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Schroder, André

CNRS Scientist

Saturday 12 July 2008, by mcube members


Tel : +33 (0)388414057
Fax : +33 (0)388414099
email: schroder[at]unistra.fr

Research activities

1-GUVs grow through bulge merging exclusively

Electroformation is well known and widely used to grow Giant Unilamellar Vesicles from a hydrated, surface spread, pre-oriented phospholipid film. We have shown, using dual probe labelling and electroformation in presence of first generation GUVs or LUVs, that GUVs grow from the spread stack without any membrane fusion event. Hence, merging of connected buds is now proven to be the only mechanism at play during GUV growing.

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2-Hydroperoxydation-induced lipid area increase
 (in bilayer geometry)

Hydroperoxidation of a phospholipid tail through a chemical reaction with a singlet oxygen 1O2 leads to the grafting of an OOH group per insaturation. When embedded in a bilayer oxidized lipids adopt a specific conformation, i.e. their OOH-bearing chain(s) tend to kink, positioning the OOH group closer to the water interface. We measured for the first time the average area increase of DOPC (≈18%) and POPC (≈14%) bilayers upon hydroperoxidation, using wether micropipette aspiration, or Reflexion Interference Contrast microscopy. Our data have been confirmed by numerical simulations.

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3-Grafted DNA stretching and confinement 
under an adhered phospholipid membrane

Single-end and double-end surface grafted λ-DNAs are pushed away, stretched and stapled during biotin-streptavidin mediated adhesion of a Giant Unilamellar Vesicle. At the end of the process the stretched DNAs remain confined in a membrane-substrate tunel, in a highly, close to fully stretched state. Interestingly the final shapes of the confined DNAs reveal that the two arms of a double-end grafted DNA are first radially stretched during the GUV adhesion process, as if they were independant, single-end grafted DNAs, up to a point corresponding on average to a degree of stretching of 0.5 of the DNA chain (1.0 corresponding to a fully stretched chain). Only at that point does the DNA chain start to adopt a loop shape.

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