Publications (8)53.95 Total impact
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Article: Forced desorption of polymers from interfaces
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ABSTRACT: In the past decade it has become possible to directly measure the adsorption force of a polymer in contact with a solid surface using single-molecule force spectroscopy. A plateau force in the force–extension curve is often observed in systems of physisorbed or noncovalently bonded polymers. If a molecule is pulled quickly compared to internal relaxation, then nonequilibrium effects can be observed. Here we investigate these effects using statistical mechanical models and experiments with a spider silk polypeptide. We present evidence that most experiments showing plateau forces are done out of equilibrium. We find that the dominant nonequilibrium effect is that the detachment height hmax(v) increases with pulling speed v. Based on a nonequilibrium model within a master-equation approach, we show the sigmoidal dependence of the detachment height on the pulling speed of the cantilever, agreeing with experimental data on a spider silk polypeptide. We also show that the slope with which the plateau forces detach is given by the cantilever force constant in both theory and experiment.New Journal of Physics 01/2011; 13(1):013025. · 4.18 Impact Factor -
Article: Controlling the Structure of Proteins at Surfaces.
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ABSTRACT: With the help of single molecule force spectroscopy and molecular dynamics simulations, we determine the surface-induced structure of a single engineered spider silk protein. An amyloid like structure is induced in the vicinity of a surface with high surface energy and can be prohibited in the presence of a hydrophobic surface. The derived molecular energy landscapes highlight the role of single silk protein structure for the macroscopic toughness of spider silk.Journal of the American Chemical Society 11/2010; · 9.91 Impact Factor -
Article: Pulling a single polymer molecule off a substrate reveals the binding thermodynamics of cosolutes.
Angewandte Chemie International Edition 06/2010; 49(28):4730-3. · 13.45 Impact Factor -
Article: Aging of hydrogenated and oxidized diamond.
Advanced Materials 01/2010; 22(3):398-402. · 13.88 Impact Factor -
Article: Single Molecule Adhesion Mechanics on Rough Surfaces
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ABSTRACT: The nanostructure of materials is supposed to affect polymer adhesion at the solid/liquid interface by variations of the exposed surface area. In contrast, our studies on the nanotribology of single recombinant spider silk proteins onto smooth and rough surfaces made of surgical stainless steel show no effect of the surface morphology. This is explained by the velocity dependence of the desorption process, which reveals a negligible friction and a high in-plane mobility at the molecular scale. We compare our results to all atomistic molecular dynamics simulations that allow estimating an upper limit for the molecular friction coefficient.11/2009; -
Article: Polymer adhesion at the solid-liquid interface probed by a single-molecule force sensor.
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ABSTRACT: A method based on atomic force microscopy is used to delineate the properties that determine single-molecule adhesion onto solid substrates in aqueous environment. Hydrophobicity as well as electrical properties of the substrate and the polymer are varied. In addition, the influence of the solvent composition, in particular the effect of ions, on the molecular adhesion at the solid-liquid interface is studied. Surprisingly, the polymer and surface-related properties account for only small changes in adhesion force, while dissolved ions show a much larger effect. These results point towards the energy of solvation as the most important contribution to adhesion for a wide variety of polymers and substrate materials.Small 10/2009; 5(24):2864-9. · 8.35 Impact Factor -
Article: Hydrophobic and Hofmeister effects on the adhesion of spider silk proteins onto solid substrates: an AFM-based single-molecule study.
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ABSTRACT: AFM-based single-molecule force spectroscopy has been used to study the effect of Hofmeister salts and protein hydrophobicity on the adhesion of recombinant spider silk proteins onto solid substrates. Therefore, a molecular probe consisting of a spider silk protein and an AFM tip has been developed, which (i) is a well-defined, small system that can be simulated by molecular dynamics simulations, (ii) allows access to the whole soluble concentration range for ions, and (iii) provides the distribution of desorption forces rather than just ensemble-averaged mean values. The measured desorption forces follow the Hofmeister series for anions (H2PO4-, Cl-, I-) with a stabilizing energy of more than 15 kBT for 5 M NaH2PO4. Moreover, this effect is influenced by the hydrophobicity of the spider silk protein, indicating that hydrophobic and Hofmeister effects are closely related.Langmuir 03/2008; 24(4):1350-5. · 4.19 Impact Factor -
Article: Single Molecule Sensors to Study Hydrophobic Phenomena
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ABSTRACT: Die Art und Stärke der hydrophoben Wechselwirkung ist entscheidend für zahlreiche technische und biologische Prozesse. Um diese Vorgänge auf der Ebene einzelner Moleküle studieren zu können, wurde in dieser Arbeit eine molekulare Sonde entwickelt, die aus einem einzelnen Polymer besteht, das an die Spitze einer AFM Blattfeder angebunden wird. Im Folgenden werden Gleichgewichtskräfte zwischen dem Sondenpolymer und unterschiedlichen Fest/Flüssig Grenzschichten gemessen und dabei Einflussfaktoren wie Temperatur, Lösungszusätze oder chemische Beschaffenheit von Molekül und Grenzfläche unabhängig voneinander variiert. Dabei ist das Messsystem so klein, das es mit atomistischen Molekulardynamik Simulationen verglichen werden kann.
Top co-authors
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Institutions
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2008–2011
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University of Technology Munich
- • Center for Integrated Protein Science Munich (CIPSM)
- • Walter Schottky Institut (WSI)
München, Bavaria, Germany
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