DNA-drug systems: How circular dichroism data is complemented by other spectroscopic techniques

Abstract

Circular dichroism (CD) measurements of DNA-drug complexes of two different systems are interpreted with the aid of other experimental and calculation data. The induced CD (ICD) of the polyamine mimic [Co(NH3)]3+ has been used to determine the low drug:DNA ratio binding constant with calf thymus DNA of 1,00,000 M-1 at 11 mM Na+. The site size is large. Linear dichroism (LD) shows how the DNA bends in accord with changes in DNA conformation observed in the CD. 9-hydroxyelliptine DNA binding in the intercalation limit and the higher concentration mode that gives rise to exciton CD signals have been probed using normal absorption, LD, both film and flow, and resonance light scattering. CNDO/S-CI calculations have also been investigated as a means of determining transition moments and intensities of individual transitions in a complex overlapping spectrum.