▎ 摘　　要

Triplex DNA has received great attention as new molecular biology tools and therapeutic agents due to their possible novel functions in biology systems. Therefore, it is important to distinguish triplex from among different forms of DNA, such as single-stranded and double-stranded DNA. In this report, several electrochemical techniques, cyclic voltammetry, electrochemical impedance spectroscopy, different pulse voltammetry, and electrochemiluminescence were used for distinguishing this unique structure among different DNA formations by using functionalized graphene/Nafion- Ru(bpy)(3)(2+) (bpy = 2, 2'-bipyridine) modified glass carbon electrode. The different interactions between nucleotides and graphene surface and Ru(bpy)(3)(2+) mediated guanine oxidation produced quite different electrochemical responses. Guanine bases are hidden inside the folded triplex DNAs, which are much less susceptible to be oxidized by Ru(bpy)(3)(3+) produced on electrodes. Furthermore, the effect of guanine bases stacking in triplex also influences the electrochemical behaviors. By changing the different position and distance of guanine bases in DNA sequences, we found that the conjoint way of several guanines strongly influenced the catalytic electrochemical responses on graphene surface. Our results provide new insight into determination of less stable protonated triplex formation by using graphene-based rapid, low-cost and sensitive electrochemical techniques.