• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.66-70
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• 1998

Several liquid crystalline monomers were synthesized and characterized to utilize as new matrix materials of liquid crystal/polymer composite films for display application. Liquid crystalline compounds which have azo group as center link, cyano group at one of the terminal position in common and bromoalkyl(azo(n)), azidoalkyl(AZI(n)), aminoalkyl(ALC(n)) as the terminal group were synthesized and identified respectively by FT-lR, $^1H-NMR$ spectrometer and elemental analysis. All these compounds exhibited nematic liquid crystalline region in the certain temperature range as determined by DSC and polarized optical microscope. These liquid crystalline compounds also showed a typical even-odd effect in both $T_{KN}$ and $T_{NI}$ due to conformational change as the length of terminal alkyl chain, $-(CH_2)n-$. was varied.

• The Korean Journal of Zoology
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• v.33 no.4
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• pp.476-492
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• 1990

Sodium arsenite (As) aqueous solution containing 4 ppm wss given to male rats for 15 days as drinking water. Electrophoretic pattern of liver cytosol from As-fed rats appeared to be significantly different from that of the control rats. Although the normal protein content of the cytosol fraction of As-fed rat liver was decreased, 8 stress proteins were increased. In liver cytosol fractions of As-treated rat, one kind of arsenic-binding substance (AsBS) was observed. Molecular weight of AsBS was identified to be 500 D and composition of amino acid was glycine, glutamic acid and cysteine. Glutathione (GSH) appeared to bind to arsenic and GSH-As complex showed the same mobility as AsBS on gel filtration chromatography. GSH conjugated As prevented As from inhibiting respiration, conformational change and swelling-contration of mitochondria. According to the above results. it is concluded that in vfuo treated arsenic stimulated synthesis of stress protein, and arsenic-binding substance might be glutathione and have a protective role against arsenic toxicity.

• BMB Reports
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• v.34 no.3
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• pp.268-273
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• 2001

In addition to the recognition site for glutamate, the N-methyl-D-aspartate (NMDA)-preferring glutamate receptor subtype shows a binding site for glycine. In this paper, we present the effects of 3-(4,6-dichloro-2-carboxymethylamino-5,7-dichloroquinoline-2-carboxylic acid (MDL 29951), a potent inhibitor of glycine binding to the NMDA receptor, on glutamate dehydrogenase (GDH) from bovine brains. The incubation of GDH isoproteins from bovine brains with MDL 29951 resulted in a dose-dependent loss of enzyme activity Separately or together, 2-oxoglutarate and NADH did not give an efficient protection against the inhibition, indicating that GDH isoproteins saturated with NADH or 2-oxoglutarate are still open to attack by MDL 29951. MDL 29951 was an uncompetitive inhibitor with respect to both 2-oxoglutarate and NADH for GDH isoproteins. These results suggest that the binding site of MDL 29951 is not directly located at the catalytic site, and the inhibition of GDH isoproteins by MDL 29951 is probably due to a steric hindrance, or a conformational change altered upon the interaction of the enzyme with its inhibitor. The inhibitory effects of MDL 29951 on GDH isoproteins were significantly diminished in the presence of ADP. GDH I reacted more sensitively with ADP than GDH II on the inhibition by MDL 29951. Our results suggest a possibility that the two types of GDHs are differently regulated by MDL 29951, depending on the physiological concentrations of ADP.

• BMB Reports
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• v.32 no.5
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• pp.515-520
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• 1999

Incubation of two types of glutamate dehydrogenase isoproteins from bovine brain with the arginine-specific dicarbonyl reagent phenylglyoxal resulted in a biphasic loss of enzyme activity. Reaction of the glutamate dehydrogenase isoproteins with phenylglyoxal caused a rapid loss of 53~62% of the enzyme activities and modification of two residues of arginine per enzyme subunit. Prolonged incubation of the glutamate dehydrogenase isoproteins with phenylglyoxal resulted in the modification of an additional four residues of arginine per enzyme subunit without further loss of the residual activities. Partial protection against inactivation was provided by the coenzyme NADH or substrate 2-oxoglutarate. The most marked decrease in the rate of inactivation was observed by the combined addition of NADH and 2-oxoglutarate, suggesting that the first two modified arginine residues are in the vicinity of the catalytic site. However, inactivation of the glutamate dehydrogenase isoproteins by phenylglyoxal appears to be partial with approximately 40% activity remained after an extended reaction time with excess reagent, suggesting that the modified arginine residues may not be directly involved in catalysis. The lack of complete protection by substrates also suggest the possibility that the modified arginine residues are not directly involved at the active site, and the partial loss of activity by the modification of arginine residues may be due to a conformational change. There were no significant differences between the two glutamate dehydrogenase isoproteins in sensitivities to inactivation by phenylglyoxal, indicating that the microenvironmental structures of the glutamate dehydrogenase isoproteins are very similar to each other.

• BMB Reports
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• v.30 no.6
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• pp.397-402
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• 1997

A thiol-specific spin label was attached to cysteine-102 of yeast cytochrome c and electron paramagnetic resonance (EPR) spectra were measured as a function of added cytochrome c oxidase concentration. The intensity decreased due to line broadening as cytochrome c formed a complex with cytochrome c oxidase and reached a minimum when the ratio of cytochrome c to cytochrome c oxidase became one. Replacement of either Lys-72 or Lys-87 of cytochrome c by Glu did not result in a significant change in binding affinity. Interestingly the K72E mutant, unlike K87E, had a much lower rate of electron transfer than the wild type. These results indicate that many positively charged residues as a group participate in complex formation but Lys-72 might be important for cytochrome c to be locked in an orientation for an efficient electron transfer. A stoichiometry of 1 was also confirmed by optical absorption of the cytochrome c-cytochrome c oxidase complex which had been run through a gel chromatography cloumn to remove unbound cytochrome c. The EPR spectrum of this 1:1 complex, however, was a mixture of two components. This explains a biphasic kinetics for a single binding site on cytochrome c oxidase without invoking conformational transition.

• Journal of the Korean Magnetic Resonance Society
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• v.2 no.2
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• pp.141-151
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• 1998

Human annexin I is a member of annexin family of calcium dependent phospholipid binding proteins, which have been implicated in various physiological roles including phospholipase A2(PLA2) inhibition, membrane fusion and calcium channel activity. In this work, the structure of N-terminally truncated human annexin I ({{{{ DELTA }}-annexin I) and its interactions with Ca2+, ATP and cAMP were studied at atomic level by using nuclear magnetic resonance (NMR) spectroscopy. The effect of Ca2+ binding on the structure of {{{{ DELTA }}-annexin I was investigated. The addition of Ca2+ to {{{{ DELTA }}-annexin I caused some changes in 13C NMR spectra. Carbonyl carbon resonances of some histidines were significantly broadened by Ca2+ binding. However, in the case of methionine, phenylalanine, and tyrosin, small changes could be observed. We found that ATP and cAMP bind {{{{ DELTA }}-annexin I, and the binding ratio of ATP to {{{{ DELTA }}-annexin I is 1. These results are well consistent with the report that cAMP and ATP interact with annexin I, and affect the calcium channels formed by annexin I. Because {{{{ DELTA }}-annexin I is a large protein with 35 kDa molecular weight, site-specific (carbonyl-13C) labeling technique was used to study the interaction sites of {{{{ DELTA }}-annexin I with Ca2+. NMR study was focused on the carbonyl carbon resonances of tyrosine, phenylalanine, methionine and histidine residues of {{{{ DELTA }}-annexin I because the number of these amino acids is small in the amino acid sequence of {{{{ DELTA }}-annexin I.

• Journal of the Korean Chemical Society
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• v.23 no.4
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• pp.187-197
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• 1979

The molar optical rotation of poly(cis-5-methylproline) was measured in solvent mixtures of chloroform and chloroethanol. After proper allowance for time-dependent mutarota-tions, equilibrium states between form A and form B were observed to occur with a solvent composition of 0.5~10 % chloroethanol in chloroform by volume. From the equilibrium constants, which were calculated by optical rotations at equilibrium measured at three different temperatures (5, 25, and 45 $^{circ}$C), the thermodynamic parameters-free enthalpy, enthalpy and entropy changes for the mutarotation-were evaluated. It was found that starting with equimolar concentrations of form A and form B, the forward mutarotation occurred in the solvent compositions of chloroethanol greater than 3 % by volume, whereas the reverse mutarotation resulted in solvent compositions of chloroethanol less than 3 % by volume. The changes in enthalpy and entropy for the forward mutarotation were found to be positive, while those were for the reverse mutarotation were negative. The driving forces for the forward mutarotation were found to be the increase in entropy, whereas that for the reverse mutarotation was the negative enthalpy change. The thermodynamic data were explained by the interaction between polymer and solvent, i.e., preferential hydrogen bonding of chloroethanol with the carbonyl group in form B over form A, and by difference in conformational energies between form A and form B.

• BMB Reports
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• v.41 no.1
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• pp.62-67
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• 2008

The present study was aimed to elucidate the mechanism of stabilization of tubulin by deuterium oxide ($D_2O$). Rate of decrease of tryptophan fluorescence during aging of tubulin at 4$^{\circ}C$ and 37$^{\circ}C$ was significantly lower in $D_2O$ than in $H_2O$. Circular dichroism spectra of tubulin after incubation at 4$^{\circ}C$, suggested that complete stabilization of the secondary structure in D2O during the first 24 hours of incubation. The number of available cysteine measured by DTNB reaction was decreased to a lesser extent in $D_2O$ than in $H_2O$. . During the increase in temperature of tubulin, the rate of decrease of fluorescence at 335 nm and change of CD value at 222 nm was lesser in $D_2O$. Differential Scanning calorimetric experiments showed that the $T_m$ values for tubulin unfolding in $D_2O$ were 58.6$^{\circ}C$ and 62.17$^{\circ}C$, and in $H_2O$. those values were 55.4$^{\circ}C$ and 59.35$^{\circ}C$.

• Food Science of Animal Resources
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• v.25 no.4
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• pp.458-464
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• 2005

This study was conducted to evaluate the effect of gamma irradiation for the reduction of an egg allergy in a cake with the irradiated egg white. A white layer cake was manufactured including 10- or 20-kGy-irradiated egg white. Enzyme-Iinked immunosorbent assays (ELISAs) with immunoglobulin (Ig) E from egg-allergic patient and with rabbit anti-ovalbumin (OVA) IgG were used to identify and quantify native OVA in the samples. Concentrations of native OVA detected by IgE and IgG in the control were $432.88{\mu}g/g$ sanple and $375.46{\mu}g/g$ sample, respectively. However, native OVA in white layer cake prepared with 10- and 20-kGy-irradiated egg white were detected at low concentrations detected by IgE to 14.27 and $8.78{\mu}g/g$ sample, respectively. Whereas, IgG recognized OVA more often in 10- and 20-kGy samples than in control. The result appear to suggest that irradiating egg white might reduce ie allergenicity by the conformational change of OVA. Therefore, gamma irradiation could utilize reduce an egg allergy.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.2
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• pp.86-91
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• 2005

The layered structure of organic-inorganic perovskite hybrids, $(C_nH_{2n+1}NH_3)_2CuC1_4$ (n = 6, 8, 10, 12) have synthesized. In $(C_nH_{2n+1}NH_3)_2CuC1_4$ compounds, the long-chain protonated alkylammonium ions as tilted bilayer type are inserted into perovskite-type layers of corner sharing $CuCl_6$ octahedron. Three solid phases have been characterized in the perovskite layered compound $(C_nH_{2n+1}NH_3)_2CuC1_4$ using HT-XRD and DSC. The $(C_nH_{2n+1}NH_3)_2CuC1_4$ compounds shows solid-solid phase transitions with stepwise increasing of the layer distance. Three different structures are explained by the conformational change of the long-chain protonated alkylammonium ions.