Figure S4. Slow-exchanging molecules can... | Rockefeller University Press

Figure S4.

$Slow-exchanging molecules can dominate the membrane-associated pool of molecules and define the response of the system to cortical flows even if constituting a minority of membrane binding events. To assess the response of a system with a mixture of fast- and slow-exchanging molecules to advective transport, we modified the model in Fig. 6 to allow molecules that bind to the membrane to exhibit a mix of membrane-bound lifetimes: short (fast-exchanging, koff, fast) and long (slow-exchanging, koff,slow). Fast events were fixed at koff, fast = 1 s−1 and koff,slow varied. (A and B) The relative membrane fraction constituted by fast-exchanging molecules (A) and the overall asymmetry (ASI) achieved at the end of flow (B) are shown as a function of the relative fraction of fast membrane binding events and the relative values of koff, fast and koff,slow. (C) Example traces showing the distribution of fast, slow, and total molecules shown for the indicated fraction of fast events for koff,slow = 10−3 s−1. To briefly summarize, in C, the 1,000-fold-longer persistence of slow-exchanging molecules at the cortex means that they make up the vast majority of molecules at the membrane at any given time even when they constitute only 1% of all membrane binding events. Consequently, the overall asymmetry achieved by advection is dominated by the response of the long-lived species.$

Slow-exchanging molecules can dominate the membrane-associated pool of molecules and define the response of the system to cortical flows even if constituting a minority of membrane binding events. To assess the response of a system with a mixture of fast- and slow-exchanging molecules to advective transport, we modified the model in Fig. 6 to allow molecules that bind to the membrane to exhibit a mix of membrane-bound lifetimes: short (fast-exchanging, k_{off, fast}) and long (slow-exchanging, k_off,slow). Fast events were fixed at k_{off, fast} = 1 s⁻¹ and k_off,slow varied. (A and B) The relative membrane fraction constituted by fast-exchanging molecules (A) and the overall asymmetry (ASI) achieved at the end of flow (B) are shown as a function of the relative fraction of fast membrane binding events and the relative values of k_{off, fast} and k_off,slow. (C) Example traces showing the distribution of fast, slow, and total molecules shown for the indicated fraction of fast events for k_off,slow = 10⁻³ s⁻¹. To briefly summarize, in C, the 1,000-fold-longer persistence of slow-exchanging molecules at the cortex means that they make up the vast majority of molecules at the membrane at any given time even when they constitute only 1% of all membrane binding events. Consequently, the overall asymmetry achieved by advection is dominated by the response of the long-lived species.