ABSTRACT
The atomic force microscope is currently used in our and many other laboratories to measure the mechanical response of polypeptide and proteins against tensile forces applied to well defined positions in their chemical structures. The resulting force vs. extension (F-E) curves are analyzed in relation to their known conformations under various conditions. The method can be extended to study the mechanical responses of other, often much larger biological structures, and extract the component proteins and DNAs from cell membranes and chromosomes.
ABSTRACT
To design protein- and polymer-based micro-machineries, it is important to understand the mechanical properties of basic structural elements such as the alpha-helix of polypeptides. We employed the force measurement mode of an atomic force microscope (AFM) to investigate the spring mechanics of poly-L-glutamic acid (PGA) in its helical and randomly coiled states. After covalently anchoring the polypeptide between a silicon substrate and an AFM tip, the force required to stretch the polymer was measured. The results indicated that PGA in its helical conformation could be stretched almost fully with a continuous increase in the stretching force, suggesting that it can be used as a reliable coil-spring in the future design of spring-loaded molecular machineries.