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    Asymmetric Reduction of Monoketo Hexadecanoic Acid Methyl Esters
    (Asian Journal Of Chemistry, 2013) Turker, Gulen; Yusufoglu, Ayse
    Methyl 2-,3-,6-,8-,14- and 15-keto hexadecanoates were reduced by using NaBH4 in presence of 1,2;5,6-di-O-isopropilydene-D-glucofuranose [DIPGH], R(+)-1,1'-binaphthyl-2,2'-diol [RBND] and pivalic acid [PA]. The reduction of 2- and 3-keto esters in the presence of (+)-1,1'-binaphthyl-2,2'-diol results in considerably higher stereoselectivities (95 % ee). Enantiometric excess (ee %) was determined by H-1 and C-13 NMR analyses using a shift reagent, Eu(tfc)(3).
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    Biosorption of Co(II), Cr(III), Cd(II), and Pb(II) Ions from Aqueous Solution Using Nonliving Neochloris Pseudoalveolaris Deason & Bold: Equilibrium, Thermodynamic, and Kinetic Study
    (Taylor & Francis Inc, 2012) Kizilkaya, Bayram; Dogan, Fatih; Akgul, Riza; Turker, Gulen
    In this study, biosorption of cobalt(II), chromium(III), cadmium(II), and lead(II) ions from aqueous solution was studied using the algae nonliving biomass (Neochloris pseudoalveolaris, Np) as natural and biological sorbents. The effect of pH, contact time, temperature, and metal concentration on the adsorption capacity of metal ions was investigated. The maximum adsorption capacities for Co(II), Cr(II), Cd(II), and Pb(II) were found to be 20.1, 9.73, 51.4 and 96.2 mg/g at the optimum conditions, respectively. The experiments showed that when pH increased, an increase in the adsorption capacity of the biomass was observed too. The kinetic results of adsorption obeyed a pseudo second-order model. Freundlich and Langmuir isotherm models were applied to experimental equilibrium data of metal ions adsorption and the value of R-L for Pb(II), Cb,(II), Co(II), and Cr(III) was found to be 0.376, 0271, 0872, and 096, respectively. The thermodynamic parameters related to the adsorption process such as E-a, Delta G(0), Delta H-0, and Delta S-0 were calculated. Delta H-0 values (positive) showed that the adsorption mechanism was endothermic. Weber-Morris and Urano-Tachikawa diffusion models were also applied to experimental equilibrium data. The algae biomass was effectively used as a sorbent for the removal of metal ions from aqueous solutions.
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    Comparative Study of Biosorption of Heavy Metals Using Living Green Algae Scenedesmus quadricauda and Neochloris pseudoalveolaris: Equilibrium and Kinetics
    (Taylor & Francis Inc, 2012) Kizilkaya, Bayram; Turker, Gulen; Akgul, Riza; Dogan, Fatih
    The biosorption of several heavy metals such as cobalt(II), chromium(III), lead(II), cadmium(II), nickel(II), and manganese(II) from aqueous systems on living microalgae cultures, Scenedesmus quadricauda and Neochloris pseudoalveolaris were studied under laboratories conditions. The kinetic and statistical parameters were calculated by using the data obtained from batch cultivation and well fitted a pseudo-first-order rate equation. The initial metal concentrations in solution were about 5-40 mg . L-1. According to the pseudo-second-order model, the biosorption capacities of Scenedesmus quadricauda for Co(II), Cr(III), Pb(II), Cd(II), Ni(II), and Mn(II) ions were found in the ranges of 2.14-52.48, 1.98-81.98, 8.05-4.26, 7.81-24.96, 2.17-55.71, and 3.54-75.20 mg g(-1), respectively. Kinetic studies revealed that the metal uptake capacity of each living green algae was rather fast. It was also observed that the biosorption kinetic rate decreased with increasing concentration for both microalgae. The application of diffusion-controlled models to the experimental results indicated that the contribution of intraparticle diffusion to the overall sorption kinetics was not very important. Results showed that Co(II), Cr(III), Pb(II), Cd(II), Ni(II), and Mn(II) ions could effectively be absorbed by using living microalga cultures from aqueous solutions.
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    Determination of Organic Acid Composition and Free Radical Scavenging Capacity of Kefir
    (Asian Journal Of Chemistry, 2014) Turker, Gulen; Kizilkaya, Bayram; Arifoglu, Nazan
    The organic acid composition as well as the free radical scavenging capacity of kefir produced from different kinds of milk was investigated. The organic acid composition of the samples was determined by high performance liquid chromatography (HPLC), while free radical scavenging capacity was evaluated spectrophotometrically. Oxalic acid, acetic acid, citric acid and succinic acids were found to be significantly higher in kefir produced from cow milk (p < 0.05), while malic acid and lactic acid were significantly higher in kefir produced from goat milk (p < 0.05). The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity of kefir produced from goat milk was significantly higher than that of kefir made from cow milk (p < 0.05). There was a high correlation between the malic acid and lactic acid formation and the free radical scavenging activity of the samples, implying that the formation of these organic acids during kefir production positively enhances the free radical scavenging capacity of the fermented milk products.
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    Determination of some nutritional compositions of roe samples of the edible sea urchin Paracentrotus Lividus (Lamarck, 1816) in the Dardanelles (Marmara Sea)
    (Natl Inst Science Communication-Niscair, 2015) Kizilkaya, Bayram; Ozalp, H. Baris; Turker, Gulen; Alparslan, Mustafa; Tekinay, A. Adem
    In this study, the nutritional composition of gonad samples of Paracentrotus lividus collected from three different stations in the Sea of Marmara (Dardanelles) and the Northern Aegean Sea, Bozcaada Island during the summer season of 2012 was investigated. As a purpose of the research, the effect of total carotenoids and free radical-scavenging activity assay of three different extracts (methanol, acetone and chloroform extracts) have been determined. Total carotenoids were found to range between 131 and 179 mu g/g of sea urchin. The current study shows that the highest inhibition was found as 99.1 (%) in methanolic extract sampled from Tuzburnu (the first station). Macro (Ca, Na, K and Mg) and micro (Cu, Fe, Mn and Zn) mineral composition of urchins was specified by ICP-OES. Results show that sea urchin was found to be rich in total carotenoids, antioxidant capacity, macro and micro minerals.
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    Enhancement of antioxidant properties of Gongolaria barbata (Phaeophyceae) by optimization of combined light intensity and salinity stress
    (Taylor & Francis Ltd, 2022) Ak, Ilknur; Cankiriligil, Ekrem Cem; Turker, Gulen; Sever, Onur; Abomohra, Abdelfatah
    The present study aimed to optimize the light intensity coupled with different salinity regimes for enhanced growth and antioxidant properties of the brown seaweed Gongolaria barbata. Five experimental trials (T-1-T-5) were suggested using response surface methodology, where growth rate and antioxidant properties of G. barbata were evaluated in each run at the end of the experiment. The model for growth rate showed differences not statistically significant among all studied groups. However, concentration of methanol extract needed to scavenge 50% of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals (IC50), total phenolics, total flavonoids, total carotenoids, chlorophyll a and chlorophyll c showed significant differences among the five studied groups. Total phenolic and flavonoid contents were primarily affected by light, showing the highest values of 2.08 mg gallic acid equivalent g(-1) and 2.41 mg rutin g(-1) at 50 mu mol photon m(-2) s(-1). However, salinity stress showed a more pronounced impact on pigments. DPPH scavenging activity was influenced by the concentration of other compounds, which showed a significant increase by 34% in group T-4. The present study recommended light intensity of 53.86 mu mol photons m(-2) s(-1) at 24.02 parts per thousand salinity as the optimum conditions to achieve the maximum antioxidant activity along with phenolic and flavonoid contents (desirability = 0.82), without significant impact on the growth.
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    Evaluation of Fatty Acid Composition, Antioxidant and Antimicrobial Activity, Mineral Composition and Calorie Values of Some Nuts and Seeds from Turkey
    (Acg Publications, 2012) Kirbaslar, Fatma Gulay; Turker, Gulen; Ozsoy-Gunes, Zeliha; Unal, Muammer; Dulger, Basaran; Ertas, Erdal; Kizilkaya, Bayram
    The samples of the hazelnut, peanut, pistachio, almond, walnut, chestnut, pumpkin seed and sunflower seed were collected from Turkey. The fatty acid compositions of Turkish nut and seed oils were analyzed by Gas Chromatography (GC) were determined. The antioxidant activity of the samples was assessed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity assay toward BHT and Vitamin C. Retinol and alpha-tocopherol were analyzed using High-Pressure Liquid Chromatography with UV Detector (HPLC-UV). The antimicrobial and antifungal activities of Turkish nut and seeds were evaluated using the disk diffusion method toward 9 bacteria and 5 yeasts. The nut and seeds showed strong antimicrobial activity against the test organisms. Spectroscopic determination of minerals (Calcium, magnesium, potassium, sodium, iron, copper, manganese, selenium, zinc, chromium, aluminum) of nuts and seeds was performed with inductively coupled plasma-atomic emission spectrometer (ICP-AES). The calorie values of samples were measured using a Bomb Calorimeter.
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    Health Risk Assessment and Mineral Contents in Brown Seaweed Colpomenia sinuosa for Human Consumption
    (Springer Int Publ Ag, 2024) Turker, Gulen; Ak, Ilknur; Tas, Elif Cagri
    This study focuses on the mineral content and health risk assessment of the brown seaweed Colpomenia sinuosa. The mineral composition of the seaweed samples (Na, K, Mg, Fe, Cu, Zn, Mn, P, Ni, Pb, Cd, Cr, Al) was investigated from three different Turkish coastal locations: & Idot;zmir Bay (S1), the Strait of & Ccedil;anakkale (S2), and the Sea of Marmara (S3). The mineral contents of samples were analyzed using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) as part of our methodology. It was found that the mineral content varied significantly depending on the location from which the samples were taken. The highest levels of Na, Ca, Mg, Fe, Ni, and Mn were observed in the samples from & Idot;zmir Bay, whereas those from the Sea of Marmara showed elevated levels of P and Zn. The study also revealed the presence of heavy metals, including Pb, Co, Cd, Cr, and Al, in the seaweed. According to hazard index (HI) calculations, adult consumption of this seaweed poses a low health risk, with a hazard index below 1. Various heavy metals have been detected in the seaweed, but their concentrations are not high enough to pose significant health risks, and therefore, the seaweed is safe for human consumption within reasonable limits. Our results suggest that C. sinuosa could be a valuable source of essential minerals for human consumption.
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    On the Origin and Age of the Ariburnu Beachrock, Gelibolu Peninsula, Turkey
    (Tubitak Scientific & Technological Research Council Turkey, 2008) Erginal, Ahmet Evren; Kiyak, Nafiye Gunec; Bozcu, Mustafa; Ertek, Ahmet; Gungunes, Hakan; Sungur, Ali; Turker, Gulen
    The beachrock formation on the Ariburnu coast situated in the Gelibolu Peninsula has been studied by field observation, thin-section interpretation, physicochemical analyses including ICP-AES and SEM/EDS, and OSL dating. These analyses reveal the presence of different amounts of major (Si, Ca, Mg, K, Fe, Al and Na) and trace elements within the beachrock cement with Si (36.2%) and Ca (32.68%) dominating the overall composition. Beachrocks composed of highly-fractured and friable beds reach a total thickness of 80 cm extending from + 60 cm at the uppermost level down to-1 m at their most seaward extent and grade from conglomerate to lithic arkose in vertical section. The total amount of CaCO3 ranges between 59.08% and 36% and the cement consists of high-Mg calcite based on EDS analysis. From SEM examination, four main morphologies were identified in cement material: (1) micritic coatings, (2) cryptocrystalline pore-filling cement, (3) meniscus cement and (4) microbial cement and suggest the presence of marine phreatic conditions with the exception of meniscus bridges, which imply that cementation may have been dominated by carbonate-rich meteoric waters at any successive stage of cementation. Five buried beachrock samples under unconsolidated beach sand were sampled for Optically Stimulated Luminescence (OSL) dating and show that the minimum and maximum ages of beachrock are 1.42 +/- 0.20 ka and 2.28 +/- 0.28 ka BP, respectively.
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    Seasonal variations and human health risk assessment of trace elements in the bivalve ecosystem in the Sea of Marmara
    (Taylor & Francis Ltd, 2022) Yildirim, Pinar; Cardak, Mine; Colakoglu, Serhat; Turker, Gulen; Ormanci, Hasan Basri
    Twelve trace elements were studied in four economically important bivalve molluscs (Mediterranean mussel, manila clam, striped venus clam, and truncated wedge clam) from the southern Marmara Sea for seasonal bioaccumulation and human health risk assessment. According to the findings, Fe and Zn were the most accumulative and element concentrations changed considerably (P < 0.05) between seasons and species. Daily, weekly, monthly intake and target hazard quotients of the trace elements were estimated and compared with maximum limits. The results revealed that consuming these bivalve molluscs from the southern Marmara Sea could be considered safe for human consumption. Nevertheless, further monitoring is needed in order to better follow the development in time of elemental pollution due to increasing environmental pressure on the Marmara Sea basin, together with research on other different bioaccumulative organisms.
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    SULFATED POLYSACCHARIDES FROM GREEN SEAWEED Codium Tomentosum FROM CANAKKALE STRAIT (TURKEY)
    (Parlar Scientific Publications (P S P), 2022) Turker, Gulen; Ak, Ilknur; Basaran, Ihsan; Keklik, Seren
    The polysaccharide extraction and structural characterization of Codium tomentosum from green algae were investigated in this project. After extraction using acetone and dichloromethane, it was purified with a phosphate buffer to obtain a highly purified Codium tomentosum polysaccharide (CTPS). The structure of CTPS was characterized by high-performance liquid chromatography (HPLC), ultraviolet-visible (UV), Fourier transforms infrared (FTIR), and nuclear magnetic resonance ((HNMR)-H-1) spectrum. Additionally, the DPPH free scavenging activity of CTPS was also examined. Our results determined that purified extract includes L-Arabinose, L-Rammnose, L-Fructose, L-Mannose, L-Galactose, and L-Fucose. Furthermore, it was found that CTPS has free radical scavenging activity. The results showed that the polysaccharide obtained from Codium tomentosum could be applied as a potential natural source.
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    The mineral composition of kefir produced from goat and cow milk
    (Wfl Publ, 2013) Turker, Gulen; Kizilkaya, Bayram; Cevik, Nazan
    The mineral composition of kefir produced from cow and goat milk was determined. The macro (Ca, P, K, Na and Mg) and microminerals (Cu, Fe and Zn) were determined both in milk and kefir samples. The Ca/P ratio in kefir produced from cow and goat milk was 1.32. The Ca, P, Mg, Cu and Fe levels were significantly higher in kefir produced from cow milk than those in cow milk; the K and Na concentrations decreased in kefir produced from cow milk (P<0.05) while there was no change in the Zn levels. The concentrations of Ca, P, Na and Mg increased in kefir produced from goat milk while the levels of K and Fe were significantly decreased (P<0.05). No changes were recorded for Cu and Zn levels in goat milk and kefir produced from goat milk. Kefir produced from goat milk was a better source for Ca, P, K, Na and Mg minerals.
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    Thin Film Properties and the Detection Volatile Organic Compounds of C-Methylcalix(4)Resorcinarene
    (Amer Inst Physics, 2018) Sen, Sibel; Capan, Rifat; Turker, Gulen
    C-Methylcalix(4) resorcinarene (CM4RA) molecule fabricated as a thin film using spin coating method was studied for an application as a sensing membrane for the detection of volatile organic compounds. The optical properties of the CM4RA films were elucidated using UV-vis spectroscopy. In addition surface plasmon resonance technique (SPR) was employed to characterize the thin film deposition process of the CM4RA thin film. Sensing properties and the film thickness of these calixresorcinarene spun films were determined from SPR measurement. Sensing measurement results showed a fast response and recovery times with a reversible response in the optical behaviour of thin films of this material. Our results can be concluded that thin film fabricated using CM4RA molecule is demonstrating a good candidate for room temperature vapour sensing application.
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    Utilization on the Removal Cd(II) and Pb(II) Ions from Aqueous Solution Using Nonliving Rivularia bulata Algae
    (Taylor & Francis Inc, 2013) Kizilkaya, Bayram; Akgul, Riza; Turker, Gulen
    In present study, biosorption and elimination of cadmium(II) and lead(II) ions from aqueous solution was evaluated using the algae nonliving biomass (Rivularia bulata) as easy availability, natural origin and biological sorbents. The effect of contact time and metal concentration on the adsorption capacity of metal ions was investigated. The maximum adsorption capacities for Cd(II) and Pb(II) were found to be 26.36 and 34.30mg/g at the optimum conditions, respectively. The experimental data exhibit a good compliance with the pseudo second-order equation for Cd(II) and Pb(II) ions. Langmuir and Freundlich models were also applied to experimental equilibrium data to find the best adsorption isotherm and the values of R-L for Cd(II) and Pb(II) were found to be 0.735 and 0.926, respectively. Weber-Morris and Urano-Tachikawa diffusion models were also applied to experimental equilibrium data. The results are showed that the algae biomass was effectively used as a sorbent for the removal of toxic metal ions from aqueous solutions.