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  • 1
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    On the structural basis and design guidelines for type II topoisomerase-targeting anticancer drugs (2013)
    Oxford University Press
    Details
    Publication Date: 2013-12-07
    Description: Type II topoisomerases (Top2s) alter DNA topology via the formation of an enzyme–DNA adduct termed cleavage complex, which harbors a transient double-strand break in one DNA to allow the passage of another. Agents targeting human Top2s are clinically active anticancer drugs whose trapping of Top2-mediated DNA breakage effectively induces genome fragmentation and cell death. To understand the structural basis of this drug action, we previously determined the structure of human Top2 β-isoform forming a cleavage complex with the drug etoposide and DNA, and described the insertion of drug into DNA cleavage site and drug-induced decoupling of catalytic groups. By developing a post-crystallization drug replacement procedure that simplifies structural characterization of drug-stabilized cleavage complexes, we have extended the analysis toward other structurally distinct drugs, m -AMSA and mitoxantrone. Besides the expected drug intercalation, a switch in ribose puckering in the 3'-nucleotide of the cleavage site was robustly observed in the new structures, representing a new mechanism for trapping the Top2 cleavage complex. Analysis of drug-binding modes and the conformational landscapes of the drug-binding pockets provide rationalization of the drugs’ structural-activity relationships and explain why Top2 mutants exhibit differential effects toward each drug. Drug design guidelines were proposed to facilitate the development of isoform-specific Top2-targeting anticancer agents.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 2
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    VisANT 4.0: Integrative network platform to connect genes, drugs, diseases and therapies (2013)
    Oxford University Press
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    Publication Date: 2013-06-23
    Description: With the rapid accumulation of our knowledge on diseases, disease-related genes and drug targets, network-based analysis plays an increasingly important role in systems biology, systems pharmacology and translational science. The new release of VisANT aims to provide new functions to facilitate the convenient network analysis of diseases, therapies, genes and drugs. With improved understanding of the mechanisms of complex diseases and drug actions through network analysis, novel drug methods (e.g., drug repositioning, multi-target drug and combination therapy) can be designed. More specifically, the new update includes (i) integrated search and navigation of disease and drug hierarchies; (ii) integrated disease–gene, therapy–drug and drug–target association to aid the network construction and filtering; (iii) annotation of genes/drugs using disease/therapy information; (iv) prediction of associated diseases/therapies for a given set of genes/drugs using enrichment analysis; (v) network transformation to support construction of versatile network of drugs, genes, diseases and therapies; (vi) enhanced user interface using docking windows to allow easy customization of node and edge properties with build-in legend node to distinguish different node type. VisANT is freely available at: http://visant.bu.edu .
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 3
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    A model for 3:2 HFQPO pairs in black hole binaries based on cosmic battery (2016)
    Oxford University Press
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    Publication Date: 2016-02-28
    Description: A model for 3:2 high-frequency quasi-periodic oscillations (HFQPOs) with 3:2 pairs observed in four black hole X-ray binaries (BHXBs) is proposed by invoking the epicyclic resonances with the magnetic connection (MC) between a spinning black hole (BH) with a relativistic accretion disc. It turns out that the MC can be worked out due to Poynting–Robertson cosmic battery, and the 3:2 HFQPO pairs associated with the steep power-law states can be fitted in this model. Furthermore, the severe damping problem in the epicyclic resonance model can be overcome by transferring energy from the BH to the inner disc via the MC process for emitting X-rays with sufficient amplitude and coherence to produce the HFQPOs. In addition, we discuss the important role of the magnetic field in state transition of BHXBs.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 4
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    Solution structure and tandem DNA recognition of the C-terminal effector domain of PmrA from Klebsiella pneumoniae (2014)
    Oxford University Press
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    Publication Date: 2014-04-03
    Description: Klebsiella pneumoniae PmrA is a polymyxin-resistance-associated response regulator. The C-terminal effector/DNA-binding domain of PmrA (PmrA C ) recognizes tandem imperfect repeat sequences on the promoters of genes to induce antimicrobial peptide resistance after phosphorylation and dimerization of its N-terminal receiver domain (PmrA N ). However, structural information concerning how phosphorylation of the response regulator enhances DNA recognition remains elusive. To gain insights, we determined the nuclear magnetic resonance solution structure of PmrA C and characterized the interactions between PmrA C or BeF 3 – -activated full-length PmrA (PmrA F ) and two DNA sequences from the pbgP promoter of K. pneumoniae . We showed that PmrA C binds to the PmrA box, which was verified to contain two half-sites, 5'-CTTAAT-3' and 5'-CCTAAG-3', in a head-to-tail fashion with much stronger affinity to the first than the second site without cooperativity. The structural basis for the PmrA C –DNA complex was investigated using HADDOCK docking and confirmed by paramagnetic relaxation enhancement. Unlike PmrA C , PmrA F recognizes the two sites simultaneously and specifically. In the PmrA F –DNA complex, PmrA N may maintain an activated homodimeric conformation analogous to that in the free form and the interactions between two PmrA C molecules aid in bending and binding of the DNA duplex for transcription activation.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 5
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    A bio-inspired computing model for ovarian carcinoma classification and oncogene detection (2015)
    Oxford University Press
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    Publication Date: 2015-04-03
    Description: Motivation: Ovarian cancer is the fifth leading cause of cancer deaths in women in the western world for 2013. In ovarian cancer, benign tumors turn malignant, but the point of transition is difficult to predict and diagnose. The 5-year survival rate of all types of ovarian cancer is 44%, but this can be improved to 92% if the cancer is found and treated before it spreads beyond the ovary. However, only 15% of all ovarian cancers are found at this early stage. Therefore, the ability to automatically identify and diagnose ovarian cancer precisely and efficiently as the tissue changes from benign to invasive is important for clinical treatment and for increasing the cure rate. This study proposes a new ovarian carcinoma classification model using two algorithms: a novel discretization of food sources for an artificial bee colony (DfABC), and a support vector machine (SVM). For the first time in the literature, oncogene detection using this method is also investigated. Results: A novel bio-inspired computing model and hybrid algorithms combining DfABC and SVM was applied to ovarian carcinoma and oncogene classification. This study used the human ovarian cDNA expression database to collect 41 patient samples and 9600 genes in each pathological stage. Feature selection methods were used to detect and extract 15 notable oncogenes. We then used the DfABC-SVM model to examine these 15 oncogenes, dividing them into eight different classifications according to their gene expressions of various pathological stages. The average accuracyof the eight classification experiments was 94.76%. This research also found some oncogenes that had not been discovered or indicated in previous scientific studies. The main contribution of this research is the proof that these newly discovered oncogenes are highly related to ovarian or other cancers. Availability and implementation: http://mht.mis.nchu.edu.tw/moodle/course/view.php?id=7 Contact: mychen@nutc.edu.tw
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
    Published by Oxford University Press
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  • 6
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    Haploinsufficiency of RCBTB1 is associated with Coats disease and familial exudative vitreoretinopathy (2016)
    Oxford University Press
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    Publication Date: 2016-03-24
    Description: Familial exudative vitreoretinopathy (FEVR) belongs to a group of genetically and clinically heterogeneous disorders in retinal vascular development. To date, in approximately 50% of patients with FEVR, pathogenic mutations have been detected in FZD4 , LRP5 , TSPAN12 , NDP and ZNF408 . In this study, we identified two heterozygous frameshift mutations in RCBTB1 from three Taiwanese cases through exome sequencing. In patient-derived lymphoblastoid cell lines (LCLs), the protein level of RCBTB1 is approximately half that of unaffected control LCLs, which is indicative of a haploinsufficiency mechanism. By employing transient transfection and reporter assays for the transcriptional activity of β-catenin, we demonstrated that RCBTB1 participates in the Norrin/FZD4 signaling pathway and that knockdown of RCBTB1 by shRNA significantly reduced nuclear accumulation of β-catenin under Norrin and Wnt3a treatments. Furthermore, transgenic fli1 :EGFP zebrafish with rcbtb1 knockdown exhibited anomalies in intersegmental and intraocular vessels. These results strongly support that reduced RCBTB1 expression may lead to defects in angiogenesis through the Norrin-dependent Wnt pathway, and that RCBTB1 is a putative genetic cause of vitreoretinopathies.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
    Published by Oxford University Press
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  • 7
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    Long-term X-ray emission from Swift J1644+57 (2013)
    Oxford University Press
    Details
    Publication Date: 2013-09-06
    Description: The X-ray emission from Swift J1644+57 is not steadily decreasing; instead, it shows multiple pulses with declining amplitudes. We model the pulses as reverse shocks from collisions between the late ejected shells and the externally shocked material, which is decelerated while sweeping the ambient medium. The peak of each pulse is taken as the maximum emission of each reverse shock. With a proper set of parameters, the envelope of peaks in the light curve as well as the spectrum can be modelled well.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 8
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    Preparation of monoPEGylated Cyanovirin-N's derivative and its anti-influenza A virus bioactivity in vitro and in vivo (2015)
    Oxford University Press
    Details
    Publication Date: 2015-05-28
    Description: Influenza A virus (IAV) has been raising public health and safety concerns worldwide. Cyanovirin-N (CVN) is a prominent anti-IAV candidate, but both cytotoxicity and immunogenicity have hindered the development of this protein as a viable therapy. In this article, linker-CVN (LCVN) with a flexible and hydrophilic polypeptide at the N-terminus was efficiently produced from the cytoplasm of Escherichia coli at a 〉15-l scale. PEGylation at the N-terminal α-amine of LCVN was also reformed as 20 kDa PEGylated linkered Cyanovirin-N (PEG 20k –LCVN). The 50% effective concentrations of PEG 20k –LCVN were 0.43 ± 0.11 µM for influenza A/HK/8/68 (H3N2) and 0.04 ± 0.02 µM for A/Swan/Hokkaido/51/96 (H5N3), dramatically lower than that of the positive control, Ribavirin (2.88 ± 0.66 x 10 3 µM and 1.79 ± 0.62 x 10 3 µM, respectively). A total of 12.5 µM PEG 20k –LCVN effectively inactivate the propagation of H3N2 in chicken embryos. About 2.0 mg/kg/day PEG 20k –LCVN increased double the survival rate (66.67%, P = 0.0378) of H3N2 infected mice, prolonged the median survival period, downregulated the mRNA level of viral nuclear protein and decreased (attenuated) the pathology lesion in mice lung. A novel PEGylated CVN derivative, PEG 20k –LCVN, exhibited potent and strain-dependent anti-IAV activity in nanomolar concentrations in vitro, as well as in micromolar concentration in vivo .
    Print ISSN: 0021-924X
    Electronic ISSN: 1756-2651
    Topics: Biology , Chemistry and Pharmacology
    Published by Oxford University Press on behalf of The Japanese Biochemical Society (JBS).
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  • 9
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    Global Oct4 target gene analysis reveals novel downstream PTEN and TNC genes required for drug-resistance and metastasis in lung cancer (2015)
    Oxford University Press
    Details
    Publication Date: 2015-02-18
    Description: Overexpression of Oct4, a stemness gene encoding a transcription factor, has been reported in several cancers. However, the mechanism by which Oct4 directs transcriptional program that leads to somatic cancer progression remains unclear. In this study, we provide mechanistic insight into Oct4-driven transcriptional network promoting drug-resistance and metastasis in lung cancer cell, animal and clinical studies. Through an integrative approach combining our Oct4 chromatin-immunoprecipitation sequencing and ENCODE datasets, we identified the genome-wide binding regions of Oct4 in lung cancer at promoter and enhancer of numerous genes involved in critical pathways which promote tumorigenesis. Notably, PTEN and TNC were previously undefined targets of Oct4. In addition, novel Oct4-binding motifs were found to overlap with DNA elements for Sp1 transcription factor. We provided evidence that Oct4 suppressed PTEN in an Sp1-dependent manner by recruitment of HDAC1/2, leading to activation of AKT signaling and drug-resistance. In contrast, Oct4 transactivated TNC independent of Sp1 and resulted in cancer metastasis. Clinically, lung cancer patients with Oct4 high, PTEN low and TNC high expression profile significantly correlated with poor disease-free survival. Our study reveals a critical Oct4-driven transcriptional program that promotes lung cancer progression, illustrating the therapeutic potential of targeting Oc4 transcriptionally regulated genes.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 10
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    Macroscale distribution of virioplankton and heterotrophic bacteria in the Bohai Sea (2016)
    Oxford University Press
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    Publication Date: 2016-03-02
    Description: In light of limited research into the relationship between the macroscale distribution and dynamic changes of microplankton in the shallow Bohai Sea, here we used flow cytometry to analyse samples collected from the Bohai Sea channel in winter and summer. Results showed that the average of both viral abundance (VA) and bacterial abundance (BA) were lower in winter (3.61  x  10 7 and 1.84  x  10 6 cells/mL, respectively) than in summer (7.47  x  10 7 and 5.05  x  10 6 cells/mL, respectively). At all 16 stations, VA was one order of magnitude greater than BA, with a positive relationship between one another. In the horizontal distribution, variations in VA and BA followed a similar trend, and both were obviously higher near-shore than offshore. In the vertical distribution, variations in both VA and BA did not show a clear relationship with water depth. VA and BA in summer were 2.1 and 2.7 times those in winter, respectively. Spearman correlation analysis showed that both VA and BA were correlated with the concentration of PO 4 -P in winter (positive) and NO 3 -N in summer (negative). Additionally, BA showed a negative correlation with salinity. It is clear that the macroscale distribution of these two kinds of microbes in the Bohai Sea is related to seasonal variation and nutrient availability.
    Print ISSN: 0168-6496
    Electronic ISSN: 1574-6941
    Topics: Biology
    Published by Oxford University Press
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