At 0 µM calbindin, 10% to 90% rise time was 2.09 ms, whereas at 200 µM it was 1.98 ms. This was expected from the fact that both mobile buffers are too slow to affect rise-times (see kon's in Table 2 and Figure 5D).
In Fig. 1 (left panel, dashed line), the expected concentration of a Ca2+ ion experienced by a nearby tentative mobile buffer is plotted.
The binding probability for a Ca2+ ion near to a mobile receptor, i.e., a mobile buffer, was modeled in the same way as for the stationary receptor, with one exception.
Our average value for the speed at which a depolarisation-induced Ca2+ transient flows from the periphery to the centre of a nerve cell with no added mobile buffer was ∼6 μm s−1.
In the model, mobile endogenous buffers were not included.
The following mobile phase buffers were used for separation of carbohydrates: Buffer A, 15 mM NaOH, and Buffer B, 50 mM NaOH/1 M sodium acetate.
Possibly the ratio of mobile buffers to immobile buffers is higher in large snail neurones, or the diffusion coefficient of the mobile buffer fraction is much higher than in other cells.
It is very likely that mobile endogenous calcium buffers were washed out during whole cell recording, even from small compartments such as spines [28].
Therefore, it is very likely that mobile endogenous calcium buffers were washed out at the start of imaging, even from small compartments such as spines and presynaptic terminals [28].
Ca2+ diffusion and binding to mobile and fixed buffers were modeled using the full set of partial differential equations (PDEs) of the reaction diffusion problem, including all necessary boundary and initial conditions (Smith, 2001; Bucurenciu et al., 2008; Eggermann and Jonas, 2012; Vyleta and Jonas, 2014).
