Synthesis, characterization, and catalytic activity of de novo designed metalloproteins

This thesis describes the design and synthesis of a four-helix protein capable of binding a catalytically active transition metal complex via phosphite ligation. We developed a novel in situ method for the phosphite-modification of de novo designed synthetic proteins and native proteins. Using this method cytochrome b562, a natural protein with surface tyrosine residues, was easily modified as its phosphite. A synthetic protein (Yc-27)4 was designed with tyrosine residues that were modified into phosphites. The phosphite-modified protein (Yc-27-DEP) 4 has tyrosine residues in appropriate positions for metal ligation. Another four-helix protein (Yc-26)4 with tyrosine residues was also synthesized and modified as its phosphite (Yc-26-DEP)4. Both (Yc-27-DEP)4 and (Yc-26-DEP)4 were reacted with the catalytically active rhodium complex RhClPPh3 to form the metalloproteins (Yc-27-DEP)4-Rh and (Yc-26-DEP)4-Rh respectively. These metalloproteins were tested for catalytic activity in the hydrogenation of small olefins. The metalloprotein, (Yc-26-DEP)4-Rh, was found to catalyze the hydrogenation of olefins such as cyclohexene, alpha-methylstyrene, and (R)-carvone. The hydrogenation of the chiral (R)-carvone using (Yc-26-DEP) 4-Rh demonstrated that the metalloprotein is more reactive than Wilkinson's catalyst. However, the hydrogenation of the ring unsaturation in (R)-carvone by the metalloprotein indicated that it is less regioselective than Wilkinson's catalyst.