Physico-Chemical Events

Sunday, October 16, 2005 3:00 PM-5:00 PM Exhibit Hall

(PP023) Direct damage to DNA by low-energy electrons.

Pan, Xiaoning1, Sanche, Léon*,1, 1 Department of Nuclear Medicine and Radiobiology, Sherbrooke, Quebec, Canada

ABSTRACT- We present results on the desorption of OH- induced by 0-19 eV electrons incident on self-assembled monolayer (SAM) films made of single and double DNA strands of different orientations with respect to a gold substrate. Such measurements make it possible to deduce the mechanism and site of OH- formation within a biomolecule as complex as DNA. The yield functions of OH- for the four different DNA SAM configurations have a threshold around 2.0 eV, the lowest value among all anions detected in this type of experiments; it exhibits a resonant peak at around 7 eV. We determine both the mechanism and site of OH- production: this type of damage is attributed to dissociative electron attachment to the phosphate group of DNA, when it contains the counterion H+, i.e., e + DNA → (DNA)- → (DNA-OH) + OH-. The present results demonstrate that the phosphate-counterion portion of DNA plays a significant role in low-energy electrons (LEEs) damage induced to DNA, and provide new insight about LEE-DNA interactions.

Key words: DNA, low-energy electrons

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2005 RRS