A Practical Guide to AFM Force Spectroscopy and Data Analysis

_{KEYWORDS: Atomic Force Microscopy; AFM; Force Measurements; Force Curves; Single Molecule; Force Spectroscopy; Data Analysis;}

The atomic force microscope (AFM) is best known for its high-resolution imaging capabilities, but it is also a powerful tool for sensitive force measurements. The AFM can be used to “fish” for single molecules and investigate their structure and biological function. The study of interaction forces with the AFM has led to deeper understanding of many biological and physical processes down to the single molecule level. In AFM “force spectroscopy” experiments, the cantilever and tip are moved directly towards the sample until contact is made, and then retracted again, while the interaction between the tip and the sample is measured. This is repeated at different locations to build a map of the tip-surface interaction or repeated at the same point to give a full statistical understanding of the interaction.

The applications of these experiments range from nanomechanical investigations of elastic properties to protein unfolding and investigations of single chemical bonds. This app note introduces the data collected in force curves and the standard steps that are used in converting the data for a quantitative force analysis.

Readers can expect to learn about:

• The basics of force curve experiments and the interactions that can be measured;
• Different calibration methods and their advantages and disadvantages; and
• The analysis of force curves and applications to determine physical properties such as adhesion, Young's modulus or stiffness.