Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 19: Biosensors and Biofunctionalized Systems

BP 19.5: Talk

Wednesday, March 28, 2007, 16:30–16:45, H43

Desorption of Spider Silk Proteins from Surfaces with an AFM studied by Molecular Dynamics — •Dominik Horinek and Roland Netz — Physik Department, Technische Universität München, 85748 Garching

Protein adsorption is important in many biological phenomena like biomineralization or cardiovascular diseases. This adsorption is governed by electrostatic forces, and by nonelectrostatic dispersion and hydrophobic forces. Recently, it was discovered that polymer adsorption is dominated by nonelectrostatic contributions even for charged substrates. We present classical molecular dynamics simulations of protein adsorption, which account for electrostatics, dispersion, and hydrophobic forces.

Spider silk proteins, which do not form secondary structure in solution, are good model compounds for computer simulation studies of protein-surface interactions. We study the desorption of spider silk proteins from hydrophobic and hydrophilic surfaces with an AFM with different pulling rates. On hydrophobic surfaces, we show that equilibrium desorption forces can be calculated by molecular dynamics, whereas thermal equilibrium is not reached when pulling off a hydrophilic surface.

We compare our modeling results with recent AFM experiments. The equilibrium desorption forces are analyzed in the context of hydrophobic and van der Waals forces, which are important for phenomena like protein folding. We also discuss friction effects, which are seen for fast pulling rates.