| Abstract: | The interaction between DNA and dyes such as acridine orange ( 1 ), proflavine ( 2 ), and 3,8-diamino-5-ethyl-6-phenylphenanthridinium bromide ( 3 ) were studied by means of the heat of mixing and UV spectra. From the results obtained, the thermodynamic quantities of DNA-dye complexes were estimated. It is concluded that the intercalation process forms a more stable binding than the stacking process does. Further, in each process, ΔG of DNA- 2 and DNA- 3 systems is nearly equal to that of the DNA- 1 system, but their — ΔH and — ΔS values are higher than those of the DNA- 1 system. The stability of binding in DNA- 2 and DNA- 3 systems may be governed largely by ΔH, while in the DNA- 1 system ΔS may contribute largely to the stability of binding. |
