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The cost of materials is one of the biggest barriers for wastewater driven microbial fuel cells (MFCs). Many studies use expensive materials with idealistic wastes. Realistically the choice of an ion selective membrane or nonspecific separators must be made in the context of the cost and performance of materials available. Fourteen membranes and separators were characterized for durability, oxygen diffusion and ionic resistance to enable informed membrane selection for reactor tests. Subsequently MFCs were operated in a cost efficient reactor design using Nafion, ethylene tetrafluoroethylene (ETFE) or polyvinylidene fluoride (PVDF) membranes, a nonspecific separator (Rhinohide), and a no-membrane design with a carbon-paper internal gas diffusion cathode. Peak power densities during polarisation, from MFCs using no-membrane, Nafion and ETFE, reached 67, 61 and 59 mWm-2, and coulombic efficiencies of 68±11%, 71±12% and 92±6%, respectively. Under 1000Ω, Nafion and ETFE achieved an average power density of 29 mWm-2 compared to 24 mWm-2 for the membrane-less reactors. Over a hypothetical lifetime of 10 years the generated energy (1 to 2.5 kWhm-2) would not be sufficient to offset the costs of any membrane and separator tested. 相似文献
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David A. Korasick Ashley C. Campbell Shelbi L. Christgen Srinivas Chakravarthy Tommi A. White Donald F. Becker John J. Tanner 《Biophysical journal》2018,114(12):2833-2843
Homooligomerization of proline utilization A (PutA) bifunctional flavoenzymes is intimately tied to catalytic function and substrate channeling. PutA from Bradyrhizobium japonicum (BjPutA) is unique among PutAs in that it forms a tetramer in solution. Curiously, a dimeric BjPutA hot spot mutant was previously shown to display wild-type catalytic activity despite lacking the tetrameric structure. These observations raised the question of what is the active oligomeric state of BjPutA. Herein, we investigate the factors that contribute to tetramerization of BjPutA in vitro. Negative-stain electron microscopy indicates that BjPutA is primarily dimeric at nanomolar concentrations, suggesting concentration-dependent tetramerization. Further, sedimentation-velocity analysis of BjPutA at high (micromolar) concentration reveals that although the binding of active-site ligands does not alter oligomeric state, reduction of the flavin adenine dinucleotide cofactor results in dimeric protein. Size-exclusion chromatography coupled with multiangle light scattering and small-angle x-ray scattering analysis also reveals that reduced BjPutA is dimeric. Taken together, these results suggest that the BjPutA oligomeric state is dependent upon both enzyme concentration and the redox state of the flavin cofactor. This is the first report, to our knowledge, of redox-linked oligomerization in the PutA family. 相似文献
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Soil geochemistry confines microbial abundances across an arctic landscape; implications for net carbon exchange with the atmosphere 总被引:1,自引:0,他引:1
N. D. Gray C. M. McCann B. Christgen S. Z. Ahammad J. A. Roberts D. W. Graham 《Biogeochemistry》2014,120(1-3):307-317
A large portion of the World’s terrestrial organic carbon is stored in Arctic permafrost soils. However, due to permafrost warming and increased in situ microbial mineralisation of released carbon, greenhouse gas releases from Arctic soils are increasing, including methane (CH4(g)). To identify environmental controls on such releases, we characterised soil geochemistry and microbial community conditions in 13 near-surface Arctic soils collected across Kongsfjorden, Svalbard. Statistically significant correlations were found between proxies for carbonate mineral content (i.e. Ca and Mg) and soil pH (Spearman rho = 0.87, p < 0.001). In turn, pH significantly inversely correlated with bacterial and Type I methanotroph gene abundances across the soils (r = ?0.71, p = 0.01 and r = ?0.74, p = 0.006, respectively), which also co-varied with soil phosphorous (P) level (r = 0.79, p = 0.01 and r = 0.63, p = 0.02, respectively). These results suggest that soil P supply, which is controlled by pH and other factors, significantly influences in situ microbial abundances in these Arctic soils. Overall, we conclude microbial responses to increasing ‘old carbon’ releases in this Arctic region are constrained by nutrient-deficiency in surface soils, with consequential impacts on the flux and composition of carbon gasses released to the atmosphere. 相似文献
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Ton van Agthoven Lambert C. J. Dorssers Ulrich Lehmann Hans Kreipe Leendert H. J. Looijenga Matthias Christgen 《PloS one》2015,10(8)
Background
Most breast cancers depend on estrogenic growth stimulation. Functional genetic screenings in in vitro cell models have identified genes, which override growth suppression induced by anti-estrogenic drugs like tamoxifen. Using that approach, we have previously identified Breast Cancer Anti-Estrogen Resistance 4 (BCAR4) as a mediator of cell proliferation and tamoxifen-resistance. Here, we show high level of expression and function of BCAR4 in human breast cancer.Methods
BCAR4 mRNA expression was evaluated by (q)RT-PCR in a panel of human normal tissues, primary breast cancers and cell lines. A new antibody raised against C78-I97 of the putative BCAR4 protein and used for western blot and immunoprecipitation assays. Furthermore, siRNA-mediated gene silencing was implemented to study the function of BCAR4 and its downstream targets ERBB2/3.Results
Except for placenta, all human normal tissues tested were BCAR4-negative. In primary breast cancers, BCAR4 expression was comparatively rare (10%), but associated with enhanced proliferation. Relative high BCAR4 mRNA expression was identified in IPH-926, a cell line derived from an endocrine-resistant lobular breast cancer. Moderate BCAR4 expression was evident in MDA-MB-134 and MDA-MB-453 breast cancer cells. BCAR4 protein was detected in breast cancer cells with ectopic (ZR-75-1-BCAR4) and endogenous (IPH-926, MDA-MB-453) BCAR4 mRNA expression. Knockdown of BCAR4 inhibited cell proliferation. A similar effect was observed upon knockdown of ERBB2/3 and exposure to lapatinib, implying that BCAR4 acts in an ERBB2/3-dependent manner.Conclusion
BCAR4 encodes a functional protein, which drives proliferation of endocrine-resistant breast cancer cells. Lapatinib, a clinically approved EGFR/ERBB2 inhibitor, counteracts BCAR4-driven tumor cell growth, a clinical relevant observation. 相似文献7.
Inga Karch Elisa Schipper Henriette Christgen Hans Kreipe Ulrich Lehmann Matthias Christgen 《PloS one》2013,8(8)
Inactivation of CDH1, encoding E-cadherin, promotes cancer initiation and progression. According to a newly proposed molecular mechanism, loss of E-cadherin triggers an upregulation of the anti-apoptotic oncoprotein BCL2. Conversely, reconstitution of E-cadherin counteracts overexpression of BCL2. This reciprocal regulation is thought to be critical for early tumor development. We determined the relevance of this new concept in human infiltrating lobular breast cancer (ILBC), the prime tumor entity associated with CDH1 inactivation. BCL2 expression was examined in human ILBC cell lines (IPH-926, MDA-MB-134, SUM-44) harboring deleterious CDH1 mutations. To test for an intact regulatory axis between E-cadherin and BCL2, wild-type E-cadherin was reconstituted in ILBC cells by ectopic expression. Moreover, BCL2 and E-cadherin were evaluated in primary invasive breast cancers and in synchronous lobular carcinomas in situ (LCIS). MDA-MB-134 and IPH-926 showed little or no BCL2 expression, while SUM-44 ILBC cells were BCL2-positive. Reconstitution of E-cadherin failed to impact on BCL2 expression in all cell lines tested. Primary ILBCs were almost uniformly E-cadherin-negative (97%) and were frequently BCL2-negative (46%). When compared with an appropriate control group, ILBCs showed a trend towards an increased frequency of BCL2-negative cases (P = 0.064). In terminal duct-lobular units affected by LCIS, the E-cadherin-negative neoplastic component showed a similar or a reduced BCL2-immunoreactivity, when compared with the adjacent epithelium. In conclusion, upregulation of BCL2 is not involved in lobular breast carcinogenesis and is unlikely to represent an important determinant of tumor development driven by CDH1 inactivation. 相似文献
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Christgen M Ballmaier M Bruchhardt H von Wasielewski R Kreipe H Lehmann U 《Molecular and cellular biochemistry》2007,306(1-2):201-212
“Side population” (SP) cells, which pump out the fluorescent dye H33342 via the ABCG2 transporter, define a putative stem/progenitor
cell population in the mammary gland. Breast cancer SP cells recently isolated from the MCF-7 cell line possess similar properties
and may represent stem cell-like cancer cells. This study extends SP cell analysis to a broad panel of human breast cancer
cell lines and investigates the expression of differentiation-associated markers in isolated cancer SP cells. Expression of
ABCG2 was determined in 16 breast cancer cell lines by quantitative RT-PCR, Western blotting and immunohistochemistry. Subsequently,
all cell lines were screened for the presence of SP cells. Human breast cancer cell lines commonly express ABCG2. ABCG2-immunoreactivity
was clearly restricted to rare cancer cells in several cell lines including Cal-51. Analysis of H33342-labeled Cal-51 cells
revealed a small fraction of putative SP cells accounting for one percent of all cells. The genuine nature of Cal-51 SP cells
was unambiguously verified by demonstrating a 30-fold increased ABCG2-expression in isolated Cal-51 SP cells. During in vitro expansion, Cal-51 SP cells generated heterologous non-SP (NSP) cells
and ABCG2-expression declined dramatically. In contrast, NSP cells failed to sustain proliferation. Freshly isolated Cal-51 SP cells
also exhibited increased expression of Muc1 and CALLA. Noteworthy, non-malignant mammary epithelial SP cells lack these differentiation markers, highlighting fundamental differences
between non-malignant and breast cancer-derived SP cells. In summary, we established Cal-51 SP cells as a novel in vitro model
to study differential gene expression in breast cancer-derived SP and NSP cells. 相似文献
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Background
During the last years the analysis of microRNA expression patterns has led to completely new insights into cancer biology. Furthermore, these patterns are a very promising tool for the development of new diagnostic and prognostic markers. However, most human tumour samples for which long term clinical records are available exist only as formalin-fixed paraffin-embedded specimens. Therefore, the aim of this study was to examine the feasibility of microRNA profiling studies in routinely processed formalin-fixed paraffin-embedded human breast cancer specimens using fluorescence labelled bead technology. 相似文献10.
Tränkenschuh W Puls F Christgen M Albat C Heim A Poczkaj J Fleming P Kreipe H Lehmann U 《PloS one》2010,5(10):e13688