Figure 5.

(a) The PCM exerts a force on optically trapped stationary beads. We infer, based on our data, that the equilibrium force arises from molecular concentration gradients in the cell coat. This equilibrium force, F_eq, increases exponentially toward the cell surface with an exponent c = 0.50 ± 0.04 μm⁻¹ (red curve). The plot shows the equilibrium force curve from a single-cell measurement, with SD error bars. (b) The correlation length, or mesh size, in the PCM increases exponentially away from the cell surface (the prefactor is set to one). This result relies on our experimental assessment that the probe particles penetrate rather than compress the PCM, and that the measured equilibrium force arises from an osmotic pressure gradient.