Determination of the antibody titer To determine the titer of the antibody, an ELISA was performed using a serial dilution of the antibody against H2A.Zac, crude serum and flow through in antigen coated wells. The antigen used was a peptide containing the histone modifications of interest. By plotting the absorbance against the antibody dilution (Figure 3), the titer of the purified antibody was estimated to be 1:8, 800.