Interaction of pyrimoidiazolium ions in calf thymus DNA

A new class of fluorescent dyes, pyridoimidiazolium cations, is being considered for their possible use in the biochemical field because of their interactions with DNA. Binding of low molecular weight fluorophores has been proven to cause a wide variety of biological responses in DNA. The dyes used here have been synthesized using α-diimine type compounds. The reaction used has the capability to produce many fluorescent cations. Binding constants of these compounds in acetonitrile with calf thymus DNA have been determined by measuring emission intensity. Emission intensity showed the degree to which binding is occurring. The experimental results show that binding is occurring among all of the fluorophores studied and calf thymus DNA. Binding is proven in the decrease in emission, with one exception, seen upon each addition of DNA. The one fluorophore which differed showed an increase in emission intensity, to a certain concentration of DNA, at which it behaved as the rest and decreased. The experimental results also show that there is no generalization that can be made when trying to correlate the binding constants with the type of binding that is occurring between these fluorophores and DNA, intercalation or nonintercalation.