Yazar "Ipek, Semih Latif" seçeneğine göre listele

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    An impedimetric determination of zearalenone on MIP-modified carboceramic electrode
    (Pergamon-Elsevier Science Ltd, 2024) Kucuk, Dilruba; Uner, Guelcan; Ipek, Semih Latif; Caglayan, Mustafa Oguzhan; Ustundag, Zafer
    Zearalenone (ZEN) is a mycotoxin that poses significant risks to human and animal health due to its mutagenic, immunosuppressive, and carcinogenic properties. This study presents a novel analytical method for detecting ZEN using electrochemical impedance spectroscopy (EIS) combined with a molecularly imprinted polymer (MIP). ZEN, used as the template molecule, was incorporated into polypyrrole on screen-printed electrodes (SPE), and a ZEN-sensitive MIP sensor was created through template removal. The modified sensor surfaces were characterized by EIS and scanning electron microscopy (SEM). An impedimetric MIP sensor for ZEN was developed, offering a detection range from 1 pM to 500 pM. The method's limit of detection (LOD) was established at 1 pM (0.3 pg/mL) with a signal-to-noise ratio of 3 (S/N = 3). The method demonstrated high precision and accuracy, with a maximum relative standard deviation (RSD) of less than 4.4% at a 95% confidence level, and relative error (RE) values ranging from -0.8% to -2.7%. The selectivity of the developed MIP sensor was evaluated using ochratoxin A, ochratoxin B, and aflatoxin B1, with no significant interference observed. ZEN recovery from spiked samples was between 95% and 105%, indicating that the method was successfully applied to grain samples, including corn, rice, and wheat.
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    Bacterial diversity and lysozyme activity of raw buffalo milk: a case study on milk collection tanks from selected farms
    (Taylor & Francis Ltd, 2024) Ipek, Semih Latif
    Approximately 15% of the milk produced in the world comes from buffaloes. In this study, the microbiome and lysozyme activities of buffalo milk in the Tepecik region were investigated. Samples were taken from ten different farms and analyzed. The average lysozyme activities were 59.858 units x 10-3/mL. Taxonomic analyses showed that Lactococcus, Acinetobacter, Moraxella, Streptococcus, Anoxybacillus, Aeromonas generally constituted the dominant bacterial groups. Low lysozyme activities and Staphylococcus aureus and Micrococcus luteus values showed that the milk taken from ten farms was mastitis free. The presence of Acinetobacter, Moraxella, Anoxybacillus and Aeromonas bacteria, which pose a pathogenic risk for milk, indicates that proper sanitation of milking machines are required. Pseudomonas, a psychrophilic bacterium, was not detected in most products, but was detected in very small amounts in some products. This work sheds a light on future studies that covers lysozyme activity measurement combined with DNA sequencing for food safety in dairy industry.
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    Cytotoxic Effect of L-Methioninase from Brevibacterium linens BL2 in Combination with Etoposide against Glioblastoma Cells
    (Mdpi, 2023) Ipek, Semih Latif; Ozdemir, Meryem Damla; Gokturk, Dilek
    L-methioninase degrades methionine, which is essential in methionine-dependent cancer cells, resulting in specific cell death. Normal cells can synthesize their own methionine amino acids even in the absence of exogenous methionine. This selective targeting of cancer cells makes L-methioninase a promising therapeutic candidate for cancer. In this study, L-methioninase was partially purified from Brevibacterium linens BL2. The specific activity of the enzyme was found as 3.055 units/mg. IC50 values (24 h) of the enzyme were 5.792 units/mL for U87MG cell line and 5.215 units/mL for T98G cell line. When L-methioninase and etoposide were used in combination, synergistic cytotoxic and cell migration inhibition effects on U87MG and T98G cells alongside decreased cytotoxic activity on the Mouse Embryonic Fibroblast and HaCaT cells compared to etoposide alone were observed. Additionally, colony numbers of U87MG cells were significantly reduced by L-methioninase and etoposide administration after 21 days of incubation. Furthermore, L-methioninase suppressed the expression levels of survivin and c-Myc while increasing the expression level of Caspase-3 in both glioblastoma cell lines. These effects were enhanced when etoposide was used in combination with etoposide. This investigation reveals that the L-methioninase enzyme not only exhibited cytotoxic effects on U87MG and T98G cells but also enhanced the anti-proliferative effects of etoposide when used in combination while also demonstrating fewer adverse effects on normal cells.