Dresden 2017 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 29: Polymer Networks and Dynamics III: Mechanical Properties

CPP 29.8: Vortrag

Dienstag, 21. März 2017, 15:45–16:00, ZEU 250

Determination of biases in equilibrium free-energy estimations from single-molecule unbinding experimentsThomas Utzig1, Philipp Stock1,2, Laila Moreno Ostertag1, and •Markus Valtiner1,21Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf, Germany — 2TU Bergakademie Freiberg, Freiberg, Germany

The capabilities of Atomic Force Microscopes to probe bond rupture at a molecular level are widely appreciated. These measurements are carried out unidirectional under non-equilibrium conditions. Jarzynski's equality (JE) has proven useful to relate the work obtained along these events to the underlying free energy of the unfolding or unbinding process. It has been also pointed out that the free energies can be biased due to finite sampling of work trajectories and dominance of rare events. Here, we present an experimental approach to quantify and correct errors arising from application of JE to single-molecule unbinding at interfaces. In particular we probe the amine/gold bond as a function of the linker's length which is used to immobilize the amine on a flat surface. With increasing linker length we observe an increase in the average work spent on unfolding and bond rupture. Also interaction energies calculated using JE increase if longer linkers are used. Our data demonstrate that the energy stored within the stretched molecule influences single molecule experiments. Further we show how these influences can be quantified, providing important design aspects for single-molecule AFM experiments.

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