• Journal of the Korean Chemical Society
• /
• v.34 no.2
• /
• pp.203-210
• /
• 1990

As a possible biocompatible and biodegrable polymer skeleton for drug delivery system, block copolymers of L-lactic acid and L-glutamic acid with different composition were synthesized and characterized. Poly (L-lactide) was prepared by polymerization of L-lactide with zine oxide at $130^{\circ}C$ for 72 hrs. 3-Amino-l-propanol was introduced to poly (L-lactide) by an ester linkage in order to initiate polymerization. Polymerization of $\gamma-benzyl-L-glutamate-N-carboxyanhydride(\gamma-BLG-NCA)$ utiliizing the amino group of modified poly (L-lactide) as an initiator gave rise to the block copoly $(L-lactide-\gamma-benzyl-L-glutamate).$ The NMR study of resulting block copolymers showed that the composition of L-lactic acid and $\gamma-benzyl-L-glutamate$ in block copolymers was depended on the weight ratio of poly (L-lactide) and $\gamma-BLG-NCA.$ The thermal properties of the resulting block copolymers were determined by the differential scanning calorimetry and by the thermogravimetry.

• Polymer(Korea)
• /
• v.31 no.3
• /
• pp.228-232
• /
• 2007

This purpose of this study is to enhance the hydrolysis of poly (butylene succinate-co-L-lactate) (PBSL) and poly [(R) -3-hydroxybutylate] (PHB), to develop materials with advanced medical absorbability and environmental suitability. The first method involves increasing the bioabsorbability of poly (glycolic acid) (PGA) in the core of the fibrous complex, while the second method involves making a complex fiber containing PBSL and PHB in the outer layer for improving environmental degradability Improvement in the hydrolysis of PBSL and PHB due to glycolic acid occurs by hydrolytic behavior of PGA. The drawing supporting the resulting PBSL/PGA fiber was executed at $65^{\circ}C$, where the orientation is well arranged in crystal form. Obtaining a PHB/PGA complex fiber in the proper crystal orientation at $50^{\circ}C$ was not possible since the arranged crystal orientation was only identified in drawings from temperatures above $50^{\circ}C$. Also, it is necessary to execute a smooth surface to achieve an on-line drawing since unevenness occurs in the fibrous surface from an in-line drawing.

• Journal of the Korean Chemical Society
• /
• v.41 no.7
• /
• pp.337-342
• /
• 1997

Acryloylmethylbenzo-15-crown-5 was prepared from the reaction of 4'-hydroxymethylbenzo-15-crown-5 with acryloyl chloride. And, poly(acryloylmethylbenzo-15-crown-5) [poly(AMB15C5)] was synthesized by radical polymerization using AIBN as initiator in benzene. Coated wire lead(II) ion-selective electrodes ($Pb^{2+}$-CWISEs) using either poly(AMB15C5) or B15C5 as neutral carrier were prepared, respectively. $Pb^{2+}$-CWISEs gave linear responses with slopes of 28$\pm$ 1mV per decade within the concentration range of $10^{-5} M{\sim}10^{-1}$ M, respectively. Also, the detection limits were $10^{-6}$ M and response times were either 3 or 5 min. for B15C5 and poly(AMB15C5), respectively. $Pb^{2+}$-CWISE base on B15C5 was rather unstable than poly(AMB15C5)'s due to solubility of the B15C5 in water. The selectivity coefficients of a variety of interfering ions such as $Mg^{2+},\; Ca^{2+},\; Co^{2+},\; Ni^{2+},\; Cu^{2+},\; Zn^{2+}$ and $Cd^{2+}$ were small ($10^{-4}{\sim}10^{-5}$), while those of $Na^+$ and $K^+$ were large (0.1∼0.01). In addition, the electrode responses depended upon the pH of test solution and the composition of the membrane. In the range pH 3∼6 of test solution, potentials of Pb2+-CWISEs were hardly changed. The optimal contents of B15C5 and poly(AMB15C5) were 7.7 wt% and 13.1 wt%, respectively.

• Applied Biological Chemistry
• /
• v.34 no.3
• /
• pp.273-278
• /
• 1991

Methanol assimilating bacterium, Pseudomonas sp. ILS-003 was used to investigate the optimum conditions for the production of $poly-{\beta}-hydroxybutyric$ acid from methanol. For PHB production, the optimum initial pH was 6.4 and the optimum temperature was $30^{\circ}C$. Also the optimum methanol concentration was found to be 1.0%(v/v). In the PHB production, $(NH_4)_2SO_4$ was the most effective nitrogen source and the optimum concentration was 0.8 g/l, which was eqivalent to 17.4 in C/N ratio. Also, deficiency of the 2 valence metal ions in the medium had stimulating effect on PHB accumulation. Under the optimum substrate concentration, successive feeding of 0.25%(v/v) methanol was the most effective on PHB production. Under the optimum conditions, 1.94 g/l of PHB and 2.78 g/l of dry biomass were produced in 96 hours, and the yield was 69.8%(w/w).

• Macromolecular Research
• /
• v.16 no.3
• /
• pp.231-237
• /
• 2008

Biodegradable poly($\varepsilon$-caprolactone-co-L-lactide)-b-poly(ethylene glycol) (PCLA-b-PEG) copolymers were synthesized via solution polymerization by varying the feed composition of $\varepsilon$-caprolactone ($\varepsilon$-CL) and L-lactide (LLA) ($\varepsilon$-CL: LLA= 10:0, 7:3, 5:5, 3:7, 0: 10). The feed ratio based on weight is in accordance with the copolymer composition except for the case of $\varepsilon$-CL: LLA=3:7 (C3L7), which was verified by $^1H$-NMR. Two different approaches were used for the exceptional case, which is an extension of the reaction time or the sequential introduction of the monomer. A copolymer composition of $\varepsilon$-CL: LLA=3:7 could be obtained in either case. The chemical microstructure of PCLA-b-PEG was determined using the $^{13}C$-NMR spectra and the effect of the sequential structure on the thermal properties and crystallinity were examined. Despite the same composition ratio of the copolymer, the microstructure can differ according to the reaction conditions.

• Journal of fish pathology
• /
• v.17 no.2
• /
• pp.75-82
• /
• 2004

Interferons are kinds of cytokines that play an important role in antiviral defense mechanisms during viral infection by converting cells to synthesize proteins that inhibit viral replication. In the present study, an antiviral response against Spring viremia of carp virus (SVCV) was developed in common carp, Cyprinus carpio following stimulation with the potent interferon inducer, poly inosinic : cytidylic acid (poly I:C). Poly I:C injected fish showed lower cumulative mortalities against SVCV than untreated fish did. Moreover, in vitro study showed that head kidney leucocytes (HKLs) produced an interferon-like cytokine (ILC) after stimulation with poly I:C. According cytopathic effect reduction (CPER) assay to examine antiviral activity of crude ILC, the capacity of HKLs for ILC production was highest at 1×$10^6$cells/ml and significantly enhanced when treated with 20~50$\mu{g}$/ml of poly I:C. The optimal temperature and concentration of FBS to induce the highest ILC production were $20^\circ{C}$ and 5%, respectively.

• Toxicological Research
• /
• v.8 no.2
• /
• pp.331-342
• /
• 1992

The chicken major histocompatibility complex (MHC), the B complex, is beginning to be analyzed at the DNA level. Inbred lines of chickens have been reported to possess 3~5 MHC class II genes. To further analyzed the molecular structure of the chicken MHC class II genes, cDNA clones coding for chicken MHC class II (B-L) ${\beta}$ chain molecules were isolated from chicken spleen and liver. Tissue-specific transcription of B-L ${\beta}$genes was studied by Northern blot analysis. A high level of expression was detected for spleen poly(A)$^+$ RNA whereas a faint signal was detected for liver poly(A)$^+$ RNA. Twenty-nine cDNA clones were isolated from the spleen and eight cDNA clones were isolated from the liver. Based on restriction maps, most clones could be clustered into one family of genes. Four cDNA clones were sequenced (S7, S10 and S19 from the spleen and L1, which was identical to S19, from the liver). Complete amino acid sequences of B-L ${\beta}$ chain molecules were predicated from the nucleotide sequences of the cDNA clones. Although both the nature and the location of the conserved residues were similar in chicken and mammalian sequences, some species-specific differences were found, suggesting that the structures of the B-L molecules are similar, but not identical to their mammalian counterparts.

• Applied Chemistry for Engineering
• /
• v.10 no.1
• /
• pp.129-134
• /
• 1999

This study is related to the investigation of the direct incorporation of $CO_2$ to polymer using quaternary ammonium salt catalysts. Quaternary ammonium salts showed good catalytic activity of $CO_2$ fixation in the synthesis of poly[(1,3-dioxolane-2-oxo-4-yl)methyl methacrylate] [poly(DOMA)] by the direct incorporation of $CO_2$ to poly(glycidyl methacrylate)[poly(GMA)]. Among the salts tested, the ones with higher alkyl chain length and with more nucleophilic counter anion showed higher catalytic activity. The yield of carbon dioxide addition increased with the reaction temperature. Kinetic study was carried out by measuring the variation of $CO_2$, pressure in a high pressure batch reactor. The reaction rate was first order to the concentration of poly(GMA) and $CO_2$, respectively. The rate constant was $0.69L/mol{\cdot}h$ and Henry's constant of $CO_2$ in DMSO at $80^{\circ}C$ was $6.8{\times}10^{-4}mol/L{\cdot}KPa$.

• Proceedings of the KIEE Conference
• /
• 1992.07b
• /
• pp.801-802
• /
• 1992

Poly Si TFTs have been fabricated from low temperature annealed a-Si films. I-V and C-V characteristics in the off-state region were measured. Analytical model for the leakage current in the off-state was suggested. In the measurement, capacitance increased abruptly with Increasing gate and drain voltage. This phenomena is attributed to the leakage current.

• 한국생물공학회:학술대회논문집
• /
• 2000.04a
• /
• pp.523-526
• /
• 2000

A novel cell surface display system was developed by employing the Escherichia coli outer membrane protein C (OmpC) as an anchoring motif. Poly-histidine (poly-His) peptides of 19, 32, 45, 84, and 162 amino acids (aa) could be successfully displayed by inserting them into the seventh exposed loop(L7) of OmpC. Recombinant cells displaying poly-His of 19, 32, 45, and 84 aa could absorb 18.9, 23.9, 26.1, and 32.0 ${\mu}mol$ of $Cd^{2+}$ per gram cell dry weight, respectively and therefore, would be useful as the biosorbents of heavy metals.