Fig. 3.

(a) The absolute concentration of total ubiquitin and inter-Ub links of affinity purified proteins. Four of 7 inter-ubiquitin links tested were detected. Total Ub concentration was calculated by averaging the summed concentrations of linked peptides and their preceding and following linear peptides. All concentrations are reported in fmol µg⁻¹ of digest; (b) this plot shows the relative concentrations of inter-Ub links to the total Ub in enriched protein samples. In the case of YPR074C that the summation of linkage/total Ub% reaches 100% we can conclude that mono-ubiquitinated form of this protein was not present in the enriched sample.