4152
J. Phys. Chem. B 2008, 112, 4152
ADDITIONS AND CORRECTIONS 2006, Volume 110B Shubhadeep Purkayastha, Jamie R. Milligan, William A. Bernhard*: An Investigation into the Mechanisms of DNA Strand Breakage by Direct Ionization of Variably Hydrated Plasmid DNA In the above-referenced paper, we reported the yields of DNA single-strand breaks (ssb) produced by the direct effect of ionizing radiation. The ssb yields, G′(ssb), were determined from the slopes of dose response curves derived from the loss of the supercoiled form of pUC18 plasmid. We have now discovered an error in the presentation of the data in Figure 1. In an attempt to reduce the overlap in data points, an offset had been applied to four of the five dose response curves before conversion of the y-axis (using Origin 6.0 by Microcal) from the linear to natural log. Consequently, only the data for Γ ) 2.5, which was not offset, displays the correct slope on the semilog plot. For each of the other data sets, the offset resulted in not only changing the values but also the slopes, with the change in slope increasing as the offset increased. As presented, therefore, the slopes do not give the values of G′(ssb), which are given correctly in Table 1. In the corrected Figure 1, no offset was applied, and the slopes reproduced the prompt ssb yields given in Table 1 of the paper.
Figure 1. Loss of supercoiled DNA with increasing radiation dose for X-irradiated pUC18 plasmid samples at various Γ. The data include plasmids at (oval) Γ ) 2.5, (rectangle) 7.5, (triangle) 11.5, (diamond) 15.0, and (plus sign) 22.5 mol water/mol nucleotide. The samples were warmed to room temperature and dissolved in 1× TE buffer prior to gel electrophoresis. The data sets are fit with a least-mean-squares straight line of the form ln(y) - ln(c) ) -mx. From the slope m of each line, G′(ssb) was calculated.
10.1021/jp801177r Published on Web 03/06/2008
