• Journal of Microbiology and Biotechnology
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• 제19권1호
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• pp.51-54
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• 2009

Myxobacteria, Gram-negative soil bacteria, are a well-known producer of bioactive secondary metabolites. Therefore, this study presents a methodological approach for the high-throughput screening of secondary metabolites from 4 wild-type Myxococcus xanthus strains. First, electrospray ionization mass spectrometry (ESI-MS) was performed using extracellular crude extracts. As a result, 22 metabolite peaks were detected, and the metabolite profiling was then conducted using the m/z value, retention time, and MS/MS fragmentation pattern analyses. Among the peaks, one unknown compound peak was identified as analogous to the myxalamid A, B, and C series. An analysis of the tandem mass spectrometric fragmentation patterns and HR-MS identified myxalamid K as a new compound derived from M. xanthus. In conclusion, LC-MS/MS-based chemical screening of diverse secondary metabolites would appear to be an effective approach for discovering unknown microbial secondary metabolites.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 총회 및 춘계학술발표회
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• pp.196-200
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• 2003

A gas chromatography/mass spectrometric assay method was developed for the simultaneous determination of ethylene glycol monomethyl ether (EGME) and diethylene glycol monomethyl ether (DEGME) in spilled aviation fuels. Ethylene glycol monobutyl ether (EGBE) and ethylene glycol monoethyl ether (EGEE) were used as internal standard and surrogate, respectively. The sample preparation consists of back-extraction with 7 mL of methylene chloride after extraction of 50 mL of fuel with 2 mL of water. The extract was concentrated to dryness and dissolved with 100L of methanol and analyzed by CC-MS (SIM). The peaks had good chromatographic properties by using semi-polar column and the extraction of these compounds from fuel also gave high recoveries of 75 and 85 % with small variations for EGME and DEGME, respectively. Method detection limits were 1.3 ng/mL for EGME and 1.0 ng/mL for DEGME in spilled fuel. The method may be useful for fuel-type differentiation between kerosene and JP-8, which may originate from the storage tank.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1527-1534
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• 2010

The conventional peptide modification process of guanidination, in which the amino groups of lysine residues are converted to guanidino groups using O-methylisourea to create more basic homoarginine residues, is often used to improve the signal intensity of lysine-containing peptides in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Here, we used three different protease enzymes (trypsin, Lys-C, and Glu-C) to evaluate the effects of guanidination on the MS signals of two enzymatically digested proteins. Horse heart myoglobin and bovine serum albumin were guanidinated either before or after digestion with trypsin, Lys-C, or Glu-C. The resulting peptides were subjected to MALDI-MS, and signal intensities and sequence coverage were systematically evaluated for each digest. Guanidination prior to Glu-C digestion improved sequence coverage for both proteins. For myoglobin, guanidination before enzymatic digestion with trypsin or Lys-C also enhanced sequence coverage, but guanidination after enzymatic digestion enhanced sequence coverage only with Lys-C. For albumin, guanidination either before or after Glu-C digestion increased sequence coverage, whereas pre- or post-digestion guanidination decreased sequence coverage with trypsin and Lys-C. The amino acid composition of a protein appears to be the major factor determining whether guanidination will enhance its MALDI-MS sequence coverage.

• Bulletin of the Korean Chemical Society
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• 제28권5호
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• pp.745-750
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• 2007

An isotope dilution-liquid chromatography/tandem mass spectrometric method was developed as a candidate reference method for the accurate determination of folic acid in infant milk formula. Sample was spiked with 13C5-folic acid and then extracted with phosphate buffer (pH 6) solution. The extract was further cleaned up by deproteinization followed by a C18 solid-phase extraction cartridge. The extract was analyzed by using LC/ ESI/MS/MS with selectively monitoring the collisionally induced dissociation channels of m/z 442 → m/z 295 and m/z 447 → m/z 295, which are the neutral glutamyl loss from the [M+H]+ ions of folic acid and 13C5-folic acid, respectively. LC/MS/MS chromatograms showed substantially reduced background from chemical noises compared to LC/MS chromatograms. Repeatability and reproducibility studies showed that the LC/MS/ MS method is a reliable and reproducible method which can provide less than 1.5 relative percentage of method precision.

• 천문학회보
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• 제37권2호
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• pp.114.1-114.1
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• 2012

To measure the magnetic field strength in the solar corona, we examined 10 fast (>1000 km/s) limb coronal mass ejections (CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and magnetic field strength in the height range 3-15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49-3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47-1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the magnetic field strength is in the range 6-105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of two, the Alfven speeds and the magnetic field strengths are consistent in both methods; and (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates.

• Molecules and Cells
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• 제41권2호
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• pp.150-159
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• 2018

Animals use their odorant receptors to receive chemical information from the environment. Insect odorant receptors differ from the G protein-coupled odorant receptors in vertebrates and nematodes, and very little is known about their protein-protein interactions. Here, we introduce a mass spectrometric platform designed for the large-scale analysis of insect odorant receptor protein-protein interactions. Using this platform, we obtained the first Orco interactome from Drosophila melanogaster. From a total of 1,186 identified proteins, we narrowed the interaction candidates to 226, of which only two-thirds have been named. These candidates include the known olfactory proteins Or92a and Obp51a. Around 90% of the proteins having published names likely function inside the cell, and nearly half of these intracellular proteins are associated with the endomembrane system. In a basic loss-of-function electrophysiological screen, we found that the disruption of eight (i.e., Rab5, CG32795, Mpcp, Tom70, Vir-1, CG30427, Eaat1, and CG2781) of 28 randomly selected candidates affects olfactory responses in vivo. Thus, because this Orco interactome includes physiologically meaningful candidates, we anticipate that our platform will help guide further research on the molecular mechanisms of the insect odorant receptor family.

• 한국환경농학회지
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• 제30권4호
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• pp.432-439
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• 2011

BACKGROUND: An official analytical method was developed to determine etofenprox residues in agricultural commodities using high-performance liquid chromatography (HPLC). METHODS AND RESULTS: The etofenprox residue was extracted with acetone from representative samples of five raw products which comprised rice grain, apple, mandarin, cabbage, and soybean. The extract was then serially purified by liquid-liquid partition and Florisil column chromatography. For rice and soybean samples, acetonitrile/n-hexane partition was additionally coupled to remove nonpolar lipids. Reversed phase HPLC using an octadecylsilyl column was successfully applied to separate etofenprox from co-extractives. Intact etofenprox was sensitively detected by ultraviolet absorption at 225 nm. Recovery experiment at the quantitation limit validated that the proposed method could apparently determine the etofenprox residue at 0.02 mg/kg. Mean recoveries from five crop samples fortified at three levels in triplicate were in the range of 93.6~106.4%. Relative standard deviations of the analytical method were all less than 10%, irrespective of crop types. A selected-ion monitoring LC/mass spectrometry with positive atmospheric-pressure chemical ionization was also provided to confirm the suspected residue. CONCLUSION(s): The proposed method is simple, rapid and sensitive enough to be employed in routine inspection or monitoring of agricultural products for the etofenprox residue.

• 분석과학
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• 제15권6호
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• pp.574-579
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• 2002

탄수화물 형태의 당뇨치료제인 acarbose 및 그 대사체를 LC/MS를 사용하는 간편하고 감도 좋은 분석방법을 개발하였다. 혈장시료를 주사기 필터로 거른후 다른 시료전처리과정 없이 LC/MS에 직접 주입하여 분석하였다. Acarbose에 대한 검정곡선은 $0.1{\sim}10{\mu}g/m{\ell}$ 농도범위에서 $r^2=0.9963$의 선형성을 나타내었다. ${\alpha}$-Amylase와 ${\beta}$-amylase를 사용한 in vitro 배양 시험을 통해서 생성된 대사체 component-I과 component-II도 정성적으로 확인 가능하였다. 이러한 LC/MS 분석법은 acarbose의 약동력학적 연구는 물론이며 다른 탄수화물 형태 약물의 연구에도 활용이 가능할 것이다.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.223.2-223.2
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• 2003

A rapid, sensitive and selective liquid chromatography-tandem mass spectrometric (LC/MS/MS) method for the determination of eupatilin in human plasma was developed. Eupatilin and internal standard, (S)-[N-3-(4-(2-(1-methyl-5-tetrazolyl)-pyridine-5-y1)- 3-fluorophenyl)-2-oxo-5-oxazolidinyl]methyl acetamide (DA-7867) were extracted from human plasma by liquid-liquid extraction and analyzed on a phenyl-hexyl column with the mobile phase of acetonitrile-ammonium formate (10 mM, pH 3.0) (60:40, v/v). (omitted)

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2005년도 가을학술대회
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• pp.150-153
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• 2005

A gas chromatography/electron impact mass spectrometric assay method was developed for the determination of Hb-adduct, 2-(hydroxyethyl)valine (HEVal), of ethylene oxide(EO). Globin was separated from hemoglobin by acid iso-propanol and ethyl acetate, then HEVal was isolated as PFPITH-HEVal by Edman degradation. PFPITH-HEVal was silylated with N-methyl-N-(tert-butyl-dimethylsilyl)trifluoroacetamide(MTBDMSTFA)-NH4I (1000:4) under catalysis of dithioerythritol. The detection limit of the assay was 5.8 pmol/g based upon assayed hemoglobin of 0.1g. Two groups of mice were exposed to EO for 0.5 and 1.0 hr/day, respectively at 400ppm during 4 weeks. As the result, the adduct levels increased according to the exposure time with the linearity of 0.7011 and 0.8914, respectively, HEVal was very valuable as biomarker for the exposure of EO. In human, HEVal was analyzed until 8.33 pmol/mg.