Fig. 5.

Nanospray spectrum of 13 μM GclR protein with 6 μM consensus DNA in 10 mM NH₄HCO₃, 1 mM DTT. This spectrum was acquired continuously over 40 min. Only one major ion series is found, with the 22–28+ of a complex of mass 134,939 daltons, which can be explained as a tetrameric protein with one dsDNA. This complex was stable at 160 V (compare to the spectrum of the protein alone in Fig. 3 ▶). Addition of excess DNA made the peaks broader (increase in the FWHM value from 213 daltons), but did not produce any different ions. The deconvolution of the major ion series (inset) shows three species, the most abundant representing a complete dsDNA and four protein subunits. The minor species probably represent failure synthesis of the DNA. The ions at m/z 3000–4000, are the 14–20+ ions from protein dimer (see also Fig. 3 ▶).