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RISS 인기검색어
- 검색키워드
- 저자 : Lee Jonghwa (검색결과 422 건)
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Lee, Jonghwa,Kim, Leesun,Shin, Yongho,Lee, Junghak,Lee, Jiho,Kim, Eunhye,Moon, Joon-Kwan,Kim, Jeong-Han American Chemical Society 2017 Journal of agricultural and food chemistry Vol.65 No.16
<P>A multiresidue method for the simultaneous and rapid analysis of 360 pesticides in representative agricultural produce (brown rice, orange, spinach, and potato) was developed using a modified QuEChERS procedure combined with gas chromatography tandem mass spectrometry (GC-MS/MS). Selected reaction monitoring transition parameters (e.g., collision energy, precursor and product ions) in MS/MS were optimized to achieve the best selectivity and sensitivity for a wide range of GC-amenable pesticides. A short (20 m) microbore (0.18 mm i.d.) column resulted in better signal-to-noise ratio with reduced analysis time than a conventional narrowbore column (30 m X 0.25 mm i.d.). The priming injection dramatically increased peak areas by masking effect on a new GC liner. The limit of quantitation was <0.01 mg/kg, and the correlation coefficients (r(2)) of matrix-matched standards were >0.99 within the range of 0.0025-0.1 mg/kg. Acetonitrile with 0.1% formic acid without additional buffer salts was used for pesticide extraction, whereas only primary secondary amine (PSA) was used for dispersive solid phase extraction (dSPE) cleanup, to achieve good recoveries for most of the target analytes. The recoveries ranged from 70 to 120% with relative standard deviations of <= 20% at 0.01 and 0.05 mg/kg spiking levels (n = 6) in all samples, indicating acceptable accuracy and precision of the method. Seventeen real samples from local markets were analyzed by using the optimized method, and 14 pesticides in 11 incurred samples were found at below the maximum residue limits.</P>
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Lee, Jonghwa,Shin, Yongho,Lee, Junghak,Lee, Jiho,Kim, Byung Joon,Kim, Jeong-Han Elsevier 2018 CHEMOSPHERE - Vol.207 No.-
<P><B>Abstract</B></P> <P>In this study, we developed a multiresidue method for the analysis of 310 pesticides in representative agricultural produce (brown rice, orange, and spinach) using ultra high performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) combined with a modified QuEChERS procedure. The optimal mobile phase composition (Methanol containing 5 mM ammonium formate and 0.1% formic acid) produced high sensitivity and reliable results. Also, the relationship between injection volume and repeatability of peak area was investigated. Most of the target pesticides had a limit of quantitation under 10 ng g<SUP>−1</SUP>, and correlation coefficients (<I>r</I> <SUP>2</SUP>) > 0.99 in matrix-matched standards within the range of 1–100 ng g<SUP>−1</SUP>. To validate the optimized method, recovery tests were performed with each of the crops at 10 and 50 ng g<SUP>−1</SUP> spiking levels (<I>n</I> = <I>5</I>). Satisfactory recoveries were achieved showing that 86.8–88.7% (at 10 ng g<SUP>−1</SUP>) and 91.9–96.1% (at 50 ng g<SUP>−1</SUP>) of the pesticides met the validation criteria (recoveries in the range of 70–120% and relative standard deviation ≤ 20%). Fifteen compounds were found to show a loss of recovery due to adsorption by primary and secondary amine or graphite carbon black. In the case of brown rice, 86.1% of pesticides showed an insignificant matrix effect (<±20%), while 35.2% and 41.6% of pesticides in orange and spinach were in that range, respectively. Sixteen apple samples from local markets were analyzed to evaluate the applicability of the optimized method. Nineteen pesticides were detected, of which the concentrations were lower than the maximum residue limit.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The protocol can analyze large number of pesticides (310 analytes) with modified QuEChERS and LC-MS/MS. </LI> <LI> A relationship between injection volumes and repeatability in LC-MS/MS analysis. </LI> <LI> Mobile phase compositions were compared for best sensitivity in LC-MS/MS. </LI> <LI> The method is reproducible and sensitive. </LI> <LI> It was successfully used to determine pesticide residues in market samples. </LI> </UL> </P>
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Kyeong Won Lee,Young Jun An,Janet Lee,Ye-Eun Jung,In Young Ko,Jonghwa Jin,Ji Hoon Park,Won Kyu Lee,Kiweon Cha,Sun-Shin Cha,Jung-Hyun Lee,Hyung-Soon Yim 한국미생물학회 2022 The journal of microbiology Vol.60 No.11
Fibroblast growth factor 11 (FGF11) is one of intracrine FGFs (iFGFs), which function within cells. Unlike canonical FGFs, FGF11 remains intracellularly and plays biological roles in FGF receptor (FGFR)-independent manner. Here, we established an expression system of recombinant FGF11 proteins in E. coli and investigated whether the extracellular administration of FGF11 can activate cellular signaling. Human FGF11 has two isoforms, FGF11a and FGF11b, depending on the presence of nuclear localization sequences (NLSs) in the N-terminus. Because these two isoforms are unstable, we prepared an FGF11a-Mut by substituting three cysteine residues in the NLS with serine and FGF11b-ΔC with C-terminal truncation. The introduction of mutation in the NLS improved the solubility of FGF11 prepared from E. coli. Exogenous addition of FGF11b and FGF11b-ΔC to BALB3T3 increased cell proliferation, while FGF11a-Mut exerted no effect. FGF11b-ΔC showed higher cell proliferation activity and FGFR signaling than FGF11b. The cell-proliferating activities of FGF11b and FGF11b-ΔC were blocked by an FGFR1 inhibitor or a recombinant FGFR1, confirming the FGFR1- dependent extracellular activity of FGF11b. The analysis of circular dichroism suggested that the C-terminus of FGF11 has an α-helical structure, which may affect its interaction with FGFR1. These results suggest that the N-and C-terminus of recombinant FGF11 are involved in the activation of FGFR1. The above results provide novel insights into the function and mechanism of FGF11 that may aid the development of useful ligands for FGFR regulation.
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Comparison of frictional forces on graphene and graphite
Lee, Hyunsoo,Lee, Naesung,Seo, Yongho,Eom, Jonghwa,Lee, SangWook IOP Pub 2009 Nanotechnology Vol.20 No.32
<P>We report on the frictional force between an SiN tip and graphene/graphite surfaces using lateral force microscopy. The cantilever we have used was made of an SiN membrane and has a low stiffness of 0.006 N m<SUP>−1</SUP>. We prepared graphene flakes on a Si wafer covered with silicon oxides. The frictional force on graphene was smaller than that on the Si oxide and larger than that on graphite (multilayer of graphene). Force spectroscopy was also employed to study the van der Waals force between the graphene and the tip. Judging that the van der Waals force was also in graphite–graphene–silicon oxide order, the friction is suspected to be related to the van der Waals interactions. As the normal force acting on the surface was much weaker than the attractive force, such as the van der Waals force, the friction was independent of the normal force strength. The velocity dependency of the friction showed a logarithmic behavior which was attributed to the thermally activated stick-slip effect. </P>
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Lee, Taeheon,Chae, Minsu,Lee, Chaeyeon,Jung, Jonghwa,Mohanty, Aruna Kumar,Kadir, Mohammad Abdul,Choi, Ji-Eun,Song, Jae Kwang,Paik, Hyun-Jong American Scientific Publishers 2018 Science of advanced materials Vol.10 No.1
<P>We report covalent bioconjugation of N-hydroxysuccinimidyl-end-functionalized polystyrene (NHS-PSt) with primary amino groups of lysine residues in protein to form in situ core-shell polymer-protein hybrid spherical nanostructures. For this, we synthesized NHS-PSt by atom transfer radical polymerization (ATRP) using N-hydroxysuccinimidyl-2-bromo-2-methylpropionate initiator. The polymer was characterized by gel permeation chromatography and H-1 NMR. For bioconjugation, NHS-PSt dissolved in DMF was added slowly to deionized water containing protein at pH 8 at room temperature in a glass vial. Self-assembled protein-polymer hybrid core-shell spherical nanostructures were characterized using DLS, TEM and confocal microscope studies. The stability of hybrid nanostructures was also studied over time.</P>
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Public Procurement for Innovation in Korea
Jonghwa Choi,Kwang Ho Lee,Ahjung Lee 과학기술정책연구원 2015 STI Policy Review Vol.6 No.2
Public procurement for innovation is used as one of the major policy tools to stimulate innovation and promote growth of small and medium-sized enterprises (SMEs) in Korea. However, it is evaluated that this policy has not been so effective in promoting technological innovation among SMEs largely because it heavily depends on price competitiveness of SMEs products and services. In order to draw some policy implications, this study examines the PPI policies of selected countries as comparative references and conducts an empirical analysis on Korean Public Procurement Services (PPS) data for identifying challenges of the current policy in Korea. We conclude that in order to enhance technological innovations of SMEs, PPI policy in Korea should 1) focus more on the potential competitiveness of SMEs, 2) enlarge public demands especially on R&D services, 3) encourage private sector participation in the public procurement market, 4) improve the assessment criteria for public procurement market registration, and 5) restructure the responsible organizations.
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Lee Junghak,Han Heeju,Yuan Xiu,Park Eunyoung,Lee Jonghwa,Kim Jeong-Han 한국응용생명화학회 2021 Applied Biological Chemistry (Appl Biol Chem) Vol.64 No.1
A quantitative analysis of ginsenoside is very important for ginseng studies because each ginsenoside shows different medical activity and metabolic pathway. In this study, a rapid, simultaneous, and quantitative analysis of 26 ginsenosides (Rb1, Rb2, Rc, Rd, Re, Rf, Rg1, Rg2(R), Rg2(S), Rg3(S), Rg3(R), Rg5, Rg6, Rh1(R), Rh1(S), Rh2(R), Rh2(S), F1, F2, F3, F4, K, Mc, PPT(S), XVII, and Y) in white, and red Panax ginseng was established using multiple reaction monitoring (MRM) mode on ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS). The mobile phase of water and methanol containing 0.1% formic acid and HSS T3 C18 analytical column was used for the chromatographic separation. The four sets of stereoisomers were successfully separated within a 26-min run time, eluting the S-isomer faster than the R-isomer with higher concentration. The ginseng extract was diluted by 100, 400 and 8000 times to fit in the calibration range and quantitated by the standard addition method. Matrix matched calibration by mixing 64 μL of the ginseng extract with 16 μL of the standard solution was used for compensating the matrix effect. Such quantitation methodology using dilution, standard addition and matrix matching resulted in precise and unambiguous quantitation of 26 ginsenosides in ginseng products. Major ginsenosides were observed at relatively higher concentrations in red Panax ginseng and the Mc was detected and quantitated for the first time in this study. The comprehensive quantitation system established in this study will contribute to quality evaluation, breeding and culturing, and quantitative metabolomics study of ginseng.
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