Fig. 3. Diffusional, ^DJ_H, and facilitated, ^FJ_H, components of total flux, ^TJ_H, are affected differently by increasing concentrations of the Good buffer MES.  An artificial source of protons is scanned with the same probe in different bath solution buffer concentrations.  Note the increased steepness of the diffusional flux curves as the buffer strength is increased from 60 µM to 1.5 mM MES (inset labels).  The only significant facilitated diffusion is detected at the high buffer concentration and at this concentration the diffusional flux is all but extinguished.  Flux is given in picomoles per cm² per sec. The bath solutions used included: x µM MES, 100 µM KCl, 200 mM Sucrose.  The artificial source consisted of a capillary drawn to a 2 µm opening, filled with bath solution which lacked buffer, was adjusted to 0.01 N HCl and gelled with 0.08% agarose.