• Bulletin of the Korean Chemical Society
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• 제24권8호
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• pp.1188-1192
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• 2003

In order to study the role of residue in the active site of glutathione S-transferase (GST), Tyr 108 residue in human GST P1-1 was replaced with alanine, phenylalanine and tryptophan by site-directed mutagenesis to obtain mutants Y108A, Y108F and Y108W. These three mutant enzymes were expressed in Escherichia coli and purified to electrophoretic homogeneity by affinity chromatography on immobilized GSH. The substitutions of Tyr108 significantly affected $K_m^{CDNB}$ and $K_m^{ETA}$, whereas scarcely affected $K_m^{GSH}$. The substitutions of Tyr108 also significantly affected $I_{50}$ of ETA, an electrophilic substrate-like compound. The effect of these substitutions on kinetic parameters and the response to inhibition suggests that tyrosine 108 in hGST P1-1 contributes to the binding of the electrophilic substrate and a major determinant in the binding of CDNB is the aromatic ring of Tyr108, not its hydroxyl group.

• 한국양식학회지
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• 제11권3호
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• pp.295-301
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• 1998

Since the end of the Pliocene, ancestral strains of Astyanax fasciatus have been accidently washed into different caves at the time of flooding and have lost their eyes and body pigments. Availability of this independently derived cave fish and their ancestral form within a single species provided a unique opportunity for studying the process of molecular evolution of the visual pigment gene. The nucleotide sequence comparisons of an ancestral river fish and two cave fish showed that nucleotide polymorphism of a green-like visual pigment gene between the eyed and blind form of A. fasciatus was much higher than that between the same blind form. Considering the number of nucleotide substitutions per nucleotide site and the direction of the nucleotide substitutions, more nucleotide substituions between the different forms of fish rater than the same one were probably due to more frequent mutations in the eyed river form. Nucleotide substitutions per site at the intron have been ocurred more than three times faster than those at the exon. This result indicates that the functional constraint has affected the green-like visual pigment gene of the blind cave fish although its eye sight is no longer required.

• Bulletin of the Korean Chemical Society
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• 제19권11호
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• pp.1253-1256
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• 1998

• 아동학회지
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• 제24권5호
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• pp.91-104
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• 2003

This study analized the strategies in beginning readers by age and reading ability. Sixty 4-and 5-year old subjects took a reading test based on Bsatjes & Brown(1997) and Park, et a1.(1989). They read contextual and non-contextual storybooks. Errors in oral reading were recorded as mispronunciations, substitutions, omissions, insertions, teacher-assistance and self-corrections. Mispronunciations and substitutions were Specifically evaluated for graphic and contextual reading strategies. Data were analyzed by percentage and mean. Results revealed that children made more mispronunciation errors in reading the non-contextual story book. They used graphic information more than contextual information. Fine-year olds and high-level readers developed the use of graphic and contextual cues simultaneously.

• BMB Reports
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• 제28권4호
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• pp.363-367
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• 1995

E. coli methionyl-tRNA synthetase is one of the class I tRNA synthetases. The Tryptophane residue at the position 461 located in the C-terminal domain of the enzyme is a key amino acid for the interaction with the anticodon of $tRNA^{Met}$. W461 was replaced with other amino acids to determine the chemical requirement for the interaction with the anticodon of $tRNA^{Met}$. Saturation mutagenesis at the position 461 generated a total of 12 substitution mutants of methionyl-tRNA synthetase. All the mutants showed the same in vivo stability as the wild-type enzyme, suggesting that the amino acid substitutions did not cause severe conformational change of the protein The mutants containing tyrosine, phenylalanine, histidine and cysteine substitutions showed in vivo activity while all the other mutants did not. The comparison of the in vitro aminoacylation activities of these mutants showed that aromatic ring structure, Van der Waals volume and hydrogen bond potential of the amino acid residue at the position 461 are the major determinants for the interaction with the anticodon of $tRNA^{Met}$.

• Journal of Microbiology
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• 제37권3호
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• pp.175-179
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• 1999

To elucidate the role of vir-box in the expression of the virE gene, the vir-box was modified by site-directed mutagenesis and tested for ${\beta}$-galactosidase activities. A, C, T T, A, C substitutions at -62, -63, and -65 positions, destroying the 5'-region of the vir-box and A T at position -55, destroying the 3'-region of the vir-box respectively, showed only 17% promoter activity. When the vir-box was modified to contain perfect dyad symmetry structure (DSR) by the substitutions T, G A, T at -60 an d-61 positions, ${\beta}$-glactosidase activity increased 302%. These results indicate that the 5' and 3'-region of vir-box as well as the imperfect DSR of the vir-box itself may play a very important role in the regulation of virE gene expression.

• 미생물학회지
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• 제29권5호
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• pp.278-283
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• 1991

Two amino acid residues ($Ala^{494}$ and $Ser^{495}$ of E. coli .gamma.-glutamylcysteine synthetase have been investigated whether they are the site of feedback inhibition by site specific mutagenesis. Single substitution of $serine^{495}$ (S495F), and double substitutions of alanine$^{494}$ and $serine^{495}$ (A494G-S495F) resulted in the inactivation of the .gamma.-glutamylcysteine synthetase activity. Substitution of $alanine^{494}$ with $glycine^{494}$ resulted in a higher level of feedback inhibition. These results suggest that $serine^{495}$ in .gamma.-glutamylcysteine synthetase is required for its catalytic acitvity and $alanine^{494}$ is presumably related to the feeback inhibition site.

• 말소리와 음성과학
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• 제6권4호
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• pp.101-108
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• 2014

This study investigates the effects of Japanese learners' Korean segmental production on pronunciation evaluation by Korean native raters. Read speech from 24 learners whose native language is Japanese are transcribed at the phonemic level, and confusion matrices are generated based on the phonemic transcriptions. The deviance from the canonical pronunciation found in the learners' speech is analyzed in terms of phoneme substitutions, vowel insertions, and consonant deletions. Each learner's pronunciation is rated impressionistically by 5 Korean native raters. The result shows that the deviance from the canonical pronunciation is strongly correlated with the pronunciation evaluation scores. Especially, the rates of phoneme substitutions and vowel insertions which are very strongly correlated with the pronunciation evaluation scores.

• 한국세라믹학회지
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• 제33권10호
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• pp.1131-1137
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• 1996

The dielectric properties and phase stabilities of Pb(Zn0.6Mg0.4)1/3Nb2/3O3 [PZMN]system were investigated into substitution of A-site with Ba, Sr and Ca ions. The A-site substitutions led to the complexity of components of perovskite phase and then DPT coefficient increased. The A-site substitutions of Ba or Sr ion perovskite single phase could be easily formed by columbite process due to increase of perovskite phase stability. The variation of lattice parameters in specimen obeyed Vegard's law and curie temperature and dielectric constant of specimen decreased linearly. But Ca substitution led to perovskite phae instability. The lattice parameter dielectric constant and curie temperature of specimens drasticaly decreased with formation of pyrochlore phase.

• 한국광물학회지
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• 제2권1호
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• pp.8-10
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• 1989

Sphene from the McDonald pegmatite near Bancroft, Ontario, Canada was analyzed using EPMA. It contains 4.3 to 6.3 weight percent of Nb2O5 with an average formula Ca1.02(Ti0.62Al0.22Nb0.07Fe0.06Ta0.01)Si0.99(O4.85F0.16). Three types of subtitutions are possible; 1)2Ti4+=(Nb, Ta)5+ + (Al, Fe3+), 2) Ti + O = (Al, Fe3+) + (F, OH), and 3) 2Ti + O = Fe2+ + (Nb, Ta)5+ + (F, OH). T재 different schemes of substitutions for balancing the analysis are considered when the iron is either all ferric or all ferrous. Assuming stoichiometry fo Ca and Si, a general formula derived from the two different schemes is Ca(Ti0.64Al0.22Fe3+0.06-X {{{{Fe_{x}^{2+} }} Nb0.01)Sio4.80-XF0.16(OH)0.04+x.