Mimicking the Active Center of Methane-monooxygenase by Metal−Peptide Complexes Immobilized on Mesoporous Silica

The short peptide sequence His-Gly-Gly-Glu, which is found in the active center of methane-monooxygenase, was immobilized on a mesoporous silica support. Self-assembled complexes of the peptide with iron and copper cations were allowed to form. Two methods were used to immobilize the peptide on the support. The peptide was either prepared on a solid-phase peptide synthesizer and then grafted on the silica support, or the peptide chain was grown directly on the silica support by a manual step-by-step synthesis. The latter method allowed us to immobilize more peptide on the support, but similar complexes were formed in both methods. Characterization by UV−vis and EXAFS showed that the Cu2+ cations were coordinated by two histidine residues originating from neighboring peptide chains and additional N/O ligands from the peptide. The complexes were tested in the oxidation of cyclohexane by H2O2. Activity and selectivity were modest, but higher than those of immobilized metal complexes with single amino acids.