16] Damage to DNA by long-range charge transport

Abstract

Photochemical reactions on DNA assemblies containing tethered photooxidants, particularly metallointercalating photooxidants, have been critical in establishing that permanent damage to DNA bases can be generated as a result of radical migration from a remote site on the DNA duplex. Induction of a 1-electron deficiency in the oxidant attached covalently to the DNA remote from the oxidizable site leads to this “chemistry at a distance,” caused by efficient charge transport through the DNA base pair stack. Double helical DNA may be unique as a polymeric assembly in solution because of this interior core of stacked aromatic heterocyclic base pairs. Similarly stacked solid-state materials tend to be conducting along the stacking direction. This chapter describes the design and construction of DNA assemblies used to probe long-range oxidative damage in DNA. It also includes methodology for the oxidative repair of a thymine dimer lesion in DNA, as this “chemistry at a distance” also depends on long-range charge transfer through the DNA base pair stack.