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. Author manuscript; available in PMC: 2009 Aug 13.
Published in final edited form as: J Am Chem Soc. 2008 Jul 18;130(32):10780–10787. doi: 10.1021/ja803083z

Figure 5.

Figure 5

(a) The pH dependence of fraction of aTAM4 radical protonated form, fRH+, obtained from EPR spectra measured at 23 °C (○) and 37 °C (□) as shown in Figure 2 and Figure 4. Lines represent the best fits of titration equation to the experimental data yielding pKa values 8.4 ± 0.05 (23 °C) and 8.0 ± 0.1 (37 °C). (b) The pH dependence of spectral amplitude ratios of the high-field components of deprotonated (R) and protonated (RH+) forms of aTAM4 radical (see Figure 4a) in logarithmic scale. Lines represent the linear regression, log(IR/IRH+) = apH − b, yielding a = 1.35 ± 0.02 and b = 10.3 ± 0.2.