Fig. 3. ATP step experiments starting at high force rigor. A stepwise increase of ATP concentration was induced by flash photolysis of caged ATP. (A) Force recording at low time resolution, indicating the conditions for induction of high-force rigor and subsequent force decay induced by an ATP step. (B) Superimposed force recordings at high time resolution of ATP step under control (pH 6.7) and test conditions (pH 7.4).