Table A1.

Model parameter interpretations and values obtained from fits to the data

Parameter Abbreviation for Interpretation Actin-FRAP Mean ± s.d. α-actinin Mean ± s.d. P-value (t-test)
κ kext/kint Crosslink ratio 0.035±0.034 0.078±0.059 0.0000014
δ Fstall/kint Contraction length 0.66±0.36 μm 0.59±0.33 μm 0.35
τ int+Fstall0)/kint Equilibration time 29±27 seconds 15±11 seconds 0.0029
τϵ γext/kint Equilibration time 0.13±0.23 seconds 0.15±0.27 seconds 0.72
  • Actin-FRAP n=86 SFs, α-actinin n=34 SFs. κ denotes the dimensionless ratio of stiffness of the crosslinks over stiffness of the SF. δ is the contraction length in μm of a sarcomeric unit. τ is the time scale in seconds associated with effective internal friction including motor contributions, whereas τϵ is the time scale associated with external friction. We provide the mean and s.d. for each model parameter. To compare the parameter distributions for the actin-FRAP and the α-actinin data we applied a Student's t-test analysis. The crosslink parameter κ results significantly higher and the time scale τ significantly lower for the α-actinin-transfected cells. The remaining parameters are independent of the transfection method. Furthermore, we find that τϵ<<τ