Jongsei Park

Erythropoietin: physico- and biochemical analysis.

A hormone, erythropoietin, mainly produced in adult kidneys and fetal livers, acts on bone marrow erythroid progenitor cells to regulate the production of erythrocyte in mammals. As a result, the oxygen carrying capacity of blood increases and the increased oxygen supply raises the cardiac function and physiological working capacity. Erythropoietin is possibly misused by athletes in sports for the purpose of improving performance. Presently there is no discernible and specific method to identify erythropoietin administration for doping control. To address this practical problem, this paper presents a summary of the applications of analytical biotechnology, especially the structural characterization of erythropoietin.

Survey of natural occurrence of trichothecene mycotoxins and zearalenone in Korean cereals harvested in 1992 using gas chromatography/mass spectrometry.

For the survey of the natural occurrence of trichothecene mycotoxins, produced by species of fungi imperfecti such as Fusarium and Trichothecium, a sensitive analytical method was developed for the simultaneous detection and quantitation of the major trichothecene mycotoxins, viz. T-2 toxin (T-2), HT-2 toxin (HT-2), nivalenol (NIV), fusarenon-X (F-X), deoxynivalenol (DON), 3-acetyl deoxynivalenol (3-Ac DON), and zearalenone (ZEN), using gas chromatography/mass spectrometry-selected ion monitoring (GC/MS-SIM) mode after trimethyl silyl derivatization. The incidence of NIV and DON in 30 barley samples were 93% and 67%, respectively; the average contents of NIV and DON in positive samples were 390 ng/g (range 40-2038) and 106 ng/g (range 5-361) respectively. In 15 maize samples, the incidences of NIV and DON were 53% and 93% respectively and the average contents were 168 ng/g and 145 ng/g, respectively. These results suggest that NIV and DON were the major contaminating trichothecene mycotoxins in Korean barley and maize samples harvested in 1992.

Urinary polyamine evaluation for effective diagnosis of various cancers

With a newly modified analytical method, the concentrations of free and acetylated urinary polyamines were simultaneously determined in a control group (32 cases) and patients with various types of cancers (104 cases, 20 males and 84 females) by gas chromatography-nitrogen-phosphorus detection. Significant concentration differences between normal subjects and various cancer patients were found. The various types of cancers (advanced gastric carcinoma, ovarian cancer, acute myelocyte leukemia, non-Hodgkins lymphoma) gave unique patterns of urinary polyamine profile as well as significant differences of concentration. To indirectly evaluate the possible involvement of enzymes, precursor-to-product concentration ratios were compared between controls and patients with various types of cancers.

Design and synthesis of α,β-unsaturated carbonyl compounds as potential ACE inhibitors

The α,β-unsaturated amide that is incorporated into the basic structural frame of a simple substrate molecule of angiotensin converting enzyme was found to serve as a Michael acceptor for the catalytic carboxylate of Glu-127, inhibiting the enzyme irreversibly.

Capillary gas chromatography of acidic non-steroidal antiinflammatory drugs as tert.-butyldimethylsilyl derivatives

Abstract The quantitative conversion of 26 acidic non-steroidal anti-inflammatory drugs (NSAIDs) simultaneously to their corresponding tert. -butyldimethylsilyl (TBDMS) derivatives in a single step was examined. The NSAIDs dissolved in triethylamine were silylated with N-methyl-N-( tert. -butyldimethylsilyl)trifluoroacetamide in isooctane at room temperature for 30 min and subsequently analysed by capillary gas chromatography and gas chromatography—mass spectrometry. The TBDMS derivatives were eluted as untailed sharp peaks and the characteristic [M — 57] + ions in the mass spectra permitted their rapid confirmation. The temperature-programmed retention index ( I ) sets measured on a DB-5 and DB-17 dual-capillary column system were characteristic of each NSAID to be used for the rapid identification by computer I matching. The derivatization yields of the NSAIDs studied were linear in the range 10–120 μg with high overall precisions. The method provided simultaneous screening and accurate confirmation of each drug when applied to serum samples spiked with NSAIDS.

Localization of the Epitope in Methamphetamine and Its Antibody Use for the Detection of Methamphetamine and Benzphetamine by Polarization Fluoroimmunoassay

An antibody was prepared, using a four carbon-bridged methamphetamine molecule as an immunogen in order to develop a polarization fluoroimmunoassay for urine screening of methamphetamine and benzphetamine. Also, its binding characteristics were investigated to locate epitope sites of methamphetamine. The study showed that the antibody was highly capable of eliciting a polarization fluoroimmunoassay response. However, the detection limit was much greater for benzphetamine (0.05 ppm) than for methamphetamine (0.2 ppm) and weakly antibody binding was found with methamphetamine. This difference in sensitivity may reflect the similarity of benzphetamine to the immunogen used to produce the antibody. Both benzphetamine and the immunogen have a tertiary amine attached to a carbon bridges whereas methamphetamine has only a secondary amine and amphetamine has a primary amine group. The difference of cross-reactivity data between phenylethylamine drugs and beta-hydroxyl phenylethylamine drugs indicates that the beta-carbon position have a major influence on the antibody interaction. Thus, the substitution of hydroxyl group on beta-carbon resulted in virtually no antibody affinity, even if a tertiary amine or secondary amine group was present in the molecule. This suggests that the beta-carbon chain plays a primary role as the epitope site with cooperative binding site of tertiary amine or secondary amine in alpha-carbon position. A hydroxyl group at the beta-carbon position plays an important inhibitory role to the antibody binding.

Identification of a pyrovalerone metabolite in the rat by gas chromatography-mass spectrometry and determination of pyrovalerone by gas chromatography-nitrogen-phosphorus detection.

Pyrovalerone and its hydroxylated metabolite have been identified by gas chromatography-mass spectrometry in rat urine and plasma. A sensitive gas chromatographic method for the quantitative analysis of pyrovalerone in rat urine and plasma is described. The method also permits the quantitative monitoring of the urinary excretion of the drug and its metabolite. Pyrovalerone and its hydroxylated metabolite are detected up to 18 h after a single oral administration to the rat at a dose of 20 mg/kg.

Voltage noise and vortex states in YBa2Cu3Ox films

Abstract The voltage-noise measurements in epitaxial YBa 2 Cu 3 O x films have been extended to the case of a high magnetic field. In a magnetic field, two noise peaks, one from the vortex motion and the other from the resistance fluctuations, were observed. The location of the vortex-motion induced peak was found to be well above the vortex-glass transition. Our interpretation is that a noise peak manifests itself in a crossover from the pinned vortex-liquid to the unpinned vortex-liquid state.

Analysis of phosphopeptides by capillary electrophoresis and matrix-assisted laser-desorption ionization-time-of-flight mass spectrometry

Abstract Capillary electrophoresis was used for the qualitative as well as quantitative analysis of phosphopeptides. Three pairs of phosphorylated peptides and non-phosphorylated analogues were analyzed by capillary electrophoresis. Each sequence of phosphopeptides contained one phosphoserine, phosphothreonine or phosphotyrosine residue. The capillary electrophoresis analyses were performed in a fused-silica capillary 50 μm in internal diameter and 100 cm in length. For detection of analyte peptides, absorbance at 214 and 229 nm wavelength in the UV region was measured. To obtain the best resolution, the concentration of analyte and the pH of the electrolyte buffer were optimized. Matrix-assisted laser-desorption ionization-time-of-flight mass spectrometry was used to confirm the molecular mass of the phosphorylated peptides and non-phosphorylated analogues. For quantitative analysis of the phosphorylated peptides using capillary electrophoresis, the linearity of the response of the absorbance at 214 nm was examined. The response of the absorbance for the phosphorylated peptides was linear; thus this validates the method for quantifying phosphopeptides using capillary electrophoresis. The results of our study show that capillary electrophoresis can be widely applied to analyze and characterize many biologically active phosphopeptides and phosphoproteins.

A new visual enzyme immunoassay of methamphetamine using linear water-soluble polyelectrolytes

A new visual enzyme immunoassay (EIA) technique has been developed. Oppositely charged synthetic linear water-soluble polyelectrolytes (poly-N-ethyl-4-vinyl-pyridine as polycation and polymethacrylate as polyanion) were used as carriers for reagent immobilization. The ability of these molecules to form an insoluble complex was applied for the separation of bound and free components of the immunoassay reaction mixture. This approach was realized in methamphetamine visual EIA. In the first stage of the assay two specific reactions took place during incubation of the analytical reagents with the probe to be analyzed: (1) competition between methamphetamine and hapten conjugated with peroxidase for the interaction with specific antibodies and (2) interaction of these antibodies with the protein A-polymethacrylate conjugate. As a result of these reactions the (polyanion-protein A)-antibody-(hapten-peroxidase) complex was formed. Then the reaction mixture was filtered through an Ultrabind membrane (0.45 microns) with adsorbed poly-N-ethyl-4-vinylpyridine, and the immunological complexes were immobilized to the membrane by electrostatic interaction. The level of peroxidase binding on the membrane was measured by diaminobenzidine substrate. The system described was optimized to achieve both high rapidity (20 min) and an appropriate sensitivity (0.4 micrograms/ml) for methamphetamine assay.