Figure 2.

Half-Life of Acetylation Incorporation. (A) The ratio of heavy acetylation incorporation ¹³C/(¹³C + ¹²C) plotted against the time. The half-time of heavy acetyl incorporation was calculated by fitting the ratios of ¹³C/(¹³C + ¹²C) acetylated peptides at each time point to the equation y = a*(1-e^(-x/b)). In the case if after 24 hours the amount of heavy labeled acetylation did not reach 0.5, as shown for the HMG-CoA lyase peptide, we used the linear polynomial equation y = ax + b. The red dashed line indicates the half-life for the Ubinuclein-2 K1147 acetyl site. (B) The isotopic patterns of heavy acetylation incorporation for two peptides identified in the ¹³C-glucose labeling experiment, and two peptides in the D₃-acetate labeling experiment are shown. The top row shows the mass spectra for the 0 hour time point, and the bottom row shows the mass spectra for the 24 hour time point. For each glucose and acetate labeled sections, the left spectra indicate a peptide that did not incorporate heavy acetylation, and the right spectra indicate a peptide that did incorporate heavy acetylation over time. The red dashed box indicates the monoisotopic peak, and the green dashed box indicates the heavy labeled peak.