Abstract
The energy landscape of proteins folding and unfolding or of ligand-receptor binding can be elucidated by force spectroscopy. Laser tweezers has excellent force resolution (∼10 fN/sqrt(Hz)) but a low force limit, making it poorly suited for protein pulling. Atomic Force Microscopy has a high force limit but poor force resolution (∼200 fN/sqrt(Hz)) because of viscous interaction of the water with the cantilever. To reduce viscous damping we developed encased cantilevers in which the cantilever is kept dry. Immersed in the solution, surface tension prevents the liquid from entering into the encasement, and only few microns of the tip protrude to interact with the sample in solution. The length of the free cantilever within the encasement is easily controlled during fabrication, hence, ultra short cantilevers with resonance frequencies >1MHz can be fabricated (Figure1, a and b). Thanks to the low damping we achieve quality factors of >100 and minimal detectable forces of 12 fN/sqrt(Hz). The cantilevers can be used in any conventional AFM setup using beam deflection. The low force noise and high force limit make encased cantilevers ideal for force spectroscopy applications.View Large Image | View Hi-Res Image | Download PowerPoint Slide
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