Uranyl photofootprinting

Abstract

The uranyl-(VI) cation (UO 22+) forms strong complexes with accessible phosphates of nucleic acid (DNA and RNA) backbones. Upon excitation with long wavelength ultraviolet light (λ = 300-420 nm), uranyl ions bound to backbone phosphates oxidize proximal sugars and induce nucleic acid backbone cleavage. Thus the uranyl(VI) ion functions as a very specific and efficient photochemical probe for identifying ligand(protein)- phosphate contacts in nucleic acid complexes as well as potential (high affinity) cation (e.g., Mg 2+)-binding sites in folded nucleic acids. Finally, the cleavage modulation of duplex DNA reflects helix conformation in terms of minor groove width, due to preferential affinity/oxidation efficiency for such regions of the DNA helix. © 2009 Humana Press, a part of Springer Science+Business Media, LLC.