Fig. 4.

Effects of dATP on lattice geometry and myofilament structure in resting cardiac muscle (pCa 9.0). At physiological ionic strength (μ = 170 mM), dATP (blue bars) significantly increases the lattice spacing (A, d_1,0), the intensity ratio of the primary equatorial reflections (B, I_1,1/I_1,0), and the spacing of the M3 reflection (C, S_M3) at both short and long SLs compared with ATP (white bars), but does not affect the intensity of the M3 reflection (D, I_M3) at either SL. However, at low ionic strength (μ = 100 mM), these effects are diminished at both short and long SLs (E–G) and the I_M3 remains unaffected by dATP (H). Error bars represent SEM for n ≥ 14 preparations. *P < 0.05. a.u., arbitrary units; NS, not significant. (Numerical values are reported in SI Appendix, Table S1.)