Butylacrylate-nucleobase Conjugates as Targets for Two-step Redox Labeling of DNA with an Osmium Tetroxide Complex

Abstrakt

Modification of nucleic acids with osmium tetroxide reagents (Os,L, such as OsO4,2,2-bipyridine, Os,bpy) has been applied in redox DNA labeling, in probing DNA structure as well as in studies of DNA interactions with other molecules. In natural DNA, primarily thymine residues form adducts with the Os,bpy in a structure selective manner. In this paper we introduce a new two-step technique of DNA modification with the electroactive Os,bpy, consisting in enzymatic construction of DNA bearing butyl acrylate (BA) moieties attached to uracil at C5 or to 7-deaza adenine at C7, followed by chemical modification of a reactive C=C double bond in the acrylate residue. We demonstrate a facile modification of the BA conjugates in both single- and double-stranded (ds) DNA under conditions when modification within the nucleobase rings in ds DNA is hindered. Various DNA-Os,bpy adducts can easily be analyzed electrochemically and distinguished by different redox potentials. The two-step procedure appears to be applicable in osmium redox labelling of ds DNA.