• Carbon letters
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• 제20권
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• pp.26-31
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• 2016

In this study, we report a general method for preparation of a one-dimensional (1D) arrangement of Au nanoparticles on single-walled carbon nanotubes (SWNTs) using biologically programmed peptides as structure-guiding 1D templates. The peptides were designed by the combination of glutamic acid (E), glycine (G), and phenylalanine (F) amino acids; peptides efficiently debundled and exfoliated the SWNTs for stability of the dispersion and guided the growth of the array of Au nanoparticles in a controllable manner. Moreover, we demonstrated the superior ability of 1D nanohybrids as flexible, transparent, and conducting materials. The highly stable dispersion of 1D nanohybrids in aqueous solution enabled the fabrication of flexible, transparent, and conductive nanohybrid films using vacuum filtration, resulting in good optical and electrical properties.

• 한국환경과학회지
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• 제12권1호
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• pp.77-80
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• 2003

The interaction of mastoparan B, a cationic tetradecapeptide amide isolated from the hornet Vespa basalis, with phospholipid bilayers was studied with synthetic mastoparan B and its analogue with Ala instead of hydrophobic 12th amino acid residue in mastoparan B. MP-B and its derivative, [12-Ala]MP-B were synthesized by the solid-phase peptide synthesis method. MP-B and its analogue, [12-Ala]MP-B adopted an unordered structure in buffer solution. In the presence of neutral and acidic liposomes, the peptides took an $\alpha$-helical structure. The two peptides interacted with neutral and acidic lipid bilayers. These results indicated that the hydrophobic face in the amphipathic $\alpha$-helix of MP-B critically affected the biological activity and helical content.

• 한국수산과학회지
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• 제28권6호
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• pp.728-735
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• 1995

The peptidyl prolyl cis-trans isomerase(PPlase, EC 5.2.2.8) from Bacillus stearothermophilus SIC1 was extracted from the cells treated with by lysozyme. PPlase was purified from the cell extracts by heat treatment, ammonium sulfate precipitation, ion exchange chromatography and finally gel filtration (FPLC). The purity of purified the enzyme after Superose 12 column chromatography was examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE). The molecular weight of the purified PPlase was estimated as 18,000 by SDS-PAGE. The 39 amino acid residues from the N-terminus were determined by the protein sequencer. The enzyme showed the optimum pH at 8.0 and was stable at the range of pH 7.0 to 8.0. The enzyme was considerably stable after heat treatment at $60^{\circ}C$ for 30 minutes, and the enzyme was quite stable up to $65^{\circ}C$. The presence of the PPlase in the refolding solution accelerated the isomerization rate of the assay peptide.

• Food Science and Biotechnology
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• 제18권5호
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• pp.1199-1203
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• 2009

Melamine is a chemical intermediate to manufacture amino resins and plastics, which cannot be used as food additive since it can cause kidney stones. A qualitative determination method of melamine residue in powdered and liquid milk was developed using Fourier transform infrared (FTIR) spectroscopic technique. The calibration sets consisted of 21 standard melamine solutions, in which 1% trichloroacetic acid aqueous solution and acetonitrile (3:1, v/v) were used as solvent. The model was validated using 10 standard melamine solutions which were unused to build up the calibration set. Infrared (IR) absorbance peaks specific to almost all chemical groups in melamine molecule were shown in the spectral range between 1,100 and 1,800/cm. Combined partial least squares (PLS)-$2^{nd}$ derivative calibration model coupled with mean centering (MC) mathematical enhancement showed the highest correlation coefficients ($R^2$>0.99). In brief, the FTIR technique can be used for quantitative analysis of melamine in milk samples.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.53-58
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• 2011

Cysteine and histidine-capped water-dispersible ZnS:Mn nanocrystals (ZnS:Mn-Cys and ZnS:Mn-His) were synthesized and their effects on E. coli and human cells were investigated. Particle sizes of these nanocrystals were found from HR-TEM images to be 3.5 nm and 4.0 nm, respectively. Their solution photoluminescence spectra showed identical broad emission peaks at 580 nm. ZnS:Mn-His significantly suppressed the growth of E. coli at $100{\mu}g/mL$ and 1 mg/mL concentrations, something not observed with ZnS:Mn-Cys. Consistent with this, greater inhibition of cell proliferation and viability were observed in HEK293 and IMR90 cells in ZnS:Mn-His at $100{\mu}g/mL$ and 1 mg/mL concentrations.

• Elastomers and Composites
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• 제50권3호
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• pp.175-183
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• 2015

A series of fluorinated aromatic poly(hydroxyamide)s (PHAs) were synthesized by direct polycondensation of diacides containing 2,6-dimethylphenoxy group and quinoxaline ring in the main chain with 2,2-bis-(3-amino-4-hydroxyphenyl) hexafluoropropane. The PHAs had relatively low inherent viscosities in the range of 0.35~0.43 dL/g at $35^{\circ}C$ in DMAc solution. All PHAs exhibited excellent solubility in aprotic solvents such as NMP, DMAc, DMF and DMSO as well as in common organic solvents such as pyridine, THF, and m-cresol at room temperature. However, the poly(benzoxazole)s (PBOs) were quite insoluble in all organic solvents except partially soluble in concentrated sulfuric acid. The PBOs showed glass transition temperatures between 233 and $284^{\circ}C$ by DSC and maximum weight loss temperatures in the range of $536-546^{\circ}C$ by TGA.

• 분석과학
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• 제17권2호
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• pp.180-183
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• 2004

형광광도법을 이용하여 histidine 아미노산을 간단하고미량까지 정확하게 정량 하는 방법을 연구하였다. $Eu^{3+}$ - TTA- histidine 착물의 방출 봉우리는 235 nm에서 들뜰 때 470 nm에서 나타나며 그의 형광세기는 histidine을 $1{\times}10^{-7}-4{\times}10^{-6}M$까지 가함에 따라 직선적으로 증가하였다. 이를 이용하여 histidine을 정량 하는 방법을 연구하였다. 검출 한계는 $5{\times}10^{-7}M$이였으며 이때의 상대표준편차는 3.5%이였다. 이 방법을 합성 시료에서 histidine을 정량 하는데 이용하였다.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.933-938
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• 1997

The interaction of mastoparan B, a tetradecapeptide toxin found in the hornet Vespa basalis, with phospholipid bilayers was investigated. Synthetic mastoparan B and its analogs, obtained by substituting one hydrophilic amino acid (2-Lys, 4-Lys, 5-Ser, 8-Ser, 11-Lys, or 12-Lys) in mastoparan B with Ala, were studied. Mastoparan B and its analogs were synthesized by the solid-phase method. As shown by circular dichroism spectra, mastoparan B and its analogs adopted an unordered structure in buffer solution. All peptides took an α-helical structure, and the α-helical content of its analogs increased in the presence of neutral and acidic liposomes as compared to that of mastoparan B. In the calcein leakage experiment, we observed that mastoparan B interacted more weakly with lipid bilayers in neutral and acidic media than its analogs. Mastoparan B also showed slightly lower antimicrobial activity and hemolytic activity towards human erythrocytes than its analogs. These results indicate that the greater hydrophobicity of the amphiphilic α-helix of mastoparan B by replacement with alamine residues results in the increased biological activity and helical content.

• Korean Chemical Engineering Research
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• 제49권4호
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• pp.475-479
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• 2011

키토산은 천연고분자 물질로 다양한 물리화학적(다중양이온, 반응성 수산화기와 아미노기 그룹), 생물학적(생리활성, 생체적합성, 생분해성) 특성을 가지고 있다. 본 연구에서는 겔형성제로 폴리감마글루탐산을 이용하여 키토산 나노입자를 제조하였다. 나노입자는 폴리감마글루탐산의 카르복실기($-COO^-$)와 키토산의 아미노기($-NH_3^+$)사이의 이온 상호작용에 의해 형성되었다. 키토산(0.1~1 g)을 100 ml 아세트산 용액(1% v/v)에 첨가한 후 상온에서 충분히 용해되도록 하룻밤 동안 교반하였다. 폴리감마글루탐산(0.1 g)은 상온에서 90 ml 증류수에 용해시켰다. 교반되고 있는 폴리감마글루탐산 용액에 키토산 용액을 주사바늘을 통해 상온에서 적가하였다. 입자의 평균 크기는 80~300 nm 범위에서 형성되었다. 키토산/폴리감마글루탐산 나노입자는 중금속 이온들($Cd^{2+}$, $Pb^{2+}$, $Zn^{2+}$, $Cu^{2+}$, $Ni^{2+}$)의 제거를 위해 콜로이드 상태의 흡착 물질로 사용되었다. 나노입자의 중금속 제거 능력은 $Cu^{2+}$ > $Pb^{2+}$ > $Cd^{2+}$ > $Ni^{2+}$ > $Zn^{2+}$의 결과를 보였다.

• 한국식품영양과학회지
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• 제44권5호
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• pp.767-774
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• 2015

완도산 다시마를 천연 염미증강제로 개발하기 위하여 다시마로부터 정미성분이 최적으로 추출되는 열수 추출 조건을 평가하였으며, 다시마 추출분말을 이용하여 염미증강 효능과 나트륨 저감화율을 분석하였다. 정미성분 추출에 가장 적합한 완도산 다시마의 수확시기를 선정하기 위하여 5월, 6월, 7월에 수확한 다시마의 일반성분과 유리아미노산을 분석한 결과 정미성분 아미노산(glutamic acid와 aspartic acid)의 함량이 가장 높은 6월 수확 다시마를 추출 원료로 선정하였다. 다시마 열수 추출 온도와 시간 조건을 평가하기 위하여 $60^{\circ}C$, $80^{\circ}C$, $100^{\circ}C$에서 1시간, 2시간, 3시간을 각각 추출하여 추출액의 품질 특성을 분석한 결과 $100^{\circ}C$ 추출 조건에서 가용성 고형분과 조단백의 함량이 35.47~36.93%와 3.75~4.00%로 가장 높게 나타났으며, 점도는 1.96~2.19 cP로 낮게 나타나 추출 온도는 $100^{\circ}C$를 선정하였다. 추출 시간 선정을 위하여 $100^{\circ}C$에서 추출 시간에 따른 추출액의 정미성분 아미노산 함량과 관능적 특성을 평가한 결과 추출 2시간에서 정미성분 아미노산인 glutamic acid와 aspartic acid의 함량이 각각 275.33 mg%와 121.18 mg%로 가장 높게 나타났으며, 관능적 기호도도 유의적으로 높게 평가되어 다시마로부터 정미성분 추출을 위해 적합한 추출 온도와 시간은 $100^{\circ}C$, 2시간 조건으로 확인되었다. 정미성분이 최적으로 추출된 다시마의 추출분말을 제조하여 NaCl 용액에 첨가한 후 염미증강 효능을 평가한 결과 짠맛 강도 1, 5, 9의 NaCl 용액이 다시마 추출분말 1% 첨가 후 짠맛 강도 4.25, 10.08, 16.58로 상승하였다. 동일한 짠맛 강도에서 NaCl 용액과 다시마 추출분말이 첨가된 시험용액의 나트륨 함량을 측정하여 나트륨 저감화율을 분석한 결과 12.24~24.33%의 저감화율을 나타내었다. 본 연구를 통하여 감칠맛과 정미성분이 풍부한 다시마 추출물은 조미소재뿐만 아니라 식품에서 나트륨 함량을 줄이기 위한 천연 염미증강제로서 산업적 활용을 기대할 수 있다.