Biomedical subjects

Eunmi Ban

Publications and source records attributed to Eunmi Ban.

8 recordsLinked to original sources

PubMed2006

Analysis of carbamazepine and its active metabolite, carbamazepine-10,11-epoxide, in human plasma using high-performance liquid chromatography.

A sensitive method based on high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection was developed for the determination of carbamazepine (CBZ) and one of its active metabolites, carbamazepine-10,11-epoxide (CBZ-E) in human plasma. CBZ, CBZ-E and the internal standard (IS) 10,11-dihydrocarbamazepine were extracted from human plasma into methyl tert-butyl ether. CBZ, CBZ-E and the IS were successfully separated on an RP C18 column with a mobile phase of acetonitrile:methanol:water (18:19:63, v/v/v) and monitored via UV detection at 210 nm. The calibration curves were linear over the concentration ranges of 0.01-10 microg/mL for CBZ and 0.005-5 microg/mL for CBZ-E in human plasma, respectively. The method displayed excellent sensitivity, precision and accuracy, and was successfully applied to the quantification of CBZ and CBZ-E in human plasma after oral administration of a single 200 mg CBZ CR tablet. This method is suitable for bioequivalence studies following single doses given to healthy volunteers.

Carbamazepine↗

PubMed2006

Sensitive column-switching high-performance liquid chromatography method for determination of propiverine in human plasma.

A sensitive column-switching high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection was developed for the determination of propiverine in human plasma. Propiverine and internal standard, oxybutynin, were extracted from human plasma that had been made basic with 5N sodium hydroxide into methyl tert-butyl ether. The extracted plasma sample was injected onto the HPLC system consisting of a pretreatment column, a concentrating column, and an analytical column, which were connected with a six-port switching valve. The assay was linear in concentration ranges of 2-200 ng/ml for propiverine in human plasma. This method showed excellent sensitivity (a limit of detection of 0.5 ng/ml), good precision and accuracy. This method is suitable for bioequivalence studies following single dose in healthy volunteers.

Benzilates↗

PubMed2004

Narrow-bore high performance liquid chromatographic method for the determination of cetirizine in human plasma using column switching.

An improved column switching high performance liquid chromatographic (HPLC) method was developed for determination of cetirizine in human plasma. Plasma samples were prepared by liquid-liquid extraction using methylene chloride. The samples extracted were initially injected into a clean-up Capcell Pak MF C8 column and the peaks of cetirizine and internal standard were separated to an analytical C18 micro-column via column switching device. This analysis showed highly sensitive and selective results. Also, it was successfully applied to evaluate the pharmacokinetics of cetirizine in human volunteers after single oral administration.

Cetirizine↗

PubMed2004

Development of HPLC method for the determination of levosulpiride in human plasma.

A rapid and simple high performance liquid chromatography (HPLC) method was developed and validated for determination of levosulpiride in human plasma. After extraction with ethylacetate/methylene chloride (5:1, v/v), analysis of levosulpiride in plasma samples was carried out using a reverse phase C18 column with fluorescence detector (maximum excitation at 300 nm and maximum emission at 365 nm) for separation and quantification. A mixture of methanol-20 mM phosphate buffer (pH 3.5, 16:84, v/v) was used as a mobile phase. The method was specific and sensitive with a limit of quantification of 5 ng/ml. This HPLC method was validated by examining the precision and accuracy for inter- and intra-day analysis in the concentration range of 5-150 ng/ml. The relative standard deviation (R.S.D.) in inter- and intra-day validation were 8.16-19.75 and 3.90-11.69%, respectively. In stability tests, levosulpiride in human plasma was stable during the storage and assay procedure. The method was applied to the bioequivalence study of two levosulpiride tablet formulations (25 mg) after a single oral administration.

Chromatography, High Pressure Liquid↗

PubMed2003

New method for analyzing the nitrite level in PC12 cells using capillary electrophoresis.

Nitric oxide (NO) is a gaseous molecule shown to have signal transmitter properties in organisms. Direct measurement of NO in physiological conditions has been difficult due to its short lifetime and low concentration. Nitrite has been used as a marker for NO formation in biological systems. Capillary electrophoresis (CE) has been recently used to measure nitrite in biological fluids. The purpose of this study is to analyze nitrite in PC12 cells (pheochromocytoma cell line) using CE. Optimal CE performance was employed with 150 mM Tris-phosphate, 6 microM hexadecyltrimethyammonium chloride buffer at pH 7.0 and a fused-silica column of 57 cm x 75 microm I.D. The signal was measured with a UV detector at 214-nm wavelength and negative potential of 10 kV was applied for nitrite analysis. Under the optimum conditions, we monitored the changes in the concentration of the nitrite levels through synergistic stimulation of tumor necrosis factor alpha plus gamma-interferon in PC12 cells.

Animals↗

PubMed2003

Analysis of vasopressin using capillary electrophoresis with laser-induced fluorescence detector based on competitive immunoassay.

A competitive immunoassay based on CE-LIF has been developed for the determination of vasopressin in biological mixtures. Vasopressin participates in the hormonal control of water metabolism and the constriction of arterioles in humans. Thus, detection of vasopressin is important in diagnosing pathological conditions and physiological water metabolism. The peptides were fluorescently tagged with FITC and purified by HPLC. The purified product was then mixed with the cerebrospinal fluid sample followed with the addition of anti-vasopressin antibody. It was possible to separate antibody-bound and free FITC-tagged vasopressin within 10 min by CE-LIF analysis using uncoated fused-silica capillary with high reproducibility.

Chromatography, High Pressure Liquid↗

PubMed2002

Direct monitoring of the expression of the green fluorescent protein-extracellular signal-regulated kinase 2 fusion protein in transfected cells using capillary electrophoresis with laser-induced fluorescence detection.

Proper subcellular localization of the extracellular signal-regulated kinases (ERKs) is important in regulating physiological functions such as proliferation and differentiation in the pheochromocytoma cell line (PC12 cells). Thus, a direct visualization method is necessary to observe ERK localization within the cell or in crude cellular extracts. In this paper, a determination method was established for the detection of ERK2 localization in PC12 cells using green fluorescent protein (GFP) and capillary electrophoresis with laser-induced fluorescence (LIF). GFP as a reporter or labeling tag for gene expression in biochemistry and cell biology was used for the detection of ERK2 localization in PC12 cells. PC12 cells were transfected with GFP-ERK2 plasmid construct that was inserted into a variant GFP gene (enhanced green fluorescent protein), and successfully expressed GFP-ERK2 fusion proteins. GFP-ERK2 fusion proteins were detected within 5 min by CE analysis using an uncoated fused-silica capillary with LIF. Optimum conditions for GFP-ERK2 fusion proteins detection were 100 mM 3-(cyclohexylamino)-1-propanesulfonic acid buffer containing 100 mM sodium dodecylsulfate, pH 11, running at 20 degrees C. This result offers new opportunity in screening for the determination of localization of intracellular components, protein-protein interactions and kinase activity within the cells.

Animals↗

PubMed2002

Determination of protein phosphorylation by extracellular signal-regulated kinase using capillary electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry.

Extracellular signal-regulated kinase (ERK) is a key regulatory enzyme mediating cell responses to mitogenic stimulation and is one of the key components in linking growth factor receptor activation to serine/threonine protein phosphorylation processes. Phosphorylation reaction by ERK plays an important role in many signal transduction pathways. ERK phosphorylates numerous substrates such as MBP, microtubule-associated protein 2 (MAP2) and nuclear protein. In particular, MBP is a substrate commonly employed for the detection of ERK activity and contains the consensus primary sequence PRT97P. In this paper, we compared the degree of the phosphorylation reaction of MBP substrate peptides by ERK with the three different MBP substrate peptides, MBP1(KNIVTPRTPPPSQGK), MBP2(VPRTPGGRR) and MBP3(APRTPGGRR) in order to select an efficient substrate peptide for phosphorylation reaction by ERK. The results showed that the MBP3 peptide is the most efficient substrate for phosphorylation reaction by ERK. Using MBP3 peptide, the phosphorylation reaction of MBP by ERK was monitored with both matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and capillary electrophoresis (CE). Our results demonstrate the feasibility of the CE method, the method being a simple and reliable technique in determining and characterizing various kinds of enzyme reaction especially including kinase enzymes.

Amino Acid Sequence↗