Predicted efficiency of advective segregation as a function of D and k _off . (A–D) The efficiency of advective segregation of a hypothetical molecule as a function of k_off and D when subjected to an experimentally fit flow profile for a period of 500 s. (A and B) show maximum ASI and relative posterior depletion at the end of 500 s of flow, respectively. (C and D) show the characteristic time (t_1/2) for decay in ASI and posterior depletion after flow ceases. Red circles in A–D indicate example parameter sets approximating the measured behavior of PAR-2 (solid circle, D ∼ 0.1 µm²/s, k_off ∼ 0.005 s⁻¹) along with 10-fold increases or decreases in D and k_off (open circles). Blue circle indicates expected behavior for the PH domain of PLC1δ1, which binds PIP₂ and which we previously have shown does not segregate in embryos (D ∼ 1.0 µm²/s, k_off ∼ 0.1 s⁻¹; Hirani et al., 2019). (E and F) ASI (E) and posterior depletion (F) shown at the end of flow and 300 s later, equivalent to the end of establishment phase and post-NEBD-maintenance phase, respectively, for the example parameter sets denoted in A–D. Note that the magnitude and stability of asymmetry are strongly impacted by 10-fold changes in k_off, but not similar changes in D. (G–I) Example concentration profiles at the end of flow and 300 s post flow for the indicated parameter sets from A–F. The flow velocity function and measured PAR-3 distribution (mean ± SD) at the end of flow are shown for reference. Note that the parameter varied in H and I vs. G is indicated in green, highlighting how reductions in k_off, but not D, improve segregation.