Table 2.

Estimated parameters of the Hill model from the best fits of stopped flow data (for both excess [S1] and excess [actin]) and titrations at pCa 8.9. The comparison contrasts the estimated parameters for prescribed reverse constants k₋₁ = 500 s⁻¹ and Y₂ =0.208 reported in Chen at al.¹ at high [Ca²⁺] and used in all our simulations (denoted as “High Ca²⁺ Rev. R.C.”) vs. the reverse constants k₋₁ =0.6 s⁻¹ and Y₂ = 0.0703 reported in¹ at low [Ca²⁺] (denoted as “Low. Ca²⁺ Rev. R.C.”).

	Stopped Flow				Titrations
	Excess Actin		Excess Myosin		High Ca2+ Rev. R.C.	Low Ca2+ Rev. R.C.
	High Ca2+ Rev. R.C.	Low Ca2+ Rev. R.C.	High Ca2+ Rev. R.C.	Low Ca2+ Rev. R.C.
αo	82.3	200	81	200	200	200
βo	300	300	300	300	300	300
Y1	5.576	15.27	7.149	18.2	78.0	52.0
Y2	0.208	0.0703	0.208	0.0703	0.2080	0.0703
k1	2.29	0.6	1.7	0.6	18	0.6
k−1	500	3.0	500	3.0	500	3.0
k2	1.761	3.50	1.207	0.95	7.00	7.00
k−2	0.09	0.09	0.09	0.09	0.09	0.09
γ	0.8	0.8	0.8	0.8	0.8	0.8
δ	0.5	0.5	0.5	0.5	0.5	0.5
K1	0.0046	0.200	0.0034	0.200	0.036	0.200
K2	19.57	38.89	13.42	10.56	77.78	77.78
Y	1.160	1.073	1.487	1.279	16.224	3.656
L′	98	145	127	173	250	493

k₁ and k₂ have units of μM⁻¹s⁻¹; K₁ and K₂, have units of μM⁻¹; equilibrium constants Y and L′, and cooperativity parameters Y₁, Y₂, γ and δ are dimensionless; all other rate constants have units of s⁻¹.