Non-covalent complexes between bis-beta-carbolines and double-stranded DNA: A study by electrospray ionization FT-ICR mass spectrometry (I).

The non-covalent complexes of five bis-beta-carbolines alkaloids with three different double-stranded oligodeoxynucleotides d(GCGCGATCGCGC)(2), d(GCGCAATTGCGC)(2), and d(GCGAAATTTCGC)(2) were investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. These five antitumor compounds all showed DNA-binding abilities. Binding affinities in the order of 2>3, 4>5, and 1 with double-stranded DNA were obtained, which mean that the length of the linkage chain between two beta-carbolines has a remarkable effect on the formation of the non-covalent complexes. Additionally, the preliminary results indicated that bis-beta-carbolines had no notable sequence selectivities.