FIGURE 1.

Description of the BFP experiment with DNA strands. The spring is a red blood cell whose tension is controlled by the aspiration in the pipette holding it (left pipette). A glass bead coated with DNA strands is attached to this red cell. The DNA is bound to the bead by single streptavidin-biotin bonds. The other pipette holds aggregates of latex particles that nonspecifically bind to the DNA strands. When the glass bead and the latex particles are brought in contact, the DNA strongly attaches to the latex particles. Upon separation, the streptavidin-biotin bond is the first one to unbind. This protocol allows the measurements of rupture forces of bonds that have been given several hours to form.