• International Journal of Industrial Entomology and Biomaterials
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• v.21 no.1
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• pp.145-150
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• 2010

The regenerated silk fibroin with various molecular weights (MW) was prepared by different dissolution condition and the effect of coagulant on the wet spinnability of the various MW silk fibroin solutions dissolved in formic acid was investigated by the observation of wet spun filament in coagulant and the measurement of maximum draw ratio. The observation on the wet spun filament in coagulation bath revealed that good fibers without bead were formed in a high MW and a very high MW silk fibroin samples. In contrast, beads were observed in the silk fibroin sample with medium MW. The maximum draw ratio of wet spun silk fibroin filament decreased with MW reduction. The decrease of maximum draw ratio in isopropanol, acetone, DMF and THF was remarkably higher than that in methanol and ethanol, indicating that the coagulant type strongly influenced the wet spinnability. The two simple evaluation methods used in this study showed complementary information for wet spinnability: (a) The observation of filament in coagulant was effective to check a continuous fiber formation and a bead formation, and (b) the maximum draw ratio measurement was useful to examine the post drawing ability related to molecular orientation.

• ALGAE
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• v.21 no.2
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• pp.261-266
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• 2006

The innate soluble polysaccharides and phenolic compounds of marine macroalgae are serious contaminants which interfere with experimental procedures such as restriction enzyme digestion, polymerase chain reaction (PCR) and other enzymatic reactions using extracted DNA samples. The viscous polysaccharides are co-precipitated with DNA samples by isopropanol or ethanol precipitation in conventional experiment. To overcome the problem, a method for the isolation of high molecular weight DNA from Porphyra tenera is developed with the application of diatomaceous earth column. The isolated DNAs by this method were about 50-100 kb in size and could be digested well with restriction enzymes. The nuclease activity seemed to be minimal, and high reproducibility in the arbitrary primed PCR for RAPD analyses was a distinctive feature. These results suggest that this method is very efficient in isolating nucleic acid from macroalgae including Porphyra.

• Bulletin of the Korean Chemical Society
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• v.29 no.8
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• pp.1554-1560
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• 2008

The probe diffusion and friction constants of methyl yellow (MY) in liquid n-alkanes of increasing chain length were calculated by equilibrium molecular dynamics (MD) simulations at temperatures of 318, 418, 518 and 618 K. Lennard-Jones particles with masses of 225 and 114 g/mol are modeled for MY. We observed that the diffusion constant of the probe molecule follows a power law dependence on the molecular weight of nalkanes, DMY${\sim}M^{-\gamma}$ well. As the molecular weight of n-alkanes increases, the exponent $\gamma$ shows sharp transitions near n-dotriacontane ($C_{32}$) for the large probe molecule (MY2) at low temperatures of 318 and 418 K. For the small probe molecule (MY1) $D_{MY1}$ in $C_{12}$ to C80 at all the temperatures are always larger than Dself of n-alkanes and longer chain n-alkanes offer a reduced friction relative to the shorter chain n-alkanes, but this reduction in the microscopic friction for MY1 is not large enough to cause a transition in the power law exponent in the log-log plot of DMY1 vs M of n-alkane. For the large probe molecule (MY2) at high temperatures, the situation is very similar to that for MY1. At low temperatures and at low molecular weights of n-alkanes, $D_{MY2}$ are smaller than $D_{self}$ of n-alkanes due to the relatively large molecular size of MY2, and MY2 experiences the full shear viscosity of the medium. As the molecular weight of n-alkane increases, $D_{self}$ of n-alkanes decreases much faster than $D_{MY2}$ and at the higher molecular weights of n-alkane, MY2 diffuses faster than the solvent fluctuations. Therefore there is a large reduction of friction in longer chains compared to the shorter chains, which enhances the diffusion of MY2. The calculated friction constants of MY1 and MY2 in liquid n-alkanes supported these observations. We deem that this is the origin of the so-called“solventoligomer”transition.

• Polymer(Korea)
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• v.24 no.4
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• pp.469-476
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• 2000

The miscibility between acrylic copolymers and tackifier resins influenced on adhesion properties of PSA. PSA with high molecular weight and narrow molecular weight distribution of acrylic copolymers showed systemical modification of adhesion properties of PSA by tackifier resins only in case of miscible system. It is concluded that the investigation of the miscibility between two Components is very important to adhesion properties of PSA.

• KSTLE International Journal
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• v.2 no.1
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• pp.55-58
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• 2001

The most widely-used orthopaedic grade polymer bearing liner material, ultrahigh molecular weight polyethylene (UHMWPE), for the total joint arthroplasty degrades after gamma-irradiation sterilization through the progressive oxidation in a shelf and in vivo. Oxidative degradation makes UHMWPE brittle and leads to decrease in mechanical properties. In this study the relationship between post-gamma-irradiation aging time and wear of UHMWPE was investigated. Six retrieved polyethylene hip liners implanted for 3-16 years and then stored in air for 1.5-6.5 years until tests were used. Two types of pin-on-disk wear testing were conducted by the uni-directional repeat pass rotating and by the linear reciprocating stainless steel disks against stationary polyethylene pins under 4Mpa at 1Hz with bovine serum lubrication in ambient environment. Wear of retrieved polyethylene hip liners does not have direct correlation with in vivo or total aging time. Linear reciprocal sliding motion generated more remarkable wear than uni-directional repeat pass sliding motion. It indicates that kinematic motion affects very crucially on the wear of aged UHMWPE having brittle white band region.

• Membrane and Water Treatment
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• v.4 no.3
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• pp.203-214
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• 2013

Laboratory tests were performed to determine the efficiency of dye solution desalination by electrodialysis. The study involved anionic dye and mineral salt recovery by obtaining two streams from a salt and dye mixture - dye-rich solution and salt solution. A standard anion-exchange and cation-exchange membranes or monovalent selective anion-exchange membranes were used in the ED stack. It was found that the separation efficiency was strongly dependent on the dye molecular weight. The best results for standard ion-exchange membranes were achieved for the desalination of Direct Black solution. Furthermore, the obtained results implied that the application of monovalent selective anion-exchange membranes improved the recovery of dye and salt solutions - the dye concentration in the diluate remained constant irrespective of the molecular weight of anionic dyes, whereas the salt recovery remained very high (99.5%).

• Journal of Sericultural and Entomological Science
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• v.42 no.2
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• pp.104-108
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• 2000

To hydrolyze insolule sericin the enzyme hydrolysis was used, and then obtained the results as given belows. When insoluble sericin was hydrolyzed by enzyme treatment, the solubility was best at pH 7, 60$\^{C}$ and was slightly increased both above 2 hours treatment and above 10% of enzyme concentration. As the results of electrophoresis, the distribution of molecular weight of sericin powder obtained by enzyme hydrolysis was very weak and showed in the wide range having no distinguishable band. Average degree of polymerzations (A.D.P.) of sericin hydrolyzed by enzyme were about 4.1∼6.3, average molecular weight were about 470∼730. The whiteness of the sericin powder obtained by enzyme hydrolysis was high and increased slightly with higher treatment concentration of enzyme. As the results of amino acid analysis, the amino acid analysis, the amino acid composition of the sericin powder from the enzyme treatment were similar to which located at near 230$\^{C}$ and 320$\^{C}$. The peak of near 230$\^{C}$ could not been found in the sericin powder obtained by enzyme hydrolysis.

• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.3
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• pp.326-333
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• 1984

The oxidation rate of krill lipids is very slow and no peroxides are accumulated even after long storage. By means of various chromatographic techniques and mass spectrophotometry, the primary antioxidant has been identified as ${\alpha}$-tocopherol. The phospholipid fractions did not show any antioxidative activity but peroxide-decomposing properties of total lipids depended upon the phospholipid contents. The peroxide-decomposing activities of phospholipids were due to the presence of polar materials generated during the storage. The most peroxide-decomposing fractions of oxidized krill lecithin by DEAE-cellulose column chromatography was low-molecule fraction (mean molecular weight: 182) and high-molecule fraction (mean molecular weight: 1942) was the next. The separation of peroxide-decomposing properties from low-molecule fraction was achieved by partitioning between chloroform and methanol/water. The methanol/water fraction showed strong peroxide-decomposing activities and main component of this fraction was assumed hydroxyamine compounds derived from choline.

• Bulletin of the Korean Chemical Society
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• v.18 no.12
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• pp.1264-1268
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• 1997

The poly(methylsilene) (1) was modified with the group 4 metallocene Cp2MCl2/Red-Al (M = Ti, Zr, Hf) combination catalyst and with the group 6 metal carbonyl M(CO)6 (M = Cr, Mo, W) catalyst, producing the highly cross-linked isoluble polymer and the lowly cross-linked soluble polymer, respectively. An interrelationship between molecular weight and percent ceramic residue yield with metal within the respective group was not found. The polymers modified with the group 4 metallocene combination catalysts have higher molecular weight and lower percent ceramic residue yield than the polymers modified with the group 6 metal carbonyl catalysts do. The catalytic activity of group 4 metallocene combinations appears to be higher at ∼100 ℃, but to be lower at very high temperature than those of group 6 metal carbonyls. The pyrolysis of the modified 1 yielded SiC ceramic.

• Journal of Microbiology and Biotechnology
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• v.7 no.2
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• pp.132-137
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• 1997

A novel protein (HEAAE, High Essential Amino Acid Encoding Protein), rich in essential amino acids ($75{\%}$ of total), was designed and constructed in our laboratory. The designed peptides were analyzed by SYBLE and stable secondary and tertiary structures were predicted. The monomeric form (HEAAE-1) of the protein consists of 20 amino acid residues with four additional amino acids comprising a potential ${\beta}$-turn (HEAAE-4). Size exclusion analysis demonstrated that the monomer is self-aggregates in aqueous solution to form higher ordered multimeric structures, which are very reminiscent of natural plant storage proteins. The DNA encoding this amino acid sequence was synthesized, and from this monomeric gene fragment (heaae-1), the stable tetrameric form of the gene (heaae-4) was generated by subcloning into the E. coli expression vector pKK223-3. A clear 6 kDa polypeptide band corresponding to the molecular weight of the dimeric form (HEAAE-2) was detected. The smeared band which appeared around the molecular weight corresponding to HEAAE-4 of 11 kDa suggested that the tetramer form of this protein might be processed into smaller size products.