Combinatorial Synthesis of Four-Helix Bundle Hemoproteins for Tuning of Cofactor Properties.

De novo proteins were assembled from two sets of helical peptides on cyclic peptide templates bound to cellulose membranes (see picture). The variation of the amino acids of the hydrophobic binding pocket in the antiparallel four-helix bundle tuned the redox potential of the reversibly bound Fe(III) - protoporphyrin IX group, as directly detected spectroscopically on the solid support.