In general consideration, as O2 is electrochemically reduced to O2 •-and the electron density increases, stabilization by HB is promoted with a concurrent increase in the complex formation constants (K -> K); therefore, the potential shifts to the positive side. Then, postulating that the molecular radii of complexes (O2-RsvH3/O2 •--RsvH3) are almost same, it is expected that DO‧app and Dsup‧app are equal. Hence, the negative-shift of Epc observed in the CVs (Figure ) is associated with K (Equation ( )) and K -(Equation ( )) in Equation ( ), implying that K -has little effect and the effect of K is emphasized at the negative-shift. On the other hand, it is reasonable that the effect of K, which is the formation constants of HB complex with O2, appears greatly since RsvH3 has three OHs in its structure. Considering above, the peculiar CV (type A)