• Journal of Life Science
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• v.20 no.8
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• pp.1214-1220
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• 2010

Imipenem-resistant bacteria were isolated from clinical specimens taken from hospitalized patients in Suncheon, Korea. Fifty-four isolates were phylogenetically analyzed based on 16S rRNA gene and gyrB gene sequence comparisons. Isolates were affiliated with Pseudomonas aeruginosa (30 strains; 55.6%), Acinetobacter baumannii (21; 38.9%), Enterobacter hormaechei (2) and Pseudomonas putida (2). Twenty-two isolates produced metallo-$\beta$-lactamase (MBL); 12 Acinetobacter baumannii strains, 7 Pseudomonas aeruginosa strains, 2 P. putida strains and 1 Enterobacter hormaechei strain. Antibiotic susceptibility of the isolates was determined using the disc diffusion method and Vitek system. Strains producing metallo-$\beta$-lactamase (type IMP & VIM) were more resistant to antibiotics ceftazidime, aztreonam, amikacin and gentamicin than to strains producing OXA and SHV type of $\beta$-lactamase.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.449-455
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• 2021

Composite materials are substances that are configured to have excellent physical properties by combining the properties of a single substance, and are in the limelight as materials that exceed the performance of metals and polymers. However, it has the disadvantages of long cycle time and high unit price, and much research is being performed to overcome these disadvantages. In this study, we developed an epoxy resin curing agent that can shorten the time required for mass production of composite materials, and tried to expand the applicability of objections by imparting flame retardancy. The epoxy resin used as a basic substance utilized two types of bisphenol F and resorcinol structure, which was further modified using 9,10-dihydro-9-oxa-10-phosphaphenantrene-10-oxide (DOPO) to impart flame retardancy. Triethylphosphate (TEP) and bis [(5-ethyl-2-methyl-1,3,2-dioxaphosphorinan-5-yl)methyl] methyl phosphonate P,P'-dioxide (FR-001) were used as additives, seven kinds of compositions were blended, thermal characteristics (gelation time, glass transition temperature) and flame retardant performance were evaluated. We successfully developed an epoxy matrix that can be applied to high pressure resin transfer molding (HP-RTM) process.

• Macromolecular Research
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• v.13 no.2
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• pp.128-134
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• 2005

The phosphorus comonomer [(6-oxido-6H-dibenz<1,2>oxaphosphorin-6-yl)methyl]-methyl butane-dioate (DOP-MBDA) was synthesized through the addition reaction of dimethyl itaconate (DMI) with 9,10-dihydro­9-oxa-10-phosphaphenan threne-10-oxide (DOP). A series of novel flame retardant poly(butylene terephthalate)s (PBTs) containing different amounts of phosphorus were prepared using DOP-MBDA as a comonomer. These novel polymers were characterized by $^{1}H-NMR$, IR, and differential scanning calorimetry (DSC). The novel phosphorus­containing poly(butylene terephthalate)s, referred to as FR-PBTs, exhibited interesting thermal and mechanical behavior, as well as superior flame retardancy. These properties are attributed to the effect of incorporating the rigid structure of DOP-MBDA and the pendant phosphorus group into the poly(butylene terephthalate) (PBT) homopolymer. The UL 94-V2 rating could be achieved with this novel flame retardant PBT, which has a phosphorus content as low as $0.5 wt\%$, and the FR-PBTs emitted less fumes and toxic gases than the PBT homopolymer.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3502-3508
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• 2014

The first synthetic route to 5'-norcarbocyclic C-nucleoside [7-oxa-7,9-dideazadenosine (furo[3,2-d]pyrimidine) and 9-deazaadenosine (pyrrolo[3,2-d]pyrimidine)] phosphonic acids from commercially available 1,3-dihydroxy cyclopentane was described. The key C-C bond formation from sugar to base precursor was performed using Knoevenagel-type condensation from a ketone derivative. Synthesized C-nucleoside phosphonic acids were tested for anti-HIV activity as well as anti-leukemic activity. Compound 26 showed significant anti-leukemic activity.

• KSBB Journal
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• v.27 no.1
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• pp.57-60
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• 2012

In this study, we evaluated the effects of Biochanin A on glucose uptake in C2C12 myotube. We found that Biochanin A significantly stimulated 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-d-glucose (2-NBDG) uptake in a dose-dependent manner. In addition, AMPK and PPAR-gamma activities were markedly increased by Biochanin A in a dose-dependent manner. However, Akt, an insulin dependent signaling molecule, did not change by Biochanin A. These results suggest that Biochanin A stimulates glucose uptake via AMPK and PPAR-gamma pathways.

• Bulletin of the Korean Chemical Society
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• v.9 no.2
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• pp.98-101
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• 1988

A pure columnar cholesterogen based on the octasubstituted phthalocyanine $(PcH_2)$, S-(+)-2, 3, 9, 10, 16, 17, 23, 24-octakis[5-(dodecyloxy)-2-oxa-pentyl]-phthalocy anine(1a), is described. To evaluate a cholesteric character of 1a, the corresponding achiral $PcH_2$ 1b and the copper complex of chiral $PcH_2$ 1a (CuPc), S-(+)-2,3,9,10,16,17,23,24-octakis[4-(dodecyloxy)- 2-oxapentyl]-phthalocyanine(2a) were also prepared. The chiral 1a exhibited a typical cholesteric texture change in which the transition of platelet (blue phase) to fan-shape texture was observed (K－M－I), whereas the corresponding achiral 1b showed only a focal conic texture (K－ M－I). This is the first instance of a pure columnar cholesterogen observed with discotic liquid crystal systems.

• Bulletin of the Korean Chemical Society
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• v.20 no.3
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• pp.276-280
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• 1999

The different core-modified porphyrins 21-thia-23-carba-12-aza-5,10-dimesityl-15,20-diphenylporphyrin (6), and their N(12)-methyl derivatives (8) were synthesized by acid-catalyzed [3+1] condensation of the corresponding 16-thia-5,10-dimesityltripyrromethanes and 2,4-bis[(α-hydroxy-α-phenyl)methyl]pyrrole. Spectroscopic evidence indicates the existence of two different tautomeric forms at room temperature in porphyrin (6). A third form of tautomer was observed when the temperature was lowered to 223 K. The most stable tautomer is one in which the nitrogenic proton resides outside the core of the macrocycle. The ratio of the three different tautomers (outer N-H/ two inner N-H, i.e. 6/12/13) was 1/l/0.5 in the case of (6) while the ratio of 1/l/0.3 was observed in the case of (10). In the case of 21-oxa-23-carba-12-aza-5,10,15,20-tetraphenylporphyrin (7), the only stable tautomeric form observed by 1H NMR was the one that nitrogenic proton resides inside the core on

• Clean Technology
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• v.23 no.4
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• pp.378-387
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• 2017

To obtain epoxy resin with permanently attached flame-retardant groups, phosphorus compound containing di-hydroxyl group [10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phospha phenanthrene-10-oxide, DOPO-HQ] and silicone compound containing di-hydroxyl group (polydimethylsiloxane, hydroxyl terminated, PDMS) were reacted with uncured epoxy prepolymer (diglycidyl ether of bisphenol A, DGEBA) and then cured using 4,4-diaminodiphenylmethane (DDM) as a crosslinking agent. The properties of the resulting epoxy materials were characterized using Fourier transform infrared (FTIR) spectrometer, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limiting oxygen index (LOI) test/vertical burning test (UL 94-V test), tensile properties test and impact test. This study examined the effect of phosphorus/silicone compound contents on the thermal/mechanical properties and flame retardancy of cured epoxy resins containing phosphorus and silicone compounds. It was found that the thermal/mechanical properties of epoxy resins containing phosphorus and silicone components were higher than those of simple epoxy resin. The flame-retardancy (LOI: 29.9 ~ 31.8% and UL 94-V: V-0) of all samples containing phosphorus compound and phosphrous compound/silicone compound was found to be passed the flame-retardant requirements (LOI: > 30%, UL 94-V: V-0) of LOI and vertical burning tests. However, the flame-retardancy (LOI: 21.4% and UL 94-V: no rating) of simple epoxy resin was found to be failed the flame-retardant requirements.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.4
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• pp.413-419
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• 2017

Four imipenem-resistant bacteria were isolated from the clinical specimens of a patient with pneumonia. To identify the isolates, we used the GN card of Vitek II system and performed a phylogenetic analysis based on 16S rRNA gene sequence. The isolates were identified as P. aeruginosa (2 strains), P. monteilii (1 strain), and P. putida (1 strain), and were tested for antibiotic resistance after determining the MIC of imipenem to be $${\geq_-}8{\mu}g/mL$$ using the AST-N225 card of Vitek II system. The imipenem-resistant genotypes were determined using PCR products amplified using specific ${\beta}-Lactamase$ gene primers. The MBL gene was identified in all four isolates. One strain of P. aeruginosa exhibited the VIM and SHV-1 type genes, while the other strain exhibited both VIM and OXA group II genes. According to the antimicrobial susceptibility test, the bacteria were more susceptible to amikacin than other antibiotics. DNA fingerprint analysis using ERIC-PCR to analyze the epidemiological relationship between strains estimated that both the P. aeruginosa isolates were similar, but exhibited different DNA band types. It is uncommon to find four strains of imipenem-resistant bacteria with different DNA band types in a single patient.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.2
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• pp.100-109
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• 2018

The emergence and dissemination of multidrug-resistant (MDR) Acinetobacter baumannii isolates have been reported worldwide, with most of these possessing the ability to form biofilms. Biofilm formation is an important virulence factor associated with the resistance to disinfection and desiccation. This study examined the genetic basis of antimicrobial resistance mechanisms of biofilm-forming A. baumannii clinical isolates. Imaging and quantification of biofilms were performed by a crystal violet assay and 46 biofilm-forming A. baumannii isolates were selected. Subsequently, 16 isolates belonging to different clones were identified using REP-PCR, and detection of the antimicrobial determinants in the isolates was carried out. The 16 isolates included 9 non-MDR and 7 MDR isolates. The mean biomass $OD_{560}$ values of the non-MDR (0.96) and MDR (1.05) isolates differed but this difference was not significant. In this study, most biofilm-forming MDR A. baumannii isolates contained various antimicrobial resistance determinants ($bla_{OXA-23}$, armA, and mutations of gyrA and parC). On the other hand, most biofilm-forming non-MDR A. baumannii isolates did not contain antimicrobial resistance determinants. These results suggest that there is little correlation between the biofilm-forming ability and antimicrobial susceptibility in A. baumannii isolates. In addition, the emergence of MDR A. baumannii clinical isolates is generally caused by mutations of the genes associated with antimicrobial resistance and/or the acquisition of various antimicrobial resistance determinants.