Conformational equilibria of hemeproteins will be studied as a function of variation at the metal site. Specific variations involving metal substitution, ligand substitution, and porphyrin variations will be included. Studies will encompass both evaluation of internal conformation energies of myoglobins and allosteric (RET) transitions in hemoglobin derivatives. Finally, work will proceed on the evaluation of a "thermodynamic model" for the control of catabolism.