Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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  • Master Thesis
    Determination of Cadmium Bound To Whey Proteins by Laser-Induced Breakdown Spectroscopy at Low Pressures
    (2023) Yalçın, Şerife; Yaman, İlayda; Yalçın, Şerife Hanım
    In this thesis study, a dried-droplet LIBS methodology at reduced pressures for determining cadmium in aqueous media and in biological samples has been developed. With the advantage of the signal enhancement effect at reduced pressures, the optimum pressure for Cd detection was determined. Results were justified with the plasma images taken at different pressures. 100 mbar pressure was found as the optimum for most emission lines of Cd. To find the most suitable substrate onto which analyte droplets will be loaded, silicon wafer-based substrates of different coating types and coating thicknesses were studied. Among them, the c-Si substrate was found to show the highest signal enhancement for Cd detection. The performance of the methodology for quantitative analysis of Cd was shown by standard solutions and certified reference water samples. Calibration curves were constructed, and performance characteristics (limit of detection, accuracy, precision) were evaluated. Detection limits in absolute amounts of 6.8 pg and 1.05 pg were obtained at atmospheric and 100 mbar pressures, respectively. The application studies involve the determination of Cd bound to whey proteins. For this purpose, standard protein (BSA) and whey protein extracted from the milk were incubated in standard Cd solutions for several hours and filtered through cut-off filters via centrifugation. The unreacted cadmium in the filtrate and Cd-bound protein in fraction were analyzed separately. It has been shown that dried-droplet LIBS at reduced pressures is a suitable methodology for identifying and determining Cd and Cd bound to proteins with a picogram amount of detection capability.
  • Master Thesis
    Identification and Detection of Cis-Platin Binding Proteins by Laser Induced Breakdown Spectroscopy
    (Izmir Institute of Technology, 2015) Kaya, İbrahim; Yalçın, Şerife; Yalçın, Şerife Hanım
    In this study, an all-optically designed laser plasma spectroscopic technique for rapid identification and detection of cisplatin-binding proteins on electrophoretic gel spots prior to molecular mass spectrometric analysis is demonstrated. For this purpose, human serum albumin, human apo transferrin and horse heart myoglobin standard proteins and protein extracts from HeLa cancer cells were subjected to; incubation with cis-platin solution for several hours. Then, non-reducing polyacrylamide gel electrophoretic separation was applied. Followed by the visualization of proteins in the gel by Coomassie Brilliant Blue staining technique protein spots on the gel were dried between two cellophane sheets and subjected to laser ablation by highly energetic laser pulses. In addition, prior to nr-SDS-PAGE separation cis-platin binding to standard proteins were monitored by ESI-MS with several measurements made in 24 hours of incubation time. Using a Nd:YAG laser at its second harmonic wavelength, 532nm, 10 Hz frequency and 10 ns pulse duration, a micro-plasma was created on dried gel spots. Resulting plasma emission light was collected with collection lenses and transferred to a spectrograph via fiber optic cable. An intensified charge coupled device (ICCD) detector enabled multielemental analysis of platinum binding protein samples. Platinum binding proteins were recognized from the prominent neutral emission line, Pt (I) at 273.3 nm, in a plasma formed by the focused laser pulses on the gel, just in the center or in the vicinity of the electrophoretic spot. Spectral emission intensity of Pt lines from LIBS data has been optimized with respect to laser energy and detector timing parameters. Optimization of LIBS experimental parameters have been studied on polyacrylamide gels soaked in cis-Pt solution for Pt signal. It has been shown that, LIBS is a suitable method for identifying Pt in proteins, in gel medium, with nanogram levels of detection capability. The technique was applied to HeLa (human cervical cancer cells) cells extract for the detection of Pt-binded HSA after standard addition of known amounts of protein.
  • Master Thesis
    Characterization of Ion Implanted Surfaces by Laser Induced Breakdown Spectroscopy, Libs
    (01. Izmir Institute of Technology, 2008) Örer, Sabiha; Yalçın, Şerife
    Laser Induced Breakdown Spectroscopy, LIBS, is a versatile atomic emission spectrometric technique for the determination of the elemental composition of solids, liquids, gases and aerosols with the need for little or no sample preparation.In this study, an optical LIBS system from its conventional parts was designed, constructed and optimized for spectrochemical analysis of solid materials. Specifically, the 2-D elemental distribution of Ge ions on silicon oxide surfaces, prepared by the method of ion implantation, with differing atomic concentrations between 1016 - 1017 ions/cm2 have been investigated by LIBS. For this purpose a Nd: YAG laser operating at the second harmonic wavelength, 532 nm, was used to create a plasma on the material surfaces. Spatially and temporally resolved atomic emission from the luminous plasma was detected by an Echelle spectroctrograph and Intensified Charged Coupled Device (ICCD) detector combination. Spectral emission intensity from the LIBS measurements has been optimized with respect to time, crater size, ablation depth and laser energy. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-Ray Spectroscopy (EDX) have been utilized to obtain crater depth, morphology and elemental composition of the sample material, respectively. LIBS spectral data revealed the possibility of performing 2-D distribution analysis of Ge ions over the silicon oxide substrate at Ge ion concentrations lower than 0.5% (atomic). LIBS as a fast semi-quantitative analysis method with 50.m lateral and 800 nm depth resolutions has been evaluated. In this wok, elemental analysis of some metal surfaces, such as Al and Cu, was also performed by LIBS.Keywords: LIBS, surface analysis, Ge ion implantation, lateral resolution,
  • Master Thesis
    Identification and Detection of Phosphorylated Proteins by Laser Induced Breakdown Spectroscopy
    (Izmir Institute of Technology, 2011) Aras, Nadir; Yalçın, Şerife
    Laser-Induced Breakdown Spectroscopy (LIBS) is an optical atomic emission spectroscopic technique that uses an energetic laser source to generate a luminous plasma. Spectrochemical analysis of the light emitted from the plasma reveals information about the elemental composition of the sample. Phosphorylation is an important regulatory mechanism that activates or deactivates many proteins and enzymes in a wide range of cellular process. Identification and detection of phosphoproteins have a crucial importance in phosphopeptide mapping. This study is based on the assessment of the capabilities and limitations of LIBS as a quick and simple method for in-gel identification and determination of phosphorylated proteins, specifically casein and ovalbumin before mass spectrometric analysis for the elucidation of phosporylation sites. For this purpose, an optical LIBS set-up was constructed from its commercially available parts and the system was optimized for LIBS analysis of polyacrylamide gels. Nd:YAG laser operating at 532 nm wavelength and at 10 Hz frequency was used to create plasma on dry gel surfaces. Emitted light from a luminous plasma was analyzed and detected by an Echelle type spectrograph containing Intensified CCD, detector. With this study, LIBS detection of phosphorous proteins after electrophoretic separation of phosphorylated proteins has been shown, for the first time. After SDS-PAGE gel separation process, phosphoproteins were recognized from prominent P(I) lines (at 253.5 nm and 255.3 nm) in a plasma formed by the focused laser pulses on the gel, just in the center or in the vicinity of the electrophoretic spot. Spectral emission intensity of P(I) lines from LIBS data has been optimized with respect to laser energy and detector timing parameters by using standard Na2HPO4. It has been shown that phosphorylated proteins (casein and ovalbumin in mixture) can be identified by LIBS after both coomassie brilliant blue and silver staining procedures. Technique shows a great promise in microlocal spotting of phosphorylated proteins in gel before MS analysis for the determination of the phosphorylation sites.
  • Master Thesis
    Laser Induced Breakdown Spectroscopic Analysis of Metal Aerosols Generated by Pneumatic Nebuliztion of Aqueous Solutions
    (Izmir Institute of Technology, 2010) Ateş Arıca, Dilek; Yalçın, Şerife
    Laser Induced Breakdown Spectroscopy, LIBS, is an analytical technique used to determine the elemental composition of samples in all forms. In this study, an experimental LIBS system has been designed and constructed for the analysis of metal aerosol particles that are generated by a pneumatic nebulizer. This research provides a basis and preliminary data for the construction of a portable LIBS system to analyze metals in aqueous environments.The aerosol particles generated from the pneumatic nebulizer travel through a sample introduction unit to reach the sample cell in which they interact with the laser beam. The source of light is a Nd:YAG laser at 532 nm, 10 Hz. When the laser beam is focused inside the sample cell, plasma is generated, and the emission containing the spectral information about the sample being analyzed is focused onto the spectrograph and detected by a gated detector. The optimum optical and experimental parameters were systematically investigated.The aqueous analyte solutions were prepared from their salts before introduced into the system. In this work, laser-induced breakdown spectroscopic emissions of Na, Ca, Mg and K aerosols were studied. In single shot mode, the minimum detectable aqueous concentrations were found as 250 ppb, 500 ppb, 400 ppb and 10 mg/L respectively. For 10 shot accumulated analyses in repetitive mode, based on 3. criterion, the detection limit (LOD) was determined as 1 mg/L, 0.6 mg/L, 1.5 mg/L and 16.3 mg/L respectively. The efficiency of the drying unit has been evaluated by particle size measurements. It has been shown that the Na aerosols with particle size of 4.3 .m decreases to 0.5 .m after passing through the membrane dryer unit.