Design, synthesis and photophysical properties Of C60-modified proteins

Fullerene-porphyrin conjugates coordinated with Fe and Zn ions (1.Fe and 1.Zn) were designed and synthesized. Compounds 1.Fe and 1.Zn were reconstituted into apomyoglobin successfully to produce C-60-modified myoglobins. 1.Fe-Mb and 1.Zn-Mb. respectively. The axial-ligand exchange reaction revealed that 1.Fe-Mb maintains the intrinsic properties of native Mb, except for the autooxidation rate constant, suggesting similar microenvironment of the porphyrin moieties in the proteins, Cyclic voltammogram (CV) of a graphite electrode modified with a film of 1.Fe-Mb-didodecyldimethylammonium bromide (DDAB) two reversible redox Couples with E-o = -206 and - 1048 mV which are attributable to Fe2+/3+ and the reduction of file porphyrin ring, respectively. Differential pulse voltammogram of an electrode modified with a 1.Fe-Mb-tridodecylmethylammonium bromide (TDAB) film in water containing 0.5 tetraethylammonium chloride and 10 mM 2.2',2"-nitrilotriethanol showed three cathodic peaks at E-2,E-1 = -372, E-1/2 -555. and E-2/3 -1028 mV which are attributable to Fe2+/3+, C-60(0/1) and the reduction of the porphyrin ring respectively. The electrodes modified with 1.Fe-Mb and 1.Zn-Mb gage anodic photocurrent coupled with on-off light irradiation. The action spectrum of photocurrent for a 1.Zn-Mb DDAB film was in accord with the UV-vis absorption spectrum of 1.Zn-Mb. Transient absorption spectra of 1.Zn in benzonitrile and 1.Zn-Mb in a 50 mM phosphate buffer at 100 ns after the ns-laser light pulse irradiation at 532 nm showed three absorption maxima at 700, 830, and 1000 nm which are assignable to the triplet excited state of C-60 (C-3(60)*), the triplet excited state of the zinc porphyrin ((ZnP)-Zn-3*). and C-60 radical anion (C-60*) respectively. Existence of the apparent C-60* indicates the generation of charge-separation state, ZnP*-C-60*. The rate constants for the generation of the charge separation states in 1.Zn and 1.Zn-Mb calculated from the fluorescence data were 8.2 x 10(8) s(-1) and 6.4 x 10(8) s(-1), respectively, and the corresponding quantum yields were 0.62 and 0.59. were 0.62 and 0.59.