SPECTROSCOPIC STUDIES ON THE INTERACTION OF 3 PARTIALLY HYDROGENATED ACRIDINE-DYES WITH CALF THYMUS DNA AND THEIR STRUCTURAL COMPARISON

The interaction of three partially hydrogenated acridine dyes (acridin e I, acridine II and acridine III) with calf thymus DNA was studied us ing spectrophotometric and spectrofluorometric methods. This paper pre sents the evidence for the formation of complexes between acridine I, II and III with calf thymus DNA From the results of this studies vario us binding parameters were evaluated. The binding constant for acridin e I and acridine In: ranged from 2.1 to 4.4 X 10(5)M(-1) for the P/D r atio from 4.29 to 0.56 while for acridine II this constant increased f rom 0.78 to 2.26 X 10(5)M(-1) for the P/D ratio 12 to 2.38 and decreas ed to 1.47 at P/D ratio 1.34. The Scatchard analysis indicated a coope rative binding of acridine II to calf thymus DNA as compared to acridi ne I and III. A red shift in the visible absorption bands for dye DNA complexes (for acridine I = 8, acridine II = 7, and acridine III = 9 n m) suggested an electronically coupled interaction mode for the dyes. It is concluded that acridine II interacted stronger with calf thymus DNA than acridine I or III. The results are interepreted in terms of t heir crystal structures and also with the already reported DNA binder structures.