[Analysis of defects in the structure of the complex poly(G).poly(C)].

The concentration of free poly(C) in solution in the course of its interaction with poly(G) as well as in the presence of preformed complex poly(G).poly(C) was measured by differential pulse polarography (DPP) at a mercury dropping electrode. Poly(C) binding with poly(G) was shown to hamper its electrochemical interaction with the mercury electrode and registration by DPP. It was concluded that the extremely low DPP signal from poly(C) in the presence of preformed complex was the result of its interaction with the distortions in the secondary structure of complex molecules containing free guanines. For quantitative testing of these defects, measurement of Tb3+ ion fluorescence was applied. It was shown that preliminary denaturation of the poly(G) secondary structure reduced the amount of structural defects in the complex and restored of complete DPP registration of redundant poly(C) added to this complex. These results show that the combination of DPP and Tb3+ fluorescence measurements permits one to detect at the quantitative level the structural defects in the poly(G).poly(C) complex.