• Journal of Life Science
• /
• v.9 no.1
• /
• pp.26-34
• /
• 1999

A thermostable pullulanase has been isolated and purified from Thermus caldophilus GK-24 to a homogeneity by gel-filtration and ion-exchange chromatography. The specific activity of the purified enzyme was 431-fold increase from the crude culture broth with a recovery of 11.4%. The purified enzyme showed $M_{r}$ of 65 kDa on denaturated and natural conditions. The pI of the enzyme was 6.1 and Schiff staining was negative, suggesting that the enzyme is not a glycoprotein. The enzyme was most active at pH 5.5. The activity was maximal at $75^{\cire}C$ and stable up to $95^{\cire}C$ for 30 min at pH 5.5. The enzyme was stable to incubation from pH 3.5 to pH 8.0 at $4^{\cire}C$ for 24hr. The presence of pullulan protected the enzyme from heat inactivation, the extent depending upon the substrate concentration. The activity of the enzyme was simulated by $Mn^{2+}$ ion, }$Ni^{2+}$, $Ca^{2+}$, $Co^{2+}$ ions. The enzyme hydrolyzed the ${\alpha}$-1,6-linkages of amylopectin, glycogens, ${\alpha}$, ${\beta}$-limited dextrin, and pullulan. The enzyme caused the complete hydrolysis of pullulan to maltotriose and the activity was inhibited by $\alpha$, $\beta$, or $\gamma$-cyclodextrins. The $NH_{2}$-terminal amino acid sequence [(Ala-Pro-Gln-(Asp of Tyr)-Asn-Leu-Leu-Xaa-ILe-Gly-Ala(Ser)] was compared with known sequences of various sources and that was compared with known sequences of various sources and that was different from those of bacterial and plant enzymes, suggesting that the enzymes are structurally different.

• Korean Journal of Computational Design and Engineering
• /
• v.9 no.4
• /
• pp.416-424
• /
• 2004

In this paper, the heat transfer analysis and thermal stress analysis of the PCB(Printed Circuit Board) equipped in electronic Packages are carried out for various may types of chips on the PCB. And two structural PCB models are used in the analyses. The electronic chips on the PCB usually emit heat and this heat generates the thermal stress around the chip. The thermal load due to the heat generation of chips on the PCB may cause the malfunction of the electronic packages such as a monitor. a computer etc. Hence, the PCB should be designed to withstand these thermal loads. In this paper, the heat transfer analysis and thermal stress analysis are executed for the PCB model with pins and the analysis results are compared with the results for the PCB model without pins. The analysis results show that the PCB model without pins is not good for the thermal stress analysis of PCB, even though these two models have similar heat transfer characteristics. The analysis results also show that the highest thermal stress occurs in the pin especially attached to the highest temperature chip, and the PCB constrained to the electronic package on the long side is structurally more stable than other cases. The analyses of the PCB are executed using the finite element analysis code, NISA.

• Toxicological Research
• /
• v.30 no.2
• /
• pp.109-116
• /
• 2014

Glucosinolates (GLSs) are abundant in cruciferous vegetables and reported to have anti thyroidal effects. Four GLSs (sinigrin, progoitrin, glucoerucin, and glucotropaeolin) were administered orally to rats, and the breakdown products of GLSs (GLS-BPs: thiocyanate ions, cyanide ions, organic isothiocyanates, organic nitriles, and organic thiocyanates) were measured in serum. Thiocyanate ions were measured by colorimetric method, and cyanide ions were measured with CI-GC-MS. Organic isothiocyanates and their metabolites were measured with the cyclocondensation assay. Organic nitriles and organic thiocyanates were measured with EI-GC-MS. In all treatment groups except for progoitrin, thiocyanate ions were the highest among the five GLS-BPs. In the progoitrin treated group, a high concentration of organic isothiocyanates (goitrin) was detected. In the glucoerucin treated group, a relatively low amount of goitrogenic substances was observed. The metabolism to thiocyanate ions happened within five hours of the administration, and the distribution of GLSs varied with the side chain. GLSs with side chains that can form stable carbocation seemed to facilitate the degradation reaction and produce a large amount of goitrogenic thiocyanate ions. Because goitrogenic metabolites can be formed without myrosinase, the inactivation of myrosinase during cooking would have no effect on the anti-nutritional effect of GLSs in cruciferous vegetables.

• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.5
• /
• pp.491-496
• /
• 2015

Electric handbike can be easily detachable to various sizes of manual wheelchair and the elderly and people with disabilities can use them easily. Therefore, connectors used for coupling between the handbike and manual wheelchair must secure structural stability for occupant safety. However, related research is rare. The aim of this study is to find the connector with highly structural stability by comparing static and dynamic mechanical characteristics among three typical connectors(a snatch lock, a slide latch, and a fastener) by computational simulations. To perform static and dynamic simulation, we referred to durability test based on Korean Standards and then calculated mechanical stresses in connectors. The results showed that the snatch lock addressed the lowest von-mises stress under the same mechanical condition. Therefore when using the combination of a handbike and a wheelchair, we concluded that the snatch lock is considered as the structurally stable connector to structural stability and usability.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.13 no.3
• /
• pp.49-55
• /
• 2014

This paper examines the effects of spring characteristics and stiffness in relation to the characteristics of hydrodynamic force. Spring forces and stiffness determine the performance of this type of pan check valve and have an effect on the overall operation. The hydraulic efficiency of the pan check valve is relatively low compared to that of a common check valve. However, a pan check valve is structurally more stable than a common check valve. We implemented the optimum design to increase the flow rate and to resolve the suppression of the pressure drop according to the extent of the compression of the spring. From the results of a flow analysis, we demonstrate spring stiffness design criteria depending on the extent of the compression of the spring of pan check valve acting on the fluid at the inlet 1 MPa pressure.

• Journal of the Society of Naval Architects of Korea
• /
• v.50 no.3
• /
• pp.153-159
• /
• 2013

The power transmission system has always been considered critical for a human powered boat(or water bike) since it first showed up at Human Powered Vessel Festival. Mechanical problems, such as abrasions and other damages of the gear system for the power transmission, lead to poor durability and low efficiency of a boat. This paper described mechanical problems and a design process of power transmission system and then suggested the method to solve the problems. It is selected a module and a type of gears that are structurally stable thus can transmit the power durable. Especially the lower gear box is applied to CRP(contra rotating propeller) system for improving the structural stability and the propeller efficiency as well. As the results, the upper and lower gear box are designed and manufactured. And from the trial test, it is confirmed that the power transmission system is reliable.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.31 no.7
• /
• pp.510-514
• /
• 2018

This study discusses and demonstrates the structural stability of highly ordered Pt patterns formed on a transparent and flexible substrate through the process of nanotransfer printing (nTP). Bending tests comprising approximately 1,000 cycles were conducted for observing Pt line patterns with a width of $1{\mu}m$ formed along the direction of the horizontal (x-axis) and vertical (y-axis) axes ($15mm{\times}15mm$); and adhesion tests were performed with an ultrasonicator for a period greater than ten minutes, to analyze the Pt crossbar patterns. The durability of both types of patterns was systematically analyzed by employing various microscopes. The results show that the Pt line and Pt crossbar patterns obtained through nTP are structurally stable and do not exhibit any cracks, breaks, or damages. These results corroborate that nTP is a promising nanotechnology that can be applied to flexible electronic devices. Furthermore, the multiple patterns obtained through nTP can improve the working performance of flexible devices by providing excellent structural stability.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.12
• /
• pp.3707-3710
• /
• 2010

A chromo/fluorogenic $NO_2S_2$-macrocycle L functionalized with nitrobenzofurazan unit as a dual-signaling probe was synthesized and structurally characterized by single crystal X-ray analysis. In a cation-induced color change experiment, L exhibited excellent $Hg^{2+}$ ion selectivity by showing the color change from orange-red to yellow. However, this hypochromic shift by $Hg^{2+}$ was observed for the weaker coordinating anion system such as ${NO_3}^-$ and ${ClO_4}^-$ ions. The observed anion effect is due to the strong coordination of anions inhibits the bond formation between $Hg^{2+}$ and the macrocyclic tert-N atom, which is sensitive to induce the color change. In the fluorometric experiment, L showed chelate-enhanced fluorescence change effect only with $Hg^{2+}$ ion, together with a change from yellow to green emission. The sensing ability for $Hg^{2+}$ with the proposed chemosensor L is due to the stable complexation with 1:1 stoichiometry (metal-to-ligand).

• The Korean Journal of Physiology and Pharmacology
• /
• v.2 no.3
• /
• pp.385-393
• /
• 1998

Human neutrophil elastase (HNElastase, EC 3.4.21.37), a causative factor of inflammatory diseases, was purified by Ultrogel AcA54 gel filtration and CM-Sephadex ion exchange chromatography. HNElastase was inhibited by phenylbutazone in a concentration dependent manner up to 0.4 mM, but as the concentration increased, the inhibitory effect gradually diminished. Binding of phenylbutazone to the human neutrophil elastase caused strong Raman shifts at 200, 440, and 1194 $cm^{-1}$. The peak at 1194 $cm^{-1}$ might be evidence of the presence $of\;-N=N-{\Phi}$ radical. The core area of the elastase, according to the visual molecular model of human neutrophil elastase, was structurally stable. A deeply situated active center was at the core area surrounded by hydrophobic amino acids. Directly neighboring the active site was one positively charged atom and two atoms carrying a negative charge, which enabled the enzyme and the drug to form a strong interaction. Phenylbutazone may form a binding, similar to a key & lock system to the atoms carrying opposite charges near the active site of the enzyme molecule. Furthermore, the hydrophobicity of the surrounding amino acid near the active site seemed to enhance the binding strength of phenylbutazone. Binding of phenylbutazone near the active site may cause masking of the active site, preventing the substrate from approaching the active site and inhibiting elastase activity.

• Bulletin of the Korean Chemical Society
• /
• v.18 no.6
• /
• pp.644-648
• /
• 1997

Introduction of an alkyl substituent at the $C_{4\beta}$ position of antimalarial trioxanes has caused them to become more active in their antimalarial activity. We have designed a structurally simple 4β-phenyl substituted trioxane (3) as an active antimalarial since it can form a more stable carbon radical when reacting with ferrous bromide. The trioxane 3 has been prepared along with the corresponding isomer 4 according to the previously reported procedure. The synthesized trioxanes 3 and 4 were finally separated by using HPLC and assigned their stereochemistry by spectroscopy and X-ray crystallography. Their antimalarial activities were surprisingly low. The low activity was then rationalized based on the product distribution of the ferrous ion induced reaction of these trioxanes. These trioxanes with ferrous bromide did not produce any detectable amount of the corresponding $C_4$-hydroxylated product, consistent with the fact that neither $C_{4\beta}$-phenyl substituted nor $C_{4\alpha}$-phenyl substituted trioxane has any antimalarial activity. It implies that a $C_4$ substituent of antimalarial trioxanes has to stabilize an adjacent carbon-centered radical in a specific stability range in order to show a good antimalarial activity. This study, combined with related studies, could help develop more potent antimalarial trioxanes.