• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.277-282
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• 2010

Durability of automotive polymer electrolyte membrane fuel cell (PEMFC) strongly depends the startup/shutdown procedure. Formation of hydrogen/air boundary in the anode gas channel, so-called reverse current condition, particularly induces fast degradation of the cathode. Under the reverse current condition, high voltage is present at the cathode facing air in the anode gas channel and is a function of residual oxygen concentration in the gas channels, that increases with storage time and reaches 21% (air) eventually. In this study, effects of residual oxygen concentration in a PEMFC on degradation of the PEMFC.

• Microbiology and Biotechnology Letters
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• v.21 no.4
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• pp.348-353
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• 1993

The optimal conditions for operating a moving-aeration bioreactor were determined as 30rpm and 150 (ml/min) of air flow rate, which can yield ca. 7.3 (l/h)of maximum mass transfer coefficient. It was also found that the agitation speed played much much important role than air input rate in oxgen transfer into the medium. $2.6{\times}10^6$ (cells/ml) and 0.6 (ml/l) of maximum cell denisty and IL-2 production were observed in batch cultivation of IL-2 producing BHK cell line. 0.53 (mM/l/h) of oxygen uptake rate was also estimated. The performance of a moving-aeration bioreactor (specific growth rate and oxygen uptake rate, etc.) was superior to other culture systems, such as cell-life and static membrane aeration bioreactors. Ii must be useful to apply this reactor to many culture processes by improving structural limitations in scaling-up the system.

• Toxicological Research
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• v.23 no.3
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• pp.215-221
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• 2007

Although sanguinarine, a benzophenanthridine alkaloid, possesses anti-cancer properties against several cancer cell lines, the molecular mechanisms by which it inhibits cell growth and induces apoptosis have not been clearly understood. In order to further explore the critical events leading to apoptosis in sanguinarine-treated MCF-7 human breast carcinoma cells, the following effects of sanguinarine on components of the mitochondrial apoptotic pathway were examined: generation of reactive oxygen species (ROS), alteration of the mitochondrial membrane potential (MMP), and the expression changes of Bcl-2 family proteins. We show that sanguinarine-induced apoptosis is accompanied by the generation of intracellular ROS and disruption of MMP as well as an increase in pro-apoptotic Bax expression and a decrease of anti-apoptotic Bcl-2 and Bcl-xL expression. The quenching of ROS generation with N-acetyl-L-cysteine, the ROS scavenger, protected the sanguinarine-elicited ROS generation, mitochondrial dysfunction, modulation of Bcl-2 family proteins, and apoptosis. Based on these results, we propose that the cellular ROS generation plays a pivotal role in the initiation of sanguinarine-triggered apoptotic death.

• Journal of Microbiology and Biotechnology
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• v.32 no.12
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• pp.1547-1552
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• 2022

β-Amyrin is a pentacyclic triterpene widely distributed in leaves and stems worldwide. The ability of β-amyrin to induce the production of reactive oxygen species (ROS) in microorganisms suggests its potential as an antimicrobial agent. Thus, this study aimed to elucidate the antibacterial mode of action of β-amyrin. We treated Escherichia coli cells with β-amyrin and found that it triggered ROS accumulation. Excessive stress caused by ROS, particularly hydroxyl radicals, induces glutathione (GSH) dysfunction. GSH protects cells from oxidative and osmotic stresses; thus, its dysfunction leads to membrane depolarization. The resultant change in membrane potential leads to the release of apoptotic proteins, such as caspases. The activated caspases-like protein promotes the cleavage of DNA into single strands, which is a hallmark of apoptosis-like death in bacteria. Apoptotic cells usually undergo events such as DNA fragmentation and phosphatidylserine exposure, differentiating them from necrotic cells, and the cells treated with β-amyrin in this study were positive for annexin V and negative for propidium iodide, indicating apoptosis-like death. In conclusion, our findings suggest that the antibacterial mode of action of β-amyrin involves the induction of ROS, which resulted in apoptosis-like death in E. coli.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.517-522
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• 2023

A chemical/mechanical durability test of polymer membrane evaluation method is used in which air and hydrogen are supplied to the proton exchange membrane fuel cell (PEMFC) and wet/dry is repeated in the open circuit voltage (OCV) state. In this protocol, when wet/dry is repeated, voltage increase/decrease is repeated, resulting in electrode degradation. When the membrane durability is excellent, the number of voltage changes increases and the evaluation is terminated due to electrode degradation, which may cause a problem that the original purpose of membrane durability evaluation cannot be performed. In this study, the same protocol as the department of energy (DOE) was used, but oxygen was used instead of air as the cathode gas, and the wet/dry time and flow rate were also increased to increase the chemical/mechanical degradation rate of the membrane, thereby shortening the durability evaluation time of the membrane to improve these problems. The durability test of the Nafion 211 membrane electrode assembly (MEA) was completed after 2,300 cycles by increasing the acceleration by 2.6 times using oxygen instead of air. This protocol also accelerated degradation of the membrane and accelerated degradation of the electrode catalyst, which also had the advantage of simultaneously evaluating the durability of the membrane and the electrode.

• Molecules and Cells
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• v.39 no.9
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• pp.680-686
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• 2016

Uncoupling proteins (UCPs) are mitochondrial inner membrane proteins that function to dissipate proton motive force and mitochondrial membrane potential. One UCP has been identified in Caenorhabditis elegans (C. elegans), namely UCP-4. In this study, we examined its expression and localization using a GFP marker in C. elegans. ucp-4 was expressed throughout the body from early embryo to aged adult and UCP-4 was localized in the mitochondria. It is known that increased mitochondrial membrane protential leads to a reactive oxygen species (ROS) increase, which is associated with age-related diseases, including neurodegenerative diseases in humans. A ucp-4 mutant showed increased mitochondrial membrane protential in association with increased neuronal defects during aging, and the neurons of ucp-4 overexpressing animals showed decreased neuronal defects during aging. These results suggest that UCP-4 may be involved in neuroprotection during aging via relieving mitochondrial membrane protential. We also investigated the relationship between UCP-4 and innate immunity because increased ROS can affect innate immunity. ucp-4 mutant displayed increased resistance to the pathogen Staphylococcus aureus compared to wild type. The enhanced immunity in the ucp-4 mutant could be related to increased mitochondrial membrane protential, presumably followed by increased ROS. In summary, UCP-4 might have an important role in neuronal aging and innate immune responses through mediating mitochondrial membrane protential.

• Membrane Journal
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• v.10 no.4
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• pp.192-197
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• 2000

Gas permeation and separation characteristics of ozone treated polysulfone (PSF) membranes were investigated. The PSF is one of the most widely used commercial membranes. Ozone treatment of the PSF membrane was performed for certain hours by continuously supplying 5 vol.% ozone-containing oxygen to the chamber, in which the membrane samples were charged. The permselectivity of PSF increased with ozone treatment time, and it was found that one and half hour was enough to ozone treatment. Increase in the selectivity of the membrane for He/$N_2$, HY$N_2$, O:J$N_2$, COJ$CH_4$ by ozone treatment was found to be due to decrease in the permeability of gases with larger molecular size such as $N_2$ and $CH_4$ The decrease in the permeability of gases with smaller molecular size was negligible. The increase in the selectivities of the PSF by ozone treatment would be due to decrease in the free volume of the polymer because of the oxygen complexes generated by the reaction between ozone and the polymer.

• Journal of Life Science
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• v.9 no.4
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• pp.473-480
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• 1999

This study was designed to investigate the effects of pine (Pinus densiflora Sieb et Zucc) needle extract (PNE) on membrane fluidity and oxidative stress in liver membranes of Sprague-Dawley (SD) rats as a study on investigation of anti-aging effect and determination of chemical structures of PNE through the animal experiments. Male SD rats were fed basic diets (control group) and experimental diets (0.5% and 1.0%-PNE group) for 6 weeks. Administrations of 0.5% and 1.0%-PNE resulted in a marked decreases (15∼25% and 23∼26%, respectively) in cholesterol accumulations of liver mitochondria and microsomes compared with control group. Membrane fluidities were significantly increased (15∼25%) in liver microsomes of 0.5% and 1.0%-PNE groups compared with control group. Formations of basal and induced oxygen radicals (BOR and IOR) in liver mitochondria were significantly inhibited (11∼12% and 10∼15%, respectively) by administrations of 0.5% and 1.0%-PNE compared with control group. Lipid peroxide (LPO) levels were remarkbly decreased about 20% in liver mitochondria and microsomes of 0.5% and 1.0%-PNE groups compared with control group. Oxidized protein levels calculated with carbonyl group were significantly decreased about 15% in liver mitochondria of 1.0%-PNE group compared with control group. These results suggest that PNE may play a effective role in a attenuating a oxidative stress and increasing a membrane fluidity.

• Membrane and Water Treatment
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• v.9 no.1
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• pp.17-21
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• 2018

A series of laboratory scale experiments were performed to investigate the feasibility of membrane separation technology for natural rubber (NR) wastewater treatment and reuse. Three types of spiral wound membranes were employed in the cross-flow experiments. The NR wastewater pretreated by sand filtration and cartridge filtration was forced to pass through the ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes successively. The UF retentate, which containing abundant proteins, can be used to produce fertilizer, while the NF retentate is rich in quebrachitol and can be used to extract quebrachitol. The permeate produced by the RO module was reused in the NR processing. Furthermore, about 0.1wt% quebrachitol was extracted from the NR wastewater. Besides, the effluent quality treated by the membrane processes was much better than that of the biological treatment. Especially for total dissolved solids (TDS) and total phosphorus (T-P), the removal efficiency improved 53.11% and 49.83% respectively. In addition, the removal efficiencies of biological oxygen demand (BOD) and chemical oxygen demand (COD) exceeded 99%. The total nitrogen (T-N) and ammonia nitrogen (NH4-N) had approximately similar removal efficiency (93%). It was also found that there was a significant decrease in the T-P concentration in the effluent, the T-P was reduced from 200 mg/L to 0.34 mg/L. Generally, it was considered to be a challenging problem to solve for the biological processes. In brief, highly resource utilization and zero discharge was obtained by membrane separation system in the NR wastewater treatment.

• Journal of Life Science
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• v.11 no.2
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• pp.103-110
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• 2001

This study was designed to investigate the effects of silkworm(Bombyx moril L.) powder on oxidative stress and membrane fluidity in brain membranes of rats. Sprague-Dawley(SD) male rats(160$\pm$10 g) were fed basic diet(control group), and experimental diets(SWP-200 and SWP-400 groups) added 200 and 400mg/kg BW/day for 6 weeks. There were no significant differences in cholesterol levels of brain memberanes by administration of silkworm powder (SWP). Membrane fluidities were significantly increased(21.5% and 30.8%, respectively) in brain mitochondria of SWP-200 and SWP-400 groups compared with control group, but significant difference between brain microsomes could not obtained. Basal oxygen radicals (BORs) in brain mitochondria and mircrosomes were significantly inhibited(8.5% and 16.5%, 16.8%and 24.8%, respectively) by SWP-200 and SEP-400 groups compared with control group. Induced oxygen radicals(IORs) in brain mitochondria were significantly inhibited(16.6% and 21.4%, respectively)by sWP-200 and SWP-400 groups compared with control group, but IOR in brain microsome were significantly inhibited about 16.0% by SWP-400 groups only compared with control group. Lipid peroxide(LPO) levels were significantly decreaed(14.8%and 22.4%, respectively) in brain mitochondria of SWP-200 and SWP-400 groups compared with control group, but LPO level was significantly decreased about 16.0% in brain microsome of SWP-400 group only. Oxidized protein(OP) levels were remarkably decreased(about 14.8% and 16.5%, respectively) in brain mitochondria of SWP-200 and SWP-400 groups, but OP level was significantly decreased about 13.0% in brain microsome of SWP-400 group only compared with control group, Theses results suggest that administration of in brain microsome of SWP-400 group only compared with control group. These results suggest that administration of SWP may play effective role in attenuating an oxidative stress and increasing a membrane fluidity in brain membranes.