Table B.1.
List of parameters estimated/used for the myofilament model
| Parameter | Description | Value | Reference |
|---|---|---|---|
| Thick-thin filament activation parameters | |||
| Lthick | Length of thick filament | 1.67 μm | Gordon et al.[27] |
| Lthin | Length of thin filament | 1.2 μm | Rice et al.[26] |
| Lbare | Length of bare region of thick filament | 0.1 μm | Rice et al.[26] |
| kon | Association rate of Ca2+ with TrpC | 100 μM | Niederer et al. |
| koffL | Dissociation rate of Ca2+ from low affinity TrpC | 4218.5 sec−1 | Fit to Janssen data[19] |
| koffH | Dissociation rate of Ca2+ from high affinity TrpC | 156.5 sec−1 | Fit to Janssen data[19] |
| ζ | Force sensitivity of Ca2+ unbinding rate | 0.23 | Fit to Janssen data[19] |
| β50 | TrpReg value which the effect is half-maximal | 0.5 | Rice et al.[26] |
| nβ | Hill-coefficient of the TrpReg effect | 15 | Rice et al.[26] |
| Qkon | Temperature dependence of kon | 1.5 | Rice et al.[26] |
| Qkoff | Temperature dependence of koff | 1.3 | Rice et al.[26] |
| Cross-bridge cycling parameters | |||
| knp | Transition rate from N to P | 329.2 sec−1 | Fit to Janssen data[19] |
| kpn | Transition rate from P to N | 50 sec−1 | Rice et al.[26] |
| ka | Myosin-actin rate of attachment | 294.1 sec−1 | Tewari et al.[15] |
| kd | Myosin-actin rate of detachment | 88.9 sec−1 | See footnote† |
| k1 | Transition rate from A1 T to A2 T | 10.2 sec−1 | Tewari et al.[15] |
| k−1 | Transition rate from A2 T to A1 T | 10.3 sec−1 | Tewari et al.[15] |
| K2 | Transition rate from A2 T to A3 T | 88.6 sec−1 | Tewari et al.[15] |
| k−2 | Transition rate from A3 T to A2 T | 20.9 sec−1 | See footnote‡ |
| k3 | Transition rate from A3 to P | 35.6 sec−1 | Tewari et al.[15] |
| α1 | Stretch sensing parameter for k1 and k−1 | 10 μm−1 | Tewari et al.[15] |
| α2 | Stretch sensing parameter for k2 and k−2 | 9 μm−1 | Tewari et al.[15] |
| α3 | Stretch sensing parameter for k3 | 59.3 μm−1 | Tewari et al.[15] |
| s3 | Strain at which k3 is minimum | 9.9 nm | Tewari et al.[15] |
| kstiff,1 | Stiffness of frictional forces arising due to myosin-actin interaction | 2827.1 kPa μm−1 | Tewari et al.[15] |
| kstiff,2 | Stiffness of forces arising due to cross-bridge powerstroke | 51871 kPa μm−1 | Tewari et al.[15] |
| QkNtoP | Temperature dependence of kNtoP | 1.6 | Rice et al.[26] |
| QkPtoN | Temperature dependence of kPtoN | 1.6 | Rice et al.[26] |
| QXB,1 | Temperature dependence of ka, k1 | 3.82 | Fit to data[19] |
| QXB,2 | Temperature dependence of kd, k−1 | 2.39 | Fit to data[19] |
| QXB,3 | Temperature dependence of k2, k3 | 6.73 | Fit to data[19] |
| QXB,4 | Temperature dependence of kstiff,1 | 1.34 | Tewari et al.[15] |
| QXB,5 | Temperature dependence of kstiff,2 | 1.44 | Tewari et al.[15] |
| Other parameters | |||
| λXB | Factor scaling cross-bridge force | 1.31 | Fit to CVS data[25]; See Footnote‖ |
| KSE | Stiffness of series element | 1000 kPa μm−1 | See text |
| η | Viscosity coefficient of cardiac muscle | 1 kPa sec μm−1 | Fixed |
†
Scaled by a factor of 2.5 from original published value to make kd/ka same as mouse XB mouse [15]. Note, that experimental data with variable Pi was only available for mouse myocardial strips (see Tewari et al. [15]).
‡
Scaled by a factor of 10 from original published value to make k−2 of same magnitude as k2. Note, no experimental data was available with variable ADP and model was relatively insensitive to this parameter (see Tewari et al. [15]).
‖
Scaling factor used to consolidate differences between myofilament force generation in vivo and in vitro. It was used only while simulating the CVS model.