KCS

Diatamycin A(DST) and Netropsin(NET) are a well known polyamide antibiotic that can bind in the minor groove of duplex DNA primarily at AT-rich sequences. An FTIR and CD study of the DNA binding modes of DST and NET were investigated binding studies with oligomeric duplexes of the form d(CGCGAAAAACGCG)·(CGCGTTTTTCGCG). Distamycin A can bind both as a monomer or as a side-by-side antiparallel dimer. In case of oligomer duplexes with AAAAA binding sites,1:1 complexes are formed at low distamycin:DNA ratios and 2:1 complexes are formed at the ratios >1. It was found that 1:1 and 2:1 drug-duplex complexes exhibit distinctly different circular dichroic(CD) spectral characteristics and can, thus, serve as diagnostic tools for binding mode differentiation. It the infrared spectra of antiparallel-stranded(aps) DNA have been studied. Significant differences have been found in the region of the thymine C=O stretchingvibrations. Interaction with three drugs known to bind in the minor groove of aps-DNA - netropsin and distamycin A - induces shifts of the C = O stretching vibrations of ps-DNA even at low ratio of drug per DNA base pair.