In both CTPR8-C 60 and CTPR8-C 60 A assemblies, the -helical structure of the protein was unaffected by fullerene binding. The CTPR proteins were then reengineered to exert more specific interactions with the fullerene surface. Two additional tyrosine residues were introduced in positions 2 and 9 of the A helix of every repeat, thus positioning two aromatic rings ca. 1 nm apart, optimal to clamp a fullerene molecule (Fig. ). The modified protein, CTPR8Y 16 , expressed well and showed the same helical structure as the original protein, based on CD spectroscopy (Fig. ). The mutant protein also showed improved fullerene binding, resulting in significantly greater amounts of hybrid material, with no free protein recovered in the case of the more water-soluble C 60 A during purification, as determined by gel filtration chromatography (Fig. ).