reaction period was found as 50 min. The enzyme indicated low carbon primary alcohols (C-2 to C-4), as well as methanol. Initially, MOX activity increased with the increase of methanol concentration, but enzyme activity decreased. The apparent K-m and V-max values for methanol substrate of HP A16 MOX were 0.25 mM and 30 U/mg, respectively. The purified MOX enzyme was applied onto sodium dodecyl sulphate-polyacrylamide gel electrophoresis; molecular weight of the enzyme was calculated to be about 670 kDa. Each MOX enzyme is composed of eight identical subunits, each of whose molecular weight is around 82 kDa and which contain eight moles of FAD as the prosthetic group, and the pI of the natural enzyme is found to be 6.4. The purified MOX enzyme was used in the bioconversion of methanol to formaldehyde as a catalyst; this conversion was compared to the conversion percentages of whole cells in our previous article in terms of catalytic performances.Öğe COMPARISON OF BIODIESEL PRODUCTIVITIES OF DIFFERENT VEGETABLE OILS BY ACIDIC CATALYSIS(Assoc Chemical Eng, 2011) Sagiroglu, Ayten; Isbilir, Sebnem Selen; Ozcan, Hakki Mevlut; Paluzar, Hatice; Toprakkiran, Neslihan M.Biodiesel has become a subject which increasingly attracts worldwide attention because of its environmental benefits, biodegradability and renewability. Biodiesel production typically involves the transesterification of a triglyceride feedstock with methanol or other short-chain alcohols. This paper presents a study of transesterification of various vegetable oils, sunflower, safflower, canola, soybean, olive, corn, hazelnut and waste sunflower oils, with the acidic catalyst. Under laboratory conditions, fatty acid methyl esters (FAME) were prepared by using methanol in the presence of 1.85% hydrochloric acid at 100 degrees C for 1 h and 25 degrees C for 3 h. The analyses of biodiesel were carried out by gas chromatography and thin layer chromatography. Also, biodiesel productivities (%) were determined on basis of the ratio of ester to oil content (w/w). The biodiesel productivities for all oils were found to be about 80% and about 90% at 25 and 100 degrees C, respectively. Also, the results showed that the yield of biodiesel depended on temperature for some oils, including canola, sunflower, safflower Os, but it was not found significant differences among all of the oil types on biodiesel productivities.Öğe Conversion of sunflower oil to biodiesel by alcoholysis using immobilized lipase(Informa Healthcare, 2008) Sagiroglu, AytenTransesterification reaction was performed using sunflower oil and short-chain alcohol by immobilized lipases in organic solvents. The fatty acid ester, which is the product of this reaction, can be used as a diesel fuel that does not produce sulfur oxide and minimize the soot particulate. Immobilized porcine pancreatic lipase (PPL) and Candida rugosa lipase (CRL) showed the satisfactory activity in these reactions. Immobilization of lipases was carried out using inorganic absorbance Celit 545 particle as a carrier. Organic solvent like hexane in reactions was required when methanol and ethanol were used as alcoholic substrate. The reaction could be performed in absence of solvent when 1-propanol and 1-butanol were used as short-chain alcohol. The activities of immobilized lipases were highly increased in comparison with free lipases because its activity sites became more effective. Immobilized enzyme could be repeatedly used without difficult method of separation and the decrease in its activity was not largely observed.Öğe Effects of Organophosphorus and Pyrethroid pesticides on antioxidant enzymes and reactivation effects of Pralidoxime:In vitro studies(Academic Publication Council, 2022) Paluzarl, Hatice; Sagiroglu, AytenThe present study aimed to assess the inhibition effects of organophosphate pesticides, malathion(R), dichlorvos(R); pyrethroid pesticides, deltamethrin(R), lambda-cyhaloethrin(R) on antioxidant enzymes and the reactivation ability of pralidoxime against pesticide inhibited-antioxidant enzymes. Oximes were reported by reactivation ability against organophosphate inhibited-acetylcholinesterase and we focused to investigate the reactivation effect of pralidoxime against organophosphate inhibited-antioxidant enzymes. IC50 values were determined by means of activity percentage diagrams. The concentrations of deltamethrin(R), malathion(R), dichlorvos(R), lambda-cyhaloethrin(R) that inhibited 50% of catalase were 5.2 mu M, 158 mu M, 133 mu M, 320 mu M, respectively, inhibited 50% of superoxide dismutase were 62 mu M, 240 mu M, 328 mu M, 2320 mu M, respectively and inhibited 50% of glutathione peroxidase were 0.7 mu M, 1198 mu M, 1638 mu M, 98 mu M, respectively. All pesticide doses showed an inhibition effect on antioxidant enzymes. Deltamethrin(R) wasfound to be a more potent inhibitor for the antioxidant enzymes followed by the rest of the pesticides used in this study. The reactivation effect of pralidoxime was determined for organophosphate inhibited-enzymes. Reactivation results showed that only catalase is reactivated by pralidoxime against dichlorvos(R) and malathion(R). Under the exposure of 50-800 mu M malathion(R) concentrations, the activities of catalase were calculated as 72-11%, respectively. After, inhibited catalase was incubated with 1 mM and 10 mM pralidoxime, the activities of catalase were calculated as 92-31% and 98-39%, respectively. Under the exposure of 100-1500 mu M dichlorvos(R) concentrations, the activities of catalase were calculated as 50-6%, respectively. After, inhibited catalase was incubated with 1 mM and 10 mM pralidoxime, the activities of catalase were calculated as 95-30% and 93-28%, respectively. When the results are examined, it is seen that increasing the pralidoxime concentration does not significantly affect the reactivation percentage of the catalase enzyme.Öğe Fresh broad (Vicia faba) tissue homogenate-based biosensor for determination of phenolic compounds(Taylor & Francis Ltd, 2014) Ozcan, Hakki Mevlut; Sagiroglu, AytenIn this study, a novel fresh broad (Vicia faba) tissue homogenate-based biosensor for determination of phenolic compounds was developed. The biosensor was constructed by immobilizing tissue homogenate of fresh broad (Vicia faba) on to glassy carbon electrode. For the stability of the biosensor, general immobilization techniques were used to secure the fresh broad tissue homogenate in gelatin-glutaraldehyde cross-linking matrix. In the optimization and characterization studies, the amount of fresh broad tissue homogenate and gelatin, glutaraldehyde percentage, optimum pH, optimum temperature and optimum buff er concentration, thermal stability, interference effects, linear range, storage stability, repeatability and sample applications (Wine, beer, fruit juices) were also investigated. Besides, the detection ranges of thirteen phenolic compounds were obtained with the help of the calibration graphs. A typical calibration curve for the sensor revealed a linear range of 5-60 mu M catechol. In reproducibility studies, variation coefficient (CV) and standard deviation (SD) were calculated as 1.59%, 0.64 X 10(-3) M, respectively.Öğe Functional and Biochemical Properties of Proteins from Safflower Seed(Taylor & Francis Inc, 2009) Sagiroglu, Ayten; Ozcan, Hakk M.; Satana, AzizThere are relatively few studies on the properties of proteins that comprise a major part of the safflower seed. The biochemical and functional properties of these proteins have not been fully discovered. In this study, safflower seed proteins were obtained by isoelectric precipitation in two fractions. One of the fractions (Fraction-1) was obtained at pH 10 and the other fraction was obtained, as the protein supernatant separate from the pH precipitate, by ultra filtration (Fraction-2). Functional and biochemical properties of both of fractions were investigated. Gel permeation chromatography (GPC) was applied to both fractions. GPC shows that high-molecular weight constituents are present only in fraction 1, whereas fraction 2 consists of proteins with lower molecular weights in comparison with protein standards. Sodium dodecyl sulfate polyacrylamide gel (SDS-PAGE) electrophoresis in the presence of mercaptoethanol and SDS with protein weight markers was applied to both of the fractions. The proteins in both of the fractions were separated and stained with Commassie Brillant blue R-250 dye on the PAGE gel. The molecular weight (Mw) of each protein band was determined graphically by plotting Log Mw and relative mobilities (Rf) using GS-300 scanning densitometry and a suitable computer program.Öğe A new multienzyme-type biosensor for triglyceride determination(Taylor & Francis Inc, 2016) Yucel, Alp; Ozcan, Hakki Mevluet; Sagiroglu, AytenAn amperometric multienzyme biosensor for determination of triglycerides (TGs) was constructed by mounting three gelatin membrane-bound enzymes on a glassy carbon electrode (working electrode), then connecting it to electrometer along with an Ag/AgCl reference electrode and a Pt auxiliary electrode. Characterization and optimization of the multienzyme biosensor, which is prepared with glycerol kinase (GK) (E.C.2.7.1.30), glycerol-3-phosphate oxidase (GPO) (EC 1.1.3.21), and lipase (EC 3.1.1.3), were studied. In the optimization studies for the bioactive layer components of the prepared biosensor, the optimum amounts of gelatin, bovine serum albumin (BSA), and glutaraldehyde was calculated as 1mg/cm(2), 1mg/cm(2), and 2.5%, respectively. Optimum pH and temperature of the reaction of biosensor were determined as 7.0 and 40 degrees C, respectively. Linear range of triolein for the biosensor was found from the calibration curve between several substrate concentration and Current. After optimization and characterization of the biosensor, its operationability in triglycerides was also tested.Öğe A Novel Amperometric Biosensor Based on Banana Peel (Musa cavendish) Tissue Homogenate for Determination of Phenolic Compounds(Informa Healthcare, 2010) Ozcan, Hakki Mevlut; Sagiroglu, AytenIn this study the biosensor was constructed by immobilizing tissue homogenate of banana peel onto a glassy carbon electrode surface. Effects of immobilization materials amounts, effects of pH, buffer concentration and temperature on biosensor response were studied. In addition, the detection ranges of 13 phenolic compounds were obtained with the help of the calibration graphs. Storage stability, repeatability of the biosensor, inhibitory effect and sample applications were also investigated. A typical calibration curve for the sensor revealed a linear range of 10-80 mu M catechol. In reproducibility studies, variation coefficient and standard deviation were calculated as 2.69%, 1.44 x 10(-3) mu M, respectively.Öğe A NOVEL BIOSENSOR BASED ON Lactobacillus acidophilus FOR DETERMINATION OF PHENOLIC COMPOUNDS IN MILK PRODUCTS AND WASTEWATER(Taylor & Francis Inc, 2011) Sagiroglu, Ayten; Paluzar, Hatice; Ozcan, Hakki Mevlut; Okten, Suzan; Sen, BurhanDifferent branches of industry need to use phenolic compounds (PCs) in their production, so determination of PCs sensitively, accurately, rapidly, and economically is very important. For the sensitive determination of PCs, some biosensors based on pure polyphenol oxidase, plant tissu, e and microorganisms were developed before. But there has been no study to develop a microbial phenolic compounds biosensor based on Lactobacillus species, which contain polyphenol oxidase enzyme. In this study, we used different forms of Lactobacillus species as enzyme sources of biosensor and compared biosensor performances of these forms for determination of PCs. For this purpose, we used lyophilized Lactobacillus cells (containing L. bulgaricus, L. acidophilus, Streptococcus thermophilus), pure L. acidophilus, pure L. bulgaricus, and L. acidophilus-and L. bulgaricus adapted to catechol in Lactobacilli MRS Broth. The most suitable form was determined and optimization studies of the biosensor were carried out by using this form. For preparing the bioactive layer of the biosensor, the Lactobacillus cells were immobilized in gelatin by using glutaraldehyde. In the study, we used catechol as a substrate. Phenolic compound determination is based on the assay of the differences on the respiration activity of the cells on the oxygen meter in the absence and the presence of catechol. The microbial biosensor response depends directly on catechol concentration between 0.5 and 5.0 mM with 18 min response time. In the optimization studies of the microbial biosensor the most suitable microorganism amount was found to be 10 mg, and also phosphate buffer (pH 8.0; 50 mM) and 37.5 degrees C were obtained as the optimum working conditions. In the characterization studies of the microbial biosensor some parameters such as substrate specificity on the biosensor response and operational and storage stability were examine. Furthermore, the determination of PC levels in synthetic wastewater, industrial wastewater, and milk products was investigated by using the developed biosensor under optimum conditions.Öğe Production of Ricinoleic Acid from Castor Oil by Immobilised Lipases(Taylor & Francis Inc, 2009) Ozcan, Hakki Mevlut; Sagiroglu, AytenPorcine pancreatic lipase (PPL), Candida rugosa lipase (CRL), and Castor bean lipase (CBL) were immobilized on celite by deposition from aqueous solution by the addition of hexane. Lipolytic performance of free and immobilized lipases were compared and optimizations of lipolytic enzymatic reactions conditions were performed by free and immobilized derivatives using olive oil as substrate. Afterwards, the influence on lipolysis of castor oil of free lipases and immobilized lipase derivatives have been studied in the case of production of ricinoleic acid. All of the lipases performances were compared and enzyme derivative was selected to be very effective on the production of ricinoleic acid by lipolysis reaction. Various reaction parameters affecting the production of ricinoleic acid were investigated with selected the enzyme derivative. The maximum ricinoleic acid yield was observed at pH 7-8, 50C, for 3hours of reaction period with immobilized 1,3-specific PPL on celite. The kinetic constants Km and Vmax were calculated as 1.6 10-4mM and 22.2mM from a Lineweaver-Burk plot with the same enzyme derivative. To investigate the operational stability of the lipase, the three step lipolysis process was repeated by transferring the immobilized lipase to a substrate mixture. As a result, the percentange of conversion after usage decreased markedly.Öğe Quantitative Analysis of a Promising Cancer Biomarker, Calretinin, by a Biosensing System Based on Simple and Effective Immobilization Process(Wiley-V C H Verlag Gmbh, 2016) Asav, Engin; Sagiroglu, Ayten; Sezginturk, Mustafa KemalCalretinin (CAL) is calcium binding protein, and its levels in blood and cerebrospinal fluids are increased, since its expression is increased various cancer types. A novel biosensor system fabricated by immobilization of a specific antibody to CAL, anti-Calretinin (anti-CAL), onto a gold electrode surface via an effective covalent binding method using mercaptohexanol, epichlorohydrin, and ethanolamine was reported for the sensitive, selective, and accurate analysis of CAL. The proposed biosensor showed a linear calibration range between 1 ng/mL and 5 ng/mL. LOD and LOQ values were determined as 0.11 ng/mL and 0.38 ng/mL, respectively. The standard deviation related to the reproducibility of the new biosensor system was calculated as 3.95%. Lastly, in order to state the applicability of the biosensor to early diagnosis of CAL in practice, artificial serum samples spiked with CAL have been analyzed by the proposed biosensor.Öğe Total phenolic content, antiradical and antioxidant activities of wild and cultivated Rumex acetosella L. extracts(Taylor & Francis Ltd, 2013) Isbilir, Sebnem Selen; Sagiroglu, AytenEdible greens, especially wild greens, play an important role in traditional diets and are rich in phenols and other compounds. The purpose of this study was to investigate total phenolic content (TPC) and antioxidant activities of ethanolic extracts from wild and cultivated Rumex acetosella L. The wild sheep sorrel extract inhibited lipid peroxidation and 1,1-diphenyl-2-picrylhydrazyl radical with EC50 values of 0.02 and 3.67mgml(-1); however, the EC50 values for cultivated sheep sorrel extract were 0.76 and 21.94mg ml(-1). In the reducing power assay, the values of measured absorbance were 0.723 and 0.430 for wild and cultivated extracts, respectively, at 1mgml(-1) concentration. The chelating of ferrous ions by the wild and cultivated sheep sorrel was determined as 59.4% and 56.2%, respectively, at 1mgml(-1) concentration. TPC of wild and cultivated sheep sorrel was found to be 69.21 +/- 8.5 and 57.57 +/- 1.8mg gallic acid equiv. g(-1) extract, respectively. There is a positive correlation between phenolic content and antioxidant assays. The results obtained in this study indicate that wild R. acetosella could be an important dietary source because of its good antioxidant properties.Öğe Ultrasensitive Impedimetric Biosensor Fabricated by a New Immobilisation Technique for Parathyroid Hormone(Springer, 2015) Ozcan, Hakki Mevlut; Yildiz, Kubra; Cakar, Cansu; Aydin, Tuba; Asav, Engin; Sagiroglu, Ayten; Sezginturk, Mustafa KemalThis paper presents a novel ultrasensitive and rapid impedimetric biosensor with new immobilisation materials for parathyroid hormone (PTH) with the aim to determine the PTH level in serum for the diagnosis and monitoring of parathyroid diseases such as hyperparathyroidism, adenoma, and thyroid cancer. The interaction between PTH and the biosensor was investigated with an electrochemical method. The biosensor was based on the gold electrode modified by mercaptohexanol (6-MHL). Anti-parathyroid hormone (anti-PTH) was covalently immobilised onto a self-assembled monolayer (SAM) by using epiclorhidrina (EPI) with ethanolamine (EA). The EPI-EA interaction represents the first use of these for the construction of biosensors in published reports. The immobilisation of the anti-PTH was monitored by electrochemical impedance spectroscopy, cyclic voltammetry and scanning electron microscopy (SEM) techniques. After the optimisation studies of immobilisation materials such as 6-MHL, EPI, EA and glutaraldehyde, linearity, repeatability and sensitivity of biosensor were evaluated as the performance of biosensor. PTH was detected within a linear range of 0.1-0.6 pg/ml, and the detection limit was 0.1 fg/ml. The specificity of the biosensor was also investigated. Finally, the described biosensor was used to detect the PTH levels in artificial serum samples.
