(1) A protein which contains a flavin cofactor has a two-electron reduction midpoint potential of -190 mV vs NHE at pH 7. The active site of this protein binds a molecule of benzoate with a dissociation constant Kd of 88 μM when the protein is oxidized. In the presence of saturating benzoate, the midpoint potential decreases to -250.

a) Draw the thermodynamic box which describes these interactions.

b) Calculate the energy in kcal/mol of each known side of the box.

c) What is the dissociation constant of benzoic acid to the reduced protein?