Dresden 2017 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 3: Computational Biophysics (joint BP/DY)

DY 3.6: Talk

Monday, March 20, 2017, 11:15–11:30, ZEU 250

Adsorption, binding motifs and structural change of proteins on silica studied by Molecular Dynamics — •Nils Hildebrand, Monika Michaelis, Susan Köppen, and Lucio Colombi Ciacchi — Bremen Center for Computational Materials Science, Bremen

The physisorption of chymotrypsin and lysozyme on amorphous silica is investigated by classical Molecular Dynamics (MD) methods in comparison to adsorption and circular dichroism (CD) experiments. The long-range protein-surface attraction field is calculated in an implicit solvent based on DLVO theory. These calculations reveal a preferred protein orientation, which could be confirmed in explicit solvent simulations. Driven by its large dipole moment, chymotrypsin adsorbs with its alpha-helical regions pointing towards the surface. Lysozyme adsorbs in a side-on orientation. Positively charged hydrophilic residues form dominant binding motifs by adsorbing in dense water layers around the deprotonated silanol surface groups. The amount of adsorbed proteins found in the experiment can be explained by a combination of the binding motifs stability and protein-protein interactions. No significant conformational changes are observed in MD simulations lasting 300 ns. In order to capture surface-induced conformational changes revealed by CD experiments, parallel tempering in combination with metadynamics is employed. In these simulations, the helical content of chymotrypsin is used as a reaction coordinate, as helical unfolding is believe to strengthen the adhesion to the surface.