3,363 research outputs found

    Vesicles in Electric Fields

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    From protection to ordeal: Duldung status and Bosnians in Berlin

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    Bending rigidity of charged lipid bilayer membranes

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    Inward and outward membrane tubes pulled from giant vesicles

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    Guidelines for assessing favourable conservation status of Natura 2000 species and habitat types in Bulgaria

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    This executive summary describes the methodology for assessing the favourable conservation status of N2000 habitats and species on site level in Bulgaria and gives guidelines for its application. The methodology was developed in the frame of the BBI/Matra project 2006/014 “Favourable Conservation Status of Natura 2000 Habitat types and Species in Bulgaria”. The project was generously supported by the Dutch government under the BBI/Matra programme, which is a combination of two international policy programs of the Dutch government. The objectives and financial resources of the BBI/Matra Programme fall within the remit of the Matra Social Transformation Program of the Ministry of Foreign Affairs and under the International Policy Program on Biodiversity of the Ministry of Agriculture, Nature and Food Quality

    GM1 Softens POPC Membranes and Induces the Formation of Micron-Sized Domains

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    The influence of the glycolipid GM1 on the physical properties of POPC membranes was studied systematically by using different methods applied to giant and large unilamellar vesicles. The charge per GM1 molecule in the membrane was estimated from electrophoretic mobility measurements. Optical microscopy and differential scanning calorimetry were employed to construct a partial phase diagram of the GM1/POPC system. At room temperature, phase separation in the membrane was detected for GM1 fractions at and above ∼5 mol %, whereby GM1-rich gel-like domains were observed by fluorescent microscopy. Fluctuation analysis, vesicle electrodeformation, and micropipette aspiration were used to assess the bending rigidity of the membrane as a function of GM1 content. In the fluid phase, GM1 was shown to strongly soften the bilayer. In the region of coexistence of fluid and gel-like domains, the micropipette aspiration technique allowed measurements of the bending rigidity of the fluid phase only, whereas electrodeformation and fluctuation analysis were affected by the presence of the gel-phase domains. The observation that GM1 decreased the bilayer bending rigidity is important for understanding the role of this ganglioside in the flexibility of neuronal membranes

    Autophagosome closure requires membrane scission

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    Giant unilamellar vesicles formed by hybrid films of agarose and lipids display altered mechanical properties

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    AbstractGiant unilamellar vesicles (GUVs) are presumably the current most popular biomimetic membrane model. Preparation of GUVs in physiological conditions using the classical electroformation method is challenging. To circumvent these difficulties, a new method was recently reported, by which GUVs spontaneously swell from hybrid films of agarose and lipids. However, agarose is left encapsulated in the vesicles in different amounts. In this work, we thoroughly characterize the mechanical properties of these agarose-GUVs in response to electric pulses, which induce vesicle deformation and can lead to membrane poration. We show that the relaxation dynamics of deformed vesicles, both in the presence and absence of poration, is significantly slowed down for agarose-GUVs when compared to agarose-free GUVs. In the presence of poration, agarose polymers prevent complete pore closure and lead to high membrane permeability. A fraction of the vesicles were found to encapsulate agarose in the form of a gel-like meshwork. These vesicles rupture and open up after electroporation and the meshwork is expelled through a macropore. When the agarose-GUVs are heated above the melting temperature of agarose for 2 h before use, vesicle response is (partially) recovered due to substantial release of encapsulated agarose during temperature treatment. Our findings reveal potential artifactual behavior of agarose-GUVs in processes involving morphological changes in the membrane as well as poration
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