be shown to have unaltered susceptibility to the effect of the uncouplers upon the AjjH'+, are of considerable bioenergetic interest. At least at first blush, their retention of bioenergetic work capacity at submaximal values of the AILH+ appears to represent a departure from the chemiosmotic formulation. In that formulation, the steady-state level of bioenergetic work, represented by, for example, the phosphorylation potential, AG,, is in direct and complete equilibrium with the AlUH+, and the AGpl/AiH+ ratio simply reflects the number of H+ ions translocated per ATP molecule synthesized (17, 25, 26, 55). It is not trivial to rigorously demonstrate that a resistant mutant strain is still fully sensitive to the effect of the agent on the AgIH±. Even in simple artificial systems, protono