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  • 1
    Electronic Resource
    Electronic Resource
    Syntheses of well-defined star-shaped poly(tetrahydrofuran) polyols by the ion-coupling method (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 3403-3408 
    Details
    ISSN: 0887-624X
    Keywords: star-shaped ; poly(THF) ; ion-coupling ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The prepoly(tetrahydrofuran) [poly(THF)] capped with hydroxyl and tetrahydrothiophenium groups was prepared using tetrahydrothiophene to terminate the living cationic polymerization of THF initiated by BF3·OEt2 and epichlorohydrin (ECH) at low conversion. Well-defined star-shaped poly(THF) polyols were synthesized by an ion-coupling reaction of the prepoly(THF) with tri- or tetrafunctional benzenecarboxylates, respectively, and this process proceeded by precipitation when the solution of the prepolymer in THF was added to an aqueous solution containing an excess of the corresponding coupling reagent. GPC studies showed that all of the carboxylate groups of every coupling reagent molecule took part in the ion-coupling reaction simultanously. This was confirmed by IR spectra. Almost all of the prepolymers were coupled to form star polymers after repeating the precipitation four times. 1H-NMR illustrated that both the star-shaped polymers and the prepolymers contained primary and secondary hydroxyl end groups. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3403-3408, 1997
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Cationic polymerization of 1,3-dioxepane in the presence of 2,2-bis(hydroxymethyl)butanol (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2899-2903 
    Details
    ISSN: 0887-624X
    Keywords: cationic ring-opening polymerization ; poly(1,3-dioxepane) triol ; 2,2-bis(hydroxymethyl)butanol ; transacetalization ; activated monomer mechanism ; activated chain mechanism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cationic polymerization of 1,3-dioxepane (DOP) initiated by triflic acid was carried out in the presence of 2,2-bis(hydroxymethyl)butanol (BHMB). The structure and molecular weight of the products were characterized by GPC and NMR spectra. The results showed that molecular weight of the polyacetal obtained could be controlled by the initial mole ratio of DOP/BHMB. GPC showed that as the mole ratio of BHMB/DOP increased, the content of cyclic oligomers also increased. Proton, 13C and 2D HMQC-fg NMR demonstrated that no hydroxymethyl group of BHMB appeared as an end group. It was also illustrated by proton NMR that some BHMB units existed in cyclic oligomers. The mechanism of formation of cyclic oligomers was discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2899-2903, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Gas permeabilities and permselectivity of photochemically crosslinked polyimides (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 485-489 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Photosensitive polyimide BTDA-3MPDA was modified by UV irradiation. The structure of UV-irradiated polyimides was investigated by FTIR and gel fraction measurements. The results showed that longer UV exposure time resulted in a higher extent of crosslinking. The gas permeabilities of hydrogen, oxygen and nitrogen through UV-irradiated polyimides were characterized in a temperature range from 30°C to 90°C. Photocrosslinking resulted in a sharp decline in gas permeability for hydrogen, oxygen, and nitrogen through polyimide in the initial stage of photocrosslinking. Then, as the crosslinked benzophenone percentage amounted to 28-38% for hydrogen, 17-31% for oxygen and 3-28% for nitrogen, the gas permeabilities showed another sharp decline. Gas permselectivity increased significantly with the progress of photocrosslinking, and it can be adjusted in a wide range by controlling the extent of crosslinking. Arrhenius plots of gas permeability for hydrogen and oxygen through UV-irradiated polyimides are straight lines; for nitrogen, however, change in the slope of the straight line is observed and activation energies for hydrogen and oxygen permeation show abrupt increases when crosslinked benzophenone percentage amounts to about 30%. UV-irradiated polyimides with simultaneous high gas permeability and permselectivity make them ideal candidate materials for gas separation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070580301
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  • 4
    Electronic Resource
    Electronic Resource
    Study on the cationic polymerization mechanism of 1,3-dioxepane in the presence of ethylene glycol (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 2613-2622 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The cationic polymerization of 1,3-dioxepane (DOP) initiated with trifluoromethanesulfonic acid (I) in the presence of ethylene glycol (EG) was investigated. At sufficiently low concentration of the initiator ([I] 〉 0.01 mol/L vs. [EG] 〈 0.20 mol/L), the molecular weights of the obtained polyacetal oligodiols are controlled by the mole ratio of consumed DOP to initial EG. Gel-permeation chromatography studies revealed that the concentration of cyclic oligomers in the products are negligible. The mechanism of the polymerization was investigated by means of kinetic studies. The results showed that the polymerization proceeds according to the active chain end mechanism (ACF) in combination with the activated monomer mechanism (AM); thus the cyclic oligomer in the obtained polymer is reduced, and intermolecular chain transfer to EG in ACE is dominant. It was also demonstrated that as [DOP]2[I]/[EG] decreases the contribution of ACE to the polymerization decreases and that of AM increases. In addition, 1H and 13C NMR data illustrated that each macromolecule of polyDOP oligodiols contained one EG unit on average and that no EG end groups exist.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980819
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  • 5
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    Anti-HBV efficacy of combined siRNAs targeting viral gene and heat shock cognate 70 (2012)
    BioMed Central
    Details
    Publication Date: 2012-11-17
    Description: Background: Hepatitis B virus (HBV) infection is a major health concern with more than two billion individuals currently infected worldwide. Because of the limited effectiveness of existing vaccines and drugs, development of novel antiviral strategies is urgently needed. Heat stress cognate 70 (Hsc70) is an ATP-binding protein of the heat stress protein 70 family. Hsc70 has been found to be required for HBV DNA replication. Here we report, for the first time, that combined siRNAs targeting viral gene and siHsc70 are highly effective in suppressing ongoing HBV expression and replication. Methods: We constructed two plasmids (S1 and S2) expressing short hairpin RNAs (shRNAs) targeting surface open reading frame of HBV(HBV S) and one plasmid expressing shRNA targeting Hsc70 (siHsc70), and we used the EGFP-specific siRNA plasmid ( siEGFP) as we had previously described. First, we evaluated the gene-silencing efficacy of both shRNAs using an enhanced green fluorescent protein (EGFP) reporter system and flow cytometry in HEK293 and T98G cells. Then, the antiviral potencies of HBV-specific siRNA (siHBV) in combination with siHsc70 in HepG2.2.15 cells were investigated. Moreover, type I IFN and TNF-alpha induction were measured by quantitative real-time PCR and ELISA. Results: Cotransfection of either S1 or S2 with an EGFP plasmid produced an 80%--90% reduction in EGFP signal relative to the control. This combinational RNAi effectively and specifically inhibited HBV protein, mRNA and HBV DNA, resulting in up to a 3.36 log10 reduction in HBV load in the HepG2.2.15 cell culture supernatants. The combined siRNAs were more potent than siHBV or siHsc70 used separately, and this approach can enhance potency in suppressing ongoing viral gene expression and replication in HepG2.2.15 cells while forestalling escape by mutant HBV. The antiviral synergy of siHBV used in combination with siHsc70 produced no cytotoxicity and induced no production of IFN-alpha, IFN-beta and TNF-alpha in transfected cells. Conclusions: Our combinational RNAi was sequence-specific, effective against wild-type and mutant drug-resistant HBV strains, without triggering interferon response or producing any side effects. These findings indicate that combinational RNAi has tremendous promise for developing innovative therapy against viral infection.
    Electronic ISSN: 1743-422X
    Topics: Medicine
    Published by BioMed Central
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  • 6
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    A Multi-scalar Palmer Drought Severity Index (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-07-08
    Description: The limitation of the fixed time scale in the Palmer drought severity index (PDSI) family has long been criticized in drought literatures. By modifying the algorithm of duration factors estimation of the self-calibrating PDSI (SC-PDSI), this paper proposed a new approach that could extend the time scale in a wide range. The properties of these newly derived SC-PDSI variants (denoted as SC-PDSI x ) at short, medium and long time scales respectively, were evaluated through comparisons with the multi-scalar standardized precipitation evapotranspiration index (SPEI) over 134 meteorological sites in China. Results show that new SC-PDSI x generally inherits the advantages of original SC-PDSI with a rather stable behavior in aspects of drought frequency and other statistical characteristics. Besides, the spatiotemporal pattern of the 2011 drought reflected by matched SC-PDSI x and SPEI is very similar, indicating the multi-scalar SC-PDSI could be a useful alternative to monitor droughts at different time scales.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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  • 7
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    Amyloid beta1-42 (Aβ42) up-regulates the expression of sortilin via the p75NTR/RhoA signaling pathway (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2013-07-31
    Description: Sortilin, a Golgi sorting protein and a member of the VPS10P family, is the co-receptor for proneurotrophins, regulates protein trafficking, targets proteins to lysosomes and regulates low density lipoprotein metabolism. The aim of this study was to investigate the expression and regulation of sortilin in Alzheimer's disease (AD). A significantly increased level of sortilin was found in human AD brain and in the brains of 6-month-old APPswe/PS1dE9 transgenic mice. Aβ 42 enhanced the protein and mRNA expression levels of sortilin in a dose- and time-dependent manner in SH-SY5Y APP695 cells, but had no effect on sorLA. In addition, proBDNF also significantly increased the protein and mRNA expression of sortilin in these cells. The recombinant extracellular domain of p75 NTR (P75ECD-FC), or the antibody against the extracellular domain of p75 NTR , blocked the upregulation of sortilin induced by Aβ, suggesting that Aβ 42 increased the expression level of sortilin and mRNA in SH-SY5Y via the p75 NTR receptor. Inhibition of ROCK, but not JNK, suppressed constitutive and Aβ 42 -induced expression of sortilin. In conclusion, this study shows that sortilin expression is increased in the AD brain in human and mice and that Aβ 42 oligomer increases sortilin gene and protein expression through p75 NTR and RhoA signaling pathways, suggesting a potential physiological interaction of Aβ 42 and sortilin in Alzheimer's disease. This article is protected by copyright. All rights reserved.
    Print ISSN: 0022-3042
    Electronic ISSN: 1471-4159
    Topics: Medicine
    Published by Wiley-Blackwell on behalf of The International Society for Neurochemistry.
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  • 8
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    Differential efficiency in exogenous DNA acquisition among closely related Salmonella strains: implications in bacterial speciation (2014)
    BioMed Central
    Details
    Publication Date: 2014-06-15
    Description: Background: Acquisition of exogenous genetic material is a key event in bacterial speciation. It seems reasonable to assume that recombination of the incoming DNA into genome would be more efficient with higher levels of relatedness between the DNA donor and recipient. If so, bacterial speciation would be a smooth process, leading to a continuous spectrum of genomic divergence of bacteria, which, however, is not the case as shown by recent findings. The goal of this study was todetermine if DNA transfer efficiency is correlated with the levels of sequence identity. Results: To compare the relative efficiency of exogenous DNA acquisition among closely related bacteria, we carried out phage-mediated transduction and plasmid-mediated transformation in representative Salmonella strains with different levels of relatedness. We found that the efficiency was remarkably variable even among genetically almost identical bacteria. Although there was a general tendency that more closely related DNA donor-recipient pairs had higher transduction efficiency, transformation efficiency exhibited over a thousand times difference among the closely related Salmonella strains. Conclusion: DNA acquisition efficiency is greatly variable among bacteria that have as high as over 99% identical genetic background, suggesting that bacterial speciation involves highly complex processes affected not only by whether beneficial exogenous DNA may exist in the environment but also the "readiness" of the bacteria to accept it.
    Electronic ISSN: 1471-2180
    Topics: Biology
    Published by BioMed Central
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  • 9
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    A case of lipoprotein glomerulopathy with thrombotic microangiopathy due to malignant hypertension (2013)
    BioMed Central
    Details
    Publication Date: 2013-03-01
    Description: Background: Lipoprotein glomerulopathy (LPG) is a rare inherited renal disease characterized by intraglomerular lipoprotein within the lumina of severely dilated glomerular capillaries. The common clinical presentation of LPG includes proteinuria or nephrotic syndrome. Hypertension and anemia were thought to be mild in LPG. Thrombotic microangiopathy (TMA) in LPG has not been previously reported. In this report, we present a patient with LPG that developed TMA. To the best of our knowledge, this is the first report of TMA in LPG.Case presentationFour years ago (2005), a 19-year-old Chinese woman was diagnosed with nephrotic syndrome and provided prednisone treatment. A combination of prednisone and cyclophosphamide did not have any effect and was discontinued after six months. Although she was steroid-resistant, over the next subsequent three years, she maintained normal renal function without anemia and thrombocytopenia. In February 2009, she had a severe headache and blurry vision and presented at a local hospital with severe hypertension. Blood pressure was 220/160 mmHg. Laboratory data showed hemoglobin 3.8 g/dL; platelet counts 29x109/L; urinary protein 7.90 g/d; total bilirubin 29.9 umol/L; indirect bilirubin 28.2 umol/L; LDH 1172 U/L; ALB 2.66 g/dL; urea nitrogen 52 mg/dL; serum creatinine 3.2 mg/dL; triglyceride 253 mg/dL; total cholesterol 273 mg/dL. ANA, ds-DNA, ANCA, anti-GBM antibody and anticardiolipin were all negative. A renal biopsy revealed LPG with TMA. Genetic evaluation showed the patient carried the APOE Kyoto mutation. Adequate control of blood pressure improved microangiopathic anemia and thrombocytopenia, however, renal function did not improve and she eventually developed uremia and became hemodialysis dependent. Conclusion: We report on a rare case of TMA probably due to malignant hypertension in LPG. Early lipid-lowering and antihypertensive treatment may improve outcome. The pathophysiologic relationship between LPG and TMA should be investigated further.
    Electronic ISSN: 1471-2369
    Topics: Medicine
    Published by BioMed Central
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  • 10
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    Association between CHEK2 H371Y mutation and response to neoadjuvant chemotherapy in women with breast cancer (2015)
    BioMed Central
    Details
    Publication Date: 2015-03-29
    Description: Background: Our previous study suggested that the recurrent CHEK2 H371Y mutation is a novel pathogenic mutation that confers an increased risk of breast cancer. The purpose of this study was to investigate whether breast cancer patients with CHEK2 H371Y mutation were more likely to respond to neoadjuvant chemotherapy. Methods: We screened a cohort of 2334 Chinese women with operable primary breast cancer who received a neoadjuvant chemotherapy regimen for CHEK2 H371Y germline mutations. Pathologic complete response (pCR) was defined as the absence of tumor cells in the breast after the completion of neoadjuvant chemotherapy. Results: Thirty-nine patients (1.7%) with CHEK2 H371Y germline mutation were identified in this cohort of 2334 patients. CHEK2 H371Y mutation carriers had a significantly higher pCR rate than non-carriers (33.3% versus 19.5%, P = 0.031) in the entire study population, and CHEK2 H371Y mutation-positive status remained an independent favorable predictor of pCR in a multivariate analysis (odds ratio [OR] = 3.01; 95% confidence interval [CI]: 1.34- 6.78, P = 0.008). CHEK2 H371Y carriers had a slightly worse distant recurrence-free survival than non-carriers (adjusted hazard ratio [HR] =1.24, 95% CI: 0.59-2.63). Conclusions: CHEK2 H371Y mutation carriers are more likely to respond to neoadjuvant chemotherapy than are non-carriers.
    Electronic ISSN: 1471-2407
    Topics: Medicine
    Published by BioMed Central
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