Apparent Binding Constants for DNA Interactions of Bifunctional Heteroaromatic Salts
Kelvin D. Gardner1, Courtney B. Mullins2, Melinda K. Solomon2, Lauren M. Hoth2, Wolfgang H. Kramer2*
1Provine High School, Jackson, MS
2Department of Chemistry and Biochemistry, Millsaps College, Jackson, MS
N-substituted heteroaromatic salts are photoactivatable compounds that are investigated for their impact on DNA. The compounds contain a DNA binding moiety which consists of the intercalator 1,8-naphthalimide. The separate DNA cleaving part can be activated by light and is producing two transient, reactive species: a heteroaromatic radical cation and an oxygen centered radical. Both of those species can damage DNA, each by a separate mechanism. To effectively cleave DNA, sufficient ground-state association is desired. DNA binding is measured by spectroscopic titrations (UV/Vis, fluorescence and CD). To determine DNA cleavage, gel electrophoresis is employed for analysis of cleavage fragments of pUC DNA. Supercoiled pUC migrates fastest. Double-strand cleavage produces linear DNA of that size which migrates slower. Single strand cleavage will relax the supercoils and produces circular DNA which migrates even slower. Time and concentration studies are performed to determine cleavage type. Addition of quenchers assists in the elucidation of the cleaving mechanism.
Acknowledgement: This work was supported by the Mississippi INBRE, funded by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20GM103476.