FIGURE 8.

Hybrid model results. We have found a simplified model that depends on only two parameters, D_f / and k_off, which provides a good fit (sum of residuals <1) to the full model when k_off ≪ (area above solid line; D_f = 30 μm²/s, w = 0.5 μm). This hybrid model describes the crossover between the reaction and effective diffusion regimes (compare to Fig. 3 C), and mathematically reduces to either the reaction dominant equation or the effective diffusion equation with small or large, respectively. Practically, the hybrid model demonstrates that a large portion (shaded area) of the previously identified full-model-only zone (see Fig. 3 C) is dependent on only two parameters: D_f / and k_off. Therefore it is important that D_f be determined before attempting to extract the rate constants from the full model.