• The Korean Journal of Physiology and Pharmacology
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• v.19 no.2
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• pp.167-175
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• 2015

A retinal prosthesis is being developed for the restoration of vision in patients with retinitis pigmentosa (RP) and age-related macular degeneration (AMD). Determining optimal electrical stimulation parameters for the prosthesis is one of the most important elements for the development of a viable retinal prosthesis. Here, we investigated the effects of different charge-balanced biphasic pulses with regard to their effectiveness in evoking retinal ganglion cell (RGC) responses. Retinal degeneration (rd1) mice were used (n=17). From the ex-vivo retinal preparation, retinal patches were placed ganglion cell layer down onto an $8{\times}8$ multielectrode array (MEA) and RGC responses were recorded while applying electrical stimuli. For asymmetric pulses, 1st phase of the pulse is the same with symmetric pulse but the amplitude of 2nd phase of the pulse is less than $10{\mu}A$ and charge balanced condition is satisfied by lengthening the duration of the pulse. For intensities (or duration) modulation, duration (or amplitude) of the pulse was fixed to $500{\mu}s$($30{\mu}A$), changing the intensities (or duration) from 2 to $60{\mu}A$(60 to $1000{\mu}s$). RGCs were classified as response-positive when PSTH showed multiple (3~4) peaks within 400 ms post stimulus and the number of spikes was at least 30% more than that for the immediate pre-stimulus 400 ms period. RGC responses were well modulated both with anodic and cathodic phase-1st biphasic pulses. Cathodic phase-1st pulses produced significantly better modulation of RGC activity than anodic phase-1st pulses regardless of symmetry of the pulse.

• Analytical Science and Technology
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• v.7 no.1
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• pp.103-114
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• 1994

The elution behaviors of Ni(II), Cu(II), Co(II), and Cr(II) in 1-phenyl-3-methyl-4(2-hydroxy-5-X-phenylazo)-5-pyrazolone, [Pm(2-OH)(5-X)PaPz](X=H, $CH_3$, $NO_2$, Cl) chelates have been studied by reversed phase HPLC. Thirteen metal-[Pm(2-OH)(5-X)PaPz] chelates were prepared and characterized by UV, IR, MS, and ICP spectroscopic methods. These metal-2-hydroxyarylazopyrazolone chelates were successfully separated on Novapak-$C_{18}$ column using methanol/water mixtures as a mobile phases. It was found that the chelates were eluted properly in an acceptable range of the capacity factor value($0{\leq}log\;k^{\prime}{\leq}1$). The dependence of the capacity factor(log k') on the volume fraction of water in the binary mobile phase showed a good linearity. Also, there was a good linear dependence of the capacity factor on the liquid-liquid extraction distribution ratio($D_c$) in methanol-water/n-pentadecane extraction system by the batch method. It suggested that the retention of the chelates in the reverse phase liquid chromatographic system be largely due to the solvophobic effect.

• Mass Spectrometry Letters
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• v.5 no.2
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• pp.42-48
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• 2014

A specific and sensitive liquid chromatography-electrospray ionization tandem mass spectrometry method (LC-ESI-MS/MS) was developed and validated for the simultaneous quantification of porphyrins (coproporphyrin, pentacarboxylporphyrin, hexacarboxylporphyrin, heptacarboxylporphyrin, and uroporphyrin) in human plasma and urine. Acidified plasma samples and urine samples were prepared by using liquid-liquid extraction using ethyl acetate and protein precipitation with acetonitrile, respectively. The separation was achieved onto a Synergi Fusion RP column ($150mm{\times}2.0mm$, $4{\mu}m$) with a gradient elution of mobile phase A (0.1% formic acid in 2 mmol/L ammonium acetate, v/v) and mobile phase B (20% methanol in acetonitrile, v/v) at a flow rate of $450{\mu}L$/min. Porphyrins and the internal standard (IS), coproporphyrin I-$^{15}N_4$, were detected by a tandem mass spectrometer equipped with an electrospray ion source operating in positive ion mode. Multiple reaction monitoring (MRM) transitions of the protonated precursor ions and the related product ions were optimized to increase selectivity and sensitivity. The proposed method was validated by assessing selectivity, linearity, limit of quantification (LOQ), precision, accuracy, recovery, and stability. The calibration curves were obtained in the range of 0.1-100 nmol/L and the LOQs were estimated as 0.1 nmol/L for all porphyrins. Results obtained from the validation study of porphyrins showed good accuracy, precision, recovery, and stability. Finally, the proposed method was successfully applied to clinical studies on the autism spectrum disorder (ASD) diagnosis of 203 Korean children.

• Journal of Environmental Health Sciences
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• v.39 no.5
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• pp.408-417
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• 2013

Objectives: Phthalates are used as plasticizers in polyvinyl chloride (PVC) plastics. As phthalate plasticizers are not chemically bound to the PVC, they can leach, migrate or evaporate into indoor air and atmosphere, foodstuffs, other materials, etc. Therefore, humans are exposed through ingestion, inhalation, and dermal exposure over their entire lifetime, including during intrauterine development. In particular, university students have a great number of opportunities to contact products including phthalates during campus life (food packaging, body care products, cosmetic, lotions, aftershave, perfume etc.). The purpose of this study was to examine levels of phthalate exposure as undergraduate students begin to use pharmaceuticals and personal care products including phthalates. Methods: Phthalate metabolites, mono-ethyl phthalate (MEP), mono-n-butyl phthalate (MnBP), mono-isobutyl phthalate (MiBP), mono-2- ethylhexyl phthalate (MEHP), {(mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP}, and mono-(2-ethlyl-5-oxohexyl) phthalate (MEOHP} were examined. 80 urine samples collected from university students were analyzed using LC/MS/MS(API 4000, Applied Bioscience) with on-line enrichment and columnswitching techniques. This study was carried out at Y university located in Gyonggi Province from 2008 to 2011. Results: The detection limit of phthalate metabolites were 0.03 ng/mL for MEP, 0.11 ng/mL for MnBP, 0.08 ng/mL for MiBP, 0.93 ng/mL for MEHP, 0.19 ng/mL for MEOHP and 0.16ng/mL for MEHHP. MnBP showed the highest urinary levels (median: 31.6 ug/L, 24.8 ug/g creatinine (cr)). Concentrations were also high for MEHHP (median: 24.1 ug/L, 19.0 ug/g cr), followed by MEOHP (median: 22.8 ug/L, 17.9 ug/g cr). In individual cases, the maximum level reached up to 348 ug/L, and 291 ug/g cr, respectively. The urinary and creatinine adjusted levels of MEP were lower than those for DBP and DEHP metabolites, but were higher in 95th percentiles. As a result, the mean daily DEP intake value was 2.3 ${\mu}g/kg$ bw/day, 3.5 ${\mu}g/kg$ bw/day for DEHP and 4.9 ${\mu}g/kg$ bw/day for DBP. Conclusion: These students' phthalate exposure levels were below the international safe level set by the EU, but higher than the 2012 KFDA survey of the age group from 3 to 18.

• Microbiology and Biotechnology Letters
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• v.31 no.3
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• pp.216-223
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• 2003

A 1.3-kb of chitosanase gene (choA) encoding 45-kDa polypeptide was cloned, expressed, and characterized from a newly isolated Bacillus cereus H-1. The chitosanase protein (ChoA) of B. cereus H-l was purified to homogeneity by ammonium sulfate precipitation and CM-sephadex column chromatography. Optimum pH was around 7, and stable pH range in the incubation at 50 C was 4-11. Optimum temperature was around 50 C, and enzyme activity was relatively stable below 45 C. ChoA showed the activities toward carboxymethyl cellulose (CMC) in addition to soluble or glycol chitosan. Based on MALDI-TOF MS analysis of purified ChoA, the entire amino acid sequence of ChoA was interpreted by database searching of previously known Bacillus chitosanases. A 1.6 kb of PCR product of corresponding chitosanase gene was obtained and its DNA sequence was determined. The deduced amino acid of choA revealed that ChoA have a 98% homology with those of Bacillus sp. No.7-M strain and Bacillus sp. KCTC0377BP. The recombinant ChoA protein was expressed in E. coli DH5$\alpha$. Deduced amino acid comparison of choA with other chitosanases suggested that it belongs to family 8 microbial endo-chitosanase with chitosanase-cellulase activity.

• Journal of Microbiology and Biotechnology
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• v.25 no.2
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• pp.152-161
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• 2015

CodY is a highly conserved protein in low G+C gram-positive bacteria that regulates genes involved in sporulation and stationary-phase adaptation. Bacillus thuringiensis is a grampositive bacterium that forms spores and parasporal crystals during the stationary phase. To our knowledge, the regulatory mechanism of CodY in B. thuringiensis is unknown. To study the function of CodY protein in B. thuringiensis, BMB171codY^- was constructed in a BMB171 strain. A shuttle vector containing the ORF of cry1Ac10 was transformed into BMB171 and BMB171codY^-, named BMB171cry1Ac and BMB171codY^-cry1Ac, respectively. Some morphological and physiological changes of codY mutant BMB171codY^-cry1Ac were observed. A comparative proteomic analysis was conducted for both BMB171codY^-cry1Ac and BMB171cry1Ac through two-dimensional gel electrophoresis and MALDI-TOF-MS/MS analysis. The results showed that the proteins regulated by CodY are involved in microbial metabolism, including branched-chain amino acid metabolism, carbohydrate metabolism, fatty acid metabolism, and energy metabolism. Furthermore, we found CodY to be involved in sporulation, biosynthesis of poly-β-hydroxybutyrate, growth, genetic competence, and translation. According to the analysis of differentially expressed proteins, and physiological characterization of the codY mutant, we performed bacterial one-hybrid and electrophoretic mobility shift assay experiments and confirmed the direct regulation of genes by CodY, specifically those involved in metabolism of branched-chain amino acids, ribosomal recycling factor FRR, and the late competence protein ComER. Our data establish the foundation for in-depth study of the regulation of CodY in B. thuringiensis, and also offer a potential biocatalyst for functions of CodY in other bacteria.

• Korean Journal of Medicinal Crop Science
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• v.11 no.5
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• pp.352-357
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• 2003

Volatile flavor compounds Angelica gigas Nakai and Angelica acutiloba Kitagawa were extracted by SDE (simultaneous steam distillation & extraction) using the mixture of n-pentane and diethylether (1:1, v/v) as an extract solvent and analyzed by GC-FID and GC-MS. The amount of essential oils of top part and root in Angelica gigas were obtained in 0.063% (v/w) and 0.389% (v/w) yields as a fresh weight base, respectively. The main compounds in top parts and the root were identified as nonane (7.51% and 24.49%, respectively), ${\alpha}-pinene$ (14.64% and 31.75%), limonene+${\beta}-phellandrene$ (14.01% and 9.66%), ${\gamma}-terpinene$ (7.85% and 1.20%), germacrene-d (5.85% and 0.22%), (E,E)-${\alpha}-farnesene$ (6.05% and 1.40%), ${\beta}-eudesmol$ (5.26% and 1.84%). Although these compounds were present in both parts. The results showed large differences in. the concentrations of them much varied. The amount of essential oils stem and leaf obtained (0.068% and 0.127% in A. gigas) and (0.153% and 0.243% in A. acutiloba) yields as a fresh weight base, respectively. More than 18 and 32 components in stem and leaf have been identified, which of main components in A. gigas were ${\alpha}-pinene$, myrcene, limonene, germacrene-d, eudesmol and butylphthalide, but germacrene-d and butylphthalide contents were also different in stem and leaf. And more than 21 and 32 components in A. acutiloba were ${\gamma}-terpinene$ and butylphthalide. Volatile compounds were very different in both species.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.5
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• pp.642-653
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• 2006

Purpose : The purpose of this study was to investigate the effect of the output energy(voltage) of laser welding on the strength and properties of joint of cast titanium(CP Gr II) and titanium alloy(Ti-6Al-4V). Material and method : Cast titanium and its alloy rods(ISO6871) were prepared and perpendicularly cut at the center of the rod. After the cut halves were fixed in a jig, and the joints welded with a laser-welding machine at several levels of output voltage of $200V{\sim}280V$. Uncut specimens served as the non-welded control specimens The pulse duration and pulse spot size employed in this study were 10ms and 1.0mm respectively. Tensile testing was conducted at a crosshead speed of 0.5mm/min. The ultimate tensile strength(MPa) was recorded, and the data (n=6) were statistically analyzed by one-way analysis of variance(ANOVA) and Scheffe's test at ${\alpha}$=0.05. The fracture surface of specimens investigated by scanning electron microscope (SEM). Vickers microhardness was measured under 500g load of 15seconds with the optimal condition of output voltage 280V. Results : The results of this study were obtained as follows, 1. When the pulse duration and spot size were fixed at 10ms and 1.0mm respectively, increasing the output energy(voltage) increased UTS values and penetration depth of laser welded to titanium and titanium alloy. 2. For the commercial titanium grade II, ultimate tensile strength(665.3MPa) of the specimens laser-welded at voltage of 280V were not statistically(p>0.05) different from the non-welded control specimens (680.2MPa). 3. For the titanium alloy(Ti-6Al-4V), ultimate tensile strength(988.3MPa) of the specimens laser-welded at voltage of 280V were statistically(p<0.05) different from the non-welded control specimens (665.0MPa). 4. The commercial titanium grade II and titanium alloy(Ti-6Al-4V) were Vickers microhardness values were increased in the fusion zone and there were no significant differences in base metal, heat-affected zone.

• Korean Journal of Food Science and Technology
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• v.45 no.6
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• pp.777-784
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• 2013

The ethyl acetate (EtOAc) layer of Canavalia gladiata (sword bean) methanol extracts showed higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity than other layers. Four phenolic compounds were isolated from the EtOAc layer by silica gel column chromatography and prep-HPLC using a guided DPPH radical-scavenging assay. The isolated compounds were identified as methyl gallate (1), gallic acid (2), 1,6-di-O-galloyl ${\beta}$-$\small{D}$-glucopyranoside (3), and 1,4,6-tri-O-galloyl ${\beta}$-$\small{D}$-glucopyranoside (4) based on MS and NMR analyses. Among the four compounds, no. 4 was isolated from this plant for the first time. Their DPPH radical-scavenging activities based on $SC_{50}$ decreased in the following order: 4 (6.9 ${\mu}M$)>3 (8.3 ${\mu}M$)>2 (10.0 ${\mu}M$)>1 (10.3 ${\mu}M$).

• Journal of Korean Society of Forest Science
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• v.101 no.4
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• pp.640-647
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• 2012

A metabolomic study was conducted to identify key metabolic components, which are correlated with the growth of 4-year-old Pinus koraiensis seedlings harvested at actively height growing season (May 18th). Among 105 individual metabolites identified by GC/MS analysis, alanine, threonine, oleic acid, and butanoic acids were negatively correlated with both height and weight of 4-year-old seedlings, while malic acid, xylose, glucose, d-turanose and inositol had positive correlation with various growth parameters. During the actively growing season, the concentrations of both amino acids and organic acids in the main stem of Superior seedling group were lower but the photosynthates such as mono-saccharide and sucrose were higher than in other seedling groups such as Intermediate and Inferior. Interestingly, d-turanose, an analogue of sucrose that is not metabolized in higher plants but used as carbon source by many organisms including numerous species of bacteria and fungi, showed the highest correlation (r=0.896, p<0.001) with height of 4-year-old seedlings, indicating that possible interaction with mycorrhizal organisms. Therefore we suggest that several metabolites selected in this study may be used as metabolic markers for complex traits in P. koraiensis.