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    Polymethacryloyl-L-Phenylalanine [PMAPA]-based monolithic column for capillary electrochromatography
    (Oxford Univ Press Inc, 2019) Derazshamshir, Ali; Aşır, Süleyman; Göktürk, Ilgım; Ektirici, Sisem; Yılmaz, Fatma; Denizli, Adil
    The ability to detect catecholamines (CAs) and their metabolites is vital to understand the mechanism behind the neuronal diseases. Neurochemistry aims to provide an improved pharmacological, molecular and physiological understanding of complex brain chemistries by analytical techniques. Capillary electrophoresis (CE) is one such analytical technique that enables the study of various chemical species ranging from amino acids and peptides to natural products and drugs. CE can easily adapt the changes in research focus and in recent years remains an applicable technique for investigating neuroscience and single cell neurobiology. The prepared phenylalanine-based hydrophobic monolithic column, Polymethacryloyl-L-phenylalanine [PMAPA], was used as a stationary phase in capillary electrochromatography to separate CAs that are similar in size and shape to each other including dopamine (DA) and norepinephrine (NE) via hydrophobic interactions. Separation carried out in a short period of 17 min was performed with the electrophoretic mobility of 5.54 x 10(-6) m(2) V-1 s(-1) and 7.60 x 10(-6) m(2) V-1 s(-1) for DA and NE, respectively, at pH 7.0, 65% acetonitrile ratio with 100 mbar applied pressure by the developed hydrophobic monolithic column without needing any extra process such as imprinting or spacer arms to immobilize ligands used in separation.
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    Selective recognition of nucleosides by boronate affinity organic-inorganic hybrid monolithic column
    (Elsevier, 2021) Ektirici, Sisem; Göktürk, Ilgım; Yılmaz, Fatma; Denizli, Adil
    Boronic acids are important ligands used to selectively recognize and enrich compounds containing cis-diol groups such as nucleosides. In the present study, organic-inorganic hybrid [POSS-MAH-BPA] monolithic column was prepared for the first time in the literature as a new boronate affinity system for the recognition of nucleosides. The selectivity of the [POSS-MAH-PBA] boronate affinity monolithic column for the recognition of cis-diol containing adenosine nucleoside from its analogue molecule of deoxyadenosine triphosphate, dATP, noncis-diol containing compound was investigated both by UV and HPLC studies. When the relative selectivity coefficients are compared, the [POSS-MAH-PBA] boronate affinity monolithic column is 4.25 times more selective for adenosine than [POSS-MAH] monolithic column. Besides, to determine endogenous nucleosides in biological fluids, which may serve as non-invasive cancer biomarkers, nucleosides were spiked into the urine solutions and passed through the [POSS-MAH-PBA] boronate affinity monolithic column, and the nucleosides were confirmed by HPLC. The adenosine recognition capability of the [POSS-MAH-PBA] boronate affinity monolithic column with an average enrichment factor of 48.9-fold was apparently superior to that of the [POSSMAH] monolithic column. Methacryl Polyhedral Oligomeric Silsesquioxanes (POSS-MA) with nano-sized stable 3-dimensional architectures provided the advantage of being used as an adsorbent for the monolithic structure by providing high surface area, 507.60 m(2)/g, and enabling vinyl groups to function with amino acid-based MAH monomers capable of providing electrons to coordinate PBA. Recovery results of more than 90% for adenosine showed that the [POSS-MAH-PBA] boronate affinity monolithic column could be a promising adsorbent for selective adsorption of cis-diol containing compounds such as nucleosides.
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    Separation of histidine enantiomers by capillary electrochromatography with molecularly imprinted monolithic columns
    (Wiley-V C H Verlag Gmbh, 2020) Şarkaya, Koray; Aşır, Süleyman; Göktürk, Ilgım; Ektirici, Sisem; Yılmaz, Fatma; Yavuz, Handan; Denizli, Adil
    In this study, we aimed to separate the enantiomeric forms of d,l-histidine, one of the essential amino acids, through molecular imprinted monolithic capillary electrochromatography columns prepared using hydrophobic N-methacryloyl-(l)-phenylalanine methyl ester as the functional monomer, and l-histidine as the template molecule. We investigated the effect of monomer ratio, temperature, template molecule mole ratio, crosslinker ratio, and porogen ratio to improve the permeability properties of the monolithic column. Characterization studies of the column were evaluated by attenuated total reflectance-Fourier transform infrared spectroscopy, scanning electron microscopy, and Brunauer-Emmett-Teller analysis. The chromatographic performance of the column was investigated using alkylbenzene-derived compounds. We evaluated some parameters to determine the optimum conditions for electrochromatographic studies such as electric field, organic solvent ratio, and pressure effect. The calculated imprinting factor (2.18) proved that the l-histidine imprinted amino acid-based monolithic column separated d,l-histidine molecules efficiently (percent relative standard deviation < 1.5) from each other using molecular imprinting technique with high-resolution values (resolution value > 1.5). As a result, selective d,l-histidine separation was achieved in less than 10 min at pH 7.0 without using a ligand or extra modification step for the first time.