Fast imaging and fast force spectroscopy of single biopolymers with a new atomic force microscope designed for small cantilevers

Abstract

Small cantilevers allow for faster imaging and faster force spectroscopy of single biopolymers than previously possible because they have higher resonant frequencies and lower coefficients of viscous damping. We have used a new prototype atomic force microscope with small cantilevers to produce stable tapping-mode images ͑1 mϫ1 m͒ in liquid of DNA adsorbed onto mica in as little as 1.7 s per image. We have also used these cantilevers to observe the forced unfolding of individual titin molecules on a time scale an order of magnitude faster than previously reported. These experiments demonstrate that a new generation of atomic force microscopes using small cantilevers will enable us to study biological processes with greater time resolution. Furthermore, these instruments allow us to narrow the gap in time between results from force spectroscopy experiments and molecular dynamics calculations.

Electrostatic complexation of spheres and chains under elastic stress

“…Here one might expect that beads are released with increasing strain in order to have the remaining beads close to their optimal wrapping length -resulting in a ''saw-tooth-like'' force-extension curve of the type recently encountered for the tension-induced denaturation of the linear macromolecule titin. 17,18 Again, our finding comes as a surprise: The chain simultaneously unwraps all the beads in parallel and there is no sequential release.…”

Force measurements with the atomic force microscope: Technique, interpretation and applications

“…They are made of aluminum or silicon nitride, leading to resonance frequencies of typically 2 MHz in air. The size of cantilevers cannot be made much smaller because it becomes more and more difficult to fabricate the tips and to focus the laser beam onto such small structures [44]. Also the aperture of the lens in the incident laser beam path has to be adjusted to the cantilever size to achieve an optimal signal-to-noise ratio [46].…”

“…Only short and thin cantilevers are soft, have a high sensitivity and a high resonance frequency. Accordingly, several researchers aim to make even smaller cantilevers with higher resonance frequency [43][44][45]. The smallest cantilevers are %10 mm long, 0.1-0.3 mm thick and 3-5 mm wide.…”

High-Resolution Imaging of Myosin Motor in Action by a High-Speed Atomic Force Microscope

“…Therefore, we need alternative guidelines for fabricating a high-speed scanner. Several laboratories throughout the world have been trying to develop a high-speed AFM (Sulcheck et al, 2000;Viani et al, 1999). They must also have encountered the greatest difficulty when making a high-speed scanner.…”