452 Chapter 11
Figure 11.18 Electrospray ionization mass spectrum (negative mode) of oligodeoxyribonucleotide d(GCGTTCCCC-
CTTTGCG) dissolved in methanol containing 0.5% diethylamine. The determined molecular mass is
4797.8091. The spectrum shows masses of the multiply charged species [M-3H]^3 (1599), [M-3H-
Na]^4 (1204.4), [M-4H]^4 (1198.9), [M-5H]^5 (958.8), [M-6H]^6 (798.9) and [M-7H]^7 (684.7)
(Figure kindly provided by J. Brazier and R. Cosstick)
Figure 11.19 Mass spectra of E. coli ribosomes recorded from solution at pH 7.0 (a) and pH 4.5 (b). Peaks are
labelled with the protein bound, and the numbers of positive charges are given in parenthesis. At pH
7.0, four proteins located in the mobile stalk region of the ribosome dominate the spectra. At pH 4.5,
eight proteins are identified. Inset, MS/MS spectrum of the peak labelled *. Acceleration in the
collision cell yields a mass consistent with that calculated for the 5S RNA. Individual charge states of
the L7/L12 proteins reveal their metal-binding properties and post-translational modifications
(Reprinted from Ref. 50. © (2003), with permission from ASBMB)