(a) The percent Zmax (circle) and Zav (square) of ZR, for protein ions formed from aqueous ammonium acetate (filled markers) or pure water (open markers) prior to reaction with a base v. the decrease in Zmax (circle) and Zav (square) after 120 s reaction with DPA. (b) fraction of basic residues, (c) molecular weight (d) number of basic residues (e) isoelectric point (pI) for each protein as a function of the decrease in Zmax (circle) and Zav (square) after 120 s reaction with DPA. (i) corresponds to cytochrome c, (ii) myoglobin, (iii) carbonic anhydrase, (iv) concanavalin A dimer and (v) holo-transferrin ions, respectively.