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유연한 연결기를 갖는 새로운 방향족 Polyformamidine의 합성과 성질
정화진 한국섬유공학회 2003 한국섬유공학회지 Vol.40 No.5
New aromatic polyformamidines were prepared by reaction of triethyl orthoformate with aromatic diamines containing various flexible linkages such as ether, isopropylidene, and hexafluoroisopropylidene between aromatic rings in N.N-dimethylsufoxide(DMSO) via high temperature solution polycondensation. The proposed structures of the resultant polymers were confirmed by elemental analysis, IR- and $^1$H-NMR spectroscopy. These polymers had inherent viscosities up to 0.42 dL/g, and most of them could be readily soluble in aprotic amide solvents including N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and DMSO at room temperature. Wide angle X-ray diffractograms(WAXD) revealed that the polymers were partially crystalline or amorphous. The glass transition temperatures of the polymers could be determined by differential scanning calorimetry (DSC) and were in the range of 118∼245 $^{\circ}C$. Thermogravimetric analysis(TGA) indicated that the polymers are stable in nitrogen up to 300 $^{\circ}C$, and 10% weight loss occurred in the temperature range of 320∼395 $^{\circ}C$ in air.
Negative feedback regulation of Wnt signaling by Gβγ-mediated reduction of Dishevelled
정화진,Hyun Joon Kim,Suk Kyung Lee,Rokki Kim,Will Kopachik,Jin-Kwan Han,조익훈 생화학분자생물학회 2009 Experimental and molecular medicine Vol.41 No.10
Wnt signaling is known to be important for diverse embryonic and post-natal cellular events and be regulated by the proteins Dishevelled and Axin. Although Dishevelled is activated by Wnt and involved in signal transduction, it is not clear how Dishevelled-mediated signaling is turned off. We report that guanine nucleotide binding protein beta 2 (Gnb2; Gβ2) bound to Axin and Gβ2 inhibited Wnt mediated reporter activity. The inhibition involved reduction of the level of Dishevelled, and the Gβ2γ2 mediated reduction of Dishevelled was countered by increased expression of Axin. Consistent with these effects in HEK293T cells, injection of Gβ2γ2 into Xenopus embryos inhibited the formation of secondary axes induced either by XWnt8 or Dishevelled, but not by β-catenin. The DEP domain of Dishevelled is necessary for both interaction with Gβ2γ2 and subsequent degradation of Dishevelled via the lysosomal pathway. Signaling induced by Gβ2γ2 is required because a mutant of Gβ2, Gβ2 (W332A) with lower signaling activity, had reduced ability to downregulate the level of Dishevelled. Activation of Wnt signaling by either of two methods, increased Frizzled signaling or transient transfection of Wnt, also led to increased degradation of Dishevelled and the induced Dishevelled loss is dependent on Gβ1 and Gβ2. Other studies with agents that interfere with PLC action and calcium signaling suggested that loss of Dishevelled is mediated through the following pathway: Wnt/Frizzled →Gβγ → PLC →Ca+2/PKC signaling. Together the evidence suggests a novel negative feedback mechanism in which Gβ2γ2 inhibits Wnt signaling by degradation of Dishevelled.
항종양 인자 p53 및 PTEN의 활성화를 중심으로 하는 항산화제 셀레늄의 암 예방 기전 연구
정화진,서영록 대한암예방학회 2007 Journal of cancer prevention Vol.12 No.4
Selenomethionine (SeMet) has been identified as one of the organic selenium compounds although the mechanism of chemopreventive action of SeMet was not clear yet. In our previous study, we suggested that p53 might be involved in chmopreventive effect of SeMet. Here, we investigated the implication of the p53 modulated by redox signal in response to SeMet in cancer prevention. We confirmed that the p53 accumulation was significantly increased in response to SeMet as dose-dependent manner. In addition, the differential localization of p53 protein was observed in nucleolus contrast with in redox factor 1 (Ref-1)-dominant negative cells indicating that p53 function for genomic stability might be modulated by redox signaling. On the other hand, PTEN known as a tumor suppressor with the inhibition of PI3K/Akt signaling pathway has no significant differences in the presence with SeMet suggesting that the chemopreventive mechanism of SeMet might be on PTEN-independent pathway. In our study, we suggested that p53 activation and localization in nucleolus might be a distinct cellular pathway of SeMet as one of the chemopreventive compounds. (Cancer Prev Res 12, 256-260, 2007) Key Words: p53, PTEN, Selenomethionine