Table 1.

Second-order bimolecular association rate constants for myosin-ADP or myosin-dADP binding with an actin dimer

Reaction distance criteria, nm	Actin-myosin on-rates, μM−1⋅s−1
	Myosin-ADP	Myosin-dADP	Fold change
0.7	0.42	0.82	1.9
0.8	1.66	4.18	2.5
1.0	8.02	22.02	2.7
1.2	21.37	76.84	3.6
2.5	403.10	1431.73	3.6
5.0	3,198.05	4,460.93	1.4

Rate constants were determined by BD simulations, as described in the text and SI Appendix. For each nucleotide, as the reaction distance criteria decreases, the on-rate increases nonlinearly. However, the on-rate for dADP-myosin to the actin dimer is consistently greater compared with ADP-myosin for all reaction distance criteria, with the greatest fold change in the range of 1.2–2.5 nm. This strongly supports the notion of an increased electrostatic affinity between actin and myosin induced by dADP.