Mireille M. A. E. Claessens

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In the presence of condensing agents such as nonadsorbing polymer, multivalent counter ions, and specific bundling proteins, chiral biopolymers typically form bundles with a finite thickness, rather than phase-separating into a polymer-rich phase. Although short-range repulsive interactions or geometrical frustrations are thought to force the equilibrium(More)
Despite their importance for the proper function of living cells, the physical properties of cross-linked actin networks remain poorly understood as the occurrence of heterogeneities hamper a quantitative physical description. The isotropic homogeneously cross-linked actin network presented here enables us to quantitatively relate the network response to a(More)
Bundles of filamentous actin (F-actin) form primary structural components of a broad range of cytoskeletal processes including filopodia, sensory hair cell bristles and microvilli. Actin-binding proteins (ABPs) allow the cell to tailor the dimensions and mechanical properties of the bundles to suit specific biological functions. Therefore, it is important(More)
The mechanical properties of cytoskeletal actin bundles play an essential role in numerous physiological processes, including hearing, fertilization, cell migration, and growth. Cells employ a multitude of actin-binding proteins to actively regulate bundle dimensions and cross-linking properties to suit biological function. The mechanical properties of(More)
The structure and rheology of cytoskeletal networks are regulated by actin binding proteins. Aside from these specific interactions, depletion forces can also alter the properties of cytoskeletal networks. Here we demonstrate that the addition of poly(ethylene glycol) (PEG) as a depletion agent results not only in severe structural changes, but also in(More)
Soluble oligomeric aggregates of alpha-synuclein have been implicated to play a central role in the pathogenesis of Parkinson's disease. Disruption and permeabilization of lipid bilayers by alpha-synuclein oligomers is postulated as a toxic mechanism, but the molecular details controlling the oligomer-membrane interaction are still unknown. Here we show(More)
While actin bundles are used by living cells for structural fortification, the microscopic origin of the elasticity of bundled networks is not understood. Here, we show that above a critical concentration of the actin binding protein fascin, a solution of actin filaments organizes into a pure network of bundles. While the elasticity of weakly cross-linked(More)
Although the structure of cross-linking molecules mainly determines the structural organization of actin filaments and with that the static elastic properties of the cytoskeleton, it is largely unknown how the biochemical characteristics of transiently cross-linking proteins (actin-binding proteins (ABPs)) affect the viscoelasticity of actin networks. In(More)
The osmotic shrinkage of giant unilamellar dioleoylphosphatidylglycerol (DOPG) vesicles in a hypertonic osmotic solution is investigated. The volume reduction for given membrane area leads to a vesiculation of the bilayer into the interior of the giant. The size of the daughter vesicles that appear inside the giant is uniform and an increasing function of(More)
We have studied the phase behavior of zwitterionic phospholipid dioleoylphosphatidylcholine (DOPC) vesicles (membranes) and interpreted our results using scaling arguments in combination with molecular realistic self-consistent field (SCF) calculations. DOPC membranes acquire a partial negative charge per lipid molecule at intermediate NaBr concentrations.(More)