Figure 2. Tension responses to the photolytic release of 1.1 mM ATP from 10 mM DMB-caged ATP (1 and 2) or 0.33 mM ATP from 2 mM DMB-caged ATP (3) in a single frog muscle fibre slightly cross-linked with EDC in the absence (1) and presence (2 and 3) of Ca²⁺.

The time of the laser flash is visible as an artefact on the tension records. The dashed vertical lines indicate the points at which the time scale was changed, so that the fast initial changes and the slow later changes could be clearly seen on a single graph. Fibre dimensions: 3.43 mm × 19 600 μm²; sarcomere length measured in relaxing solution, 2.1 μm.