Table 3. Kinetic and affinity determinations of WDR5-SET1_Win interactions using SPR.

Values represent mean ± s.d. acquired from at least three independent experimental determinations (separate receptor immobilizations). For MLL2_Win, n = 4 independent experimental determinations were used.

Peptide sequence	kon (M−1s−1) × 10−5	koff (s−1) × 103	KD-SPR (nM)
Sulforhodamine B-(GGS)3MLL1Win-NH2	ND*	ND**	16,000 ± 3,000***
Sulforhodamine B-(GGS)3MLL2Win-NH2	3.7 ± 0.3	12 ± 1	33 ± 2
Sulforhodamine B-(GGS)3MLL3Win-NH2	4.9 ± 0.4	9 ± 1	19 ± 1
Sulforhodamine B-(GGS)3MLL4Win-NH2	2.1 ± 0.3	41 ± 3	190 ± 20
Sulforhodamine B-(GGS)3 SETd1AWin-NH2	3.1 ± 0.2	110 ± 10	350 ± 10
Sulforhodamine B-(GGS)3SET1dBWin-NH2	3.4 ± 0.3	24 ± 1	69 ± 6

^ND*k_on was not quantitatively determined. Although the WDR5-MLL1_Win interactions were detectable using an SPR measurement (Fig. 3), no accurate quantitative determination was made due to the limited time resolution of the approach. In this case, we assume that the k_on was in the same order of magnitude with the k_on of other SET1_Win peptides (~10⁵ M⁻¹s⁻¹).

^ND**k_off was not quantitatively determined due to a fast dissociation rate constant. The upper-limit value for the detection of k_off is 0.5 s⁻¹ according to instrument specifications. The Biacore 8K+ cannot measure rate constants of dissociation, k_off, faster than 0.5 s⁻¹.

^***Here, K_D-SPR was determined using a steady-state SPR measurement (Supplementary Figure S6).