FIGURE A1.
PMN surface indentation in the absence of divalent cations. (Left) Data of force versus indentation distance measured with large diameter probe tips, 3.5 ± 0.05 μm. (Right) Data of force versus indentation distance measured with small diameter probe tips, 2.3 ± 0.08 μm. The mean stiffnesses derived for indentation of the PMN interface are kcomp = 0.15 and 0.16 pN/nm respectively. The double-ended arrows in the right figure illustrate the expected resolution in force set by a probe spring constant of 0.5 pN/nm and ∼±5 nm errors in the tracking of bead displacements.