• Journal of the Microelectronics and Packaging Society
• /
• v.11 no.3 s.32
• /
• pp.63-70
• /
• 2004

The structural, electrical properties of $(Ba, Sr)TiO_3[BSTO]/RuO_2$ thin films were examined by the addition of amorphous BSTO layer between crystlline BSTO film and $RuO_2$ substrate. We prepared BSTO films with double-layered structure, that is, amorphous layers deposited at $60^{\circ}C$ and crystalline films. Crystalline films were prepared at 550 on amorphous BSTO layer. The thickness of the amorphous layers was varied from 0 to 170 nm. During the deposition of crystalline films, the crystallization of the amorphous layers occurred and the structure was changed to circular while crystalline BSTO films showed columnar structure. Due to insufficient annealing effect, amorphous BSTO phase was observed when the thickness of the amorphous layers exceeded 30 nm. Amorphous BSTO layer could also prevent the formation of oxygen deficient region in $RuO_2$ surface. Leakage current of total BSTO films decreased with increasing amorphous layer thickness due to structural modifications. Dielectric constant showed maxi-mum value of 343 when amorphous layer thickness was 30 nm at which the improvement by grain growth and the degradation by amorphous phase were balanced.

• Journal of the Microelectronics and Packaging Society
• /
• v.21 no.1
• /
• pp.13-17
• /
• 2014

The direct-patternable $SnO_2$ thin film was successfully fabricated by photochemical metal-organic deposition. The composition and chemical bonding state of $SnO_2$ thin film were analyzed by using X-ray photoelectron spectroscopy (XPS) from the surface to the interface with Si substrate. XPS depth profiling analysis allowed the determination of the atomic composition in $SnO_2$ film as a function of depth through the evolution of four elements of C 1s, Si 2p, Sn 3d, and O 1s core level peaks. At the top surface, nearly stoichiometric $SnO_2$ composition (O/Sn ratio is 1.92.) was observed due to surface oxidation but deficiency of oxygen was increased to the interface of patterned $SnO_2/Si$ substrate where the O/Sn ratio was about 1.73~1.75 at the films. This O deficient state of the film may act as an n-type semiconductor and allow $SnO_2$ to be applied as a transparent electrode in optoelectronic applications.

• Molecules and Cells
• /
• v.41 no.1
• /
• pp.35-44
• /
• 2018

Mitochondria are responsible for supplying of most of the cell's energy via oxidative phosphorylation. However, mitochondria also can be deleterious for a cell because they are the primary source of reactive oxygen species, which are generated as a byproduct of respiration. Accumulation of mitochondrial and cellular oxidative damage leads to diverse pathologies. Thus, it is important to maintain a population of healthy and functional mitochondria for normal cellular metabolism. Eukaryotes have developed defense mechanisms to cope with aberrant mitochondria. Mitochondria autophagy (known as mitophagy) is thought to be one such process that selectively sequesters dysfunctional or excess mitochondria within double-membrane autophagosomes and carries them into lysosomes/vacuoles for degradation. The power of genetics and conservation of fundamental cellular processes among eukaryotes make yeast an excellent model for understanding the general mechanisms, regulation, and function of mitophagy. In budding yeast, a mitochondrial surface protein, Atg32, serves as a mitochondrial receptor for selective autophagy that interacts with Atg11, an adaptor protein for selective types of autophagy, and Atg8, a ubiquitin-like protein localized to the isolation membrane. Atg32 is regulated transcriptionally and post-translationally to control mitophagy. Moreover, because Atg32 is a mitophagy-specific protein, analysis of its deficient mutant enables investigation of the physiological roles of mitophagy. Here, we review recent progress in the understanding of the molecular mechanisms and functional importance of mitophagy in yeast at multiple levels.

• Fisheries and Aquatic Sciences
• /
• v.7 no.4
• /
• pp.204-214
• /
• 2004

The effect of wind. stresses on the flow and water quality has been examined, particularly focused on the environment of oyster farms in Gamak Bay, by a two dimensional numerical model. In autumn (wind: $45.0^{\circ}$, 4.3 m/s), the overall flow turned out to be stronger than any other seasons and in addition, a pair of anticlockwise and clockwise vortices has been created at the northwest of the bay. Consequently, the wind in autumn seemed efficient not only for growing oyster but also for reducing the water pollution as the flow becomes much more active. In summer an anoxic condition appeared around the northwest of the bay where the flow is stagnant. According to a field survey, the majority of oyster farms tended to be densely distributed around the areas where DO concentration is high. Furthermore, oyster farms with a high production (over 1,300 kg per hanging string of 100 m) were distributed along with approximately 4 of Ch-a concentration. This suggests that oyster production is closely related to the concentration of DO or Ch-a.

• BMB Reports
• /
• v.40 no.1
• /
• pp.82-87
• /
• 2007

Our heterologous expression system of the human ferritin H-chain gene (hfH) allowed us to characterize the cellular effects of ferritin in yeasts. The recombinant Saccharomyces cerevisiae (YGH2) evidenced impaired growth as compared to the control, which was correlated with ferritin expression and with the formation of core minerals. Growth was recovered via the administration of iron supplements. The modification of cellular iron metabolism, which involved the increased expression of high-affinity iron transport genes (FET3 and FTR1), was detected via Northern blot analysis. The findings may provide some evidence of cytosolic iron deficiency, as the genes were expressed transcriptionally under iron-deficient conditions. According to our results examining reactive oxygen species (ROS) generation via the fluorescence method, the ROS levels in YGH2 were decreased compared to the control. It suggests that the expression of active H-ferritins reduced the content of free iron in yeast. Therefore, present results may provide new insights into the regulatory network and pathways inherent to iron depletion conditions.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.207.1-207.1
• /
• 2013

Tantalum oxide has been extensively investigated as one of the promising Resistive switching materials applicable to Resistive Dynamic Access Memories. Impedance spectroscopy offers simultaneous measurements of electrical and dielectric information, separation of electrical origins among bulk, grain boundaries, and interfaces, and the monitoring of electrical components. Such benefits have been combined with the resistive states of resistive switching devices which can be described in terms of equivalent circuits involving resistors, capacitors, and inductors, The current work employed pulsed laser deposition in order to prepare the oxygen-deficient tantalum oxide. The fabricated devices were controlled between highresistance and low-resistance states in controlled current compliance modes. The corresponding electrical phenomena were monitored both in the dc-based current-voltage characteristics and in the ac-based impedance spectroscopy. The origins of the electrical switching are discussed towards optimized ReRAM devices in terms of interfacial effects.

• Biomolecules & Therapeutics
• /
• v.19 no.4
• /
• pp.451-459
• /
• 2011

Peroxiredoxins (Prxs) have a critical role in protecting cells against oxidative damage generated by reactive oxygen species (ROS). PrxI and PrxII are more than 90% homologous in their amino acid sequences, and both proteins reduce $H_2O_2$. In this study, an over-expression plasmid carrying PrxI was transfected into $PrxII^{-/-}$ mouse embryonic fibroblasts (MEFs) to investigate potential compensatory relationships between PrxI and PrxII. ROS levels induced by oxidative stress were increased in $PrxII^{-/-}$ MEFs as compared to wild-type MEFs. Moreover, exposure of $PrxII^{-/-}$ MEFs to $H_2O_2$ caused a reduction in cell viability of about 10%, and the proportion of cell death was increased compared to mock-treated $PrxII^{-/-}$ MEFs. However, transient over-expression of PrxI in $PrxII^{-/-}$ MEFs conferred increased resistance against the oxidative damage, as evidenced by increased cell viability and reduced intracellular ROS levels under $H_2O_2$ stress conditions. The findings suggest that over-expressed PrxI can partly compensate for the loss of PrxII function in PrxII-deficient MEFs.

• Journal of Microbiology and Biotechnology
• /
• v.33 no.12
• /
• pp.1681-1691
• /
• 2023

Flavin mononucleotide-binding proteins or domains emit cyan-green fluorescence under aerobic and anaerobic conditions, but relatively low fluorescence and less thermostability limit their application as reporters. In this work, we incorporated the codon-optimized fluorescent protein from Chlamydomonas reinhardtii with two different linkers independently into the redox-responsive split intein construct, overexpressed the precursors in hyperoxic Escherichia coli SHuffle T7 strain, and cyclized the target proteins in vitro in the presence of the reducing agent. Compared with the purified linear protein, the cyclic protein with the short linker displayed enhanced fluorescence. In contrast, cyclized protein with incorporation of the long linker including the myc-tag and human rhinovirus 3C protease cleavable sequence emitted slightly increased fluorescence compared with the protein linearized with the protease cleavage. The cyclic protein with the short linker also exhibited increased thermal stability and exopeptidase resistance. Moreover, induction of the target proteins in an oxygen-deficient culture rendered fluorescent E. coli BL21 (DE3) cells brighter than those overexpressing the linear construct. Thus, the cyclic reporter can hopefully be used in certain thermophilic anaerobes.

• Korean Journal of Environmental Agriculture
• /
• v.5 no.2
• /
• pp.149-155
• /
• 1986

The fatty acid compositions of phospholipids extracted from leaves and leaf mitochondria, which were sampled from several horicultural plants grown under blue color-deficient sunlight (BCDS), were determined and compared with those from plants grown under natural white colored sunlight(WCS). It was found that the mitochondria isolated from plants grown under BCDS contained phospholipid whose degree of unsaturation in unit of number of double bonds per lipid molecule was remarkably higher than that from plants grown under WCS, the relative increment being $8{\sim}49%$. This was significantly larger than the relative increment, $4{\sim}8%$ for total phospholipid extracted from whole leaves grown under BCDS campared to WCS. This observation demonstrated that the blue light effect of sunlight on the chemical property of cellular membranes, as long as it was concerned with fatty acid composition, arose mainly at the mitochondrial membrane. Also observing that the degree of unsaturation of mitochondrial phospholipid was much lower than that of total phospholipid, it was interpreted that this was the consequence of rather active oxidative destruction of lipid-fatty acid components occuring in mitochondrial membrane by the reactive oxygen species, especially superoxide($O_2-$), which was known to be produced in mitochondrial inner membrane through the side reactions of the respiratory electron transport chain and also probably through the photosensitized reaction involving oxygen induced by blue colored light. Thus, it may be tentatively concluded that the extent of photosensitization in mitochondrial membrane could be considerably reduced under BCDS resulting in lowering of the $O_2-$ level in the respirating organelle The possible involvement of photodynamic action in membrane oxidation was also indicated by the fact that the typical fat-soluble antioxidant, ${\alpha}-tocopherol$, was found to be contained on a higher level in leaves under BCDS than those under WCS.

• Journal of Marine Life Science
• /
• v.2 no.2
• /
• pp.62-69
• /
• 2017

In order to assess the potential environmental factors in the vicinity of a fish cage farm, we investigated the biotic and abiotic factors during a short-term period in summer 2016 in two inner stations of Tongyeong Obi. High water temperature on August 10^th was apparent among the full depth of up to 29℃, which might have been related to the abnormally high temperatures of large amounts of the Changjiang River discharge along the Tongyeong coast. The concentration of nitrate+nitrite, ammonium, phosphate, and silicate ranged from 0.08 to 5.11 μM, 0.08 to 34.62 μM, 0.01 to 1.15 μM, and 1.46 to 31.79 μM, respectively. The nutrients were mainly supplied by precipitation and leaching from the bottom sediments in the fish culture farm area. It was not retained for a long duration because of the phytoplankton consumption and diffusion by water currents. The chlorophyll a concentration varied from 0.49 ㎍ l^-1 to 7.39 ㎍ l^-1. At that time, Chaetoceros debilis, C. pseudocurvisetus, and Pseudo-nitzschia delicatissima were rapidly proliferated and reached the level of 4.74 × 10⁹ cells l^-1. In particular, the lowest dissolved oxygen was recorded at 4.52 ㎍ l^-1 at the bottom layer after bloom. Therefore, even though phytoplankton blooms in summer have frequently occurred in a fish culture farm area, the oxygen-deficient environments were not found in neither the surface nor bottom layers, which implied that the water masses might be well exchanged from the mouth of the northwest and southeast between Obi and Mireuk Island in the study area.