FIGURE 6.

Fluorescence lifetime change following transition from relaxation to rigor. A, difference between the mean fluorescence lifetimes of ELC in relaxation and rigor. All ELC label positions have a longer fluorescence lifetime in rigor. n = 13, 14, 14 and 16, p < 0.05 in each case. B, the effect of partial thick and thin filament overlap on the fluorescence lifetime profile of A-bands in relaxed and rigor fibers. The relaxed fiber was stretched to 2.6 μm and then moved to rigor. Shown are the half-sarcomere fluorescence intensity (black) and fluorescence lifetime profiles in relaxed (green) and rigor (red) fibers. Two populations of fluorescence lifetime are observed in rigor at the center and periphery of the A-band, which can be attributed to the presence of unattached and attached cross-bridges, respectively. arb., arbitrary units.