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Influences of Bridge Group on Thermal and Mechanical Properties of Epoxy Resins
Liu Yuan,Zhao Jun,Liu Ai-Qin,Liu Xiao-Qing,Luo Jun 한국고분자학회 2020 폴리머 Vol.44 No.4
In order to obtain thermosetting epoxy resin, it is the prerequisite condition that the epoxy precursor must contain at least two epoxy groups. Thus, bridge group is needed to link the epoxy groups, and naturally, the chemical structure of the bridge group may also influence the thermomechanical performances of the cured epoxy resin. However, literature about the effects of bridge group on properties of cured epoxy is seldom published. To fill the gap, three model epoxy monomers containing different bridge groups have been synthesized from 4,4"-dihydroxydiphenyl, 1,1-bis(4- hydroxyphenyl)cyclohexane and bisphenol A in this work. After chemical structure confirmation, all of the monomers are cured by methylhexahydrophthalic anhydride (HMMPA), and the properties of the obtained cured network are evaluated by differential scanning calorimetry (DSC), dynamic thermomechanical analysis (DMA), tensile test and scanning electron microscope (SEM). The results show that bulky bridge group can effectively increase the glass transition temperature, enhance the tensile strength, and enlarge elongation at break of the cured epoxy resin.
Zhong-Liu Zhou,Wen-Qing Yin,Xiao-Peng Zou,Dan-Ying Huang,Cui-Liu Zhou,Lian-Mei Li,Ke-Cheng Chen,Zi-Ying Guo,San-Qing Lin 한국응용생명화학회 2014 Applied Biological Chemistry (Appl Biol Chem) Vol.57 No.6
The extraction and solvent partition of the leaves ofEucalyptus citriodora, and repeated column chromatography for n-BuOH fraction yielded a new flavonoid glycoside, citrioside C (1),along with three known flavonoid glycosides (2-4). The latter wereidentified with kaempferol-3-O-β-D-glucopyranosyl (12)-α-L-rhamnoside(2), kaempferol-3-O-α-L-rhamnoside (3), and quercetin-3-O-α-Lrhamnoside(4). Their chemical structures were identified on thebasis of spectroscopic data analyses including NMR, MS, UV, andIR. All constitutents were isolated for the first time from the leavesof Eucalyptus citriodora. The potential antivirus activity of all theisolated compounds was evaluated. Compound 4 showed potentantiviral activity against respiratory syncytial virus with 50%inhibition concentration (IC50) value of 1.9 μg/mL and selectiveindex value of 9.8.
Zhou, Zhong-Liu,Yin, Wen-Qing,Zou, Xiao-Peng,Huang, Dan-Ying,Zhou, Cui-Liu,Li, Lian-Mei,Chen, Ke-Cheng,Guo, Zi-Ying,Lin, San-Qing 한국응용생명화학회 2014 Applied Biological Chemistry (Appl Biol Chem) Vol.57 No.6
The extraction and solvent partition of the leaves of Eucalyptus citriodora, and repeated column chromatography for n-BuOH fraction yielded a new flavonoid glycoside, citrioside C (1), along with three known flavonoid glycosides (2-4). The latter were identified with kaempferol-3-O-${\beta}$-$\small{D}$-glucopyranosyl (12)-${\alpha}$-$\small{L}$-rhamnoside (2), kaempferol-3-O-${\alpha}$-$\small{L}$-rhamnoside (3), and quercetin-3-O-${\alpha}$-$\small{L}$-rhamnoside (4). Their chemical structures were identified on the basis of spectroscopic data analyses including NMR, MS, UV, and IR. All constitutents were isolated for the first time from the leaves of Eucalyptus citriodora. The potential antivirus activity of all the isolated compounds was evaluated. Compound 4 showed potent antiviral activity against respiratory syncytial virus with 50% inhibition concentration ($IC_{50}$) value of $1.9{\mu}g/mL$ and selective index value of 9.8.
Liu, Xue-Ni,Tang, Zheng-Hao,Zhang, Yi,Pan, Qing-Chun,Chen, Xiao-Hua,Yu, Yong-Sheng,Zang, Guo-Qing Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.1
Rhomboids were identified as the first intramembrane serine proteases about 10 years ago. Since then, the study of the rhomboid protease family has blossomed. Rhomboid domain containing 1 (RHBDD1), highly-expressed in human testis, contains a rhomboid domain with unknown function. In the present study, we tested the hypothesis that RHBDD1 was associated with proliferation and apoptosis in hepatocellular carcinoma using recombinant lentivirus-mediated silencing of RHBDD1 in HepG2 cells. Our results showed that down-regulation of RHBDD1 mRNA levels markedly suppressed proliferation and colony formation capacity of HepG2 human hepatoma cancer cells in vitro, and induced cell cycle arrest. We also found that RHBDD1 silencing could obviously trigger HepG2 cell apoptosis. In summary, it was demonstrated that RHBDD1 might be a positive regulator for proliferative and apoptotic characteristics of hepatocellular carcinoma.
Fast Transient Buck Converter Using a Hysteresis PWM Controller
Liu, Yong-Xiao,Zhao, Jin-Bin,Qu, Ke-Qing The Korean Institute of Power Electronics 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.6
In this paper, a fast transient buck converter using hysteresis PWM control is presented. The proposed control method is based on hysteresis control of the capacitor C voltage. This offers a faster transient response to meet the challenges of the power supply requirements for fast dynamic input and load changes. It also provides better stability and solves the compensation problem of the error amplifier in conversional voltage PWM control. Finally, the steady-state and dynamic operation of the proposed control method are analyzed and verified by simulation and experimental results.
Liu, Ying,Zhou, Long-Shu,Xu, Xiao-Ming,Deng, Liang-Qing,Xiao, Qian-Kun Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.9
Aim: We aimed to investigate the associations of dietary intake of folate, vitamin $B_6$ and $B_{12}$ and MTHFR genotype with breast cancer in a Chinese population. Methods: A matched case-control study was conducted, and 435 patients with newly diagnosed and histologically confirmed breast cancer and 435 controls were collected. The folate intake, vitamin $B_6$ and vitamin $B_{12}$ were calculated, and MTHFR C665T, C677T and A1298C were analyzed by PCR-RFLP. Results: We found vitamin $B_{12}$ was likely to reduce the risk of breast cancer, and MTHFR 665TT was associated with increased risk of breast cancer. Folate intake, vitamin $B_{12}$ intake and variants of MTHFR C677T and MTHFR A1298C demonstrated no association with risk of breast cancer. However, we found patients with low intake of vitamin $B_6$ and MTHFR 665TT genotype had a higher risk of breast cancer (OR=1.87, 95% CI=1.29-2.77), the association being less pronounced among subjects with a moderate intake of vitamin $B_6$ and MTHFR 665TT genotype (OR=1.58, 95% CI=1.03-2.49, P=0.03). Conclusion: Our study indicated that the MTHFR C665T polymorphism and vitamin $B_6$ are associated with risk of breast cancer, which indicated roles for nutrients in developing breast cancer.
Liu, Jun-Bao,Dai, Chun-Mei,Su, Xiao-Yun,Cao, Lu,Qin, Rui,Kong, Qing-Bo Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.22
To study the gene expression change and possible signal pathway during androgen-dependent prostate cancer (ADPC) becoming androgen-independent prostate cancer (AIPC), an LNCaP cell model of AIPC was established using flutamide in combination with androgen-free environment inducement, and differential expression genes were screened by microarray. Then the biological process, molecular function and KEGG pathway of differential expression genes are analyzed by Molecule Annotation System (MAS). By comparison of 12,207 expression genes, 347 expression genes were acquired, of which 156 were up-ragulated and 191 down-regulated. After analyzing the biological process and molecule function of differential expression genes, these genes are found to play crucial roles in cell proliferation, differntiation, cell cycle control, protein metabolism and modification and other biological process, serve as signal molecules, enzymes, peptide hormones, cytokines, cytoskeletal proteins and adhesion molecules. The analysis of KEGG show that the relevant genes of AIPC transformation participate in glutathione metabolism, cell cycle, P53 signal pathway, cytochrome P450 metabolism, Hedgehog signal pathway, MAPK signal pathway, adipocytokines signal pathway, PPAR signal pathway, TGF-${\beta}$ signal pathway and JAK-STAT signal pathway. In conclusion, during the process of ADPC becoming AIPC, it is not only one specific gene or pathway, but multiple genes and pathways that change. The findings above lay the foundation for study of AIPC mechanism and development of AIPC targeting drugs.
Kinetics and computational docking studies on the inhibition of tyrosinase induced by oxymatrine.
Liu, Xiao-Xia,Sun, Shi-Qing,Wang, Yu-Jie,Xu, Wei,Wang, Yi-Fang,Park, Daeui,Zhou, Hai-Meng,Han, Hong-Yan Humana Press 2013 Applied biochemistry and biotechnology Vol.169 No.1
<P>A combination of enzymatic inhibition kinetics and computational prediction was employed to search for an effective inhibitor of tyrosinase. We found that oxymatrine significantly inhibited tyrosinase, and that this reaction was not accompanied by detectable conformational changes. Kinetic analysis showed that oxymatrine reversibly inhibited tyrosinase in a mixed-type manner. Measurements of intrinsic and ANS-binding fluorescences showed that oxymatrine did not induce any conspicuous changes in the tertiary structure. We also conducted a docking simulation between tyrosinase and oxymatrine using two docking programs, Dock6.3 and AutoDock4.2 (binding energy was -118.81 kcal/mol for Dock6 and -8.04 kcal/mol for AutoDock4). The results also suggested that oxymatrine interacts mostly with the residues of CYS83 and HIS263 in the active site of tyrosinase. This strategy of predicting tyrosinase inhibition by simulation of docking coupling with kinetics may prove useful in screening for potential tyrosinase inhibitors. Knowledge of tyrosinase inhibition can provide medical, cosmetic, and agricultural applications. Our study suggests that oxymatrine is an important agent for various applications related to pigment formation.</P>
Abrin Induces HeLa Cell Apoptosis by Cytochrome с Release and Caspase Activation
( Xiao Ling Qu ),( Liu Ting Qing ) 생화학분자생물학회 2004 BMB Reports Vol.37 No.4
We identified apoptosis as being a significant mechanism of toxicity following the exposure of HeLa cell cultures to abrin holotoxin, which is in addition to its inhibition of protein biosynthesis by N-glycosidase activity. The treatment of HeLa cell cultures with abrin resulted in apoptotic cell death, as characterized by morphological and biochemical changes, i.e., cell shrinkage, internudeosomal DNA fragmentation, the occurrence of hypodiploid DNA, chromatin condensation, nudear breakdown, DNA single strand breaks by TUNEL assay, and phosphatidylserine (PS) externalization. This apoptotic cell death was accompanied by caspase-9 and caspase-3 activation, as indicated by the cleavage of caspase substrates, which was preceded by mitochondrial cytochrome c release. The broad-spectrum caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD-fmk), prevented abrin-triggered caspase activation and partially abolished apoptotic cell death, but did not affect mitochondrial cytochrome c release. These results suggest that the release of mitochondrial cytochrome c, and the sequential caspase-9 and caspase-3 activations are important events in the signal transduction pathway of abrin-induced apoptotic cell death in the HeLa cell line.