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Öğe Atomic Force Microscopy Study of Living Baker's Yeast Cells(AMER SCIENTIFIC PUBLISHERS, 2011) Mikoliunaite, L.; Makaraviciute, A.; Suchodolskis, A.; Ramanaviciene, A.; Oztekin, Y.; Stirke, A.; Jurkaite, G.Currently, Atomic Force Microscopy (AFM) has a wide range of applications in a variety of disciplines of science and industry including biology and medicine. Despite the maturity of the AFM technique, it is still finding new opportunities in visualization of biological materials and biomolecular processes. The most frequent and ordinary application of AFM is surface topology and morphological studies. This paper describes educational application of AFM in observation of a living cell wall structure. For the following study we have selected Sacchoromyces cerevisiae cells, better known as baker's yeast cells that are available in any supermarket and widely used for fermentation control of food and drinks, and as a leavening agent in baking. The sample preparation and measurements are described. Living yeast cells were prepared in solutions containing glucose or sodium chloride. Proposed AFM based protocol allows the researcher to keep baker's yeast cells alive, and to observe them in air conditions. The experiment is suitable for Master and/or Ph.D. students and is designed to show the main principles of the Bio-AFM operation. In some particular cases, this protocol may be adoptable for bachelor students, who have already completed an extended course in nanotechnology, biotechnology or microbiology. To show educational suitability, the protocol has been tested in the environment of educational laboratory and performed by students studying physics, chemistry, biotechnology and biology.Öğe 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.Öğe Electrochemical formation of polypyrrole-based layer for immunosensor design(ELSEVIER SCIENCE SA, 2014) Ramanavicius, A.; Oztekin, Y.; Ramanaviciene, A.This research represents the evalution of electrochemical formation of conducting polymer polypyrrole-based composite layer, which could be applied in immunosensor design. Polypyrrole (Ppy) layer was formed by mean of potential pulses and bovine leukaemia virus (BLV) protein gp51 (gp51) was entrapped during this synthesis within formed Ppy layer (gp51/Ppy). Some Ppy layer formation aspects were evaluated and mathematical model, which is describing tendencies of gp51/Ppy layer formation, was adopted. The interaction of gp51/Ppy layer with specific antibodies that are present in the blood serum of BLV infected cattle was evaluated by pulsed amperometric detection. (C) 2014 Elsevier B.V. All rights reserved.Öğe Fluorescence study of glucose oxidase self-encapsulated within polypyrrole(ELSEVIER SCIENCE SA, 2012) Ramanavicius, A.; Ryskevic, N.; Kausaite-Minkstimiene, A.; Bubniene, U.; Baleviciute, I.; Oztekin, Y.; Ramanaviciene, A.Glucose oxidase self-encapsulation within polypyrrole was achieved and this process was monitored by the registration of flavin adenine dinucleotide autofluorescence spectra at different periods. The fluorescence of non-encapsulated enzyme was investigated and compared to encapsulated enzyme within polypyrrole. The data presented herein show that at the same experimental conditions the glucose oxidase, if encapsulated within polypyrrole, is more stable than native enzyme. (C) 2012 Elsevier B.V. All rights reserved.Öğe 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.
