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2015
Journal Article
Titel
Estimation of the free energy of adsorption of a polypeptide on amorphous SiO2 from molecular dynamics simulations and force spectroscopy experiments
Abstract
Estimating the free energy of adsorption of materials-binding peptides is fundamental to quantify their interactions across bio/inorganic interfaces, but is difficult to achieve both experimentally and theoretically. We employ a combination of molecular dynamics (MD) simulations and dynamical force-spectroscopy experiments based on atomic force microscopy (AFM) to estimate the free energy of adsorption DGads of a (GCRL) tetrapeptide on amorphous SiO2 in pure water. The results of both equilibrium, advanced sampling MD and non-equilibrium, steered MD are compared with those of two different approaches used to extract DGads from the dependence of experimentally measured adhesion forces on the applied AFM loading rates. In order to obtain unambiguous peak forces and bond loading rates from steered MD trajectories, we have developed a novel numerical protocol based on a piecewise-harmonic fit of the adhesion work profile along each trajectory. The interpretation of the experiments has required a thorough quantitative characterization of the elastic properties of polyethylene glycol linker molecules used to tether (GCRL)15 polypeptides to AFM cantilevers, and of the polypeptide itself. All obtained DGads values fall within a relatively narrow window between −5 and −9 kcal mol−1, but can be associated with large relative error bars of more than 50%. Among the different approaches compared, Replica Exchange with Solute Tempering simulations augmented with MetaDynamics (RESTMetaD) and fitting of dynamic force spectroscopy experiments with the model of Friddle and De Yoreo lead to the most reliable DGads estimates.
Author(s)
Meißner, Robert Horst
Wei, Gang
Hybrid Materials Interfaces Group, Faculty of Production Engineering, Bremen Center for Computational Materials Science and Center for Environmental Research and Sustainable Technology (UFT), University of Bremen