Ueno, T.

Small 2010, 6, 1873-1879, 10.1002/smll.201000772

The synthesis of a robust bio‐nanotube consisting of the β‐helical tubular component proteins of bacteriophage T4 is described. The crystal structure indicates that it has a well‐defined nanoscale length of 10 nm as a result of the head‐to‐head dimerization of β‐helices. Surprisingly, the tube assembly has high thermal stability, high tolerance to organic solvents, and a wide pH‐stability range.

Ueno, T.

Chem. Commun. 2011, 47, 2074, 10.1039/C0CC03015E

We have constructed a robust β-helical nanotube from the component proteins of bacteriophage T4 and modified this nanotube with RuII(bpy)3 and ReI(bpy)(CO)3Cl complexes. The photocatalytic system arranged on the tube catalyzes the reduction of CO2 with higher reactivity than that of the mixture of the monomeric forms.

Ueno, T.

Dalton Trans. 2012, 41, 11424, 10.1039/C2DT31030A

We have succeeded in preparing semi-synthesized proteins bound to Sc3+ ion which can promote an epoxide ring-opening reaction. The Sc3+ binding site was created on the surface of [(gp5βf)3]2 (N. Yokoi et al., Small, 2010, 6, 1873) by introducing a cysteine residue for conjugation of a bpy moiety using a thiol–maleimide coupling reaction. Three cysteine mutants [(gp5βf_X)3]2 (X = G18C, L47C, N51C) were prepared to introduce a bpy in different positions because it had been reported that Sc3+ ion can serve as a Lewis-acid catalyst for an epoxide ring-opening reaction upon binding of epoxide to bpy and two –ROH groups. G18C_bpy with Sc3+ can accelerate the rate of catalysis of the epoxide ring-opening reaction and has the highest rate of conversion among the three mutants. The value is more than 20 times higher than that of the mixtures of [(gp5βf)3]2/2,2′-bipyridine and L-threonine/2,2′-bipyridine. The elevated activity was obtained by the cooperative effect of stabilizing the Sc3+ coordination and accumulation of substrates on the protein surface. Thus, we expect that the semi-synthetic approach can provide insights into new rational design of artificial metalloenzymes.