• Animal cells and systems
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• 제1권4호
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• pp.583-587
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• 1997

Incubation of an NADPH-dependent succinic semialdehyde reductase from bovine brain with N-bromosuccinimide (NBS) resulted in a time-dependent loss of enzyme activity. The inactivation followed pseudo-first-order kinetics with the second-order rate constant of $6.8\times{10}^3$ $M^-1$ $min^{-1}$. The inactivation was prevented by preincubation of the enzyme with substrate succinic semialdehyde, but not with coenzyme NADPH. There was a linear relation-ship between oxindole formation and the loss of enzyme activity. Spectro-photometric studies indicated that about one oxindole group per molecule of the enzyme was formed following complete loss of enzymatic activity. It is suggested that the catalytic function of succinic semialdehyde reductase is modulated by binding of NBS to a specific tryptophan residue at or near the substrate binding site of the enzyme.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.423-428
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• 2009

The comparative study of three calix[4]heterocycles (calix[4]pyrrole, calix[4]furan, and calix[4]thiophene) has been theoretically performed by using high-level density functional theory (DFT) at the MPWB1K/6-311G$^{**}$//B3LYP/6- 311G$^{**}$ level. The effect of different hetero-atoms (nitrogen, oxygen, and sulfur) placed in the heterocycles on the conformational flexibility, thermodynamic stability order, cavity sizes, charge distributions, and binding propensities are examined. The thermodynamic stability differences between the conformers are found to be much greater in calix[4]pyrrole compared to those in calix[4]furan and calix[4]thiophene. Relatively larger NH group and higher dipole of a pyrrole ring in calix[4]pyrrole contribute to the higher energy barrier for the conformational conversions and relatively rigid potential energy surface compared to the case of calix[4]furan and calix[4]thiophene. The computational results herein provide theoretical understanding of the conformational flexibility and the thermodynamic nature which can be applied to understand the complexation behavior of the three calix[4]heterocycles.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2806-2808
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• 2010

The structure of 3-aminophenol $(CO_2)_1$ cluster was computationally studied both in the ground and the lowest singlet excited electronic states. The ground state structure and binding energy of the cluster was investigated using the second-order M$\ddoot{o}$ller-Plesset perturbation theory (MP2) at the complete basis set (CBS) limit. The excited state geometry of the cluster was obtained at the second-order approximate coupled cluster (CC2) level with cc-pVDZ basis set, and the $S_0-S_1$ absorption spectrum was simulated by calculating Franck-Condon overlap integral. The ground state geometry of the global minimum with a very high binding energy of 4.3 kcal/mol was found for the cluster, due to the interaction between amino group and $CO_2$ in addition to the strong $\pi-\pi$ interaction between the aromatic ring and $CO_2$. The excited state geometry shows a very big shift in the position of $CO_2$ compared to the ground state geometry, which results in low intensity and broad envelope in the Franck-Condon simulation.

• 한국환경보건학회지
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• 제1권1호
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• pp.21-27
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• 1974

This work was carried out to investigate the chemical properties of the chelate compounds which were produced with 2-methoxy-5-nitrophenol(MNG) and metal salt such as copper nitrate and manganese nitrate. And obtained results were as in the followings. 1) The binding ratio of the chelate compounds formation were determined by using the molar ratio concentration method and their chemical structures were identified by IR-spectrum. 2) In the absorbance measuring, 2-methoxy-5-nitrophenol coordinated with manganese and copper showed the maximum absorbance at $430 m\mu$ and $410 m\mu$ respectively. 3) The binding ratio of chelated compounds were measured by molar ratio method and continuous variation method with spectrophotometer, which was identified as 1:2. 4) The conditional formation constant(log Kn value) of manganese and copper chelate compounds were 6.70, 6.75, respectively according to the equation of $log\frac{A-AM\circ n MNG}{AMm MNG-A}=n log (M\circ)+log Kn$ 5) The dissociations degree of manganese and copper chelate compound were $2, 300{\times} 10^{-7}$, $2, 346{\times} 10^{-7}$ respectively according to the molar calculation method.

• Bulletin of the Korean Chemical Society
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• 제28권5호
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• pp.816-820
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• 2007

Novel new red-light emitting perylene fluoroionophore N,N'-dipropyl-1,7-bis(calix[4]azacrown-5-crown-5)- 3,4,9,10-perylene tetracarboxy diimide (3) was prepared by reacting N,N'-dipropyl-1,7-dibromo-3,4,9,10- perylene tetracarboxy diimide (1) with calix[4]azacrown-5-crown-5. Also the alternating copolymer (4) with similar repeating unit was prepared reacting by calix[4]bisazacrown-5 with 1. Metal ion binding by 3 and 4 leads to a blue-shift of absorption band and emission spectra. When ionophoric characteristics were investigated by binding alkali, alkali earth metal and various metal ions, polymeric ionophores displayed large fluorescence decreasing effects with K+, Ag+ and Ba2+, which was rationalized by photo-induced charge transfer (PCT).

• BMB Reports
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• 제41권11호
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• pp.808-813
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• 2008

Human microsomal prostaglandin E synthase-1 (mPGES-1) is a membrane associated protein that catalyzes the conversion of prostaglandin $H_2$ ($PGH_2$) into prostaglandin $E_2$ ($PGE_2$). In this study, the expression of human mPGES-1 in E. coli was significantly enhanced by modifying the utility of specific codons and the recombinant mPGES-1 was efficiently purified to homogeneity. The $K_m$ and $V_{max}$ of the purified enzyme were determined and the trimeric state characterized by chemical cross-linking with glutaraldehyde. The purified mPGES-1 was used for the screening of a chemical library of bioactive or drug compounds to identify novel inhibitors, and oxacillin and dyphylline were identified as moderately inhibiting mPGES-1 with $I_{C50}$ values of 100 and 200 ${\mu}M$, respectively. As these compounds competitively inhibited the catalysis of $PGH_2$, their binding sites appeared to be located near the $PGH_2$ binding pocket.

• Bulletin of the Korean Chemical Society
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• 제33권6호
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• pp.1998-2004
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• 2012

We carried out DFT calculations for monohydrated sulfuric and phosphoric acids. We are interested in clusters which differ in orientation of hydrogen atoms only. Such molecular complexes are close in energy, since they lie in the vicinity of the global minimum energy structure on the flat potential energy surface. For monohydrated sulfuric acid we identified four different isomers. The monohydrated phosphoric acid forms five different conformers. These systems are difficult to study from the theoretical point of view, since binding energy differences in several cases are very small. For each structure, we calculated harmonic vibrational frequencies to be sure that if the optimized structures are at the local or global minima on the potential energy surface. The analysis of calculated -OH vibrational frequencies is useful in interpretation of infrared photodissociation spectroscopy experiments. We employed four different DFT functionals in our calculations. For each structure, we calculated binding energies, thermodynamic properties, and harmonic vibrational frequencies. Our analysis clearly shows that DFT approach is suitable for studying monohydrated inorganic acids with different hydrogen atom orientations. We carried out MP2 calculations with aug-cc-pVDZ basis set for both monohydrated acids. MP2 results serve as a benchmark for DFT calculations.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4169-4172
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• 2012

To elucidate the roles of cysteine residues in rice Phi-class GST F3, in this study, all three cysteine residues were replaced with alanine by site-directed mutagenesis in order to obtain mutants C22A, C73A and C77A. Three mutant enzymes were expressed in Escherichia coli and purified to electrophoretic homogeneity by affinity chromatography on immobilized GSH. The substitutions of Cys73 and Cys77 residues in OsGSTF3 with alanine did not affect the glutathione conjugation activities, showing non-essentiality of these residues. On the other hand, the substitution of Cys22 residue with alanine resulted in approximately a 60% loss of specific activity toward ethacrynic acid. Moreover, the ${K_m}^{CDNB}$ value of the mutant C22A was approximately 2.2 fold larger than that of the wild type. From these results, the evolutionally conserved cysteine 22 residue seems to participate rather in the structural stability of the active site in OsGSTF3 by stabilizing the electrophilic substrates-binding site's conformation than in the substrate binding directly.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3644-3652
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• 2010

The metallo-$\beta$-lactamases ($M{\beta}Ls$) are clinically significant enzymes which readily hydrolyze most $\beta$-lactam antibiotics. Discovering potential inhibitors for the $M{\beta}Ls$ is an expensive, time consuming endeavor. Virtual screening can sieve out inhibitor candidates with incompatible features prior to synthesis, decreasing these costs. Using Autodock 4.0, the binding locations and energies of four previously-studied potential inhibitors and four additional compounds obtained from the National Cancer Institute (NCI) database were computationally calculated. Based on the docking models of these eight compounds, we then designed several hypothetical inhibitor structures, compounds A through F, and performed their respective docking experiments. The docking results for compound F showed that it binds to the zinc containing active sites with a lowest predicted binding energy of -6.70 kcal/mol, suggesting F is the most likely potential $M{\beta}L$ inhibitor.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2523-2531
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• 2009

Effects of some diacid, diamine and dinitro aromatic compounds on the structure and activity of adenosine deaminase (ADA) were investigated by UV-Vis spectrophotometry in 50 mM phosphate buffer at pH = 7.5 and 27 ${^{\circ}C}$ and molecular docking studies. The results showed that all tested ligands are showing inhibition; five ligands are uncompetitive and other two ligands are mixed of competitive and noncompetetive inhibitors with majority of competitive behavior. For the later case analysis was done based on competitive inhibition. Diacids have larger size and higher inhibition constant ($K_I$) relative to others. A logical correlation between calculated free energy of binding and experimental values was obtained for un-competitive. Experimental and calculated data showed that competitive inhibitors are distributed near the active site of enzyme and form several cluster of ranks, whereas uncompetitive inhibitors bind to the enzyme-substrate complex and distributed far from the active site. Results of structure-activity relationship showed that, larger, more hydrophobe, less spherical and more aromatic ligands have higher inhibition constants.