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. 2008 Feb 14;36(6):2073–2081. doi: 10.1093/nar/gkn051

Figure 4.

Figure 4.

Pre-looped DNA. (a) FokI and 3H-labelled pIF185 in Buffer R was mixed with an equal volume of MgOAc in Buffer R to give a mixture that contained 2.5 nM DNA (80% SC), 125 nM FokI and 10 mM MgOAc. After various times, the reactions were quenched with EDTA and the residual concentrations of SC DNA measured. The insert shows data from reactions over 1 s, the main panel reactions over 60 s. The line through the data points corresponds to the equation for a triple exponential decay, with values of 23 ± 5 s−1, 0.6 ± 0.2 s−1 and 0.06 ± 0.03 s−1 for the rate constants. The first and second were the best fits to the data in the insert, the third to the data in the main panel. (b) The data in (a) show that kcleave must be about 20 s−1 and that the process which limits kmax to 3 s−1 is kloop.