In the experiment shown, the vesicles accumulate [¹⁴C]acetate against about a 100-fold concentration gradient which translates into a DpH (interior alkaline) of –120 mV {a 10-fold gradient is equal to 60 mV (i.e., 2.3RT/F x log₁₀ [acetate]_in/[acetate]_out,); a 100-fold gradient 120 mV; a 1000-fold gradient 180 mV; etc. (each 10-fold increase in the concentration gradient represents one log₁₀ unit increase)}.  Since pH is also expressed in log₁₀ units, a 100-fold gradient of acid at external pH 5.5 means that at this external pH, internal pH is 7.5. 

When the identical experiment is carried out with [³H]TPP⁺, very similar results are obtained, demonstrating that in addition to a DpH of –120 mV, the vesicles also generate a large DY (interior negative) at pH 5.5.  However, in contradistinction to the DpH measurements with [¹⁴C]acetate, when TPP⁺ is used to measure DY, addition of nigericin (NIG) results in further accumulation of the lipophilic cation, while valinomycin (VAL) causes the vesicles to completely release the accumulated cation.  Thus, there is a reciprocal relationship between the pH gradient and the membrane potential which will be discussed below. 

 With inside-out (ISO) vesicles using methylamine accumulation to measure DpH and SCN^- accumulation to measure DY, values similar to those observed in RSO vesicles are obtained, but of course, they are of opposite polarity (i.e., interior acid and positive).