• 분석과학
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• 제33권5호
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• pp.209-214
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• 2020

This study has been carried out to develop a standard method for quantifying of 3 permitted artificial sweeteners (including sodium saccharine, aspartame, acesulfame potassium) contained in foods by HPLC-DAD. A simple and rapid sample pretreatment method was used to remove fat and protein from the test solution with Carrez clearing regent precipitant know to be effective for protein and fat removal. The artificial sweeteners in the test solution purified through sample pretreatment were detected by high performance liquid chromatograph using a Reverse phase C18 column (5 ㎛, 4.6 × 250 mm). The simultaneous quantitative test of 3 kinds of artificial sweeteners can be effectively performed on the high fat emulsified foods containing a large amount of fat. Using the established simultaneous quantitative test method, artificial sweeteners were tested in foods such as dairy products, snacks and chocolate. The results calibration curve showed good linearity with high regression coefficients and the result of recovery test showed satisfactory recoveries within 80~110 %.

• Journal of Microbiology and Biotechnology
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• 제18권2호
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• pp.283-286
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• 2008

The methylenetetrahydrofolate dehydrogenase/cyclohydrolase (MTHFDC) from the thermoacidophilic archaeon Thermoplasma acidophilum is a 30.6kDa molecular-mass enzyme that sequentially catalyzes the conversion of formyltetrahydrofollate to methylenetetrahydrofolate, with a preference for NADP as a cofactor, rather than NAD. In order to elucidate the functional and structural features of MTHFDC from archaeons at a molecular level, it was overexpressed in Escherichia coli and crystallized in the presence of its cofactor, NADP, at 295K using polyethylene glycol (PEG) 4000 as a precipitant. The crystal is a member of the monoclinic space group $P2_1$, with the following unit cell parameters: $a=66.333{\AA},\;b=52.868{\AA},\;c=86.099{\AA},\;and\;{\beta}=97.570^{\circ}$, and diffracts to a resolution of at least $2.40{\AA}$ at the synchrotron. Assuming a dimer in the crystallographic asymmetric unit, the calculated Matthews parameter $(V_M)\;was\;2.44{\AA}^3/Da$ and the solvent content was 49.7%.

• Journal of Microbiology and Biotechnology
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• 제18권2호
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• pp.295-298
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• 2008

Creatine kinase (CK; E.C. 2.7.3.2) is an important enzyme that catalyzes the reversible transfer of a phosphoryl group from ATP to creatine in energy homeostasis. The brain-type cytosolic isoform of creatine kinase (BB-CK), which is found mainly in the brain and retina, is a key enzyme in brain energy metabolism, because high-energy phosphates are transfered through the creatine kinase/phosphocreatine shuttle system. The recombinant human BB-CK protein was overexpressed as a soluble form in Escherichia coli and crystallized at $22^{\circ}C$ using PEG 4000 as a precipitant. Native X-ray diffraction data were collected to $2.2{\AA}$ resolution using synchrotron radiation. The crystals belonged to the tetragonal space group $P4_32_12$, with cell parameters of a=b=97.963, $c=164.312{\AA},\;and\;{\alpha}={\beta}={\gamma}=90^{\circ}$. The asymmetric unit contained two molecules of CK, giving a crystal volume per protein mass $(V_m)$ of $1.80{\AA}^3\;Da^{-1}$ and a solvent content of 31.6%.

• Journal of Microbiology and Biotechnology
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• 제20권2호
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• pp.325-331
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• 2010

Rhodococcus erythropolis amidase was expressed in Escherichia coli cells. The crude amidase in the cell-free extract was immobilized using the cross-linked enzyme aggregate (CLEA) method. The crude amidase was mixed with bovine serum albumin and then precipitated with ammonium sulfate. The resultant precipitant was subsequently cross-linked with glutaraldehyde. Scanning electron microscopy revealed that this co-CLEA had a ball-like shape with a diameter of approximately $1\;{\mu}m$. This co-CLEA evidenced hydrolytic activity toward a variety of amide substrates. The amidase co-CLEA evidenced an optimum temperature of $60^{\circ}C$ and an optimum pH of 8.0, results that were similar to those of the soluble amidase. The reaction stability of the co-CLEA was increased. That is, it was stable up to $50^{\circ}C$ and in a pH range of 5.0-12.0. Additionally, the co-CLEA could be recovered by centrifugation, and retained 96% activity after 3 repeated cycles. This amidase co-CLEA may prove useful as a substitute for soluble amidase as a biocatalyst in the pharmaceutical and chemical industries.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.657-661
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• 2002

PZT powder was prepared by partial oxalate method using $(Zr_{0.53}Ti_{0.47})O_2$, $Pb(NO_3)_2$ and $(COOH)_2{\cdot}2H_2O$ as a precipitant. $Nb_2O_5$ additive effect on microstructure and piezoelectric properties of PZT ceramics were investigated. The coexistence of rhombohedral and tetragonal phases of PZT ceramics at the sintering temperature of $1100^{\circ}C$ was revealed from the X-ray diffraction patterns. The grain size PZT ceramics was decreased with the increase $Nb^{5+}$. and the sinterbility of PZT ceramics was decreased with the increase $Nb^{5+}$ addition. The electromechanical coupling factors $K_p$ show above 0.60 at $1100^{\circ}C$ sintering temperature by $Nb_2O_5$ addition above 0.6mol%.

• 한국추진공학회지
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• 제3권1호
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• pp.48-54
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• 1999

질산암모늄(AN)과 potassium dinitramide(KDN)의 수용액으로부터 염석법에 의해 상안정화 질산암모늄(PSAN)을 제조하는 방법을 나타내었다. 침전제로 사용된 유기 용매는 아세토니트릴이었다. 침전된 결정들의 DSC 분석결과 이들 결정들이 PSAN임을 확인하였고, 침전된 결정중의 KDN 함량이 약 6 무게 % 이상일 때 $0^{\cire}C$에서 $80^{\cire}C$의 온도 범위내에서 AN이 안정화되었다. 제조된 결정들은 고체 로켓 추진제 및 폭약 둥의 제조에서 산화제로 사용될 수 있을 것이다.

• 한국결정학회지
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• 제5권1호
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• pp.20-23
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• 1994

대장균의 IciA 단백질은 DnaA 단백질의 작용장소에 결합하여 DNA의 복제가 개시되는 것을 막는다. 따라 서 IciA단백질은 세포주기의 주요 단계에서 결정적인 역할을 한다. 이러한 IciA 단백질의 구조와 기능간의 관 계를 연구하기 위하여 X-선 결정학을 이용하여 삼차원 구조를 결정하고자 한다. 그 첫 단계로 IciA단백질 결정화를 시도하였다. sodium formate를 침전제로 이용하여 결정을 얻을 수 있었다.

• 한국결정학회지
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• 제15권1호
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• pp.40-43
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• 2004

The peptide deformylase from the pathogenic bacterium Staphylococcus aureus has been over-expressed in Escherichia coli and crystallized in the presence of the inhibitor actinonin at 297 K using polyethylene glycol 20000 as a precipitant. X-ray diffraction data have been collected to 2.2 ${\AA}$ resolution. The crystal is trigonal, belonging to the space group $P3_121$ (or its enantiomorph $P3_221$), with unit cell parameters of a = b = 62.70 ${\AA}$ c = 108.23 ${\AA}$, ${\alpha}\;=\;{\beta}\;=\;90^{\circ},\;and\;{\gamma}\;=\;120^{\circ}$. An asymmetric unit contains a monomer of the recombinant enzyme, giving a $V_M$ of 2.84 ${\AA}^3\;Da^_{-1}$ and a solvent content of 56.7%.

• 한국세라믹학회지
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• 제52권6호
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• pp.521-526
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• 2015

$Ce_{0.8}Gd_{0.2}O_{1.9}$(GDC20) powder was prepared from a mixture of submicron-sized $CeO_2$ powder and Gd precipitates using ammonium carbonate $((NH_4)_2CO_3)$ as a precipitant. The mixture was calcined at $700^{\circ}C$ for 4 h followed by ball-milling that resulted in the GDC powder with an average particle size of $0.46{\mu}m$. The powder had a very uniform particle size distribution with particle sizes ranging from $0.3{\mu}m$ to $1{\mu}m$. Sintering of undoped GDC samples did not show a relative density of 99.2% until the temperature was increased to $1500^{\circ}C$, whereas GDC samples doped with 5 mol% CoO exhibited a significant densification at lower temperature reaching a relative density of 97.6% at $1100^{\circ}C$ and of 98.8% at $1200^{\circ}C$.

• Food Science and Biotechnology
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• 제15권2호
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• pp.189-195
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• 2006

A study was conducted to develop optimal conditions for a large-scale, sequential separation method for value-added components from egg yolk. Starting with liquid egg yolk, immunoglobulin Y (IgY), phospholipids, and neutral lipids were extracted sequentially using water, ethanol, and n-hexane. The remainder was yolk proteins. Adjusting the pH of diluted egg yolk to pH 5.0-5.2 decreased phospholipids content in the supernatant after centrifugation, which was very important for preventing clogging problem of ultrafiltration filters during the subsequent concentration step for IgY separation. Extraction of precipitants after centrifugation with four volumes of 100% ethanol once removed most of the phospholipids and the purity of phospholipids was more than 85% (wt.) after drying. The subsequent extraction of precipitant from ethanol extraction with four volumes of hexane 3 times removed neutral lipids almost completely and resulted in a high protein product with minimal lipids. The sequential separation method is considered to be advantageous for large-scale separations of many valuable components from egg yolk.