• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.245-252
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• 2007

Since the new millennium, truss PCMs(Periodic Cellular Metals) have drawn attention because of their superior specific stiffness, strength and multi-functionality. Prior studies have focused on the structural design and optimization. Kagome truss PCM has been proved to have the higher resistance to plastic buckling, more plastic deformation energy and lower anisotropy than other truss PCMs. In this study, we introduce a new idea to fabricate multi-layered Kagome truss PCM from continuous wires which can gain high strength as in piano wires and can be controlled to be defect free owing to drawing process. The relative density, the stiffness and the strength under bending and compressive load are estimated through elementary mechanics and compared with the results from experiments and FEA. The failure mechanisms are analyzed, and also mechanical performance and production are discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.737-744
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• 2017

A new ultralow density material (ULDM) named Shellular was recently introduced. Shellular has a periodic cellular structure with smooth-curved shells. The template for the first Shellular was fabricated using lithography and its shape was similar to the P-surface, a type of triply periodic minimal surface (TPMS). In this paper, a new fabrication method of Shellular with D-surface, named W-Shellular, is described. W-Shellular is fabricated based on weaving of polymer wires. The compressive properties are evaluated by experiments and analysis in comparison with the previous ULDMs.

• BMB Reports
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• v.56 no.11
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• pp.575-583
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• 2023

Mitochondria, fundamental cellular organelles that govern energy metabolism, hold a pivotal role in cellular vitality. While consuming dioxygen to produce adenosine triphosphate (ATP), the electron transfer process within mitochondria can engender the formation of reactive oxygen species that exert dual roles in endothelial homeostatic signaling and oxidative stress. In the context of the intricate electron transfer process, several metal ions that include copper, iron, zinc, and manganese serve as crucial cofactors in mitochondrial metalloenzymes to mediate the synthesis of ATP and antioxidant defense. In this mini review, we provide a comprehensive understanding of the coordination chemistry of mitochondrial cuproenzymes. In detail, cytochrome c oxidase (CcO) reduces dioxygen to water coupled with proton pumping to generate an electrochemical gradient, while superoxide dismutase 1 (SOD1) functions in detoxifying superoxide into hydrogen peroxide. With an emphasis on the catalytic reactions of the copper metalloenzymes and insights into their ligand environment, we also outline the metalation process of these enzymes throughout the copper trafficking system. The impairment of copper homeostasis can trigger mitochondrial dysfunction, and potentially lead to the development of copper-related disorders. We describe the current knowledge regarding copper-mediated toxicity mechanisms, thereby shedding light on prospective therapeutic strategies for pathologies intertwined with copper dyshomeostasis.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.28 no.2
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• pp.127-135
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• 2006

Objectives: The extent of bone formation that occurs at the interface of metallic implants and bone is determined by the number and activity of osteoblastic cells. Stress proteins may be contributing determinants of cell viability in altered environments. Hsp27 is a small Mr hsp which is known as a molecular chaperone. Methods: To better understand how heat shock protein 27 contributes to endosseous implant - associated metal ions affects on osteoblastic cell viability, the effect of chromium and titanium ions were compared to effects of cadmium ions in the ROS17/2.8 osteoblastic cell line. Results: ROS17/2.8 osteoblastic cell line demonstrated ion - specific reductions in growth; reductions were significantly greater for cadmium than for chromium or titanium. Chromium impaired growth of cultures without altering cell viability measured using the MTT assay. A stable transformed cell line expressing additional hsp27(clone "A7") was resistant to the toxic effects of titanium and partially protected from cadmium toxicity. Conclusions: A role for hsp27 in protection of osteoblastic cells from metal ion toxicity is supported by the chromium - induced elevations in hsp27 abundance and the behavior of the A7 cell line in response to metal ions in culture. Similar biochemical responses to altered cellular environments may contribute to the fate of tissues adjacent to select metallic implants.

• Journal of Microbiology and Biotechnology
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• v.30 no.8
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• pp.1261-1271
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• 2020

Cytochrome c_L (Cytc_L) is an essential protein in the process of methanol oxidation in methylotrophs. It receives an electron from the pyrroloquinoline quinone (PQQ) cofactor of methanol dehydrogenase (MDH) to produce formaldehyde. The direct electron transfer mechanism between Cytc_L and MDH remains unknown due to the lack of structural information. To help gain a better understanding of the mechanism, we determined the first crystal structure of heme c containing Cytc_L from the aquatic methylotrophic bacterium Methylophaga aminisulfidivorans MP^T at 2.13 Å resolution. The crystal structure of Ma-Cytc_L revealed its unique features compared to those of the terrestrial homologues. Apart from Fe in heme, three additional metal ion binding sites for Na⁺, Ca⁺, and Fe²⁺ were found, wherein the ions mostly formed coordination bonds with the amino acid residues on the loop (G93-Y111) that interacts with heme. Therefore, these ions seemed to enhance the stability of heme insertion by increasing the loop's steadiness. The basic N-terminal end, together with helix α4 and loop (G126 to Y136), contributed positive charge to the region. In contrast, the acidic C-terminal end provided a negatively charged surface, yielding several electrostatic contact points with partner proteins for electron transfer. These exceptional features of Ma-Cytc_L, along with the structural information of MDH, led us to hypothesize the need for an adapter protein bridging MDH to Cytc_L within appropriate proximity for electron transfer. With this knowledge in mind, the methanol oxidation complex reconstitution in vitro could be utilized to produce metabolic intermediates at the industry level.

• Journal of Ginseng Research
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• v.34 no.3
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• pp.198-204
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• 2010

Korean ginseng (Panax ginseng C.A. Meyer) preserved in syrup, known as ginseng Jung Kwa (GJK), is a popular traditional snack in Korea. We investigated the effects of heat processing time on total phenolic content and antioxidant capacity of GJK. Water extract was prepared from GJK with different heat processing times, 3 hours (GJK-3), 6 hours (GJK-6), or 12 hours (GJK-12), with sonication for 2 hours. The GJK extract contained total phenolic content in the following order: GJK-12 (2.28%)>GJK-6 (1.57%)>GJK-3 (1.29%). Both the peroxy and hydroxyl radical-scavenging activity and cellular antioxidant capacity of GJK extract was significantly enhanced with increasing heat processing time. The hydroxyl radical-scavenging activity of GJK-12 extract was greater than that of the GJK-3 and GJK-6 extracts, consistent with metal chelating capacity and reducing capacity. In a cellular model, the GJK extract effectively reduced 2,2'-azobis(2-amidinopropane) dihydrochloride, $Cu^{2+}$-, and $H_2O_2$-induced oxidative stress, with GJK-12 and GJK-6 extracts demonstrating greater cellular antioxidant capacity than the GJK-3 extract. These results suggest that heat processing time can contribute to the antioxidant capacity of GJK and that GJK extract may have the potential to be used as an effective dietary antioxidant to prevent oxidative stress-related diseases.

• Journal of Physiology & Pathology in Korean Medicine
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• v.21 no.1
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• pp.165-170
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• 2007

Pyungwi-san(PWS) have been using as a basic prescription of digestive disorder in Korean traditional medicine. This study was performed to examine the in vitro antioxidant activity of the extract using different antioxidant tests including by 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical scavenging, superoxide anion radical scavenging, metal chelating hydrogen peroxide scavenging, lipid peroxydation protective effect and scavenging effect of nitric oxide and peroxynitrite. Herbal-acupuncture solution of PWS(PWS-HS) exhibited a concentration-dependent inhibition of DPPH radical adduct formation and it showed dose-dependent free radical scavenging activity onto superoxide anions. In addition, the result of metal chelating hydrogen peroxide scavenging and ammonium thiocyanate experiments showed that PWS-HS was an active scavenger of hydroxyl radicals. Furthermore, it was also found to be effective in scavenging nitric oxide and peroxynitrite, well-known cytotoxic species that can oxidize several cellular components such as proteins, lipids and DNA.

• Molecules and Cells
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• v.23 no.1
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• pp.100-107
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• 2007

The moss Physcomitrella patens has two life cycles, filamentous protonema and leafy gametophore. A modified from of suppression subtractive hybridization (SSH), mirror orientation selection (MOS), was applied to screen genes differentially expressed in the P. patens protonema. Using reverse Northern blot analysis, differentially expressed clones were identified. The identified genes were involved mainly in metal binding and detoxification. One of these genes was an AP2 (APETALA2) domain-containing protein (PpACP1), which was highly up-regulated in the protonema. Alignment with other AP2/EREBPs (Ethylene Responsive Element Binding Proteins) revealed significant sequence homology of the deduced amino acid sequence in the AP2/EREBP DNA binding domain. Northern analysis under various stress conditions showed that PpACP1 was induced by ethephon, cadmium, copper, ABA, IAA, and cold. In addition, it was highly expressed in suspension-cultured protonema. We suggest that PpACP1 is involved in responses to metals, and that suspension culture enhance the expression of genes responding to metals.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.96-101
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• 2007

A new metallic sandwich panel with a quasi-Kagome truss core subjected to bending load has been analyzed. First, equations of the failure loads corresponding to the eight failure modes are presented. Then, non-dimensional forms of the equations are derived as functions of three geometric variables, one material parameter (yield strain), one load index and one weight index. Failure maps are presented for a given weight index. By using the dimensionless forms of equations as the design constraints, two kinds of optimization are performed. One is based on the weight, that is, the objective function, namely, the dimensionless load is to be maximized for a given weight. Another is based on the load, that is, the dimensionless weight is to be minimized for a given load. The results of the two optimization processes are found to agree each other. The optimized geometric variables are derived as a function of given weights or failure loads. The performance of the quasi-Kagome truss as the core of a sandwich panel is evaluated by comparison with those of honeycomb cored and octet truss cored panels

• Environmental Engineering Research
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• v.20 no.1
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• pp.41-50
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• 2015

The cyanobacterium Anabaena doliolum Ind1 isolated from a coal mining site was tested for removal of cadmium at optimum pH 7.0 and temperature $25^{\circ}C$. The organism recorded high percentage of metal removal (92-69%) within seven days of exposure to 0.5-2.0 ppm cadmium. Biosorption onto the cell surface was the primary mode of metal removal. Fourier transform infrared spectroscopy (FTIR) established hydroxyl, amides, carboxyl, sulphate and carbonyl groups to be the major functional groups on the cell surface involved in cadmium binding. Cellular ultrastructure and a range of vital physiological processes (i.e., photosynthetic pigments, respiration, photosynthesis, heterocyst frequency and nitrogenase activity) remained unaffected upon 0.5 ppm treatment; higher concentrations of cadmium exerted visible adverse effects. Amongst the five photosynthetic pigments tested, phycocyanin was the most targeted pigment (inhibition was 15-89%). Both respiration and photosynthetic activities were inhibited by cadmium with more severe effect seen on respiration. 2.0 ppm cadmium exposure also had drastic negative effect on nitrogenase activity (87% decreased).