• International Journal of Industrial Entomology and Biomaterials
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• 제7권1호
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• pp.37-44
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• 2003

Alcohol dehydrogenases (AHDs) are enzymes responsible for the catalysis of the reversible conversion of various alcohols to their corresponding aldehydes and ketonesis. Until now cDNA sequences of ADH gene is informed exclusively from several diptean species. We describe here the cDNA sequence and mRNA expression of a putative ADH gene from the mole cricket, Gryllotalpa orientalis, and phylogenetic relationships among known insect ADHs. The G. orientalis ADH cDNA sequences comprised of 798 bp encoding 266 amino acid residues. The multiple sequence alignment of G. orientalis ADH gene and known dipteran ADHs shared 100％ identity in the nine amino acid residues that are important for the enzymatic activity in Drosophila melanogaster. Percent sequence identity ranged from 25％ to 32％ among all insect ADHs including both types of ADHs. G. orientalis ADH gene showed no clear resemblance to any dipteran species and type. Phylogenetic analysis of the deduced amino acid sequences of G. orientalis ADH gene with available dipteran ADH genes including both types of ADHs further confirmed that the G. orientalis ADH gene is not clearly assigned to either type of ADHs. Northern blot analysis revealed a stronger signal in the fat body than midgut and epidermis, indicating that the fat body possibly is a main site for the synthesis of the G. orientalis ADH protein.

• Journal of Microbiology and Biotechnology
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• 제9권6호
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• pp.811-819
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• 1999

The ${\beta}-CGTase$ gene of alkalophilic Bacillus firmus var. alkalophilus was cloned into E. coli using $pZErO^{TM}-2$ as a vector. The cloned gene encoded a total of 710 amino acid residues consisting of 674 amino acids of the matured protein and 36 amino acids of the signal peptide, including 20 amino acids from the lacZ gene in the vector. Although the cloned ${\beta}-CGTase$ gene did not contain the promoter and start codons, it was expressed by the lac promoter and lacZ start codon in the $pZErO^{TM}$ vector. A comparison was made with the amino acid sequence and ten other CGTases from Bacillus sp. Also, ten highly conserved regions, which are important amino acid residues in catalysis of CGTase, were identified. The lac promoter used for expression of the ${\beta}-CGTase$ gene was induced constitutively in recombinant E. coli even without IPTG possibly because of a lack of the lacI gene in both host and vector, repressing the lacZ gene in the lac operon. Its expression was catabolically repressed by glucose, however, its repression was reduced by soluble starch, mainly because of the extremely high increase of the cAMP level. ${\beta}-CGTase$ can be overproduced in the recombinant E. coli by maintaining intracellular cAMP levels mostly through the intermittent feeding of glucose during cultivation.

• Journal of Microbiology and Biotechnology
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• 제16권9호
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• pp.1434-1440
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• 2006

The stable anchorage of pyridoxal 5'-phosphate (PLP) in the active site of D-amino acid transaminase (D-AT) is crucial for the enzyme catalysis. The three-dimensional structure of D-AT revealed that Glu32 is one of the active site groups that may playa role in PLP binding. To prove the role of Glu32 in PLP stability, we firstly checked the rate of the potential rate-limiting step. The kinetic analysis showed that the rate of the ${\alpha}$-deprotonation step reduced to 26-folds in E32A mutant enzyme. Spectral analyses of the reaction of D-AT with D-serine revealed that the E32A mutant enzyme failed to stabilize the key enzyme-substrate intermediate, namely a quinonoid intermediate (E-Q). Finally, analysis of circular dichroism (CD) on the wild-type and E32A mutant enzymes showed that the optical activity of PLP in the enzyme active site was lost by the removal of the carboxylic group, proving that Glu32 is indeed involved in the cofactor anchorage. The results suggested that the electrostatic interaction network through the groups from PLP, Glu32, His47, and Arg50, which was observed from the three-dimensional structure of the enzyme, plays a crucial role in the stable anchorage of the cofactor to give necessary torsion to the plane of the cofactor-substrate complex.

• KSBB Journal
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• 제24권3호
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• pp.267-272
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• 2009

셀룰로오즈는 포도당 단위체가 $\beta$-1,4-glucoside결합을 이뤄 긴 사슬형태를 띈다. 또한 리그노셀룰오로직 물질에서의 셀룰로오즈 중 $50{\sim}90%$는 수소결합에 의해 결정형으로 존재하고 나머지 부분은 무정형으로 존재한다. 본 연구에서는 셀룰로오즈를 구성하는 포도당의 분해 생성물을 화인하기 위해 셀룰로오직 바이오매스 (유채대)와 1.5 g/l의 순수한 포도당을 반응온도 $164^{\circ}C$, 산 농도 0.77% (w/w) $H_2SO_4$, $0{\sim}20$ min동안 묽은 산 가수분해 시켜 분해물의 생성량 변화를 관찰하였다. 포도당을 묽은 산에 의해 분해시키면 탈수반응에 의해 1,6-anhydroglucose가 생성되며, 또한 포도당의 이성질체인 과당으로 전환되고 이 과당은 HMF와 포름산으로 전환된다. 또한 산 농도, 반응온도가 포도당 분해에 영향을 미치는 주요 변수임을 확인할 수 있었다. 그리고 분해생성물 중 하나인 HMF 1.308 g/l를 반응온도 $164^{\circ}C$, 산 농도 0.77% (w/w) $H_2SO_4$, $0{\sim}20$ min동안 산 가수분해 시켜 HMF와 HMF 분해물의 변화를 확인하였다.

• Korean Chemical Engineering Research
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• 제55권2호
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• pp.270-274
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• 2017

본 연구에서는 양자 역학 계산 이론 중 하나인 Density Functional Theory (DFT)를 사용하여 $Pd/Pd_3Fe$ 촉매 표면에서 개미산(HCOOH) 분해 반응으로부터 수소를 생산하는 반응 메커니즘을 분석하였다. 기존 연구에 따르면, 단일 원자 촉매 중에서 개미산 분해 반응에 가장 높은 수소 생산성을 기록하는 원자는 Pd 촉매이지만, 부 반응으로 생산되는 CO가 Pd에 독성을 띄우기 때문에 Pd 촉매의 성능을 저하시킨다. 이러한 단점을 극복하고자, Pd를 기반으로 Pd와 Fe를 3:1로 합금하여 $Pd_3Fe$가 코어(core) 형태로 존재하고 Pd가 표면에 위치한 core-shell $Pd/Pd_3Fe$ 촉매를 설계하여 개미산 분해 반응에 의한 수소 생산 속도를 계산하였다. 순수 Pd촉매 보다 $Pd/Pd_3Fe$ 촉매의 수소 생산 반응의 활성 에너지가 감소하였다. 그 이유는 Pd와 Fe가 합금화 되면서 $Pd_3Fe$의 격자 상수가 $2.76{\AA}$로 줄어 들어 HCOO의 흡착에너지를 0.03 eV 감소시켰고, Fe에서 표면 Pd로 전자가 이동하면서 표면 전자 구조가 변화하여 HCOO의 흡착에너지를 0.29 eV 낮추었기 때문이다. 본 연구에서 제안하는 결과를 바탕으로 추후 개미산으로부터 수소 생산이 더 용이한 새로운 촉매 설계 메커니즘을 제안하고자 한다.

• BMB Reports
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• 제42권9호
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• pp.552-560
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• 2009

Cyclooxygenases (COX-1 and COX-2) are ER-resident proteins that catalyze the committed step in prostanoid synthesis. COX-1 is constitutively expressed in many mammalian cells, whereas COX-2 is usually expressed inducibly and transiently. Abnormal expression of COX-2 has been implicated in the pathogenesis of chronic inflammation and various cancers; therefore, it is subject to tight and complex regulation. Differences in regulation of the COX enzymes at the posttranscriptional and posttranslational levels also contribute significantly to their distinct patterns of expression. Rapid degradation of COX-2 mRNA has been attributed to AU-rich elements (AREs) at its 3’UTR. Recently, microRNAs that can selectively repress COX-2 protein synthesis have been identified. The mature forms of these COX proteins are very similar in structure except that COX-2 has a unique 19-amino acid (19-aa) segment located near the C-terminus. This C-terminal 19-aa cassette plays an important role in mediation of the entry of COX-2 into the ER-associated degradation (ERAD) system, which transports ER proteins to the cytoplasm for degradation by the 26S proteasome. A second pathway for COX-2 protein degradation is initiated after the enzyme undergoes suicide inactivation following cyclooxygenase catalysis. Here, we discuss these molecular determinants of COX-2 expression in detail.

• Macromolecular Research
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• 제17권5호
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• pp.289-295
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• 2009

Low viscosity aromatic hyperbranched polyester epoxy resin (HTBE) was synthesized by the reaction between epichlorohydrin (ECH) and carboxyl-end hyperbranched polyester (HTB) which was prepared from inexpensive materials $A_2$ (1,4-butanediol glycol, BEG) and $B_3$ (trimellitic anhydride, TMA) by pseudo one-step method. The molar mass of the HTB was calculated from its acid value by "Recursive Probability Approach". The degree of branching (DB) of the HTB was characterized by model compounds and $^1H$ NMR-minus spectrum technology, and the DB of the HTB was about $0.47{\sim}0.63$. The viscosity and epoxy equivalent weight of the HTBE were $3,600{\sim}5,000\;cp$ and lower than 540 g/mol respectively. The reaction mechanism and structure of the $AB_2$ monomer, HTB and HTBE were investigated by MS, $^1H$ NMR and FTIR spectra technology. The molecular size of HTBE is under 8.65 nm and its shape is ellipsoid-like as determined by molecular simulation.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVI)
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• pp.580-583
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• 2005

The aim of this study was to prepare a hydrogels composed of alginate blended with a carboxymethyl scleroglucan (CMSC) and evaluate the feasibility of the hydrogels as a drug delivery system for a protein. The main advantage of the alginate/CMSC hydrogels is to improve a restricted drug release from alginate hydrogels. The CMSC was chemically synthesized with chloroacetic acid and confirmed using a FT-IR. The alginate/CMSC hydrogels were prepared at distinct compositions by crosslinking with calcium ions. The swelling ratios of these hydrogels increased significantly with increasing the content of CMSC. At pH 7.4, the swelling ratios of the hydrogels increased remarkably as compared to those at pH 1.2. In ovalbumin (OVA) release test, the amount of OVA released from the hydrogels showed higher as compared to those released at pH 1.2. In addition, the release of OVA was improved with increasing the content of CMSC. Thus, the alginate/CMSC hydrogels may be used as a potential system for oral delivery of protein drugs.

• Parasites, Hosts and Diseases
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• 제40권3호
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• pp.131-138
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• 2002

The cyclophilins (Cyps) are family members of proteins that exhibit peptidylprolyl cis-trans isomerase (PPIase, EC 5.2.1.8) activity and bind the immunosuppressive agent cyclosprin A (CsA) in varying degrees. During the process of random sequencing of a cDNA library made from Giardia intestinalis WB strain, the cyclophilin gene (gicypl) was isolated. An open reading frame of gicyp1 gene was 576 nucleotides, which corresponded to a translation product of 176 amino acids (Gicypl). The identity with other Cyps was about 58-71%. The 13 residues that constituted the CsA binding site of human cyclophilin were also detected in the amino acid sequence of Gicypl, including tryptophan residue essential for the drug binding. The single copy of the gicypl gene was detected in the G. intestinalis chromosome by southern hybridization analysis. Recombinant Gicyp 1 protein clearly accelerated the rate of cis ${\rightarrow}$ trans isomerization of the peptide substrate and the catalysis was completely inhibited by the addition of $0.5{\;}{\mu}M$ CsA.

• Carbon letters
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• 제12권1호
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• pp.1-7
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• 2011

In the present study, the removal of Pb (II) ions on oxidized activated carbons (ACs) was investigated. ACs were derived from activation of indigenous cotton stalks waste with potassium hydroxide (KOH) in two-stage process. The KOH-ACs were subjected to liquid-phase oxidation with hot $HNO_3$ and one untreated sample was included for comparison. The obtained carbons were characterized by Fourier transform infrared (FTIR), slurry pH and $N_2$-adsorption at 77 K, respectively. Adsorption capacity of Pb (II) ions on the resultant carbons was determined by batch equilibrium experiments. The experimental results indicated that the oxidation with nitric acid was associated with a significant increase in mass of yield as well as a remarkable reduction in internal porosity as compared to the untreated carbon. The AC-800N revealed higher adsorption capacity than that of AC-800, although the former sample exhibited low surface area and micropore volume. It was observed that the adsorption capacity enhancement attributed to pore widening, the generation of oxygen functional groups and potassium containing compounds leading to cation-exchange on the carbon surface. These results show that the oxidized carbons represented prospective adsorbents for enhancing the removal of heavy metals from wastewater.