Fig 1.
1/8th wedge 3D-model of a half sarcomere.
Wedge-shaped sarcomere model with filaments at optimal overlap 2.3 μm length, showing location of Triad, SR, Z-disk, I-band, M-line, and A-band. Panels: a, b, and c, show how the sarcomere would appear in cross section at the three locations, illustrating how myofilament packing varies along the sarcomere: a) slice containing only actin filaments (I-band), b) slice of overlapped myosin and actin filaments (A-band), showing the myosin heads projecting off the filament backbone in pairs and c) slice near middle (M-line) of sarcomere in myosin head bare zone. Thick myosin filaments illustrated in blue, thin actin filaments illustrated in red. Virtual measurement compartments (MC-c0, MC-m0… etc) created to count changes in ion distribution, labelled on surface of compartment where they occur.
Table 1.
Fluid volume of measurement compartments.
Fig 2.
Release rates used to drive Ca2+ release, through the RYR in the model. The rate was changed every 1/10th of a ms during the simulation.
Fig 3.
[Ca2+] transient plots from our model.
The figure is a data plot for a single seed value (seed 10) used in the experiment plotted with line of best fit using a robust local regression using a weighted linear least squares (rloess) smoothing function.
Table 2.
Peak [Ca2+] within the individual MCs in the model.
Fig 4.
Calcium concentration along the sarcomere.
(a) Presents the 5 plots from MCs in the outer radial shell of the sarcomere model. (b) Presents the 5 plots from MCs in the middle radial shell of the sarcomere model. (c) Presents the 5 plots from MCs in the centre radial shell of the sarcomere model. Within the legend all results are sorted according to distance from the RYR’s to centre of each compartment.
Fig 5.
Percentage of available TnC binding sites bound with Ca2+.
(a) plots from 5 MCs in outer radial compartments. (b) plots from 5 MCs in middle radial compartments. (c) plots from 5 MCs in centre radial compartments. Within the legend all results are sorted according to distance from the RYR’s to centre of each compartment.
Fig 6.
Free Ca2+ ions are blue, ATP is yellow, ATP+Ca is green, RYRs are cyan. A single myosin filament (blue) and actin filament (red) are rendered for scale and position. Ions are depicted much larger than scale for visibility, MC-o translucent red, MC-m translucent grey, MC-c translucent green. Same renderings as S1 Video.
Fig 7.
Fenestrated SR, SERCA activation at peak [Ca2+].
SERCA pumps bound with 2 Ca2+ ions are white, SERCA bound with a single Ca2+ are orange, unbound SERCA are dark orange, RYR release sites are cyan (single myosin and actin rendered for scale).
Fig 8.
Model at peak [Ca2+] showing troponin-C binding sites.
TnC bound with 2 Ca2+ ions dark purple, TnC bound with single Ca2+ ion red, TnC unbound pink (Same renderings as used in S2 Video).
Table 3.
Proteins and MC size used within the simulation.
Table 4.
Reactions and rates used in the sarcomere simulation.