Oxidative damage to DNA is important in the progression of molecular diseases such as cancer. Electron holes produced upon DNA oxidation are mobile and can move throughout the base stack. One possible trapping reaction for guanine radicals is the formation of DNA-protein crosslinks. The fluorescent base analogue, 2-aminopurine (2-Ap) is capable of photo-oxidizing guanine but also undergoes back electron transfer with the guanine radical produced. We placed 2-Ap into a DNA strand at three different distances from the nearest guanine base to determine the relative rates of back electron transfer and crosslinking to histone protein. Crosslinking was detected by gel shift assay.  Crosslinking was observed for 2 and 4 basepair separations, but not for systems with guanine adjacent to the 2-Ap base, indicating that the latter system has back electron transfer occurring much more quickly than crosslinking.

System for comparing relative rates of back electron transfer and crosslinking

243rd National Meeting (2012)

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