Correction

BIOPHYSICS. For the article “Detection and characterization of the product of hydroethidine and intracellular superoxide by HPLC and limitations of fluorescence,” by Hongtao Zhao, Joy Joseph, Henry M. Fales, Edward A. Sokoloski, Rodney L. Levine, Jeannette Vasquez-Vivar, and B. Kalyanaraman, which appeared in issue 16, April 19, 2005, of Proc. Natl. Acad. Sci. USA (102, 5727–5732; first published April 11, 2005; 10.1073/pnas.0501719102), the authors note that the last sentence of the Abstract, “We conclude that the HPLC/fluorescence assay using HE as a probe is more suitable reactive oxygen species for detecting intracellular ,” should read “We conclude that the HPLC/fluorescence assay using HE as a probe is more suitable for detecting intracellular .” This change does not alter the conclusions of the article.