• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1279-1284
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• 2014

The binding of TATA-binding protein (TBP) to the TATA-box containing promoter region is aided by many other transcriptional factors including TFIIA and TFIIB. The mechanistic insight into the assembly of RNA polymerase II preinitation complex (PIC) has been gained by either directly altering a function of target protein or perturbing molecular interactions using drugs, RNAi, or aptamers. Aptamers have been found particularly useful for studying a role of a subset of PIC on transcription for their ability to inhibit specific molecular interactions. One major hurdle to the wide use of aptamers as specific inhibitors arises from the difficulty with traditional assays to validate and determine specificity, affinity, and binding epitopes for aptamers against targets. Here, using a technique called the bio-layer interferometry (BLI) designed for a label-free, real-time, and multiplexed detection of molecular interactions, we studied the assembly of a subset of PIC, TBP binding to TATA DNA, and two distinct classes of aptamers against TPB in regard to their ability to inhibit TBP binding to TFIIA or TATA DNA. Using BLI, we measured not only equilibrium binding constants ($K_D$), which were overall in close agreement with those obtained by electrophoretic mobility shift assay, but also kinetic constants of binding ($k_{on}$ and $k_{off}$), differentiating aptamers of comparable KDs by their difference in binding kinetics. The assay developed in this study can readily be adopted for high throughput validation of candidate aptamers for specificity, affinity, and epitopes, providing both equilibrium and kinetic information for aptamer interaction with targets.

• The Korean Journal of Applied Statistics
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• 제18권3호
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• pp.503-519
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• 2005

Cointegration test is usually performed under the assumption that the cointegrating vector is constant for the whole sample period. Most previous studies have used conventional cointegration methods in testing for a stable long-run equilibrium relation among related variables. However they have overlooked that the long-run equilibrium may not the unique and the stable relation may not be guaranteed. This study develops the additional statistical tests for the stability of the estimated cointegrating vector. Three tests for the parameter stability of a cointegrated regression model are utilized and applied to identify the types of variations in the long-run relation between the domestic unemployment and the rotated macroeconomic variables of interest. The present paper finds that, there exists a stable but, time-varying long-run relation between those. The observed variation in cointegrating relations is generally characterized by a discrete one-time shift, rather than a gradually evolving random walk process which is attributable to the IMF financial and economic crisis.

• Applied Chemistry for Engineering
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• 제28권3호
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• pp.339-344
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• 2017

Reaction characteristics and catalytic activities on reverse water gas shift (RWGS) reaction over $Pt/TiO_2$ catalyst and Pt based catalysts added promoters were investigated. It was confirmed that RWGS reaction activity was affected by the kind of supports and active metals and the $Pt/TiO_2$ catalyst showed the highest catalytic activity. From various inlet $CO_2$ concentration tests and also the evaluation of thermodynamic equilibrium conversion, the catalytic activity of $Pt/TiO_2$ catalyst could be evaluated objectively and it was found to be higher than that of commercial catalysts. The catalytic activity could increase by adding Ca and Na as promoters. The XPS analysis revealed that the catalytic activity is closely correlated with the electron density of surface active sites.

• Applied Chemistry for Engineering
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• 제20권2호
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• pp.186-190
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• 2009

This study is purposed to analyze thermodynamic properties on the hydrogen production by dimethyl ether steam reforming. Various reaction conditions of temperatures (300~1500 K), feed compositions (steam/carbon = 1~7), and pressures (1, 5, 10 atm) were applied to investigate the effects of the reaction conditions on the thermodynamic properties of dimethyl ether steam reforming. An endothermic steam reforming competed with an exothermic water gas shift reaction and an exothermic methanation within the applied reaction condition. Hydrogen production was initiated at the temperature of 400 K and the production rate was promoted at temperatures exceeding 550 K. An increase of steam to carbon ratio (S/C) in feed mixture over 1.5 resulted in the increase of the water gas shift reaction, which lowered the formation of carbon monoxide. The maximum hydrogen yield with minimizing loss of thermodynamic conversion efficiency was achieved at the reaction conditions of a temperature of 900 K and a steam to carbon ratio of 3.0.

• Journal of the Korean Chemical Society
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• 제25권1호
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• pp.1-6
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• 1981

Ultraviolet spectrophotometric investigations were carried out on the systems of o-, m-and p-xylene with iodine in carbon tetrachloride. The results reveal the formation of one to one molecular complexes of the type, $C_6H_4(CH_3)_2{\cdot}I_2. $The equilibrium constants of complexes were obtained in consideration of that absorption maxima has the blue shift with the increasing temperatures according to the formation of the charge transfer complexes. The thermodynamic parameters, $ {\Delta}$H, $ {\Delta}$G and $ {\Delta}$S for the formation of the charge transfer complexes were calculated from these values. These results combined with previous study of this series indicated that the relative stabilities of the polymethylbenzene complexes with iodine increase in the order, Benzene < Toluene < o-Xylene < p-Xylene These results are supposed to be the influence resulted from increase of electron density by the positive inductive effect and the steric hindrance effect.

• Journal of the Korean Chemical Society
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• 제29권6호
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• pp.575-581
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• 1985

Ultraviolet spectrophotometric investigations have been carried out on the systems of benzene, naphthalene and phenanthrene with iodine in carbon tetrachloride. The results reveal the formation of the one to one molecular complexes. The equilibrium constants were obtained in consideration of that absorption maxima due to the formation of the charge transfer complexes shift to blue with increasing temperature. Thermodynamic parameters for the formation of the charge transfer complexes were calculated from these values. These results indicate that the stabilities of the complexes formed between polynuclear aromatics and iodine increase with the number of aromatic rings. This may be a measure of the relative basicities of polynuclear aromatics toward iodine, which is explained in terms of the resonance of the interaction between aromatics and iodine. The results in this study were, additionally, compared with those of the polymethylbenzene series to be discussed the reason for them.

• Journal of the Korean Chemical Society
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• 제35권4호
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• pp.335-342
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• 1991

The effect of pressure and temperature on the stabilities of the charge transfer complexes of 1,3,5-trinitrobenzene, tetrachloro-p-benzoquinone and tetracyanoethylene with hexamethylbenzene in carbon tetrachloride has been investigated by spectrophotometric measurements. The equilibrium constants for the formation of the complexes were obtained at various temperature and pressure, and thermodynamic parameters for the formation of the charge transfer complexes are calculated from these values. The relative stabilities of charge transfer complexes with hexamethylbenzene increase in the order; 1,3,5-trinitrobenzene < tetrachloro-p-benzoquinone < tetracyanoethylene. This may be regarded as an order of relative acidity of these compounds in complexation with hexamethylbenzene and is explained in terms of the negative inductive effect of the ${\pi}$ acceptors. The red-shift at higher pressure, the blue-shift at higher temperature and the relation between pressure and oscillator strength are discussed on the basis of thermodynamic functions.

• Microbiology and Biotechnology Letters
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• 제37권4호
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• pp.365-370
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• 2009

For the production of diglyceride (DG) containing medium chain fatty acid, which could be utilized as a substrate to structured lipid production, monoglyceride (MG) and caprylic acid were reacted in the presence of lipase. The reaction system was well mixed homogeneously without using any organic solvent. Among the lipases investigated, Lipozyme RM IM and Novozym 435 were selected on the basis of equilibrium DG yields from the medium chain fatty acid and MG. And reaction conditions such as addition of molecular sieve, water content of immobilized lipase, reaction temperature, and mole ratio of MG/caprylic acid are optimized to increase DG production by using Lipozyme RM IM. DG content of reaction mixture showed 8% increase by adding molecular sieve to reaction mixture. Removal of water from the immobilized lipase could affect seriously equilibrium content of DG. More than 2.8%(w/w) removal of water from the support could make 44% of DG. Optimum temperature was found to $60^{\circ}C$. Temperature shift from $60^{\circ}C$ to $25^{\circ}C$ resulted in increase of free fatty acid (FFA) content. The equilibrium DG yield was not seriously affected by on MG/caprylic acid molar ratio. However, at the stoichiometric ratio of 1:1 the highest DG yield was obtained. Increasing MG/caprylic acid ratio from 0.3 to 1.8 decreased FFA content from 34% to 13%, while MG content increased from 27% to 50%.

• Journal of the Korean Chemical Society
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• 제54권5호
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• pp.500-505
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• 2010

Two different dyes containing the same molecular weight but different chemical structure have been utilized for the study of thermodynamic parameters. In this study, {3-(4-(diethylamino)phenyl)-3-(1-ethyl-2-methyl-1H-indol-3-yl)isobenzofuran-1(3H)-one} (Blue 502) and {3-(4-(diethylamino)-2-methylphenyl)-3-(1,2-dimethyl-1H-indol-3-yl)isobenzofuran-1(3H)-one} (Blue 402) were used. It has been performed by measuring UV spectra of the two dyes. In general, the blue shift has been observed from both dyes in higher carbon number alcohol solvents. Interestingly, Blue 502 showed higher stability than Blue 402 in the same conditions used in this study. And, the equilibrium constants (0.9~1.0) of the dyes depending upon temperature change were also calculated using UV absorbance. The standard enthalpy calculated from equilibrium constants and molar absorptivity($\varepsilon$) are 10.94 kJ/mol in Blue 402 and 9.010 kJ/mol in Blue 502, respectively.

• BMB Reports
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• 제32권6호
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• pp.521-528
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• 1999

The folding of recombinant hepatitis B virus X-protein (rHBx) solubilized from Escherichia coli inclusion bodies was investigated. By sequential dialysis of urea, rHBx was folded into its native structure, which was demonstrated by the efficacy of its transcriptional activation of the adenovirus major late promoter (MLP), fluorescence spectroscopy, and circular dichroism (CD) analysis. The decrease in CD values at 220 nm and a corresponding blue shift of the intrinsic fluorescence emission confirmed the ability of rHBx to refold in lower concentrations of urea, yielding the active protein. Equilibrium and kinetic studies of the refolding of rHBx were carried out by tryptophan fluorescence measurements. From the biphasic nature of the fluorescence curves, the existence of stable intermediate states in the renaturation process was inferred. Reverse phase-high performance liquid chromatography (RP-HPLC) analysis further demonstrated the existence of these intermediates and their apparent compactness.