http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
The pH Studies of Recombinant Acetohydroxy Acid Synthase from Tobacco
윤문영,최정도,김복환 대한화학회 2003 Bulletin of the Korean Chemical Society Vol.24 No.5
Acetohydroxy acid synthase (AHAS) is one of several enzymes that require thiamine diphosphate and a divalent cation as essential cofactors. The active site contains several conserved ionizable groups and all of these appear to be important as judged by the fact that mutation diminishes or abolishes catalytic activity. Recently, we have shown [Yoon, M.-Y., Hwang, J.-H., Choi, M.-K., Baek, D.-K., Kim, J., Kim, Y.-T., Choi, J.-D. FEBS Letters 555 (2003), 185-191] that the activity is pH-dependent due to changes in Vmax and V/$K_m$. Data were consistent with a mechanism in which substrate was selectively catalyzed by the enzyme with an unprotonated base having a pK 6.48, and a protonated group having a pK of 8.25 for catalysis. Here, we have in detail studied the pH dependence of the kinetic parameters of the cofactors (ThDP, FAD, Mg2+) in order to obtain information about the chemical mechanism in the active site. The Vmax of kinetic parameters for all cofactors was pH-dependent on the basic side. The pK of ThDP, FAD and Mg2+ was 9.5, 9.3 and 10.1, respectively. The V/$K_m$ of kinetic parameters for all cofactors was pH-dependent on the acidic and on the basic side. The pK of ThDP, FAD and Mg2+ was 6.2-6.4 on the acidic side and 9.0-9.1 on the basic side. The well-conserved histidine mutant (H392) did not affect the pH-dependence of the kinetic parameters. The data are discussed in terms of the acid-base chemical mechanism.
The prediction of dynamic fatigue life of multi-axial loaded system
윤문영,김경호,오재응,이성범,부광석,김흥섭 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.1
The purpose of this paper is to compare with estimation of equivalent fatigue load in time domain and frequency domain and estimatethe fatigue life of structure with multi-axial vibration loading. The fatigue analysis with two methods is implemented with various signalslike random, sinusoidal signals. Also, an equivalent fatigue life estimated by rainflow cycle counting in time domain is compared withresults estimated with probability density function of each signal in frequency domain. In case of frequency domain, equivalent fatiguelife can be estimated through Dirlik’s method with probability density function. The work proposed in this paper compared the fatiguedamage accumulated under uni-axial loading to that induced by multi-axial loading. The comparison was performed for a simple cantileverbeam exposed to vibrations of several directions. For verification of estimation performance of fatigue life, results are compared tothose of FEM analysis (ANSYS).
Kinetic Studies of Aspartase from Hafnia alvei byTemperature Dependence Activity Changes
윤문영,Yun, Mun Yeong Korean Chemical Society 2000 Bulletin of the Korean Chemical Society Vol.21 No.4
The temperature dependence of the kinetic parameters of the aspartase-catalyzed reaction has been examined in the direction of deamination. The pK1values at 37$^{\circ}C$, 25$^{\circ}C$, 16$^{\circ}C$ and 7$^{\circ}C$ were 6.2 $\pm$ 0.1, 6.3 $\pm$ 0.1, $6.7{\pm}0.3$ and 6.9 $\pm$ 0.3, respectively. On the other hand, the pK2 values at 37$^{\circ}C$,25$^{\circ}C$, 16$^{\circ}C$ and 7$^{\circ}C$ were 8.1 $\pm0.2$, 8.3 $\pm$ 0.2, 8.2 $\pm$ 0.3 and 8.0 $\pm$ 0.2,respectively. The enthalpy of ionization, DHion, calculated from the slope of pK1, are 6.0 $\pm$ 0.3 kcal/mol. These results validate the prediction that aspartase requires a histidine residue for a general base, and a cysteine (or having a carboxyl functional group) for a general acid.
Effect of SiO2-ionized Loess on the Treatment of Tinea Pedis
윤문영,박정극 한국생물공학회 2009 Biotechnology and Bioprocess Engineering Vol.14 No.4
SiO2-ionized loess was prepared from the reaction of loess and sodium hydroxide at 1,400°C. The antifungal activity of SiO2-ionized loess against Trichophyton tonsurans, causing tinea, was examined by comparing against that of untreated loess. Soap containing SiO2-ionized loess was used for clinical efficacy tests in the evaluation of the treatment of tinea pedis. The mineral components in loess were maintained after the reaction and the content of ignite loss was decreased to 0.64%, compared to loess. The antifungal ratio reached 56.8% on medium containing 2.0% SiO2-ionized loess and 81.1% on medium containing greater than 3.0% SiO2-ionized loess. However, medium containing untreated loess had no antifungal activity. A clinical efficacy test revealed that soap containing the SiO2-ionized loess led to a significant improvement in symptoms, with the efficacy increasing as the duration of treatment increased.
Cloning and Characterization of UDP-glucose Dehydrogenase from Sphingomonas chungbukensis DJ77
윤문영,박혜연,박해철,박성하,김성건,김영창,신말식,최정도 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.7
Sphingomonas chungbukensis DJ77 has the ability to produce large quantities of an extracellular polysaccharide that can be used as a gelling agent in the food and pharmaceutical industries. We identified, cloned and expressed the UDP-glucose dehydrogenase gene of S. chungbukensis DJ77, and characterized the resulting protein. The purified UDP-glucose dehydrogenase (UGDH), which catalyzes the reversible conversion of UDP-glucose to UDPglucuronic acid, formed a homodimer and the mass of the monomer was estimated to be 46 kDa. Kinetic analysis at the optimal pH of 8.5 indicated that the Km and Vmax for UDP-glucose were 0.18 mM and 1.59 mM/min/mg,respectively. Inhibition assays showed that UDP-glucuronic acid strongly inhibits UGDH. Site-directed mutagenesis was performed on Gly9, Gly12 Thr127, Cys264, and Lys267. Substitutions of Cys264 with Ala and of Lys267 with Asp resulted in complete loss of enzymatic activity, suggesting that Cys264 and Lys267 are essential for the catalytic activity of UGDH.
윤문영 漢陽大學校 自然科學硏究所 2000 自然科學論文集 Vol.19 No.-
아세토니트릴 용매 내에서 p-니트로염화벤조일과 o-클로로아닐린과의 반응을 온도 (15, 20, 25℃)와 압력변화(1, 200, 500, 1000bar)에 따라 반응속도론적으로 연구하였다. 반응속도상수로부터 활성화파라미터 (ΔV≠, Δβ≠, ΔH≠, ΔS≠, ΔG≠, Ea)를 구하였다. 온도가 증가함에 따라 속도상수는 증가하고, 이때 ΔV≠, Δβ≠및 ΔS≠는 모두 음의값을 나타내었으며, 압력변화에 따른 속도론적 연구는 전반적인 반응을 associative SN2반응으로 진행됨을 알 수 있다. Aspartase from Hafnia alvei was inactivated by N-bromosuccinimide(NBS) following pseudo-first order kinetics. The apparent reaction orders were 2.9 ×10-3min-1㎛-1, indicating that inactivation was due to a indole group in the active site of aspartase and participation of the indole group in the essential step in the catalytic reaction. Spectrophoto-metric studies indicated that about one oxyindole group per molecule of enzyme was formed following complete loss of enzymatic activity.