• Journal of Biomedical Engineering Research
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• v.28 no.5
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• pp.647-656
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• 2007

The purpose of this study was to analyze the effects of vibratory stimulus as somatosensory inputs on the postural control in human standing. To study these effects, the center of pressure(COP) was observed while subjects were standing on a stable and an unstable support with co-stimulated mechanical vibrations to flexor ankle muscles(tibialis anterior tendon, achilles tendon) and two plantar zones on both foot. The COP sway measurement was repeated twice in four conditions: (1) with visual cue and vibration, (2) without visual cue and vibration, (3) with visual cue and without vibration, (4) without visual cue and with vibration. The calculated parameters were the COP sway area and the distance, the median frequency and the spectral energy of COP sway in three intervals $0.1{\sim}0.3,\;0.3{\sim}1,\;1{\sim}3Hz$. The results showed that vibratory stimulus affect postural stability. The reduction rate of the COP sway with vibratory stimulus were higher on the unstable support because the effect of postural stability increases when afferent nervous flow is more activated by vibration on unstable support. If unclear visual or vibratory information is received, one type of information is compared with the other type of sensory information. Then the input balance between visual and vibratory information is corrected to maintain postural stability. These findings are important for the rehabilitation system of postural balance control and the use of vibratory information.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2509-2513
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• 2010

In order to increase protease stability of a novel Trp-rich model antimicrobial peptide, $K_6L_2W_3$ (KLWKKWKKWLK-$NH_2$)and investigate the effect of L-amino acid to peptoid residue conversion on biological functions, we synthesized its antimicrobial peptoid, $k_6l_2w_3$. Peptoid $k_6l_2w_3$ had similar bacterial selectivity compared to peptide $k_66L_2W_3$. The bactericidal rate of $k_6l_2w_3$ was somewhat slower than that of $K_6L_2W_3$. Peptoid $k_6l_2w_3$ exhibited very little dye leakage from bacterial outer-membrane mimicking PE/PG liposomes, as observed in $K_6L_2W_3$, indicating that the major target site of $K_6L_2W_3$ and $k_6l_2w_3$ may be not the cell membrane but the cytoplasm of bacteria. Trypsin treatment of $K_6L_2W_3$ completely abolished antimicrobial activities against Escherichia coli and Staphylococcus aureus. In contrast, the antimicrobial activity of $k_6l_2w_3$ was completely preserved after trypsin treatment. Taken together, our results suggested that antimicrobial peptoid $k_6l_2w_3$ can potentially serves as a promising therapeutic agent for the treatment of microbial infection.

• BMB Reports
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• v.34 no.4
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• pp.355-364
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• 2001

Major human Nucleoside diphosphate kinases (NDPKs) exist as hetero-oligomers, consisting of NDPK-A and NDPK-B, rather than homo-oligomer. To investigate their biological function depending on the oligomeric structure in vivo, we characterized the biochemical properties of cellular NDPK. Cellular NDPKs, which are made up of a unique combination of isoforms, were purified from human erythrocyte and placenta. We found that cellular NDPK and recombinant isoforms NDPKs have their own distinct biochemical properties in autophosphorylation, stability toward heat or urea, and DNA binding. Cellular NDPK was found to have unique characteristics rather than the expected additive properties of recombinant isoforms. The mutations in the dimeric interface of NDPK-B (R34G, N69H or K135L) caused defective DNA binding and simultaneously reduced the enzymatic stability These results suggest that the oligomeric interaction could play a major role in the stability of catalytic domain and might be related to the regulation of various cellular functions of NDPK.

• Analytical Science and Technology
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• v.27 no.6
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• pp.339-346
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• 2014

The author assessed the availability of urine reference material for proficiency test provided for laboratories in occupational health. N-methylacetamide is the biomarker of exposure to N,N-dimethyl acetamide, which was used as the substitute for hepatotoxic N,N-dimethylformamide (DMF). N-methylacetamide (NMAC) urine samples of 3 different levels covering the 0.2~2 times of the exposure limit were tested. Stability test up to 180 days (0, 7, 30, 60, 180 days) at 4 different temperatures (-60, -20, 5, $25^{\circ}C$) and homogeneity test were performed for these samples. New analytical condition by GC/MSD using SIM mode (m/z 58, 59) and DB-624 column was investigated for better selectivity, sensitivity and resolution. Urinary NMAC samples showed good homogeneity for 3 levels. These samples also showed good stability up to 180 days. The data of stability and homogeneity of urinary DMAC confirmed the basis of including this item into Korean proficiency test for occupational health laboratories since 2008.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.337-342
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• 1997

Dental implant has been increasingly used to recover the masticatory unction of tooth. It has been well known that the success of dental implant is heavily dependent on initial stability and long-term osseointegration due to optimal stress distribution in the surrounding bones. The role of periodontal ligament, removed during operation, is to absorb impact force and to distribute them to alveolar bone. or this reason, the study for artificial periodontal ligament has become an important issue in this field. In this study, chitosan was coated on dental implant or the purpose of replacing the role of intact periodontal ligament. The results by experiment and FEM analysis showed : I) Initial stability of dental implant was significantly increased(35%) when the implant was coated with chitosan. II) The coated implant showed higher impact absorption, more even stress distribution and lower stress magnitude under impact force than uncoated implant. Accordingly, the micro-fracture of the surrounding bones due to impact force would be lessened by chitosan coating on dental implant.

• Food Science of Animal Resources
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• v.32 no.5
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• pp.618-626
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• 2012

Citrus (Citrus unshiu S. Marcoy) industry by-products were used as a source of dietary fiber, and the effects of dietary fiber extracted from citrus peel on the proximate composition, pH, color, protein solubility, cooking loss, emulsion stability, and apparent viscosity of a chicken emulsion in model systems were examined. Chicken emulsions were prepared by adding citrus peel fiber at four different concentrations (1, 2, 3, and 4%). The apparent viscosity, redness, and yellowness of the chicken emulsion with citrus peel fiber were higher than those of the control (p<0.05). The lightness values of the chicken emulsions were lower in treatments containing citrus peel fiber (p<0.05). Furthermore, moisture content, cooking loss, and emulsion stability of the chicken emulsion with 1-2% citrus peel fiber were higher than those of other treatments (p<0.05). Fat content was lower in the treatments with added citrus peel fiber than that in the control (p<0.05). Chicken emulsions with added citrus peel fiber had improved quality characteristics, and the best results were obtained for the chicken emulsion with 2% added citrus peel fiber.

• Journal of the Korea Society for Simulation
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• v.20 no.1
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• pp.51-59
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• 2011

This paper is concerned with locomotion of dog-like quadruped robots that can adapt to various terrains, mainly dealing with implementation methods and characteristics of static and dynamic gaits. To this end, a 12-DOF robot is built in house, motional trajectories of its body and feet are generated mimicking biological life, and the corresponding leg joint angles are analytically obtained by inverse kinematics. Such joint angle data are then applied to the robot's ADAMS model for computer simulations so that the planned walk and trot gaits are both confirmed dynamically stable. However, contrary to the simulation results, previous trot patterns showed unstable behavior during experiments. This problem led us to analyze the reason, and in the course we discovered the importance of maximally utilizing the concept of WSM rather than ZMP and therefore reducing the gait period to secure the stability of dynamic gaits such as trot.

• The Korean Journal of Ecology
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• v.18 no.1
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• pp.109-120
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• 1995

As the genetically modified microorganisms (GMMs) and their recombinant plasmid DNAs could be released into natural environments, their stabilities and impacts to indigenous microorganisls have become very importhant research subjects concerning with environmental and ecological aspects. In this study, the genetically modified E. coli CU103 and its recombinant pCU103 plasmid DNA, in which pcbCD genes involving in degradation of biphenyl and 4-chlorobiphenyl were cloned, were studied for their survival and stability in several different waters established under laboratory conditions. E. coli CU103 and its host E. coli XL1-Blue survived longer in sterile distilled water (SDW) and filtered autoclaved river water (FAW) than in filtered river water (FW). A lot of extracellular DNAs were released from E. coli CU103 by lytic action of phages in FW and the released DNAs were degraded by DNase dissolved in the water. Such effects of the factors in FW on stability of the recombinant pCU103 plasmid were also observed in the results of gel electrophoresis, quantitative analysis with bisbenzimide, and transformation assay. Therefore, the recombinant plasmids of pCU103 were found to be readily liberated from the genetically modified E. coli CU103 into waters by normal metabolic processes and lysis of cells. And the plasmid DNAs were quite stable in waters, but their stabilities could be affected by physicoKDICical and biological factors in non-sterile natural waters.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.40
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• pp.26.1-26.10
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• 2018

Background: This study aimed to evaluate the mechanical, biological, and esthetic stability of a zirconium abutment according to evidence-based dentistry. Main text: An electronic search was performed. Domestic studies were found using the keywords "zirconia abutments" and "zirconium abutment" in KMbase, KoreaMed, and the National Assembly Library, and international studies were found using the same keywords in PubMed. All identified studies were divided by evidence level from the viewpoint of the research type utilizing the evidence-based review manual. A total of 102 domestic studies (with Korean language) were found, and 9 of these studies were selected. In these nine studies, 3 had evidence level 3 and 6 had evidence level 4. A total of 97 international studies (with English language) were found, and 19 were selected. Among these 19 studies, 5 had evidence level 2 and 7 had evidence level 3, whereas the remainder had evidence level 4. According to the studies, zirconium abutments are mechanically, biologically, and esthetically stable, but the evidence level of these studies is low, and the follow-up duration is no longer than 5 years. Conclusions: All examined studies verified the mechanical stability of zirconium abutments for a period no longer than 5 years. Therefore, a long-term clinical observation is needed. Zirconium abutments are thought to be biologically stable, but they are not superior to titanium abutments. As the esthetic stability of such abutments had a low evidence level in the studies that examined here, a much higher evidence level is needed.

• Journal of Microbiology and Biotechnology
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• v.23 no.1
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• pp.7-14
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• 2013

In the Bacillus amyloliquefaciens ${\alpha}$-amylase (BAA), the loop (residues 176-185; region I) that is the part of the calcium-binding site (CaI, II) has two more amino acid residues than the ${\alpha}$-amylase from Bacillus licheniformis (BLA). Arg176 in this region makes an ionic interaction with Glu126 from region II (residues 118-130), but this interaction is lost in BLA owing to substitution of R176Q and E126V. The goal of the present work was to quantitatively estimate the effect of ionic interaction on the overall stability of the enzyme. To clarify the functional and structural significance of the corresponding salt bridge, Glu126 was deleted (${\Delta}$E126) and converted to Val (E126V), Asp (E126D), and Lys (E126K) by site-directed mutagenesis. Kinetic constants, thermodynamic parameters, and structural changes were examined for the wild-type and mutated forms using UV-visible, atomic absoption, and fluorescence emission spectroscopy. Wild-type exhibited higher $k_{cat}$ and $K_m$ but lower catalytic efficiency than the mutant enzymes. A decreased thermostability and an increased flexibility were also found in all of the mutant enzymes when compared with the wild-type. Additionally, the calcium content of the wild-type was more than ${\Delta}E126$. Thus, it may be suggested that ionic interaction could decrease the mobility of the discussed region, prevent the diffusion of cations, and improve the thermostability of the whole enzyme. Based on these observations, the contribution of loop destabilization may be compensated by the formation of a salt bridge that has been used as an evolutionary mechanism or structural adaptation by the mesophilic enzyme.