Figure 5.

LSD1 activity can be measured using MassSQUIRM. (A) 0.25 µg of a synthetic H3K4me2 peptide was subjected to varying concentrations of recombinant LSD1 in demethylase buffer for 2 h at 37°C and analyzed with MassSQUIRM. (B) Quantification of methylation levels was determined using r₁ and r₂ values from peptide alone samples (bottom panel) and equations 5–7. Open circles indicate light methylation while closed circles indicate heavy methylation.