Publications (28)97.41 Total impact
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Article: A simple one-step assay platform based on fluorescence quenching of macroporous silicon.
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ABSTRACT: We synthesized 3D macroporous silicon through a simple electrochemical dissolution process and systematically estimated its protein adsorption and effect on fluorescence emission. Compared with conventional 2D polystyrene plate, the macroporous silicon showed a superior protein adsorption capacity and significant fluorescence quenching effect. We developed a 3D macroporous silicon-based adenosine assay system through the following fabrication process: streptavidin molecules that have been immobilized on the surface of macroporous silicon are attached with biotin-linked and adenosine-specific DNA aptamer, followed by hybridization between the attached aptamer and fluorescent chemical (carboxytetramethylrhodamine/CTMR) that is conjugated with a short complementary DNA sequence. In the absence of adenosine, the aptamer-CTMR complexes remain closely attached to the surface of porous silicon, hence fluorescence being significantly quenched. Upon binding to adenosine, the DNA aptamer is subject to structure switching that leads to dissociation of CTMR from DNA aptamer, and consequently the CTMR fluorescence is restored, indicating a simple one-step assay of adenosine. Compared to the conventional 2D PS and ZnO nanorods-based assays, adenosine at much lower (sub-micromolar) concentration was successfully detected through the 3D macroporous silicon-based assay. The three-dimensionally and densely immobilized aptamer probes and effective fluorescence quenching on the surface of macroporous silicon enables adenosine to be detected at lower levels. Although the adenosine detection is reported here as a proof-of-concept, the developed macroporous silicon-based simple one-step assay platform can be applied in general to fluorescence quenching -based detection of many other biomolecules.Biosensors & bioelectronics 09/2012; · 5.43 Impact Factor -
Article: Selection of aptamers in SELEX process
04/2012; 1(1):1-7. -
Article: Sol-gel derived nanoporous compositions for entrapping small molecules and their outlook toward aptamer screening.
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ABSTRACT: This paper reports for the first time the application of sol-gel microarrays for immobilizing nonsoluble small chemicals (Bisphenol-A; BPA). Also, known problems of sol-gel adhesion to conventional microtiter well plate substrates are circumvented by anchoring the sol-gel microspots to a porous silion surface so-called, PS-SG chips. We confirmed low molecular weight chemical immobilization inside a sol-gel network using fluorescein. BPA and the BPA specific aptamer were utilized as a model pair to verify the affinity specific interaction in the PS-SG selection system. The aptamer interacted specifically with BPA in the sol-gel spots, as shown in microarrays forming the letters "L", "U", "N", and "D". Moreover, the bound aptamer was released by heat, recovered, and verified by gel electrophoresis. The developed PS-SG chip platform will be used for screening aptamers against numerous small molecules such as toxins, metabolites, or pesticide residues.Analytical Chemistry 01/2012; 84(6):2647-53. · 5.86 Impact Factor -
Article: A sol-gel-integrated protein array system for affinity analysis of aptamer-target protein interaction.
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ABSTRACT: A sol-gel microarray system was developed for a protein interaction assay with high activity. Comparing to 2-dimensional microarray surfaces, sol-gel can offer a more dynamic and broad range for proteins. In the present study, this sol-gel-integrated protein array was used in binding affinity analysis for aptamers. Six RNA aptamers and their target protein, yeast TBP (TATA-binding protein), were used to evaluate this method. A TBP-containing sol-gel mixture was spotted using a dispensing workstation under high-humidity conditions and each Cy-3-labeled aptamer was incubated. The dissociation constants (K(d)) were calculated by plotting the fluorescent intensity of the bound aptamers as a function of the TBP concentrations. The K(d) value of the control aptamer was found to be 8 nM, which agrees well with the values obtained using the conventional method, electric mobility shift assay. The sol-gel-based binding affinity measurements fit well with conventional binding affinity measurements, suggesting their possible use as an alternative to the conventional method. In addition, aptamer affinity measurements by the sol-gel-integrated protein chip make it possible to develop a simple high-throughput affinity method for screening high-affinity aptamers.Nucleic acid therapeutics. 06/2011; 21(3):179-83. -
Article: A sol-gel-based microfluidics system enhances the efficiency of RNA aptamer selection.
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ABSTRACT: RNA and DNA aptamers that bind to target molecules with high specificity and affinity have been a focus of diagnostics and therapeutic research. These aptamers are obtained by SELEX often requiring many rounds of selection and amplification. Recently, we have shown the efficient binding and elution of RNA aptamers against target proteins using a microfluidic chip that incorporates 5 sol-gel binding droplets within which specific target proteins are imbedded. Here, we demonstrate that our microfluidic chip in a SELEX experiment greatly improved selection efficiency of RNA aptamers to TATA-binding protein, reducing the number of selection cycles needed to produce high affinity aptamers by about 80%. Many aptamers were identical or homologous to those isolated previously by conventional filter-binding SELEX. The microfluidic chip SELEX is readily scalable using a sol-gel microarray-based target multiplexing. Additionally, we show that sol-gel embedded protein arrays can be used as a high-throughput assay for quantifying binding affinities of aptamers.Oligonucleotides 03/2011; 21(2):93-100. · 2.80 Impact Factor -
Article: Development of single-stranded DNA aptamers for specific Bisphenol a detection.
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ABSTRACT: The development of reagents with high affinity and specificity to small molecules is crucial for the high-throughput detection of chemical compounds, such as toxicants or pollutants. Aptamers are short and single-stranded (ss) oligonucleotides able to recognize target molecules with high affinity. Here, we report the selection of ssDNA aptamers that bind to Bisphenol A (BPA), an environmental hormone. Using SELEX process, we isolated high affinity aptamers to BPA from a 10(15) random library of 60 mer ssDNAs. The selected aptamers bound specifically to BPA, but not to structurally similar molecules, such as Bisphenol B with one methyl group difference, or 4,4'-Bisphenol with 2 methyl groups difference. Using these aptamers, we developed an aptamer-based sol-gel biochip and detected BPA dissolved in water. This novel BPA aptamer-based detection can be further applied to the universal and high-specificity detection of small molecules.Oligonucleotides 03/2011; 21(2):85-91. · 2.80 Impact Factor -
Article: Aptamer microarray mediated capture and mass spectrometry identification of biomarker in serum samples.
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ABSTRACT: Sensitive detection of molecular biomarkers in clinical samples is crucially important in disease diagnostics. This paper reports the development of an aptamer microarray platform combined with sol-gel technology to identify low-abundance targets in complex serum samples. Because of the nanoporous structure of the sol-gel, a high capacity to immobilize the affinity specific aptamers is accomplished which allows binding and detection of target molecules with high sensitivity. The captured protein is digested in situ and the obtained digest was analyzed by ESI-MS without any interference from the affinity probe. TBP (TATA Box Protein) and its specific aptamers were chosen as a model system. A proof of concept with protein concentrations ranging between nanomolar to micromolar is reported, showing a good linearity up to 400 nM when characterized in an aptamer sandwich assay. Moreover, as low as 0.001% of target protein present in total serum proteins could be identified without any pretreatment step using ESI MS/MS mass spectrometry. We believe this novel strategy could become an efficient method for aptamer-based biomarker detection linked directly to mass spectrometry readout.Journal of Proteome Research 11/2010; 9(11):5568-73. · 5.11 Impact Factor -
Article: Aptamer sandwich-based carbon nanotube sensors for single-carbon-atomic-resolution detection of non-polar small molecular species.
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ABSTRACT: A portable sensor platform for the detection of small molecular species is crucial for the on-site monitoring of environmental pollutants, food toxicants, and disease-related metabolites. However, it is still extremely difficult to find highly selective and sensitive sensor platforms for general small molecular detection. Herein, we report aptamer sandwich-based carbon nanotube sensor strategy for small molecular detection, where aptamers were utilized to capture target molecules as well as to enhance the sensor signals. We successfully demonstrated the detection of non-polar bisphenol A molecules with a 1 pM sensitivity. Significantly, our sensors were able to distinguish between similar small molecular species with single-carbon-atomic resolution. Furthermore, using the additional biotin modification on labeling aptamer, we enhanced the detection limit of our sensors down to 10 fM. This strategy allowed us to detect non-polar small molecular species using carbon nanotube transistors, thus overcoming the fundamental limitation of field effect transistor-based sensors. Considering the extensive applications of sandwich assay for the detection of rather large biomolecules, our results should open up completely new dimension in small molecular detection technology and should enable a broad range of applications such as environmental protection and food safety.Lab on a Chip 10/2010; 11(1):52-6. · 5.67 Impact Factor -
Article: Effect of taxifolin glycoside on atopic dermatitis-like skin lesions in NC/Nga mice.
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ABSTRACT: Increased levels of eosinphils, IgE, IL-4, 5, and 13 and pro-inflammatory factors (COX-2, iNOS) are observed in patients with atopic dermatitis (AD). Taxifolin 3-O-beta-D-glucopyranoside (TAX) from the roots of Rhododendron mucronulatum (RM) was examined to determine whether its immunomodulatory effect was applicable for treating atopic dermatitis.A total of 7 groups of NC/Nga mice with AD were treated by topical application or intraperitoneal injection of TAX for 4 weeks. Follow-up evaluations were done to assess the changes in clinical observations, eosinophil counts, and levels of IgE, cytokines, COX-2 and iNOS.In the clinical observation during the experimental period, TAX treatment significantly reduced the severity of AD-like lesions induced in NC/Nga mice. Eosinophil and IgE levels decreased after treatment of the animals with TAX. TAX may thus be associated with improvement of eosinophil-related allergic diseases. The expression of cytokines (IL-4, 5 and 13) was significantly inhibited in the TAX-treated group, suggesting that TAX might play an immunoregulatory role associated with AD. In RT-PCR, iNOS and COX-2 expression levels were reduced in the TAX-treated group. In western blotting, the expression levels of iNOS and COX-2 were also reduced in the TAX-treated group.These findings suggest that TAX is effective for the treatment of AD by preventing the production of inflammatory cytokines and by reducing skin inflammation.Phytotherapy Research 07/2010; 24(7):1071-7. · 2.09 Impact Factor -
Article: Long-pulsed Nd:YAG laser treatment of warts: report on a series of 369 cases.
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ABSTRACT: Various treatment methods have been adopted in the management of warts; however, there is still no consensus on first-line treatment. This study was designed to evaluate the efficacy of long-pulsed Nd:YAG laser in the treatment of warts. Over the course of 1 yr, 369 patients with recalcitrant or untreated warts were exposed to a long-pulsed Nd:YAG laser. The following parameters were used: spot size, 5 mm; pulse duration, 20 msec; and fluence, 200 J/cm(2). No concomitant topical treatment was used. In all, 21 patients were lost during follow up; hence, the data for 348 patients were evaluated. The clearance rate was 96% (336 of the 348 treated warts were eradicated). The clearance rate of verruca vulgaris after the first treatment was very high (72.6%), whereas the clearance rate of deep palmopantar warts after the first treatment was low (44.1%). During a median follow-up period of 2.24 months (range, 2-10 months), 11 relapses were seen (recurrence rate, 3.27%). In conclusion, long-pulsed Nd:YAG laser is safe and effective for the removal or reduction of warts and is less dependent on patient compliance than are other treatment options.Journal of Korean medical science 10/2009; 24(5):889-93. · 0.84 Impact Factor -
Article: The use of 1540 nm fractional photothermolysis for the treatment of acne scars in Asian skin: a pilot study.
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ABSTRACT: Various modalities have been used to treat acne scars, but limited efficacy and considerable side effects have restricted their proper use. Recently, a new-generation fractional photothermolysis modality has been introduced that has deeper penetrating ability; however, a 1540 nm fractional photothermolysis study has not yet been performed. To evaluate the efficacy and safety of 1540 nm fractional photothermolysis for the treatment of acne scars in Asian skin. Sixteen volunteers (Fitzpatrick skin types III-IV) with mild to moderate acne scars were enrolled. Acne scar lesions were treated with 1540-nm fractional photothermolysis (Starlux 1540). Three treatment sessions were performed for each patient 4 weeks apart. Outcome assessments included the following four methods: (1) clinical evaluation of the photographs that were taken before and after the treatment; (2) comparison of the quality of life (QOL) of the patients before and after the treatment; (3) patients' satisfaction with the treatment; and (4) comparison of the quantity of collagen and elastic fibers in the skin biopsies before and 12 weeks after the last treatment. A mild to moderate clinical improvement was observed in most of the patients. Moreover, the QOL of all the patients improved, and all of them were satisfied with the results of the treatment. Significant collagen and elastic-fiber increases were also observed after the treatment, and side effects were limited to transient erythema and edema, which occurred in 50% of the patients. No severe side effect was observed. 1540 nm fractional photothermolysis is an effective and safe method for improving acne scar, even in Asian skin.Photodermatology Photoimmunology and Photomedicine 07/2009; 25(3):138-42. · 1.30 Impact Factor -
Article: Selection and elution of aptamers using nanoporous sol-gel arrays with integrated microheaters.
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ABSTRACT: RNA and DNA aptamers that bind to target molecules with high specificity and affinity have been a focus of diagnostics and therapeutic research. These aptamers are obtained by SELEX (Systematic Evolution of Ligands by EXponential enrichment) often requiring more than 10 successive cycles of selection and amplification, where each cycle normally takes 2 days per cycle of SELEX. Here, we have demonstrated the use of sol-gel arrays of proteins in a microfluidic system for efficient selection of RNA aptamers against multiple target molecules. The microfluidic chip incorporates five sol-gel binding droplets, within which specific target proteins are imbedded. The droplets are patterned on top of individually addressable electrical microheaters used for selective elution of aptamers bound to target proteins in the sol-gel droplets. We demonstrate that specific aptamers bind their respective protein targets and can be selectively eluted by micro-heating. Finally, our microfluidic SELEX system greatly improved selection efficiency, reducing the number of selection cycles needed to produce high affinity aptamers. The process is readily scalable to larger arrays of sol-gel-embedded proteins. To our knowledge, this is the first demonstration of a chip-based selection of aptamers using microfluidics, thereby allowing development of a high throughput and efficient SELEX procedures.Lab on a Chip 06/2009; 9(9):1206-12. · 5.67 Impact Factor -
Article: Gene expression profile related to prognosis of acute myeloid leukemia.
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ABSTRACT: Acute myeloid leukemia (AML) is a heterogeneous group of diseases with respect to biology and clinical course. Through genome-wide scanning, we can have an improvement of the diagnosis and assay system of AML. Microarray was performed for the identification of acute myeloid leukemia prognosis. We divided patients into two groups (good prognosis group, GPG and poor prognosis group, PPG) based on differences in the individual reactions to treatment. Gene expression profiles were analyzed using microarray. Among genes up-regulated at least two-fold and down-regulated at least 0.5-fold in HL-60, we chose three up-regulated genes (PPP2CA, ME3, and CCDN2) and three down-regulated genes (GLO1, ANXA2, and BMI1) and confirmed the expression of these six genes by RT-PCR. We created a leukemia-specific subclass microarray, based on the gene expression profiles. Clinical samples from the bone marrow of four patients were hybridized on this microarray. Among the genes selected by the microarray technology, NB4, silenced TRIB3 and overexpressed XRN2 were not differentiated in spite of treatment with ATRA. This indicates that XRN2 and TRIB3 play an important role in cell differentiation. These data provided an expression profile for the diagnosis and prognosis of AML patients and identified candidate genes that might allow the prognosis of AML through the relative comparison of the expression level of genes between GPG and PPG.Oncology Reports 01/2008; 18(6):1395-402. · 1.84 Impact Factor -
Article: Optimization of expression conditions for soluble protein by using a robotic system of multi-culture vessels.
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ABSTRACT: We have developed a robotic system for an automated parallel cell cultivation process that enables screening of induction parameters for the soluble expression of recombinant protein. The system is designed for parallelized and simultaneous cultivation of up to 24 different types of cells or a single type of cell at 24 different conditions. Twenty-four culture vessels of about 200 ml are arranged in four columns x six rows. The system is equipped with four independent thermostated waterbaths, each of which accommodates six culture vessels. A two-channel liquid handler is attached in order to distribute medium from the reservoir to the culture vessels, to transfer seed or other reagents, and to take an aliquot from the growing cells. Cells in each vessel are agitated and aerated by sparging filtered air. We tested the system by growing Escherichia coli BL21(DE3) cells harboring a plasmid for a model protein, and used it in optimizing protein expression conditions by varying the induction temperature and the inducer concentration. The results revealed the usefulness of our custom-made cell cultivation robot in screening optimal conditions for the expression of soluble proteins.Journal of Microbiology and Biotechnology 12/2007; 17(11):1868-74. · 1.38 Impact Factor -
Article: Enhanced stability of heterologous proteins by supramolecular self-assembly.
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ABSTRACT: Recently, we reported on the dual function of human ferritin heavy chain (hFTN-H) used for the fusion expression and solubility enhancement of various heterologous proteins: (1) high-affinity interaction with HSP70 chaperone DnaK and (2) formation of self-assembled supramolecules with limited and constant sizes. Especially the latter, the self-assembly function of hFTN-H is highly useful in avoiding the undesirable formation of insoluble macroaggregates of heterologous proteins in bacterial cytoplasm. In this study, using enhanced green fluorescent protein (eGFP) and several deletion mutants of Mycoplasma arginine deiminase (ADI(132-410)) as reporter proteins, we confirmed through TEM image analysis that the recombinant fusion proteins (hFTN-H::eGFP and hFTN-H::ADI(132-410)) formed intracellular spherical particles with nanoscale diameter ( approximately 10 nm), i.e., noncovalently cross-linked supramolecules. Surprisingly, the supramolecular eGFP and ADI showed much enhanced stability in bioactivity. That is, the activity level was much more stably maintained for the prolonged period of time even at high temperature, at high concentration of Gdn-HCl, and in wide range of pH. The stability enhancement by supramolecular self-assembly may make it possible to utilize the protein supramolecules as novel means for drug delivery, enzymatic material conversion (biotransformation), protein chip/sensor, etc. where the maintenance of protein/enzyme stability is strictly required.Applied Microbiology and Biotechnology 06/2007; 75(2):347-55. · 3.42 Impact Factor -
Article: Accelerated degradation of dipentyl phthalate by Fusarium oxysporum f. sp. pisi cutinase and toxicity evaluation of its degradation products using bioluminescent bacteria.
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ABSTRACT: The efficiency of two lipolytic enzymes (fungal cutinase and yeast esterase) in the degradation of dipentyl phthalate (DPeP) was investigated. The DPeP degradation rate of fungal cutinase was surprisingly high, i.e., almost 60% of the initial DPeP (500 mg/L) was decomposed within 2.5 hours, and nearly 40% of the degraded DPeP disappeared within the initial 15 minutes. With the yeast esterase, despite the same concentration, >87% of the DPeP remained even after 3 days of treatment. The final chemical composition after 3 days was significantly dependent on the enzyme used. During degradation with cutinase, most DPeP was converted into 1,3-isobenzofurandione (IBF) by diester hydrolysis. However, in the degradation by esterase, pentyl methyl phthalate, in addition to IBF, was produced in abundance. Toxicity monitoring using various recombinant bioluminescent bacteria showed that the degradation products from yeast esterase contained a toxic hazard, causing oxidative stress and damage to protein synthesis.Current Microbiology 06/2006; 52(5):340-4. · 1.82 Impact Factor -
Article: Effect of amniotic membrane on induced expression of iNOS by exposure to stimulants in HaCaT cells.
Journal of Dermatological Science 05/2006; 42(1):78-80. · 3.72 Impact Factor -
Article: Expression of neutrophil gelatinase-associated lipocalin in skin epidermis.
Journal of Investigative Dermatology 03/2006; 126(2):510-2. · 6.31 Impact Factor -
Article: Generation of parametric image of regional myocardial blood flow using H(2)(15)O dynamic PET and a linear least-squares method.
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ABSTRACT: Although a parametric image of myocardial blood flow (MBF) can be obtained from H(2)(15)O PET using factor and cluster analysis, this approach is limited when factor analysis fails to extract each cardiac component. In this study, a linear least-squares (LLS) method for estimating MBF and generating a MBF parametric image was developed to overcome this limitation. The computer simulation was performed to investigate the statistical properties of the LLS method, and MBF values obtained from the MBF parametric images in dogs were compared with those obtained using the conventional region of interest (ROI) and invasive microsphere methods. A differential model equation for H(2)(15)O in the myocardium was modified to incorporate the partial-volume and spillover effect. The equation was integrated from time 0 to each PET sampling point to obtain a linearlized H(2)(15)O model equation. The LLS solution of this equation was estimated and used to calculate the MBF, the perfusable tissue fraction (PTF), and the arterial blood volume fraction (V(a)). A computer simulation was performed using the input function obtained from canine experiments and the tissue time-activity curves contaminated by various levels of Poisson noise. The parametric image of the MBF, PTF, and V(a) was constructed using the PET data from dogs (n = 7) at rest and after pharmacologic stress. The regional MBF from the parametric image was compared with those produced by the ROI method using a nonlinear least-squares (NLS) estimation and an invasive radiolabeled microsphere technique. The simulation study showed that the LLS method was better than the NLS method in terms of statistical reliability, and the parametric images of the MBF, PTF, and V(a) using the LLS method had good image quality and contrast. The regional MBF values using the parametric image showed a good correlation with those using the ROI method (y = 0.84x + 0.40; r = 0.99) and the microsphere technique (y = 0.95x + 0.29; r = 0.96). The computation time was approximately 10 s for the 32 x 32 x 6 x18 (pixel x pixel x plane x frame) matrix. A noninvasive, very fast, and accurate method for estimating the MBF and generating a MBF parametric image was developed using the LLS estimation technique and H(2)(15)O dynamic myocardial PET.Journal of Nuclear Medicine 11/2005; 46(10):1687-95. · 6.38 Impact Factor -
Article: Biodegradation and detoxification of organophosphate insecticide, malathion by Fusarium oxysporum f. sp. pisi cutinase.
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ABSTRACT: Efficiencies of two lypolytic enzymes (fungal cutinase and yeast esterase) in malathion degradation were investigated. Surprisingly, degradation rate of malathion by fungal cutinase was very high, i.e. almost 60% of initial malathion (500 mg l(-1)) was decomposed within 0.5 h, and nearly 50% of the degraded malathion disappeared within initial 15 min. With the yeast esterase, despite the same concentration, more than 65% of malathion remained even after 2-day treatment. During enzymatic degradation of malathion, two malathion-derived compounds were detected, and time-course changes in composition were also monitored. In the degradation by both fungal cutinase and yeast esterase, two additional organic chemicals were produced from malathion: malathion monoacid (MMA) and malathion diacid (MDA) by ester hydrolysis. Final chemical composition after 2 d was significantly dependent on the enzyme used. Fungal cutinase produced MDA as a major degradation compound. However in the malathion degradation by yeast esterase, an isomer of MMA was produced in abundance in addition to MDA. Toxic effects of malathion and its final degradation products were investigated using various recombinant bioluminescent bacteria. As a result, the degradation products (including MMA) by esterase severely caused membrane damage and inhibition of protein synthesis in bacterial cells, while in the fungal cutinase processes, malathion was significantly degraded to non-toxic MDA after the extended period (2 days).Chemosphere 10/2005; 60(10):1349-55. · 3.21 Impact Factor
Top co-authors
Top Journals
Institutions
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2010–2012
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Dongguk University
Seoul, Seoul, South Korea -
Chung-Ang University
Seoul, Seoul, South Korea
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2009–2011
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Cornell University
- • Department of Molecular Biology and Genetics
- • School of Applied and Engineering Physics
Ithaca, NY, USA
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2004–2007
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Korea University
- Department of Chemical and Biological Engineering
Seoul, Seoul, South Korea
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1999–2005
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Seoul National University Hospital
- Department of Internal Medicine
Seoul, Seoul, South Korea
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