Formulation and some biological uses of a buffer mixture whose buffering capacity is relatively independent of pH in the range pH 4-9

A mixture is described which has a buffering capacity which is essentially independent of pH in the range pH 4.0-9.0. It is shown how this buffer mixture may be used to determine the force-flux relationship of proton transfer between two aqueous phases separated by a phospholipid bilayer in vesicular systems and so demonstrate that this relationship is linear over a wide range of delta mu approximately H+. The buffer mixture can, furthermore, be employed to determine the volume enclosed within a vesicular preparation.