CHEMISTRY, BIOCHEMISTRY. For the article “DNA-mediated charge transport for DNA repair,” by Elizabeth M. Boon, Alison L. Livingston, Nikolas H. Chmiel, Sheila S. David, and Jacqueline K. Barton, which appeared in issue 22, October 28, 2003, of Proc. Natl. Acad. Sci. USA (100, 12543-12547; first published October 14, 2003; 10.1073/pnas.2035257100), the authors note that the calibrations to potentials versus NHE using Ag wire were not accurate. Measurements using an Ag/AgCl reference electrode rather than Ag wire show the midpoint potentials for DNA-bound MutY to be -110 mV or 90 mV versus NHE. Similarly, for the DNA-bound MutY mutant, C199H, the midpoint potential is -135 mV or 65 mV versus NHE. This correction does not affect the conclusions of the article.