Figure 3

Determination of histone variant H3.2 and identification of methylation at Lysine 27 of histone variant H3.2. A. MALDI-TOF mass spectrum showing mono- (m/z 959.58), di- (m/z 973.59) and tri- (m/z 987.61) methylation at Lysine 27 in the peptide ²⁷KSAPTTGGVK³⁶ of histone H3.2, but without non-methylation (about m/z 945) at this site. B, C and D. MS/MS spectrum of the peptide precursor ions at m/z 959.58, 973.59 and 987.61 respectively determining mono-, di- and tri-methylation at Lysine 27 in the peptide of ²⁷KSAPTTGGVK³⁶ of histone H3.2. B, C, and D indicated that the amino acid sequence of this peptide was KSAPTTGGVK and only Lysine 27 was methylated, but not Lysine 36.