Hydrophobic Interactions in Metalloporphyrin−Peptide Complexes

Synthetic heme−oligopeptide complexes of coproporphyrin-I-atoiron(III) have been prepared in aqueous solution, and their equilibrium formation constants have been determined by spectrophotometric titration. The presence of hydrophobic residues flanking the coordinated histidine dramatically increase peptide binding to the heme by more than 20 kJ/mol.