Figure 2.

Mini-radio centrifuge force microscope (MR.CFM) and collagen tethering. (a) Photograph of the microscope, with the centrifuge bucket insert at the bottom and a sample chamber leaning at the side. The height of the assembly is <16 cm and its mass is 421 g. (b) Schematic of the optical elements within the microscope. A force F = mω²r is exerted on all beads of relative mass m within the sample chamber, located a distance r from the central rotation axis, when the rotor spins at angular frequency ω. (c) Image of microspheres subjected to 9 pN of force in MR.CFM, tethered to the surface by collagen molecules. Although each bead occupies only a few pixels in the final image, they are easily detected. (d) Schematic of tethering geometry. Single molecules of collagen are tethered to a glass slide via biotin-streptavidin linkages, and are covalently linked to the surface of heavy beads via thiol-amine coupling. To see this figure in color, go online.