Extended Data Fig. 3: Mass spectrometry of probe 17 synthetic intermediates.

a–l, Representative ESI-MS spectra and deconvoluted MS spectra of synthetic intermediates 6 (a), 8 (b), 7 (c), 9 (d), 10 (e), 11 (f), 12 (g), UbMesNa (h), 13 (i), 14 (j), 15 (k), and 16 (l) shown in Extended Data Fig. 2.