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    Colorimetric Determination of Triacetin in Polymer-Composites
    (2012) Mostovojus, V.; Tucinskas, G.; Ramanaviciene, A.; Öztekin, Y.; Ramanavicius, A.
    Here proposed method enables the determination of triacetin concentrations in non-cured as well as fully cured air-filters and align the results obtained by gravimetric measurements. This method is relatively fast and accurate and it is based on colorimetric determination of triacetin esters converted to hydroxamic acid, which forms purple-red complexes with ferric ion. This reaction is widely used in the determination of various esters for a long time. Practical applicability of this method was demonstrated by triacetin determination in air-filters with limit of determination of 1.2*10-4 M. The experimental data showed linear relationship of calibration curve from solution concentrations in the range from 1.2*10-4 M to 1.2*10-3 M. This method is suitable for the accurate determination of triacetin concentrations during and after the production of filters without the application of expensive equipment. We believe that this method has real potential for the practical application. © 2012 American Scientific Publishers All rights reserved.
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    Fatty acid and dietary fibre content of walnut (Juglans regia L.) varieties grown in Turkey
    (2006) Akça, Yaşar; Kara, Hüseyin; Yazıcıgil, Zafer; Öztekin, Y.; Özgen, Mustafa; Sütyemez, Mehmet; Kalyoncu, Leyla
    Walnuts (Juglans regia L.), as part of healthy diet, contain multiple beneficial components such as unique fatty acid profile and high levels of Vitamin E, fibre and polyphenols. In this work, fatty acid profile and dietary fibre content of new walnut varieties grown in Turkey have been reported. For this purpose walnut samples were collected from 18 different varieties and genotypes grown in Turkey. Four international commercial varieties ('Heartley', Pedro', 'Chandler' and 'Serr'), three Turkish commercial varieties ('Kaman', 'Sebin', 'Bilecik') and 11 new promising new genotypes were evaluated in terms of their fatty acid profile and total dietary fibre contents. Fatty acid composition was determined by gas chromatography and total dietary fibre determination was done by enzymatic-gravimetric procedure. Potential health benefits of newly selected Turkish walnut varieties showed promising results since 6 out of 14 newly selected varieties had more than 70% PUFA and all the new selections except one had more than 10% dietary fibre content.
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    Immunosensor Based on Fluorescence Quenching Matrix of the Conducting Polymer Polypyrrole
    (Springer Heidelberg, 2010) Ramanavicius, A.; Ryskevic, N.; Öztekin, Y.; Kausaite-Minkstimiene, A.; Jursenas, S.; Baniukevic, J.; Kirlyte, J.; Bubniene, U.; Ramanaviciene, A.
    In this study, the combination of autofluorescent proteins and fluorescence quenching polymers was shown to be a design which can increase the selectivity and sensitivity of immunosensors. With this objective, the conducting polymer polypyrrole (Ppy) was used as a matrix for immobilization of proteins, which enables biological recognition of the analyte, and as a fluorescence quencher, which increases the selectivity of fluorescence-based detection. In this study, bovine leukemia virus proteins gp51 were immobilized within the Ppy matrix and formed a polymeric layer with affinity for antibodies against protein gp51 (anti-gp51). The anti-gp51 antibodies are present at high levels in the blood serum of cattle infected by bovine leukemia virus. Secondary antibodies labeled with horseradish peroxidase (HRP) were used as specific fluorescent probes for detection of a particular target, because the fluorescence of HRP was readily detectable at the required sensitivity. The Ppy was used as fluorescent background, because its fluorescence was almost undetectable when excited by near UV light at 325 nm. Moreover the Ppy quenched the fluorescence of some fluorescent agents including fluorescein-5(6)-isothiocyanate (fluorescein), rhodamine B, and HRP by almost 100% when these fluorescent agents were adsorbed on the surface of Ppy. It is predicted that Ppy-induced fluorescence quenching could be used in the design of immunosensors to increase selectivity and sensitivity.