Detailed Cardiac Myofilament Experiments

Our experimental setup has been described in full detail before [3 (link), 4 (link)]. Briefly, the intraoperatively resected tissue was transported in ice-cold oxygenated cardioplegic solution, containing BDM (Sigma Aldrich Chemie GmbH, Steinheim, Germany). For the skinning procedure, the trabeculae were excised and permeabilized with Triton-X solution (Sigma Aldrich Chemie GmbH, Steinheim, Germany). The skinned myofilaments were then attached to a force transducer and a forceps and the experiments were conducted by immersing the myofilaments in twelve bowls with increasing calcium concentrations. The calcium concentration is displayed as logarithmic calcium concentration (pCa), which is a negative decadic logarithm. We started with the lowest calcium concentration at pCa 7.0 and increasing at 6.5, 6.0, 5.75, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 4.75, 4.52. Length changes, recorded by the force transducer, were recorded and stored in a database.