(A) Plot showing the average translational displacement per actuation for the rollers coated with the indicated H3K4 methylated peptide on a DIDO1-PHD surface. Streptavidin-biotin and streptavidin-avidin (PBS) are included for references. See Figure 2—source data 2 for results of statistical analysis; all comparisons are statistically significant (p<0.0001). (B) Plot showing the calculated average rolling parameter per interaction. (C) Log-Log plot of the rolling parameters (RP) from panel B with the reported Kds. Extrapolated points for the unknown interactions are represented by unfilled markers, and the 95% confident interval for the fitting is depicted. (D) Table of rolling parameters and associated Kd estimates for the DIDO1-PHD interactions. Fold change is calculated as the ratio between the Kd values for the indicated peptide and for H3K4me3. These ratios are used to calculate at T=298K. The published values are from Gatchalian et al., 2013 using NMR (me1) and tryptophan fluorescence (me2/3); *ND = Not determined. (E) Image of the DIDO1-PHD crystal structure with H3K4me3 peptide, with the PHD surface electrostatic potentials shown (red = negative, blue = positive), the for K4me3, and the estimated for the rest of the peptide. The PTM reader sites are shown with greater detail to the right. Here, is calculated between the sequential methyl states, and the ratio of H3T3pK4me3 and H3K4me3 give the for T3p. (F) Results of the DIDO1-PHD histone peptide microarray assay against the indicated peptides (see Figure 1—figure supplement 1B for results of all peptides). Only H3K4me3 is statistically significant (P<0.05). (see Figure 2—source data 2 for results of statistical analysis). While these results indicate general binding trends, they cannot provide Kd estimates and do not have high enough resolution to distinguish between weaker binding interactions.