Fig. 4. Force extension curves of DNA for each magnet configuration and bead size. (A) A vertical magnet configuration and 1 μm beads. (B) A lateral magnet configuration and 1 μm beads. (C) A vertical magnet configuration and 2.8 μm beads. (D) A lateral magnet configuration and 2.8 μm beads. Data were obtained for λ/2 DNA molecules and from flow cells of one or two layers of parafilm or from glass capillaries. Force–extension data were fitted to the worm-like chain model (solid line). Fitting parameters are shown in Table 2. Error bars are the standard error of the mean.