Figure 2.

(a) Charge state series for the native ADH tetramer after online SEC. Dashed lines indicate the calculated maxima (i.e., most abundant isotope peaks) for charge states from 23+ to 28+. (b) Zoom on the 26+ charge state, showing the extreme (for native MS) resolving power and mass accuracy achieved with this method. “Δ” denotes the difference between the observed (blue) and calculated (red) maximum. Note that the Zn²⁺ binding adds 61.91 Da per metal cation (495.32 Da for all eight or approximately 0.34% of the mass of the complex), corresponding to 2.38 m/z at this charge state (19.05 m/z in total), and is thus easily observable with this method. No smoothing of the spectrum was performed.