Induced Conformational Changes in the Two Subunits

Let us first examine the subunit on which the first ligand binds, say the left-hand one. We denote by the change in the mole fraction of the L form, in the left-hand 

The quantity P(L /I 0) denotes the conditional probability of finding the left subunit in state L, given that the left subunit is occupied and the right subunit is empty. Therefore, is the difference in the probabilities (or mole fractions) of the left-hand subunit being in state L, before and after the binding on the left subunit [the sums in Eq. (4.7.27) are over a = L,H and P = L, H], 

In terms of the notation of Section 4.7.3, this quantity can be written as 

We see that the sign of is determined only by (1 - h). It is positive when h I, i.e., the ligands prefer to bind on L. Note that when q = 1 and K=K, this reduces to the quantity d in Section 3.4. 

The second quantity of interest, denoted by is the change in the mole fraction of L in the second subunit (or the right-hand one) induced by binding on the first subunit (the left-hand one). This quantity is defined by 

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