Note that ∆G 1 (pH) and ∆G 2 (pH) act on the "reactants" and "products" of the upper branch in Figure : a more favorable ∆G 1 (pH) will increase ∆∆G 0 while a more favorable ∆G 2 (pH) will decrease ∆∆G 0 , and vice-versa. here, pK • a corresponds to the reference pK a of residue A.