Isotopic labeling of histone variants. Average relative distribution (markers) of the fully isotopically labeled (A) H3, H4 and H1.4 peptides, (B) H2A peptides and (C) H2B variant peptides across the labeling time course. Note the gradual accumulation of the fully labeled peptide as time increases. The peptide labeled as H2A (V,Z) corresponds to the sequence ATIAGGGVIPHIHK, and the peptide labeled as H2A (types 1B, C, E and 3) corresponds to the sequence NDEELNKLLGR. All other peptides correspond to > 3 different histone proteins. Vertical lines represent standard deviation.