Superoxide dismutase mass spectrum

Figure 3-11 Matrix-assisted laser desorption / ionization time-of-flight (MALDI-TOF) mass spectrum of bovine erythrocyte Cu-Zn superoxide dismutase averaged over ten shots with background smoothing. One-half pi of solution containing 10 pmol of the enzyme in 5 mM ammonium bicarbonate was mixed with 0.5 pi of 50 mM a-cyanohydroxycinnamic acid dissolved in 30% (v / v) of acetoni-trile-0.1% (v / v) of trifluoroacetic acid. The mixture was dried at 37° C before analysis. The spectrum shows a dimer of molecular mass of 31,388 Da, singly charged and doubly charged molecular ions at 15,716, and 7870 Da, respectively. The unidentified ion at mass 8095.6 may represent an adduct of the matrix with the doubly charged molecular ion. Courtesy of Louisa Tabatabai.

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