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Lee, Taek Joon,Chang, Cha-Wen,Hahm, Suk Gyu,Kim, Kyungtae,Park, Samdae,Kim, Dong Min,Kim, Jinchul,Kwon, Won-Sang,Liou, Guey-Sheng,Ree, Moonhor IOP Pub 2009 Nanotechnology Vol.20 No.13
<P>We have fabricated electrically programmable memory devices with thermally and dimensionally stable poly(<I>N</I>-(<I>N</I>′,<I>N</I>′-diphenyl-<I>N</I>′-1,4-phenyl)-<I>N</I>,<I>N</I>-4,4′-diphenylene hexafluoroisopropylidene-diphthalimide) (6F-2TPA PI) films and investigated their switching characteristics and reliability. 6F-2TPA PI films were found to reveal a conductivity of 1.0 × 10<SUP>−13</SUP>–1.0 × 10<SUP>−14</SUP> S cm<SUP>−1</SUP>. The 6F-2TPA PI films exhibit versatile memory characteristics that depend on the film thickness. All the PI films are initially present in the OFF state. The PI films with a thickness of >15 to <100 nm exhibit excellent write-once-read-many-times (WORM) (i.e. fuse-type) memory characteristics with and without polarity depending on the thickness. The WORM memory devices are electrically stable, even in air ambient, for a very long time. The devices’ ON/OFF current ratio is high, up to 10<SUP>10</SUP>. Therefore, these WORM memory devices can provide an efficient, low-cost means of permanent data storage. On the other hand, the 100 nm thick PI films exhibit excellent dynamic random access memory (DRAM) characteristics with polarity. The ON/OFF current ratio of the DRAM devices is as high as 10<SUP>11</SUP>. The observed electrical switching behaviors were found to be governed by trap-limited space-charge-limited conduction and local filament formation and further dependent on the differences between the highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels of the PI film and the work functions of the top and bottom electrodes as well as the PI film thickness. In summary, the excellent memory properties of 6F-2TPA PI make it a promising candidate material for the low-cost mass production of high density and very stable digital nonvolatile WORM and volatile DRAM memory devices. </P>
( Jin Won Hyun ),( Ji Won Cha ),( Mei Jing Piao ),( Ki Cheon Kim ),( Cheng Wen Yao ),( Jian Zheng ),( Seong Min Kim ),( Chang Lim Hyun ),( Yong Seok Ahn ) 한국응용약물학회 2014 Biomolecules & Therapeutics(구 응용약물학회지) Vol.22 No.2
We investigated the protective effects of chlorogenic acid (CGA), a polyphenol compound, on oxidative damage induced by UVBexposure on human HaCaT cells. In a cell-free system, CGA scavenged 1,1-diphenyl-2-picrylhydrazyl radicals, superoxide anions,hydroxyl radicals, and intracellular reactive oxygen species (ROS) generated by hydrogen peroxide and ultraviolet B (UVB). Furthermore, CGA absorbed electromagnetic radiation in the UVB range (280-320 nm). UVB exposure resulted in damage to cellularDNA, as demonstrated in a comet assay; pre-treatment of cells with CGA prior to UVB irradiation prevented DNA damage andincreased cell viability. Furthermore, CGA pre-treatment prevented or ameliorated apoptosis-related changes in UVB-exposedcells, including the formation of apoptotic bodies, disruption of mitochondrial membrane potential, and alterations in the levelsof the apoptosis-related proteins Bcl-2, Bax, and caspase-3. Our findings suggest that CGA protects cells from oxidative stressinduced by UVB radiation.
Ko, Yong-Gi,Kwon, Wonsang,Yen, Hung-Ju,Chang, Cha-Wen,Kim, Dong Min,Kim, Kyungtae,Hahm, Suk Gyu,Lee, Taek Joon,Liou, Guey-Sheng,Ree, Moonhor American Chemical Society 2012 Macromolecules Vol.45 No.9
<P>A series of aromatic polyimides (PIs) were synthesized via the polymerization of 3,3′,4,4′-diphenylsulfonyltetracarboxylic dianhydride with 4,4′-diaminotriphenylamine derivatives containing hydrogen, cyano, methoxy, or dimethylamine substituents. These PIs were thermally and dimensionally stable and produced high-quality thin films when applied in a conventional spin-coating process. Their structure and properties were characterized. Nanoscale thin films of the PIs demonstrated excellent electrical memory performance, with high stabilities and ON/OFF current ratios. The memory characteristics were found to be tunable by varying the substituents; nonvolatile write-once–read-many-times memory behavior, nonvolatile ON/OFF switching type memory behavior, and volatile dynamic random access memory behavior were observed. The memory characteristics were substantially influenced by the electron-accepting cyano- and electron-donating dimethylamine substituents but were apparently not affected by the electron-donating methoxy substituent. In addition, the film density was a significant factor influencing the observed memory behaviors, with larger film densities causing lower OFF-current levels. However, the critical switching-on voltage varied very little as the substituents were changed and was measured to be approximately ±2 V. All of the memory behaviors were found to be governed by a mechanism involving trap-limited space-charge-limited conduction and local filament formation. Overall, all of the PIs assessed in the present work were found to be suitable active materials for the low-cost mass production of high-performance, programmable unipolar memory devices that can be operated with very low power consumption, high ON/OFF current ratios, and high thermal and dimensional stability.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2012/mamobx.2012.45.issue-9/ma300311d/production/images/medium/ma-2012-00311d_0004.gif'></P>
Phloroglucinol inhibits ultraviolet B radiation-induced oxidative stress in the mouse skin
Piao, Mei Jing,Ahn, Mee Jung,Kang, Kyoung Ah,Kim, Ki Cheon,Zheng, Jian,Yao, Cheng Wen,Cha, Ji Won,Hyun, Chang Lim,Kang, Hee Kyoung,Lee, Nam Ho,Hyun, Jin Won Informa Healthcare 2014 International journal of radiation biology Vol.90 No.10
<P><I>Purpose</I>: Previously we demonstrated that phloroglucinol (1,3,5-trihydroxybenzene) protected human HaCaT keratinocytes against ultraviolet B (UVB, 280-320 nm)-induced oxidative stress <I>in vitro</I> by scavenging intracellular reactive oxygen species (ROS). The current study investigated whether phloroglucinol could similarly protect the mouse skin against UVB-induced oxidative tissue damage <I>in vivo</I>.</P><P><I>Materials and methods</I>: Male 7-week-old Balb/c mice were divided into the following untreated normal control, phloroglucinol only-treated, vehicle plus UVB (30 or 60 mJ/cm<SUP>2</SUP>)-exposed, and phloroglucinol (10 or 50 mg/ml) plus UVB (30 or 60 mJ/cm<SUP>2</SUP>)-treated groups. Following UVB exposure, phloroglucinol or phosphate buffered saline vehicle was applied to the dorsal skin of each mouse daily for 3 days. Studies were conducted at 24 h after the last of the UVB exposures. Histopathological analyses of dorsal skin lesions were performed on all mice. In addition, the levels of UVB-provoked injury to cellular components, including DNA, proteins, and lipids were detected by levels of 8-oxoguanine (8-oxoG), protein carbonyls, and 8-isoprostane. Apoptosis were assessed by using western blot for B-cell lymphoma-2-associated X protein (Bax) and activated caspase-3 expression, by using immunohistochemistry.</P><P><I>Results</I>: UVB radiation increased the thickness of the epidermis and the dermis, and also stimulated the accumulation of mast cells in the irradiated skin. However, treatment with phloroglucinol significantly decreased all of these parameters. Furthermore, phloroglucinol decreased UVB-provoked injury to cellular components, including DNA, proteins, and lipids; down-regulated the expression of phospho-histone H2A.X in the injured skin; and reduced the UVB-generated levels of 8-oxoG, protein carbonyls, and 8-isoprostane, which are all markers of oxidative stress. In addition, phloroglucinol attenuated the UVB-induced expression of the pro-apoptotic proteins, Bax protein, and activated caspase-3.</P><P><I>Conclusion</I>: These results suggest that phloroglucinol safeguards the mouse skin against UVB-induced oxidative stress and apoptosis.</P>
Dictyopteris undulata Extract Induces Apoptosis in Human Colon Cancer Cells
Kim, Areum Daseul,Kang, Kyoung Ah,Piao, Jing Mei,Kim, Ki Cheon,Zheng, Jian,Yao, Cheng Wen,Cha, Ji Won,Hyun, Chang Lim,Boo, Sun Jin,Lee, Nam Ho,Na, Soo Young,Hyun, Jin Won 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.3
The present study investigated the cytotoxic and apoptotic effects of an ethanol extract derived from the marine brown alga Dictyopteris undulata against human colon adenocarcinoma cells. The Dictyopteris undulata extract (DUE) showed cytotoxic activity against SW480 cells in a dose-dependent manner, with 50% inhibition of cell viability at a concentration of $40{\mu}g/mL$. DUE also induced programmed cell death in SW480 cells, as evidenced by apoptotic body formation, DNA fragmentation, an increase in the population of apoptotic sub-$G_1$ phase cells, and mitochondrial membrane depolarization. Moreover, DUE significantly modulated the expression of apoptosis-associated proteins, resulting in a decrease in B cell lymphoma-2 expression and an increase in Bcl-2-associated X protein expression, as well as the activation of caspase-9 and caspase-3. Furthermore, DUE showed apoptotic cell death in two other colon cancer cell lines, SNU407 and HT29. These observations suggest that DUE may prove useful as a therapeutic agent for the attenuation of colon cancer.
Zhang, Rui,Kang, Kyoung Ah,Piao, Mei Jing,Kim, Ki Cheon,Zheng, Jian,Yao, Cheng Wen,Cha, Ji Won,Maeng, Young Hee,Chang, Weon Young,Moon, Pyong-Gon,Baek, Moon-Chang,Hyun, Jin Won Lychnia 2014 International journal of oncology Vol.45 No.3
<P>Glutathione S-transferase pi-1 (GSTP-1) is a member of the glutathione S-transferase enzyme superfamily, which catalyzes the conjugation of electrophiles to glutathione during the process of detoxification. In this study, the epigenetic alterations of GSTP-1 expression in human colorectal cancers and the underlying mechanisms were investigated. In 10 colon cancer patients, proteomic analysis revealed that expression of GSTP-1 protein was higher in tumor tissues than in paired adjacent normal tissues. Likewise, in 7 of 10 colon cancer patients, GSTP-1 protein expression was more than 1.5-fold higher in tumor tissues than in adjacent normal tissues, as determined by western blotting. Immunohistochemical data confirmed that GSTP-1 protein was expressed at higher levels in colon cancer tissues compared to normal mucosa. GSTP-1 enzyme activity was closely correlated with GSTP-1 protein expression in colon cancer patients. Consistent with this, GSTP-1 mRNA, protein and activity levels were higher in the colorectal cancer cell lines Caco-2, HCT-116, HT-29, SNU-407 and SNU-1033 compared to the normal colon cell line FHC. Methylation-specific PCR results indicated that the high levels of GSTP-1 in human colorectal cancer cell lines were likely due to the lower degree of promoter methylation in colon cancer cell lines compared to the normal colon cell line, consistent with findings in colon cancer patients. Moreover, the levels of specific activator-protein complexes and histone marks were higher in human colorectal cancer cells compared to the normal human colon cell line, whereas the repressor protein complexes exhibited the opposite pattern. Furthermore, chromatin immunoprecipitation assays demonstrated that expression levels of the transcription factors AP-1 and SP-1 were correlated with the upregulation of GSTP-1 expression in colorectal cancer cells. Finally, knockdown of GSTP-1 promoted the sensitivity of SNU-407 cells to the anticancer agent 5-fluorouracil. These data indicate that GSTP-1 may serve as a clinically useful biomarker of colon cancer and a target for anti-colon cancer drugs.</P>