This models the sedimentation velocity of a protein in two conformations, which are initially in an equilibrium governed by the equilibrium constant Keq = [A]/[A*]. The equilibrium constant is dimensionless, but the entry in the parameter box will be in base-10 log. For example, a value of -1 means that in equilibrium A* is 10fold more populated that A, a value of 1 menas that A is 10fold more populated that A*, and a value of 0 means that both are equally populated.
Even though the conformational equilibrium cannot be detected in sedimentation equilibrium, during sedimentation velocity the two forms A and A* may migrate with different rates, s(A) and s(A*), and therefore be disturbed from their initial equilibrium. The boundary shape in such an experiment will depend strongly on the rate constant 'kchange' with which the conformational mixture relaxes back to the equilibrium. Theory predicts that for infinitely slow rate constants sedimentation will be like that of two independent species, while for infinitely fast reactions the sedimentation will proceed like a single species sedimenting at an intermediate s-value.