Conformational Changes in the Two Subunits

First we focus on the first subunit, say the left-hand one, and ask what is the change in the mole fraction of the L form upon binding of the first ligand. This effect is similar to the one we have studied in section 2.10. We denote by the difference in the mole 

The more difficult question concerns the change in the distribution of the rhs subunit, induced by binding on the Ihs subunit, which is defined as 

We see again, as in the expression for the indirect correlation, that the sign of this quantity depends on both h and r/. A choice of /z 1 (i.e., Ul Uh) does not guarantee a positive value of. To obtain a positive shift for the second subunit (in the sense of 1) we need also that r . In this case the binding of the first ligand shifts the equilibrium concentration of both subunits in favor of the L conformation. Similarly, one can define the effect of the second ligand on equilibrium concentrations of the two subunits. These are 

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