• 대한기계학회논문집
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• 제13권4호
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• pp.789-798
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• 1989

본 연구에서는 평균속도구배를 용이하게 변화시킬 수 있는 전단유동 발생기를 제작하였다. 최고속도구배는 38se $c^{-1}$까지 얻을 수 있으며 최대중심선 속도는 15m/sec까지이다. 10개의 채널(두께 2mm인 알루미늄판)로 유동단면을 등분하 였으며, 각 채널의 내부저항조절 방법으로 마름모형태의 막대인 knob을 설치하였다.

• Mass Spectrometry Letters
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• 제4권3호
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• pp.55-58
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• 2013

Dioscin is a biologically active steroidal saponin with anticancer and hepatoprotective effects. A rapid, selective, and sensitive liquid chromatographic method with electrospray ionization tandem mass spectrometry was developed for the quantification of dioscin in rat plasma. Dioscin was extracted from rat plasma using ethyl acetate at acidic pH. The analytes were separated on a Halo C18 column using gradient elution of acetonitrile and 0.1% formic acid and detected by tandem mass spectrometry in selected reaction monitoring mode. The standard curve was linear ($r^2$ = 0.998) over the concentration range of 1-100 ng/mL. The lower limit of quantification was 1.0 ng/mL using 50 ${\mu}L$ of plasma sample. The coefficient of variation and relative error for intra- and inter-assay at four QC levels were 1.3 to 8.0% and -5.4 to 10.0%, respectively. This method was applied successfully to the pharmacokinetic study of dioscin after oral administration of dioscin at a dose of 29.2 mg/kg in male Sprague-Dawley rats.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1559-1563
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• 2011

Thermal hydrogenation of phenylacetylene (PA, $C_8H_6$) to styrene ($C_8H_8$) on pre-$C_xH_y$- and C-covered Cu(111) single crystal substrates has been studied using temperature-programmed desorption (TPD) mass spectrometry. Chemisorbed PA with an acetylene group has been proved to be associated with hydrogen of pre-adsorbed $C_xH_y$ to form styrene (104 amu) on Cu surface. For the parent (PA) mass (102 amu) TPD profile, the TPD peaks at 360 K and 410 K are assigned to chemisorbed vertically aligned PA and flat-lying cross-bridged PA, respectively (J. Phys. Chem. C 2007, 111, 5101). The relative $I_{360K}/I_{410K}$ TPD ratio dramatically increases with increasing pre-adsorbed $C_xH_y$ before dosing PA, while the ratio does not increase for pre-C-covered surface. For PA on pre-$C_xH_y$-covered Cu(111) surface, styrene desorption is enhanced relative to the parent PA desorption, while styrene formation is dramatically quenched on pre-C-covered (lack of adsorbed hydrogen nearby) surface. It appears that only cross-bridged PA associates with adsorbed hydrogen to form styrene that promptly desorbs at 410 K, while vertically aligned PA is less likely to participate in forming styrene.

• Nutrition Research and Practice
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• 제16권3호
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• pp.298-313
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• 2022

BACKGROUND/OBJECTIVES: The effectiveness of natural compounds in improving athletic ability has attracted attention in both sports and research. Gynostemma pentaphyllum (Thunb.) leaves are used to make traditional herbal medicines in Asia. The active components of G. pentaphyllum, dammarane saponins, or gypenosides, possess a range of biological activities. On the other hand, the anti-fatigue effects from G. pentaphyllum extract (GPE) and its effective compound, gypenoside L (GL), remain to be determined. MATERIALS/METHODS: This study examined the effects of GPE on fatigue and exercise performance in ICR mice. GPE was administered orally to mice for 6 weeks, with or without treadmill training. The biochemical analysis in serum, glycogen content, mRNA, and protein expressions of the liver and muscle were analyzed. RESULTS: The ExGPE (exercise with 300 mg/kg body weight/day of GPE) mice decreased the fat mass percentage significantly compared to the ExC mice, while the ExGPE showed the greatest lean mass percentage compared to the ExC group. The administration of GPE improved the exercise endurance and capacity in treadmill-trained mice, increased glucose and triglycerides, and decreased the serum creatine kinase and lactate levels after intensive exercise. The muscle glycogen levels were higher in the ExGPE group than the ExC group. GPE increased the level of mitochondrial biogenesis by enhancing the phosphorylation of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) protein and the mRNA expression of nuclear respiratory factor 1, mitochondrial DNA, peroxisome proliferator-activated receptor-δ, superoxide dismutase 2, and by decreasing the lactate dehydrogenase B level in the soleus muscle (SOL). GPE also improved PGC-1α activation in the SOL significantly through AMPK/p38 phosphorylation. CONCLUSIONS: These results showed that GPE supplementation enhances exercise performance and has anti-fatigue activity. In addition, the underlying molecular mechanism was elucidated. Therefore, GPE is a promising candidate for developing functional foods and enhancing the exercise capacity and anti-fatigue activity.

• Natural Product Sciences
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• 제23권2호
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• pp.84-91
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• 2017

This study proposes a sensitive and selective liquid chromatography-electrospray ionization tandem mass spectrometry method of efficiently assessing the quality of a traditional herbal medicine called Yeonggyechulgam-tang (YGCGT). The following compounds 1 - 11, namely, liquiritin apioside (1), liquiritin (2), liquiritigene (3), coumarin (4), cinnamic acid (5), cinnamaldehyde (6), glycyrrhizin (7), atractylenolide III (8), atractylenolide II (9), atractylenolide I (10), and pachymic acid (11) were separated on a UPLC BEH $C_{18}$ column ($2.1{\times}100mm$, $1.7{\mu}m$) at a column temperature of $45^{\circ}C$ eluted with a gradient condition of 0.1% (v/v) formic acid in distilled water and acetonitrile. The correlation coefficient of the calibration curve of the eleven constituents was ${\geq}0.9936$. The limits of detection and quantification of the compounds 1 - 11 were 0.06 - 4.73 ng/mL and 0.17-14.20 ng/mL, respectively. Using this analytical method, the compound 11 in lyophilized YGCGT decoction extract was not detected, while the compounds 1 - 10 were detected 0.13-166.43 mg/g.

• 분석과학
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• 제21권6호
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• pp.502-509
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• 2008

혈청 내 콜레스테롤을 정량분석하기 위한 일차분석법으로 동위원소희석 액체크로마토그래피/질량분석법(isotope dilution liquid chromatography/mass spectrometry)을 사용하였다. 콜레스테롤은 Thermo ODS hypersil $C^{18}$ 칼럼을 사용하여 분리하였고, 이동상은 100% 메탄올, 유속은 0.3 mL/min으로 하였다. 콜레스테롤과 콜레스테롤-$3,4-13C_2$는 $[M-H_2O+H]^+$이온에 해당하는 m/z 369.4와 371.3에서 모니터링하여 정량에 합당한 크로마토그램을 얻을 수 있었다. 방법의 유효성을 증명하기 위해서 NIST SRM 909b를 분석한 결과 인증값과 불확도 범위 내에서 일치하는 것을 확인하였다. 이 방법을 바탕으로 혈청 인증표준 물질 4 종류를 제조하여 인증을 실시하였다. 인증 결과, 반복성의 상대표준오차는 0.1~0.8%, 재현성의 경우 0.24%이하, 확장 불확도는 95% 신뢰도구간에서 약 1.43%로 나타났다.

• 분석과학
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• 제13권3호
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• pp.385-393
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• 2000

뇨시료 중 amineptine의 (dihydro-10, 11-dibenzo[a, d] cycloheptenyl-5-amino-7-heptanoic acid) metabolites를 분석하기 위한 최적조건을 찾기 위하여 pH 변화에 따른 추출률과 세가지의 유도체화시약에 대한 반응성을 조사해본 결과 pH는 9.5, 유도체화시약은 carboxylic acid group에 MSTFA로 반응 시켰을 경우 좋은 결과를 나타내었다. GC/MS를 이용하여 amineptine을 복용한 사람의 뇨를 분석한 결과 amineptine과 그 대사물질인 dihydro-10, 11-dibenzo[a, d] cycloheptenyl-5-amino-5-pentanoic acid ($C_5$-metabolite)와 $C_5$-metabolite의 lactamized product인 ${\delta}$-lactam을 확인하였다. Amineptine과 그 metabolite들을 GC/MS-SIM mode로 분석하기 위한 monitoring ion들은 m/z 192를 공통 이온으로 선정하였으며, 각각의 분자이온을 선정하였다. Amineptine의 excretion study 결과, amineptine, ${\delta}$-lactam 및 $C_5$-metabolite는 4시간이내에 70-90%가 배설되었고 20시간 이내에 거의 배설이 완결되었다.

• Journal of Applied Biological Chemistry
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• 제44권4호
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• pp.167-172
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• 2001

A cDNA fragment encoding the chloroplastic fructose-1, 6-bisphosphatase (FBPase) was cloned via PCR from the cDNA library of pea leaves. The cloned cDNA, about 1.05 kbp without signal sequence, was introduced into a pET-28a vector for expression in E. coli strain BL21(DE3)pLysS. The recombinant FBPase was purified through $Ni^+-NTA$ affinity chromatography and characterized. Molecular mass of the monomer was about 42,000. Enzymatic activity of the purified enzyme as the native pea chloroplastic FBPase was the highest at alkaline pH (pH 9.0). The recombinant enzyme was activated by a reducing agent DTT and was insensitive to AMP. The activation energy (Ea) and Arrehenius frequency factor were 42.67 kcal/mol and $2.65{\times}10^{14}/s$, respectively, slightly higher than those of the native enzyme. $K_M$ and $V_{max}$ were $99.98{\mu}M$ and $52.9{\mu}M/min$, respectively, which were comparable with the native enzyme.

• 한방비만학회지
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• 제17권2호
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• pp.87-95
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• 2017

Objectives: This study was conducted to evaluate efficacy and safety of Punica granatum L. Actinidia chinensis Planch. mixed extract on body fat. Methods: Thirty women were recruited ($25kg/m^2{\leq}body$ mass index [BMI]${\leq}29.9kg/m^2$) ($19yr{\leq}age{\leq}38yr$) and randomized to receive Punica granatum L. Actinidia chinensis Planch. mixed extract or placebo for 8 weeks. During the test, they visited four times including screening. Body fat mass, body fat rate, anthropometric dimensions at waist and hip, waist-hip ratio, total cholesterol, triglyceride, low density lipoprotein-cholesterol (LDL-C), and high density lipoprotein-cholesterol (HDL-C) were measured at screening and 8 weeks after screening. Adverse reaction were also checked each visit. Results: There were no significant differences in all index. But when divide experimental group by BMI index, age, and compliance, less than BMI $27kg/m^2$ group decreased body weight, body fat mass and more than BMI $27kg/m^2$ group also decreased body weight, body fat mass and waist circumference. Less than age 30 years group showed decline of waist circumference, fat free rate and T-cholesterol and more than age 30 years group showed decline of fat free mass. Group with compliance more than 95% was decreased BMI, fat free mass, and hip circumference. Conclusions: There was no significant efficacy as compared with placebo group, but as divide experimental group according to BMI index, age, compliance, mixed extract might be effective to reduce obesity index.

• 한국분말재료학회지
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• 제21권4호
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• pp.294-300
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• 2014

The connecting rod is one of the most important parts in automotive engines, transforming the reciprocal motion of a piston generated by internal combustion into the rotational motion of a crankshaft. Recent advances in high performance automobile engines demand corresponding technological breakthroughs in the materials for engine parts. In the present research, the powder metallurgy (P/M) process was used to replace conventional quenching and/or tempering processes for mass production and ultimately for more cost-efficient manufacturing of high strength connecting rods. The development of P/M alloy powder was undertaken not only to achieve the improvement in mechanical properties, but also to enhance the machinability of the P/M processed connecting rods. Specifically $MoS_2$ powders were added as lubricants to non-normalizing Fe-Cr-Mn-V-C alloy powder to improve the post-sintering machinability. The effects of $MoS_2$ addition on the microstructure, mechanical properties, and machining characteristics were investigated.