O-GlcNAcylation of amyloid-β precursor protein at threonine 576 residue regulates trafficking and processing

Chun, Y.S.,Kwon, O.H.,Chung, S. Academic Press 2017 Biochemical and biophysical research communication Vol. No.

The pathological hallmark of Alzheimer's disease (AD) is associated with the accumulation of amyloid-β (Aβ) derived from proteolytic processing of amyloid-β precursor protein (APP). APP undergoes post-translational modification including N- and O-glycosylation. O-GlcNAcylation is a novel type of O-glycosylation, mediated by O-GlcNAc transferase attaching O-β-N-acetylglucosamine (O-GlcNAc) to serine/threonine residues of the target proteins. O-GlcNAc is removed by O-GlcNAcase. We have previously reported that increasing O-GlcNAcylated APP using the O-GlcNAcase inhibitor, PUGNAc, increases its trafficking rate to the plasma membrane and decreases its endocytosis rate, resulting in decreased Aβ production. However, O-GlcNAc modification sites in APP are unknown. In this study, we mutated three predicted O-GlcNAc modification threonine residues of APP into alanines (T291A, T292A, and T576A) and expressed them in HeLa cells. These APP mutants showed reduced O-GlcNAcylation levels, indicating that these sites were endogenously O-GlcNAcylated. Thr 576 was the major O-GlcNAcylation site when cell was treated with PUGNAc. We also showed that the effects of PUGNAc on APP trafficking to the plasma membrane and Aβ production were prevented in the T576A mutant. These results implicate Thr 576 as the major O-GlcNAcylation site in APP and indicate that O-GlcNAcylation of this residue regulates its trafficking and processing. Thus, specific O-GlcNAcylation of APP at Thr 576 may be a novel and promising drug target for AD therapeutics.

Characteristics of FAM-Z01 compared to silica gels in the performance of an adsorption bed

Hong, S.W.,Ahn, S.H.,Chung, J.D.,Bae, K.J.,Cha, D.A.,Kwon, O.K. Pergamon 2016 Applied thermal engineering Vol. No.

This paper investigates the characteristics of ferroaluminophosphate (FAM-Z01) compared to various types of conventional silica gels in the performance of an adsorption bed. FAM-Z01 has high potential to replace silica gel due to some key advantages, including a low heating temperature and high adsorption rate resulting from its S-shaped isotherm. We conducted a performance simulation on a fin-tube type adsorption bed with FAM-Z01/water and silica gel/water working pairs and compared the results in terms of coefficient of performance (COP) and specific cooling power (SCP). In the partial pressure range of typical operating condition for silica gels, there was no advantage with FAM-Z01. However, in the partial pressure range of 0.14<P/P<SUB>0</SUB><0.29, which corresponds to a lower evaporation temperature (15<SUP>o</SUP>C→10<SUP>o</SUP>C) and lower heating temperature (80<SUP>o</SUP>C→70<SUP>o</SUP>C) compared to the typical operating condition for silica gels, the COP of FAM-Z01 was almost similar (3.72% decreased) to that of Type-RD silica gel, while the SCP was significantly increased by 35.0%. This indicates that without a change of system efficiency, FAM-Z01/water has a high cooling capacity with small size as compared to Type-RD silica gel/water. This confirms that the adsorbent FAM-Z01 has a high potential to address one of the adsorption chiller's disadvantages, i.e., system size.

Synergistic antibacterial effect of curcumin against methicillin-resistant Staphylococcus aureus

Mun, S.H.,Joung, D.K.,Kim, Y.S.,Kang, O.H.,Kim, S.B.,Seo, Y.S.,Kim, Y.C.,Lee, D.S.,Shin, D.W.,Kweon, K.T.,Kwon, D.Y. G. Fischer 2013 Phytomedicine Vol.20 No.8

<P>Methicillin-resistant Staphylococcus aureus (MRSA) are spread among infected patients, with infection rates increasing at an alarming rate. Furthermore, increased resistance to antibiotics has resulted in serious challenges in the treatment of infectious diseases worldwide. Under the selection pressure of exposure to antibiotics, microorganisms evolve to survive against the new conditions imposed by therapy. Therefore, there exists a need to develop alternative natural or combination drug therapies. Curcumin (CCM), a natural polyphenolic flavonoid isolated from the rhizome of a plant, Curcuma longa Linne., has been found to possess many beneficial biological activities. The aim of this study was to investigate the synergistic effect of curcumin and antibiotics as well as to determine the antibacterial activity of CCM against specific MRSA strains. The antibacterial activity of CCM was assessed by the broth microdilution method (by calculating the minimal inhibitory concentration [MIC]), checkerboard dilution test, and time-kill assay. Antimicrobial activity of CCM was observed against all tested strains. The MICs of CCM against 10 strains of S. aureus ranged from 125 to 250 mu g/ml. In the checkerboard test, CCM markedly reduced the MICs of the antibiotics oxacillin (OXI), ampicillin (AMP), ciprofloxacin (CIP), and norfloxacin (NOR) used against MRSA. The time-kill curves showed that a combined CCM and OXI treatment reduced the bacterial counts below the lowest detectable limit after 24 h. This study suggested that CCM reduced the MICs of several antibiotics tested, notably of OXI, AMP, CIP, and NOR, and that CCM in combination with antibiotics could lead to the development of new combination of antibiotics against MRSA infection. (C) 2013 Published by Elsevier GmbH.</P>

저장벽 양자우물구조와 비태칭 패브리 - 페로 공명기 구조에 의한 고성능 2×4 S-SEED Array 구현

권오균(O. K. Kwon),최영완(Y. W. Choi),김광준(K. J. Kim),이일항(E. H. Lee),이상훈(S. H. Lee),원용협(Y. H. Won),유형모(H. M. Yoo) 한국광학회 1994 한국광학회지 Vol.5 No.1

GaAs/Al_(0.04)Ga_(0.96)As 다중양자우물 구조를 이용한 반사형 PIN 다이오우드 S-SEED의 설계에 있어 낮은 동작전압, 높은 포화에너지 및 높은 반사율 on/off 강도비를 얻고자 저장벽 양자우물구조와 비대칭 페브리-페로 공명구조를 결합하였다. 2×4 array를 구성하는 S-SEED들은 역방향 동작전압 5V에서 평균적으로 13 이상의 반사율 on/off 강도비 (CR)와 약 24%의 반사율차 (ΔR) 및 91% 이상의 광쌍안정폭 (Δ)을 나타내었다. 공명구조를 이용함으로서 PIN 다이오우드 진성영역내의 양자우물의 주기수를 줄일 수 있어 외부동작전압 없이도 CR~4.7, R~9.2%, ~22%의 향상된 무전압 광쌍안정 동작특성을 얻었다. We designed and fabricated a 2×4 symmetric self electro-optic effect device array using GaAs/Al_(0.04)Ga_(0.96)As extremely shallow quantum wells grown by a molecular beam epitaxy. By employing ESQW and asymmetric Fabry-Perot cavity structure simultaneously, we improved the performances of S-SEED such as on/off contrast ratio (CR), reflectivity change (ΔR), and optical bistability loop width (Δ). The average values of the elements of the 2×4 S-SEED array were CR~13.1, R~24%, and Δ~91%. It was found that the AFP cavity structure enhances the self-biased optical bistability in ESQW-SEED under no external bias. That is due to the decreased intrisic region thickness in AFP-SEED structures, and which increases the built-in electric fields. The zero-biased S-SEED showed CR of ~4.7, R~9%, and Δ~22%.

왕겨에 의한 신령버섯균사체 액체배양액의 생쥐 항복수암성 증가

Young S. Kim(김영숙),Wook J. Jang(장욱진),Md. A. Rakib(라키브),Jung M. Kwon(권정민),Chae R. Ahn(안채린),So Y. Kim(김소영),Yong U. Cho(조용운),Young K. Ha(하영권),Jeong O. Kim(김정옥),Yeong L. Ha(하영래) 한국생명과학회 2010 생명과학회지 Vol.20 No.9

왕겨가 Agaricus blazei Murill (AB: 신령버섯)균사체 액체배양 추출물의 항암성을 증가시키는지에 관한 연구를 수행하였다. AB균사체를 대두박을 기본으로 한 액체배지에 다양한 조건으로 배양하여, β-glucan 함량, Brix, 균사체를 측정하여 적정 생육조건을 선정하고, 이들의 열수추출물의 S-180 cell로 유도한 mouse 복수암에 대한 항암성을 조사하였다. AB균사체는 25℃에서 5일간 배양하였을 때 최적 생육을 나타내었고, 이 배양물이 다른 조건에서 배양한 배양물보다 우수한 항암성을 나타내었다. AB균사체의 생육 및 항암성은 변온배양에 따른 효과는 없었다. 따라서 이 최적배양조건(25℃, 5일 배양)에서 AB균사체를 1% 왕겨분말이 함유된 액체배지에 배양하고, 이의 열수 추출물의 항암성을 검증하였다. 1% 왕겨가 함유된 액체배지에서 배양한 열수추출물의 항암성은 왕겨가 함유되지 않은 배지의 열수추출물보다 항암성이 유의성 있게 증가되었다(p<0.05). 왕겨의 첨가는 AB균사체의 생육을 오히려 촉진시켰다. 이 결과는 왕겨가 AB균사체 뿐 만 아니라 다른 버섯균사체 액체배양물의 항암성 증진을 위한 원료로 활용될 수 있을 것임을 의미한다. The effects of rice hull (RH) powder on the anticarcinogenic activity of submerged-liquid cultures of Agaricus blazei Murill (AB) were assessed for mouse ascites cancers induced by mouse Sarcoma S-180 (S-180) cancer cells. Optimal growth of AB mycelia in the basal liquid culture medium, containing soybean meal, was achieved by culturing at 25℃ for 5 days, when evaluated by β-glucan content, Brix, and mycelial weight, relative to other culture conditions. Hot-water extract (HWE) of the submergedliquid culture of AB mycelia grown at 25℃ for 5 days exhibited a stronger anticarcinogenic activity, relative to HWE from other culture conditions. No such effects were obtained from AB mycelial cultures by alternative temperature-controlling cultures. Both cytotoxicity for S-180 cells and anticarcinogenic potentials for mouse ascites cancer of the HWE from AB mycelia grown in the basal medium containing 1% RH powder for 5 days at 25℃ were significantly (p<0.05) enhanced, relative to HWE from the AB mycelia culture of the basal medium without RH powder. These results indicate that HWE of submerged-liquid culture of AB mycelia, incubated in media containing 1% RH powder at 25℃ for 5 days, enhanced anticarcinogenic activity against S-180 cell-induced mouse ascites cancer, and suggest that RH powder is an excellent ingredient for the improvement of the anticarcinogenic potentials of the submerged-liquid culture of mushroom mycelia.

Caspase-3 activation as a key factor for HBx-transformed cell death

Kim, A.,Kwon, O. S.,Kim, S. O.,He, L.,Bae, E. Y.,Lee, M. S.,Jeong, S. J.,Shim, J. H.,Yoon, D. Y.,Kim, C. H.,Moon, A.,Kim, K. E.,Ahn, J. S.,Kim, B. Y. Blackwell Publishing Ltd 2008 Cell proliferation Vol.41 No.5

<P>Abstract. </P><P><I>Objectives</I>: Nuclear factor-kappa B (NF-&kgr;B) activation has been associated with the tumorigenic growth of hepatitis B virus X protein (HBx)-transformed cells. This study was aimed to find a key target for treatment of HBx-mediated cancers. <I>Materials and methods</I>: NF-&kgr;B activation, endoplasmic reticulum-stress (ER-stress), caspase-3 activation, and cell proliferation were evaluated after Chang/HBx cells permanently expressing HBx viral protein were treated with inhibitors of NF-&kgr;B, proteasome and DNA topoisomerase. <I>Results</I>: Inhibition of NF-&kgr;B transcriptional activity by transient transfection with mutant plasmids encoding Akt1 and glycogen synthase kinase-3&bgr; (GSK-3&bgr;), or by treatment with chemical inhibitors, wortmannin and LY294002, showed little effect on the survival of Chang/HBx cells. Furthermore, I&kgr;Bα (S32/36A) mutant plasmid or other NF-&kgr;B inhibitors, 1-pyrrolidinecarbonidithioic acid and sulphasalazine, were also shown to have little effect on the cell proliferation. By contrast, proteasome inhibitor-1 (Pro1) and MG132 enhanced the HBx-induced ER-stress response and the subsequent activation of caspase-12, -9 and -3 and reduced cell proliferation. Camptothecin (CPT), however, triggered activation of caspase-3 without induction of caspase-12, and reduced cell proliferation. In addition, CPT-induced cell death was reversed by pre-treatment with z-DEVD, a caspase-3-specific inhibitor. <I>Conclusions</I>: Detailed exploitation of the regulators of caspase-3 activation could open the gate for finding an efficient target for development of anticancer therapeutics against HBx-transformed hepatocellular carcinoma.</P>

Excluded vertex-minors for graphs of linear rank-width at most k

Jeong, J.,Kwon, O.j.,Oum, S.i. Academic Press 2014 European journal of combinatorics : Journal europ& Vol.41 No.-

Linear rank-width is a graph width parameter, which is a variation of rank-width by restricting its tree to a caterpillar. As a corollary of known theorems, for each k, there is a finite obstruction set O<SUB>k</SUB> of graphs such that a graph G has linear rank-width at most k if and only if no vertex-minor of G is isomorphic to a graph in O<SUB>k</SUB>. However, no attempts have been made to bound the number of graphs in O<SUB>k</SUB> for k≥2. We show that for each k, there are at least 2<SUP>Ω(3^k)</SUP> pairwise locally non-equivalent graphs in O<SUB>k</SUB>, and therefore the number of graphs in O<SUB>k</SUB> is at least double exponential. To prove this theorem, it is necessary to characterize when two graphs in O<SUB>k</SUB> are locally equivalent. A graph is a block graph if all of its blocks are complete graphs. We prove that if two block graphs without simplicial vertices of degree at least 2 are locally equivalent, then they are isomorphic. This not only is useful for our theorem but also implies a theorem of Bouchet (1988) stating that if two trees are locally equivalent, then they are isomorphic.

CHF₃ / C₂F6 플라즈마에 의한 실리콘 표면 잔류막의 특성

권광호(K.-H. Kwon),박형호(H.-H. Park),이수민(S. M. Lee),강성준(S. J. Kang),권오준(O.-J. Kwon),김보우(B.W. Kim),성영권(Y.-K. Sung) 한국진공학회(ASCT) 1992 Applied Science and Convergence Technology Vol.1 No.1

실리콘을 CHF₃/C₂F_6 가스 플라즈마를 이용하여 식각하면 실리콘위에 탄소, 불소 및 산소로 이루어진 잔류막이 형성된다. 이 잔류막을 XPS로 분석한 결과 탄소는 C-Si, C-Si, C-C/H, C-CF_x(x≤3), C-F, C-F₂, C-F₃ 결합을 하고 있으며, 불소는 F-Si, F-C 및 F-O 결합으로 이루어져 있음을 알았다. 한편 산소는 O-Si 및 O-F 결합으로, 실리콘은 Si-Si, Si-C 및 Si-O 결합상태를 나타낸다. 잔류막의 수직분포 연구를 통하여 Si-O 및 Si-C 결합이 탄소와 불소의 결합층 아래에 존재하고, 잔류막의 표면부에 F-O 결합이 분포함을 알았다. 또한 건식식각 변수가 잔류막 형성에 미치는 영향이 조사되었으며 CHF₃/C₂F_6 가스 유량비, RF power 벚 압력 등이 잔류막의 두께, 조성비 및 잔류막의 결합상태에 영향을 미침을 알 수 있었다. Si surfaces exposed to CHF₃/C₂F_6 gas plasmas in reactive ion etching (RIE) have been characterized by X-ray photoelectron spectroscopy (XPS). CHF₃/C₂F_6 gas plasma exposure of Si surface leads to the deposition of residual film containing carbon and fluorine. The narrow scan spectra of C 1s show various bonding states of carbon as C-Si, C-Si, C-C/H, C-CF_x(x≤3), C-F, C-F₂, and C-F₃. The chemical bonding states of fluorine are described with F-Si, F-C, and F-O. And the oxygen and silicon are also detected. The effects of parameters for reactive ion etching as CHF₃/C₂F_6 gas ratio, RF power, and pressure are investigated.

Combustion properties of gaseous CH₄/O₂ coaxial jet flames in a single-element combustor

Kim, T.Y.,Choi, S.,Kim, H.K.,Jeung, I.S.,Koo, J.,Kwon, O.C. Butterworths [etc.] ; Elsevier Science Ltd 2016 Fuel Vol.184 No.-

Fundamental combustion properties of gaseous methane (CH<SUB>4</SUB>)/oxygen (O<SUB>2</SUB>) coaxial jet flames in a single-element combustor are experimentally evaluated as a preliminary step for subsequent studies of injection at very low temperature or using liquid O<SUB>2</SUB> for CH<SUB>4</SUB>/O<SUB>2</SUB> bipropellants, recently appearing to be the oncoming liquid bipropellant. A combustion chamber with quartz windows, a single shear coaxial injector and an exhaust nozzle on the downstream of the chamber is considered for the present study. Focusing on the measurements of the ignition and combustion stability limits of the coaxial jet flames in the chamber, flame visualization is also conducted by OH<SUP>*</SUP> chemiluminescence, schlieren imaging and direct imaging. Results show the ignition limits restricted than the combustion stability limits. Flame behaviors are largely classified into two, the stably attached flame and the oscillating, liftoff (near-blowout) flame. Due to cooling effects on the wall of the chamber, stably liftoff flame is not observed. The stability of the flame is greatest at fuel-rich condition (based on the injected amounts of CH<SUB>4</SUB> and O<SUB>2</SUB>). From the flame visualization flame thickness is found to be smaller than the injector lip thickness and insensitive to injection conditions. The laminar-flow behavior near the injector exit due to the strong burning of pure O<SUB>2</SUB> is observed even for high Reynolds numbers (Re). The flame visualization also exhibits the recirculating O<SUB>2</SUB> that enhances burning in the combustor through the reaction with the outer fuel jet. The results of ignition limits, combustion stability limits and flame visualization can be used as a database for researches of modeling the gaseous CH<SUB>4</SUB>/O<SUB>2</SUB> jet flames in the combustion chamber.

장기 저장연료의 열안정성 및 연료접촉 고무오링의 수명예측 연구

정근우(K. W. Chung),홍진숙(J. S. Hong),김영운(Y. W. Kim),한정식(J. S. Han),정병훈(B. H. Jeong),권태수(T. S. Kwon),서동욱(D. O. Suh),성민준(M. J. Sung),권영일(Y. I. Kwon) 한국트라이볼로지학회 2018 한국윤활학회지(윤활학회지) Vol.34 No.5

Thermal deterioration of fuel due to long-term storage influences engine performance and causes malfunctions. Fuel stability is usually evaluated via heat resistance and thermal stability during a brief heat shock at high temperature; storage stability in this scenario means that there is very little change in the quality of the fuel during long-term storage. In addition, rubber-based products such as oil seals, O-rings, and rubber hoses can influence the quality of the fuel. When these rubber products are in contact with fuel, they can swell, mechanically weaken, and occasionally crack, thus leaking low molar weight rubber and additives including plasticizer and antioxidant into the fuel to degrade its properties and shorten its useful lifetime. This study determines the thermal stabilities of three kinds of synthetic fuels by evaluating their low temperature kinematic viscosities, chemical composition changes via GC analyses, gross heat of combustion, and color changes. We evaluate the compression set of O-rings by immersing one NBR and two FKM rubber O-rings in the three synthetic fuel samples in airtight containers at variable storage temperatures for six months; from this, we estimate the lifetimes of the O-rings using the Power law model. There were very little changes in the chemical compositions and gross heat of combustion after six months of the experiment. The lifetimes are thus dependent on the materials of the rubber products, and in particular, the FKM O-ring was calculated to have a theoretical lifetime of 200 to 5,700 years. These results indicate that the synthetic fuels maintain their physical properties even after long-term storage at high temperatures, and the FKM O-ring is suitable for long-term sealing of these fuels.