• Analytical Science and Technology
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• v.16 no.4
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• pp.325-332
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• 2003

To analyze co-planar PCBs in food, the isotopic dilution method by high resolution gas chromatography/high resolution mass spectrometry was applied. Among 209 PCB congeners, 12 congeners (#77, #81, #126, #169, #105, #114, #118, #123, #156, #157, #167 and #189) were chosen as target compounds that were toxic congeners re-assessed by WHO in 1998. Milk and milk products including cheese and butter were collected as food samples. Samples were homogenized, spiked with the known amount of the standard mixture and extracted. After extraction, extracts were cleaned up by sulfuric acid impregnated silica gel, purified on silica gel and alumina column chromatography and then analyzed by HRGC/HRMS. As results, the overall recoveries were ranged from 83% to 106% and the limit of detection was about 0.1 pg/g at signal/noise>3. Levels of targets in the selected food samples were 0.001~0.107 pgWHO-TEQ/g.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.1
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• pp.7-17
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• 2007

Purpose: As increasing complexity of modern radiotherapy technique, more developing dosimetry is required. Polymer gel dosimeters offer a wide range of potential applications with high resolution and assured quality in the thee-dimensional verification of complex dose distribution such as intensity-modulated radiotherapy (IMRT). The purpose of this study is to find the most sensitive and suitable gel as a dosimeter by varying its composition ratio and its condition such as temperature during manufacturing. Materials and Methods: Each polymer gel with various ratio of composition was irradiated with the same amount of photon beam accordingly. Various polymer gels were analyzed and compared using a dedicated software written in visual C++ which converts TE images to R2 map images. Their sensitivities to the photon beam depending on their composition ratio were investigated. Results: There is no dependence on beam energy nor dose rate, and calibration curve is linear. Conclusion: The polymer gel dosimeter developed by using anti-oxidant in this study proved to be suitable for dosimetry.

• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.483-490
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• 2004

We have developed a novel polymerase chain reaction (PCR)-microchip gel electrophoresis (MGE) method based on the sieving gel mixture of commercially available poly(vinylpyrrolidone) (PVP) and hydroxy ethyl cellulose (HEC) for the rapid detection and diagnosis of the orf virus (ORFV) from Korean indigenous goat. After amplification of 594-bp DNA fragment from the B2L gene of ORF virus, the amplicon was analyzed by the MGE separation. The glass microfluidic chip (64 mm total length (36 mm effective length)${\times}$90 ${\mu}$m width${\times}$20 ${\mu}$m depth) allowed the fast detection and diagnosis of ORFV in the mixture of 1.0% PVP ($M_r$ 360,000) and 1.0% HEC ($M_r$250,000) as a sieving matrix with better resolution and reproducibility of DNA fragments. Under the electric field of 277.8 V/cm, the 594-bp DNA was analyzed within 4 min. Compared to traditional slab gel electrophoresis, the PCR-MGE method was twenty times faster and an effective clinical method for the quantitative analysis of ORFV.

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.153-157
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• 2017

Gel type internal electrolytes were synthesized by varying hydroxyethyl-cellulose (HEC) amounts and their durability and conductivity were measured. The ionic conductivity decreased as the content of HEC increased thus the internal electrolyte containing more than 12% of HEC could not be used as a reference electrode. Based on durability test results, as the HEC amount decreased carrier density resulting in increasing of the amount of KCl coming out of the porous membrane. Therefore in order to use long time at ballast water treatment systems, we selected 10% HEC for gel type internal electrolyte. The resolution test for total residual oxidants (TRO) was carried out using the TRO sensor and the gel type reference electrode made of 10% HEC. A 50 mV potential was applied to the TRO sensor for 30 sec and changes in the current were measured. It was confirmed that the TRO concentrations ranging from 0 to 15 mg/L could be separated at salinity conditions of 0.2~30 PSU. The results indicated that the TRO concentration at sea water and at fresh water was successfully measured by the TRO sensor constructed with the reference electrode using gel-type internal electrolyte of HEC.

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.153-158
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• 2008

A microchip-based capillary gel electrophoresis (MCGE) technique was developed for the ultra-fast detection and differentiation of Candidatus Mycoplasma haemominutum (Candidatus M. haemominutum, California strain) and Mycoplasma haemofelis (M. haemofelis, Ohio strain) in Korean feral cats through the application of programmed field strength gradients (PFSG) in a conventional glass double-T microchip. The effects of the poly (ethyleneoxide) (PEO) concentration and electric field strength on the separation of DNA fragments were investigated. The PCR-amplified products of Candidatus M. haemominutum (202-bp) and M. haemofelis (273-bp) were analyzed by MCGE within 75 s under a constant applied electric field of 117.6 V/cm and a sieving matrix of 0.3% PEO (Mr 8 000 000). When the PFSG was applied, MCGE analysis generated results 6.8-times faster without any loss of resolution or reproducibility. The MCGE-PFSG technique was also applied to eleven samples selected randomly from 33 positive samples. The samples were detected and differentiated within 11 s. The analysis time of the MCGE-PFSG technique was approximately 980-times faster than that using conventional slab gel electrophoresis.

• Journal of the Korean Society of Visualization
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• v.6 no.2
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• pp.45-50
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• 2008

It has been found that the colony size of bacteria grown on an agar plate decreases with increasing agar gel concentration. Evidenc from recent studies suggests that the bacterial colony dynamics is closely related with the mechanical properties of the substrate. We investigate whether bacterial growth on the agar substrate is controlled mostly by the nutrients' diffusion which is hindered more in porous medium than in solution. The number of bacterial cells in single colonies is found to be inversely correlated with agar concentration. High-resolution live cell imaging at the single bacterium level confirms that the bacterial growth rate is reduced with increasing agar concentration. There is a strong correlation between the slowed diffusion and the reduced number of cells in a high concentration of agar medium.

• Journal of Microbiology and Biotechnology
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• v.16 no.4
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• pp.647-650
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• 2006

D-Psicose 3-epimerase (DPE) catalyzes the interconversion of D-fructose to D-psicose by epimerizing the carbon-3 position. The DPE from Agrobacterium tumefaciens was cloned and expressed in Escherichia coli. The expressed enzyme was purified by affinity chromatography on an IMAC, gel filtration chromatography on a Sephacryl S-300 HR, and anion-exchange chromatography on a RESOURCE Q. The molecular mass of the purified enzyme was estimated to be about 135 kDa by Superdex 200 gel filtration chromatography, corresponding to a homotetramer. The enzyme produced crystals suitable for X-ray diffraction to a $2.0{\AA}$ resolution at 100 K. The crystals were found to belong to the orthorhombic space group $P2_12_12_1$, with unit-cell parameters a=102.4, b=113.0, and $c=131.8{\AA}$. In addition, the calculated packing parameter $(V_m)$ was $2.79{\AA}^3/Da$, the solvent content was 55.92%, and an asymmetric unit consisted of four monomers.

• Journal of Plant Biotechnology
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• v.39 no.1
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• pp.81-92
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• 2012

Two-dimensional gel electrophoresis (2-DGE) is one of the most important technologies for high-resolution separation of proteins for proteomics. In this study, we present a detail 2-DGE protocol which allows detection and quantification of total plant proteins separated on gels to improve matching in image analysis. This protocol highlighted here may be useful for researchers, who like to first study for the development of protein biomarkers involved in development, biotic and abiotic stresses in plant.

• Applied Biological Chemistry
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• v.30 no.2
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• pp.163-168
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• 1987

A method, based upon the separation of cellular proteins by one-and two-dimensional electrophoresis was used for distinguishing butween Bradyrhizobium japonicum strains and Rhizobium fredii strains. Significant differences in protein pattern of one-dimensional SDS-PAGE vs-ere observed between Rhizobium fredii strains and Bradyrhizobium japonicum strains. The differences in six distinct main lands were observed among total 52 kinds of protein bands. Furthermore, the distribution of proteins in two groups by two-dimensional polyacrylamide gel electrophoresis was very different. The majority of visible proteins of Rhizobium fredii were acidic, whereas those of Bradyrhizobium japonicum were basic. In addition, amino acid composition was analyzed to detect the differences between two groups. No significant differences in amino acid composition were observed between Bradyrhizobium japonicum strains and Rhizobium fredii strains. The results indicate that one-and two-dimensional polyacrylamide gel electrophoresis were useful for identifying rhizobia isolates. One-dimensional SDS-PAGE of rhizobia proteins provided a rapid method for screening a large number of isolates, whereas two-dimensional electrophoresis was more of resolution and easiness for analyzing protein spots.

• Particle and aerosol research
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• v.6 no.2
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• pp.51-59
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• 2010

ZnO quantum dots embedded in a silica matrix without agglomeration were synthesized from $TEOS:Zn(NO_3)_2$ solutions in one-step process by aerosol-gel method. It was successfully demonstrated that the size of ZnO Q-dots could be controlled from 2 to 7 mm verified by a high resolution transmission electron microscope observation. The line scanning energy dispersive X-ray spectroscopy(EDS) revealed that the Q-dots existed preferentially inside SiO2 sphere when Zn/Si < 0.5. However, the Q-dots distributed homogeneously all over the sphere when Zn/Si > 1.0. Blue-shifted UV/Vis absorption peak observation confirmed the quantum size effect on the optical properties. The photoluminescence(PL) emission peaks of the powders at room temperature were consistent with previous reports in the following aspects: 1) PL characteristics are dominated by two peaks of deep-level defect-related emissions at 2.4 - 2.8 eV, 2) the first defect-related peak at 2.4 eV was blue shifted due to the quantum size effect with decreasing the concentration of $Zn(NO_3)_2$(decreasing the size of ZnO q dots). More interestingly, the existence of surface-exposed ZnO q dots affects greatly the second defect PL peak at 2.8 eV.