DNA binding of a spermine derivative: spectroscopic study of anthracene-9-carbonyl-N super(1)-spermine with poly[d(G-C) multiplied by (d(G-C)] and poly [d(A-T) multiplied by d(A-T)]

The binding of polyamines, including spermidine (1) and spermine (2), to poly[d(G-C) multiplied by d(G-C)] was probed using spectroscopic studies of anthracene-9-carbonyl-N super(1)-spermine (3); data from normal adsorption, linear dichroism (LD), and circular dichroism (CD) are reported. Ligand LD and CD for transitions located in the DNA region of the spectrum were used. The data show that 3 binds to DNA in a manner characteristic of both its amine and polycyclic aromatic parts. With poly[(dG-dC) multiplied by (dG-dC)], binding modes are occupied sequentially and different modes correspond to different structural perturbations of the DNA. The most stable binding mode for 3 with poly[d(G-C) multiplied by d(G-C)] has a site size of 6 plus or minus 1 bases, and an equilibrium binding constant of (2.2 plus or minus 1.1) x 10 super(7) M super(-1) with the anthracene moiety intercalated. It dominates the spectra from mixing ratios of approximately 133:1 until 6:1 DNA phosphate: 3 is reached. The analogous data for poly[d(A-T) multiplied by d(A-T)] between mixing ratios 36:1 and 7:1 indicates a site size of 8.3 plus or minus 1.1 bases and an equilibrium binding constant of (6.6 plus or minus 3.3) x 10 super(5) M super(-1). Thus, 3 binds preferentially to poly[d(G-C) multiplied by d(G-C)] at these concentrations