Single Molecule Force Spectroscopy with the ForceRobot® 300

Introduction

The atomic force microscope (AFM) allows imaging or manipulation of materials ranging from individual molecules such as DNA and proteins to whole cells. The sensitive force detection and control have naturally led to a range of experiments where single molecules are investigated without lateral scanning or imaging. These force spectroscopy experiments probe the response of the molecule over a spectrum of forces. Single-molecule force spectroscopy enables the investigation of internal molecular properties such as backbone elasticity and length or intramolecular binding, for example protein unfolding. The binding and interactions between molecules can also be probed, as intermolecular binding, for instance ligand-receptor or DNA hybridization [1]. It can even be possible to differentiate ligand and inhibitor binding to membrane proteins on the basis of their unfolding signatures [2]. By varying the experimental parameters, the kinetics and energy landscape of the binding can also be measured [3].

Single molecule force spectroscopy (SMFS) places particular demands on the instrument, leading to the development of the ForceRobot®300 as a dedicated force spectroscope. The requirements partly overlap with those of a high-quality atomic force microscope, such as high-precision piezo elements and sensitive, low-noise detection systems. The positioning and deflection detection of the cantilever at the sub-nanometer precision are a prerequisite for high-quality force experiments. Other requirements are specific to the force spectroscopy experiments, because of the demands of working with individual molecules.