Endogenous Ca²⁺ buffer properties from nerve terminals with two endogenous buffers, where either both components appear to have undetectable mobility (top row) or the higher-affinity buffer has a significantly higher mobility (bottom row). K_d,e1, B_T,e1, K_d,e2, B_T,e2, and τ were determined by fitting to Eq. 2, with the inclusion of an exponential factor multiplying [B_e1] and allowing the time constant to vary. V_A and [Ca²⁺]_Free,0 were as described in Table 1. τ gives the time constant for exponential decay of the concentration of the high-affinity endogenous buffer by diffusion into the patch pipette. For the top row, no washout could be detected. The fitting yielded a value for τ indistinguishable from zero.