Direct observation of ultrafast-electron-transfer reactions unravels high effectiveness of reductive DNA damage
2011
Nguyen, Jenny | Ma, Yuhan | Luo, Ting | Bristow, Robert G. | Jaffray, David A. | Lu, Qing-Bin
Both water and electron-transfer reactions play important roles in chemistry, physics, biology, and the environment. Oxidative DNA damage is a well-known mechanism, whereas the relative role of reductive DNA damage is unknown. The prehydrated electron (Formula ), a novel species of electrons in water, is a fascinating species due to its fundamental importance in chemistry, biology, and the environment. Formula is an ideal agent to observe reductive DNA damage. Here, we report both the first in situ femtosecond time-resolved laser spectroscopy measurements of ultrafast-electron-transfer (UET) reactions of Formula with various scavengers (KNO₃, isopropanol, and dimethyl sulfoxide) and the first gel electrophoresis measurements of DNA strand breaks induced by Formula and OH{bullet} radicals co-produced by two-UV-photon photolysis of water. We strikingly found that the yield of reductive DNA strand breaks induced by each Formula is twice the yield of oxidative DNA strand breaks induced by each OH{bullet} radical. Our results not only unravel the long-standing mystery about the relative role of radicals in inducing DNA damage under ionizing radiation, but also challenge the conventional notion that oxidative damage is the main pathway for DNA damage. The results also show the potential of femtomedicine as a new transdisciplinary frontier and the broad significance of UET reactions of Formula in many processes in chemistry, physics, biology, and the environment.
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