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- Berthomier, M., et al.
(författare)
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Alfven : magnetosphere-ionosphere connection explorers
- 2012
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Ingår i: Experimental astronomy. - Dordrecht : Springer. - 0922-6435 .- 1572-9508. ; 33:2-3, s. 445-489
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Tidskriftsartikel (refereegranskat)abstract
- The aurorae are dynamic, luminous displays that grace the night skies of Earth's high latitude regions. The solar wind emanating from the Sun is their ultimate energy source, but the chain of plasma physical processes leading to auroral displays is complex. The special conditions at the interface between the solar wind-driven magnetosphere and the ionospheric environment at the top of Earth's atmosphere play a central role. In this Auroral Acceleration Region (AAR) persistent electric fields directed along the magnetic field accelerate magnetospheric electrons to the high energies needed to excite luminosity when they hit the atmosphere. The "ideal magnetohydrodynamics" description of space plasmas which is useful in much of the magnetosphere cannot be used to understand the AAR. The AAR has been studied by a small number of single spacecraft missions which revealed an environment rich in wave-particle interactions, plasma turbulence, and nonlinear acceleration processes, acting on a variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster magnetospheric research mission is now fortuitously visiting the AAR, but its particle instruments are too slow to allow resolve many of the key plasma physics phenomena. The Alfv,n concept is designed specifically to take the next step in studying the aurora, by making the crucial high-time resolution, multi-scale measurements in the AAR, needed to address the key science questions of auroral plasma physics. The new knowledge that the mission will produce will find application in studies of the Sun, the processes that accelerate the solar wind and that produce aurora on other planets.
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| 4. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 6. |
- Briand, Elisabeth, 1979, et al.
(författare)
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An OEGylated thiol monolayer for the tethering of liposomes and the study of liposome interactions
- 2010
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140. ; 81:4-5, s. 1153-1161
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present work is to develop a protocol for the specific immobilization of liposomes, via tethers, onto functionalized gold surfaces, and in addition to give one example for such a surface architecture All surface functionalization steps are charcerized and controlled First, mixed thiolate self-assembled monolayers (SAMs) prepared from COOH- and OCH3-terminated oligo(ethylene glycol) (OEG) alkane thiols were characterized by polarization modulation reflection absorption infrared spectroscopy (PM-RAIRS) and by X-ray photoemission spectroscopy (XPS). The composition of the mixed SAMs was found to be close to that of the thiol solution. Next, grafting of biotin conjugated with an NH2-terminated OEG spacer (biotin-OEG-NH2) to the COOH groups via conventional amine coupling was optimized with respect to the COOH/OCH3 ratio of the SAM. The grafting of biotin-OEG-NH2 was assessed by monitoring the binding of neutravidin and albumin to the biotinylated surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D), as well as by PM-RAIRS It was shown that a COOH/OCH3 ratio of around 0.3 was sufficient to saturate the SAMs with neutravidin. Finally, tethering of liposomes onto the neutravidin-terminated SAMs. was achieved. As an application example. of a close packed layer of tethered liposomes was exposed to the membrane-penetrating peptide melittin As monitored by QCM-D. the liposomes fused when interacting with the peptide and ruptured into an extended. supported lipid bilayer over the whole surface. In summary, the described surface modification has potential for the development of assays requiring tethered Intact liposomes, or tethered planar bilayers. Such surface architectures are especially important for the study of transmembrane proteins and peptides.
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| 7. |
- Briand, Elisabeth, 1979, et al.
(författare)
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Chemical Modifications of Au/SiO2 Template Substrates for Patterned Biofunctional Surfaces
- 2011
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 27:2, s. 678-685
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to create patterned surfaces for localized and specific biochemical recognition. For this purpose, we have developed a protocol for orthogonal and material-selective surface modifications of microfabricated patterned surfaces composed of SiO2 areas (100 mu m diameter) surrounded by Au. The SiO2 spots were chemically modified by a sequence of reactions (silanization using an amine-terminated silane (APTES), followed by amine coupling of a biotin analogue and biospecific recognition) to achieve efficient immobilization of streptavidin in a functional form. The surrounding Au was rendered inert to protein adsorption by modification by HS(CH2)(10)CONH-(CH2)(2)(OCH2CH2)(7)OH (thiol-OEG). The surface modification protocol was developed by testing separately homogeneous SiO2 and Au surfaces, to obtain the two following results: (i) SiO2 surfaces which allowed the grafting of streptavidin, and subsequent immobilization of biotinylated antibodies, and (ii) Au surfaces showing almost no affinity for the same streptavidin and antibody solutions. The surface interactions were monitored by quartz crystal microbalance with dissipation monitoring (QCM-D), and chemical analyses were performed by polarization modulation-reflexion absorption infrared spectroscopy (PM-RAIRS) and X-ray photoelectron spectroscopy (XPS) to assess the validity of the initial orthogonal assembly of APTES and thiol-OEG. Eventually, microscopy imaging of the modified Au/SiO2 patterned substrates validated the specific binding of streptavidin on the SiO2/APTES areas, as well as the subsequent binding of biotinylated anti-rIgG and further detection of fluorescent rIgG on the functionalized SiO2 areas. These results demonstrate a successful protocol for the preparation of patterned biofunctional surfaces, based on microfabricated Au/SiO2 templates and supported by careful surface analysis. The strong immobilization of the biomolecules resulting from the described protocol is advantageous in particular for micropatterned substrates for cell-surface interactions.
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| 9. |
- Cheray, M, et al.
(författare)
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Cytosine methylation of mature microRNAs inhibits their functions and is associated with poor prognosis in glioblastoma multiforme
- 2020
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Ingår i: Molecular cancer. - : Springer Science and Business Media LLC. - 1476-4598. ; 19:1, s. 36-
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundLiterature reports that mature microRNA (miRNA) can be methylated at adenosine, guanosine and cytosine. However, the molecular mechanisms involved in cytosine methylation of miRNAs have not yet been fully elucidated. Here we investigated the biological role and underlying mechanism of cytosine methylation in miRNAs in glioblastoma multiforme (GBM).MethodsRNA immunoprecipitation with the anti-5methylcytosine (5mC) antibody followed by Array, ELISA, dot blot, incorporation of a radio-labelled methyl group in miRNA, and miRNA bisulfite sequencing were perfomred to detect the cytosine methylation in mature miRNA. Cross-Linking immunoprecipiation qPCR, transfection with methylation/unmethylated mimic miRNA, luciferase promoter reporter plasmid, Biotin-tagged 3’UTR/mRNA or miRNA experiments and in vivo assays were used to investigate the role of methylated miRNAs. Finally, the prognostic value of methylated miRNAs was analyzed in a cohorte of GBM pateints.ResultsOur study reveals that a significant fraction of miRNAs contains 5mC. Cellular experiments show that DNMT3A/AGO4 methylated miRNAs at cytosine residues inhibit the formation of miRNA/mRNA duplex and leading to the loss of their repressive function towards gene expression. In vivo experiments show that cytosine-methylation of miRNA abolishes the tumor suppressor function of miRNA-181a-5p miRNA for example. Our study also reveals that cytosine-methylation of miRNA-181a-5p results is associated a poor prognosis in GBM patients.ConclusionTogether, our results indicate that the DNMT3A/AGO4-mediated cytosine methylation of miRNA negatively.Graphical abstract
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