• Applied Chemistry for Engineering
• /
• v.16 no.6
• /
• pp.834-841
• /
• 2005

Polyethylene glycol esters (PEG-esters) were synthesized by condensation reaction of dicarboxylic acid such as adipic acid and sebacic acid and several PEGs. The PEG-esters were analyzed by FT-IR, $^1H-NMR$ and HPLC for structure analysis, and by GPC for molecular weight. Through the analysis of surface tension, critical micelle concentration (CMC), aluminum contact angle of water solution containing the PEG-ester, the synthetic PEG-esters are proven to exhibit surfactant properties. The surface tension ranged from 45 to 50 dyn/cm depended on the concentration and structures of the PEG-esters. The surface tension of PEG-esters with sebacic acid moiety and short polyoxyethylene unit resulted in lower value than that of PEG-ester with adipic acid moiety and long polyoxyethylene unit. The CMC of water solution containing 2.5 wt% PEG-ester with sebacic acid moiety estimated at $0.9{\times}10^{-5}{\sim}5.3{\times}10^{-3}mol/L$ depended on the structures of PEG-esters. The CMC of PEG-esters with long polyoxyethlene unit showed a higher value than that of PEG-esters with short polyoxyethylene unit. Meanwhile, the CMC of PEG-esters with adipic acid moiety was not distinct due to their high hydrophilic character. As the results of contact angle and cutting time aginst aluminum, the contact angle ranged from $45^{\circ}$ to $53^{\circ}$ depended on the concentration of PEG-esters. The cutting time of aluminum showed the shortest value at CMC, but the longest value above CMC. This fact indicates that the CMC of PEG-esters is a very important factor in drilling aluminum.

• Applied Chemistry for Engineering
• /
• v.25 no.1
• /
• pp.90-95
• /
• 2014

Nylon66 extrudates as a function of the extrusion number were prepared by a twin screw extruder. Chemical structures, thermal properties, melt index, crystal structures, mechanical properties such as the tensile strength, elongation at break and impact strength, and rheological property were measured by FT-IR, $^1H$-NMR, melt indexer, DSC, TGA, XRD, universal tensile tester, Izod impact tester, and rheometer. FT-IR and $^1H$-NMR characterizations indicated that the number of extrusions did not affect the chemical structure. The decrease in the molecular weight was checked by the melt index of extrudates. There were no effects of the thermal history on the melting and degradation temperature. The tensile and impact strength and modulus were found to be similar, regardless of the number of extrusions, but the elongation decreased significantly. The complex viscosity of extrudates at low frequencies decreased with the extrusion number. No structural changes after extrusion were confirmed from the fact that there was no change in the slope and shape of G'-G" plot.

• Macromolecular Research
• /
• v.12 no.6
• /
• pp.573-580
• /
• 2004

To prepare chitosan-based polymeric amphiphiles that can form nanosized core-shell structures (nanopar­ticles) in aqueous milieu, chitosan oligosaccharides (COSs) were modified chemically with hydrophobic cholesterol groups. The physicochemical properties of the hydrophobized COSs (COSCs) were investigated by using dynamic light scattering and fluorescence spectroscopy. The feasibility of applying the COSCs to biomedical applications was investigated by introducing them into a gene delivery system. The COSCs formed nanosized self-aggregates in aqueous environments. Furthermore, the physicochemical properties of the COSC nanoparticles were closely related to the molecular weights of the COSs and the number of hydrophobic groups per COS chain. The critical aggregation concentration values decreased upon increasing the hydrophobicity of the COSCs. The COSCs effi­ciently condensed plasmid DNA into nanosized ion-complexes, in contrast to the effect of the unmodified COSs. An investigation of gene condensation, performed using a gel retardation assay, revealed that $COS6(M_n=6,040 Da)$ containing $5\%$ of cholesteryl chloroformate (COS6C5) formed a stable DNA complex at a COS6C5/DNA weight ratio of 2. In contrast, COS6, the unmodified COS, failed to form a stable COS/DNA complex even at an elevated weight ratio of 8. Furthermore, the COS6C5/DNA complex enhanced the in vitro transfection efficiency on Human embryonic kidney 293 cells by over 100 and 3 times those of COS6 and poly(L-lysine), respectively. Therefore, hydrophobized chitosan oligosaccharide can be considered as an efficient gene carrier for gene delivery systems.

• Molecules and Cells
• /
• v.20 no.1
• /
• pp.1-16
• /
• 2005

The peptidyl transferase center (PTC) is located in a protein free environment, thus confirming that the ribosome is a ribozyme. This arched void has dimensions suitable for accommodating the 3'ends of the A-and the P-site tRNAs, and is situated within a universal sizable symmetry-related region that connects all ribosomal functional centers involved in amino-acid polymerization. The linkage between the elaborate PTC architecture and the A-site tRNA position revealed that the A-to P-site passage of the tRNA 3'end is performed by a rotatory motion, which leads to stereochemistry suitable for peptide bond formation and for substrate mediated catalysis, thus suggesting that the PTC evolved by genefusion. Adjacent to the PTC is the entrance of the protein exit tunnel, shown to play active roles in sequence-specific gating of nascent chains and in responding to cellular signals. This tunnel also provides a site that may be exploited for local co-translational folding and seems to assist in nascent chain trafficking into the hydrophobic space formed by the first bacterial chaperone, the trigger factor. Many antibiotics target ribosomes. Although the ribosome is highly conserved, subtle sequence and/or conformational variations enable drug selectivity, thus facilitating clinical usage. Comparisons of high-resolution structures of complexes of antibiotics bound to ribosomes from eubacteria resembling pathogens, to an archaeon that shares properties with eukaryotes and to its mutant that allows antibiotics binding, demonstrated the unambiguous difference between mere binding and therapeutical effectiveness. The observed variability in antibiotics inhibitory modes, accompanied by the elucidation of the structural basis to antibiotics mechanism justifies expectations for structural based improved properties of existing compounds as well as for the development of novel drugs.

• Korean Journal of Agricultural Science
• /
• v.43 no.1
• /
• pp.33-39
• /
• 2016

Brassicaceae consists of important species that have significant amounts of metabolites, and many studies have been carried out in order to understand the mechanism that improves the content of these metabolites. In Brassicacea, Cardamine manshurica Nakai is one of the important edible plants and is rich in oil, fiber, and various nutrients. In this study, we constructed cDNA library using leaves from 4 week-old plants and analyzed the ESTs of C. manshurica Nakai. One thousand thirty-nine ESTs were discovered which assembled to form 468 unigenes. The latter contained 116 contigs and 352 singletons. Similarity search of these ESTs with BLASTX revealed similarities with Arabidopsis thaliana 285 (31.9%), Arabidopsis lyrata 172 (19.3%), Capsella rubella 162 (18.1%), and Eutrema salsugineum 137 (15.3%). ESTs were functionally categorized into molecular function, biological process, and cellular component, and each category took 10.6%, 58.5%, and 30.9%, respectively. The functional analysis also found that 94.9% of ESTs showed at least one GO ID. Microsatellite analysis of 468 unigene sequences revealed 225 structures of which Di-, Tri-, Tetra-, Penta-repeats were 35.6% (80/225), 63.1% (142/225), 0.9% (2/225), and 0.4% (1/225), respectively. The results from our study can be a valuable resource for Cardamine research.

• Korean Journal of Plant Taxonomy
• /
• v.44 no.3
• /
• pp.191-201
• /
• 2014

In order to find useful taxonomic morphological characters, 17 taxa from East-Asia Astragalus and Oxytropis anertii were investigated. In this study, seed coat structure, fruit surface, and fruit anatomical structures were selected to classify the species in Astragalus. As a results, useful morphological and anatomical characters in East-Asia Astragalus were life cycle, leaflet shape, raceme, petal color, seed color, pod shape, absent or present of hairs in pod surface, bent degree of dorsal suture, and thickness of endocarp. Using medicinal sources in China, A. floridus, A. membranaceus, A. membranaceus var. mongholicus and A. tongolensis were formed same group. However, these were not completely consensus in the morphological characters. The other hand, A. koraiensis and A. sikokianus, which have controversial taxonomic issue, have clearly no differences morphological characters each other. Therefore, A. koraiensis, A. sikokianus, and A. bhotanensis should be conducted a comparative study on the DNA sequences and molecular cytology in order to clarify the taxonomic treatments in the near future.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.1
• /
• pp.60.1-60.1
• /
• 2015

High energy photons and mechanical energy produced by the process of star formation result in copious FIR molecular and atomic lines, which are important coolants of the system. Photons thermally or mechanically induced could dissociate water in the dense envelope to change relative abundances among the species of O, OH, and H2O. Here we analyze OH emission lines toward embedded young stellar objects (YSOs) observed as part of the Herschel open time key program, 'Dust, Ice, and Gas In Time (DIGIT)' in order to study the physical conditions of associated gas and the energy budget loaded on the OH line emission. According to our analysis of the Herschel/PACS spectra, OH emission peaks at the central spaxel in most of sources, but several sources show spatially extended emission structures. In the extended emission sources, the distribution of OH emission is correlated with that of [OI] emission and extended along the outflow directions. Considering the diversity of source properties, ratios between detected OH lines are relatively constant among sources. In addition, each OH line has strong correlation with bolometric luminosity. In order to determine the physical conditions of YSOs, we adopt several methods for the analysis of the OH lines: rotational diagram, non-LTE LVG analysis, and a 2-D PDR code. From the simple LVG analysis, we find that the thermal solution with the dense ( > $10^7cm^{-3}$) and warm ( ~ 100 K) OH gas reproduces the ratios of detected OH lines. However, our self-consistent PDR 2-D model, which can deal with the IR-pumping effect from the central protostar as well as the warm dust in situ, cannot fit the observational results, suggesting that an irradiated shock model is necessary for a better interpretation.

• Journal of Adhesion and Interface
• /
• v.10 no.3
• /
• pp.127-133
• /
• 2009

Acrylic pressure sensitive adhesives (PSAs) are used in various field of high-technology industries such as semiconductor, display, mobile, automobile, and so on. Because of they have high durabilities and can be easily introduced functional groups in their molecular structures. PSA perfomances has an effect on their applications in industry process operation, reliability of final products. In this study, PSA performances as a function of fim thickness which is one of the impact factors effects on PSA performances will be investigated using combinatorial methods. Acrylic PSAs are synthesized using 2-ethylhexyl acrylate and acrylic acid. Thickness-gradient of acrylic PSA sample is made by a micro applicator. We compare general coating method with thickness-gradient coating method and evaluate the reappearance of combinatorial methods compared with existing coating method. Thickness-gradient of acrylic PSA sample shows rough and broad data tendency.

• Korean Journal of Pharmacognosy
• /
• v.44 no.4
• /
• pp.320-325
• /
• 2013

"SaCheolNaMu" has been used as a Korean folk medicine for the jaundice, lumbago and uterine diseases. Although a crude drug related to this folk medicine is sold in traditional herbal market, the botanical origin of this drug has not been pharmacognostically confirmed yet. In this study, the morphological and anatomical characteristics of the stem of Euonymus species growing in Korea, i.e. Euonymus japonica and E. fortunei var. radicans were studied to clarify the botanical origin of "SaCheolNaMu". As a result, it was found that these two species could be discriminated by the morphological criteria such as the thickness of cuticles, the number of collenchyma cell layers, and the frequency of druse and resinous substance. According to these criteria, it was elucidated that the commercial folk medicine "SaCheolNaMu" was the stem of E. japonica. Meanwhile, HPLC-DAD analysis on the 70% ethanolic extracts of two species showed significantly different HPLC profiles each other. The molecular ions of three characteristic peaks shown in the chromatogram of two species were identified by ESI-MS, and their structures were estimated to be flavonol glycosides.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.06a
• /
• pp.88.1-88.1
• /
• 2010

Organic dyes, because of their many advantages, such as high molar extinction coefficients, convenience of customized molecular design for desired photophysical and photochemical properties, inexpensiveness with no transition metals contained, and environment-friendliness, are suitable as photosensitizers for the Dye-sensitized Solar Cell (DSSC). The efficiency of DSSC based on metal-free organic dyes is known to be much lower than that of Ru dyes generally, but a high solar energy-to-electricity conversion efficiency of up to 8% in full sunlight has been achieved by Ito et al. using an indoline dye. This result suggests that smartly designed and synthesized metal-free organic dyes are also highly competitive candidates for photosensitizers of DSSCs with their advantages mentioned above. Recently, the performance of DSSC based on metal-free organic dyes has been remarkably improved by several groups. We had reported the novel organic dye with double electron acceptor chromophore, which was a new strategy to design an efficient photosensitizer for DSSC. To verify the strategy, we synthesized organic dyes whose geometries, electronic structures and optical properties were derived from preceding density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. In this paper, we successfully synthesized the chromophore containing multi-acceptor push-pull system from triphenylamine with thiophene moieties as a bridge unit. Organic dyes with a single electron acceptor and double acceptor system were also synthesized for comparison purposes. The photovoltaic performances of these dyes were compared, and the recombination dark current curves and the incident photon-to-current (IPCE) efficiencies were also measured in order to characterize the effects of the multi-anchoring groups on the open-circuit voltage and the short-circuit current. In order to match specifications required for practical applications to be implemented outdoors, light soaking and thermal stability tests of these DSSCs, performed under $100mWcm^{-2}$ and $60^{\circ}C$ for 1000h.