Table 1. MUSICO parameters for the... | Rockefeller University Press

Table 1.

MUSICO parameters for the simulations of twitch contractions in intact rat trabeculae at fixed length and at temperature 27.2°C in Fig. 5 (Caremani et al., 2016) and at 27.5°C in Fig. 6 (Janssen et al., 2002)

Description	Parameter	Isometric trabeculae	Notes
Cross-bridge cycle
Myosin–actin binding rate	$k_{+ A}^{o}$	226 s⁻¹
Myosin–actin detachment rate^a	$k_{- A}^{o}$	46 s⁻¹
Myosin stroke cap rate	$k_{+ P i}^{c a p}$	1,000 s⁻¹	Mijailovich et al., 2016, 2019
Myosin reverse stroke cap rate	$k_{- P i}^{c a p}$	100 s⁻¹	Mijailovich et al., 2016, 2019
Power stroke Gibbs energy change	$Δ G_{s t r o k e}$	−13 $k_{B} T$	Mijailovich et al., 2016, 2019
Working stroke	$d$	10.5 nm	Duke, 1999; Mijailovich et al., 2016, 2019
Second working stroke	$δ$	1 nm	Mijailovich et al., 2016, 2019
ADP release rate^a	$k_{+ D}^{o}$	60 s⁻¹
ATP binding and myosin detachment^a	$k_{+ T}$	10⁶ s⁻¹
Hydrolysis forward rate^a	$k_{+ H}$	100 s⁻¹
Hydrolysis backward rate^a	$k_{- H}$	10 s⁻¹
Cross-bridge stiffness	$κ$	1.3 pN/nm	Duke, 1999; Mijailovich et al., 2016, 2019
$k_{B} T$ at 27.5°C	$k_{B} T$	4.147 pN·nm
Calcium kinetics
Calcium binding to TnC equilibrium rate	${\tilde{K}}_{C a}$	1 µM⁻¹	Smith and Geeves, 2003; Geeves et al., 2011
Calcium binding rate to TnC	${\tilde{k}}_{C a}$	75.4 µM⁻¹·s⁻¹	Smith and Geeves, 2003; Geeves et al., 2011
Calcium dissociation rate from TnC	$k_{- C a}$	75.4 s⁻¹	Kreutziger et al., 2011; Wang et al., 2012, 2013
TnI–actin equilibrium rate constant At high Ca²⁺	$λ$	10
TnI–actin backward rate constant	$λ_{-}$	375 s⁻¹
Allosteric TnC–TnI–actin–Ca²⁺ parameter	$ε_{o}$	0.01	Smith and Geeves, 2003; Geeves et al., 2011
CFC
Tpm pinning angle	$ϕ_{-}$	−25°	Poole et al., 2006
Myosin Tm angular displacements	$ϕ_{+}$	10°	Poole et al., 2006
Angular SD of free CFC	$σ_{0}$	29.7°	Pirani et al., 2005; Mijailovich et al., 2012
Persistence length of Tm–Tn confined chain	$1 /ξ$	50 nm	Mijailovich et al., 2012
PS
Transition rate to PS	$k_{- P S}$	200 s⁻¹	Assumed
Baseline rate	$k_{P S}^{0}$	5 s⁻¹	Assumed
Amplitude	$k_{P S}^{m a x}$	400 s⁻¹	Assumed
Calcium Hill function slope	$b$	5	Assumed
Half-activation point of the Hill function	${[C a^{2 +}]}_{50}$	1 µM	Assumed
Sarcomere
Length of sarcomere	$S L$	2.2 µm
Length of actin filament	$L_{a}$	1.1 µm	Robinson and Winegrad, 1977, 1979
Interfilament spacing	$d_{10}$	33.83 nm	Irving and Maughan, 2000
Thin-filament elastic modulus	$A E_{a}$	65 nN	Huxley et al., 1994; Kojima et al., 1994
Thick-filament elastic modulus	$A E_{m}$	132 nN	Huxley et al. 1994

Description	Parameter	Isometric trabeculae	Notes
Cross-bridge cycle
Myosin–actin binding rate	$k_{+ A}^{o}$	226 s⁻¹
Myosin–actin detachment rate^a	$k_{- A}^{o}$	46 s⁻¹
Myosin stroke cap rate	$k_{+ P i}^{c a p}$	1,000 s⁻¹	Mijailovich et al., 2016, 2019
Myosin reverse stroke cap rate	$k_{- P i}^{c a p}$	100 s⁻¹	Mijailovich et al., 2016, 2019
Power stroke Gibbs energy change	$Δ G_{s t r o k e}$	−13 $k_{B} T$	Mijailovich et al., 2016, 2019
Working stroke	$d$	10.5 nm	Duke, 1999; Mijailovich et al., 2016, 2019
Second working stroke	$δ$	1 nm	Mijailovich et al., 2016, 2019
ADP release rate^a	$k_{+ D}^{o}$	60 s⁻¹
ATP binding and myosin detachment^a	$k_{+ T}$	10⁶ s⁻¹
Hydrolysis forward rate^a	$k_{+ H}$	100 s⁻¹
Hydrolysis backward rate^a	$k_{- H}$	10 s⁻¹
Cross-bridge stiffness	$κ$	1.3 pN/nm	Duke, 1999; Mijailovich et al., 2016, 2019
$k_{B} T$ at 27.5°C	$k_{B} T$	4.147 pN·nm
Calcium kinetics
Calcium binding to TnC equilibrium rate	${\tilde{K}}_{C a}$	1 µM⁻¹	Smith and Geeves, 2003; Geeves et al., 2011
Calcium binding rate to TnC	${\tilde{k}}_{C a}$	75.4 µM⁻¹·s⁻¹	Smith and Geeves, 2003; Geeves et al., 2011
Calcium dissociation rate from TnC	$k_{- C a}$	75.4 s⁻¹	Kreutziger et al., 2011; Wang et al., 2012, 2013
TnI–actin equilibrium rate constant At high Ca²⁺	$λ$	10
TnI–actin backward rate constant	$λ_{-}$	375 s⁻¹
Allosteric TnC–TnI–actin–Ca²⁺ parameter	$ε_{o}$	0.01	Smith and Geeves, 2003; Geeves et al., 2011
CFC
Tpm pinning angle	$ϕ_{-}$	−25°	Poole et al., 2006
Myosin Tm angular displacements	$ϕ_{+}$	10°	Poole et al., 2006
Angular SD of free CFC	$σ_{0}$	29.7°	Pirani et al., 2005; Mijailovich et al., 2012
Persistence length of Tm–Tn confined chain	$1 /ξ$	50 nm	Mijailovich et al., 2012
PS
Transition rate to PS	$k_{- P S}$	200 s⁻¹	Assumed
Baseline rate	$k_{P S}^{0}$	5 s⁻¹	Assumed
Amplitude	$k_{P S}^{m a x}$	400 s⁻¹	Assumed
Calcium Hill function slope	$b$	5	Assumed
Half-activation point of the Hill function	${[C a^{2 +}]}_{50}$	1 µM	Assumed
Sarcomere
Length of sarcomere	$S L$	2.2 µm
Length of actin filament	$L_{a}$	1.1 µm	Robinson and Winegrad, 1977, 1979
Interfilament spacing	$d_{10}$	33.83 nm	Irving and Maughan, 2000
Thin-filament elastic modulus	$A E_{a}$	65 nN	Huxley et al., 1994; Kojima et al., 1994
Thick-filament elastic modulus	$A E_{m}$	132 nN	Huxley et al. 1994

Based on mouse and human α myosin values in (Deacon et al., 2012a, 2012b) with corrections for temperature; ionic strength is as documented in (Mijailovich et al., 2017).

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