Binary elements model representation. (A) A standard representation of a four element kinetic scheme composed of an agonist-binding site (A), a main gate (m), a desensitization gate (d), and a drug-binding site (D). States are labeled by the bit-wise representation of the element configurations (i.e., “0100” represents the state A₀m₁d₀D₀). Although the model contains 16 states, there are only four transitions into or out of any given state (e.g., circled state and bold transition arrows). (B) A binary elements representation of the same model shown in A, where each element is depicted as a labeled circle and interacting elements are connected by solid lines. This representation is analogous to that used previously to describe systems of linked particles (e.g., Sigg, 2013). Note that not all possible interactions are labeled (e.g., binding sites interact with gates, but not each other).