• Journal of Microbiology and Biotechnology
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• 제17권6호
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• pp.952-959
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• 2007

His-His-Leu (HHL), a tripeptide derived from a Korean soybean paste, is an angiotensin-I-converting enzyme (ACE) inhibitor. We report here a method of producing this tripeptide efficiently by expressing tandem multimers of the codons encoding the peptide in E. coli and purifying the HHL after hydrolysis of the peptide multimers. The HHL gene, tandemly multimerized to a 40-mer, was ligated with ubiquitin as a fusion gene (UH40). UH40 was inserted into vector pET29b; the UH40 fusion protein was then produced in E. coli BL21. The recombinant UH40 protein was purified by cation-exchange chromatography with a yield of 17.3mg/l and analyzed by matrixassisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry and protein N-terminal sequencing. Leucine aminopeptidase was used to cleave a 405-Da HHL monomer from the UH40 fusion protein and the peptide was purified using reverse-phase high-performance liquid chromatography (HPLC) on a C18 HPLC column, with a final yield of 6.2mg/l. The resulting peptide was confirmed to be HHL with the aid of MALDI-TOF mass spectrometry, glutamine-TOF mass spectrometry, N-terminal sequencing, and measurement of ACE inhibiting activity. These results suggest that our production method is useful for obtaining a large quantity of recombinant HHL for functional antihypertensive peptide studies.

• Mass Spectrometry Letters
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• 제10권3호
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• pp.88-92
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• 2019

A sensitive analytical method of rhodanthpyrone A in rat plasma was developed using a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Rhodanthpyrone A and rhodanthpyrone B (internal standard) in rat plasma were extracted by a liquid-liquid extraction method with ethyl acetate. This extraction method gave results in high and reproducible extraction recovery in the range of 73.75-79.90% with no interfering peaks around the peak elution time of rhodanthpyrone A and B. The standard calibration curves for rhodanthpyrone A ranged from 0.5 to 2000 ng/mL were linear with $r^2$ > 0.994 and the inter- and intra-day accuracy and precision and the stability were within acceptance criteria. Using this validated analytical method, pharmacokinetics of rhodanthpyrone A following intravenous and oral administration of rhodanthpyrone A at doses of 2 mg/kg and 30 mg/kg, respectively, were investigated. Rhodanthpyrone A in rat plasma showed multi-exponential elimination pattern with high clearance and volume of distribution values. The absolute oral bioavailability of this compound was calculated as 3.7%. Collectively, the newly developed sensitive LC-MS/MS analytical method of rhodanthpyrone A could be successfully applied to investigate the pharmacokinetic properties of this compound and would be useful for the further studies on the efficacy, toxicity, and biopharmaceutics of rhodanthpyrone A.

• 분석과학
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• 제30권2호
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• pp.102-111
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• 2017

Here we reported a methodology for identification of triacylglycerols (TAGs) and diacylglycerols (DAGs) in coix seed by preparative thin layer chromatography (prep-TLC) and non-aqueous reversed-phase liquid chromatography (NARP LC)-atmospheric pressure chemical ionization (APCI) tandem mass spectrometry (MS/MS). Lipid components were extracted from coix seed by reflux extraction using n-hexane for 3 hr. TAGs and DAGs in coix seed extract were effectively purified and isolated from matrix interferences by prep-TLC and then analyzed by LC-APCI-MS and MS/MS for identification. TAGs were effectively identified taking into consideration of their LC retention behavior, APCI-MS spectra patterns, and MS/MS spectra of $[DAG]^+$ ions. In MS/MS spectra of TAGs, diacylglycerol-like fragment $[DAG]^+$ ions were useful to identify TAGs with isobaric fragment ions. Based on an established method, 27 TAGs and 8 DAGs were identified in coix seed extract. Among them, 15 TAGs and 8 DAGs were for the first time observed in coix seed. Interestingly, some of TAGs isolated by prep-TLC were partly converted into DAGs through probably photolysis process during storing in room temperature. Thus, degradation phenomenon of TAGs should be considered in the quality evaluation and nutritional property of coix seed. LC-APCI-MS/MS combined with prep-TLC will be practical method for precise TAG and DAG analysis of other herbal plants.

• 대한화학회지
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• 제59권3호
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• pp.225-232
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• 2015

하천수 중에 7가지의 농약류(2,4-dichlorophenoxyacetic acid, 메소밀, 알디캅, MCPA, molinate, 카바릴, 카보퓨란)와 2가지의 합성원료(quinoline, 비스페놀-A)를 액체크로마토그래피 전자분무 이온화 질량분석법(liquid chromatography-electrospray ionization-tandem mass spectrometry, LC-ESI-MS/MS)을 사용하여 분석하였다. 분석물질들은 고체상 추출법(solid-phase extraction, SPE)을 사용하여 추출하였다. 용리액은 질소가스로 농축하였다. 잔여물에 30% 메탄올 수용액 100 μL를 재 용해시켜 0.2 μm PTFE 실린지 필터로 거른 후 그 일부를 LC-ESI-MS/MS에 직접 주입하여 분석하였다. 확립된 조건에서 검정곡선은 0.997 이상의 상관계수를 갖는 직선성을 보였다. 정량한계는 0.002~0.011 μg/L 이었고, 정밀도는 16.4% 이하였다. 또한 정확도는 84~107%의 범위를 보였고, 회수율은 56.2~98.6% 값을 나타내었다. 본 연구에서 개발한 분석법을 실제 하천수 분석에 적용하였다.

• Bulletin of the Korean Chemical Society
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• 제26권5호
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• pp.729-734
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• 2005

A sensitive and selective method for quantitation of sofalcone and its active metabolite in human plasma has been established using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS). Plasma samples were transferred into 96-well plate using an automated sample handling system and spiked with 10 $\mu$L of 2 $\mu$g/mL $d_3$-sofalcone and $d_3$-sofalcone metabolite solutions (internal standard), respectively. After adding 0.5 mL of acetonitrile to the 96-well plate, the plasma samples were then vortexed for 30 sec. After centrifugation, the supernatant was transferred into another 96-well plate and completely evaporated at 40 ${^{\circ}C}$ under a stream of nitrogen. Dry residues were reconstituted with mobile phase and were injected into a $C_{18}$ reversed-phase column. The limit of quantitation of sofalcone and its metabolite was 2 ng/mL, using a sample volume of 0.2 mL for analysis. The reproducibility of the method was evaluated by analyzing 10 replicates over the concentration range of 2 ng/mL to 1000 ng/mL. The validation experiments of the method have shown that the assay has good precision and accuracy. Sofalcone and its metabolite produced a protonated precursor ion ([M+H]$^+$) of m/z 451 and 453, and a corresponding product ion of m/z 315 and 317, respectively. Internal standard ($d_3$-sofalcone and $d_3$-sofalcone metabolite) produced a protonated precursor ion ([M+H]$^+$) of m/z 454 and 456 and a corresponding product ion of m/z 315 and 317, respectively. The method has been successfully applied to a pharmacokinetic study of sofalcone and its active metabolite in human plasma.

• 한국축산식품학회지
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• 제35권6호
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• pp.765-771
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• 2015

The development of a sample preparation method and optimization of the analytical instrumentation conditions were performed for the determination of the vitamin B₁₂ content in emulsified baby foods sold on the Korea market. After removal of the milk protein and fats by chloroform extraction and centrifugation, the vitamin B₁₂ was water extracted from the sample. Following filtration of the solution through a nylon filter, the water-soluble extract was purified by solid-phase extraction using a Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS). The solution eluted from the cartridge was dried under a stream of nitrogen gas and reconstituted with 1 mL of water. The sample solution was injected into an LC-MS/MS system after optimizing the mobile phase for vitamin B₁₂ detection. The calibration curve showed good linearity with the coefficient of correlation (r²) value of 0.9999. The limit of detection was 0.03 µg/L and the limit of quantitation was 0.1 µg/L. The method of detection limit was 0.02 µg/kg. The vitamin B₁₂ recovery from a spiking test was 99.62% for infant formula and 99.46% for cereal-based baby food. The sample preparation method developed in this study would be appropriate for the rapid determination of the vitamin B₁₂ content in infant formula and baby foods with emulsified milk characteristics. The ability to obtain stable results more quickly and efficiently would also allow governments to exercise a more extensive quality control inspection and monitoring of products expected to contain vitamin B₁₂. This method could be implemented in laboratories that require time and labor saving.

• 한국식품위생안전성학회지
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• 제32권2호
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• pp.89-95
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• 2017

에너지 음료는 카페인을 주성분으로 타우린, 비타민 같은 다른 energy-enhancing 성분을 함유하고 있다. 미국과 유럽에서는 글루쿠로노락톤이 에너지 음료에 첨가될수 있으나, 국내에서 의약품으로는 허가되어 있다. 따라서 식품 첨가물로는 그 사용이 금지 되어 있어, 지속적으로 수입 및 유통 음료에서 시험검사를 하여 규제하고 있다. 현재 분석법으로 사용하는 LC-PDA 법은 복잡한 유도체화 과정을 거치고, 음료 중에 당류들이 위양성 결과를 나타내기도 한다. 이런 기존 방법의 단점을 개선하기 위해 HILIC-ESI-MS/MS(hydrophilic interaction liquid chromatography coupled to electrospray ionization tandem mass spectrometry)를 이용한 분석법을 개발하고, 선택성, 직선성, 검출한계, 정량한계, 정밀도, 정확성, 재현성에 대하여 분석법 유효성 검증을 수행했고, AOAC, EURACHEM 가이드라인에 부합되는 결과를 얻었다.

• Translational and Clinical Pharmacology
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• 제25권2호
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• pp.67-73
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• 2017

Glimepiride, a third generation sulfonylurea, is an antihyperglycemic agent widely used to treat type 2 diabetes mellitus. In this study, an untargeted urinary metabolomic analysis was performed to identify endogenous metabolites affected by glimepiride administration. Urine samples of twelve healthy male volunteers were collected before and after administration of 2 mg glimepiride. These samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and then subjected to multivariate data analysis including principal component analysis and orthogonal partial least squares discriminant analysis. Through this metabolomic profiling, we identified several endogenous metabolites such as adenosine 3', 5'-cyclic monophosphate (cAMP), quercetin, tyramine, and urocanic acid, which exhibit significant metabolomic changes between pre- and posturine samples. Among these, cAMP, which is known to be related to insulin secretion, was the most significantly altered metabolite following glimepiride administration. In addition, the pathway analysis showed that purine, tyrosine, and histidine metabolism was affected by pharmacological responses to glimepiride. Together, the results suggest that the pharmacometabolomic approach, based on LC-MS/MS, is useful in understanding the alterations in biochemical pathways associated with glimepiride action.

• 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.

• 분석과학
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• 제15권5호
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• pp.410-416
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• 2002

본 연구에서는 LC - MS/MS를 이용해 혈장과 뇨중에서 반코마이신을 신속하게 정량분석하는 방법을 개발하였다. 크로마토그래피는 $C_{18}$ XTerra MS 컬럼 ($2.1{\times}30mm$, $3.5{\mu}m$)을 사용하여 분석하였다. 이동상으로는 0.25% 초산이 섞인 10% 아세토니트릴 용액을 사용하였으며, 유속은 $250{\mu}L/min$이다. 반코마이신과 카페인 (내부표준물질)은 multiple reaction monitoring (MRM) 방법을 사용하여 검출하였으며 반코마이신은 precursor ion m/z 725.0 ( $[M+2H]^{2+}$)와 product ion m/z 100.0을 사용하였다. 혈장에서 반코마이신의 검출한계는 1 nM이며 좋은 정확성과 정밀성을 보여주었다. 또한 혈장중에서 반코마이신의 정량범위는 $0.01{\mu}M$ - $100{\mu}M$이다. 혈장과 뇨중에서 반코마이신을 정량하는 이 분석방법은 약물동력학연구 및 관련연구에 성공적으로 적용되었다.