FIGURE 1.

Diagram of one-dimensional system treated in the Theory section. Three receptors are shown as elongated rectangles with a black steric exclusion zone and a clear exclusion zone, and an arrow to indicate orientation; two are oriented to the right, and one to the left. Three ligands are also shown as hatched rectangles of finite size, although the theory treats them as particles of zero size. Two ligands are oriented to the left and one to the right, and one is bound to the leftmost receptor.