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신경 세포에서 Ca-channel의 비활성에 관한 연구
이영식,조기승 漢陽大學校 基礎科學硏究所 1988 基礎科學論文集 Vol.7 No.-
신경세포의 bursting 기작을 설명하기 위하여 기존에 제안된 Ca-activated Potassium channel 대신 Ca channel을 사용하여 기존의 model과 유사한 결과를 얻었다. 이들의 Phase Plane에서의 행동도 유사함을 보여준다. We have modified slow oscillation dynamics in Plant Nerve cell model in order to incorperated the Ca chnnael incativation mechanism. The calcium activated potassium channel has been replcaed with leak and voltage dependent calcium channel with and calcium inactivated voltage gated calcium channel. The simulation results with our model resemble the experimental results and Plant model's. The phase plane behavior of our model is also similar to the Plant model's behavior. It suggest that the calcium channel inactivation mechainsm may be a possible mehcanism for the slow oscillation dynamics in membrane potential oscillation in neuron cell body.
담체의 표면거칠기와 전단응력이 미생물 부착에 미치는 영향
박영식,송승구,이채남,최윤찬 부산대학교 환경문제연구소 1995 環境硏究報 Vol.13 No.-
The propose of this paper was to examine the effect of surface roughness and shear stress of support medium on the development of biofilm in a rotating biological contactor. The surface roughness of PMMA as a support media was adjusted to 0.4, 0.8, 1.2, and 3㎛, respectively. Shear stress was varied with speed of rotating biological contactor. At low shear stress, bacterial attachment was not varied greatly with surface roughness. But at increased shear stress, bacterial attachment was changed sharply with surface roughness.
마이크로파 여기 플라즈마광 생성을 위한 도파관 시스템 설계에 관한 연구
전상재,전후동,송창현,하석영,이승혁,이태호,박의준 금오공과대학교 2005 論文集 Vol.26 No.-
In this paper, the plasma lighting system(PLS) excited by the commercial high power magnetron is developed. The design concepts are based on maximizing the huninous efficacy in conjunction with the miniaturization of waveguide system Furthermore the fine tuning is simplified by using only one stub, and the impedance matching is maximized by introducing the tapering technique. The experimental results show that the luminous efficacy can be dramatically improved by the proposed design method.
Suppression of Egr-1 transcription through targeting of the serum response factor by oncogenic H-Ras
Shin, Soon Young,Bahk, Young Yil,Ko, Jesang,Chung, Il-Yup,Lee, Young Seek,Downward, Julian,Eibel, Hermann,Sharma, Prem M,Olefsky, Jerrold M,Kim, Young-Ho,Lee, Bonghee,Lee, Young Han Wiley (John WileySons) 2006 The EMBO journal Vol.25 No.5
<P>The transcription factor Egr-1 functions as a key regulator in cellular growth, differentiation, and apoptosis. The loss of Egr-1 expression is closely associated with tumor development, although the molecular mechanism behind the suppression of Egr-1 is largely unknown. In this report, we show that growth factor-induced transcriptional activation of Egr-1 gene is downregulated by chronic expression of oncogenic H-Ras in NIH3T3 fibroblasts. Our results demonstrate that phosphoinositide 3-kinase (PI3K) signaling is necessary for oncogenic H-Ras-mediated reduction of Egr-1 gene expression. Aberrant activation of PI3K signaling by oncogenic Ras decreased the level of serum response factor (SRF) protein through the acceleration of proteolysis, which resulted in decreased SRF binding to the serum response element (SRE) sites within the Egr-1 promoter, leading to the suppression of Egr-1 transcription. Inhibition of PI3K signaling restored the downregulation of SRF and Egr-1 expression caused by oncogenic Ras. Our findings suggest a novel signaling mechanism by which prolonged activation of oncogenic H-Ras can trigger the loss of tumor suppressor Egr-1 through the PI3K pathway in NIH3T3 fibroblast model cell lines.</P>
Lee, Sang Min,Rhee, Sue Goo,Lee, Young Seek,Cho, Key Seung,Lee, Kang Suk,Son, Hyeog Gin 생화학분자생물학회 1982 BMB Reports Vol.29 No.6
A membrane-bound phosphatidylinositol 4-kinase (PI 4-kinase) was separated in a sucrose gradient and solubilized with 1% Triton X-100 from mouse brain. The enzyme was purified 2,952-fold by various chromatographic techniques including DEAF-cellulose, PI-Sepharose and Sephacryl S-200 gel filtration. The molecular weight of PI 4-kinase was approximately 76 kDa by gel filtration and 70.8 kDa by SDS-polyacrylamide gel electrophoresis. The purified enzyme exhibited specific activity of 112 nmol/min/㎎ protein and pI value of 4.7. Kinetic analysis of the PI 4-kinase indicated apparent K_m values of 190 μM and 120 μM for phosphatidylinositol and ATP, respectively. The maximal activity of this purified enzyme was observed at pH 7.4 at an incubation temperature of 37℃. The enzyme activity was significantly activated by Mg^(2+), Mn^(2+) and Fe^(2+), and inhibited severely by Ca^(2+). PI 4-kinase was proved to be pure in its immunoblot test by polyclonal antibody prepared from immunized rabbit sera. By this test, we were able to detect the existence of the same type of PI 4-kinase from other mouse organ tissues, such as liver, heart, kidney and spleen. Furthermore, similar immunoblot analysis with the same antisera recognized the different epitopes of PI 4-kinase proteins from various organs of rabbit, Chinese hamster and rat.
Purification and Characterization of Mouse Liver Rhodanese
Lee, Young Seek,Cho, Key Seung,Lee, Chul Young,Hwang, Jae Hoon 생화학분자생물학회 1977 BMB Reports Vol.28 No.2
Rhodanese from mouse liver was purified to near homogeneity by ammonium sulfate precipitation, CM-Sephadex ion exchange, hydroxyapatite and Sephacryl S-200-HR gel filtration chromatographies with a purification of 776 folds. The molecular weight was determined by Sephadex G-150 gel filtration and found to be 34.8 KDa. SDS-PAGE showed molecular weight 34 KDa and two identical subunits splitting by aging for 3 weeks at -70℃ the molecular weight of which was 17 KDa. The optimal pH of enzyme activity was 9.4 and the pI value of the enzyme was 6.6. Rhodanese showed the optimal reaction temperature of 25℃ and near linear increasing pattern until 10 min. incubation. KM values of rhodanese for KCN and Na₂S₂O₃ as substrates were 12.5 mM and 8.3 mM, respectively. Rhodanese activity was inhibited by more than 70% at a concentration of 100 μM of Ni^(2+), Zn^(2+), Cd^(2+), Hg^(2+) and Cu^(2+). Other metal ions, such as Mn^(2+), Mg^(2+), Ca^(2+), and Fe^(2+) showed no effect on rhodanese activity.
Lee, Young Seek,Chung, Il Yup,Chung, Jae Min 생화학분자생물학회 1989 BMB Reports Vol.35 No.2
Methianine aminopeptidase (MetAP) catalyzes the removal of an amino-terminal methionine from a newly synthesized polypeptide. The enzyme was purified to homogeneity from Bacillus stearothermophilus (KCTC 1752) by a procedure that involves heat precipitation and four sequential chromatographs (including DEAE-Sepharose ion exchange, hydroxylapatite, Ultrogel AcA 54 gel filtration, and Reactive red 120 dye affinity chromatography). The apparent molecular masses of the enzyme were 81,300 Da and 41,000 Da, as determined by gel filtration chromatography and sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE), respectively This indicates that the enzyme is comprised of two identical subunits. The MetAP specifically hydrolyzed the N-terminal residue of Met-Ala-Ser that was used as a substrate, and exhibited a strong preference for Met-Ala-Ser over Leu-Gly-Gly, Leu-Ser-Phe, and Leu-Leu-Tyr. The enzyme has an optimal pH at 8.0, an optimal temperature at 80℃, and pI at 4.1. The enzyme was heat-stable, as its activity remained unaltered when incubated at 80℃ for 45 min. The Km and Vmax values of the enzyme were 3.0 mM and 1.7 mmol/min/㎎, respectively. The B. stearothermophilus MetAP was completely inactivated by EDTA and required Co^(2+) ion(s) for activation, suggesting the metal dependence of this enzyme.