Supramolecular complex of cytochrome c with lariat ether: Solubilization, redox behavior and catalytic activity of cytochrome c in methanol

A variety of lariat ethers were employed to solubilize water-soluble cytoch rome c in methanol, in which alcohol, ether, ester, amine, and amide functi onalities were attached as cation-ligating side arms to 18-crown-6, 15-crow n-5, and 12-crown-4 rings. Among these lariat ethers, the alcohol-armed 18- crown-6 derivative offered the highest solubilization efficiency for cytoch rome c via supramolecular complexation. The resulting cytochrome c-lariat e ther complexes were electrochemically and spectroscopically characterized a nd confirmed to have redox-active heme structures of 6-coordinate low-spin population in methanol. Some of them catalyzed the oxidation of pinacyanol chloride with hydrogen peroxide in methanol and exhibited higher activities than unmodified cytochrome c and its poly(ethylene glycolated) derivative. Since the supramolecular complexation between lariat ether and cytochrome c includes extremely simple procedures, it provides a facile preparation me thod of effective biocatalysts working in organic solvents from metalloprot eins.