Showing papers by "Udo Seifert published in 2002"
TL;DR: Giant vesicles prepared from the diblock copolymer polybutadien-b-polyethyleneoxide (PB-PEO) exhibit a shear surface viscosity, which is about 500 times higher than those found in common phospholipid bilayers, and this result constitutes the first direct measurement of the shear Surface Viscosity of such polymersomes.
Abstract: Giant vesicles prepared from the diblock copolymer polybutadien-b-polyethyleneoxide (PB-PEO) exhibit a shear surface viscosity, which is about 500 times higher than those found in common phospholipid bilayers. Our result constitutes the first direct measurement of the shear surface viscosity of such polymersomes. At the same time, we measure bending and stretching elastic constants, which fall in the range of values typical for lipid membranes. Pulling out a tether from an immobilized polymersome and following its relaxation back to the vesicle body provides an estimate of the viscous coupling between the two monolayers composing the polymer membrane. The detected intermonolayer friction is about an order of magnitude higher than the characteristic one for phospholipid membranes. Polymersomes are tough vesicles with a high lysis tension. This, together with their robust rheological properties, makes them interesting candidates for a number of technological applications.
126 citations
TL;DR: In this paper, the dynamical strength of adhesion molecules under a time-dependent force is studied theoretically using analytical and numerical methods, and on-and off-rates are calculated self-consistently using the full potential rather than the usual linear approximation.
Abstract: The dynamical strength of adhesion molecules under a time-dependent force is studied theoretically using analytical and numerical methods. On- and off-rates are calculated self-consistently using the full potential rather than the usual linear approximation. Rebinding events lead to a finite strength at zero loading rate with a subsequent linear increase with loading rate. In the adjacent non-linear regime, the dynamical strength increases more strongly than logarithmically with effective exponents up to about 1/2.
81 citations
TL;DR: The elastic response of a single DNA molecule to an external electric field in two dimensions is investigated and the relaxation of the end-to-end distance from a highly stretched state follows a scaling behavior with a scaling exponent of 0.46 ± 0.8 as expected for diffusive shortening.
Abstract: We investigate the elastic response of a single DNA molecule to an external electric field in two dimensions. DNA is tethered at one extremity to a solid support, confined to two dimensions by the electrostatic interaction with a fluid lipid membrane and directly visualized by fluorescence microscopy. The end-to-end distance of electrophoretically stretched DNA elongates with increasing field strength in good agreement with the worm-like chain model for semiflexible chains adapted to two dimensions. We obtain an effective charge of 0.6 e/nm. The time average contour of the stretched molecule shows a trumpet-like vertical broadening due to thermal fluctuations. Alignment of the membrane-bound DNA is reversible. The relaxation of the end-to-end distance from a highly stretched state follows a scaling behavior with a scaling exponent of 0.46 ± 0.8 as expected for diffusive shortening.
45 citations