• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.74-74
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• 2003

We report here the results on N-acetyl-N'-methylamide of oxazolidine (Ac-Oxa-NHMe) calculated using the ab initio molecular orbital method with the self-consistent reaction field (SCRF) theory at the HF level of theory with the 6-3l+G(d) basis set. The displacement of the $\square$-CH$_2$ group in proline ring by oxygen atom has affected the structure of proline, cis$\^$∼/ trans equilibrium, and rotational barrier. The up-puckered structure is found to be prevalent for the trans conformers of the Oxa amide. The higher cis populations of the Oxa amide can be interpreted due to the longer distance between the acetyl methyl group and the 5-methylene group of the ring for the trans conformer of the Oxa amide than that of the Pro amide. The changes in charge of the prolyl nitrogen and the decrease in electron overlap of the C$\^$∼/ N bond for TS structures seem to play a role in lowering rotational barriers of the Oxa amide compared to that of the Pro amide. The calculated preferences for cis conformers in the order of Oxa > Pro amides and for trans-to-cis rotational barriers in the order of Pro > Oxa amide in water are consistent with experimental results on Oxa-containing peptides. The pertinent distance between the prolyl nitrogen and the N$\^$∼/ H amide group to form a hydrogen bond might indicate that this intramolecular hydrogen bond could contribute in stabilizing the TS structures of Oxa and Pro amides and play a role in prolyl isomerization.

• Nutrition Research and Practice
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• v.18 no.1
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• pp.62-77
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• 2024

BACKGROUND/OBJECTIVES: Colorectal cancer (CRC) is the third most common cancer worldwide with a high recurrence rate. Oxaliplatin (OXA) resistance is one of the major reasons hindering CRC therapy. β-Carotene (BC) is a provitamin A and is known to have antioxidant and anticancer effects. However, the combined effect of OXA and BC has not been investigated. Therefore, this study investigated the anticancer effects and mechanism of the combination of OXA and BC on CRC. MATERIALS/METHODS: In the present study, the effects of the combination of OXA and BC on cell viability, cell cycle arrest, and cancer stemness were investigated using HCT116, HT29, OXA-resistant cells, and human CRC organoids. RESULTS: The combination of OXA and BC enhanced apoptosis, G₂/M phase cell cycle arrest, and inhibited cancer cell survival in human CRC resistant cells and CRC organoids without toxicity in normal organoids. Cancer stem cell marker expression and self-replicating capacity were suppressed by combined treatment with OXA and BC. Moreover, this combined treatment upregulated apoptosis and the stem cell-related JAK/STAT signaling pathway. CONCLUSIONS: Our results suggest a novel potential role of BC in reducing resistance to OXA, thereby enhances the anticancer effects of OXA. This enhancement is achieved through the regulation of cell cycle, apoptosis, and stemness in CRC.

• Microbiology and Biotechnology Letters
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• v.49 no.2
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• pp.239-248
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• 2021

The emergence of multidrug-resistant Acinetobacter baumannii has partly increased treatment failure and patient mortality. Class D β-lactamases is an important mechanism of resistance to beta-lactam antibiotics in this species. This study aimed to investigate the relationship between the presence oxacillinase gene and genetic fingerprints of A. baumannii isolates from the intensive care unit of an Egyptian tertiary care hospital. One hundred and twenty A. baumannii clinical isolates were collected. Multiplex PCR was performed to detect genes encoding oxacillinases (OXA-23, OXA-24, OXA-51, OXA-58 and OXA-143). Molecular typing of all collected isolates was performed using random amplified polymorphic DNA (RAPD)-PCR assay. Out of 120 examined isolates, 92, 88 and 84% were resistant to ertapenem, imipenem and meropenem, respectively. The species-specific, commonly present OXA-51 gene was found in all isolates while OXA-23 showed a high prevalence of 88% of isolates. OXA-24 and OXA-143 genes were detected in 3% and 1% of isolates, respectively. No OXA-58 gene was detected. Five clusters consisting of 19 genotypes were detected using RAPD-PCR. Genotype A was the most prevalent, it was observed in 62% of the isolates followed by genotype B (12%). These results revealed that genotypes A and B are common in the hospital. Results also demonstrate that RAPD-PCR is a rapid and reliable method for studying the clonal similarity among A. baumannii isolated from different clinical specimens.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.2
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• pp.94-101
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• 2016

Acinetobacter species isolates are important opportunistic pathogens and commonly implicated in nosocomial infections. The therapeutic options for treatment of the bacterial infections are limited because the bacteria isolates are usually multidrug resistant (MDR). In the current study, we investigated various carbapenemase genes in 68 Acinetobacter species isolates. Antimicrobial susceptibilities were tested using the disk diffusion method. Screening of carbapenemase genes was performed via multiplex PCR. In addition, PCR and DNA sequencing were used to identify the carbapenemase genes. Repetitive extragenic palindromic-PCR (REP-PCR) was also performed to assess the clonality of isolates. In our study, A. baumannii isolates were highly resistant to all agents tested while all non-A. baumannii isolates were susceptible to all agents tested, with the exception of aztreonam and cefotaxime. All 51 A. baumannii isolates contained the $bla_{OXA-51}$ gene and 37 (72.5%) isolates also harbored the $bla_{OXA-23}$ gene. In addition, 39 MDR A. baumannii isolates were identified in our study and 37 isolates contained the $bla_{OXA-23}$ gene. The 37 MDR strains harboring $bla_{OXA-23}$ showed type I (n=22) or type II (n=15) banding patterns on their REP-PCR profiles. Our results suggest clonal relation and horizontal spreading of MDR A. baumannii isolates containing the $bla_{OXA-23}$ gene at the hospital located in Daejeon. Continuous investigation of antimicrobial resistant determinants and monitoring emergence and dissemination of MDR isolates is required to prevent and control infection and colonization of MDR A. baumannii isolates.

• Biomedical Science Letters
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• v.22 no.2
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• pp.29-36
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• 2016

Among the several agents causing carbapenem resistance of Acinetobacter baumannii, the most common cause is OXA-23 ${\beta}$-lactamase, which is known to hydrolyze carbapenem. To effectively control dissemination of carbapenem-resistant Acinetobacter baumannii (CRAB), development of both rapid and easy-to-use detection methods are required. The aim of this study is to develop a novel immunochromatographic assay (ICA) for rapid detection of OXA-23 ${\beta}$-lactamase. Of the seven monoclonal antibodies (mAbs) screened by ELISA, four mAbs (4G6, 4H6, 6G4, 9A4) exhibited high reactivity. Of these four specific antibodies, the combination of 6G4/4G6 showed the greatest reactivity and this combination of mAbs (6G4/4G6 mAbs) was used to develop the OXA-23 ${\beta}$-lactamase ICA. Of 102 A. baumannii isolates tested, the OXA-23 ${\beta}$-lactamase ICA results were consistent with PCR analysis except one false positive and one false negative isolate. The overall sensitivity and specificity were 98.36% and 97.56%, respectively. In conclusion, to the best of our knowledge, we have developed the first specific antibody set to detect OXA-23 ${\beta}$-lactamase using an ICA kit. This novel ICA can be used as a reliable and easy-to-use immunological assay for detection of OXA-23 ${\beta}$-lactamase producing CRAB in clinical laboratories.

• Osong Public Health and Research Perspectives
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• v.9 no.6
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• pp.325-333
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• 2018

Objectives: The purpose of this study was to determine the presence of IMP and OXA genes in clinical strains of Pseudomonas aeruginosa (P. aeruginosa) that are carriers of the ampC gene. Methods: In this study, 105 clinical isolates of P. aeruginosa were collected. Antibiotic resistance patterns were determined using the disk diffusion method. The strains carrying AmpC enzymes were characterized by a combination disk method. Multiplex-PCR was used to identify resistance and virulence genes, chi-square test was used to determine the relationship between variables. Results: Among 105 isolates of P. aeruginosa, the highest antibiotic resistance was to cefotaxime and aztreonam, and the least resistance was to colictin and ceftazidime. There were 49 isolates (46.66%) that showed an AmpC phenotype. In addition, the frequencies of the resistance genes were; OXA48 gene 85.2%, OXA199, 139 3.8%, OXA23 3.8%, OXA2 66.6%, OXA10 3.8%, OXA51 85.2% and OXA58 3.8%. The IMP27 gene was detected in 9 isolates (8.57%) and the IMP3.34 was detected in 11 isolates (10.47%). Other genes detected included; lasR (17.1%), lasB (18%) and lasA (26.6%). There was a significant relationship between virulence factors and the OX and IMP genes ($p{\leq}0.05$). Conclusion: The relationship between antibiotic resistance and virulence factors observed in this study could play an important role in outbreaks associated with P. aeruginosa infections.

• Korean Journal of Clinical Laboratory Science
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• v.54 no.3
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• pp.179-191
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• 2022

Carbapenem-resistant Enterobacteriaceae (CRE) poses an increasing public health threat and has limited treatment options with high associated mortality. Genotypes of carbapenemase that threaten public health (bla_KPC, bla_NDM, bla_IMP, and bla_VIM) and bla_OXA-48-like genes were detected by phenotypic and molecular diagnosis, and related gene distribution patterns were investigated. Phenotypic testing using the modified Hodge test confirmed positivity in all 41 strains examined, and carbapenemase inhibitory testing using meropenem+phenyl boronic acid or meropenem+EDTA confirmed positivity in 18 and 8 strains, respectively. Polymerase chain reaction revealed the presence of amplification products in 28 strains of bla_KPC, 25 strains of bla_NDM, 5 strains of bla_IMP, 1 strain of bla_VIM, and 13 bla_OXA-48-like strains. In addition, 7 strains of bla_KPC+bla_NDM, 1 strain of bla_KPC+bla_IMP, 1 strain of bla_NDM+bla_OXA-48-like, 1 strain of bla_NDM+bla_VIM, 4 strains of bla_KPC+bla_NDM+bla_IMP, and 4 strains of bla_KPC+bla_NDM+bla_OXA-48-like were identified. Melting curve analysis using real-time PCR was wholly consistent with PCR results. The study shows genetic identification of highly specific CRE by real-time PCR could be used to provide early diagnoses and infection control, improve surveillance, and prevent the transmission of CRE.

• Bulletin of the Korean Chemical Society
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• v.27 no.3
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• pp.395-398
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• 2006

Nerve agents (sarin, tabun, soman and VX) are class of military important substances able to cause many severe intoxications during few minutes. Currently, the threat of misuse of these agents is daily discussed. Unfortunately, there is no single antidote able to treat intoxication caused by all of these agents. Owing to this fact, new generation of antidotes, especially acetylcholinesterase (AChE; EC 3.1.1.7) reactivators, is still developed. In this study, we have tested four newly developed AChE reactivators: 1-(4-hydroxyiminomethylpyridinium)- 5-(4-carbamoylpyridinium)-3-oxa-pentane dibromide (1), 1-(3-hydroxyiminomethylpyridinium)-5-(4-carbamoylpyridinium)-3-oxa-pentane dibromide (2), 1,5-bis(2-hydroxyiminomethylpyridinium)-3-oxa-pentane dichloride (3) and 1,5-bis(4-hydroxyiminomethylpyridinium)-3-oxa-pentane dibromide (4) for their potency to reactivate in vitro tabun and cyclosarin-inhibited AChE. Their reactivation efficacy was compared with currently the most promising oxime HI-6 (1-(2-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium)-2-oxa-propane dichloride). According to obtained results, two AChE reactivators 1 and 4 were able to reactivate tabun-inhibited AChE. On the contrary, there was no better AChE reactivator than HI-6 able to reactivate cyclosarin-inhibited AChE.

• Journal of the Korean Chemical Society
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• v.43 no.5
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• pp.11-503
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• 1999

• Bulletin of the Korean Chemical Society
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• v.29 no.12
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• pp.2331-2336
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• 2008