• International Journal of Industrial Entomology and Biomaterials
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• 제38권2호
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• pp.51-55
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• 2019

The structure and properties of silk polymers (fibroin and sericin) can be satisfactorily controlled by choosing a suitable silkworm variety and, hence, this parameter (i.e., silkworm variety) has attracted increasing attention. A previous study reported that the crystallinity of white colored silkworm cocoons depends on the silkworm variety. In the present study, sixteen yellow colored silkworm variety cocoons were produced and their molecular conformation and crystallinity were investigated. The conformation of the silkworm cocoons varied with the silkworm variety. Most cocoons exhibited ${\beta}$-sheet conformation, although random coil and ${\beta}$-sheet conformations co-existed in some cocoons (e.g., 21 and D90). The crystallinity of the silkworm cocoons varied with the silkworm variety and the measurement position of the cocoon (i.e., outer surface or inner surface). However, the difference in the crystallinity indices of the outer and inner surfaces comprising the cocoons varied with the silkworm variety, but was <2% for all cocoons, except for MAL.

• International Journal of Industrial Entomology and Biomaterials
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• 제33권2호
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• pp.144-148
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• 2016

Recently, silk sericin has been studied extensively for biomedical and cosmetic applications because of its unique properties, including UV resistance and wound healing ability. For use in applications, sericin is fabricated in various forms including films and gels. However, the mechanical properties of sericin are too weak. In this basic study on improving the mechanical properties of sericin, a silk sericin aqueous solution was separated into two layers by centrifugation. The solution viscosity, molecular conformation, and mechanical properties of each separation layer of the sericin were examined. Sericin from the lower layer had a higher solution viscosity and film mechanical properties (strength and strain) than that from the upper layer, implying that sericin from the lower layer had a higher molecular weight than that from the upper layer. The molecular conformation of the sericin films varied depending on the casting solvent. In aqueous solution, the sericin film from the lower layer showed a ${\beta}$-sheet conformation, whereas that from the upper layer displayed a random coil conformation. All the sericin films showed a highly ${\beta}$-sheet-crystallized state when cast in formic acid, regardless of the separation layer.

• 한국잠사곤충학회지
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• 제42권1호
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• pp.42-47
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• 2000

Structural and thermal characteristics of silk fibroin/poly(2-hydroxyethyl methacrylate)(PHEMA) blend films were investigated using FTIR, X-ray diffractometer, differential scanning calorimeter, thermogravimeter and scanning electron microscope. FTIR spectra showed that the conformation of silk fibroin prepared by dissolving in formic acid was $\beta$-sheet, which did not affected by blending with PHEMA. The X-ray diffraction patterns also showed that individual crystalline structure of silk fibroin and PHEMA was not affected for the blend films. The initial thermal decomposition temperature of silk fibroin/PHEMA blend film tends to be higher than either of silk fkbroin or PHEMA. Thermal stability of both polymers, more notably PHEMA, can be improved by blending two components. As a result of SEM observation, the phases separation for silk fibroin/PHEMA blend films occured regardless of blend ratio ; continuous and dispersed phase were silk fibroin and PHEMA component, respectively.

• Bulletin of the Korean Chemical Society
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• 제25권6호
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• pp.838-842
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• 2004

Amyloid peptide (A${\beta}$) is the major component of senile plaques found in the brain of patient of Alzheimer's disease. ${\beta}$-amyloid peptide (25-35) (A${\beta}$25-35) is biologically active fragment of A${\beta}$. The three-dimensional structure of A${\beta}$25-35 in aqueous solution with 50% (vol/vol) TFE determined by NMR spectroscopy previously adopts an ${\alpha}$-helical conformation from $Ala^{30}$ to $Met^{35}$. It has been proposed that A${\beta}$(25-35) exhibits pH- and concentration-dependent ${\alpha}-helix{\leftrightarrow}{\beta}$sheet transition. This conformational transition with concomitant peptide aggregation is a possible mechanism of plaque formation. Here, in order to gain more insight into the mechanism of ${\alpha}$-helix formation of A${\beta}$25-35 peptide by TFE, which particularly stabilizes ${\alpha}$-helical conformation, we studied the secondary-structural elements of A${\beta}$25-35 peptide by molecular dynamics simulations. Secondary structural elements determined from NMR spectroscopy in aqueous TFE solution are preserved during the MD simulation. TFE/water mixed solvent has reduced capacity for forming hydrogen bond to the peptide compared to pure water solvent. TFE allows A${\beta}$25-35 to form bifurcated hydrogen bonds to TFE as well as to residues in peptide itself. MD simulation in this study supports the notion that TFE can act as an ${\alpha}$-helical structure forming solvent.

• International Journal of Industrial Entomology and Biomaterials
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• 제26권2호
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• pp.113-118
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• 2013

In this study, silk sericin films were prepared using different extraction methods, and the molecular conformation of sericin was examined using Fourier-transform infrared spectroscopy with attenuated total reflection geometry. Additionally, the effect of the film side (air-facing side or plate-facing side) on the molecular conformation of the sericin films was investigated. Interestingly, the molecular conformation of the sericin film depended on the film side. The molecular conformation of air-facing side of the sericin film was significantly influenced by extraction solution and time. The ${\beta}$-sheet crystallization and the crystallinity index of the sericin film markedly increased with an increase in the extraction time in hot water. The order of the crystallinity indices for the sericin films obtained with different extraction solutions was as follows: citric acid solution > urea solution >> hot water. In contrast, no remarkable differences were observed in the molecular conformation of the plate-facing side of the sericin film after extraction in hot water for different time periods. Urea and citric acid solution extractions showed remarkably higher crystallinity indices for sericin than those obtained after hot water extraction. However, no significant differences were observed in the crystallinity index of sericin between urea and citric acid solution extraction in plate-facing side of the film.

• 한국잠사곤충학회지
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• 제41권1호
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• pp.54-60
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• 1999

염산 또는 수산화나트륨 수용액의 농도, 온도, 시간 등 처리조건에 따른 작잠견사의 가수분해율을 측정하였으며 산처리 작잠분말과 알칼리처리 작잠분말의 형태 및 구조특성을 주사전자현미경, 적외선 분광분석, X-선 회절분석 등의 방법으로 분석한 결과 다음과 같은 결과를 얻었다. 1. 작잠견사에 대한 염산 및 수산화나트륨의 처리농도와 온도가 높을수록 또한 처리시간이 길어질수록 작잠견사의 가수분해율은 증가하는 경향을 나타내었으나 고온, 고농도의 조건하에서 수산화나트륨을 작잠견사에 처리하는 경우 작잠견사의 가수분해율이 오히려 떨어지는 경향을 보였다. 2. 산 및 알칼리 처리에 의하여 제조된 작잠분말의 형태는 용해도가 30 wt% 부근에서는 섬유상의 형태를 유지하였으며 산처리 분말의 경우 용해도가 증가함에 따라 섬유축 방향으로 조각난 미세한 입자형태를 나타내었으나 알칼리처리 분말의 경우에는 부정형의 입자형태를 나타내었다. 3. 적외선 분광분석 결과 작잠분말은 처리조건과 무관하게 ${\beta}$-sheet 구조의 특성을 반영하는 1635, 1532, 1226, 960, 700 cm$^{-1}$ 흡수대와 ${\alpha}$-helix 구조의 특성을 반영하는 616 cm$^{-1}$ 흡수대가 뚜렷하게 나타나 작잠분말의 주요 conformation은 ${\beta}$-sheet 구조와 ${\alpha}$-helix 구조임을 확인하였다. 4. X-선 회절분석 결과 가수분해율이 낮을 경우 (35 wt%)에는 ${\beta}$-sheet 구조와 ${\alpha}$-helix 구조에 기인하는 회절 피크가 뚜렷하게 나타났으나 가수분해율이 80 wt% 이상으로 증가하면 2${\theta}$=17.1$^{\circ}$ 및 20.0$^{\circ}$의 회절피크만 강하게 나타났다.

• 한국잠사곤충학회지
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• 제44권2호
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• pp.87-92
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• 2002

염화아연에 의한 작잠 견사의 용해 조건을 살펴본 후 투석법에 의하여 얻은 작잠 견피브로인 분말의 형태와 적외선 분광 특성 및 X-선 회절 특성을 살펴본 결과 다음과 같은 결론을 얻었다. 1. 작잠 견사는 고농도의 염화아연 수용액에 용해되었으나 용해 조건을 조절하여 완전하게 작잠 견사를 용해할 수 있었다. 2. 재생 작잠 분말의 구조 특성을 살펴보기 위하여 적외선 분광분석과 X-선 회절분석을 행한 결과 작잠분말은 $\beta$-sheet 구조와 $\alpha$-helix 구조로 이루어져 있었다. 3. 염화아연을 사용하여 제조한 작잠 견피브로인 용액으로부터 순수한 작잠 견피브로인을 얻기 위한 새로운 방법이 개발되어야 함을 알 수 있었다.

• 한국잠사곤충학회지
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• 제53권2호
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• pp.118-123
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• 2015

알코올의 농도 변화에 따른 실크단백질의 구조전이 효과에 대하여 살펴보기 위하여 백옥잠 누에고치를 이용하여 실크단백질 용액을 제조하였다. 알코올의 농도를 100%, 70%, 50%로 조절하여 제조한 실크 비드의 적외선 분광 분석을 하였다. 고농도(100%) 알코올로 처리한 실크단백질은 전형적인 ${\beta}-sheet$ 구조를 반영하는 $1265cm^{-1}$ 부근에서 흡수대를 보였으며 모델 약물로 사용한 4HR의 특성 피크는 관찰되지 않았다. 알코올의 농도를 70%, 50%로 조절하여 처리한 경우에는 모델 약물의 흡수대인 $2933cm^{-1}$ 부근, $1069cm^{-1}$ 부근, 그리고 $973cm^{-1}$ 부근의 흡수대가 발현되었다. 이러한 결과는 알코올의 농도에 따라 조성되는 실크단백질의 미세 구조에 차이가 있음을 나타내며, 보다 정밀한 실크단백질 구조 제어를 위한 추가 연구가 필요한 것으로 생각된다.

• 한국잠사곤충학회지
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• 제52권1호
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• pp.10-15
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• 2014

작잠 누에고치를 정련한 후 질산칼슘4수화물의 용융액을 사용하여 재생 작잠 실크피브로인 스펀지를 제조하였다. 작잠 실크피브로인은 280 nm에서 tyrosine 잔기 등에 기인한 흡광대를 나타내었다. 작잠 실크피브로인 스펀지를 에탄올 농도별로 처리한 후 구조 전이를 관찰한 결과 80% 에탄올 처리시에는 ${\beta}$-sheet 구조($700cm^{-1}$), ${\alpha}$-helix 구조($625cm^{-1}$), 그리고 random coil ($660cm^{-1}$) 구조가 공존하는 것으로 나타났다. 또한 작잠 실크피브로인을 이용한 in vitro 상처회복실험 결과 실크피브로인의 첨가에 의하여 상처회복 효과가 인정되었다.

• 한국미생물생명공학회:학술대회논문집
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• 한국미생물생명공학회 2001년도 Proceedings of 2001 International Symposium
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• pp.149-153
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• 2001

To investigate the mode of bactericidal action for antimicrobial peptide, pediocin, synthetic and mutant pediocins were prepared by direct chemical synthesis. Native pediocin was purified from Pedio-coccus acidilactici M and its conformational structure and bactericidal functions were analyzed and compared to synthetic pediocin. Schematic mode of pediocin actions, how pediocin binds on the target cell membrane, penetrates and makes tunnel are proposed. For these purposes, primary and secondary structures of pediocin was analyzed and disulfide bond assignment was also done. The pediocin purified from P. acidilactici M had high effective bactericidal ability against gram positive bacteria, especially Listeria monocytogenes and was very stable at extreme pHs and even at high temperatures such as autoclaving temperature (121$^{\circ}C$). Pediocin was consisted of 44 amino acids with four cysteines. Novel synthetic peptides were achieved by solid phase peptide synthesis(SPPS) method. To explain the function of cysteine in C-terminal region, mutant pediocin, Ped[C24A＋C44A], was synthesized and their structural and biological functions were analyzed. Second mutant pediocin, Ped[KllE], was prepared to explain the function of lysine at 11 of N-terminal part of pediocin, especially loop of $\beta$-sheet, and to predict the initial binding site of pediocin. The native and synthetic pediocins was showed random coil conformation by spectropolarimetry in moderate conditions. This conformation was observed in extreme conditions such as high temperature and low and high pHs, also. Circular dichroism(CD) data also showed the existence of $\beta$-turn structure in N-terminal part both native and synthetic pediocins. A structural model for pediocin predicts that 18 amino acids in the N-terminal part of the peptide assume a three-strand $\beta$-sheet conformation. This random coil in C-terminal part of pediocin was converted to folding structure, helix structure, in nonpolar solvents such as alcohol and TFE. The disulfide bond between $^{9}$ Cys and $^{14}$ Cys was concrete and inevitable, however, evidences of disulfide bond between $^{24}$ Cys and $^{44}$ Cys was not. Data of Ped[C24A＋C44A], pediocin mutant showed that $^{44}$ Cys was required during killing the target cells but not inevitable, since Ped[C24A＋C44A] still have bactericidal activity but much less than native pediocin. Another pediocin mutant, Ped[KllE], had still bactericidal activity, was controversial to propose that positive charge like as $^{11}$ Lys in loop or hinge in bacteriocin bound or helped to binding to microorganism with electrostatic interaction between cell membrane especially teichoic acid and positive amino acid nonspecifically. The conformation of pediocin among native, synthetic and mutant pediocins did not show big difference. The conformations between oxidized and reduced pediocin were almost similar regardless of native or synthetic.