THE THERMODYNAMIC CHARACTERIZATION OF POLY(I).POLY(C) DUPLEX AMINOACRIDINE DYE SYSTEM

In the reported experiments, thermodynamic quantities of dyes (proflavine, PF and 9-aminoacridine, 9AA) bound to the poly(I)-poly(C) duplex in the intercalation process have been evaluated from measurement of the heat of mixing. The free energy change for the duplex-PF system is smaller than that for the duplex-9AA system, indicating that the intercalation of PF into the poly(I)-poly(C) duplex is more stable than the intercalation of 9AA, as in the case of that in the poly(A)-poly(U) duplex-dye system reported previously. This conclusion was drawn from the heat of interaction between PF and poly(I)-poly(C) duplex being larger than that between 9AA and poly(I)-poly(C) duplex. In addition, the enthalpy change of the poly(I)-poly(C) duplex-dye system is smaller than that of poly(A)-poly(U) duplex-dye one, suggesting that the conformational change of the poly(I)-poly(C) duplex in the intercalation process is considerably larger than that of the poly(A)-poly(U) duplex.