Electron transfer in DNA from guanine and 8-oxoguanine to a radical cation of the carbohydrate backbone.
Photolysis of a 4'-pivaloyl-substituted nucleotide in single- and double-stranded DNA (1) generated an enol ether radical cation 4 that was reduced to enol ether 17 by electron transfer from the nearest guanoside (G). Variation of the nucleotide sequence demonstrated a strong distance dependence of this electron-transfer rate with beta = 1.0 +/- 0.1 A(-1). When 8-oxoguanosine (G(oxo)) was used as the electron donor, the rate of the electron transfer increased by a factor of 4 but the distance dependence of the transfer remained unchanged within experimental error. In single strands, the number of intervening A, T, and C nucleotides had a much smaller effect; the rate remained nearly constant for two, three, or four intervening nucleotides. This is explained by the flexibility of the single-stranded oligonucleotides.
Meggers
E
E
Department of Chemistry, University of Basel, Switzerland.
Dussy
A
A
Schäfer
T
T
Giese
B
B
D050260:Carbohydrate Metabolism; D004247:DNA / Q000378:metabolism*; D053938:DNA Fragmentation; D004579:Electron Transport; D005609:Free Radicals; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D010782:Photolysis
D005609:Free Radicals; C024829:8-hydroxyguanine; D006147:Guanine; D004247:DNA