Fluorescence polarization signals (Q|| and Q^), sarcomere length (S.L. measured using white light diffraction) and tension (T) during staircase length changes. The fiber is actively contracting at 5 mM MgATP and ~30 uM free Ca2+. Panel (a) shows 9 successive releases applied every 50 ms. Panel (b) is a faster time base display of the average of 40 steps from 5 separate contractions. Both Q signals change instantly at the length step. Q^ continues to deflect during quick tension recovery. These data show that the regulatory light chain tilts during elastic distortion of the myosin head and during the force-generating transition.
Irving et al., Nature 1995