Figure 7.

Scatter plots for single emission-dipole and lever-arm orientation coordinates, (β′,α′) or (β,α), respectively, from skeletal (A and B) and cardiac muscle (C) in relaxation. Blue and red symbols represent p-polarized (e_p) and s-polarized (e_s) photoactivating light polarization. Open squares (lever-arm) are calculated from the emission dipole moments of photoactivated probes with orientation coordinates (β′,α′) (open triangles). The fitted points (solid blue and red squares (μ_emfit)) were derived from structures 725 (skeletal) and 506 (cardiac) in Fig. 6. (D) Stacked histogram for the absorption dipole coordinate, γ′, defined in Eq. 12d. The histogram specifies one of the Euler angles relating the emission molecular frame ({u,v,w} in Fig. S1) to the lab frame ({L_x′,L_y′,L_z′} in Fig. 2). The narrow-profile histogram indicates that PAGFP is rigidly immobilized on the cross bridge in both skeletal and cardiac muscle. The skeletal histogram has events from both p- and s-polarization (blue and red, respectively) photoactivated dipoles. The cardiac histogram has just the p-polarization photoactivated dipoles (green).