New approaches to reveal quantitative free energy landscapes in molecular interactions by single molecule force spectroscopy

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New approaches for performing and analysing single molecule force measurements are proposed and will be applied to intermolecular (e.g. protein-ligand or metal chelating complexes) and to intramolecular interactions as observed in protein folding and unfolding processes. Both, the data analysis procedures and the existing design of force spectroscopic experiments for intermolecular measurements will be improved. Specifically, here it is required to allow for unlimited repetition of the experiment on one and the same molecule to avoid artefacts originating from an uncontrolled angle between pulling direction and surface as well as unspecific and multiple interactions. The strategy applied overcomes the existing experimental obstacles by the design of a polymer scaffold on which the interaction partners can be specifically bound in a defined geometry. The data analysis procedures developed in our group, which give force dependent off-rates will be improved to include complex free energy landscapes which show a curvature and roughness around the bound and the transition state. Force dependent free activation energies and exponential prefactors in the Arrhenius equation will be obtained from temperature dependent force measurements. Rigorous statistical error analysis of the experimental results will allow for quantitative model testing for free energy landscapes.