In vitro nucleotide misinsertion opposite the oxidized guanosine lesions spiroiminodihydantoin and guanidinohydantoin and DNA synthesis past the lesions using Escherichia coli DNA polymerase I (Klenow fragment).

The low redox potential of 8-oxo-7,8-dihydroguanine (OG), a molecule regarded as a marker of oxidative damage in cells, makes it an easy target for further oxidation. Using a temperature-dependent method of synthesis, the oxidation products of OG, guanidinohydantoin (Gh) and/or its isomer iminoallantoin (Ia) as well as spiroiminodihydantoin (Sp), have been site-specifically incorporated into DNA oligomers. Single nucleotide insertion and primer extension experiments using Escherichia coli Kf exo(-) DNA polymerase were carried out under "standing start" and "running start" conditions in various sequence contexts.