• Macromolecular Research
• /
• v.15 no.7
• /
• pp.633-639
• /
• 2007

A variety of NMR techniques were applied to the micro-chemical structural characterization of polyanilines prepared via an efficient synthetic method in a self-stabilized dispersion medium in which the polymerization was conducted in a heterogeneous organic/aqueous biphasic system without any stabilizers. Here, the monomer and growing polymer chain were shown to function simultaneously as a stabilizer, imparting compatibility for the dispersion of the organic phase, and as a form of flexible template in an aqueous reaction medium. Polymerizations predicated on this concept generated polyanilines with a low defect content: solution state $^{13}C-NMR$ and solid $^{13}CDD/CP/MAS$ spectroscopy indicated that the synthesized HCPANi and its soluble derivative, HCPANi-t-BOC, evidenced distinctly different NMR spectra with fewer side peaks, as compared to conventionally prepared PANis, and the complete structural assignments of the observed NMR peaks could be determined via the combination of both 1D and 2D techniques. Ortho-linked defects in HCPANi were estimated to be as low as 7%, as shown by a comparison of the integration of the carbonyl carbon resonance peaks.

• Journal of the Korean Chemical Society
• /
• v.35 no.3
• /
• pp.258-261
• /
• 1991

Four thiazolidines and following five new compounds were prepared by the addition reaction of cysteine and thiophenol to ${\alpha}$,N-diphenylnitrones, respectively ; ${\alpha}$,thiophenoxy-benzylidene aniline ;${\alpha}$,thiophenoxy-p-hydroxybenzylidene aniline ; ${\alpha}$,thiophenoxy-p-chlorobenzylidene aniline ;${\alpha}$,thiophenoxy-p-methoxybenzylidene aniline ; ${\alpha}$,thiophenoxy-p-nitrobenzylidene aniline. The structure of these compounds were confirmed by the elemental analysis, UV-, IR-and NMR-spectra.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.8
• /
• pp.1839-1844
• /
• 2009

A 20-residue hybrid peptide CA(1-8)-MA(1-12) (CAMA) incorporating residues 1-8 of cecropin A (CA) and residues 1-12 of magainin 2 (MA) has high antimicrobial activity without toxicity. To investigate the effects of the total positive charges of CAMA on the antibacterial activity and toxicity, a hybrid peptide analogue (CAMA-syn) was designed with substitutions of $Ile^{10}\;and\;Ser^{16}$ with Lys. According to CD spectra, structure of CAMA-syn with increase of cationicity was very similar to that of CAMA in DPC micelle. CAMA-syn showed antimicrobial activity similar with CAMA while CAMA-syn has no hemolytic activity and much lower cytotoxicity against RAW 264.7 macrophage cells than CAMA. Also, CAMA and CAMA-syn significantly inhibited NO production by LPSstimulated RAW264.7 macrophage at 10.0∼20.0 $\mu$M. CAMA-syn displayed salt resistance on antimicrobial activity against Escherichia coli at the physiological concentrations of $CaCl_2\;and\;MgCl_2$. The combination studies of peptides and antibiotics showed that CAMA-syn has synergistic effects with synthetic compound and flavonoid against Enterococcus faecalis and VREF. CAMA-syn can be a good candidate for the development of new antibiotics with potent antibacterial and synergistic activity but without cytotoxicity.

• BMB Reports
• /
• v.29 no.6
• /
• pp.545-548
• /
• 1996

CA(1-8)ME(1-12), the CA-ME hybrid peptide of the amino terminal segments of cecropin A (CA) and melittin (ME), has been reported to have a broad spectrum and improved potency without a hemolytic property. In order to obtain new synthetic peptides with powerful antibacterial activity without hemolytic activity, several hybrid peptides were designed from the sequences of CA, ME, magainin 2, bombinin and lactoferricin. All hybrid peptides were constructed to form an amphipathically basic-flexible-hydrophobic structure and synthesized by the solid phase method. Their hemolytic activities against human red blood cells and antibacterial activities against both Gram-positive and Gram-negative bacteria were detennined. CA(1-8)MA(1-12), CA(1-8)BO(1-12), MA(10-17)ME(1-12) and LF(20-29)ME(1-12) showed comparable activities with broad spectra against both Gram-positive and Gram-negative bacteria relative to CA(1-8)ME(1-12) but without hemolytic properties. These hybrid peptides, therefore, could be useful as model peptides to design a novel peptide with improved antibacterial activity and study on structure-activity relationships of antimicrobial peptides.

• Nuclear Engineering and Technology
• /
• v.49 no.4
• /
• pp.825-837
• /
• 2017

Due to the severe impacts of recent earthquakes, the use of seismic isolation is paramount for the safety of nuclear structures. The diversity observed in seismic events demands ongoing research to analyze the devastating attributes involved, and hence to enhance the sustainability of base-isolated nuclear power plants. This study reports the seismic performance of a seismically-isolated nuclear reactor containment building (NRCB) under strong short-period ground motions (SPGMs) and long-period ground motions (LPGMs). The United States Nuclear Regulatory Commission-based design response spectrum for the seismic design of nuclear power plants is stipulated as the reference spectrum for ground motion selection. Within the period range(s) of interest, the spectral matching of selected records with the target spectrum is ensured using the spectral-compatibility approach. NRC-compliant SPGMs and LPGMs from the mega-thrust Tohoku earthquake are used to obtain the structural response of the base-isolated NRCB. To account for the lack of earthquakes in low-to-moderate seismicity zones and the gap in the artificial synthesis of long-period records, wavelet-decomposition based autoregressive moving average modeling for artificial generation of real ground motions is performed. Based on analysis results from real and simulated SPGMs versus LPGMs, the performance of NRCBs is discussed with suggestions for future research and seismic provisions.

• Microbiology and Biotechnology Letters
• /
• v.24 no.5
• /
• pp.546-552
• /
• 1996

The applicability of chitosan, a biodegradable natural polymer, as the coating material to prevent the dispersal of the spores of the apple white rot agent Botryosphaeria dothidea, was investigated. The physical properties of mixed chitosan/polyvinyl alcohol(PVA) film showed the increased physical properties for film formation, such as tensil strength, elongation, and viscosity, compared to either chitosan or PVA film. The FT-IR spectra of chitosan/PVA film indicated that the film was formed by simple blending not by any new synthetic bond. The chitosan and chitosan/PVA film showed effective antifungal activity on B. dothidea. The formed films were well decomposed by ASTM strains used for biodegradability test, on the other hand, the PVA film could not be decomposed by above standard strains. The field test at apple orchard showed that the dispersal of B. dothidea spores could be effectively reduced by coated film, especially by chitosan/PVA film. The spore dispersal was reduced upto 97.0% by 1.0% chitosan/5.0% PVA film during 4 months.

• 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 Environmental Science International
• /
• v.29 no.12
• /
• pp.1171-1184
• /
• 2020

The green synthesis of inorganic nanoparticles (NPs) using biomaterials has garnered considerable attention in recent years because of its eco-friendly, non-toxic, simple, and low-cost nature. In this study, we synthesized NPs of noble metals, such as Ag and Au using an aqueous extract of a marine seaweed, Ecklonia cava. The formation of AgNPs and AuNPs was confirmed by the presence of surface plasmon resonance peaks in UV-Vis absorption spectra at approximately 430 and 530 nm, respectively. Various properties of the NPs were evaluated using characterization techniques, such as dynamic light scattering, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. Phytochemicals in the seaweed extract, such as phlorotannins, acted as both reducing and stabilizing agents for the growth of the NPs. The green-synthesized AgNPs and AuNPs were found to exhibit high catalytic activity for the decomposition of organic dyes, including azo dyes, methylene blue, rhodamine B, and methyl orange.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.20 no.4
• /
• pp.399-410
• /
• 2022

The solubility and species distribution of radionuclides in groundwater are essential data for the safety assessment of deep underground spent nuclear fuel (SNF) disposal systems. Americium is a major radionuclide responsible for the long-term radiotoxicity of SNF. In this study, the solubility of americium compounds was evaluated in synthetic groundwater (SynDB3), simulating groundwater from the DB3 site of the KAERI Underground Research Tunnel. Geochemical modeling was performed using the ThermoChimie_11a thermochemical database. Concentration of dissolved Am(III) in Syn-DB3 in the pH range of 6.4-10.5 was experimentally measured under over-saturation conditions by liquid scintillation counting over 70 d. The absorption spectra recorded for the same period suggest that Am(III) colloidal particles formed initially followed by rapid precipitation within 2 d. In the pH range of 7.5-10.5, the concentration of dissolved Am(III) converged to approximately 2×10^-7 M over 70 d, which is comparable to that of the amorphous AmCO₃OH(am) according to the modeling results. As the samples were aged for 70 d, a slow equilibrium process occurred between the solid and solution phases. There was no indication of transformation of the amorphous phase into the crystalline phase during the observation period.

• Journal of the Korean Chemical Society
• /
• v.44 no.1
• /
• pp.45-51
• /
• 2000

The binding mode of anthryl derivatives to synthetic polynucleotides were investigated by various spectroscopic methods. The spectroscopic properties of anthracence with metbylamine and methylethylenediamine side chains, complexed with $poly[d(A-T)_2]$ and $poly[d(G-C)_2]$, can be summarized as a red-shift, with a strong hypochromism in the absortion spectrum, similar induced CD spectra, and a strong negative LD spectrum with an $LD^r$ magnitude comparable to the DNA absorption region. These observations indicate that anthracene moiety is intercalated between the nucleo-bases of $poly[d(A-T)_2]$ and $poly[d(G-C)_2]$. The side chains did not alter the spectroscopic properties, demonstrating that the binding mode was not affected by them. A strong energy transfer was observed from poly[d(A-T),] and $poly[d(I-C)_2]$ but not from $poly[d(G-C)_2]$, as reported by Kumar et al. (J. Am. Chem. Soc.(1993) 115, 8547). Since the binding mode is the same for all the polynucleotides, the amine group of the guanine base, which protrudes into the minor groove of $poly[d(G-C)_2]$, is concluded to disrupt the energy transfer.