This article describes the application of the fastest commercially available video-rate atomic force microscope (AFM) for studying the molecular dynamics of biological samples with a temporal resolution reaching 20 ms per frame. High-speed AFM was used for monitoring the kinetics of the temperature-induced ripple phase transition in supported lipid bilayers, DNA origami streptavidin-biotin binding, thermodynamic rehybridization of DNA, collagen type I fibrillogenesis, and the mobile annexin V trimer dynamics in 2D protein crystals. With no further need for sample processing, the applied method offers a breakthrough in molecular and sample dynamics measurements by enabling the real-time visualization of molecular processes and structural transitions at near-native conditions.

It has been theoretically predicted that a polymer chain in poor solvent conditions undergoes a phase transition from a collapsed globule to a stretched coil. In this paper, we present force-distance curves, obtained by atomic force microscopy (AFM), showing the characteristic forceplateau associated with this transition. We show that the magnitude of the force depends on the environment (interfacial energy) that the stretched coil experiences when it is pulled-out as it is predicted by the theory.