• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.939-945
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• 1997

Several types of 4-substituted-quinoline-2-carboxylic acid derivatives possessing different substituents at C4-position such as sulfonyl, phosphonyl, carbonyl groups, or a flexible alkyl chain have been synthesized and evaluated for their in vitro antagonistic activity at the glycine site on the N-methyl-D-aspartate (NMDA) receptor. Of them, 5,7-dichloro-4-(tolylsulfonylamino)-quinoline-2-carboxylic acid 9 was found to have the best in vitro binding affinity with IC50 of 0.57 μM. On the other hand, in compounds 21 and 22 the introduction of flexible alkyl chains on C4 of the quinoline mother nuclei caused a significant decrease of the in vitro binding affinity. In addition, replacement of polar carboxylic acid group on C2 by neutral bioisosteres in compounds 23a-d also seems to be disadvantageous to in vitro activity. In the structure-activity relationship (SAR) study of the 4-substituted quinoline-2-carboxylic acid acid derivatives, it was realized that the substitution pattern on C4 significantly influences on the binding affinity for the glycine site of NMDA receptor and the binding affinity might be increased by the introduction of a suitable electron rich substituent at C4 which has the ability of H-bonding donor.

• Preventive Nutrition and Food Science
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• 제6권1호
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• pp.79-81
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• 2001

Deoxynucleoside kinases exist as heterodimeric pairs specific for deoxyadenosine/deoxyguanosine kinase (dAK/dGK) and deoxyadenosine/deoxycytidine kinase (dAK/dCK). The aspartic acid-84 in dGK was mutated to alanine, asparagine and glutamic acid by site-directed mutagenesis. The mutation resulted in a drastic decease in dGK activity compared to the unmodified cloned enzyme while it increased production of dAK activity. The mutated dak/dgk genes, which synthesize tandem deoxyadenosine/deoxyguanosine kinase, were inserted back to the Lactobacillus acidophilus and Lactococcus lactis by electroporation to determine the effect of site-directed mutation of he enzymes on the microbial growth. However, no significant change was observed in cell growth and lactic acid production between wild type and mutant lactic acid bacteria.

• Journal of Photoscience
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• 제9권2호
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• pp.33-36
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• 2002

In vertebrate rhodopsins the glutamic acid at position 113 serves as a counterion to stabilize the protonated retinylidene Schiff base linkage and to shift the spectrum to the visible region. Invertebrate rhodopsins and retinochrome have the amino acid residue different from glutamic acid or asparatic acid at this position and therefore, these pigments may have a counterion at different position. We first investigated the counterion in retinochrome by site specific mutagenesis. The results showed that the counterion is the glutamic acid at position 181, where almost of all the pigments including vertebrate and invertebrate rhodopsins in the rhodopsin family have a glutamic acid or an aspartic acid. In vertebrate rhodopsins, however, Glu 181 does not act as a counterion, and the red-sensitive cone pigments have a histidine at this position, which serves as a chloride-binding site for red-shift of the absorption spectrum. These findings suggested that the role of Glu181 as a counterion may be weakened by the newly acquired counterion at position 113. Taken together with our recent studies on an invertebrate-type rhodopsin, the rhodopsin diversity was discussed from viewpoint of counterion.

• 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.

• 산업기술연구
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• 제21권A호
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• pp.17-26
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• 2001

The fatigue strength of SM55C has significantly decreased by 83% compared with atmosphere where distilled exists due to strong erosive action of acid fog. The reason is inferred in a way that strong acid erosive material such as acid fog act and give rise to multi-site crack on the surface. Several fatigue clacks occurred under the acid fog repeat the process of division and unification on the surface and form a long non-propagating crack throughout the circumference of experimented steel. However, in the depth, many parts do not show much trace of unification, and the depth is not as big as the one of normal crack shape. 10% of $CaCl_2$ causes strong erosive reaction to material. Then eventually make the life of fatigue shooter. On the other hand, 20% of $CaCl_2$ beings about oxidized material organic crack closing due to weak erosive reaction.

• Journal of Microbiology and Biotechnology
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• 제30권7호
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• pp.1104-1107
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• 2020

The N-terminal domain of the Pseudomonas sp. FB15 phytase increases low-temperature activity and catalytic efficiency. In this study, the 3D structure of the N-terminal domain was predicted and substitutions for the amino acid residues of the region assumed to be the active site were made. The activity of mutants, in which alanine (A) was substituted for the original residue, was investigated at various temperatures and pH values. Significant differences in enzymatic activity were observed only in mutant E263A, suggesting that the amino acid residue at position 263 of the N-terminal domain is important in enzyme activity.

• BMB Reports
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• 제34권4호
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• pp.305-309
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• 2001

MatR in Rhizobium trifolii is a malonate-responsive transcription factor that regulates the expression of genes, matABC, enabling decarboxylation of malonyl-CoA into acetyl-CoA, synthesis of malonyl-CoA from malonate and CoA, and malonate transport. According to an analysis of the amino acid sequence homology, MatR belongs to the GntR family The proteins of this family have two-domain folds, the N-terminal helix-turn-helix DNA-binding domain and the C-terminal ligand-binding domain. In order to End the malonate binding site and amino acid residues that interact with RNA polymerase, a site-directed mutagenesis was performed. Analysis of the mutant MatR suggests that Arg-160 might be involved in malonate binding, whereas Arg-102 and Arg-174 are critical for the repression activity by interacting with RNA polymerase.

• 한국위험물학회지
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• 제3권1호
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• pp.59-64
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• 2015

Semiconductor industry has large number of chemical inventory and is easily exposed to chemical release incidents. Toxic release is one of the most interested area in evaluating consequence to the vicinity of industry facilities handling hazardous materials. Hydrofluoric acid is one of the typical chemical used in semiconductor facility and is selected and toxic release is evaluated to assess the risk impacted to its off-site. Accident scenarios were listed using process safety information. The scenarios having effect to the off-site were selected and assessed further according to guideline provided by Korea government. Worst case and alternative scenarios including other interested scenarios were evaluated using ALOHA. Each evaluated scenario was assessed further considering countermeasures. The results showed that the facility handling hydroflooric acid is safe enough and needed no further protections at the moment.

• 대한치과보철학회지
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• 제32권3호
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• pp.368-377
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• 1994

In order to investigate the oral health status including dental erosion, the authors had surveyed and oral examined 510 male workers, among whom 199 workers were exposed to acids and 311 were not exposed to acids, in a factory using acids during the period from November, 26 to 27 in 1992. The obtained results were as follows ; 1. The positive rate of dental erosion between the acid exposed and non-exposed group didn't show statistical difference. But the positive rate of degree 1 dental erosion by degree was statistically high in the acid exposed group(P<0.05). 2. The acid exposed group showed the higher positive rate of degree 1 dental erosion in lower incisors by site(P<0.01). 3. To the average number of eroded teeth, the acid exposed group showed more degree 1 eroded teeth in lower incisors than the non-exposed(P<0.05). 4. Although the rate of dental erosion was increased according to the increase in tenure in both exposed and non-exposed group(P<0.05), there was no difference in rate of the dental erosion by site among the same tenure group. 5. In the acid exposed group, the rate of dental erosion between protective mask wearer group and non-wearer group was not statistically different, but upper incisors of the protective mask wearer group showed lower rate of dental erosion by site(P<0.05). 6. The positive rate of periodontal diseases was higher in the acid exposed group(P<0.01).

• 생명과학회지
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• 제15권4호
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• pp.633-640
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• 2005

Bacillus pumilus TX703으로부터 xylanase를 정제한 후 효소의 활성부위를 조사하기 위하여 여러 가지 화학수식제를 사용하여 효소활성의 저해도를 측정하였다. 여러 가지 화학수식제 중에서 carbodiimide와 N-bromosuccinimide가 효소활성을 완전히 저 해시 켜 glutamic acid 또는 aspartic acid 잔기와 tryptophan 잔기가 효소의 활성부위에 관여하리라 추측되었다. 각각의 경우에 효소 실활은 수식제의 첨가농도에 따라 pseudo first-order kinetics 양식을 보여주었으며, car-bodiimide와 N-bromosuccinimide는 각각 비경쟁적 저해와 경쟁적 저해방식을 나타내었다. 기질첨가에 의한 효소활성 보호실험을 통하여 tryptophan 잔기가 기질결합부위라 판단되었다. 효소실활속도의 분석에 의해 효소활성에는 2개의 glutamic acid 또는 aspartic acid 잔기와 1개의 tryptophan 잔기가 관여하는 것으로 나타났다.